Estimation method for pressure transfer effect of fill soil close to bridge foundation

Abstract

The invention discloses a method for estimating the pressure transfer effect of fill soil close to a bridge foundation, and relates to the technical field of fill, and the method comprises the steps: researching the influence of airport fill loading on the mechanical response of a close-range bridge foundation; defining a soil pressure transfer coefficient beta from fill loading to an adjacent bridge foundation, and summarizing influence factors of the soil pressure transfer coefficient beta into three parts; numerical simulation calculation analysis is carried out through MIDAS GTS NX, a three-dimensional numerical analysis model is established, the influence of the upper factor, the middle factor and the lower factor on the soil pressure transfer coefficient beta is researched, and the influence rule of the soil pressure transfer coefficient beta is obtained; a regression equation is obtained through regression analysis, and a modified coulomb formula is provided based on a coulomb theory soil pressure formula; and comparing and analyzing a model test and a numerical analysis result, and verifying the reasonability of the formula by comparing theoretical calculation with a finite element result. According to the method for estimating the pressure transfer effect of the fill soil close to the bridge foundation, scientific guidance can be provided for engineering.

Description

Technical Field

[0001] The invention relates to the technical field of filling, and in particular to a method for estimating the pressure transfer effect of filling soil adjacent to a bridge foundation. Background Art

[0002] At present, there are few studies on similar geotechnical engineering problems at home and abroad. In order to ensure the overall safety and stability of the airport high fill project and bridge foundation engineering system, and at the same time ensure investment savings, it is necessary to further clarify the soil pressure transmission effect of the airport high fill slope support piles to the adjacent bridge foundation piers. This paper intends to explore the mechanism of soil pressure transmission from the airport fill to the adjacent bridge foundation through theoretical analysis, numerical simulation and other methods, in order to provide scientific guidance for similar projects. Summary of the invention

[0005] The present invention proposes a method for estimating the pressure transfer effect of fill soil adjacent to a bridge foundation to solve the problems mentioned in the above technical background.

[0006] To achieve the above object, the present invention proposes a method for estimating the pressure transfer effect of fill soil adjacent to a bridge foundation, comprising the following steps:

[0007] S1. Study the influence of airport fill loading on the mechanical response of close-range bridge foundations;

[0008] S2. Define the earth pressure transfer coefficient β from the backfill load to the adjacent bridge foundation, and summarize the influencing factors of the earth pressure transfer coefficient β into three major factors: "upper, middle and lower": "upper" factors include the backfill height H, the cement content of the filler δ, the original foundation slope α and the platform width L; "middle" factors include the distance D between the bridge foundation and the supporting piles; "lower" factors include the reinforcement thickness of the soft foundation h, the diameter of the cement soil mixing pile d, the spacing between the cement soil mixing piles s and the cement soil strength f of the cement soil mixing piles cu ;

[0009] S3. Through numerical simulation and analysis using MIDAS GTS NX, a three-dimensional numerical analysis model was established to study the influence of the "upper" factor, "middle" factor, "lower" factor and their corresponding nine factors on the earth pressure transfer coefficient β, and obtain the influence law of the "upper" factor, "middle" factor and "lower" factor on the earth pressure transfer coefficient β;

[0010] S4. Through regression analysis, the regression equations of the soil pressure transfer coefficient β under the "upper" factor, "middle" factor and "lower" factor are obtained. Based on the Coulomb theory soil pressure formula, the modified Coulomb formula for the soil pressure of the existing bridge foundation due to adjacent loading is proposed; the model test results are compared with the numerical analysis results, and the rationality of the formula is verified by comparing the theoretical calculation with the finite element results.

[0011] Preferably, the formula of the earth pressure transfer coefficient β is as follows:

[0012]

[0013] Among them, E1 is the lateral earth pressure of the retaining wall, and E2 is the lateral earth pressure of the bridge cap, both in kN·m -1 , used to solve the soil pressure design problem near the bridge foundation.

[0014] Preferably, S3 establishes a three-dimensional numerical analysis model as follows:

[0015] S31, generating a geometric model, the length of the three-dimensional model in the X-axis direction is 113m, the length in the Y-axis direction is 44.5m, the model height is 86.3m, and the bridge pile foundation, retaining wall pile foundation, and slope protection piles are all circular piles;

[0016] S32, generate unit grids. The soil, foundation and retaining wall use automatic generation of 3D grids, and the automatic-solid function is used for grid division. The hybrid grid generator is selected for division, and the basic grid size is 5m; the bridge, retaining wall pile foundation and slope protection pile use beam unit simulation to automatically generate 1D grids, and the automatic-line function is used for grid division, and the basic grid size is 3.2m;

[0017] S33. Select gravity load and specify the model boundary conditions; the model boundary conditions are as follows: ① The top of the high fill and the ground surface are free boundaries without any constraints; ② The left and right sides of the model constrain the displacement in the X direction; ③ The front and rear sides constrain the displacement in the Y direction; ④ The bottom of the model restricts displacement in three directions;

[0018] S34, construction stage management, using static / slope analysis to manage construction stages and create stress type construction stage groups;

[0019] S35, select the calculation parameters, select γ-fill bulk density, e-porosity, E-elastic modulus, ν-Poisson's ratio, c-cohesion and -internal friction angle is selected as the formation parameter, E-elastic modulus and ν-Poisson's ratio are selected as concrete parameters;

[0020] S36. Study the numerical scheme of the effects of “upper” factors, “middle” factors and “lower” factors on soil pressure transfer, and obtain the influence rules of “upper” factors, “middle” factors and “lower” factors on soil pressure transfer coefficient β.

[0021] Preferably, the construction stage group of S34 includes the following 6:

[0022] Ground stress balance: The natural stress field existing before the construction is called the initial ground stress field. During the calculation process of finite element, the initial ground stress generated by the self-weight stress is simulated by clearing the displacement of the initial stress field.

[0023] Pile foundation construction: Activate the pile foundation-1D grid group to simulate pile foundation construction;

[0024] Foundation pit excavation: passivate the foundation pit excavation range grid group and the cap grid group, and simulate the foundation pit excavation;

[0025] Bridge foundation and pier construction: In this construction stage group, activate the bridge pile foundation-1D grid group, pier grid group, and pier column grid group, activate the pier to change the attribute boundary, and simulate the bridge pile foundation and pier construction;

[0026] Backfilling of foundation pit and construction of retaining wall: reactivate the grid group of foundation pit excavation range, activate the grid group of slope cutting range, the grid group of buttress retaining wall, the grid group of retaining wall, and the grid group of No. 1 slope protection pile, activate the base of buttress retaining wall to change the attribute boundary, and simulate the backfilling of foundation pit and the construction of retaining wall;

[0027] Fill construction: Activate the fill grid group to simulate the layered filling construction.

[0028] Preferably, the Coulomb theory earth pressure formula for clay soil in S4 is as follows:

[0029]

[0030]

[0031] Among them, P a is the active earth pressure, γ is the bulk density of fill, H0 is the height of retaining wall, K a is the active earth pressure coefficient, α0 is the angle between the vertical line and the wall, β0 is the angle between the horizontal plane and the wall, is the internal friction angle, δ0 is the friction between the fill and the front, K q is the overload coefficient, q is the standard value of the uniformly distributed surface load, η is the cohesion influence coefficient, and c is the cohesion of the soil.

[0032] Preferably, the modified Coulomb earth pressure formula of the "upper" factor on the adjacent bridge foundation is as follows:

[0033] Introducing the earth pressure transfer coefficient β into the Coulomb earth pressure formula, the modified Coulomb earth pressure formula for the fill load on the adjacent bridge foundation considering the fill height H is obtained as follows:

[0034] E a =β·P a =[-0.208ln(H)+1.1341]P a ;

[0035] The earth pressure transfer coefficient β is introduced into the Coulomb earth pressure formula, and the modified Coulomb earth pressure formula of the fill load on the adjacent bridge foundation considering the filler cement content δ is obtained as follows:

[0036] E a =(-0.0076δ+0.5319)·P a ;

[0037] The earth pressure transfer coefficient β is introduced into the Coulomb earth pressure formula, and the modified Coulomb earth pressure formula of the fill load on the adjacent bridge foundation considering the original foundation slope α is obtained as follows:

[0038]

[0039] The earth pressure transfer coefficient β is introduced into the Coulomb earth pressure formula, and the modified Coulomb earth pressure formula of the fill load on the adjacent bridge foundation considering the platform width L is obtained as follows:

[0040] E a =[0.4784e 0.0094L ]·P a .

[0041] The preferred formula for the modified Coulomb earth pressure of the "middle" factor on the adjacent bridge foundation is as follows:

[0042] The earth pressure transfer coefficient β is introduced into the Coulomb earth pressure formula, and the modified Coulomb earth pressure formula of the fill load on the adjacent bridge foundation is obtained when the distance D between the bridge foundation and the supporting pile is considered as follows:

[0043] E a =(0.5119D- 0.101 )·P a .

[0044] Preferably, the modified Coulomb earth pressure formula of the "lower" factor on the adjacent bridge foundation is as follows:

[0045] The earth pressure transfer coefficient β is introduced into the Coulomb earth pressure formula, and the modified Coulomb earth pressure formula of the fill load on the adjacent bridge foundation considering the reinforcement thickness h is obtained as follows:

[0046] E a =(0.0115ln(h)+0.5183)·P a ;

[0047] The earth pressure transfer coefficient β is introduced into the Coulomb earth pressure formula, and the modified Coulomb earth pressure formula of the fill load on the adjacent bridge foundation considering the pile diameter d of the cement soil mixing pile is obtained as follows:

[0048] E a=[0.0074ln(d)+0.3826]·P a ;

[0049] The earth pressure transfer coefficient β is introduced into the Coulomb earth pressure formula, and the modified Coulomb earth pressure formula of the fill load on the adjacent bridge foundation considering the spacing s of cement soil mixing piles is obtained as follows:

[0050] E a =(-0.003s+0.3824)·P a ;

[0051] The soil pressure transfer coefficient β is introduced into the Coulomb soil pressure formula to obtain the cement soil strength f considering the cement soil mixing pile. cu Under this condition, the modified Coulomb earth pressure formula of fill load on adjacent bridge foundation is as follows:

[0052] E a =[0.00811n(f cu )+0.3755]·P a .

[0053] Therefore, the present invention adopts the above-mentioned method for estimating the pressure transfer effect of fill soil adjacent to the bridge foundation, which has the following beneficial effects:

[0054] (1) The concept of soil pressure transfer coefficient β near the bridge foundation is proposed to facilitate the reasonable calculation and design of the soil pressure near the bridge foundation;

[0055] (2) For the three major categories of "upper", "middle" and "lower", nine factors are used to propose the Coulomb formula for the correction of the soil pressure on the existing bridge foundation by the adjacent loading, which is convenient for designers to make reasonable calculations of the soil pressure on the bridge foundation.

[0056] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 This is a flow chart of a method for estimating pressure transfer effect of fill soil adjacent to a bridge foundation according to the present invention;

[0058] Figure 2 It is a schematic diagram of the upper influencing factors of a method for estimating the pressure transfer effect of fill soil near a bridge foundation according to the present invention;

[0059] Figure 3 It is an overall network diagram of a model of an estimation method for pressure transmission effect of fill soil adjacent to a bridge foundation according to the present invention;

[0060] Figure 4 It is a schematic diagram of influencing factors in a method for estimating pressure transfer effect of fill soil adjacent to a bridge foundation according to the present invention;

[0061] Figure 5 It is a schematic diagram of the lower influencing factors of a method for estimating the pressure transfer effect of fill soil near a bridge foundation according to the present invention;

[0062] Figure 6 A schematic diagram of soil pressure calculation for estimating the soil pressure transmission effect of fill soil adjacent to a bridge foundation according to the present invention;

[0063] Figure 7 A comparison diagram of a theoretical formula for fill height H and numerical simulation calculation results of a method for estimating the pressure transfer effect of fill soil near a bridge foundation according to the present invention;

[0064] Figure 8 A comparison diagram of a theoretical formula for the cement content δ of a filler material and numerical simulation calculation results of a method for estimating the pressure transfer effect of fill soil near a bridge foundation according to the present invention;

[0065] Fig. 9 A comparison diagram of the original foundation slope α theoretical formula and numerical simulation calculation results of a method for estimating the pressure transfer effect of fill soil near a bridge foundation according to the present invention;

[0066] Fig.10 A comparison diagram of the platform width L theoretical formula and numerical simulation calculation results of a method for estimating the pressure transmission effect of fill soil near a bridge foundation according to the present invention;

[0067] Fig.11 A method for estimating the pressure transfer effect of fill soil near a bridge foundation according to the present invention is a comparison diagram of the theoretical formula of the distance D between the bridge foundation and the supporting piles and the numerical simulation calculation results;

[0068] Fig.12 A comparison diagram of a theoretical formula for the thickness h of a soft foundation reinforcement and numerical simulation calculation results of an estimation method for the pressure transfer effect of fill soil near a bridge foundation according to the present invention;

[0069] Fig.13 A comparison diagram of the theoretical formula of the cement-soil mixing pile diameter d and the numerical simulation calculation results of a method for estimating the pressure transfer effect of fill soil near a bridge foundation according to the present invention;

[0070] Fig.14 A comparison diagram of the theoretical formula of the spacing s of cement-soil mixing piles and the numerical simulation calculation results of a method for estimating the pressure transfer effect of fill soil near a bridge foundation according to the present invention;

[0071] Fig.15 The present invention is a method for estimating the pressure transmission effect of fill soil near the bridge foundation. The cement soil strength f of the cement soil mixing pile cu Comparison chart of theoretical formula and numerical simulation results. DETAILED DESCRIPTION

[0072] The following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0073] like Figure 1 As shown in FIG. 1 , a method for estimating the pressure transfer effect of fill soil adjacent to a bridge foundation includes the following steps:

[0074] S1. Study the influence of airport fill loading on the mechanical response of close-range bridge foundations.

[0075] Although the theoretical soil pressure calculation method can calculate the soil pressure on the fill retaining wall, it cannot calculate the soil pressure on the bridge foundation. If the design value of the soil pressure on the bridge foundation is directly taken as the soil pressure behind the retaining wall, the design load on the bridge foundation will be too large; if the supporting effect of the retaining wall is considered too large and the soil pressure transferred from the retaining wall to the bridge foundation is ignored, the design load on the bridge foundation will be too small, which will inevitably have a significant impact on the bridge foundation. At present, these two extremes often appear in the design results. However, the soil pressure actually acting on the adjacent bridge foundation must be between these two loads. For this reason, the concept of soil pressure transfer coefficient is proposed.

[0076] S2. Define the earth pressure transfer coefficient β of the backfill load to the adjacent bridge foundation, and summarize the influencing factors of the earth pressure transfer coefficient β into three parts: the "upper" factors include the backfill height H, the cement content of the filler δ, the original foundation slope α and the platform width L; the "middle" factors include the distance D between the bridge foundation and the supporting piles; the "lower" factors include the reinforcement thickness h of the soft foundation, the diameter d of the cement-soil mixing piles, the spacing s of the cement-soil mixing piles and the cement-soil strength f of the cement-soil mixing piles. cu .

[0077] like Figure 2 As shown in Figure 2, the formula for the earth pressure transfer coefficient β is as follows:

[0078]

[0079] Among them, E1 is the lateral earth pressure of the retaining wall, and E2 is the lateral earth pressure of the bridge cap, both in kN·m -1 The transfer coefficient of fill load to bridge foundation soil pressure is the ratio of the resultant earth pressure of the retaining wall to the resultant earth pressure of the bridge foundation pedestal, which is used to solve the design problem of bridge foundation soil pressure caused by adjacent loads.

[0080] S3. Through numerical simulation and analysis using MIDAS GTS NX, a three-dimensional numerical analysis model is established to study the influence of the "upper" factor, "middle" factor, "lower" factor and their corresponding nine factors on the soil pressure transfer coefficient β, and obtain the influence law of the "upper" factor, "middle" factor and "lower" factor on the soil pressure transfer coefficient β.

[0081] MIDAS-GTS / NX can intuitively build complex three-dimensional geometric models, and also provides a wealth of material constitutive models, unit libraries and boundary conditions that can simulate the constitutive relations of most typical geotechnical materials. This embodiment uses MIDASGTS NX for numerical simulation and analysis.

[0082] S31. Generate a geometric model. The length of the 3D model in the X-axis direction is 113m, the length in the Y-axis direction is 44.5m, and the model height is 86.3m. The bridge pile foundation, retaining wall pile foundation, and slope protection pile are all circular piles; the bridge pile foundation has a diameter of 1.5m and a pile length of 55m; the retaining wall pile foundation has a diameter of 1m and a pile length of 46.2m; the No. 1 slope protection pile has a diameter of 1.2m and a pile length of 19m. The A-type retaining wall is 8m long, 22.5m wide, and 18m high. The retaining wall panel and buttress are 0.8m thick; the B-type retaining wall is 3.9m long and 5.5m high. The bridge A cap is 10.3m long, 14.2m wide, and 3.5m high; the B cap is 10.3m long, 18.1m wide, and 5.1m high; the two caps are 16.8m apart and connected by a 3.6m wide and 2.6m high concrete beam.

[0083] S32, such as Figure 3 As shown, the unit grid is generated. The soil, abutment and retaining wall use automatic 3D grid generation, the automatic-solid function is used for grid division, and the hybrid grid generator is selected for division. The basic grid size is 5m; the bridge, retaining wall pile foundation and slope protection pile use beam unit simulation to automatically generate 1D grid, and the automatic-line function is used for grid division, and the basic size is 3.2m.

[0084] S33. Select gravity load and specify model boundary conditions. The model has only one gravity load. Select gravity load after meshing. Model boundary conditions are as follows: ① The top of the high fill and the ground surface are free boundaries without any constraints; ② The left and right sides of the model constrain displacement in the X direction; ③ The front and rear sides constrain displacement in the Y direction; ④ The bottom of the model restricts displacement in three directions.

[0085] S34, construction phase management, using static / slope analysis to conduct construction phase management, creating stress type construction phase groups; according to the design drawings of the terminal building foundation pit support and the slope support project on the south side of the terminal building for the third phase expansion project of a certain airport, the bridge and high fill construction are divided into multiple steps including pile foundation construction ~ fill construction.

[0086] The numerical simulation of this embodiment sets the following 6 construction stage groups:

[0087] Ground stress balance: The natural stress field existing before the construction is called the initial ground stress field. During the calculation process, the finite element method simulates the initial ground stress generated by the self-weight stress by clearing the displacement of the initial stress field. In the initial construction step of the construction phase management group, MIDAS GTS activates the 1st to 4th layer soil grid group, the original fill grid group, the pedestal grid group, and the buttress retaining wall base grid group, activates the displacement boundary and gravity load, and checks the displacement clearing option to clear the initial stress displacement of all units and realize the simulation analysis of the initial stress field. Note: The attributes of the pedestal grid group and the buttress retaining wall base grid group activated in this construction phase group are still the first layer soil attribute parameters.

[0088] Pile foundation construction: Activate the Pile Foundation-1D grid group to simulate pile foundation construction.

[0089] Foundation pit excavation: passivate the foundation pit excavation range grid group and the foundation bearing platform grid group, and simulate the foundation pit excavation.

[0090] Bridge foundation and cap construction: In MIDAS GTS, you can use the static / slope analysis, boundary, and change attribute functions to change the properties of the grid group. In this construction stage group, activate the bridge pile foundation-1D grid group, the cap grid group, and the column grid group on the cap, activate the cap change attribute boundary, and simulate the bridge pile foundation and cap construction.

[0091] Backfilling of foundation pit and construction of retaining wall: reactivate the grid group of foundation pit excavation range, activate the grid group of slope cutting range, the grid group of buttress retaining wall, the grid group of retaining wall and the grid group of No. 1 slope protection pile, activate the base of buttress retaining wall to change the attribute boundary, and simulate the backfilling of foundation pit and construction of retaining wall.

[0092] Fill Construction: Activate the fill grid group to simulate fill construction.

[0093] S35, select the calculation parameters, select γ-fill bulk density, e-porosity, E-elastic modulus, ν-Poisson's ratio, c-cohesion and -internal friction angle is selected as the formation parameter, and E-elastic modulus and ν-Poisson's ratio are selected as concrete parameters.

[0094] In this numerical simulation, the bridge, retaining wall pile foundation, cap, retaining wall, and slope protection pile all use isotropic elastic constitutive models, and the rock and soil body uses the Moore-Coulomb constitutive model (MC). According to the geotechnical engineering investigation report of a certain airport phase III expansion project, the formation parameters are obtained as shown in Table 1.

[0095] Table 1 Selection of formation parameters for numerical analysis

[0096]

[0097] The bridge pile foundation, pedestal and column are all made of C40 concrete according to the bridge design report. The high fill support structure is made of C40 concrete according to the high fill support design report. The counter-pressure soil retaining wall is made of C30 concrete. The concrete parameters are shown in Table 2.

[0098] Table 2 Concrete parameter selection

[0099] Concrete strength grade Elastic modulus E / GPa Poisson's ratio ν C30 30.0 0.167 C40 32.5 0.167 C50 34.5 0.167

[0100] S36. Study the numerical scheme of the effects of “upper” factors, “middle” factors and “lower” factors on soil pressure transfer, and obtain the influence rules of “upper” factors, “middle” factors and “lower” factors on soil pressure transfer coefficient β.

[0101] The influence of the "upper" factors of the airport high fill on the soil pressure transfer effect of the adjacent bridge foundation is studied. The main factors are as follows: the influence of the fill height H, the cement soil content of the fill δ, the original foundation slope α, the platform width L, etc. on the soil pressure transfer effect. The schematic diagram of the upper influencing factors is shown in Figure 4 The specific numerical analysis scheme is shown in Table 3.

[0102] Table 3 Numerical schemes of upper influencing factors

[0103]

[0104] The influence of fill height H on the soil pressure transfer effect is studied. The fill properties are set to plain fill, original foundation slope α=1:2.0, platform width L=10m, and the influence of fill height H on the soil pressure transfer coefficient β is studied.

[0105] Taking H = 18m as an example, the lateral earth pressure of the retaining wall panel can be divided into three stages vertically. The first stage (10-16m): the lateral earth pressure of the retaining wall panel is 0, the second stage (2-10m): the lateral earth pressure of the retaining wall panel decreases along the height of the wall, showing a linear distribution, and the third stage (0-2m): the earth pressure curve has an inflection point at 2m. In the first stage, due to the lateral displacement of the fill soil, the wall and soil are separated, and the earth pressure of the retaining wall is zero; the distribution law of earth pressure in the second and third stages has a small fluctuation compared with the traditional theoretical calculation. The reason is that the friction between the retaining wall back, the ribs and the fill soil inhibits the transmission of earth pressure and causes the inflection phenomenon.

[0106] As the fill height increases, the soil pressure on the abutment gradually increases. When the fill height H=18-25, the maximum soil pressure at the abutment increases from 78.06kPa to 126.16kPa, an increase of 62%. This is because as the fill height H increases, the load at the fill increases sharply, and the load transferred to the adjacent bridge foundation abutment also increases.

[0107] When the fill height H increases from 18m to 25m, the earth pressure of the retaining wall increases from 514.5kN·m -1 Increased to 978.8 kN·m -1 , increased by 47.5%; the soil pressure of the foundation increased from 247.2kN·m -1 Increased to 455.54 kN·m -1 , increased by 39.8%; the earth pressure transfer coefficient β decreased from 53% to 47%. As the fill load increases, the earth pressure at the fill retaining wall and the cap increases in a coordinated manner, but due to the hysteresis of the fill earth pressure being transmitted downward, the earth pressure generated on the lower cap increases slightly, which leads to a gradual decrease in the earth pressure transfer coefficient.

[0108] Based on the above modeling process, the fill height is set to H = 18m, the original foundation slope α = 1:2.0, and the platform width L = 10m to study the influence of fill property δ on the earth pressure transfer coefficient.

[0109] When the filler property δ increases from δ = 0% to δ = 9%, the distribution law of the retaining wall earth pressure is consistent, the earth pressure gradually decreases, and the maximum earth pressure decreases from 110kPa to 62kPa, a decrease of 43.6%. This is because the cement soil content of the filler increases, the strength and stiffness of the fill are enhanced, the self-stability is enhanced, and the lateral earth pressure on the retaining wall is reduced.

[0110] When the filler property δ increases from δ = 0% to δ = 9%, the distribution law of the soil pressure on the cap is consistent, the soil pressure gradually decreases, and the maximum soil pressure decreases from 78.1kPa to 51.1kPa, a decrease of 34.6%. This is because the cement soil content of the filler increases, the shear strength of the fill increases, the fluidity of the fill soil decreases, and the lateral soil pressure on the cap decreases.

[0111] When the cement soil content of fill material is δ=0%~9%, the combined earth pressure of retaining wall is 514.5kN·m -1 Reduced to 414.1 kN·m -1 , reduced by 19.5%; the soil pressure of the foundation decreased from 247.2kN·m -1 Reduced to 193.4 kN·m -1 , decreased by 29.5%; the earth pressure transfer coefficient β decreased from 53% to 46%. With the increase of filler cement soil content, the earth pressure resultant force generated by the fill load on the retaining wall and the cap decreased synergistically, but due to the enhanced self-stability of the fill, the earth pressure transfer effect weakened, which led to a decrease in the earth pressure transfer coefficient.

[0112] Based on the above modeling process, the fill properties are set to plain fill, fill height H = 18m, and platform width L = 10m, and the influence of the original foundation slope α on the soil pressure transfer coefficient is studied.

[0113] When the original foundation slope α decreases from α = 1:1.5 to α = 1:2.0, the distribution law of the retaining wall earth pressure is consistent, the earth pressure gradually increases, and the maximum value increases from 70.1kPa to 80.4kPa, an increase of 14.7%. This is because the original foundation slope α is slowed down, the filling volume in the filling area increases, the load at the filling increases, and the lateral earth pressure on the retaining wall increases.

[0114] When the original foundation slope α decreases from α=1:1.5 to α=1:2.0, the soil pressure distribution at the cap is consistent, the soil pressure gradually increases, and the maximum value increases from 74kPa to 78kPa, an increase of 5%. The original foundation slope α slows down, the load at the fill increases, and the lateral soil pressure on the adjacent cap increases.

[0115] When the original foundation slope α is reduced from α=1:1.5 to α=1:2.0, the earth pressure of the retaining wall increases from 487.2kN·m -1 Increased to 514.1 kN·m -1 , increased by 5.5%; the soil pressure of the foundation increased from 242.3kN·m -1 Increased to 274.3 kN·m -1 , increased by 13.2%; the earth pressure transfer coefficient β increased from 49.7% to 53.3%. This is because the original foundation slope α slowed down, resulting in an increase in fill load, and the earth pressure on the retaining wall and the pedestal increased synergistically, but the original foundation slope slowed down, and the increase in earth pressure on the pedestal was greater than the increase in earth pressure on the retaining wall, which led to an increase in the earth pressure transfer coefficient.

[0116] Based on the above modeling process, the fill properties are set to plain fill, the original foundation slope α = 1:2.0, and the fill height H = 18m, and the influence of the platform width L on the earth pressure transfer coefficient is studied.

[0117] When the platform width L increases from L = 5m to L = 15m, the distribution law of the earth pressure on the retaining wall is consistent, the earth pressure gradually increases, and the maximum earth pressure increases from 68kPa to 74kPa, an increase of 8%. This is because the increase in platform width L increases the amount of fill in the fill area and the fill load, which leads to an increase in the earth pressure generated by the fill on the retaining wall.

[0118] When the platform width L increases from L = 5m to L = 15m, the distribution law of soil pressure on the cap is consistent, the soil pressure gradually increases, and the maximum soil pressure increases from 65kPa to 79kPa, an increase of 21%. This is because the increase in the load at the fill increases the lateral soil pressure on the cap.

[0119] When the platform width L increases from L = 5m to L = 15m, the earth pressure of the retaining wall increases from 485.1kN·m -1 Increased to 545.48 kN·m-1 , increased by 12.5%; the soil pressure of the foundation increased from 241.4 kN·m -1 Increased to 298.4 kN·m -1 , increased by 23.6%; the soil pressure transfer coefficient β increased from 50% to 55%. The increase in platform width L increases the soil pressure on the retaining wall and the cap, but the increase in platform width causes the increase in the soil pressure on the cap to be greater than the increase in the soil pressure on the retaining wall, which leads to an increase in the soil pressure transfer coefficient.

[0120] The influence of the "middle" factors of the airport high fill on the soil pressure transfer effect of the adjacent bridge foundation is studied. The main factors are as follows: The influence of the distance D between the bridge foundation and the supporting piles on the soil pressure transfer effect. The schematic diagram of the middle influencing factors is shown in Figure 5 The specific numerical analysis scheme is shown in Table 4.

[0121] Table 4 Numerical schemes of influencing factors in the middle

[0122]

[0123] Based on the above modeling process, the influence of the horizontal distance D between fill and bridge foundation on the earth pressure transfer coefficient is studied.

[0124] When the horizontal distance D between the fill and the bridge foundation increases from D = 0.5m to D = 8m, the distribution law of the earth pressure on the retaining wall is consistent, but the earth pressure changes slightly, which means that the change of the horizontal distance D between the fill and the bridge foundation has no effect on the lateral earth pressure of the retaining wall.

[0125] When the horizontal distance D between the fill and the bridge foundation increases from D = 0.5m to D = 8m, the distribution law of the soil pressure on the cap is consistent, the soil pressure gradually decreases, and the maximum soil pressure decreases from 151kPa to 72kPa, a decrease of 52%. This is because as the horizontal distance between the fill and the bridge foundation increases, the bridge foundation gradually moves away from the range of the fill load soil pressure.

[0126] When the horizontal distance D between the fill and the bridge foundation increases from D = 0.5m to D = 8m, the change range of the resultant earth pressure of the retaining wall is small, with a maximum difference of 1.3%; the resultant earth pressure of the cap increases from 247.2kN·m -1 Reduced to 223.5 kN·m -1 , decreased by 18.5%; the soil pressure transfer coefficient β decreased from 53% to 40%. The increase in the horizontal distance D between the fill and the bridge foundation will not affect the change of the earth pressure of the retaining wall, but the bridge foundation gradually moves away from the action range of the fill load earth pressure, and the earth pressure on the bridge foundation gradually decreases, resulting in a decrease in the earth pressure transfer coefficient.

[0127] The influence of the "lower" factors of the airport fill on the soil pressure transmission effect of the adjacent bridge foundation is studied. The weak stratum where the bridge foundation is located is reinforced with cement soil mixing piles. The main factors are as follows: reinforcement thickness h, cement soil mixing pile diameter d, cement soil mixing pile spacing s, cement soil mixing pile cement soil strength f cu The lower influencing factor diagram is as follows Figure 6 The specific numerical analysis scheme is shown in Table 5.

[0128] Table 5 Numerical schemes of the lower influencing factors

[0129]

[0130] This embodiment uses the composite foundation method to simulate the reinforcement of soft strata. The mechanism of the composite foundation is to fully mobilize the soil between piles and the piles to jointly bear the load.

[0131] Based on the above modeling process and composite foundation equivalent method, cement soil mixing piles are used to reinforce the soft foundation. The diameter of the cement soil mixing pile foundation is set to d = 0.6m, the pile foundation spacing is s = 1.2m, and the cement soil strength f cu =1.5MPa. The influence of reinforcement depth h of soft strata on soil pressure transfer coefficient is studied.

[0132] When the reinforcement depth h of the soft stratum increases from h = 3m to h = 15m, the distribution law of soil pressure is consistent, but the change amplitude of soil pressure is small, which shows that the change of the reinforcement depth h of the soft stratum has no effect on the lateral soil pressure of the retaining wall.

[0133] When the reinforcement depth h of the soft stratum increases from h = 3m to h = 15m, the distribution law of the soil pressure on the cap is consistent, the soil pressure gradually increases, and the maximum soil pressure increases from 88.7kPa to 95.3kPa, an increase of 3%. With the increase of the reinforcement depth h of the soft stratum, the range of high-strength soil around the bridge foundation gradually increases, which limits the horizontal displacement of the cap and causes the soil pressure on the cap to increase.

[0134] When the reinforcement depth of soft strata increases from h = 3m to h = 15m, the change range of the resultant earth pressure of the retaining wall is small, with a maximum difference of 1.3%; the resultant earth pressure of the cap increases from 278.5kN·m -1 Increased to 306 kN·m -1 , increased by 9.9%; the soil pressure transfer coefficient β increased from 53.1% to 54.9%. The increase in the reinforcement depth h of the soft stratum will not affect the size of the retaining wall soil pressure, but will lead to an increase in the soil pressure of the bridge cap, thereby increasing the soil pressure transfer coefficient.

[0135] Based on the above modeling process and composite foundation equivalent method, cement soil mixing piles are used to reinforce the soft foundation. The reinforcement depth of the soft foundation is set to h = 10m, the pile spacing is s = 1.2m, and the cement soil strength fcu =1.5MPa. The influence of the diameter d of cement-soil mixing pile foundation on the soil pressure transfer coefficient was studied.

[0136] When the diameter of the cement-soil mixing pile increases from d = 0.5m to d = 0.8m, the distribution of soil pressure is consistent, but the change in soil pressure is small, which means that the change in pile diameter has no effect on the soil pressure of the retaining wall.

[0137] When the diameter of the cement-soil mixing pile increases from d = 0.5m to d = 0.8m, the distribution law of the soil pressure on the cap is consistent, the soil pressure gradually increases, and the maximum soil pressure increases from 94.2kPa to 96.6kPa, an increase of 1%. As the diameter d of the cement-soil mixing pile increases, the strength of the soil around the bridge foundation increases, resulting in an increase in the soil pressure on the cap.

[0138] When the diameter of cement-soil mixing pile increases from d = 0.5m to d = 0.8m, the change range of the resultant earth pressure of retaining wall is small, with the maximum difference of 1.3%; the resultant earth pressure of cap increases from 278.5kN·m -1 Increased to 306 kN·m -1 , increased by 9.9%; the earth pressure transfer coefficient β increased from 37.7% to 38%. As the diameter of the pile foundation increases, the reinforcement effect of the soft foundation is better, the stiffness of the foundation after reinforcement is greater, and the coordinated deformation of the soft foundation and the bridge foundation is smaller, resulting in greater earth pressure transferred to the bridge foundation in the filling direction, which leads to an increase in the earth pressure transfer coefficient.

[0139] Based on the above modeling process and composite foundation equivalent method, cement soil mixing piles are used to reinforce the soft foundation. The reinforcement depth of the soft foundation is set to h = 10m, the diameter of the cement soil mixing pile foundation is d = 0.6m, and the cement soil strength f cu =1.5MPa. The influence of the spacing s between cement-soil mixing piles on the soil pressure transfer coefficient is studied.

[0140] When the spacing between cement-soil mixing piles increases from s = 1.0m to s = 1.8m, the distribution of earth pressure on the retaining wall is consistent, but the change in earth pressure is small, which means that the change in the spacing between cement-soil mixing piles s has no effect on the lateral earth pressure on the retaining wall.

[0141] When the spacing between cement-soil mixing piles increases from s=1.0m to s=1.8m, the distribution law of soil pressure on the cap is consistent, the soil pressure gradually decreases, and the maximum soil pressure decreases from 96.2kPa to 93.1kPa. As the spacing between cement-soil mixing piles s increases, the strength of the soil around the bridge foundation decreases, resulting in a decrease in the soil pressure on the cap.

[0142] When the spacing between cement-soil mixing piles increases from s = 1.0m to s = 1.8m, the change range of the resultant earth pressure of the retaining wall is small, with a maximum difference of 1.3%; the resultant earth pressure of the cap increases from 306kN·m-1 Reduced to 297 kN·m -1 , decreased by 2.8%; the earth pressure transfer coefficient β decreased from 37.9% to 37.6%. As the pile spacing s increases, the reinforcement effect of the soft foundation becomes worse, the stiffness of the reinforced foundation becomes smaller, the coordinated deformation of the soft foundation and the bridge foundation becomes larger, resulting in a smaller earth pressure transferred from the fill direction to the bridge foundation, which leads to a decrease in the earth pressure transfer coefficient.

[0143] Based on the above modeling process and composite foundation equivalent method, cement soil mixing piles are used to reinforce the soft foundation. The reinforcement depth of the soft foundation is set to h = 10m, the diameter of the cement soil mixing pile foundation is d = 0.6m, and the spacing of the cement soil mixing pile foundation is s = 1.2m. cu Influence on earth pressure transfer coefficient.

[0144] When the cement soil strength changes from f cu =0.5MPa increases to f cu =2.0MPa, the distribution of earth pressure on the retaining wall is consistent, but the change in earth pressure is small. This indicates that the strength of cement soil f cu The change of has no effect on the lateral earth pressure of the retaining wall.

[0145] When the cement soil strength changes from f cu =0.5MPa increases to f cu =2.0MPa, the distribution law of soil pressure on the foundation is consistent, the soil pressure gradually increases, and the maximum soil pressure increases from 88kPa to 96.6kPa, an increase of 9%. cu The increase of the soil pressure around the bridge foundation increases, which leads to the increase of soil pressure on the foundation.

[0146] Cement soil strength from f cu =0.5MPa increases to f cu =2.0MPa, the change range of the combined earth pressure of the retaining wall is small, with a maximum difference of 1.3%; the combined earth pressure of the foundation increases from 282kN·m -1 Increased to 308 kN·m -1 The soil pressure transmission coefficient β increased from 37% to 38%. cu The increase of the reinforcement coefficient will increase the reinforcement effect of the soft foundation, the greater the foundation stiffness after reinforcement, and the smaller the coordinated deformation of the soft foundation and the bridge foundation, resulting in a greater earth pressure transmitted to the bridge foundation in the fill direction, which in turn increases the earth pressure transfer coefficient.

[0147] The influence of the "upper" factor, "middle" factor and "lower" factor on the earth pressure transfer coefficient β is as follows: the earth pressure transfer coefficient β increases with the original foundation slope α, platform width L, reinforcement thickness h, cement soil mixing pile diameter d and cement soil strength f of the cement soil mixing pile. cuIt gradually increases with the increase of fill height H, filler cement content δ, the distance D between the bridge foundation and the supporting piles, and the spacing s between cement-soil mixing piles.

[0148] S4. Through regression analysis, the regression equations of the soil pressure transfer coefficient β under the "upper" factor, "middle" factor and "lower" factor are obtained. Based on the Coulomb theory soil pressure formula, the modified Coulomb formula for the soil pressure of the existing bridge foundation due to adjacent loading is proposed; the model test results are compared with the numerical analysis results, and the rationality of the formula is verified by comparing the theoretical calculation with the finite element results.

[0149] The Coulomb theory earth pressure formula for clay soil is as follows:

[0150]

[0151] Among them, P a is the active earth pressure, γ is the bulk density of fill, H0 is the height of retaining wall, K a is the active earth pressure coefficient, α0 is the angle between the vertical line and the wall, β0 is the angle between the horizontal plane and the wall, is the internal friction angle, δ0 is the friction between the fill and the front, K q is the overload coefficient, q is the standard value of the uniformly distributed surface load, η is the cohesion influence coefficient, and c is the cohesion of the soil.

[0152] The modified Coulomb earth pressure formula for the adjacent bridge foundation by the “upper” factor is as follows:

[0153] Introducing the earth pressure transfer coefficient β into the Coulomb earth pressure formula, the modified Coulomb earth pressure formula for the fill load on the adjacent bridge foundation considering the fill height H is obtained as follows:

[0154] E a =β·P a =[-0.208ln(H)+1.1341]P a ;

[0155] For the earth pressure of the fill retaining wall, the result of Coulomb earth pressure formula is recorded as E 1f , the numerical analysis result is recorded as E 1a , for the soil pressure on the foundation, the result of the modified Coulomb formula is recorded as E 2f , the numerical result is recorded as E 2a , compare the theoretical calculation results with the numerical analysis results, such as Figure 7 As shown by Figure 7It can be seen that the earth pressure E1 of the fill retaining wall obtained by numerical analysis is basically consistent with that obtained by Coulomb's earth pressure. However, the Coulomb's earth pressure calculation formula cannot calculate the earth pressure E2 on the adjacent bridge foundation. The earth pressure on the adjacent bridge foundation obtained by the modified Coulomb's earth pressure formula proposed in this embodiment is basically consistent with the numerical simulation calculation results, with an average error of 8.5%. This shows that it is reasonable for this embodiment to adopt the modified Coulomb's earth pressure calculation formula considering the fill height.

[0156] The earth pressure transfer coefficient β is introduced into the Coulomb earth pressure formula, and the modified Coulomb earth pressure formula of the fill load on the adjacent bridge foundation considering the filler cement content δ is obtained as follows:

[0157] E a =(-0.0076δ+0.5319)·P a ;

[0158] Depend on Figure 8 It can be seen that the soil pressure on the adjacent bridge foundation obtained by the modified Coulomb's earth pressure formula considering the filler properties is consistent with the numerical simulation calculation result, with an average error of 11.2%, indicating that the modified Coulomb's earth pressure calculation formula considering the filler properties adopted in this embodiment is reasonable.

[0159] The earth pressure transfer coefficient β is introduced into the Coulomb earth pressure formula, and the modified Coulomb earth pressure formula of the fill load on the adjacent bridge foundation considering the original foundation slope α is obtained as follows:

[0160]

[0161] Depend on Fig. 9 It can be seen that the soil pressure on the adjacent bridge foundation obtained by the modified Coulomb soil pressure formula considering the original foundation slope is consistent with the numerical simulation calculation result of this embodiment, with an average error of 9.3%, indicating that the modified Coulomb soil pressure calculation formula considering the original foundation slope adopted in this embodiment is reasonable.

[0162] The earth pressure transfer coefficient β is introduced into the Coulomb earth pressure formula, and the modified Coulomb earth pressure formula of the fill load on the adjacent bridge foundation considering the platform width L is obtained as follows:

[0163] E a =[0.4784e 0.0094 L]·P a .

[0164] Depend on Fig.10 It can be seen that the soil pressure on the adjacent bridge foundation obtained by the modified Coulomb's earth pressure formula considering the platform width is consistent with the numerical simulation calculation result of this embodiment, with an average error of 3.2%, indicating that the modified Coulomb's earth pressure calculation formula considering the platform width adopted in this embodiment is reasonable.

[0165] The modified Coulomb earth pressure formula for the adjacent bridge foundation by the “middle” factor is as follows:

[0166] The earth pressure transfer coefficient β is introduced into the Coulomb earth pressure formula, and the modified Coulomb earth pressure formula of the fill load on the adjacent bridge foundation is obtained when the distance D between the bridge foundation and the supporting pile is considered as follows:

[0167] E a =(0.5119D -0.101 )·P a .

[0168] Depend on Fig.11 It can be seen that the soil pressure on the adjacent bridge foundation obtained by the modified Coulomb earth pressure formula considering the distance between the fill and the bridge foundation is consistent with the numerical simulation calculation result of this embodiment, with an average error of 6.5%, indicating that the modified Coulomb earth pressure calculation formula considering the distance between the fill and the bridge foundation adopted in this embodiment is reasonable.

[0169] The modified Coulomb earth pressure formula for the adjacent bridge foundation by the “lower” factor is as follows:

[0170] The earth pressure transfer coefficient β is introduced into the Coulomb earth pressure formula, and the modified Coulomb earth pressure formula of the fill load on the adjacent bridge foundation considering the reinforcement thickness h is obtained as follows:

[0171] E a =(0.0115ln(h)+0.5183)·P a ;

[0172] Depend on Fig.12 It can be seen that the soil pressure on the adjacent bridge foundation obtained by the modified Coulomb's earth pressure formula considering the reinforcement depth of the soft foundation is consistent with the numerical simulation calculation result of this embodiment, with an average error of 9.4%, indicating that the modified Coulomb's earth pressure calculation formula considering the reinforcement depth of the soft foundation adopted in this embodiment is reasonable.

[0173] The earth pressure transfer coefficient β is introduced into the Coulomb earth pressure formula, and the modified Coulomb earth pressure formula of the fill load on the adjacent bridge foundation considering the pile diameter d of the cement soil mixing pile is obtained as follows:

[0174] E a =[0.0074ln(d)+0.3826]·P a ;

[0175] Depend on Fig.13 It can be seen that the soil pressure on the adjacent bridge foundation obtained by the modified Coulomb earth pressure formula considering the diameter of the reinforced pile is consistent with the numerical simulation calculation result of this embodiment, with an average error of 5.2%, indicating that the modified Coulomb earth pressure calculation formula considering the diameter of the reinforced pile adopted in this embodiment is reasonable.

[0176] The earth pressure transfer coefficient β is introduced into the Coulomb earth pressure formula, and the modified Coulomb earth pressure formula of the fill load on the adjacent bridge foundation considering the spacing s of cement soil mixing piles is obtained as follows:

[0177] E a =(-0.003s+0.3824)·P a ;

[0178] Depend on Fig.14 It can be seen that the soil pressure on the adjacent bridge foundation obtained by the modified Coulomb earth pressure formula considering the spacing between reinforced piles is consistent with the numerical simulation calculation result of this embodiment, with an average error of 7.1%, indicating that the modified Coulomb earth pressure calculation formula considering the spacing between reinforced piles adopted in this embodiment is reasonable.

[0179] The soil pressure transfer coefficient β is introduced into the Coulomb soil pressure formula to obtain the cement soil strength f considering the cement soil mixing pile. cu Under this condition, the modified Coulomb earth pressure formula of fill load on adjacent bridge foundation is as follows:

[0180] E a =[0.00811n(f cu )+0.3755]·P a .

[0181] Depend on Fig.15 It can be seen that the soil pressure on the adjacent bridge foundation obtained by the modified Coulomb's earth pressure formula considering the cement strength of the reinforced pile is consistent with the numerical simulation calculation result of this embodiment, with an average error of 5.4%, indicating that the modified Coulomb's earth pressure calculation formula considering the cement strength adopted in this embodiment is reasonable.

[0182] Therefore, the present invention adopts the above-mentioned method for estimating the pressure transfer effect of fill soil adjacent to the bridge foundation to study the pressure transfer mechanism of the airport fill soil adjacent to the bridge foundation, so as to provide scientific guidance for similar projects.

[0183] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for estimating the pressure transfer effect of fill soil adjacent to a bridge foundation, characterized in that: The following steps are involved: S1. Study the influence of airport fill loading on the mechanical response of close-range bridge foundations; S2. Define the earth pressure transfer coefficient β of the backfill load to the adjacent bridge foundation, and summarize the influencing factors of the earth pressure transfer coefficient β into three major factors: the upper factor includes the backfill height H, the cement content of the filler δ, the original foundation slope α and the platform width L; the middle factor includes the distance D between the bridge foundation and the supporting piles; the lower factor includes the reinforcement thickness of the soft foundation h, the diameter of the cement soil mixing pile d, the spacing between the cement soil mixing piles s and the cement soil strength f of the cement soil mixing piles. cu ; S3. Through numerical simulation and analysis using MIDAS GTS NX, a three-dimensional numerical analysis model is established to study the influence of the upper factor, middle factor, lower factor and their corresponding nine factors on the earth pressure transfer coefficient β, and obtain the influence law of the upper factor, middle factor and lower factor on the earth pressure transfer coefficient β; S4. Through regression analysis, the regression equations of the soil pressure transfer coefficient β under the upper factors, middle factors and lower factors are obtained. Based on the Coulomb theory soil pressure formula, a modified Coulomb formula for the soil pressure of the existing bridge foundation due to adjacent loading is proposed; the model test results are compared with the numerical analysis results, and the rationality of the formula is verified by comparing the theoretical calculation with the finite element results.

2. The method for estimating the pressure transfer effect of fill soil adjacent to a bridge foundation according to claim 1, characterized in that: The formula for the earth pressure transfer coefficient β is as follows: Among them, E1 is the lateral earth pressure of the retaining wall, and E2 is the lateral earth pressure of the bridge cap, both in kN·m -1 .

3. The method for estimating the pressure transfer effect of fill soil adjacent to a bridge foundation according to claim 1, characterized in that: S3 establishes a three-dimensional numerical analysis model as follows: S31, generating a geometric model, the length of the three-dimensional model in the X-axis direction is 113m, the length in the Y-axis direction is 44.5m, the model height is 86.3m, and the bridge pile foundation, retaining wall pile foundation, and slope protection piles are all circular piles; S32, generate unit grids. The soil, foundation and retaining wall use automatic generation of 3D grids, and the automatic-solid function is used for grid division. The hybrid grid generator is selected for division, and the basic grid size is 5m; the bridge, retaining wall pile foundation and slope protection pile use beam unit simulation to automatically generate 1D grids, and the automatic-line function is used for grid division, and the basic grid size is 3.2m; S33. Select gravity load and specify model boundary conditions; S34, construction stage management, using static / slope analysis to manage construction stages and create stress type construction stage groups; S35, select the calculation parameters, select γ-fill bulk density, e-porosity, E-elastic modulus, ν-Poisson's ratio, c-cohesion and -internal friction angle is selected as the formation parameter, E-elastic modulus and ν-Poisson's ratio are selected as concrete parameters; S36. Study the numerical scheme of the upper, middle and lower factors on the soil pressure transfer effect, and obtain the influence law of the upper, middle and lower factors on the soil pressure transfer coefficient β.

4. The method for estimating the pressure transfer effect of fill soil adjacent to a bridge foundation according to claim 3 is characterized in that: The construction phase groups of S34 include the following 6: Ground stress balance: The natural stress field existing before the construction is called the initial ground stress field. During the calculation process of finite element, the initial ground stress generated by the self-weight stress is simulated by clearing the displacement of the initial stress field. Pile foundation construction: Activate the pile foundation-1D grid group to simulate pile foundation construction; Foundation pit excavation: passivate the foundation pit excavation range grid group and the cap grid group, and simulate the foundation pit excavation; Bridge foundation and pier construction: In this construction stage group, activate the bridge pile foundation-1D grid group, pier grid group, and pier column grid group, activate the pier to change the attribute boundary, and simulate the bridge pile foundation and pier construction; Backfilling of foundation pit and construction of retaining wall: reactivate the grid group of foundation pit excavation range, activate the grid group of slope cutting range, the grid group of buttress retaining wall, the grid group of retaining wall, and the grid group of No. 1 slope protection pile, activate the base of buttress retaining wall to change the attribute boundary, and simulate the backfilling of foundation pit and the construction of retaining wall; Fill construction: Activate the fill grid group to simulate the layered filling construction.

5. The method for estimating the pressure transfer effect of fill soil adjacent to a bridge foundation according to claim 3 is characterized in that: The Coulomb theory earth pressure formula for cohesive soil in S4 is as follows: Among them, P a is the active earth pressure, γ is the bulk density of fill, H0 is the height of retaining wall, K a is the active earth pressure coefficient, α0 is the angle between the vertical line and the wall, β0 is the angle between the horizontal plane and the wall, is the internal friction angle, δ0 is the friction between the fill and the front, K q is the overload coefficient, q is the standard value of the uniformly distributed surface load, η is the cohesion influence coefficient, and c is the cohesion of the soil.

6. The method for estimating the pressure transfer effect of fill soil adjacent to a bridge foundation according to claim 5, characterized in that: The modified Coulomb earth pressure formula of the upper factor on the adjacent bridge foundation is as follows: The formula for the modified Coulomb earth pressure of the fill height H on the adjacent bridge foundation is as follows: E a =β·P a =[-0.208ln(H)+1.1341]P a ; The formula for the modified Coulomb earth pressure of the filler cement content δ on the adjacent bridge foundation is as follows: E a =(-0.0076δ+0.5319)·P a ; The formula for the modified Coulomb earth pressure of the original foundation slope α on the adjacent bridge foundation is as follows: The formula for the modified Coulomb earth pressure of the platform width L on the adjacent bridge foundation is as follows: E a =[0.4784e 0.0094L ]·P a 。 7. The method for estimating the pressure transfer effect of fill soil adjacent to a bridge foundation according to claim 5, characterized in that: The formula for the modified Coulomb earth pressure of the middle factor on the adjacent bridge foundation is as follows: The distance D between the bridge foundation and the supporting piles is the formula for the modified Coulomb earth pressure on the adjacent bridge foundation: E a =(0.5119D -0.101 )·P a .

8. The method for estimating the pressure transfer effect of fill soil adjacent to a bridge foundation according to claim 5, characterized in that: The formula for the modified Coulomb earth pressure of the lower factor on the adjacent bridge foundation is as follows: The formula for the modified Coulomb earth pressure of the reinforcement thickness h on the adjacent bridge foundation is as follows: From a =(0.0115ln(h)+0.5183)·P a ; The formula for the modified Coulomb earth pressure of the cement-soil mixing pile diameter d on the adjacent bridge foundation is as follows: AND a =[0.0074ln(d)+0.3826]·P a ; The formula for the modified Coulomb earth pressure of cement-soil mixing pile spacing s on the adjacent bridge foundation is as follows: E a =(-0.003s+0.3824)·P a ; Cement soil strength of cement soil mixing pile cu The modified Coulomb earth pressure formula for the adjacent bridge foundation is as follows: E a =[0.00811n(f cu )+0.3755]·P a 。

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