CN102808429B - Pile foundation soaking load test method based on creep-strain separation - Google Patents

Abstract

The invention discloses a pile foundation soaking load test method based on creep-strain separation, which comprises the steps as follows: firstly, a constant load is loaded; secondly, strain values of a pile body and internal force of the pile body before the soaking are tested, that is, when the settlement of a test pile is stabilized, the strain values in different depth positions of the pile body of the test pile are tested and the internal force in different depth positions of the pile body of the test pile before the soaking are analyzed; thirdly, the soaking is conducted and the strain values of the pile body during the soaking are tested, that is, when the settlement of the test pile is stabilized, the test pile is soaked, and after the test pile is soaked, the strain values in different depth positions of the pile body of the test pile are tested at regular intervals of Delta t; fourthly, an actually measured creep degree function of a calibration section is obtained; fifthly, the creep degree function during each loading age is obtained; and sixthly, the strain values of the pile body and the internal force of the pile body are calculated after creep separation during the soaking. The method disclosed by the invention has the advantages that the steps are simple, the testing is convenient, creep and strain can be separated from a pile body strain test result simply, conveniently, rapidly and accurately, so that the test result approximates to the practical stress state of the pile body as much as possible.

Description

Pile foundation ponding loading test method based on creep strain separation

Technical field

The present invention relates to a kind of pile foundation ponding loading test method, especially relate to a kind of pile foundation ponding loading test method based on creep strain separation.

Background technology

Early eighties, Swiss Confederation's Zurich University of Science and Technology rock and construction of tunnel are that professor K.Kovari etc. has proposed collimation method monitoring principle (Linewise observation), are different from the pointwise observation principle (Pointwise Observation) of counting representative with strain; And developed a series of portable instrument (comprising slip micrometer) according to collimation method monitoring principle, to be different from the fixedly embedded type instrument such as strain meter, multiple spot extensometer, oneself declares this quasi-instrument patent and entrusts the production and sales of Switzerland Solexperts AG company.

Slip micrometer is that it can 1m be the strain that gauge length is measured line direction continuously according to a kind of portable high-accuracy strain testing instrument of collimation method monitoring principle development, and then calculates the Stress and displacement of each point.This series instrument is by Switzerland's research and production, the later stage eighties 20th century is introduced China, in the monitoring of the engineering site such as pile foundation, deep foundation ditch, tunnel, side slope, dam, obtained successful Application at home, tester similar with other compared, and can obtain higher measuring accuracy.Transportable test panel instrument is counted in slip micrometer, it measures the mean strain of adjacent point-to-point transmission serially, so just can derive the displacement of axial strain distribution and arbitrfary point on whole piece survey line, a set of instrument can be used for a plurality of boring and a plurality of engineering, is specially adapted to the on-the-spot strain of geotechnical engineering (distortion) monitoring.During actual test, slip micrometer can move freely and measure continuously relative deformation, the strain that resolution ratio is 0.001mm/m and the deformation test instrument between adjacent 2 points (spacing is 1000mm) along survey line in measured medium.

Slip micrometer is mainly comprised of test probe, test tube (English name is Measuring pipe), data collecting instrument, guide rod (also claiming measuring staff) etc., and wherein test tube is comprised of plastic bushing (English name is Casing) and mark (English name is Measuring Mark).Wherein, the mark measurement sign that conical ring that the materials such as hard metal or duroplasts make and shell form of serving as reasons; Test probe adopts ball cone positioning principle to measure the mark in test tube, and sensor accuracy is very high, before and after each measurement, carries out periodic calibration, can arrive very high certainty of measurement and long-time stability.During actual test, on plasticity sleeve pipe, a mark is laid at every meter of interval, and survey line is divided into some sections, by grouting, together with mark is cast in securely with measured medium, when measured medium deforms, will drive mark deform in same pace with it.Thereby with slip micrometer, measure piecemeal each gauge length over time, thereby obtain reflecting that measured medium is along the distortion regularity of distribution of survey line.

Collapsible loess is a kind of special soils, extensively be distributed in northern China, it can sink under the effect of power and water, and wherein self weight collapse loess will be sunk by water soaking under the effect of upper earthing gravity pressure, thereby causes the stake in self weight collapse loess to produce negative friction effect.In Collapsible Loess District, concrete pile is main pile foundation type.Be arranged in the pile foundation of Site of Collapsible Loess, when settlement by soaking soil layer immersion deflection is greater than pile foundation deflection, saturated yielding soil layer produces relatively to pile foundation, and all certain thickness settlement by soaking soil bodys of stake are suspended on pile body by frictional force, and test pile is produced to negative friction effect.While adopting pile foundation to use as the basis of important engineering on Site of Collapsible Loess, negative friction working trait for research Collapsible Loess District pile foundation, and the parameter such as required negative friction size and Depth of Neutral during the design of definite pile foundation engineering, often carry out the on-the-spot submerging test of Site of Collapsible Loess pile foundation, actual measurement pile foundation negative friction force and other correlation technique parameters are carried out Pile Foundations Design.

Before the eighties in 20th century, adopt suspension method to carry out the experimental study of Loess Site pile foundation negative friction force more.Development along with measuring technology, after the nineties in 20th century, many employings are buried sensor underground and by internal force, are tested to carry out the test of negative friction in pile body, common way is in loess immersion process, maintaining test pile stake, to push up constant load (comprise zero load) constant, in pile body, bury sensor test loess underground the situation of additional sinking process pile concrete strain occurs in immersion, by elastic theory formula (1) calculate the axle power of the different test of pile body section, and then obtain pile side resistance (containing negative friction size and Depth of Neutral).Q in formula (1) _ifor the Zhou Liqieqi unit of pile body i section part is kN, for the strain mean of pile body i section part, E _ifor pile shaft material modulus of elasticity, Qie Qiwei unit is kPa, A _ifor pile body section area, Qie Qi unit is m ².

Yet in employing, bury underground in the pile foundation submerging test that sensor carries out, required time (starting to sedimentation basicly stable from immersion) of collapsible loess immersion settlement stability is longer, and test generally needs to continue January～March.In this process, test pile pile body concrete under the effect of axle power except occurring elastic strain, also can creep, therefore, in test pile ambient conditions (temperature and humidity), remain unchanged under condition, be embedded in the strain that the sensor test in pile body obtains and in fact comprised elastic strain and the two parts of creeping.In the middle of test data housekeeping in the past, often ignore the impact of creeping, the strain substitution formula (1) directly test being obtained is calculated pile body axle power, when place, stake top reference axis power and stake top load application are inconsistent, generally by be less than 1 fixedly correction factor (making in formula (1) both sides, place, stake top equal) in formula (1) right side increase by, the axle power of pile body is revised.

To sum up, because pile foundation ponding loading test need to carry out the long period, under action of long-term load, concrete is except occurring elastic strain, also can creep, but in test job in the past, ignore the impact of creeping, will survey strain substitution elastic theory design formulas and calculate pile body axle power, pile body the strength of the axle is calculated result certainly will have larger error.In fact, need to be in strain testing result separated concrete elastic strain and creeping, after the value of creeping in deduction actual measurement strain, then calculate and just can make pile body axial force test result be tending towards reality by elastic theory.

Summary of the invention

Technical problem to be solved by this invention is for above-mentioned deficiency of the prior art, a kind of pile foundation ponding loading test method based on creep strain separation is provided, simple and the convenient test of its method step, can be easy from pile strain test result, separated creep strain fast and accurately, make test result approach as far as possible the actual stress state of pile body.

For solving the problems of the technologies described above, the technical solution used in the present invention is: a kind of pile foundation ponding loading test method based on creep strain separation, is characterized in that the method comprises the following steps:

Step 1, constant load load: from top to bottom the test pile of having constructed is loaded, and the load loading on test pile stake top is F _n; The stress applying on described test pile stake top , the dowel section area that in formula, A is test pile;

Described test pile is vertical to the concrete pile being laid in collapsible loess stratum, and test pile leaves pile crown more than ground;

Pile strain value and Internal forces test before step 2, immersion: during stake settlement stability to be tested, adopt slip micrometer to test the strain value at test pile pile body different depth place, and process according to test result analysis pile body axle power and the pile side resistance that draws the front test pile pile body different depth of immersion place;

Before test pile being loaded in step 1, first in test pile, lay the test tube of described slip micrometer, described test tube is vertically to being laid in the pile body of test pile; Described test tube is comprised of plasticity sleeve pipe and a plurality of mark being arranged on from the bottom to top on described plasticity sleeve pipe of the equal opening in upper and lower two ends; In a plurality of described marks, the mark mutually concordant with ground is mark one; In a plurality of described marks, be positioned at described mark one top and the mark adjacent with described mark one is top mark, described top mark is positioned at demarcates section, and the distance of described top mark between pushing up with test pile stake is greater than the external diameter of test pile; The sections of described test pile between described top mark and described mark one is for demarcating section;

Step 3, immersion and pile strain value test between soaking period: during stake settlement stability to be tested, test pile is soaked, now to maintain the load time be τ to the pile top load of test pile ₀; After immersion, per interval Δ t, adopts described slip micrometer once to test the strain value at test pile pile body different depth place; Wherein, Δ t=24 hour ± 5 hours; And after m test, the actual measurement strain value at the test pile pile body different depth place in m the different test moment between corresponding acquisition soaking period;

Wherein, between soaking period, m different tests are respectively t constantly from front to back ₁, t ₂, t ₃t _m, the time interval between adjacent two tests constantly in front and back is Δ t, and pile top load maintains load time τ ₀be positioned at test t constantly ₁the time interval before and between the two is Δ t;

Between soaking period, the stress applying on described test pile stake top remains unchanged;

Step 4, a demarcation section actual measurement creep degree function obtain, and its acquisition process is as follows:

Step 401, the strain of demarcating section between soaking period calculatings of creeping: according to the test result in step 2 and step 3, by the strain value of m between soaking period different tests demarcation section constantly, after the strain value of all demarcating before deduction immersion section, acquisition stress the strain of lower m the different tests of effect demarcation section is constantly crept;

The strain of demarcating section under step 402, the unitstress effect calculating of creeping: by stress in step 401 the strains of lower m the difference test of effect demarcation section are constantly crept, and the strain that is converted to the demarcation section in m the different test moment under unitstress effect is crept;

Step 403, a demarcation section creep degree Function Fitting: according to the strains of the demarcation section in m the different test moment under the unitstress effect obtaining in step 402, creep, adopt polynomial fitting method, simulate the creep degree function C (t, the τ that between soaking period, demarcate section ₀), and described creep degree function C (t, τ ₀) be that test pile is τ in load age ₀time creep degree function;

The creep degree function of step 5, arbitrary load age obtains: according to the creep degree function C (t, the τ that simulate in step 403 ₀), and adopt aging mechanism, nativistic theory or aging and congenital binding isotherm, extrapolate described test pile at arbitrary load age τ _itime creep degree function C (t, τ _i), i=1,2,3 wherein ... m;

When adopting aging mechanism to calculate, C (t, τ _i)=C (t, τ ₀)-C (τ _i, τ ₀);

When adopting nativistic theory to calculate, C (t, τ _i)=C (t-τ _i+ τ ₀, τ ₀);

When adopting aging and congenital binding isotherm to calculate,

$C(t,{\mathrm{\τ}}_i)=\frac{C(t,{\mathrm{\τ}}_0)-C({\mathrm{\τ}}_i,t_0)+C(t-{\mathrm{\τ}}_i+{\mathrm{\τ}}_0,{\mathrm{\τ}}_0)}{2};$

Step 6, the separated rear pile strain value of creeping between soaking period and Internal forces are calculated: the actual measurement strain value at the test pile pile body different depth place in m the different test moment between the soaking period that test in step 3 is drawn, all eliminate after creep of concrete, obtain between soaking period the separated rear strain value of creeping at m different tests test pile pile body different depth place constantly; Meanwhile, corresponding extrapolating eliminated test pile pile body different depth after creep of concrete and is between soaking period m different tests axle power and the separated rear pile-side negative friction of creeping constantly;

For the arbitrary depth z of test pile pile body, be in any test t constantly _nactual measurement strain value ε _n ^*(z) while eliminating creep of concrete,

According to formula ${\mathrm{\ϵ}}_n\left(z\right)=\frac{P_n\left(z\right)}{\mathrm{EA}}={{\mathrm{\ϵ}}_n}^{*}\left(z\right)-\frac{P_0\left(z\right)}{A}C(t_n,{\mathrm{\τ}}_0)-\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\frac{{\mathrm{\ΔP}}_i\left(z\right)}{A}C(t_n,{\mathrm{\τ}}_i),$ Calculate the arbitrary depth z of test pile pile body and be in any test t constantly _ncreep separated after strain value, wherein n is natural number and n≤m; In formula, ε _n(z) for test pile pile body depth z after eliminating creep of concrete is in test t constantly _ncreep separated after strain value, ε _n ^*(z) the test pile pile body depth z drawing for test in step 3 is in test t constantly _nactual measurement strain value, P _n(z) for test pile pile body depth z after eliminating creep of concrete is in test t constantly _npile body axle power, and

${\mathrm{\ΔP}}_n\left(z\right)=\frac{1}{1+\mathrm{EC}(t_n,{\mathrm{\τ}}_n)}\left\{E\right[{{\mathrm{A\ϵ}}_n}^{*}\left(z\right)-P_0\left(z\right)C(t_n,{\mathrm{\τ}}_0)-\underset{i=1}{\overset{n-1}{\mathrm{\Σ}}}{\mathrm{\ΔP}}_i\left(z\right)C(t_n,{\mathrm{\τ}}_i)]-P_0\left(z\right)-\underset{i=1}{\overset{n-1}{\mathrm{\Σ}}}{\mathrm{\ΔP}}_i\},$

P ₀(z) the pile body axle power before soaking in the test pile pile body depth z place drawing for analyzing and processing in step 2, the dowel section area that A is test pile, the pile concrete modulus of elasticity that E is test pile, C (t _n, τ ₀) be the C of creep degree function described in step 4 (t, τ ₀) at test moment t _ntime functional value, C (t _n, τ _i) be the C of creep degree function described in step 5 (t, τ _i) at test moment t _ntime functional value, C (t _n, τ _n) be creep degree function C (t, τ _n) at test moment t _ntime functional value;

After extrapolating elimination creep of concrete, test pile pile body depth z is in test t constantly _naxle power after, also need according to formula after calculating elimination creep of concrete, test pile pile body depth z is in test t constantly _npile-side negative friction.

The above-mentioned pile foundation ponding loading test method based on creep strain separation, it is characterized in that: the test pile described in step 1 is cylindrical stake, and what pile foundation ponding loading test of all side excavation formation of test pile was used tests pits, described testing pits as flat hole, and mutually concordant at the bottom of the hole in described mark one and described flat hole; A described demarcation section arranged outside has a tank, and described tank is that cylindrical tank and its are coaxial laying with test pile;

When test pile is soaked in step 3, adopt pumping system to continue to water filling in tank, institute injects underground water and fills with after tank, overflows inflow test pits and freely descend maceration to steep the residing collapsible loess of test pile stratum from tank;

Described pumping system comprises draws water pipeline and underground water is delivered to the pumping equipment in tank by the pipeline that draws water, described in draw water rear end and the pumping equipment of pipeline join, and the front end of the pipeline that draws water extends the bottom land of tank from top to bottom; The height of described tank is not less than the height of described top mark.

The above-mentioned pile foundation ponding loading test method based on creep strain separation, is characterized in that: the quantity of test tube described in step 2 is one or more;

When the quantity of described test tube is many, the structure of many described test tubes and size are all identical, and many described test tubes are along the circumferential direction evenly laid in test pile;

While adopting described slip micrometer to test the strain value at test pile pile body different depth place in step 2, the strain value at test pile pile body different depth place before the many groups of immersions that corresponding acquisition is drawn by many described test tube tests respectively, after afterwards the strain value at test pile pile body different depth place before many groups of immersions being averaged, obtain the mean strain value at the front test pile pile body different depth of immersion place; Subsequently, according to the mean strain value at test pile pile body different depth place before obtained immersion, extrapolate pile body axle power and the pile side resistance at the front test pile pile body different depth of immersion place;

In step 3, after m test, corresponding acquisition tests by many described test tubes the many groups test data drawing respectively, and each organizes the actual measurement strain value that described test data includes the test pile pile body different depth place in m the different test moment between soaking period;

M the different strain value of testing demarcation section constantly between soaking period in step 401, correspondence is respectively the mean strain value that many described test tubes are tested the demarcation section in m the different test moment between the soaking period drawing;

ε described in step 6 _n ^*(z) the test pile pile body depth z, drawing for many described test tube tests is in test t constantly _naverage actual measurement strain value.

The above-mentioned pile foundation ponding loading test method based on creep strain separation, it is characterized in that: the bottom of described tank is provided with a plurality of water seepage holes, a plurality of described water seepage holes are along the circumferential direction evenly laid in the surrounding outside of test pile, and a plurality of described water seepage hole is all vertically to laying.

The above-mentioned pile foundation ponding loading test method based on creep strain separation, is characterized in that: when test pile is loaded in step 1, adopt device for measuring force to the described load F being applied on test pile stake top from top to bottom _ndetect in real time, and by testing result synchronous driving to data processor;

While adopting described slip micrometer to test the strain value at test pile pile body different depth place in step 2, the data collecting instrument of described slip micrometer by test result synchronous driving to data processor, described data processor carries out analyzing and processing to test result, and corresponding pile body axle power and the pile side friction that draws the front test pile pile body different depth of immersion place; And the data collecting instrument of the micrometer that slides described in step 3, the test pile pile body different depth that test is drawn is in the actual measurement strain value synchronous driving in m the different test moment between soaking period to described data processor, described data processor carries out analyzing and processing according to step 4 to the method described in step 6 again, and respective handling show that eliminating test pile pile body different depth after creep of concrete is between soaking period m different tests creep separated rear strain value, pile body axle power and pile-side negative friction constantly.

The above-mentioned pile foundation ponding loading test method based on creep strain separation, it is characterized in that: in step 6, also need to be in the axle power in m the different test moment between soaking period and the separated rear pile-side negative friction of creeping according to test pile pile body different depth after the elimination creep of concrete of extrapolating, extrapolate the Depth of Neutral of test pile between soaking period.

The above-mentioned pile foundation ponding loading test method based on creep strain separation, it is characterized in that: the test pile described in step 1 is bored pile, and after the stake hole forming of described bored pile, first described test tube is arranged in described stake hole, more described bored pile is carried out to filling concrete construction.

The above-mentioned pile foundation ponding loading test method based on creep strain separation, is characterized in that: when test pile is loaded in step 1, adopt charger to load from top to bottom; Described charger comprises two at the anchoring pile of the test pile left and right sides and is erected on two loading equipemtns between described anchoring pile, described loading equipemtn be positioned at test pile directly over.

The above-mentioned pile foundation ponding loading test method based on creep strain separation, is characterized in that: the test pile described in step 1 is pile for prestressed pipe; After described prestressing pipe pile construction completes, then in the described pile for prestressed pipe completing in construction, test tube is installed, and described test tube is vertically to the pipe pile core middle part that is laid in described pile for prestressed pipe; Described top mark is in a plurality of described marks, to be positioned at the mark of topmost;

After described test tube installation, adopt again grouting equipment in the pipe pile core of described pile for prestressed pipe and the cavity between test tube, to inject packing material from the bottom to top, the mixed serum of described packing material for being uniformly mixed to form according to the ratio of weight ratio 1000 ︰ 600～1200 ︰ 75 by water, cement and swell soil.

The above-mentioned pile foundation ponding loading test method based on creep strain separation, is characterized in that: in step 1, a plurality of described marks are even laying, and the spacing between neighbouring two described marks is 1m; Δ t=24 hour in step 3.

The present invention compared with prior art has the following advantages:

1, method step is simple, reasonable in design and realize conveniently, and input cost is low.

2, according to the pile body the strength of the axle is calculated method after the theoretical elimination Creep Effect of deriving of Linear Creep, expression formula is simple, and when the Internal Force Monitoring time interval is little, the Internal forces under can each monitoring time of step-by-step calculation.

3, by constant pile top load, near stake top, unsettled demarcations section is set, can obtain a creep degree fundamental curve, by the derive creep degree curve of arbitrary load age of nativistic theory and aging mechanism, can obtain an interval value that comprises collateral resistance true value accordingly.

4, for making the creep degree curve of acquisition representative, should control the strength grade of pile concrete, its compressive strength should be greater than 2.5 times of neutral point place stress, makes test result more accurate.

5, adopt the submerging test to loess pile foundation can utilize the principle that underground water temperature is comparatively constant to control the temperature and humidity of demarcating section concrete, make the ambient conditions of itself and bottom pile body basic identical.While specifically adopting underground water as immersion water source, and around demarcating section, a tank is set, allows underground water enter tank from bottom, top overflow entering immersion test pits, with play demarcate section temperature substantially constant and with the essentially identical object of bottom pile body temperature, it is convenient to realize, input cost is low.Simultaneously, also there is the problem similar with temperature in the humidity of demarcating section, if water seepage hole is set in tank, can make the concrete humidity of upper and lower pile body (one of curing condition) reach rapidly basic identical, make to demarcate section creep degree function recording more representative.

6, when test pile is pile for prestressed pipe, test tube mounting method step is simple, easy and simple to handle and input cost is low, test tube installation steps are reasonable in design and workable, while test tube installation rate is fast and test tube installation quality is high, efficiently solve the technical barrier that test tube is installed in pile for prestressed pipe, guaranteed that test tube is positioned at the test position of pile for prestressed pipe, thereby can survey, accurately recorded pile lining strain.And when test pile is pile for prestressed pipe, the packing material component that adopts is reasonable in design and result of use good, by Backup Materials between pile for prestressed pipe and test tube, make pile lining strain pass to test tube by packing material, by test test tube strain energy, accurately reflect the strain value of pile lining under the effect of load.

7, method step is reasonable in design and realize conveniently, by strain testing is installed in test pile, by test tube, monitors pile strain, arranges and demarcate section more than ground; While carrying out internal force test, demarcate section and be soaked among the metastable underground water of temperature with the pile body that buries simultaneously, the temperature and humidity that maintenance test pile is demarcated section concrete is constant and consistent with bottom pile body, and the strength grade of concrete of Control experiment stake; According to demarcating section pile top load value and each strain testing result, obtain test pile and demarcate the relation of stress, strain and the monitoring time of section, set up representative creep degree function curve, specifically by the elastic strain value of measuring under load at the same level before the demarcation section strain value deduction immersion of measuring between soaking period, obtain demarcating between soaking period the creep strain of section, obtain and demarcate section with the creep of concrete that the testing time increases, be converted into creeping under unitstress effect; Finally according to creep degree function curve, and from test pile strain testing result, deduct after creep strain under principle of stacking and Linear Creep assumed condition, adopt elastic theory to calculate test pile internal force.Because the strain testing result between soaking period has comprised elastic strain and creep strain, thereby the separation of need creeping.And when the concrete strength of Control experiment stake is greater than 2.5 times of neutral point place stress, can make creeping as Linear Creep of pile body concrete generation, adopt Linear Creep theory to eliminate the creep of concrete causing under long duration load, when compressive stress hour, the limiting value of having crept under stress long term, and the value of creeping is any time approximated to direct ratio with stress, be that creep degree and stress are irrelevant, concrete creeping meets principle of stacking, in time dependent loading situation, the typical case who sets up according to the stress increment principle of stacking expression formula of creeping.

8, considered the impact of creep of concrete in the long-term test process of pile foundation internal force, can be easy from pile strain test result, separated creep strain fast and accurately, test result is approached as far as possible actual, grasp more accurately the real stress state of pile body, thereby improved the precision of test and the reliability of data, its measuring accuracy is high and test data reliability is strong.Meanwhile, utilize the more constant principle of underground water temperature, the temperature of upper and lower pile body is unified to the temperature identical with underground water, thus reduced the impact of temperature on pile strain, make test data good stability, certainty of measurement is higher.

9, due in pile foundation submerging test, the amount of creeping that pile concrete produces under action of long-term load is larger, should take into full account the impact that under action of long-term load, pile body is crept, otherwise can bring considerable influence to the pile side resistance analysis result in loading procedure after negative friction and later stage pile peripheral earth settlement stability, the deviation of occurrence law even, and adopt the present invention can be simply, facilitate and effectively Creep Effect separated, test result is more accurate, practical value is high, and popularizing application prospect is extensive.

In sum, the simple and convenient test of the inventive method step, can be easy from pile strain test result, separated creep strain fast and accurately, makes test result approach as far as possible the actual stress state of pile body.

Below by drawings and Examples, technical scheme of the present invention is described in further detail.

Accompanying drawing explanation

Fig. 1 is test method FB(flow block) of the present invention.

Stress state schematic diagram when Fig. 2 carries out submerging test for employing the present invention to bored pile.

Fig. 3 is for adopting the present invention to obtain to demarcate the creep structural representation of curve of section strain.

Stress state schematic diagram when Fig. 4 carries out submerging test for employing the present invention to pile for prestressed pipe.

Description of reference numerals:

1-test pile; 2-test pits; 3-demarcation section;

4-tank; 5-test tube; 6-motor-pumped well;

7-pumping equipment; 8-anchoring pile; 9-loading equipemtn;

10-pipeline draws water; 11-hole enlargement pile crown; 12-packing material.

The specific embodiment

Embodiment 1

As shown in Figure 1 and Figure 2, the pile foundation ponding loading test method based on creep strain separation of the present invention, comprises the following steps:

Step 1, constant load load: from top to bottom the test pile 1 of having constructed is loaded, and the load loading on 1 top of test pile is F _n; The stress applying on 1 top of described test pile , in formula, A is the dowel section area of test pile 1.

Described test pile 1 is vertical to the concrete pile being laid in collapsible loess stratum, and test pile 1 leaves pile crown more than ground.

In the present embodiment, described test pile 1 is cylindrical stake, and all side excavations of test pile 1 form that a pile foundation ponding loading test uses test pits 2, described in test pits 2 for flat hole, and mutually concordant at the bottom of the hole in described mark one and described flat hole.Described demarcation section 3 arranged outside have a tank 4, and described tank 4 is coaxial laying with test pile 1 for cylindrical tank and its.The height of described tank 4 is not less than the height of described top mark.

In the present embodiment, a plurality of described marks are even laying, and the spacing between neighbouring two described marks is 1m.

Actual laying while installing also can, according to concrete test needs, adjust accordingly the spacing between neighbouring two described marks in the scope of 0.999m～1.001m.In the present embodiment, a stake footpath for described test pile 1 is 0.846m, and stake long be 60m, the height of described pile crown is h=d3+d4+ △, wherein d3 is the spacing between neighbouring two described marks, d4 is footpath of described test pile 1, △=10cm ± 2cm.The height that the top of described test tube 5 exceeds 1 top of test pile is 8cm～20cm.

In the present embodiment, the test pile 1 described in step 1 is bored pile, and after the stake hole forming of described bored pile, first described test tube 5 is arranged in described stake hole, more described bored pile is carried out to filling concrete construction.

During practice of construction, described test pile 1 can be also the concrete pile of other type.

In the present embodiment, described bored pile top is provided with hole enlargement pile crown 11, described top mark is the mark that is laid in hole enlargement pile crown 11 bottoms, described hole enlargement pile crown 11 tops are provided with a mark, the set mark in described hole enlargement pile crown 11 tops is positioned at mark top, described top and it is the mark adjacent with described top mark, and the set mark in described hole enlargement pile crown 11 tops is in a plurality of described marks, to be positioned at the mark of topmost.

In the present embodiment, adopt anchored pile-testing method to load pile for prestressed pipe 4.During actual tests, also can adopt accumulation load method to load.

In the present embodiment, when test pile 1 is loaded, adopt charger to load from top to bottom.Described charger comprises two at the anchoring pile 8 of test pile 1 left and right sides and is erected on two loading equipemtns 9 between described anchoring pile 8, described loading equipemtn 9 be positioned at test pile 1 directly over.

Described loading equipemtn 9 also comprise be erected on two reaction beams between described anchoring pile 8, be laid in the transfer beam directly over test pile 1 and be positioned at test pile 1 directly over and be laid in the loading equipemtn in described transfer beam, described reaction beam pads pressurization beam is housed above described loading equipemtn and between the two.Described transfer beam middle part has the test tube preformed hole passing for test tube 5.In the present embodiment, described pressurization beam and described reaction beam be all positioned at test pile 1 directly over, two described anchoring pile 8 symmetries are laid in the left and right sides of test pile 1.

During actual use, described loading equipemtn comprises a plurality of jack of along the circumferential direction laying, and a plurality of described jack are even laying.In the present embodiment, the quantity of described jack is two.

During actual loading, take the mode of stage loading that test pile 1 is loaded on to trial load, i.e. F _n.

Pile strain value and Internal forces test before step 2, immersion: during stake to be tested 1 settlement stability, adopt slip micrometer to test the strain value at test pile 1 pile body different depth place, and process according to test result analysis pile body axle power and the pile side resistance that draws the front test pile of immersion 1 pile body different depth place.

Before test pile 1 being loaded in step 1, first, in the test tube 5 of the described slip micrometer of the interior laying of test pile 1, described test tube 5 is vertically to being laid in the pile body of test pile 1; Described test tube 5 is comprised of plasticity sleeve pipe and a plurality of mark being arranged on from the bottom to top on described plasticity sleeve pipe of the equal opening in upper and lower two ends.In a plurality of described marks, the mark mutually concordant with ground is mark one.In a plurality of described marks, be positioned at described mark one top and the mark adjacent with described mark one is top mark, described top mark is positioned at demarcates section 3, and the distance between described top mark and 1 top of test pile is greater than the external diameter of test pile 1.The sections of described test pile 1 between described top mark and described mark one is for demarcating section 3.

In the present embodiment, when test pile 1 is soaked in step 3, adopt pumping system to continue to the interior water filling of tank 4, institute injects underground water and fills with after tank 4, overflows that flowing into tests pits 2 also freely descends maceration to steep the residing collapsible loess of test pile 1 stratum from tank 4.

Described pumping system comprises draws water pipeline 10 and underground water is delivered to the pumping equipment 7 in tank 4 by the pipeline 10 that draws water, described in draw water rear end and the pumping equipment 7 of pipeline 10 join, and the front end of the pipeline 10 that draws water extends the bottom land of tank 4 from top to bottom.

In the present embodiment, described pumping equipment 7 is from the interior groundwater abstraction of motor-pumped well 6.

The bottom of described tank 4 is provided with a plurality of water seepage holes, and a plurality of described water seepage holes are along the circumferential direction evenly laid in the surrounding outside of test pile 1, and a plurality of described water seepage hole is all vertically to laying.In the present embodiment, the quantity of described water seepage hole is two.

In the present embodiment, the internal diameter Φ 2=c * Φ 1 of described tank 4, wherein Φ 1 is the diameter of test pile 1, and c=1.2～2.

During practice of construction, can according to specific needs, the internal diameter Φ 2 of tank 4 be adjusted accordingly.

To sum up, described test pile 1 leaves more than 2 the ground of testing pits demarcates section 3, around demarcating section, within 3 one weeks, is provided with tank 4, the interior test tube 5 that is longitudinally provided with of test pile 1.Described 2 outer motor-pumped well 6 and the pumping equipments 7 that are provided with groundwater abstraction of testing pits, test pits in 2 and are provided with anchoring pile 8 and loading equipemtn 9.

In the present embodiment, while adopting described slip micrometer to test the strain value at test pile 1 pile body different depth place, the strain value at the test pile 1 pile body different depth place that described slip micrometer test draws, for comparing after described charger loading with before loading, the strain value that described test pile 1 pile body different depth place occurs.That is to say, before loading, first adopt described slip micrometer to test in step 1, the measured value at the test pile 1 pile body different depth place that now test draws is just initial displacement value; After loading and after stake to be tested 1 settlement stability, adopt again described slip micrometer to test, the measured value at the test pile 1 pile body different depth place that now test draws is just shift value after loading, and after the loading at described test pile 1 pile body different depth place, the difference of shift value and initial displacement value is just loaded load F _ntime test pile 1 pile body different depth place strain value, and this stress value for immersion before the strain value at test pile 1 pile body different depth place.Subsequently, the strain value at test pile 1 pile body different depth place before the immersion drawing according to test, analyzing and processing draws pile body axle power and the pile side resistance at the front test pile of immersion 1 pile body different depth place.

The strain value at test pile 1 pile body different depth place before the immersion drawing according to test, before analyzing and processing draws and soaks, the test pile 1 pile body axle power at pile body different depth place and the process of pile side resistance are as follows:

First, before the immersion drawing according to described slip micrometer test, the strain value at test pile 1 pile body different depth place, draws out loaded load F _ntime pile body actual measurement strain curve.

When the quantity of described test tube 5 is one, described pile body actual measurement strain curve is that described slip micrometer is tested the front test pile 1 pile strain value of the immersion drawing with the curve of change in depth;

When the quantity of described test tube 5 is many, the corresponding strain value that draws the front test pile of many group immersions 1 pile body different depth place of described slip micrometer, before many group immersions, the strain value at described test pile 1 pile body different depth place is corresponding with a plurality of test tubes 5 respectively, and the mean strain value that described pile body actual measurement strain curve is the front test pile 1 of immersion is with the curve of change in depth, and described mean strain value is the average of the strain value at described test pile 1 pile body different depth place before many group immersions.

In actual test process, when the quantity of described test tube 5 is many, the quantity of slip micrometer used is a plurality of, correspondingly by a plurality of test probes that are used in conjunction with many described test tubes 5, carry out synchronism detection respectively, and a plurality of described test probe is worn supplementary biography by measured data and is delivered to data collecting instrument.That is to say, a plurality of described test probes are synchronously tested.

Secondly, adopt the polynomial fitting method of pile strain curve, above-mentioned pile body actual measurement strain curve is carried out to matching, obtain loaded load F _ntime test pile 1 pile strain matched curve; The pile body matching strain value that described pile strain matched curve is test pile 1 is with the curve of change in depth.

Afterwards, according to formula calculate the pile concrete modulus of elasticity of test pile 1.

In formula, A is that the dowel section area Qie Qi unit of test pile 1 is m ², Q _ifor the load F loading on 1 top of test pile _nqie Qi unit is kN; ε _0ifor stake top loaded load F _nthe matching strain value on 1 top of Shi Suoshu test pile, the pile strain matched curve that it can draw according to matching draws.

Then, according to formula P ₀(z)=AE _iε _i(z), calculate the pile body axle power before the immersion of the test pile arbitrary depth z of 1 pile body place.

In formula, A is that the dowel section area Qie Qi unit of test pile 1 is m ², ε _i(z) for the pile strain matched curve drawing according to matching draws the matching strain value at the test pile arbitrary depth z of 1 pile body place, P ₀(z) be the pile body axle power before test pile 1 pile body depth z place immersion, E is the pile concrete modulus of elasticity of test pile 1.

Subsequently, according to formula calculate the pile side friction before the immersion of the test pile arbitrary depth z of 1 pile body place.

In formula, D is that the external diameter Qie Qi unit of test pile 1 is m, P ₀(z) be the pile body axle power before test pile 1 pile body depth z place immersion.

Finally, according to formula calculate the end resistance of test pile 1; A in formula ₀for the stake end cross-sectional area Qie Qi unit of test pile 1 is m ², Q _na kN of Zhou Liqieqi unit holding for test pile 1.

Step 3, immersion and pile strain value test between soaking period: during stake to be tested 1 settlement stability, test pile 1 is soaked, now to maintain the load time be τ to the pile top load of test pile 1 ₀(that is to say, now the load age of test pile 1 is τ ₀); After immersion, per interval Δ t, adopts described slip micrometer once to test the strain value at test pile 1 pile body different depth place; Wherein, Δ t=24 hour ± 5 hours; And after m test, the actual measurement strain value at the test pile 1 pile body different depth place in m the different test moment between corresponding acquisition soaking period.

Wherein, between soaking period, m different tests are respectively t constantly from front to back ₁, t ₂, t ₃t _m, the time interval between adjacent two tests constantly in front and back is Δ t, and pile top load maintains load time τ ₀be positioned at test t constantly ₁the time interval before and between the two is Δ t.

Between soaking period, the stress applying on 1 top of described test pile remains unchanged.

In the present embodiment, Δ t=24 hour, one day.In actual test process, can be according to actual needs, to Δ, t adjusts accordingly.In step 1, F _n=3000kN, before immersion, classification is forced into 3000kN; Under this load action, after the settlement stability of stake top, to the 2 interior immersions of testing pits, in pile peripheral earth generation self-collapsibility infall process, maintain stake top 3000kN load constant; From immersion day, start at after 71 days (stopping to the 2 interior immersions of testing pits soaking 53 days), pile peripheral earth distortion is stable.

Step 4, a demarcation section actual measurement creep degree function obtain, and its acquisition process is as follows:

Step 401, the strain of demarcating section between soaking period calculatings of creeping: according to the test result in step 2 and step 3, by the strain value of m between soaking period different tests demarcation section 3 constantly, all demarcate after sections 3 strain value acquisition stress before deduction immersion the strain of lower m the different tests of effect demarcation section 3 is constantly crept.

Wherein, demarcate the strain value of section 3, be specially the strain value between described top mark and described mark one.

The strain of demarcating section under step 402, the unitstress effect calculating of creeping: by stress in step 401 the strains of lower m the difference test of effect demarcation section 3 are constantly crept, and the strain that is converted to the demarcation section 3 in m the different test moment under unitstress effect is crept.

During actual conversion, only need be by stress in step 401 the strains of the demarcation section 3 in lower m the different test moment of effect are crept, all divided by after, the strain that just obtains the demarcation section 3 in m the different test moment under unitstress effect is crept.

In the present embodiment, the strain of the demarcation section 3 in m the different test moment under unitstress effect is crept, in described point mode, be plotted in and take stake top load and maintain the load time as abscissa and take the strain of demarcating section 3 and creep in the plane right-angle coordinate of ordinate, carry out again afterwards Function Fitting.

Step 403, a demarcation section creep degree Function Fitting: according to the strains of the demarcation section 3 in m the different test moment under the unitstress effect obtaining in step 402, creep, adopt polynomial fitting method, simulate the creep degree function C (t, the τ that between soaking period, demarcate section 3 ₀), and described creep degree function C (t, τ ₀) be that test pile 1 is τ in load age ₀time creep degree function.

Described creep degree function C (t, τ ₀) for load age be τ ₀time demarcate section 3 under unitstress effect strain creep, with stake top load, maintain the curve that the load time changes, demarcate the section strain curve of creeping, refer to Fig. 3.

To sum up, what the present invention adopted is the method that field measurement mode is obtained creep degree function, and practical operation is very easy, and realizes conveniently, but must carry out having in load stake (being test pile 1), and its method is to arrange and demarcate section 3 near the stake top of test pile 1.And described demarcation section 3 should be apart from stake top certain distance (in the present embodiment, this distance be d4+ △, and wherein d4 is the stake footpath of described test pile 1, △=10cm ± 2cm), to avoid the inhomogeneous pile cutoff of test pile 1 cross section upper stress.In submerging test process, at negative friction test period (after immersion), maintain pile top load F _n(stress applying on 1 top of test pile corresponds to ) constant, monitoring is demarcated section 3 and is maintained with stake top load the creep of concrete that the load time increases, and is converted into creeping under unitstress effect, and adopts curve-fitting method to carry out matching to the monitored data of creeping, obtain creep degree function expression C (t, τ ₀).

The creep degree function of step 5, arbitrary load age obtains: according to the creep degree function C (t, the τ that simulate in step 403 ₀), and adopt aging mechanism, nativistic theory or aging and congenital binding isotherm, extrapolate described test pile 1 at arbitrary load age τ _itime creep degree function C (t, τ _i), i=1,2,3 wherein ... m;

When adopting aging mechanism to calculate, C (t, τ _i)=C (t, τ ₀)-C (τ _i, τ ₀);

When adopting nativistic theory (being called again the effect that continues theoretical) to calculate, C (t, τ _i)=C (t-τ _i+ τ ₀, τ ₀);

When adopting aging and congenital binding isotherm to calculate,

$C(t,{\mathrm{\τ}}_i)=\frac{C(t,{\mathrm{\τ}}_0)-C({\mathrm{\τ}}_i,t_0)+C(t-{\mathrm{\τ}}_i+{\mathrm{\τ}}_0,{\mathrm{\τ}}_0)}{2}.$

According to above-mentioned aging mechanism, nativistic theory or aging and congenital binding isotherm, as known load age τ ₀creep of concrete degree fundamental curve C (t, τ ₀), by vertical translation and the horizontal translation of coordinate system, just can obtain respectively arbitrary load age τ _itime creep degree function C (t, τ _i).

Wherein, aging mechanism has been considered the impact of concrete aging on creep deformation; And nativistic theory has been emphasized the heredity of creep deformation.In fact, concrete is fairly obvious in premature ageing feature, and stage main manifestations is heredity.For pile foundation submerging test feature, during immersion, pile concrete length of time is mostly between 28 days to 90 days, according to relevant creep test result, during pile foundation submerging test, creep of concrete truly has and reduces with the increase of load age, adopt nativistic theory can over-evaluate the value of creeping, but adopt aging mechanism also can underestimate the value of creeping.With regard to Analysis of Negative Friction result, the negative friction that uses nativistic theory to obtain is less than normal, and that aging mechanism obtains is bigger than normal, and true negative friction value is between the two.Therefore, consider the error that allows in engineering, the negative friction value that nativistic theory and aging mechanism analysis can be obtained is in addition on average as negative friction test value, i.e. aging and congenital binding isotherm.

Step 6, the separated rear pile strain value of creeping between soaking period and Internal forces are calculated: the actual measurement strain value at the test pile 1 pile body different depth place in m the different test moment between the soaking period that test in step 3 is drawn, all eliminate after creep of concrete, obtain between soaking period the separated rear strain value of creeping at m different tests test pile 1 pile body different depth place constantly; Meanwhile, corresponding extrapolating eliminated test pile 1 pile body different depth after creep of concrete and is between soaking period m different tests axle power and the separated rear pile-side negative friction of creeping constantly.

For the arbitrary depth z of test pile 1 pile body, be in any test t constantly _nactual measurement strain value ε _n ^*(z) while eliminating creep of concrete,

According to formula ${\mathrm{\ϵ}}_n\left(z\right)=\frac{P_n\left(z\right)}{\mathrm{EA}}={{\mathrm{\ϵ}}_n}^{*}\left(z\right)-\frac{P_0\left(z\right)}{A}C(t_n,{\mathrm{\τ}}_0)-\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\frac{{\mathrm{\ΔP}}_i\left(z\right)}{A}C(t_n,{\mathrm{\τ}}_i),$ Calculate the arbitrary depth z of test pile 1 pile body and be in any test t constantly _ncreep separated after strain value, wherein n is natural number and n≤m; In formula, ε _n(z) for test pile 1 pile body depth z after eliminating creep of concrete is in test t constantly _ncreep separated after strain value, ε _n ^*(z) the test pile 1 pile body depth z drawing for test in step 3 is in test t constantly _nactual measurement strain value, P _n(z) for test pile 1 pile body depth z after eliminating creep of concrete is in test t constantly _npile body axle power, and

$P_n\left(z\right)=P_0\left(z\right)+\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{\ΔP}}_i\left(z\right);$

${\mathrm{\ΔP}}_n\left(z\right)=\frac{1}{1+\mathrm{EC}(t_n,{\mathrm{\τ}}_n)}\left\{E\right[{{\mathrm{A\ϵ}}_n}^{*}\left(z\right)-P_0\left(z\right)C(t_n,{\mathrm{\τ}}_0)-\underset{i=1}{\overset{n-1}{\mathrm{\Σ}}}{\mathrm{\ΔP}}_i\left(z\right)C(t_n,{\mathrm{\τ}}_i)]-P_0\left(z\right)-\underset{i=1}{\overset{n-1}{\mathrm{\Σ}}}{\mathrm{\ΔP}}_i\},$

P ₀(z) the pile body axle power before soaking in the test pile 1 pile body depth z place drawing for analyzing and processing in step 2, A is the dowel section area of test pile 1, E is the pile concrete modulus of elasticity of test pile 1, C (t _n, τ ₀) be the C of creep degree function described in step 4 (t, τ ₀) at test moment t _ntime functional value, C (t _n, τ _i) be the C of creep degree function described in step 5 (t, τ _i) at test moment t _ntime functional value, C (t _n, τ _n) be creep degree function C (t, τ _n) at test moment t _ntime functional value.

After extrapolating elimination creep of concrete, test pile 1 pile body depth z is in test t constantly _naxle power after, also need according to formula after calculating elimination creep of concrete, test pile 1 pile body depth z is in test t constantly _npile-side negative friction.

The function of creep degree described in step 5 C (t, τ _i) in, the creep degree function when i=n is C (t _n, τ _n).

Meanwhile, in step 6, also need to be in the axle power in m the different test moment between soaking period and the separated rear pile-side negative friction of creeping according to test pile 1 pile body different depth after the elimination creep of concrete of extrapolating, extrapolate the Depth of Neutral of test pile 1 between soaking period.Concrete reckoning process refers to pertinent regulations in < < Code for design of building > > (GB50007-2003), < < technical code for building pile foundation > > (JGJ94-2008) and < < Code for building construction in collapsible loess zone > > (GB50025-2004).

In the present embodiment, when test pile 1 is loaded in step 1, adopt device for measuring force to the described load F being applied on 1 top of test pile from top to bottom _ndetect in real time, and by testing result synchronous driving to data processor.And in loading procedure, adopt displacement detecting unit to detect in real time a stake top settling amount for test pile 1, and by testing result synchronous driving to data processor.

Actual laying while installing, described displacement detecting unit is the displacement transducer being laid on the pile crown of test pile 1.Described device for measuring force is the pressure sensor being laid on described loading equipemtn.Described device for measuring force and described displacement detecting unit all join with described data processor.Described pressure sensor is between described loading equipemtn and pressurization beam, and pressure sensor and described data processor join.

While adopting described slip micrometer to test the strain value at test pile 1 pile body different depth place in step 2, the data collecting instrument of described slip micrometer by test result synchronous driving to data processor, described data processor carries out analyzing and processing to test result, and corresponding pile body axle power and the pile side friction that draws the front test pile of immersion 1 pile body different depth place; And the data collecting instrument of the micrometer that slides described in step 4, the test pile 1 pile body different depth that test is drawn is in the actual measurement strain value synchronous driving in m the different test moment between soaking period to described data processor, described data processor carries out analyzing and processing according to step 5 to the method described in step 7 again, and respective handling show that eliminating test pile 1 pile body different depth after creep of concrete is between soaking period m different tests creep separated rear strain value, pile body axle power and pile-side negative friction constantly.

During practice of construction, the quantity of test tube described in step 25 is one or more.

When the quantity of described test tube 5 is many, the structure of many described test tubes 5 and size are all identical, and many described test tubes 5 are along the circumferential direction evenly laid in test pile 1;

While adopting described slip micrometer to test the strain value at test pile 1 pile body different depth place in step 2, the strain value at test pile 1 pile body different depth place before the many groups of immersions that corresponding acquisition is drawn by many described test tube 5 tests respectively, after afterwards the strain value at test pile 1 pile body different depth place before many groups of immersions being averaged, obtain the mean strain value at the front test pile of immersion 1 pile body different depth place; Subsequently, according to the mean strain value at the 1 pile body different depth place of test pile before obtained immersion, extrapolate pile body axle power and the pile side resistance at the front test pile of immersion 1 pile body different depth place;

In step 3, after m test, corresponding acquisition tests by many described test tubes 5 the many groups test data drawing respectively, and each organizes the actual measurement strain value that described test data includes the test pile 1 pile body different depth place in m the different test moment between soaking period;

M the different strain value of testing demarcation section 3 constantly between soaking period in step 401, correspondence is respectively the mean strain value that many described test tubes 5 are tested the demarcation section 3 in m the different test moment between the soaking period drawing;

ε described in step 6 _n ^*(z) the test pile 1 pile body depth z, drawing for many described test tube 5 tests is in test t constantly _naverage actual measurement strain value.

In the present embodiment, the quantity of test tube described in step 25 is two.During practice of construction, can test needs according to reality, the quantity of test tube 5 is adjusted accordingly.

To sum up, because creep of concrete refers to concrete while remaining unchanged (be stress) under the long term of a certain constant load, the phenomenon of its strain increase with time.

Creep and increase and can extend over scores of years, but most ofly in 1-2, occur, front 2-6 month with fastest developing speed, to load age, is the concrete of 28 days, and during convergence, (pile top load maintains load time=∞) crept and reached 2～4 with the ratio of elastic strain.Strictly speaking, should adopt the nonlinear criterion of creeping to predict the creep deformation of concrete structure, but at present Non-linear Creep theory does not also reach practical stage, thereby usually think approx and between creep deformation and its stress, exist linear relationship, obedience Boltzman principle of stacking.Under the following conditions, measured result and principle of stacking (or linear relationship) are very approaching:

1) numerical value of stress is lower than 40%～50% of concrete strength, or says within working stress scope;

2) strain value does not reduce during the course;

3) process of creeping does not experience significant dry;

4) after original upload, stress value does not increase considerably.

Compare with any one of first three condition, run counter to the error that last condition causes less, last condition conventionally can be ignored when calculating.In pile foundation submerging test, condition 1) and 3) can realize by human intervention; Condition 2) substantially satisfied, i.e. in pile foundation submerging test, due to the development gradually of negative friction, pile strain increases gradually.Under principle of stacking and Linear Creep assumed condition, creep and can be expressed as: ${\mathrm{\&epsiv;}}_c\left(t\right)=\mathrm{\&sigma;}\left({\mathrm{\&tau;}}_0\right)C(t,{\mathrm{\&tau;}}_0)+{\&Integral;}_{{\mathrm{\&tau;}}_0}^{t}C(t,\mathrm{\&tau;})\mathrm{d\&sigma;}\left(\mathrm{\&tau;}\right)---\left(2\right);$ Formula (2) is discrete, have: ${\mathrm{\&epsiv;}}_c\left(t\right)=\mathrm{\&sigma;}\left({\mathrm{\&tau;}}_0\right)C(t,{\mathrm{\&tau;}}_0)+\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{\mathrm{\&Delta;\&sigma;}}_{i}C(t,{\mathrm{\&tau;}}_i)---\left(3\right);$ ε in formula (3) _c(t) be t creep strain constantly, σ (τ ₀) be τ ₀the stress constantly applying, Δ σ _ifor τ _ithe stress constantly applying, C (t, τ ₀) for load age be τ ₀time creep degree function, C (t, τ _i) for load age be τ _itime creep degree function.

In conjunction with the definition of creep of concrete, the essence of formula (3) is the amount of creeping of some constant load superposition calculation time dependent loadings that continually varying load is separated into.Use it to calculate creeping of pile concrete, need know discrete load (Δ σ _i) application time τ _i.Load time τ due to afterbody load before immersion ₀for known, can calculate different testing time t in pile foundation submerging test _n(n=1,2,3 ...) pile body axle power.

Get arbitrary strain testing section (being the test pile arbitrary depth z of 1 pile body place) for research object, before immersion, under pile top load effect, the axle power after test pile 1 settlement stability is P ₀(z) (load time is shorter, can not consider to creep, and directly by formula (3), calculates pile body axle power), after immersion, along with the development of negative friction, arbitrary test is t constantly _naxle power be: Δ P in formula (4) _i(z) be continually varying, but when Internal Force Monitoring interval (being Δ t) is little, continually varying axle power can be carried out discretely, suppose Δ P _i(z) at this testing time t _iwith testing time last time t _i-1(when i=1, t _i-1for τ ₀) in the middle of τ constantly _iconcentrate and occur.

, according to elastic theory, have: $\mathrm{EA}({{\mathrm{\&epsiv;}}_n}^{*}\left(z\right)-{\mathrm{\&epsiv;}}_c\left(t\right))=P_0\left(z\right)+\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{\mathrm{\&Delta;P}}_i\left(z\right)---\left(5\right);$ In formula (5), E is the pile concrete modulus of elasticity of test pile 1, and A is the dowel section area (being the cross-sectional area of test pile 1 pile body) of test pile 1, ε _n ^*(z) be test moment t _nthe actual measurement strain value that test draws, ε _c(t) be test moment t _ncreep strain (be ε _n(z)), n is test moment t between soaking period _nthe internal force testing time of having monitored.

By formula (3) substitution formula (5), after arrangement, can obtain:

${\mathrm{\&Delta;P}}_n\left(z\right)=\frac{1}{1+\mathrm{EC}(t_n,{\mathrm{\&tau;}}_n)}\left\{E\right[{{\mathrm{A\&epsiv;}}_n}^{*}\left(z\right)-P_0\left(z\right)C(t_n,{\mathrm{\&tau;}}_0)-\underset{i=1}{\overset{n-1}{\mathrm{\&Sigma;}}}{\mathrm{\&Delta;P}}_i\left(z\right)C(t_n,{\mathrm{\&tau;}}_i)]-P_0\left(z\right)-\underset{i=1}{\overset{n-1}{\mathrm{\&Sigma;}}}{\mathrm{\&Delta;P}}_i\}---\left(6\right),$

According to formula (4) with can recursion calculate n(n=1 between soaking period, 2,3 ...) inferior (i.e. test is t constantly _n) the axle power in internal force when test, can be used as the fundamental formular of pile foundation submerging test internal force test result analysis.

The elastic strain of eliminating after creep of concrete is:

${\mathrm{\&epsiv;}}_n\left(z\right)=\frac{P_n\left(z\right)}{\mathrm{EA}}={{\mathrm{\&epsiv;}}_n}^{*}\left(z\right)-\frac{P_0\left(z\right)}{A}C(t_n,{\mathrm{\&tau;}}_0)-\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}\frac{{\mathrm{\&Delta;P}}_i\left(z\right)}{A}C(t_n,{\mathrm{\&tau;}}_i)---\left(7\right).$

To sum up, owing to affecting, the factor of creep of concrete is a lot, mainly comprises concrete composition, ambient conditions (comprise and making and curing condition), stress situation, scantling etc. (wherein the concrete in air-tight state, scantling does not affect and creeps).For guaranteeing that test obtains demarcating preferably the section curve of creeping, (be creep degree function C (t, τ ₀)) and representative, test pile 1 and monitoring time interval (being Δ t) should meet following requirement:

The first, concrete strength of pile:

Formula (6) is according to the theoretical the strength of the axle is calculated formula of deriving of Linear Creep, only have when greatest axis power is less than 0.4～0.5 times of concrete strength and could be suitable for, over this value, creep non-linear by presenting, creep degree curve, by relevant with stress intensity, makes the problem of creeping more complicated.Therefore, should and estimate downdrag size according to the size of the negative friction test period stake top load that loads, the proper strength grade (being the strength grade of concrete of test pile 1 pile body) of selecting test pile 1, makes the compressive strength of pile concrete be greater than 2.5 times of neutral point place stress; Otherwise, also can and estimate downdrag size according to concrete strength of pile grade, control the size of the stake top load that loads.

The second, submerging test operating mode:

While adopting field trial test creep degree function due to need, thereby must carry out having in load stake, therefore should not carry out separately the test without the negative friction of load stake.When need having the creep degree application of curve that records in load stake on without load stake time, concrete composition, Finish time and the ambient conditions etc. of two should be basic identical.

Three, the Internal Force Monitoring time interval (being Δ t):

Because the present invention is undertaken discrete by continually varying axle power, and the time of origin of supposing axle power increment is the middle moment twice Internal Force Monitoring time, therefore the time interval of Internal Force Monitoring is unsuitable oversize, especially at the immersion initial stage, creep and increase rapidly, and immersion initial stage and cutting off the water during initial stage negative friction (pile body axle power) increases rapidly, generally get 24 hours.

Four, temperature and humidity is controlled:

Due in Collapsible Loess District below ground soil temperature more than 5m be subject to the impact of atmospheric temperature comparatively serious, and the temperature below 5m is comparatively constant below ground.

And that pile foundation submerging test lasts is longer, toward contact, cross over Various Seasonal, atmospheric temperature amplitude of variation is larger, do not take measures to make the under-represented of a creep strain that pushes up near demarcation section 3, (1 ℃ of the every rising of concrete temperature, will produce approximately 12.4 * 10 even to occur surveying the situation that strain is comparatively chaotic ^-6mPa ^-1creep strain).Therefore, should take measures to make the temperature of demarcation section 3 comparatively constant, and basic identical with the bottom pile body (being arranged in the pile body of soil) of below ground, when adopting underground water as immersion water source, can around demarcating section 3, a tank 4 be set, allow underground water from bottom, enter tank 4, top is overflowed and being entered immersion and test pits 2, with play demarcate section 3 temperature substantially constants and with the essentially identical object of bottom pile body temperature.Meanwhile, also there is the problem similar with temperature in the humidity of demarcating section, if water seepage hole is set in tank 4, can make the concrete humidity of upper and lower pile body (one of curing condition) reach rapidly basic identical, demarcates the section 3 creep degree functions that record more representative.

Embodiment 2

As shown in Figure 4, in the present embodiment, as different from Example 1: the test pile 1 described in step 1 is pile for prestressed pipe; After described prestressing pipe pile construction completes, then in the described pile for prestressed pipe completing in construction, test tube 5 is installed, and described test tube 5 is vertically to the pipe pile core middle part that is laid in described pile for prestressed pipe; Described top mark is in a plurality of described marks, to be positioned at the mark of topmost.And the quantity of described test tube 5 is one.The pile body cross section of described pile for prestressed pipe is annular, and because stake underseal closes, thereby described pile for prestressed pipe end cross section is circular.

After described test tube 5 installations, adopt again grouting equipment in the pipe pile core of described pile for prestressed pipe and the cavity between test tube 5, to inject packing material 12 from the bottom to top, the mixed serum of described packing material 12 for being uniformly mixed to form according to the ratio of weight ratio 1000 ︰ 600～1200 ︰ 75 by water, cement and swell soil.

Thereby in the present embodiment, the mounting method of test tube 5 is different from embodiment 1.When reality is installed test tube 5, its installation process is as follows:

Water filling in step 101, pile for prestressed pipe: after described prestressing pipe pile construction completes, fill with water to the pipe pile in-core of pile for prestressed pipe.

Described pile for prestressed pipe sealed bottom is welded with steel pile tip, and described pipe pile core bottom seals the rear water storage cavity that top has that forms by steel pile tip.

In practice of construction process, when pile for prestressed pipe is constructed, according to the construction method of conventional prestressed concrete pile, construct.In the present embodiment, described pile for prestressed pipe is assemblied to form from the bottom to top by a plurality of pile sections, and the joint location between neighbouring two described pile sections adopts welding manner to be connected and sealed.When pile for prestressed pipe is constructed, according to conventional method, complete successively stake, pitching pile, pile sinking, pile extension and the pile follower process of hanging.Actual while carrying out pile extension, adopt welding equipment around pile for prestressed pipe joint location one week, and neighbouring two described pile sections are integrally welded.And when pile for prestressed pipe is carried out to pile sinking, take the form of construction work of pile sinking section by section, and the pile-sinking method adopting comprises hammering method, static pressure method, lash method, water jetting, prebored hole method, middle pick method etc., wherein static pressure method is with the most use.In the present embodiment, adopt static pressure method to carry out pile sinking.

To sum up, before pile for prestressed pipe is constructed, first in a plurality of the above pile section, be positioned at the pile section sealed bottom weldable steel pile top of foot.After prestressing pipe pile construction completes, the more than 7 reserved pile crown on ground.Due to a stake end weldable steel pile top sealing stake end for, pile for prestressed pipe, and the joint of adjacent two described pile sections adopts welding manner to be connected and sealed, thereby can effectively guarantee to described pipe pile in-core water filling time, seepage does not occur position while welding.

Step 102, test tube are installed: described test tube 5 is connected to form from bottom to up by a plurality of test tube sections, and be tightly connected between adjacent two test tube sections, the test tube sections that is positioned at foot in many described test tube sections is that bottom test tube sections and its bottom seal by seal cover, thereby can effectively guarantee to described test tube 5 interior water filling time, there is not seepage.In the present embodiment, described plasticity sleeve pipe is HPVC pipe (plastic conduit).

The test probe of described slip micrometer be two ends with the probe of spheric probe, and the length of described test probe is identical with the spacing between neighbouring two marks; The in-built LVDT displacement meter of described test probe and a NTC thermometer.In the present embodiment, described plasticity sleeve pipe is divided into a plurality of plasticity cover tube segment by a plurality of described marks, between neighbouring two marks, all by described plasticity cover tube segment, connects.

And the installation process of described test tube 5 is as follows:

Step 1021, bottom test tube sections are transferred: first by described bottom test tube sections vertically to be positioned over described pipe pile core directly over, adopt again to the mode of water filling continuously in the test tube sections of described bottom, described bottom test tube sections is vertically sunk gradually, is h until test tube sections top, described bottom exceeds the height of described pipe pile in-core water level; H=30cm～70cm wherein;

In the present embodiment, h=50cm.During practice of construction, can, according to the concrete needs of reality, the numerical value of h be adjusted accordingly within the scope of 30cm～70cm.

Step 1022, a upper test tube sections connect height and transfer: the test tube sections that upper need are installed is sealedly attached to has now transferred on the test tube sections putting in place, all test tube sections that now current transferred test tube sections is connected with its underpart form a water-injecting cavity, and all test tube sections that current transferred test tube sections is connected with its underpart are all coaxial laying; Afterwards, by the mode of continuous water filling in described water-injecting cavity, all test tube sections that the test tube sections that current need are transferred is connected with its underpart vertically sink in the lump gradually, until current transferred test tube sections top exceeds the height of described pipe pile in-core water level, are h.In the present embodiment, h=50cm.

Step 1023, repeating step 1022 repeatedly, until complete the decentralization process of all test tube sections in described test tube, the bottom of now described test tube 5 installations, and described bottom test tube sections and the bottom connection of described pipe pile core touch.

After described test tube 5 installations, water is filled in its inside.

After 5 installations of test tube described in step 1, the height that the top of described test tube 5 exceeds pile for prestressed pipe stake top is 8cm～20cm.The mark that is positioned at foot in a plurality of described marks is bottom mark, and the distance of described bottom mark and described pipe pile core bottom is d3, wherein 10cm < d3 < 30cm.

In the present embodiment, the height that the top of described test tube 5 exceeds 4 tops of pile for prestressed pipe is 10cm.During practice of construction, can be according to specific needs, the height that test tube 5 tops is exceeded to 4 tops of pile for prestressed pipe adjusts accordingly.The length of described test tube sections is 3m～4m.

In the present embodiment, described plasticity sleeve pipe is connected to form by more piece plasticity cover tube segment, and between neighbouring two plasticity cover tube segment, mark is installed.Before reality is installed test tube 5, first plasticity sleeve pipe being become to joint length with mark pre-connection is the test tube sections of 3m～4m.When described test tube sections is carried out to pre-connection, after first the joint location of neighbouring two need connection plasticity sleeve pipe sections all being smeared to one deck all-purpose adhesive, dock, the joint that the plasticity that adopts again adhesive waterproof tape to connect neighbouring two need is overlapped between tube segment seals, specifically in the outside adhesive waterproof tape 24-17 lap seal in turn that adopts of joint.To sum up, in described test tube 5, between neighbouring two plasticity cover tube segment, all adopt omnipotent glue-line and adhesive waterproof tape to carry out waterproofing work to the joint location between neighbouring two plasticity cover tube segment.

In the present embodiment, the quantity of described test tube 5 is one.During practice of construction, be not more than the pile for prestressed pipe of Φ 600m for internal diameter, the quantity of its pipe pile test tube that in-core is installed 5 is one.

In actual installation process, for guaranteeing the accuracy of test tube 5 installation sites, along the depth direction of pile for prestressed pipe, every 2m～3m, a centralizer one is set test tube 5 is fixed on to the test position of design in advance.Described test tube 5 is carried out in installation process, synchronously from the bottom to top a plurality of described centralizers one are installed respectively.Described centralizer one comprises the collar, the lower collar under the upper collar and is along the circumferential direction connected in the rib frame that a plurality of ribs between the collar and lower collar form, the structure of the described upper collar and lower collar and size all identical and the two be all level to laying.The structure of a plurality of described ribs and size are all identical; The internal diameter of the described upper collar and lower collar is all less than the external diameter of mark and the external diameter that the internal diameter of the two is all greater than plasticity sleeve pipe, and the spacing between a plurality of described ribs and described pile for prestressed pipe inside wall is d1, wherein d1=3mm～8mm; Space D 1=c * d between the described upper collar and lower collar ₀, wherein c=1～2, and d ₀internal diameter for pile for prestressed pipe.

During practice of construction, when the quantity of described test tube 5 is many, the structure of many described test tubes 5 and size are all identical.And while carrying out test tube installation, many described test tubes 5 are synchronously installed, and the installation progress of many described test tubes 5 is all identical.The mounting method of many described test tubes 5 is all identical, and all according to step 1021 to the method described in step 1023, installs.

When the internal diameter of pile for prestressed pipe is greater than Φ 600m, the quantity of described test tube 5 is many, and many described test tubes 5 are along the circumferential direction evenly laid.For guaranteeing the accuracy of many described test tube 5 installation sites, many described test tubes 5 are assembled into one by a plurality of centralizers two of laying from the bottom to top, and many described test tubes 5 are assembled into a test tube group.Spacing between neighbouring two described centralizers two is 2m～3m.Described test tube group is vertical to the inside center place that is laid in described pipe pile core under the centralizing function of a plurality of described centralizers two.And many described test tubes 5 are carried out in synchronous installation process, synchronously from the bottom to top a plurality of described centralizers two are installed respectively.Because structure and the size of many described test tubes 5 are all identical, the installation site of a plurality of described mark 10 of installing in many described test tubes 5 is all identical, thus in many described test tubes 5 mark at same depth place in same level.

Described centralizer two comprises annulus and is positioned at the lower annulus under annulus, described upper annulus and lower annulus inside are provided with the interior annulus that many described test tubes 5 of a plurality of confessions are passed, and along the circumferential direction evenly laying and its installation position are corresponding one by one with the installation position of many described test tubes 5 for a plurality of described interior annulus.Uniform being located in same level of all interior annulus that described upper annulus and its are inner set, and all by transverse connection, be connected between upper annulus all interior annulus set with its inside.Uniform being located in same level of all interior annulus that described lower annulus and its are inner set, and all by transverse connection, be connected between lower annulus all interior annulus set with its inside.Between described upper annulus and lower annulus, by vertical connector, be connected.Described upper annulus is identical with the quantity of many described test tubes 5 with the quantity of set interior annulus in lower annulus, and in described upper annulus and lower annulus, the diameter of set interior annulus is all identical.The internal diameter of described interior annulus is less than the external diameter of mark and it is greater than the external diameter of plasticity sleeve pipe.Identical and the two the diameter of the diameter of described upper annulus and lower annulus is than the little 3mm～8mm of the internal diameter of pile for prestressed pipe.Space D 2=c * d between described upper annulus and lower annulus ₀, wherein c=1～2, and d ₀internal diameter for pile for prestressed pipe.

Described test tube 5 installations, adopt grouting equipment in the cavity between described pipe pile core and test tube 5, to inject packing material 12 from the bottom to top, and grouting pressure is 0.2MPa ± 0.02MPa.In the present embodiment, described packing material 12 is for evenly to be mixed according to the ratio of weight ratio 1000 ︰ 1000 ︰ 75 by water, cement and swell soil, during practice of construction, can according to specific needs, water, cement and bentonitic weight ratio be adjusted accordingly in the scope of 1000 ︰ 600～1200 ︰ 75.The swell soil adopting is sodium bentonite or calcium-base bentonite.

In the present embodiment, described grouting equipment comprises grouting pump and the Grouting Pipe of joining with grouting pump.Actual while carrying out slip casting, need be by Grouting Pipe deeply to the pipe pile core bottom of pile for prestressed pipe, and carry out slip casting from top to bottom, in slip casting process like this, the water filling of pipe pile in-core institute is discharged gradually.During practice of construction, before slip casting, also can adopt pumping equipment that the water filling of described pipe pile in-core institute is all extracted out.

Of the present invention by water, cement and swell soil all the test philosophy of the mixed packing material 4 forming be: the admixture of water makes each component in packing material 12 be easy to stir, be convenient to packing material 6 and be poured into smoothly in the space between pile for prestressed pipe and test tube 5, guarantee that cement carries out normal hydration reaction; Cement is powdery hydraulicity inorganic coagulation material, is the intensity source of packing material 12, can effectively adjust the mechanical property of packing material 6 by adjusting cement factor; Swell soil is to take montmorillonite as main moisture clay pit, there is stronger water swellability, dispersiveness, suspension and pulping, after packing material admixture swell soil, possess good mobility, cohesiveness and water retention etc., improved the performance of packing material 12, constructability is used.In actual test process, pile body deformation passes to test tube 5 by packing material 12.

In test process, between the uniaxial compressive strength of injected packing material 12 uniaxial compressive strength and the uniaxial compressive strength of described pile for prestressed pipe in test tube 5, and inject packing material 12 the single shaft pressure-proof elasticity modulus of single shaft pressure-proof elasticity modulus in test tube 5 and the single shaft pressure-proof elasticity modulus of described pile for prestressed pipe between time, in step 1, can load.

In the present embodiment, described packing material 12 injected after N days, between the uniaxial compressive strength and the uniaxial compressive strength of pile for prestressed pipe of the uniaxial compressive strength of described packing material 12 in test tube 5, and inject packing material 12 the single shaft pressure-proof elasticity modulus and the single shaft pressure-proof elasticity modulus of pile for prestressed pipe of single shaft pressure-proof elasticity modulus in test tube 5 between, now adopt described loading equipemtn pile for prestressed pipe to be loaded from top to bottom; Wherein, N is not less than 14.

Thereby, in actual test process, when described packing material 12 injected after 14 days, just can load.In addition, during actual test, also can adopt uniaxial compressive strength test to determine the load time of described loading equipemtn.

In the present embodiment, all the other method steps and technological principle are all identical with embodiment 1.

The above; it is only preferred embodiment of the present invention; not the present invention is imposed any restrictions, every any simple modification of above embodiment being done according to the technology of the present invention essence, change and equivalent structure change, and all still belong in the protection domain of technical solution of the present invention.

Claims (10)

1. the pile foundation ponding loading test method based on creep strain separation, is characterized in that the method comprises the following steps:

Step 1, constant load load: from top to bottom the test pile of having constructed (1) is loaded, and the load loading on test pile (1) stake top is F _n; The stress applying on described test pile (1) stake top , in formula, A is the dowel section area of test pile (1);

Described test pile (1) is vertical to the concrete pile being laid in collapsible loess stratum, and test pile (1) leaves pile crown more than ground;

Pile strain value and Internal forces test before step 2, immersion: during stake (1) settlement stability to be tested, adopt slip micrometer to test the strain value at test pile (1) pile body different depth place, and process according to test result analysis pile body axle power and the pile side resistance that draws front test pile (1) the pile body different depth of immersion place;

Before test pile (1) being loaded in step 1, first in test pile (1), lay the test tube (5) of described slip micrometer, described test tube (5) is vertically to being laid in the pile body of test pile (1); Described test tube (5) is comprised of plasticity sleeve pipe and a plurality of mark being arranged on from the bottom to top on described plasticity sleeve pipe of the equal opening in upper and lower two ends; In a plurality of described marks, the mark mutually concordant with ground is mark one; In a plurality of described marks, be positioned at described mark one top and the mark adjacent with described mark one is top mark, described top mark is positioned at demarcates section (3), and the distance between described top mark and test pile (1) stake top is greater than the external diameter of test pile (1); The sections of described test pile (1) between described top mark and described mark one is for demarcating section (3);

Step 3, immersion and pile strain value test between soaking period: during stake (1) settlement stability to be tested, test pile (1) is soaked, now to maintain the load time be τ to the pile top load of test pile (1) ₀; After immersion, per interval Δ t, adopts described slip micrometer once to test the strain value at test pile (1) pile body different depth place; Wherein, Δ t=24 hour ± 5 hours; And after m test, the actual measurement strain value at test pile (1) the pile body different depth place in m the different test moment between corresponding acquisition soaking period;

Wherein, between soaking period, m different tests are respectively t constantly from front to back ₁, t ₂, t ₃t _m, the time interval between adjacent two tests constantly in front and back is Δ t, and pile top load maintains load time τ ₀be positioned at test t constantly ₁the time interval before and between the two is Δ t;

Between soaking period, the stress applying on described test pile (1) stake top remains unchanged;

Step 4, a demarcation section actual measurement creep degree function obtain, and its acquisition process is as follows:

Step 401, the strain of demarcating section between soaking period calculatings of creeping: according to the test result in step 2 and step 3, by the strain value of m between soaking period different tests demarcation section (3) constantly, all demarcate after the strain value of section (3) acquisition stress before deduction immersion the strain of lower m the different tests of effect demarcation section (3) is constantly crept;

The strain of demarcating section under step 402, the unitstress effect calculating of creeping: by stress in step 401 the strains of lower m the difference test of effect demarcation section (3) are constantly crept, and the strain that is converted to the demarcation section (3) in m the different test moment under unitstress effect is crept;

Step 403, a demarcation section creep degree Function Fitting: according to the strains of the demarcation section (3) in m the different test moment under the unitstress effect obtaining in step 402, creep, adopt polynomial fitting method, simulate the creep degree function C (t, the τ that between soaking period, demarcate section (3) ₀), and described creep degree function C (t, τ ₀) be that test pile (1) is τ in load age ₀time creep degree function;

The creep degree function of step 5, arbitrary load age obtains: according to the creep degree function C (t, the τ that simulate in step 403 ₀), and adopt aging mechanism, nativistic theory or aging and congenital binding isotherm, extrapolate described test pile (1) at arbitrary load age τ _itime creep degree function C (t, τ _i), i=1,2,3 wherein ... m;

When adopting aging mechanism to calculate, C (t, τ _i)=C (t, τ ₀)-C (τ _i, τ ₀);

When adopting nativistic theory to calculate, C (t, τ _i)=C (t-τ _i+ τ ₀, τ ₀);

When adopting aging and congenital binding isotherm to calculate,

$C(t,{\mathrm{\&tau;}}_i)=\frac{C(t,{\mathrm{\&tau;}}_0)-C({\mathrm{\&tau;}}_i,t_0)+C(t-{\mathrm{\&tau;}}_i+{\mathrm{\&tau;}}_0,{\mathrm{\&tau;}}_0)}{2};$

Step 6, the separated rear pile strain value of creeping between soaking period and Internal forces are calculated: the actual measurement strain value at test pile (1) the pile body different depth place in m the different test moment between the soaking period that test in step 3 is drawn, all eliminate after creep of concrete, obtain between soaking period the separated rear strain value of creeping at m different tests test pile (1) pile body different depth place constantly; Meanwhile, corresponding extrapolating eliminated test pile (1) pile body different depth after creep of concrete and is between soaking period m different tests axle power and the separated rear pile-side negative friction of creeping constantly;

For the arbitrary depth z of test pile (1) pile body, be in any test t constantly _nactual measurement strain value ε _n ^*(z) while eliminating creep of concrete,

According to formula ${\mathrm{\&epsiv;}}_n\left(z\right)=\frac{P_n\left(z\right)}{\mathrm{EA}}={{\mathrm{\&epsiv;}}_n}^{*}\left(z\right)-\frac{P_0\left(z\right)}{A}C(t_n,{\mathrm{\&tau;}}_0)-\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}\frac{{\mathrm{\&Delta;P}}_i\left(z\right)}{A}C(t_n,{\mathrm{\&tau;}}_i),$ Calculate the arbitrary depth z of test pile (1) pile body and be in any test t constantly _ncreep separated after strain value, wherein n is natural number and n≤m; In formula, ε _n(z) for test pile (1) pile body depth z after eliminating creep of concrete is in test t constantly _ncreep separated after strain value, ε _n ^*(z) test pile (1) the pile body depth z drawing for test in step 3 is in test t constantly _nactual measurement strain value, P _n(z) for test pile (1) pile body depth z after eliminating creep of concrete is in test t constantly _npile body axle power, and

$P_n\left(z\right)=P_0\left(z\right)+\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{\mathrm{\&Delta;P}}_i\left(z\right);$

${\mathrm{\&Delta;P}}_n\left(z\right)=\frac{1}{1+\mathrm{EC}(t_n,{\mathrm{\&tau;}}_n)}\left\{E\right[{{\mathrm{A\&epsiv;}}_n}^{*}\left(z\right)-P_0\left(z\right)C(t_n,{\mathrm{\&tau;}}_0)-\underset{i=1}{\overset{n-1}{\mathrm{\&Sigma;}}}{\mathrm{\&Delta;P}}_i\left(z\right)C(t_n,{\mathrm{\&tau;}}_i)]-P_0\left(z\right)-\underset{i=1}{\overset{n-1}{\mathrm{\&Sigma;}}}{\mathrm{\&Delta;P}}_i\},$ P ₀(z) the pile body axle power before soaking in test pile (1) the pile body depth z place drawing for analyzing and processing in step 2, A is the dowel section area of test pile (1), E is the pile concrete modulus of elasticity of test pile (1), C (t _n, τ ₀) be the C of creep degree function described in step 4 (t, τ ₀) at test moment t _ntime functional value, C (t _n, τ _i) be the C of creep degree function described in step 5 (t, τ _i) at test moment t _ntime functional value, C (t _n, τ _n) be creep degree function C (t, τ _n) at test moment t _ntime functional value;

After extrapolating elimination creep of concrete, test pile (1) pile body depth z is in test t constantly _naxle power after, also need according to formula after calculating elimination creep of concrete, test pile (1) pile body depth z is in test t constantly _npile-side negative friction.

2. according to the pile foundation ponding loading test method based on creep strain separation claimed in claim 1, it is characterized in that: the test pile described in step 1 (1) is cylindrical stake, and all side excavations of test pile (1) form test pits (2) that pile foundation ponding loading test is used, described testing pits (2) is flat hole, and mutually concordant at the bottom of the hole in described mark one and described flat hole; Described demarcation section (3) arranged outside has a tank (4), and described tank (4) is coaxial laying with test pile (1) for cylindrical tank and its;

When test pile (1) is soaked in step 3, adopt pumping system to continue to the interior water filling of tank (4), inject underground water and fill with after tank (4), from tank (4), overflow to flow into and test pits (2) and freely descend maceration to steep the residing collapsible loess of test pile (1) stratum;

Described pumping system comprises the pipeline that draws water (10) and underground water is delivered to the pumping equipment (7) in tank (4) by the pipeline that draws water (10), the rear end of the described pipeline that draws water (10) and pumping equipment (7) join, and the front end of the pipeline that draws water (10) extends the bottom land of tank (4) from top to bottom; The height of described tank (4) is not less than the height of described top mark.

3. according to the pile foundation ponding loading test method based on creep strain separation described in claim 1 or 2, it is characterized in that: the quantity of test tube described in step 2 (5) is one or more;

When the quantity of described test tube (5) is many, structure and the size of many described test tubes (5) are all identical, and many described test tubes (5) are along the circumferential direction evenly laid in test pile (1);

While adopting described slip micrometer to test the strain value at test pile (1) pile body different depth place in step 2, the strain value at test pile (1) pile body different depth place before the many groups of immersions that corresponding acquisition is drawn by many described test tubes (5) test respectively, after afterwards the strain value at test pile (1) pile body different depth place before many groups of immersions being averaged, obtain the mean strain value at front test pile (1) the pile body different depth of immersion place; Subsequently, according to the mean strain value at test pile (1) pile body different depth place before obtained immersion, extrapolate pile body axle power and the pile side resistance at front test pile (1) the pile body different depth of immersion place;

After testing for m time in step 3, many groups test data that corresponding acquisition is drawn by many described test tubes (5) test respectively, and each organizes the actual measurement strain value that described test data includes test pile (1) the pile body different depth place in m the different test moment between soaking period;

M the different strain value of testing demarcation section (3) constantly between soaking period in step 401, correspondence is respectively the mean strain value that many described test tubes (5) are tested the demarcation section (3) in m the different test moment between the soaking period drawing;

ε described in step 6 _n ^*(z) test pile (1) the pile body depth z, drawing for many described test tubes (5) test is in test t constantly _naverage actual measurement strain value.

4. according to the pile foundation ponding loading test method based on creep strain separation claimed in claim 2, it is characterized in that: the bottom of described tank (4) is provided with a plurality of water seepage holes (13), a plurality of described water seepage holes (13) are along the circumferential direction evenly laid in the surrounding outside of test pile (1), and a plurality of described water seepage hole (13) is all vertically to laying.

5. according to the pile foundation ponding loading test method based on creep strain separation described in claim 1 or 2, it is characterized in that: when test pile (1) is loaded in step 1, adopt device for measuring force to the described load F being applied on test pile (1) stake top from top to bottom _ndetect in real time, and by testing result synchronous driving to data processor;

While adopting described slip micrometer to test the strain value at test pile (1) pile body different depth place in step 2, the data collecting instrument of described slip micrometer by test result synchronous driving to data processor, described data processor carries out analyzing and processing to test result, and corresponding pile body axle power and the pile side friction that draws front test pile (1) the pile body different depth of immersion place; And the data collecting instrument of the micrometer that slides described in step 3, the test pile that test is drawn (1) pile body different depth is in the actual measurement strain value synchronous driving in m the different test moment between soaking period to described data processor, described data processor carries out analyzing and processing according to step 4 to the method described in step 6 again, and respective handling show that eliminating test pile (1) pile body different depth after creep of concrete is between soaking period m different tests creep separated rear strain value, pile body axle power and pile-side negative friction constantly.

6. according to the pile foundation ponding loading test method based on creep strain separation described in claim 1 or 2, it is characterized in that: in step 6, also need to be in the axle power in m the different test moment between soaking period and the separated rear pile-side negative friction of creeping according to test pile (1) pile body different depth after the elimination creep of concrete of extrapolating, extrapolate the Depth of Neutral of test pile between soaking period (1).

7. according to the pile foundation ponding loading test method based on creep strain separation described in claim 1 or 2, it is characterized in that: the test pile described in step 1 (1) is bored pile, and after the stake hole forming of described bored pile, first described test tube (5) is arranged in described stake hole, more described bored pile is carried out to filling concrete construction.

8. according to the pile foundation ponding loading test method based on creep strain separation described in claim 1 or 2, it is characterized in that: when test pile (1) is loaded in step 1, adopt charger to load from top to bottom; Described charger comprises that two are positioned at the anchoring pile (8) of test pile (1) left and right sides and are erected on the loading equipemtn (9) between two described anchoring piles (8), described loading equipemtn (9) be positioned at test pile (1) directly over.

9. according to the pile foundation ponding loading test method based on creep strain separation described in claim 1 or 2, it is characterized in that: the test pile described in step 1 (1) is pile for prestressed pipe; After described prestressing pipe pile construction completes, then test tube (5) is installed in the described pile for prestressed pipe completing in construction, and described test tube (5) is vertically to the pipe pile core middle part that is laid in described pile for prestressed pipe; Described top mark is in a plurality of described marks, to be positioned at the mark of topmost;

After described test tube (5) installation, adopt grouting equipment from the bottom to top to pipe pile core and the interior packing material (12) that injects of the cavity between test tube (5) of described pile for prestressed pipe, described packing material (12) is the mixed serum being uniformly mixed to form according to the ratio of weight ratio 1000 ︰ 600～1200 ︰ 75 by water, cement and swell soil again.

10. according to the pile foundation ponding loading test method based on creep strain separation described in claim 1 or 2, it is characterized in that: in step 1, a plurality of described marks are even laying, and the spacing between neighbouring two described marks is 1m; Δ t=24 hour in step 3.