CN110185070A - Oblique Steep Slope Bridge vertical bearing capacity correction factor and bearing capacity computation method - Google Patents
Oblique Steep Slope Bridge vertical bearing capacity correction factor and bearing capacity computation method Download PDFInfo
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Abstract
The invention discloses a kind of oblique Steep Slope Bridge vertical bearing capacity correction factor and bearing capacity computation methods, first the Pile Bearing Capacity disturbance degree α under calculating different gradientv,Then the Pile Bearing Capacity disturbance degree α obtained according to step 1vCalculate pile foundation side friction reduction coefficient ζv, ζv=1- αv.After obtained bearing capacity will be calculated multiplied by the correction factor, Vertical Bearing Capacity of Pile Foundation is more nearly oblique abrupt slope area Bored Pile of Bridge actual carrying capacity, avoids the incidence of engineering accident.After considering the correction factor, oblique Steep Slope Bridge Vertical Bearing Capacity of Pile Foundation is more accurate, and the precision of design can be improved in Design of Foundation, reduces uncertain factor bring design alteration in engineering.After correction factor, Design of Foundation is more nearly actual value, reduces waste of material, reduces pile foundation construction cost.
Description
Technical field
The invention belongs to civil engineering Bridge Design and technical field of construction, and in particular to oblique Steep Slope Bridge pile foundation vertical is held
Carry power correction factor and bearing capacity computation method.
Background technique
As highway industry continues to develop, bridge acts on increasingly significant in highway construction, and Bored Pile of Bridge is bridge
One of main base form in beam engineering.Bridge upper load is transferred in ground by pile foundation, Bored Pile of Bridge carrying
Power is mainly provided by pile side friction and end resistance jointly, and Pile Bearing Capacity shares how much being divided into according to its pile side friction
Friction pile and end-bearing pile.When Pile Bearing Capacity is mainly provided by pile side friction, it is called Piles for Friction Piles basis at this time, when
When Pile Bearing Capacity is mainly provided by end resistance, it is called end-bearing pile.It is most of profound in existing highway Bored Pile of Bridge
Pile foundation is based on friction pile, and for friction pile, its side friction mainly passes through pile body side surface area and stake week Rock And Soil phase interaction
With pile foundation can generate a downtrend relative to pile peripheral earth since pile top load is acted on, and pile foundation is by stake Zhou Yan
The soil body provide upward side friction come support pile foundation bear upper load.
For its pile side friction of plane earth's surface Bored Pile of Bridge in the form of pile center's axis is centrosymmetric, between each other
Deng mutually balancing greatly, the bearing capacity of pile foundation is perfect mistake at this time, and bearing capacity is according to Road Bridge Pile Foundation plinth
Handbook and relevant design proper calculation, according further to engineering practical experience pile foundation, there are also the calculating of its Correlation
Bearing capacity, all in all its theoretical comparative maturity in terms of the Bored Pile of Bridge bearing capacity calculation of level land.
Highway bridge continues to develop in recent years, and the oblique Steep Slope Bridge construction in mountain area is gradually spread out, and oblique steep slope region constructs a bridge
Pile foundation construction, design, in terms of it is more complicated than plane Bored Pile of Bridge, as shown in Figure 1, due to oblique steep hillslope
Section free face 1 presence, 2 pile side friction of pile foundation cannot be effectively played, under identical pile foundation buried depth, level land stake side
4 soil body of Rock And Soil is complete, presence of the oblique steep slope region Bored Pile of Bridge in mountain area due to oblique abrupt slope 3, soil body missing on the outside of free face,
Then Rock And Soil side friction in stake side is low compared to level land pile foundation, and Pile Bearing Capacity can be carried relative to plane pile foundation at this time
Power reduces, and at present there is no dedicated calculation Bearing Capacity Theory formula is provided for oblique Steep Slope Bridge pile foundation, still using flat
Face Vertical Bearing Capacity of Pile Foundation calculation formula.Pile foundation includes two kinds, and one is friction piles, and one is embedded rock piles.
(1) the plane Vertical Bearing Capacity of Pile Foundation [R of friction pilea1] calculation formula is as follows:
(2) the plane Vertical Bearing Capacity of Pile Foundation [R of embedded rock pilea2] calculation formula is as follows:
But this level land Bored Pile of Bridge Ultimate Strength formula is used to calculate the oblique Steep Slope Bridge pile foundation limit
Bearing capacity, bearing capacity are not conform to actual, and the theoretical value that Bored Pile of Bridge bearing capacity formula acquires by the level land is deposited
In following disadvantage:
(1) calculated value found out is higher than actual bearer ability, reduces oblique Steep Slope Bridge Pile Bearing Capacity safety coefficient,
Easily cause traffic accident.
(2) difficulty is brought to Bored Pile of Bridge design, carrying is acquired according to the calculating of traditional Pile Bearing Capacity calculation formula
Power is higher, none relatively accurate bearing capacity value, is not easy to pile foundation during Bored Pile of Bridge Design of Bearing Capacity and sets
Meter.
(3) it is be easy to cause the waste of material, increases design and construction cost.It is calculated in the design according to general equation
Bearing capacity ratio is actual big, then big how much none relatively accurate value actually, then designer then can be for safety by stake
Key dimension, arrangement of reinforcement etc. blindly increase (may actually have more than is needed so much material), and engineering cost is be easy to cause to increase.
Summary of the invention
To solve the above-mentioned problems, the present invention provides oblique Steep Slope Bridge vertical bearing capacity correction factor and bearing capacities
Calculation method more accurately calculates Bored Pile of Bridge bearing capacity.
In order to achieve the above objectives, the calculation method of oblique Steep Slope Bridge vertical bearing capacity correction factor, including following step
It is rapid:
Pile Bearing Capacity disturbance degree α under step 1, calculating different gradientv,In formula, P0For identical work
Flat slope pile foundation ultimate vertical bearing capacity under condition, P indicate the pile foundation vertical ultimate bearing capacity of certain gradient；
Step 2, the Pile Bearing Capacity disturbance degree α obtained according to step 1vCalculate pile foundation side friction reduction coefficient ζv, ζv
=1- αv。
Further, in step 1, by testing under vertical uniform load q, the long friction pile of piles with different is measured in difference
Pile foundation vertical ultimate bearing capacity P under the gradient, when the gradient is 0 ° with the long friction pile of stake in flat slope pile foundation vertical limit
Bearing capacity P0。
Further, taking displacement at pile top is the corresponding load of 1.5mm as Ultimate Bearing Capacity of Pile Foundation P.
Further, in step 1, n gradient X is measuredjUnder pile foundation vertical ultimate bearing capacity Pj, 0≤j≤n-1, n >=2,
And calculate the reduction coefficient ζ under the gradientvj, when gradient X is in Xj~Xj+1Between when, pile foundation vertical ultimate bearing capacity ζv=ζvj+
k(Pj+1-Pj), k=(Xj+1-Xj)/(ζvj+1-ζvj)。
Further, n=6, the measurement gradient are 0 °, 30 °, 45 °, 60 °, 75 ° and 90 °.
A kind of oblique Steep Slope Bridge vertical bearing capacity calculation method, the oblique Steep Slope Bridge bearing capacity of pile foundation [R of friction pilea1]
Calculation formula are as follows:The oblique Steep Slope Bridge stake of embedded rock pile
Base bearing capacity [Ra2] calculation formula are as follows:In above formula, pile foundation side
Frictional resistance reduction coefficient ζvIt obtains according to the method for claim 1, [Ra1]-friction pile single-pile vertical orientation compression bearing holds
Perhaps it is worth, [Ra2]-embedded rock pile single-pile vertical orientation compression bearing feasible value；U-pile body perimeter；Ap- stake end section area；N-soil
The number of plies；li- each the thickness of the layer；qik- and liThe frictional resistance standard value of corresponding each soil layer and stake side；[fa0At]-stake end
The basic feasible value of bearing capacity of soil；H-stake end buried depth；k2- allowable bearing with depth correction factor；γ2- stake
The above each soil layer in end is weighted and averaged severe；λ-correction factor；m0- clear bottom coefficient；c1- end resistance mobilization factor；frk- stake
Hold rock saturation uniaxial compressive strength standard value；c2iThe side of-the i-th layer of rock stratum hinders mobilization factor；hi- stake is embedded in each rock stratum part
Thickness；M-rock stratum the number of plies；ζsThe collateral resistance mobilization factor of-coating soil.
Compared with prior art, the present invention at least has technical effect beneficial below: the present invention is by setting oblique abrupt slope
Bored Pile of Bridge vertical bearing capacity correction factor, and by capacity correct coefficient and bearing capacity disturbance degree αvEstablish connection, shadow
Loudness can be calculated by comparing simply calculating, and bearing capacity amendment is found out and then the disturbance degree found out
Coefficient；By two methods of model test and numerical simulation find out different gradient and stake it is long under Pile Bearing Capacity amendment system
Number, it is almost the same that two methods acquire its correction factor, Bored Pile of Bridge bearing capacity can be made more objective and accurate, more adjunction
It is close practical.
Further, taking displacement at pile top to be the corresponding load of 1.5mm as Ultimate Bearing Capacity of Pile Foundation P, 1.5mm is industry
Relatively approve and be more conform with actual in inside.
Further, in step 1, n gradient X is measuredjUnder pile foundation vertical ultimate bearing capacity Pj, 0≤j≤n-1, n >=2,
And calculate the reduction coefficient ζ under the gradientvj, when gradient X is in Xj~Xj+1Between when, pile foundation vertical ultimate bearing capacity ζv=ζvj+
k(Pj+1-Pj), k=(Xj+1-Xj)/(ζvj+1-ζvj), it does not need to carry out a large amount of DATA REASONING, can easily calculate different slopes
Pile foundation vertical ultimate bearing capacity under degree.
Further, due to close in 0-30 ° of this section pile foundation vertical ultimate bearing capacity variation tendency, the gradient is greater than
At 30 °, the variation of pile foundation vertical ultimate bearing capacity is more obvious, so taking n=6, the measurement gradient is 0 °, 30 °, 45 °, 60 °, 75 °
And 90 °.
A kind of oblique Steep Slope Bridge vertical bearing capacity calculation method in mountain area, will calculate obtained bearing capacity and repairs multiplied by this
After positive coefficient, Vertical Bearing Capacity of Pile Foundation is more nearly oblique abrupt slope area Bored Pile of Bridge actual carrying capacity, avoids engineering thing
Therefore incidence.After considering the correction factor, oblique Steep Slope Bridge Vertical Bearing Capacity of Pile Foundation is more accurate, in Design of Foundation
In the precision of design can be improved, reduce uncertain factor bring design alteration in engineering.After correction factor, stake
Basic engineering is more nearly actual value, reduces waste of material, reduces pile foundation construction cost.
Detailed description of the invention
Fig. 1 a is oblique abrupt slope pile foundation schematic diagram；
Fig. 1 b is level land pile foundation schematic diagram；
The stake that Fig. 2 a is long 40cm is with the P-S of oblique abrupt slope slope changeVCurve；
The stake that Fig. 2 b is long 60cm is with the P-S of oblique abrupt slope slope changeVCurve；
The stake that Fig. 2 c is long 80cm is with the P-S of oblique abrupt slope slope changeVCurve；
The stake that Fig. 2 d is long 100cm is with the P-S of oblique abrupt slope slope changeVCurve；
Fig. 3 is influence schematic diagram of the degree variation to bearing capacity of pile foundation；
Fig. 4 is slope change to bearing capacity of pile foundation disturbance degree αVInfluence schematic diagram；
Fig. 5 a is oblique abrupt slope pile foundation FEM calculation geometrical model；
The oblique abrupt slope pile foundation limited element calculation model grid dividing sectional view that Fig. 5 b is 45 °.
In attached drawing: 1, free face, 2, pile foundation, 3, the oblique abrupt slope of massif, 4, level land stake side Rock And Soil.
Specific embodiment
The following describes the present invention in detail with reference to the accompanying drawings and specific embodiments.
1. Pile Bearing Capacity reduction coefficient proposes
Pile side friction is substantially the shear problem of Pile side soil, and the shearing of Pile side soil limit frictional resistance value and Pile side soil is strong
It spends related, increases with the increase of soil classifiction.And soil classifiction depend on its classification, property, state and
Normal stress on shear surface.The Pile side soil of different classes of, property, state and depth will be with different pile side frictions.
Oblique Steep Slope Bridge pile foundation Pile side soil makes slopes pile foundation two since missing within the scope of the certain depth of side or pile peripheral earth intensity are insufficient
Frictional resistance suffered by frictional resistance suffered by side and level land pile foundation has certain difference, to the routinely level land stake design of oblique Steep Slope Bridge pile foundation
Obviously be not suitable for, therefore, to oblique Steep Slope Bridge pile foundation in design, its bearing capacity should be reduced, to ensure that pile foundation carries
Power meets requirement.
Pile foundation side friction reduction coefficient ζvCalculation formula it is as follows:
ζvReduction coefficient under-certain ratio of slope；
f1- close to massif side pile friction value；
f2- outside pile foundation side friction value.
Pile Bearing Capacity disturbance degree αvCalculation formula is as follows:
In formula: P0Indicate that corresponding flat slope pile foundation ultimate vertical bearing capacity/axle power/frictional resistance, P indicate the stake of certain gradient
Base ultimate vertical bearing capacity/axle power/frictional resistance, works as P0Indicate corresponding flat slope pile foundation ultimate vertical bearing capacity/when, P is indicated
The pile foundation vertical ultimate bearing capacity of certain gradient；Work as P0When indicating corresponding flat slope pile foundation vertical limit axle power, P indicates certain gradient
Pile foundation vertical ultimate bearing capacity/axle power/frictional resistance；Work as P0When indicating corresponding flat slope pile foundation vertical limit frictional resistance, P table
Show pile foundation vertical ultimate bearing capacity/axle power/frictional resistance of certain gradient,.
To application referring herein to pile side friction indicate that Pile Bearing Capacity disturbance degree then corresponds to formula are as follows:
The P in pile side friction0It is equivalent to 2f1, P is equivalent to f1+f2, then relevant variable is substituted into disturbance degree at this time and calculated
Formula obtains:
It is not easy to calculate when as can be seen from the above equation directly calculating Pile Bearing Capacity reduction coefficient, but meter can be passed through
Its bearing capacity disturbance degree is calculated, finds out reduction coefficient indirectly.
Its Pile Bearing Capacity calculation formula after consideration Pile Bearing Capacity reduction coefficient, is held using oblique Steep Slope Bridge pile foundation
It is as follows to carry power calculation formula:
(1) rub pile vertical carrying capacity [Ra1] calculation formula is as follows:
(2) Vertical Bearing Capacity of Rock-socketed Pile [Ra2] calculation formula is as follows:
In formula:
ζv- pile foundation side friction reduction coefficient；
[Ra1]-friction pile single-pile vertical orientation compression bearing feasible value (kN), [Ra2The compression of]-embedded rock pile single-pile vertical orientation is held
It carries power feasible value (kN), the difference of pile body self weight and displacement soil weight (when self weight is included in buoyancy, replaces soil weight and be also included in buoyancy)
Consider as load；
U-pile body perimeter (m)；
Ap- stake end section area (m2), for club-footed pile, take base expanding and base expanding area of section；
N-soil number of plies；
li- each the thickness of the layer (m)；
qik- and liThe frictional resistance standard value (kPa) of corresponding each soil layer and stake side, can be according to 1 value of table；
[fa0The basic feasible value of bearing capacity (kPa) of soil, the value are generally provided by design data at]-stake end；
H-stake end buried depth (m), for there is the pile foundation washed away, buried depth is started by general scour line；Nothing is washed away
Pile foundation, buried depth are counted by ground line after natively upper thread or practical excavation；The calculated value of h is not more than 40m, when being greater than 40m, presses
It is calculated according to 40m；
k2- allowable bearing is chosen according to supporting course great soil group at stake end according to table 2 with the correction factor of depth；
γ2It is more than-stake end that each soil layer is weighted and averaged severe (kN/m3)；
λ-correction factor is selected according to table 3；
m0- clear bottom coefficient, is selected according to table 4；
c1- end resistance the mobilization factor depending on the factors such as borehole cleaning situation, catalase degree is used according to table 5；
frk- stake end rock saturation uniaxial compressive strength standard value (kPa), clay matter rock take natural moisture uniaxial compressive strong
Standard value is spent, f is worked asrkIt is calculated when less than 2MPa according to friction pile；frkiFor i-th layer of frkValue；
c2iThe side of-i-th layer of rock stratum depending on the factors such as borehole cleaning situation, catalase degree hinders mobilization factor, according to
Table 1.5 uses；
hi- stake is embedded in the thickness (m) of each rock stratum part, does not include severely-weathered layer and completely decomposed layer；
M-rock stratum the number of plies does not include severely-weathered layer and completely decomposed layer；
ζsThe collateral resistance mobilization factor of-coating soil, according to stake end frkIt determines: as 2MPa≤frkWhen < 15MPa, ζs=
0.8；As 15MPa≤frkWhen < 30MPa, ζs=0.5；Work as frkWhen > 30MPa, ζs=0.2；
1 pile side friction standard value q of tableik
2 bearing capacity of foundation slab width adjusting for depth coefficient k of table1、k2
3 correction factor λ value of table
The clear bottom Coefficient m of table 40Value
| t/d | 0.3~0.1 |
| m0 | 0.7~1.0 |
Note: 1.t, d are the diameter of sediment of the hole bottom thickness and stake.
When 2.d≤1.5m, t≤300mm；When d > 1.5m, t≤500mm, and 0.1 < t/d < 0.3.
5 coefficient c of table1、c2Value
| Lithosphere situation | c1 | c2 |
| Completely, more complete | 0.6 | 0.05 |
| It is relatively broken | 0.5 | 0.04 |
| It is broken, smashed to pieces | 0.4 | 0.03 |
2 Pile Bearing Capacity reduction coefficients solve
Can be seen that oblique abrupt slope Pile Bearing Capacity and level land Bored Pile of Bridge bearing capacity by above-mentioned analysis is to have difference
, therefore ask its bearing capacity reducing coefficient can be convenient and calculate pile foundation in the actual carrying capacity in oblique abrupt slope area.Design is tiltedly steep
Slope Bored Pile of Bridge model test finds out its Pile Bearing Capacity disturbance degree, and then is found out under its different gradient according to formula 1-3
Bored Pile of Bridge reduction coefficient.
Analysis of experiments scheme under 2.1 vertical uniform load qs
It is oblique using indoor model test to the vertical location deployment analysis of different gradient, the long pile foundation of piles with different
Abrupt slope area Bored Pile of Bridge design bearing capacity, which rationally determines, provides scientific basis.Testing program is as follows:
(1) slope change is to the deformation characteristic of Bored Pile of Bridge and the impact analysis of load transfer mechanism
The gradient: 0 °, 30 °, 45 °, 60 °, 75 °, 90 °；
(2) the long variation of stake is to the deformation characteristic of Bored Pile of Bridge and the impact analysis of load transfer mechanism
It is long that 4 stakes are designed under above-mentioned each gradient, are respectively as follows: 40cm, 60cm, 80cm, 100cm.
2.2 test results and analysis
Oblique impact analysis of the abrupt slope slope change to Vertical Bearing Capacity of Pile Foundation, same stake are grown in different gradient pile foundation
P-Sv curvilinear motion rule is as shown in Fig. 2 a to Fig. 2 d.It can be seen that under identical vertical uniform load q from Fig. 2 a to Fig. 2 d,
With displacement at pile top Sv of the stake under long as oblique abrupt slope gradient increase is gradually increased.
Taking displacement at pile top is the corresponding load of 1.5mm as Ultimate Bearing Capacity of Pile Foundation P, and different gradient, piles with different are grown
Bearing capacity calculation achievement is shown in Table the ultimate bearing capacity of 6-different gradients.Wherein αvFor bearing capacity disturbance degree,Wherein
P0Indicate that corresponding flat slope pile foundation ultimate vertical bearing capacity, P indicate the Vertical Bearing Capacity of Pile Foundation of any gradient.
Table 6
Fig. 3 and Fig. 4 is slope change to bearing capacity of pile foundation and disturbance degree αVInfluence variation.It can from table 6, Fig. 3 and Fig. 4
To find out:
Piles with different is long, and it can be approximately constant that the same gradient, which changes less pile bearing capacity disturbance degree,.Such as in 60 ° of gradients
When, it is 18.76%, 18.43%, 17.97%, 17.66% that the disturbance degree in 40cm, 60cm, 80cm, 100cm is grown in stake.
With the increase of the gradient, the ultimate bearing capacity of the same long oblique abrupt slope pile foundation of stake is on a declining curve, is 30 ° in the gradient
When, Ultimate Bearing Capacity is compared with the depression of bearing force 6% or so of flat slope pile foundation, and relatively other gradients, ultimate bearing capacity is by the gradient
Variation influences minimum, and depression of bearing force is little；When the gradient is 45 °, 60 °, 75 °, Ultimate Bearing Capacity is compared with flat slope pile foundation
Depression of bearing force is followed successively by 10%, 18%, 23% or so, and bearing capacity reduces degree and significantly increases；When the gradient is 90 °, pile foundation
Depression of bearing force 27% or so of the ultimate bearing capacity compared with flat slope pile foundation, ultimate bearing capacity decline maximum.
With the disturbance degree α of its bearing capacity of the increase of the gradientVIncrease, by taking 60cm long as an example, is arrived for 30 ° in the oblique abrupt slope gradient
In 90 ° of change procedure, disturbance degree rises to 27.62% from 6.32%, illustrates that the increase of the gradient changes the biography of pile side resistance
Effect is passed, so that bearing capacity of pile foundation has different degrees of reduction with the increase of the gradient.With the increase of the gradient, ultimate bearing
Power is influenced bigger by the gradient, analysis shows, in oblique abrupt slope area, the design of bridge pile foundation should fully consider the oblique abrupt slope gradient above
Influence.
Ultimate bearing capacity increases the bearing capacity reducing coefficient ζ compared with flat slope with the gradientV(ζV=1- αV) variation, it is shown in Table 7.
Table 7 with slope change reduction coefficient
Table 7 can be seen that the increase with the gradient, be in decreasing trend, slope with bearing capacity of pile foundation reduction coefficient of stake when long
For degree in 0 ° and 30 ° variation, it is little that bearing capacity reducing coefficient reduces degree；When the gradient is greater than 30 °, it is bright that bearing capacity reduces degree
Aobvious to increase, when the gradient is 90 °, reduction is only 73% or so of level land stake.
The verifying of 3 Pile Bearing Capacity reduction coefficients
Described previously for the oblique abrupt slope area Bored Pile of Bridge vertical bearing capacity reduction coefficient in mountain area by establishing indoor model examination
It tests, propose and has solved the oblique Steep Slope Bridge Pile Bearing Capacity reduction coefficient of different gradient, and illustrate it and solved
Journey, but whether the reduction coefficient and oblique abrupt slope pile foundation bearing capacity in Practical Project are consistent, need further to verify.Therefore
On the basis of being familiar with investigation field engineering property condition, Numerical Simulation Analysis model is established, is held by what analogue simulation obtained
It carries power and compares with the bearing capacity for considering that reduction coefficient obtains, to prove the reliability of the reduction coefficient.
4 are directed to the reduction coefficient for the gradient not measured, are obtained by following two mode.
First is that changing the gradient, and above-mentioned test process is repeated, obtains the reduction coefficient under the gradient；Second is that according to having surveyed
The reduction coefficient of the gradient needed for the reduction coefficient of the different gradient measured calculates.Calculating process is as follows: setting n that measurement obtains
Gradient XjUnder pile foundation vertical ultimate bearing capacity be Pj, 0≤j≤n-1, n >=2, according to PjCalculate the reduction coefficient under the gradient
ζvj, when gradient X is in Xj~Xj+1Between when, pile foundation vertical ultimate bearing capacity ζv=ζvj+k(Pj+1-Pj), k=(Xj+1-Xj)/
(ζvj+1-ζvj)。
3.1 model foundation
(1) geometrical model and dividing elements
In conjunction with the characteristics of pile foundation structure stress and requirement of the FEM calculation to computing resource, by a large amount of tentative calculations, really
It is scheduled on and calculates the stake diameter range that Lateral and the stake bed rock soil body take 10 times, the geometrical model of oblique abrupt slope pile foundation is as shown in Figure 5 a.
A variety of computing unit types are provided in Marc Nonlinear Finite metaprogram, it is contemplated that the needs of research select eight nodes, six face
Body unit carries out grid dividing, and when by entity discreteness at finite element unit, encryption bridge pile foundation and its surrounding as far as possible is native
Body unit not only can ensure that computational accuracy, but also be easy to restrain to thin transition by close in this way, save operation time from the near to the remote.
Most close mono- unit of 0.2m, mono- unit of maximum 2m, limited element calculation model are as shown in Figure 5 b.
(2) boundary condition determines
Computation model is approximately the unlimited body of half space, for computation model boundary condition, by model lower part bottom surface and side
X, Y, Z-direction displacement fix, to stake top apply classification load, 500kN level-one.
(3) constitutive model is chosen
Finite element numerical computational solution precision depends primarily on the reasonability of constitutive model and the accuracy of calculating parameter.This
It studies Bridge piling strtucture and uses concrete material, use perfect elasticity constitutive model in analysis, oblique abrupt slope Rock And Soil is main
For ground material, it is earth's surface rock mass through weathering, degrades, carries, post-depositional product, there are the spies such as loose, multiphase, changeable
Property, and influenced by stress level, stress history, stress path, stress state and rate of stressing, therefore use elastoplasticity
Constitutive model is analyzed.
For all Rock And Soils of stake in deformation process, stress-strain relation is in non-linear relation, for tracking load history ask displacement,
The full dose of strain and stress, therefore Mohr-Coulomb yield criterion is used, constitutive relation is described using incremental form.
(4) parameter is chosen
Calculating for the consistency and science for guaranteeing Numerical Simulation result and Practical Project, in Numerical Simulation Analysis
Parameter surveys data according to Practical Project to choose, and is specifically shown in Table 8.
8 Material Physics mechanics parameter of table
3.2 conceptual design
The vertical load that bridge pile foundation is born mainly includes the load etc. that self gravity and superstructure generate.Pile foundation is worn
It crosses soft stratum or unstable formation and vertical load is transmitted to the soil layer or rock stratum that deep is harder, compressibility is small, by having
Effect is using the side friction of the formation resistance and stake side rock mass that act on an end come vertical supporting loads.It is soft using finite element analysis
Part Marc to locating for the slope foot relatively of the different oblique abrupt slope gradients, piles with different length, stake diameter, the different distance of pilespacing free face, stake bottom not
Influence with position and the variation of slope foot domatic to bridge pile foundation stress condition carries out simulation analysis, studies the oblique steep slope region in mountain area
The bearer properties of bridge pile foundation, the design for the type bridge pile foundation provide theoretical foundation.
A diameter 1.5m, the long 15m of stake are taken, using different vertical load hierarchical loadings, analyzes bridge pile foundation under different gradient
Bearer properties, calculate operating condition see Table 9 for details.
The oblique abrupt slope slope change of table 9 calculates operating condition
Note: the operating condition that 1. gradients are 0 °, as flat slope pile foundation analyze operating condition (similarly hereinafter) as a comparison；
3.3 calculated results and analysis
By analysis, vertical bearing capacity is mainly become by the maximum that the deformation characteristic and superstructure of stake side rock mass are allowed
Shape determines.One timing of the long and stake diameter of stake, by carrying out FEM calculation to the bridge pile foundation in the different tiltedly abrupt slope gradients, point
Analyse the changing rule of bearing capacity of pile foundation.Following table is that a diameter is Pile Bearing Capacity under 1.5m long and oblique abrupt slope slope changes.Root
Show that piles with different grows the corresponding Pile Bearing Capacity at different gradient and is shown in Table 10 according to Numerical Model Analysis result.
Table 10
The bearing capacity reducing coefficient that table 11 is calculated acquires bearing capacity (being calculated according to table 7)
Table 12
Note: αV=PTable 6/PTable 7
In above table: table 6 is the oblique Steep Slope Bridge Pile Bearing Capacity value being calculated according to Numerical Simulation Analysis, table
11 be to be obtained based on level land Pile Bearing Capacity value by the Pile Bearing Capacity reduction coefficient solution of model test proposition,
Table 12 is the ratio of bearing capacity value and bearing capacity value in table 11 in table 10.Data in analytical table 12 are missed substantially all 1 or so
Difference fully meets engine request 10% 1% or so, it can be seen that Pile Bearing Capacity reduction coefficient proposed by the present invention
It can be applied in practice in engineering.
The oblique Steep Slope Bridge Vertical Bearing Capacity of Pile Foundation reduction coefficient ζ in mountain area proposed by the present inventionV, concrete application are as follows: first
Vertical Bearing Capacity of Pile Foundation P when no abrupt slope is calculated according to Pile Bearing Capacity calculation formula (formula 1-1 or 1-2)0, with this
It is worth on the basis of calculated value, needs to calculate the Pile Bearing Capacity P of the friction pile under corresponding operating condition discussed abovei, then have Pi=P0
×ζV。
The above content is merely illustrative of the invention's technical idea, and this does not limit the scope of protection of the present invention, all to press
According to technical idea proposed by the present invention, any changes made on the basis of the technical scheme each falls within claims of the present invention
Protection scope within.
Claims (6)
1. the calculation method of oblique Steep Slope Bridge vertical bearing capacity correction factor, which comprises the following steps:
Pile Bearing Capacity disturbance degree α under step 1, calculating different gradientv,In formula, P0For under identical operating condition
Flat slope pile foundation ultimate vertical bearing capacity, P indicates the pile foundation vertical ultimate bearing capacity of certain gradient；
Step 2, the Pile Bearing Capacity disturbance degree α obtained according to step 1vCalculate pile foundation side friction reduction coefficient ζv, ζv=1-
αv。
2. the calculation method of oblique Steep Slope Bridge vertical bearing capacity correction factor according to claim 1, feature exist
In by testing under vertical uniform load q, it is perpendicular to measure pile foundation of the long friction pile of piles with different under different gradient in step 1
To ultimate bearing capacity P, when the gradient is 0 ° with the long friction pile of stake in flat slope pile foundation ultimate vertical bearing capacity P0。
3. the calculation method of oblique Steep Slope Bridge vertical bearing capacity correction factor according to claim 1, feature exist
In taking displacement at pile top is the corresponding load of 1.5mm as Ultimate Bearing Capacity of Pile Foundation P.
4. the calculation method of oblique Steep Slope Bridge vertical bearing capacity correction factor according to claim 1, feature exist
In, in step 1, n gradient X of measurementjUnder pile foundation vertical ultimate bearing capacity Pj, 0≤j≤n-1, n >=2, and calculate the gradient
Under reduction coefficient ζvj, when gradient X is in Xj~Xj+1Between when, pile foundation vertical ultimate bearing capacity ζv=ζvj+k(Pj+1-Pj), k=
(Xj+1-Xj)/(ζvj+1-ζvj)。
5. the calculation method of oblique Steep Slope Bridge vertical bearing capacity correction factor according to claim 4, feature exist
In n=6, the measurement gradient is 0 °, 30 °, 45 °, 60 °, 75 ° and 90 °.
6. a kind of oblique Steep Slope Bridge vertical bearing capacity calculation method, which is characterized in that the oblique Steep Slope Bridge pile foundation of friction pile
Bearing capacity [Ra1] calculation formula are as follows:Embedded rock pile it is oblique
Steep Slope Bridge bearing capacity of pile foundation [Ra2] calculation formula are as follows:On
In formula, pile foundation side friction reduction coefficient ζvIt obtains according to the method for claim 1, [Ra1]-friction pile single-pile vertical orientation by
Press bearing capacity feasible value, [Ra2]-embedded rock pile single-pile vertical orientation compression bearing feasible value；U-pile body perimeter；Ap- stake end section
Area；N-soil number of plies；li- each the thickness of the layer；qik- and liThe frictional resistance standard value of corresponding each soil layer and stake side；
[fa0The basic feasible value of bearing capacity of soil at]-stake end；H-stake end buried depth；k2- allowable bearing with depth amendment
Coefficient；γ2It is more than-stake end that each soil layer is weighted and averaged severe；λ-correction factor；m0- clear bottom coefficient；c1- end resistance plays
Coefficient；frk- stake end rock saturation uniaxial compressive strength standard value；c2iThe side of-the i-th layer of rock stratum hinders mobilization factor；hi- stake is embedding
Enter the thickness of each rock stratum part；M-rock stratum the number of plies；ζsThe collateral resistance mobilization factor of-coating soil.
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