CN103528897A - Method for determining critical state parameter in data of large scale triaxial test on coarse-grained soil under high ambient pressure - Google Patents

Abstract

The invention relates to a method for determining a critical state parameter in data of a large scale triaxial test on coarse-grained soil under a high ambient pressure. The method for determining the critical state parameter in data of the large scale triaxial test on the coarse-grained soil under the high ambient pressure comprises the following steps: firstly, placing the coarse-grained soil into a triaxial consolidation drainage shear testing device to be tested; secondly, obtaining data in the test; thirdly, calculating shearing stress in the consolidation drainage shear according to a formula (described in the specification). A component force parameter of a water pressure in axial direction of a test sample is increased, so that the negligence that influence of the water pressure is not considered in regulations in the prior art is overcome, and the formula in the method corrects an error that a shearing stress-axial stress strain curve (q-epsilona) is bent in advance under a high ambient pressure test working condition in a formula (14) in the regulation (SL-237-017-1999); according to the new formula in the method, test data automatically recorded by a computer is calculated, and consistency of critical state points (breaking points) obtained according to the shearing stress-axial stress strain curve (q-epsilona) and a volumetric strain-axial stress strain curve (epsilonv-epsilona) respectively is high, so that the method for determining the critical state parameter in data of the large scale triaxial test on the coarse-grained soil under the high ambient pressure is applicable to engineering application.

Description

Coarse-grained soil large triaxial test data critical conditions parameter determination method under high confining pressure

Technical field

The present invention relates to coarse-grained soil large triaxial test data critical conditions parameter determination method under the coarse-grained soil consolidation draining scissor test field, particularly a kind of high confining pressure in civil engineering work.

Background technology

At present, many countries will or build height of dam at 300m level rock in the world.For example, Philippine is building the Abula rock that 234m is high; Pakistan is building the Basha rock that 270m is high, and after building up, their height of dam is all by the water cloth a strip of land between hills rock (the built the highest rock in the world) higher than Chinese height of dam 233m.And there is the dam site of many suitable construction superelevation rocks in the Yarlung Zangbo River in China Lancang River, Jinsha jiang River, Nujiang, Yalongjiang River, Dadu River and the upper reaches of the Yellow River and Tibet etc.For example height of dam is at Ci Haxia, the Ma Ji of 250m～350m, Gu Shui, as Qi Zong power station, Jinsha jiang River beautiful, height of dam 352m.

Owing to also not having in the world the engineering precedent of 300m level face dam to build up, also just lack construction experiences for reference and measured data.Conventionally dam deformation amount and height of dam are square proportional, along with increasing considerably of height of dam, under deadweight, high hydraulic pressure effect, the dam body maximum settlement of the high face dam of 300m, and be not equal to 2 times of high 150m dam, also be not equal to 1.5 times of the high face dam of 200m, its stress deformation proterties is different from the high face dam of 150m～200m, cannot be according to the experience extrapolation of 150m level or the high face dam of 200m.Therefore, Ma Hongqi academician starts in meeting and proposes in " the high rock adaptability of 300m level and countermeasure ": " 300m level face dam dam deformation is large; therefore tackle intensity and the deformation behaviour further investigation of dam material ", that is to say and will study the constitutive model that is applicable to 300m level rock-fill dams.

At present, the constitutive model based on critical conditions theory become in constitutive model family, grow a lot before shadow and a member of showing unique characteristics.Due to damage of soil body, cut the swollen characteristics such as contracting separation of cutting and have clear and definite definition clearly, and be successfully applied to soil and sand, critical conditions constitutive model has embodied good practical superiority and theoretic tightness.Coarse-grained soil for resembling stockpile and comprise like this greater particle size, has also developed several critical conditions constitutive models.But perplex everybody, because the confined pressure of shop experiment need obtain highlyer, so in large triaxial test, the definite problem of critical conditions parameter of coarse fodder soil becomes extremely important.

" Advanced Soil Mechanics " pointed out: when reaching critical conditions, plasticity shearing strain infinitely increases, plastic volumetric strain increment and effective stress increment are 0, the soil body is in perfect plasticity state, now all effective stress terminals are all positioned at same straight line (stress ratio equals M) above, and this straight line is called critical conditions line.That is to say that, when gravel (gravel) in large triaxial test is in critical conditions, body becomes ε _vno longer change, deviatoric stress q, mean principle stress p also no longer increase., the shape of the stress-strain diagram in the triaxial consolidation Drainage Shear test findings of the coarse-grained soil arranging out according to rules (q-ε curve) is usually that after hump type has arrived peak, q has just declined, and sees Fig. 1.And the peak of conventionally all getting deviatoric stress q is as critical state point, that is to say, soil is once reach critical state point, and deviatoric stress q just starts to decline subsequently.And according to " Advanced Soil Mechanics " definition, deviatoric stress q should be constant or substantially constant.But the triaxial test curve arranging out by rules is inconsistent with the not apparition of deviatoric stress q of definition in " Advanced Soil Mechanics ".Why does is this?

In addition, according to body, become ε _vthe constant critical state point obtaining, obviously partially after according to answering the peak point q of hump type stress-strain diagram (q-ε) to obtain critical state point.The critical state point position being obtained by stress-strain diagram and body change-strain curve is different.

As shown in fig. 1, in existing rules technology by shear stress-axle varied curve q-ε _adefinite breakdown point, obviously with by body change-axle varied curve ε _v-ε _adefinite breakdown point position is inconsistent, thereby causes in Practical Project at a loss as to what to do.

Summary of the invention

Technical matters to be solved by this invention is to provide coarse-grained soil large triaxial test data critical conditions parameter determination method under a kind of high confining pressure, can guarantee the ε by shear stress-axle varied curve q- _awith body change-axle varied curve ε _v-ε _athe soil sample breakdown point position obtaining is consistent.

In order to solve the technical matters of above-mentioned existence, the present invention adopts following technical scheme: coarse-grained soil large triaxial test data critical conditions parameter determination method under a kind of high confining pressure, comprises the following steps:

One, coarse-grained soil specimen being put into triaxial consolidation Drainage Shear test unit tests;

Two, obtain in test data;

Three, the new formula of being derived by applicant:

$q={\mathrm{\σ}}_1-\frac{{\mathrm{\πr}}^2}{A_a}{\mathrm{\σ}}_3$

In formula:

σ ₁for axial stress, unit: MPa,

A _afor test specimen round platform floorage, unit: cm ²,

R is test specimen round platform top radius, unit: cm,

σ ₃the confined pressure Zhi， unit of appointment: MPa during for triaxial test,

Calculate the shear stress of consolidation draining in cutting.

Axial stress following formula [1]～[6] in former rules calculate:

【1】 $h_c={\mathrm{<figure-callout\; id="0"\; label="h"\; filenames="131017085655.png,131017085707.png"\; state="\{\{state\}\}">h</figure-callout>}}_0\&times;{(1-\frac{\mathrm{\&Delta;V}}{V_0})}^{1/3},$

【2】 $A_c=\frac{V_0-\mathrm{\&Delta;V}}{h_c},$

【3】V _c=h _cA _c，

In formula:

H _c---the height after sample is fixed, unit: cm,

A _c---the area after sample is fixed, unit: cm ²,

V _c---the volume after sample is fixed, unit: cm ³,

H ₀---sample elemental height, unit: cm,

V ₀---sample initial volume, unit: cm ³,

Δ h _c---fixed deflection, unit: cm ²,

Δ V---consolidation draining Liang， unit: cm ³,

【4】 ${\mathrm{\&sigma;}}_1=\frac{F}{A_a},$

【5】 $A_a=\frac{V_c-\mathrm{\&Delta;}{V}_i}{h_c-\mathrm{\&Delta;}{h}_i},$

【6】h _i=h _c-Δh _i，

V _c---the volume after sample is fixed, cm ³;

Δ V _i---the volume change of sample in shear history, cm ³;

Δ h _i---the height change of sample in shear history, cm.

Compared with prior art, beneficial effect of the present invention is as follows:

By increased confined pressure sample axially on minute force parameter, the rules of having corrected prior art are not considered the carelessness of water pressure impact, and formula of the present invention corrects in rules (SL-237-017-1999) formula [14] shear stress-axial strain curve (q-ε in high confining pressure situation _a) shift to an earlier date crooked mistake.

New formula according to the present invention carries out computing to the self registering test figure of computing machine, presses shear stress-axle varied curve (q-ε _a) and press body change-axle varied curve ε _v-ε _athe critical state point obtaining (breakdown point) high conformity, is suitable for engineering application.

Accompanying drawing explanation

Below in conjunction with drawings and Examples, the invention will be further described:

Fig. 1 is shear stress-axle varied curve (q-ε of the prior art _a) and press body change-axle varied curve ε _v-ε _a.

Fig. 2 a is fixed front and fixed rear specimen size.

Sample force analysis figure when Fig. 2 b is shearing.

Fig. 3 a is the photo after bedding material confined pressure 0.6MPa off-load.

Fig. 3 b is the photo after bedding material confined pressure 1.0MPa off-load.

Fig. 3 c is the photo after bedding material confined pressure 1.6MPa off-load.

Fig. 3 d is the photo after bedding material confined pressure 2.15MPa off-load.

Fig. 4 is that the round platform of matching in computation process departs from body schematic diagram.

Fig. 5 is that half round platform in Fig. 4 departs from body.

Fig. 6 is shear stress-axle varied curve (q-ε that the present invention obtains _a) and press body change-axle varied curve ε _v-ε _a.

Fig. 7 is mean principle stress p and the graph of a relation of shear stress q within the scope of confined pressure 3MPa under the stockpile critical conditions being obtained by method of the present invention.

The graph of a relation of the logarithm that Fig. 8 is void ratio e and mean principle stress p under the stockpile critical conditions being obtained by method of the present invention within the scope of confined pressure 3MPa.

Fig. 9 is the solid derivation schematic diagram of formula in the present invention [12].

Figure 10 is the longitudinal profile derivation schematic diagram of formula in the present invention [12].

Figure 11 is the end face derivation schematic diagram of formula in the present invention [12].

Embodiment

The triaxial test curve arranging out by rules, inconsistent with the not apparition of deviatoric stress q of definition in " Advanced Soil Mechanics ".In addition, according to body, become ε _vthe constant critical state point obtaining, obviously partially after according to answering the peak point q of hump type stress-strain diagram (q-ε) to obtain critical state point.The critical state point position being obtained by stress-strain diagram and body change-strain curve is different.

Through carefully searching reason, closely related with the method for the processing triaxial consolidation Drainage Shear test figure of stipulating in current design criteria.Applicant is in carrying out the process of a large amount of large triaxial tests, launch thinking, to sample force analysis, list respectively axially and level to equilibrium of forces equation, obtained the formula 19.6.2-1 in replacement " water power hydraulic engineering earthwork test rule " SL237-017-1999 consolidated drained test, the new formula of 19.6.2-2.New formula has been corrected the mistake in former rules, can well solve stress-strain curve peak point under high confining pressure (being sample breakdown point) and the inconsistent problem of body change-strain curve peak point, according to new formula, the peak point of above two curves is all corresponding to same axle variate, thereby can be good at determining breakdown point, and then determine more accurately critical conditions Parameters of constitutive model, then in substitution finite element program, can obtain the dam deformation value of more approaching reality, overcome the deformation values problem less than normal of existing calculating.

1, the formula in " water power hydraulic engineering earthwork test rule ".

The height of fixed rear sample, area and volume in 1.1 rules.

People's Republic of China's power industry standard " water power hydraulic engineering earthwork test rule " SL237-1999 of issue on Dec 17th, 2006 has stipulated the disposal route of triaxial consolidation Drainage Shear test figure.As shown in Figure 2 a, because the shape of fixed rear sample is cylindrical substantially, so rules are by cylindrical consideration.

The planimetric map of fixed front column type sample is the abcd shown in solid line, when fixed, due to three direction pressurizeds, becomes the efgh shown in actual situation.

The 100th page of regulation of rules calculated height, area and the volume of the fixed rear actual measurement of sample by following formula [1]～[6]:

【1】 $h_c={\mathrm{<figure-callout\; id="0"\; label="h"\; filenames="131017085655.png,131017085707.png"\; state="\{\{state\}\}">h</figure-callout>}}_0\&times;{(1-\frac{\mathrm{\&Delta;V}}{V_0})}^{1/3}---(\mathrm{19.5.4}-1)$

【2】 $A_c=\frac{V_0-\mathrm{\&Delta;V}}{h_c}---(\mathrm{19.5.4}-2)$

【3】 V _c＝h _cA _c (19.5.4-3)

In formula:

H _c---the height after sample is fixed, unit: cm;

A _c---the area after sample is fixed, unit: cm ²;

V _c---the volume after sample is fixed, unit: cm ³;

H ₀---sample elemental height, unit: cm;

V ₀---sample initial volume, unit: cm ³;

Δ h _c---fixed deflection, unit: cm ²;

Δ V---consolidation draining Liang， unit: cm ³.

In rules, calculating volume after fixed and area and formula is reasonable.In the present invention, use in the same old way.

1.2, the height of sample, area and volume in shear history in rules.

When coarse-grained soil is sheared, the shape of sample more resembles cydariform, and for simplicity, rules are equal principle by volume, and cydariform sample is reduced to isopyknic cylinder, sees Fig. 2 b.Therefore, 104～105 pages of rules are calculated sample corrected area while shearing by following formula:

【4】 ${\mathrm{\&sigma;}}_1=\frac{F}{A_a}$

【5】 $A_a=\frac{V_c-{\mathrm{\&Delta;V}}_i}{h_c-{\mathrm{\&Delta;h}}_i}---(\mathrm{19.6.2}-1)$

【6】h _i=h _c-Δh _i

In formula:

V _c---the volume after sample is fixed, unit: cm ³;

Δ V _i---the volume change of sample in shear history, unit: cm ³;

Δ h _i---the height change of sample in shear history, unit: cm.

Sample corrected area A as implied above _aactual is average area, is the area of equivalent cylindrical.The power F on sample top is measured and is tried to achieve by hoop dynamometer (sensor).

As shown in Fig. 3 a～Fig. 3 d, actual sample is (can be approximately preferably round platform) of cydariform in fact, and deviation must appear in thus obtained data.

2, the new formula (symbol is got consistent with " water power hydraulic engineering earthwork test rule ") of releasing by round platform:

When the shortcoming of the formula in rules (5.1.2) is the compression of sample axially loaded, the shape of sample is no longer cylindrical, and as shown in Fig. 3 a～Fig. 3 d, sample becomes cydariform after confined pressure off-load, also relatively resembles two onesize round platforms and is buckled together.Owing to being no longer the cylinder of outer wall vertical, the σ being applied by confined pressure water ₃to produce in vertical direction axial thrust load, this power can not be ignored, and ignores this component and has caused the inaccurate of experimental result.Particularly at axle, become ε _alarger, thereby in the test of the larger high confining pressure of sample external drum.At this moment, sample is reduced to cylinder improper, for the sake of simplicity, equal principle by volume, be reduced to equate with cydariform volume of sample two isopyknic round platforms up and down.Rules are selected with sample equal-volume, contour cylinder as the disengaging body of analyzing use, and cylindrical cross-section is amassed as A _a.Therefore, applicant's area of selecting to go to the bottom is A _athe round platform at place is set up and is departed from body.The height that departs from body is h _a. round platform floorage is A _aradius is R _a; Round platform upper base radius is r, r=D (1-ε)/2, and wherein D is the upper base diameter after fixed; Round platform bus is long is l _a, lateral area is S _l.Following relational expression is set up:

[7] S _l=π l _a(r+R _a) (the long-pending formula of frustum cone side on how much books).

[8] R-r=l _asin θ (relation formula of round platform line segment on how much books).

Referring to Fig. 4, confined pressure σ ₃at axial component, be σ ₃sin θ * S _l, because sample deadweight is relatively little, in rules, ignored it, so we also ignore deadweight.Set up the balance equation of axial force:

[9] σ _1l* A _a=σ ₁* A _a+ σ ₃sin θ * π l _a(R _a+ r) applicant list vertically to equilibrium of forces formula).

σ wherein ₁it is the axial stress calculating by [4] formula in rules; σ ₃it is given confined pressure of when test; σ _1lthat round platform floorage is A _aon axial stress.

By formula [8] substitution formula [9], equal sign two ends are same divided by A _a, obtain:

【10】 ${\mathrm{\&sigma;}}_{1l}={\mathrm{\&sigma;}}_1+{\mathrm{\&sigma;}}_3\frac{\mathrm{\&pi;}{R_a}^2-{\mathrm{\&pi;r}}^2}{A_a}$ (applicant's derivation).

In fact, from knowledge of hydraulics, σ ₃act on the axial force of frustum cone side on long-pending and equal its projection on round platform is gone to the bottom.Equaling external radius is R _a, inside radius annulus area (the π R that is r _a ²-π r ²) be multiplied by σ ₃.

Due to π R _a ²=A _a, be simplified form:

【11】 ${\mathrm{\&sigma;}}_{1l}={\mathrm{\&sigma;}}_1+{\mathrm{\&sigma;}}_3-\frac{\mathrm{\&pi;}{r}^2}{A_a}{\mathrm{\&sigma;}}_3$ (applicant's derivation).

By [12] σ _3l=σ ₃.

Finally, according to the definition in " Advanced Soil Mechanics " book, shear stress q equals q=σ _1l-σ _3l, be reduced to:

【13】 $q={\mathrm{\&sigma;}}_{1l}-{\mathrm{\&sigma;}}_{3l}={\mathrm{\&sigma;}}_1-\frac{\mathrm{\&pi;}{r}^2}{A_a}{\mathrm{\&sigma;}}_3$ (applicant push away final formula).

Wherein the derivation of formula [12] is:

As shown in Figure 9, get a differential curved surface ABED on half round platform, for differential curved surface ABED, can be considered the planar trapezoidal of inclination, its area is d _s, establish it and round platform central axis OO ' angle is θ, act on making a concerted effort for dF, as shown in figure 10 on differential curved surface ABED.On frustum cone side, there is size for σ ₃pressure, σ ₃for definite value, dF is dF' at the component that is parallel to end face on round platform.

Referring to Figure 11, have:

$d_s=(r+R_a)\&times;d_{\mathrm{\&alpha;}}\&times;\frac{h_a}{\cos \mathrm{\&theta;}}\&times;\frac{1}{2}$ (how much conversion relations)

DF=σ ₃* d _s(higher mathematics knowledge)

DF'=dF * cos θ (higher mathematics knowledge).

By Figure 11, can be obtained, power dF' is dF at the component perpendicular to half round platform ACFD plane _x, be:

dF _x=dF'×sinα。(equilibrium of forces equation)

Can be obtained fom the above equation: $d{F}_x={\mathrm{\&sigma;}}_3\&times;(r+R_a)\&times;\mathrm{d\&alpha;}\&times;\frac{h_a}{\cos \mathrm{\&theta;}}\&times;\frac{1}{2}\&times;\cos \mathrm{\&theta;}\&times;\sin \mathrm{\&alpha;}$ (inventor's derivation)

So: $d{F}_x={{\&Integral;}_0^{\mathrm{\&pi;}}\mathrm{\&sigma;}}_3\&times;(r+R_a)\&times;\mathrm{d\&alpha;}\&times;\frac{h_a}{\cos \mathrm{\&theta;}}\&times;\frac{1}{2}\&times;\cos \mathrm{\&theta;}\&times;\sin \mathrm{\&alpha;}$ (inventor's derivation)

Abbreviation obtains: $d{F}_x={{\&Integral;}_0^{\mathrm{\&pi;}}\mathrm{\&sigma;}}_3\&times;(r+R_a)\&times;\mathrm{d\&alpha;}\&times;h_a\&times;\frac{1}{2}\&times;\sin \mathrm{\&alpha;}$ (inventor's derivation)

$=\frac{{\mathrm{\&sigma;}}_3\&times;(r+R_a)\&times;h_a}{2}{\&Integral;}_0^{\mathrm{\&pi;}}\sin \mathrm{\&alpha;d\&alpha;}$ (inventor's derivation)

And ${\&Integral;}_0^{\mathrm{\&pi;}}\sin \mathrm{\&alpha;d\&alpha;}=(-\cos \mathrm{\&pi;})-(-\cos 0)=\left(1\right)-(-1)=2$ (higher mathematics integral formula)

? $F_x={\mathrm{\&sigma;}}_3\&times;\frac{(2r+{2R}_a)}{2}\&times;h_a={\mathrm{\&sigma;}}_3\&times;S_{\mathrm{ACFD}}$ (inventor's derivation).

In half round platform ACFD plane, effect has size for σ _3lpressure, σ _3lfor definite value, what it produced in half round platform ACFD plane makes a concerted effort for F _l, have:

F _l=σ _3l* S _aCFD(equilibrium of forces equation)

Level can obtain to row equilibrium of forces equation:

F _l=F _x(equilibrium of forces equation)

So have: σ _3l=σ ₃(inventor push away result).

And in rules, the shear stress formula of consolidation draining in cutting is formula [14]:

【14】 q=σ ₁-σ ₃。

Applicant push away formula [13] and former rules [14] in, σ ₁by axial stress that formula [4]-[6] obtain in former rules; σ ₃the confined pressure value of appointment while being large triaxial test.

Below, applicant push away new formula [13] and the large triaxial test data of the dam material that is all used for having processed Shuibuya Dam of the formula [14] in former rules, thereby which can be offered an explanation out, be rational.

3, the stress-strain diagram of water cloth a strip of land between hills face dam large triaxial test.

3.1 material behavior.

The Shuibuya Concrete Face Rockfill Dam of height of dam 233m is the current high dam in built similar dam type in the world, the highest rock---Mexico Ah melon Mill handkerchief dam exceeds 46m than built in the world, than China built the highest rock---Tianshengqiao-I rock exceeds 55m.Engineering characteristic at heavily stressed lower dam filler is the key issue that is related to Dam Construction success or not.

Test material adopts Mao Kou group limestone stockpile, and its physical property is: proportion 2.73, sillar density 2.69g/cm ³, saturated water absorption 0.76%, ultimate compression strength 68.1MPa when saturated, dry state ultimate compression strength 87.3MPa, coefficient of softing 0.78.Fig. 6 is the on-the-spot feeding in stock ground.

Triaxial test fundamental property index: sample preparation dry density 2.18g/cm ³, each grating accounts for the number percent of sample general assembly (TW): 60～40mm20%, 40～20mm25.6%, 20～10mm18.4%, 10～5mm16%, 5～2mm12%, 2～1mm3%, 1～0.5mm3%, 0.5～0mm2%.Applicant leads project team member to complete 23 samples.In order clearly to see trial curve clearly, therefrom selected representational 5 to be drawn in Fig. 6.Wherein zero ◇ of the △ on transverse axis+* representative is pressed new formula [13], data and curve that the raw data of test computer record is calculated; Black dotted lines represents data and the curve raw data of computer record being calculated by formula in rules.

As seen from Figure 6, the curve that new formula [13] obtains, the critical state point that the critical state point obtaining by shear stress maximal value (breakdown point) obtains when becoming constant by body has good consistance.And formula [14] in rules, curve (black dotted lines) is bent downwardly in advance, and the critical state point obtaining by shear stress maximal value obviously shifts to an earlier date, and is not same position with becoming the constant critical state point obtaining by body.

According to the data in new formula [13], obtained the critical conditions characteristic of stockpile:

Conclusion 1:23 large triaxial consolidation Drainage Shear test figure shows: under stockpile critical conditions, mean principle stress p and shear stress q are linear relations within the scope of confined pressure 3MPa.Referring to Fig. 7.

Conclusion 2:23 large triaxial consolidation Drainage Shear test figure shows: under stockpile critical conditions, the logarithm of void ratio e and mean principle stress p is linear relation within the scope of confined pressure 3MPa.Referring to Fig. 8.

4, conclusion

New formula [13] has been introduced the axial thrust load parameter of confined pressure at sample, corrected former testing regulations and do not considered the carelessness of water confined pressure impact, new formula corrects in rules (SL-237-017-1999) formula [14] shear stress-axial strain curve (q-ε in high confining pressure test _a) shift to an earlier date crooked mistake.

According to new formula, the self registering test figure of computing machine is carried out to computing, press shear stress-axle varied curve (q-ε _a) and press body change-axle varied curve ε _v-ε _athe critical state point obtaining (breakdown point) high conformity, is suitable for Practical.

According to new formula [13], can obtain correct trial curve, and then arrange constitutive parameter more accurately and carry out dimensional Finite Element, can predict more accurately distortion and the stress of 300 meter level rock-fill dams.

5, experimental procedure of the present invention is standard test step of the prior art, is specially:

The operating process of coarse-grained soil triaxial test:

One, dress sample (soil sample height 60cm)

1, each group five etc. is distributed into and is mixed in sample container; Scuppit uniform mixing, records the watering can water yield before watering;

2, two metafiltration paper have not been forgotten to put on base; High confining pressure test is to hold 1.1 meters of mould cylinder liners long, 0.9 meter high above plastic-blasting cloth.

3, each soil sample is packed into and held in mould cylinder, with bar reinforcement, smash periphery, make pore filling fine grained.

4, above soil sample, put two layers of filter paper;

5, put pressure head well, pressure head and high-voltage tube connect together, and check that whether interface is loosening, in case leak and cause test failure in test.

(points for attention: while using surface vibrator, hold up for 4, prevent from holding mould bucket and topple over, or beneath car wheel is overstepped the limit.）

Two, sample is degassed

1, first first Ya Hexia hole, upper hole pressure passageway water is rinsed, then connect the pipe on pressure head, connect lower sensor for pore water pressure, start degassed.

(points for attention: the little rubber circle on base can not fall, have fallen and can leak gas, and renew at every turn);

2, first turn on the power switch, then open vacuum pump, open degassed valve, degassed valve, distribution valve, upper pore pressure valve and make sample degassed, press while showing negative pressure in hole instantly, pulls down and hold mould cylinder.

Points for attention: exhaust vacuum and will first close each valve on triaxial apparatus, and then stop vacuum pump.

The water filling of San, pressure chamber

1, each parameter (load, confined pressure, hole pressure, back-pressure) zeroing;

2, push assigned address after sample is installed, connect confined pressure sensor, lower hole presses sensing to connect, connect confined pressure pipe, lower pore pressure pipe;

3, open confined pressure valve, tap into water pipe, turn on pressure chamber's vent port, open tap water (confined pressure pipe) switch, then open water intaking valve and start water filling.

When 4 ,Dang pressure chamber vent ports start spilling water, water filling completes.First close running water switch, then close water intaking valve, tighten pressure chamber's vent port.

Four, natural saturation method

1, remove pore pressure pipe, hole is pressed and be connected with drainpipe;

2, open water knockout feed water valve, and limit, pond de aerated water halter, for degassing tank is filled with water.Then close degassing tank feed water valve;

3, before saturated, open computer, recording body becomes pipe reading;

4, open lower pore pressure valve, saturated valve, connection valve, connection valve, start saturated.

Points for attention: the standard that sample is saturated is to see whether drainpipe water discharges continuously, and calculates the turnover water yield and pore-body accumulated amount.

Five, sample is fixed

1,, after saturated end, close saturated valve, lower pore pressure valve, upper pore pressure valve.Remove the drainpipe that hole presses face, change pore pressure pipe;

2, open backpressure valve, connection valve 2, saturated valve, make back-pressure tank water 1000ml left and right;

3, on triaxial apparatus, open pore pressure valve, confined pressure valve, distribution valve 1, backpressure valve;

4, regulate crossbeam liter, first open oil sources, reference system pressure table of comparisons regulating system pressure;

5, carry out the operation on computer, first oil cylinder displacement is mentioned to 58mm;

6, crossbeam falls, and contacts (not forgetting) with sample upper piston;

7, " test type ", " parameter setting ", " controlling test " are set;

8, side direction control mode is selected with " confined pressure control ", establishes " speed ", " confined pressure maintenance target " (then clicking " determining " button), (desirable 0.05～0.1MPa/ minute).

Click " equidistantly storing data " in " data management ", and " figure is opened " button, " determining " button at click confined pressure place;

9, body becomes without zero clearing, starts fixed;

10, software judge consolidation time to or stabilized reference to (constancy of volume), point out fixed end,

Click " figure pass " button in " figure output ",

Click " storage finishes " button in " data management ",

Click " storage curve " button in " figure output ", saved as consolidation curve.

Points for attention: want contradistinction system pressure table of comparisons regulating system pressure before shearing.

Six, sample is sheared

Deformation-sensor is installed and to good initial position (showing that 1～2mm is best), load is selected to stepping and zero clearing.

The shear test that A, confined pressure remain unchanged

1,, before shearing and starting, check whether back to zero of side direction water vat piston;

2, regulate crossbeam position, crossbeam is contacted with sample, load change is within 10;

3, axially control mode is selected " Deformation control ", input " speed " and " distortion keeps target " value.

(desirable 0.5mm/ minute, 150mm);

4, click " equidistantly storage " button in " data management ";

5, " determining " button of clicking confined pressure place just starts to have sheared, and opening pore pressure valve, distribution valve, backpressure valve is Drainage Shear;

6, sheared " figure pass " button in rear click " figure output ",

Click " storage finishes " button in " data management ",

Click " storage curve " button in " figure output ", saved as shearing curve.

Seven, unloading

1, close two valves on base;

2, axially control mode is selected " axial translation control ", input 1mm/ minute, and " displacement maintenance target " is made as zero;

3, unloading confined pressure, selects with " confined pressure control ", establishes " speed ", " confined pressure maintenance target " (being made as zero);

When 4, axial displacement drops to 50 left and right, turn on pressure chamber's vent port, start draining;

5, shutdown system pressure, takes off shaft position sensor;

6 ,Jiang pressure chambers are pushed into Hoisting Position, pull down confined pressure, hole pressure, back-pressure pressure transducer, and the pressure head of slinging supports with bamboo clappers, removes fastening bolt, unloads pressure chamber, loads onto porous disc hoisting ring, and porous disc is hung out together with sample, rinses base and pipeline.

7, exit software systems, close electrical control cubicles power supply, shut down computer, the power supply of leaving behind.

Points for attention

System in test run, when the pressure of hydraulic power source do not reduce to zero or stop before, must not close Mersure Controler, otherwise will make actuator generation out of control impact, parts or test specimen are damaged.

Claims (2)

1. a coarse-grained soil large triaxial test data critical conditions parameter determination method under high confining pressure, is characterized in that comprising the following steps:

One, coarse-grained soil specimen being put into triaxial consolidation Drainage Shear test unit tests;

Two, obtain in test data;

Three, by formula:

calculate the shear stress of consolidation draining in cutting,

In formula:

σ ₁for axial stress, unit: MPa,

A _afor test specimen round platform floorage, unit: cm ²,

R is test specimen round platform top radius, unit: cm,

σ ₃the confined pressure Zhi， unit of appointment: MPa during for triaxial test,

This new formula

replaced the formula q=σ in former rules ₁-σ ₃.

2. coarse-grained soil large triaxial test data critical conditions parameter determination method under a kind of high confining pressure according to claim 1, is characterized in that:

Axial stress following formula [1]～[6] in former rules calculate:

【1】 $h_c=h_0\&times;{(1-\frac{\mathrm{\&Delta;V}}{V_0})}^{1/3},$

【2】 $A_c=\frac{V_0-\mathrm{\&Delta;V}}{h_c},$

【3】V _c=h _cA _c，

In formula:

H _c---the height after sample is fixed, unit: cm,

A _c---the area after sample is fixed, unit: cm ²,

V _c---the volume after sample is fixed, unit: cm ³,

H ₀---sample elemental height, cm,

V ₀---sample initial volume, unit: cm ³,

Δ h _c---fixed deflection, unit: cm ²,

Δ V---consolidation draining Liang， unit: cm ³.

【4】 ${\mathrm{\&sigma;}}_1=\frac{F}{A_a},$

【5】 $A_a=\frac{V_c-{\mathrm{\&Delta;V}}_i}{h_c-{\mathrm{\&Delta;h}}_i},$

【6】h _i=h _c-Δh _i，

V _c---the volume after sample is fixed, unit: cm ³;

Δ V _i---the volume change of sample in shear history, unit: cm ³;

Δ h _i---the height change of sample in shear history, unit: cm.

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