Composite pile foundation structure for road surface rigidity optimization of road transition section and design and use method of composite pile foundation structure

Abstract

The invention provides a composite pile foundation structure for road surface rigidity optimization of a road transition section and a design and use method of the composite pile foundation structure, and relates to the technical field of composite pile foundations. The composite pile foundation structure can be applied to an embankment foundation and a bridge abutment pile foundation and comprises a bearing platform, a pile cap, a gasket, an elastic composite plate, replaceable filler, a pile and a pile end self-adaptive deformer. The design and use method of the bridge abutment pile foundation is guided by the load settlement characteristic of the butted roadbed, and the design and use method of the embankment composite pile foundation is guided by the settlement control standard. Design variables comprise the pile length, the pile diameter, the pile number, the compression thickness of the elastic composite plate, the arrangement depth of the replaceable filler, the limit pile side friction resistance of the replaceable filler and the compression modulus of the replaceable material, the structure can optimize the overall rigidity of the road surface on one side of the abutment, the phenomenon of bump of the abutment is effectively avoided, zero-differential settlement is achieved theoretically, and the construction efficiency is improved. And the settlement index can be controlled in the application of an embankment foundation.

Description

Technical Field

[0001] The present application relates to the technical field of composite pile foundations, and in particular to a composite pile foundation structure for optimizing the pavement stiffness of a highway transition section and a design and use method thereof. Background Art

[0002] The problem of differential settlement in the transition section between roads and bridges has existed for a long time. For the abutment pile foundation, the stiffness on one side of the abutment actually has a large redundancy. The existing method usually considers increasing the stiffness from the roadbed side to reduce the differential settlement of the pavement in the transition section. The treatment method is not easy to accurately control the stiffness and consumes huge costs. There is no structure or method to reduce the stiffness on one side of the abutment.

[0003] In addition, the design of the existing abutment pile foundation is disconnected from the deformation characteristics of the roadbed. The misalignment formed under the subsequent reciprocating traffic load still exists, and zero differential settlement has not yet been achieved in theory.

[0004] For the settlement control of roadbed, the settlement deformation of the foundation accounts for a large proportion. Usually, densely distributed piles are arranged to reduce the deformation. The upper load is mainly borne by the piles. The upper load borne by the piles in the working state is less than their own ultimate bearing capacity, which requires a higher cost.

[0005] For piles, negative friction is usually considered to be a disadvantage and has not been properly utilized. Summary of the invention

[0006] The present application provides a composite pile foundation structure for optimizing the pavement stiffness of a highway transition section and a design and use method thereof, which makes reasonable use of the negative friction resistance on the pile side, and the force transmission path of the upper load of the pedestal is as follows: the upper load of the pedestal is first transmitted to a replaceable filler, then to the pile, and finally to the replaceable filler, and the pile fully exerts its bearing capacity under normal working conditions; for the abutment pile foundation, the overall stiffness is reduced, and the abutment pile foundation is designed based on the load-settlement characteristics of one side of the roadbed, thereby achieving zero differential settlement between the abutment and the roadbed transition section; for the embankment foundation, accurate control of the settlement of the roadbed transition section is achieved, the use of piles is reduced, and the soil between the piles shares more loads, thereby reducing settlement and saving construction costs; the present structure and the design and use method provide guarantees for the safety, comfort and smoothness of highway vehicle driving.

[0007] In a first aspect, the present application provides a composite pile foundation structure for optimizing the pavement stiffness of a highway transition section, comprising a cap, a pile cap, an elastic composite plate, a replaceable filler, a pile, and a pile end adaptive deformer;

[0008] The cap is embedded and connected with the elastic composite plate. The elastic composite plate is compressed and deformed during the construction stage to apply negative friction to the pile in advance. The elastic composite plate is located on the replaceable material. The replaceable filler is selected according to the parameters calculated by the deformation control equation. The control variables of the replaceable filler include depth, compression modulus, and ultimate side friction. The pile is arranged in plurality, and the spacing between each pile is at least 6.5 times the pile diameter. The pile exerts its ultimate bearing capacity in normal working state. The pile is connected to the pile cap and the pile end adaptive deformer at the top and end respectively.

[0009] Furthermore, the elastic deformation coefficient of the elastic composite plate is in the range of 0.3GPa to 0.9GPa, and the elastic composite plate is in the elastic stage when in use. The elastic composite plate includes an embedded plate, an elastic plate and a bottom plate. The upper surface of the embedded plate is provided with transverse grooves and longitudinal grooves. The embedded plate is embedded and connected to the base, and the elastic plate is located between the embedded plate and the bottom plate. The elastic plate is rigidly connected to the embedded plate and the bottom plate.

[0010] Furthermore, the pile has negative friction.

[0011] Furthermore, the pile cap is arranged on the top of the pile, the pile end adaptive deformer is arranged at the end of the pile, a gasket is arranged under the pile cap, and the pile passes through the elastic composite plate and the replaceable material and extends into the cap and the replaceable filler.

[0012] Furthermore, the replaceable filler is used to share the upper load increment after the pile exerts its ultimate bearing capacity to prevent rapid settlement and deformation.

[0013] Furthermore, the elastic deformation coefficient of the pile end adaptive deformer is 0.1 kPa, the thickness of the pile end adaptive deformer is 0.2 m, and the pile end adaptive deformer generates adaptive deformation according to the upper load.

[0014] Furthermore, the composite pile foundation structure has a force transmission path and a force transmission stage; wherein the force transmission path is: the load on the upper part of the cap is first transmitted to the replaceable filler, then to the pile, and finally to the replaceable filler;

[0015] The force transmission stage includes:

[0016] Stage 1: The load increment on the upper part of the cap is completely offset by the negative friction, the upper load is completely shared by the replaceable filler, and the bearing capacity of the pile is not fully exerted;

[0017] The second stage: The load increment on the upper part of the cap is completely shared by the piles, and the piles begin to exert their bearing capacity. The replaceable filler always shares the load of the absolute value of the total negative friction resistance pre-added during the construction stage;

[0018] The third stage: The load increment on the upper part of the foundation is completely borne by the replaceable filling material, the pile is in an elastic support state, the bearing capacity of the pile is fully exerted, and the replaceable filling material shares the set load.

[0019] In a second aspect, the present application provides a design and use method for a bridge abutment pile foundation, which is used to design a composite pile foundation structure for optimizing the pavement stiffness of a highway transition section as described in the first aspect, comprising:

[0020] Step 1: According to the roadbed design and construction plan, determine the highway grade and the standard value of the vehicle uniform load as q, and the filling height of the fill on one side of the roadbed as H. t , the height after preloading construction is H y , the width of the roadbed is B, the distance of half the span of the bridge is L, the gravity of the elastic composite plate is Q1, and the elastic deformation coefficient is K1;

[0021] Step 2: Preliminarily determine the width of the abutment on one side of the abutment pile foundation, the length of the abutment along the driving direction, the non-vehicle load Q2 borne by the abutment and the abutment, and the standard value of the ultimate bearing capacity of the replaceable filler, f. oa , check whether the foundation bearing satisfaction rate is greater than 0.5 through the following formula:

[0022]

[0023] Among them, ψ represents the foundation bearing satisfaction rate;

[0024] Step 3: Taking the vehicle load on the road surface as the independent variable, establish the post-construction settlement calculation function of the road surface on one side of the roadbed:

[0025] S L (q) = S C (q)+S S (q)+S E -s GC1

[0026] Among them, S L (q) represents the calculation function of the post-construction settlement of the road surface on one side of the roadbed, S C (q) represents the function of the subgrade deformation value with respect to the road vehicle load, S S (q) represents the function of foundation settlement value with respect to road vehicle load, S E It represents the self-compaction settlement value caused by the embankment fill load, s GC1 It is the construction settlement on one side of the roadbed;

[0027] S C (q) is calculated as follows:

[0028]

[0029] Among them, k is the total number of soil layers of embankment fill, αzi is the average vertical additional stress coefficient of the i-th fill layer, E sti is the compression modulus of the i-th layer of embankment fill, H i is the thickness of the i-th fill layer of the embankment;

[0030] S S (q) is calculated as follows:

[0031]

[0032] Among them, α z is the average additional stress coefficient of vehicle load on the bottom of the roadbed, z i-1 and Z i is the distance from the roadbed surface to the i-1th and ith soil layers, and are the average additional stress coefficients from the roadbed surface to the i-1th layer and the i-th layer of soil, σ z2 is the average additional stress of the roadbed fill on the bottom of the roadbed;

[0033] S E The calculation formula is as follows:

[0034]

[0035] Among them, γ i-1 and γ i H is the fill weight of the i-1th and i-th layers of the embankment; i-1 is the thickness of the i-1th layer of fill in the embankment;

[0036] s GC1 The calculation formula is as follows:

[0037] s GC1 =H t -H y

[0038] Step 4: Taking the vehicle load on the road surface as the independent variable, establish the post-construction settlement calculation function of the road surface on one side of the abutment pile foundation:

[0039] S q (q)=ψ q [S t (q)+S sp ]+S K (q)-s GC2

[0040] Among them, ψ q It is the correction factor for settlement calculation. In the absence of empirical value, it is taken as 1. t (q) is the function of the settlement of the elastic composite plate under additional pressure on the road surface vehicle load, S spis the settlement caused by the interaction between pile and soil, S K (q) is the total compression of the elastic composite plate, s GC2 It is the construction settlement on one side of the abutment;

[0041] S t (q) is calculated as follows:

[0042]

[0043] Among them, η p is the influence coefficient of pile penetration deformation, and its values ​​are 1, 1.15, and 3 respectively when the bearing layer at the pile end is sand, silt, and clay; x is the initial controlled compression deformation value of the elastic composite plate, n is the number of piles arranged in the abutment pile foundation; m is the number of soil layers included in the calculation depth, and the settlement calculation depth is calculated according to σ z =0.1σ c Determine, σ z is the additional stress, σ c is the vertical soil stress; E si is the compression modulus of the i-th layer of soil; p0 is the additional stress of the bottom plate of the elastic composite plate;

[0044] q sik is the limit lateral friction resistance, d is the diameter of the pile, k is the number of soil layers within the length of the pile; σ3 is the additional vertical stress of the backfill on the pile end plane;

[0045] S sp The calculation formula is as follows:

[0046]

[0047] In the formula, It represents the average lateral friction weighted by thickness within the pile body. It represents the average compression modulus within the pile body, l i is the thickness of the i-th soil layer, l is the pile length,

[0048] S K (q) The calculation method is as follows:

[0049]

[0050] s GC2 The calculation formula is as follows:

[0051]

[0052] Among them, ψ SC is the settlement correction factor, P G =Q1+Q2,B e is the basic equivalent width, ν s is the weighted Poisson's ratio of the soil within the pile length range under the elastic composite plate bottom plate, E0 is the average elastic modulus within the pile length range, C is the settlement influence coefficient of the pile group, and A e It is the effective load-bearing area obtained by deducting the pile area from the base area;

[0053] Step 5: Determine the seven unknown basic design parameters: pile length l, pile diameter d, pile number n, initial controlled compression deformation value x of the elastic composite plate, thickness h of the replaceable filler, and limit lateral friction resistance q of the replaceable filler. s1k , compression modulus E of replaceable filler s1 , the standard value of vehicle uniform load q is divided into 7 levels starting from 0, namely 0, q1, q2, q3, q4, q5, q6, and the overall deformation control equations of the road surface are established:

[0054]

[0055] Among them, S L (0), S L (q1), S L (q2), S L (q3), S L (q4), S L (q5), S L (q6) represents the post-construction settlement of the road surface on one side of the roadbed under the standard values ​​of vehicle uniform load of 0, q1, q2, q3, q4, q5, and q6, respectively. q (0), S q (q1), S q (q2), S q (q3), S q (q4), S q (q5), S q (q6) represents the post-construction settlement of the road surface on one side of the abutment under the standard values ​​of uniformly distributed vehicle load of 0, q1, q2, q3, q4, q5, and q6 respectively;

[0056] Step 6, solving the pavement overall deformation control equation group to obtain basic design combination parameters;

[0057] Step 7: Verify the basic design combination parameters, including:

[0058] Verify the overall bearing capacity safety. The overall bearing capacity safety K should be no less than 2:

[0059]

[0060] Pile spacing verification: The basic design combination parameters are required to meet the requirement that the pile spacing is greater than 6.5 times the pile diameter under the bottom size of the elastic composite plate;

[0061] Verification of symmetrical arrangement principle: The arrangement of abutment pile foundations should be symmetrical along the roadbed section and the longitudinal direction of the roadbed;

[0062] Step 8: Obtain the final zero differential settlement design combination parameters.

[0063] In a third aspect, the present application provides a design and use method for a highway foundation, which is used to design a composite pile foundation structure for optimizing the stiffness of a highway transition section pavement as described in the first aspect, comprising:

[0064] Step 1: According to the roadbed design and construction plan, determine the highway grade and the standard value of the vehicle uniform load q, the length of the transition section L1, and the initial height H of the fill when constructing one side of the roadbed t , fill height after preloading construction H y , roadbed and pavement width B, length A of elastic composite plate, width B of elastic composite plate, gravity Q1 of elastic composite plate, elastic deformation coefficient K1;

[0065] Step 2: Determine the bearing weight Q3, the total amount of transition section roadbed fill Q4, and the bearing capacity of the replaceable material foundation f oa Verify whether the foundation bearing capacity satisfaction rate is greater than 0.5:

[0066]

[0067] In the formula, ψ1 is the foundation bearing satisfaction rate;

[0068] Step 3: Taking the vehicle load on the road surface as the independent variable, establish the post-construction settlement calculation function of the road surface on one side of the roadbed:

[0069] S L (q) = S C (q)+S S (q)+S E -s GC3

[0070] Among them, S C (q) represents the function of the subgrade deformation value with respect to the road vehicle load, S S (q) represents the function of composite foundation settlement value with respect to road vehicle load, S E It represents the self-compaction settlement value caused by the embankment fill load, s GC3 For construction settlement;

[0071] S C (q) is calculated as follows:

[0072]

[0073] Among them, k is the total number of soil layers of embankment fill, αzi is the average vertical additional stress coefficient of the i-th layer of soil, E sti Compression modulus of the ith layer of embankment fill, H i is the thickness of the i-th fill layer of the embankment;

[0074] S S (q) is calculated as follows:

[0075] S S (q)=ψ l [S t (q)+S sp ]+S K (q)

[0076] Among them, ψ l Correction factor for settlement calculation; S t (q) is the function of the bottom settlement of the elastic composite slab with respect to the road vehicle load, p0 is the additional stress of the bottom plate of the elastic composite plate; η p is the influence coefficient of pile penetration deformation. When the bearing layer at the pile end is sand, silt, and clay, the values ​​are 1, 1.15, and 3, respectively. x is the initial controlled compression deformation value of the elastic composite plate. n is the number of piles arranged in the composite foundation. m is the number of soil layers included in the calculation depth. The settlement calculation depth is calculated according to σ z =0.1σ c Determine, σ z is the additional stress, σ c is the vertical soil stress, E si is the compression modulus of the i-th layer of soil, q sik is the limiting lateral friction, d is the diameter of the pile, k is the number of soil layers within the length of the pile, and Z i is the distance from the bottom of the elastic composite plate to the i-th soil layer, is the average additional stress coefficient from the bottom of the elastic composite plate to the i-th soil layer; S sp is the settlement caused by the interaction between pile and soil. l i is the thickness of the i-th soil layer, l is the pile length, S K (q) is the total compression of the elastic composite plate,

[0077] S E The calculation formula is as follows:

[0078]

[0079] Among them, γ i-1 and γ i H is the fill weight of the i-1th and i-th layers of the embankment; i-1is the thickness of the i-1th layer of fill in the embankment;

[0080] s GC3 The calculation formula is as follows:

[0081]

[0082] Among them, ψ SC is the settlement correction factor, P G =Q1+Q3+Q4, B e is the basic equivalent width, ν s is the weighted Poisson's ratio of the soil within the pile length range under the elastic composite plate bottom plate, E0 is the average elastic modulus within the pile length range, C is the settlement influence coefficient of the pile group, and A e It is the effective load-bearing area obtained by deducting the pile area from the base area;

[0083] Step 4: Determine the reasonable design range of pile length according to geological survey conditions, and determine the reasonable design range of pile diameter according to pile type; determine the post-construction settlement requirement of transition section pavement as [s]; determine the seven unknown basic design parameters: pile length l, pile diameter d, number of piles n, initial controlled compression deformation value x of elastic composite plate, thickness h of replaceable filler, and limit lateral friction resistance q of replaceable filler s1k , compression modulus E of replaceable filler s1 , establish the inequality group for overall deformation control of roadbed and pavement:

[0084]

[0085] In the formula, l min represents the minimum designable pile length, l max The minimum designable pile length, d min The minimum designable pile diameter, d max represents the minimum designable pile diameter, ··· represents other design requirements;

[0086] Step 5: Solve the settlement control inequality group to obtain the basic design combination parameters;

[0087]

[0088] In the formula, each row of parameters represents each set of basic design combination parameters calculated;

[0089] Step 6: Verify basic design combination parameters, including:

[0090] Verify the overall bearing capacity safety, the overall bearing capacity safety K is guaranteed to be no less than 2:

[0091]

[0092] Pile spacing verification: The basic design combination parameters are required to meet the requirement that the pile spacing is greater than 6.5 times the pile diameter under the bottom size of the elastic composite plate;

[0093] Verification of symmetrical layout principle: The pile layout of composite foundation should be symmetrical along the center line of the road surface;

[0094] Step 7: Establish cost function;

[0095] M=Cnπr 2 l+Dnπr 2 +EABh+FAB+GABH c +M q

[0096] In the formula, C represents the cost of pile material per cubic meter, unit: yuan / m 3 ; D represents the cost of the pile end adaptive deformer per square meter, unit: yuan / m 3 ; E represents the cost of replaceable materials per cubic meter, unit: yuan / m 3 ; F represents the local cost of elastic composite board per square meter, unit: yuan / m 3 ; G represents the cost of the foundation material per cubic meter, unit: yuan / m 3 ;H c is the average thickness of the cap; M q represents other costs;

[0097] Step 8: After Step 6 and Step 7, the final basic design parameter combination number is k, and the minimum construction cost is calculated based on the basic design combination parameters:

[0098]

[0099] Among them, M min Indicates the minimum construction cost, M1, M2, M 3、 M k They represent the construction costs under the first set of basic design parameters, the second set of basic design parameters, the third set of basic design parameters, and the kth set of basic design parameters respectively;

[0100] Step 9: Obtain the optimal design combination parameters.

[0101] The composite pile foundation structure and its design and use method for optimizing the pavement stiffness of the transition section of the highway provided by the present application, the elastic composite plate is compacted and deformed in the construction stage to pre-apply negative friction resistance, so that the negative friction resistance is effectively utilized; the distance between the piles under the pedestal is increased, so that the working state of the pile is in the limit bearing state, and the setting of the replaceable filler controls the sinking of the pile body, so that the pile and the soil share the upper load, and the stiffness of the overall composite pile foundation structure is reduced, and the construction cost is greatly saved; for the design of the abutment pile foundation structure, the application of the present application avoids the excessive stiffness redundancy of the abutment pile foundation structure, takes the load characteristics of one side of the roadbed as the design guide, proposes a group of pavement overall deformation control equations, and achieves the goal of zero differential settlement control at the junction with the roadbed; for the design of the composite pile foundation of the roadbed, takes the precise settlement value control as the design guide, proposes a group of pavement overall deformation control inequalities, and achieves the maximum bearing capacity of the pile, which greatly saves the construction cost. The structure and design and use method provided by the present application provide a guarantee for the safety, comfort and smoothness of highway vehicle driving. BRIEF DESCRIPTION OF THE DRAWINGS

[0102] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0103] Figure 1 A schematic diagram of a composite pile foundation structure for optimizing the pavement stiffness of a highway transition section provided in an embodiment of the present application;

[0104] Figure 2 A top view of a composite pile foundation structure for optimizing the pavement stiffness of a highway transition section provided in an embodiment of the present application;

[0105] Figure 3 A side view of a composite pile foundation structure for optimizing the pavement stiffness of a highway transition section provided in an embodiment of the present application;

[0106] Figure 4 A schematic diagram of a pile, a pile cap and a pile end adaptive deformer in a composite pile foundation structure for optimizing the pavement stiffness of a highway transition section provided in an embodiment of the present application;

[0107] Figure 5 A schematic diagram of a composite pile foundation structure for optimizing the pavement stiffness of a highway transition section provided in an embodiment of the present application, applied to a bridge abutment pile foundation working condition;

[0108] Figure 6 A schematic diagram of a composite pile foundation structure for optimizing pavement stiffness in a highway transition section provided in an embodiment of the present application, applied to an embankment condition.

[0109] Description of reference numerals:

[0110] 1. Capping platform; 2. Pile cap; 3. Gasket; 4. Embedded plate; 5. Elastic plate; 6. Bottom plate; 7. Replaceable filler; 8. Pile; 9. Pile end adaptive deformer; 10. Roadbed; 11. Abutment structure; 12. Bridge deck.

[0111] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0112] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0113] The technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0114] See also Figure 1 The embodiment of the present application provides a composite pile foundation structure for optimizing the pavement stiffness of a highway transition section, comprising a cap 1, a pile cap 2, a gasket 3, an embedding plate 4, an elastic plate 5, a bottom plate 6, a replaceable filler 7, a pile 8, and a pile end adaptive deformer 9. The cap 1 is embedded and connected with the elastic composite plate. The embedding plate 4, the elastic plate 5, and the bottom plate 6 together form an elastic composite plate from top to bottom. The elastic composite plate is compressed and deformed during the construction stage to pre-apply negative friction to the pile. The elastic composite plate is located above the replaceable filler 7. The control variables of the replaceable filler 7 include depth, compression modulus, and ultimate lateral friction. The spacing between each pile 8 is 6.5 times the pile diameter or more. The pile 8 exerts its ultimate bearing capacity in a normal working state. The pile 8 is connected to a pile cap 2 and a pile end adaptive deformer 9 at the top and end, respectively. The elastic modulus of the pile end adaptive deformer 9 is 0.1 kPa. The force transmission path of the composite pile foundation structure is: the load on the cap 1 is first transmitted to the replaceable filler 7, then to the pile 8, and finally to the replaceable filler 7.

[0115] In some embodiments, the pile 8 has negative friction. The negative friction is pre-applied. This embodiment provides a method for pre-applying negative friction to the pile, the steps of which include:

[0116] Step 1: horizontally install the elastic composite panel;

[0117] Step 2, setting the initial controlled compression deformation value of the elastic composite plate;

[0118] Step 3, stacking a weight on the embedded plate 4 to pre-compress the elastic composite plate to a target compression depth;

[0119] Step 4, completing the construction of all piles 8;

[0120] Step 5: remove the heavy objects on the embedded plate 4.

[0121] See also Figure 5 , is a schematic diagram of a composite pile foundation structure for optimizing the pavement stiffness of a highway transition section provided in an embodiment of the present application, which is applied to a bridge abutment pile foundation working condition. The present application embodiment provides a design and use method for a bridge abutment pile foundation, so as to design a composite pile foundation structure that can be applied to a bridge abutment pile foundation working condition, and the design and use method comprises the following steps:

[0122] S51. According to the roadbed design and construction plan, the highway grade and the standard value of the vehicle uniform load q are determined, and the filling height H of the fill when constructing one side of the roadbed is determined. t , the height after preloading construction H y , the width of the roadbed is B; the distance of half the span of the bridge is L; the gravity of the elastic composite plate is Q1, and the elastic deformation coefficient is K1.

[0123] S52. Preliminarily determine the width of the abutment on one side of the abutment pile foundation as a, the length of the abutment along the driving direction as b, the non-vehicle load borne by the abutment and the abutment as Q2, and the standard value of the ultimate bearing capacity of the replaceable filling material as f. oa , check whether the foundation bearing capacity satisfaction rate is greater than 0.5:

[0124]

[0125] S53. Taking the vehicle load on the road surface as the independent variable, a calculation function for the post-construction settlement of the road surface on one side of the roadbed is established:

[0126] S L (q) = S C (q)+S S (q)+S E -s GC1

[0127] Among them, S C (q) represents the function of the subgrade deformation value with respect to the road vehicle load, S S (q) represents the function of foundation settlement value with respect to road vehicle load, S E It represents the self-compaction settlement value caused by the embankment fill load, s GC1This is the construction settlement on one side of the roadbed.

[0128] S C (q) is calculated as follows:

[0129] k is the total number of soil layers of the embankment fill, α zi The average vertical additional stress coefficient of the i-th layer of soil, E sti Compression modulus of the ith layer of embankment fill, H i is the thickness of the i-th fill layer of the embankment.

[0130] S S (q) is calculated as follows:

[0131]

[0132] Among them, α z is the average additional stress coefficient of vehicle load on the bottom of the roadbed, Z i is the distance from the roadbed surface to the i-th soil layer, is the average additional stress coefficient from the roadbed surface to the i-th soil layer, which is taken according to Article J.0.2 of the Code for Design of Highway Bridge and Culvert Foundations, σ z2 It is the average additional stress caused by roadbed fill on the bottom of roadbed.

[0133] S E The calculation formula is as follows:

[0134] γ i is the fill weight of the ith layer of the embankment;

[0135] s GC1 The calculation formula is as follows:

[0136] s GC1 =H t -H y

[0137] S54. Taking the vehicle load on the road surface as the independent variable, establish the calculation function of the post-construction settlement of the road surface on one side of the abutment pile foundation:

[0138] S q (q)=ψ q [S t (q)+S sp ]+S K (q)-s GC2

[0139] In the formula, ψ q It is the correction factor for settlement calculation. In the absence of empirical value, it is taken as 1. t (q) is the function of the settlement of the elastic composite plate bottom plate 6 under additional pressure with respect to the road vehicle load, Ssp is the settlement caused by the interaction between pile and soil, S K (q) is the total compression of the elastic composite plate, s GC2 This is the construction settlement on one side of the abutment.

[0140] S t (q) is calculated as follows:

[0141]

[0142] Where η p is the influence coefficient of pile penetration deformation; when the bearing layer at the pile end is sand, silt, and clay, the values ​​are 1, 1.15, and 3 respectively; x is the initial controlled compression deformation value of the elastic composite plate, n is the number of piles arranged in the abutment pile foundation; m is the number of soil layers included in the calculation depth, and the settlement calculation depth is calculated according to σ z =0.1σ c Determine, σ z is the additional stress, σ c is the vertical soil stress; E si is the compression modulus of the i-th layer of soil; p0 is the additional stress of the elastic composite plate bottom plate 6; q sik is the ultimate lateral friction resistance, d is the diameter of the pile, k is the number of soil layers within the length of the pile; σ3 is the additional vertical stress of the backfill on the pile end plane; Z i is the distance from the roadbed surface to the i-th soil layer; It is the average additional stress coefficient from the subgrade surface to the i-th soil layer, and is taken according to Article J.0.2 of the Code for Design of Highway Bridge and Culvert Foundations.

[0143] S sp The calculation formula is as follows:

[0144]

[0145] In the formula, l i is the thickness of the i-th soil layer, l is the pile length,

[0146] S K (q) The calculation method is as follows:

[0147]

[0148] s GC2 The calculation formula is as follows:

[0149]

[0150] In the formula, ψ SC is the settlement correction factor, P G =Q1+Q2,Be is the basic equivalent width, ν s is the weighted Poisson's ratio of the soil within the pile length range under the elastic composite plate bottom plate 6, E0 is the average elastic modulus within the pile length range, C is the settlement influence coefficient of the pile group, which can be calculated according to the "Handbook of Pile Foundation Engineering", A e A is the effective load-bearing area of ​​the cap area minus the pile area. e =A-nπ(K P d) 2 / 4,K P The general value is 1.5.

[0151] S55. The seven unknown basic design parameters are as follows: pile length l, pile diameter d, pile number n, initial controlled compression deformation value x of the elastic composite plate, thickness h of the replaceable filler 7, and ultimate lateral friction resistance q of the replaceable filler 7. s1k , compression modulus E of replaceable filler 7 s1 The standard value of the uniformly distributed vehicle load q is divided into 7 levels starting from 0, namely 0, q1, q2, q3, q4, q5, and q6, and a group of control equations for the overall deformation of the road surface is established.

[0152]

[0153] Among them, S L (0), S L (q1), S L (q2), S L (q3), S L (q4), S L (q5), S L (q6) represents the post-construction settlement of the road surface on one side of the roadbed under the standard values ​​of vehicle uniform load of 0, q1, q2, q3, q4, q5, and q6, respectively. q (0), S q (q1), S q (q2), S q (q3), S q (q4), S q (q5), S q (q6) represents the post-construction settlement of the road surface on one side of the abutment under the standard values ​​of vehicle uniformly distributed load of 0, q1, q2, q3, q4, q5 and q6 respectively.

[0154] S56. Solve the pavement overall deformation control equations to obtain basic design combination parameters.

[0155] S57, basic design combination parameter verification, the process is as follows:

[0156] S571. Verify the overall bearing capacity safety factor. The overall bearing capacity safety factor K should be no less than 2:

[0157]

[0158] S572, Pile spacing verification: The basic design combination parameters are required to meet the pile spacing greater than 6.5 times the pile diameter under the bottom size of the elastic composite plate;

[0159] S573, Verification of symmetrical arrangement principle: The arrangement of abutment pile foundations should be symmetrical along the roadbed section and the longitudinal direction of the roadbed;

[0160] S574. Verification of post-construction settlement: The allowable post-construction settlement shall meet the requirements of Table 7.7.1-2 of the Highway Subgrade Design Specifications (JTG D30-2015).

[0161] S58: Obtain the final zero differential settlement design combination parameters.

[0162] See also Figure 6 , is a schematic diagram of a composite pile foundation structure for optimizing the pavement stiffness of a highway transition section provided in an embodiment of the present application, applied to an embankment condition. The present application embodiment provides a design and use method for a highway foundation, so as to design a composite pile foundation structure that can be applied to an embankment condition, comprising the following steps:

[0163] S61. According to the roadbed design and construction plan, the highway grade and the standard value of the vehicle uniform load q are determined, the length of the transition section is L1, and the initial height of the fill during construction on one side of the roadbed is H. t , fill height after preloading construction H y , the width of the roadbed and pavement is B; the length of the elastic composite plate is A, the width is B, the gravity is Q1, and the elastic deformation coefficient is K1;

[0164] S62, specify the bearing weight Q3, the total amount of fill in the transition section is Q4, and the bearing capacity of the foundation for replaceable filler is f oa Verify whether the foundation bearing capacity satisfaction rate is greater than 0.5:

[0165]

[0166] S63. Taking the vehicle load on the road surface as the independent variable, establish the calculation function of the post-construction settlement of the road surface on one side of the roadbed:

[0167] S L (q) = S C (q)+S S (q)+S E -s GC3

[0168] Among them, S C(q) represents the function of the subgrade deformation value with respect to the road vehicle load, S S (q) represents the function of composite foundation settlement value with respect to road vehicle load, S E It represents the self-compaction settlement value caused by the embankment fill load, s GC3 For construction settlement;

[0169] S C (q) is calculated as follows:

[0170] k is the total number of soil layers of the embankment fill, α zi is the average vertical additional stress coefficient of the i-th layer of soil, E sti Compression modulus of the ith layer of embankment fill, H i is the thickness of the i-th fill layer of the embankment;

[0171] S S (q) is calculated as follows:

[0172] S S (q)=ψ l [S t (q)+S sp ]+S K (q); ψ l Correction factor for settlement calculation; S t (q) is the function of the elastic composite plate bottom plate settlement with respect to the road vehicle load, p0 is the additional stress of the elastic composite plate bottom plate 6; η p is the influence coefficient of pile penetration deformation. When the bearing layer at the pile end is sand, silt, and clay, the values ​​are 1, 1.15, and 3, respectively. x is the initial controlled compression deformation value of the elastic composite plate. n is the number of piles arranged in the composite foundation. m is the number of soil layers included in the calculation depth. The settlement calculation depth is calculated according to σ z =0.1σ c Determine, σ z is the additional stress, σ c is the vertical soil stress, E si is the compression modulus of the i-th layer of soil, q sik is the limiting lateral friction, d is the diameter of the pile, k is the number of soil layers within the length of the pile, and Z i is the distance from the elastic composite plate bottom plate 6 to the i-th soil layer, is the average additional stress coefficient from the elastic composite plate bottom plate 6 to the i-th soil layer, which is taken according to Article J.0.2 of the Code for Design of Highway Bridge and Culvert Foundations; S sp is the settlement caused by the interaction between pile and soil. l i is the thickness of the i-th soil layer, l is the pile length, S K (q) is the total compression of the elastic composite plate,

[0173]

[0174] S E The calculation formula is as follows:

[0175] γ i is the fill weight of the ith layer of the embankment;

[0176] s GC3 The calculation formula is as follows:

[0177] ψ SC is the settlement correction factor,

[0178] P G =Q1+Q3+Q4, B e is the basic equivalent width, ν s is the weighted Poisson's ratio of the soil within the pile length range under the elastic composite plate bottom plate 6, E0 is the average elastic modulus within the pile length range, C is the settlement influence coefficient of the pile group, which can be calculated according to the "Handbook of Pile Foundation Engineering", A e The effective load-bearing area is the area of ​​the cap minus the area of ​​the pile.

[0179] A e =A-nπ(K P d) 2 / 4,K P The general value is 1.5;

[0180] S64. According to the geological survey, the reasonable design range of pile length shall be determined. According to the type of pile, the reasonable design range of pile diameter shall be determined. The requirement for post-construction settlement of the transition section pavement shall be [s]. The seven unknown basic design parameters shall be determined as follows: pile length l, pile diameter d, number of piles n, initial controlled compression deformation value x of the elastic composite plate, thickness h of the replaceable filler, and ultimate lateral friction resistance q of the replaceable filler. s1k , compression modulus E of replaceable filler 7 s1 , establish the inequality group for controlling the post-construction settlement of the roadbed and pavement:

[0181]

[0182] In the formula, l min represents the minimum designable pile length, l max The minimum designable pile length, d min The minimum designable pile diameter, d max represents the minimum designable pile diameter, ··· represents other design requirements;

[0183] S65, solving the settlement control inequality group to obtain the basic design combination parameters;

[0184]

[0185] In the formula, each row of parameters represents each set of basic design combination parameters calculated;

[0186] S66, basic design combination parameter verification, the process is as follows:

[0187] S661. Verify the overall bearing capacity safety factor. The overall bearing capacity safety factor K should be no less than 2:

[0188]

[0189] S662, Pile spacing verification: The basic design combination parameters are required to meet the pile spacing greater than 6.5 times the pile diameter under the bottom size of the elastic composite plate;

[0190] S663. Verification of symmetrical layout principle: The pile layout of the composite foundation should be symmetrical along the center line of the road surface.

[0191] S67, establishing a cost function;

[0192] M=Cnπr 2 l+Dnπr 2 +EABh+FAB+GABH c +M q

[0193] In the formula, the unit of C is yuan / m 3 , represents the cost of pile 8 material per cubic meter; the unit of D is yuan / m 2 , represents the cost of the pile end adaptive deformer 9 per square meter; the unit of E is yuan / m 3 , represents the cost of replaceable filler 7 per cubic meter; the unit of F is yuan / m 2 , represents the cost of elastic composite board per square meter; the unit of G is yuan / m 3 , represents the cost of material per cubic meter of foundation, H c is the average thickness of the platform 1; M q Indicates other costs.

[0194] S68. Calculate the minimum construction cost based on the basic design combination parameters;

[0195]

[0196] Among them, M min Represents the minimum construction cost, represented by M1, M2, and M3.

[0197] S69. Obtain the optimal design combination parameters.

[0198] The various embodiments or implementation methods in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the various embodiments can be referenced to each other.

[0199] It should be noted that the phrases "one embodiment", "an embodiment", "an exemplary embodiment", "some embodiments", etc. mentioned in the specification indicate that the described embodiments may include certain features, structures or characteristics, but not every embodiment may include the certain features, structures or characteristics. In addition, such phrases do not necessarily refer to the same embodiment. In addition, when describing certain features, structures or characteristics in conjunction with an embodiment, it is within the knowledge of those skilled in the art to implement such features, structures or characteristics in conjunction with other embodiments, whether explicitly or not explicitly described.

[0200] In general, terms should be understood, at least in part, by the context in which they are used. For example, the term "one or more" as used herein may be used to describe any feature, structure, or characteristic in a singular sense, or may be used to describe a combination of features, structures, or characteristics in a plural sense, depending, at least in part, on the context. Similarly, terms such as "a," "an," or "the" may also be understood to convey singular usage or to convey plural usage, depending, at least in part, on the context.

[0201] It should be easily understood that “on,” “above,” and “over” in the present disclosure should be interpreted in the broadest manner, so that “on” not only means “directly on something,” but also includes the meaning of “on something” with intervening features or layers therebetween, and “above” or “over” not only includes the meaning of “above” or “over,” but also may include the meaning of “above” or “over something” with no intervening features or layers therebetween (i.e., directly on something).

[0202] In addition, spatially relative terms, such as "below," "below," "beneath," "above," "above," etc., may be used herein for ease of description to describe the relationship of one element or feature relative to other elements or features as shown in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation shown in the figures. The device may have other orientations (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein may likewise be interpreted accordingly.

[0203] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A composite pile foundation structure for optimizing the pavement stiffness of a highway transition section, characterized in that: It includes a cap, a pile cap, an elastic composite plate, a replaceable filler, a pile and a pile end adaptive deformer; The cap is embedded and connected with the elastic composite plate. The elastic composite plate is compressed and deformed during the construction stage to apply negative friction to the pile in advance. The elastic composite plate is located on the replaceable material. The replaceable filler is selected according to the parameters calculated by the deformation control equation. The control variables of the replaceable filler include depth, compression modulus, and ultimate side friction. The pile is arranged in plurality, and the spacing between each pile is at least 6.5 times the pile diameter. The pile exerts its ultimate bearing capacity in normal working state. The pile is connected to the pile cap and the pile end adaptive deformer at the top and end respectively.

2. The composite pile foundation structure for optimizing the road surface stiffness of a highway transition section according to claim 1, characterized in that: The elastic deformation coefficient of the elastic composite plate is in the range of 0.3GPa to 0.9GPa. The elastic composite plate is in the elastic stage when in use. The elastic composite plate includes an embedded plate, an elastic plate and a bottom plate. The upper surface of the embedded plate is provided with transverse grooves and longitudinal grooves. The embedded plate is embedded and connected to the base. The elastic plate is located between the embedded plate and the bottom plate. The elastic plate is rigidly connected to the embedded plate and the bottom plate.

3. The composite pile foundation structure for optimizing the road surface stiffness of a highway transition section according to claim 1, characterized in that: The pile has negative friction.

4. The composite pile foundation structure for optimizing the road surface stiffness of a highway transition section according to claim 1, characterized in that: The pile cap is arranged on the top of the pile, the pile end adaptive deformer is arranged at the end of the pile, a gasket is arranged under the pile cap, and the pile passes through the elastic composite plate and the replaceable material and extends into the cap and the replaceable filler.

5. The composite pile foundation structure for optimizing the road surface stiffness of a highway transition section according to claim 1, characterized in that: The replaceable filler is used to share the upper load increment after the pile exerts its ultimate bearing capacity to prevent rapid settlement and deformation.

6. The composite pile foundation structure for optimizing the road surface stiffness of a highway transition section according to claim 1, characterized in that: The elastic deformation coefficient of the pile end adaptive deformer is 0.1 kPa, the thickness of the pile end adaptive deformer is 0.2 m, and the pile end adaptive deformer generates adaptive deformation according to the upper load.

7. The composite pile foundation structure for optimizing the road surface stiffness of a highway transition section according to claim 3, characterized in that: The composite pile foundation structure has a force transmission path and a force transmission stage; wherein the force transmission path is: the load on the upper part of the cap is first transmitted to the replaceable filler, then to the pile, and finally to the replaceable filler; The force transmission stage includes: Stage 1: The load increment on the upper part of the cap is completely offset by the negative friction, the upper load is completely shared by the replaceable filler, and the bearing capacity of the pile is not fully exerted; The second stage: The load increment on the upper part of the cap is completely shared by the piles, and the piles begin to exert their bearing capacity. The replaceable filler always shares the load of the absolute value of the total negative friction resistance pre-added during the construction stage; The third stage: The load increment on the upper part of the foundation is completely borne by the replaceable filling material, the pile is in an elastic support state, the bearing capacity of the pile is fully exerted, and the replaceable filling material shares the set load.

8. A design and use method for abutment pile foundation, characterized in that: A composite pile foundation structure for optimizing the pavement stiffness of a highway transition section according to any one of claims 1 to 7, comprising: Step 1: According to the roadbed design and construction plan, determine the highway grade and the standard value of the vehicle uniform load as q, and the filling height of the fill on one side of the roadbed as H. t , the height after preloading construction is H y , the width of the roadbed is B, the distance of half the span of the bridge is L, the gravity of the elastic composite plate is Q1, and the elastic deformation coefficient is K1; Step 2: Preliminarily determine the width of the abutment on one side of the abutment pile foundation, the length of the abutment along the driving direction, the non-vehicle load Q2 borne by the abutment and the abutment, and the standard value of the ultimate bearing capacity of the replaceable filler, f. oa , check whether the foundation bearing satisfaction rate is greater than 0.5 through the following formula: Among them, ψ represents the foundation bearing satisfaction rate; Step 3: Taking the vehicle load on the road surface as the independent variable, establish the post-construction settlement calculation function of the road surface on one side of the roadbed: S L (q)=S C (q)+S S (q)+S E -s GC1 Among them, S L (q) represents the calculation function of the post-construction settlement of the road surface on one side of the roadbed, S C (q) represents the function of the subgrade deformation value with respect to the road vehicle load, S S (q) represents the function of foundation settlement value with respect to road vehicle load, S E It represents the self-compaction settlement value caused by the embankment fill load, s GC1 It is the construction settlement on one side of the roadbed; S C (q) is calculated as follows: Among them, k is the total number of soil layers of embankment fill, α zi is the average vertical additional stress coefficient of the i-th layer of fill, E sti is the compression modulus of the i-th layer of embankment fill, H i is the thickness of the i-th fill layer of the embankment; S S (q) is calculated as follows: Among them, α z is the average additional stress coefficient of vehicle load on the bottom of the roadbed, z i-1 and Z i is the distance from the roadbed surface to the i-1th and ith soil layers, and are the average additional stress coefficients from the roadbed surface to the i-1th layer and the i-th layer of soil, σ z2 is the average additional stress of the roadbed fill on the bottom of the roadbed; S E The calculation formula is as follows: Among them, γ i-1 and γ i H is the fill weight of the i-1th and i-th layers of the embankment; i-1 is the thickness of the i-1th layer of fill in the embankment; s GC1 The calculation formula is as follows: s GC1 =H t -H y Step 4: Taking the vehicle load on the road surface as the independent variable, establish the post-construction settlement calculation function of the road surface on one side of the abutment pile foundation: S q (q)=ψ q [S t (q)+S sp ]+S K (q)-s GC2 Among them, ψ q It is the correction factor for settlement calculation. In the absence of empirical value, it is taken as 1. t (q) is the function of the settlement of the elastic composite plate under additional pressure on the road surface vehicle load, S sp is the settlement caused by the interaction between pile and soil, S K (q) is the total compression of the elastic composite plate, s GC2 It is the construction settlement on one side of the abutment; S t (q) is calculated as follows: Among them, η p is the influence coefficient of pile penetration deformation, and its values ​​are 1, 1.15, and 3 respectively when the bearing layer at the pile end is sand, silt, and clay; x is the initial controlled compression deformation value of the elastic composite plate, n is the number of piles arranged in the abutment pile foundation; m is the number of soil layers included in the calculation depth, and the settlement calculation depth is calculated according to σ z =0.1σ c Determine, σ z is the additional stress, σ c is the vertical soil stress; E si is the compression modulus of the i-th layer of soil; p0 is the additional stress of the bottom plate of the elastic composite plate; q sik is the limit lateral friction resistance, d is the diameter of the pile, k is the number of soil layers within the length of the pile; σ3 is the additional vertical stress of the backfill on the pile end plane; S sp The calculation formula is as follows: In the formula, It represents the average lateral friction weighted by thickness within the pile body. It represents the average compression modulus within the pile body, l i is the thickness of the i-th soil layer, l is the pile length, S K (q) The calculation method is as follows: s GC2 The calculation formula is as follows: Among them, ψ SC is the settlement correction factor, P G =Q1+Q2,B e is the base equivalent width, ν s is the weighted Poisson's ratio of the soil within the pile length range under the elastic composite plate bottom plate, E0 is the average elastic modulus within the pile length range, C is the settlement influence coefficient of the pile group, and A e It is the effective load-bearing area obtained by deducting the pile area from the base area; Step 5: Determine the seven unknown basic design parameters: pile length l, pile diameter d, pile number n, initial controlled compression deformation value x of the elastic composite plate, thickness h of the replaceable filler, and limit lateral friction resistance q of the replaceable filler. s1k , compression modulus E of replaceable filler s1 , the standard value of the uniformly distributed vehicle load q is divided into 7 levels starting from 0, namely 0, q1, q2, q3, q4, q5, q6, and the overall deformation control equations of the road surface are established: Among them, S L (0), S L (q1), S L (q2), S L (q3), S L (q4), S L (q5), S L (q6) represents the post-construction settlement of the road surface on one side of the roadbed under the standard values ​​of vehicle uniform load of 0, q1, q2, q3, q4, q5, and q6, respectively. q (0), S q (q1), S q (q2), S q (q3), S q (q4), S q (q5), S q (q6) represents the post-construction settlement of the road surface on one side of the abutment under the standard values ​​of uniformly distributed vehicle load of 0, q1, q2, q3, q4, q5, and q6 respectively; Step 6, solving the pavement overall deformation control equation group to obtain basic design combination parameters; Step 7: Verify the basic design combination parameters, including: Verify the overall bearing capacity safety. The overall bearing capacity safety K should be no less than 2: Pile spacing verification: The basic design combination parameters are required to meet the requirement that the pile spacing is greater than 6.5 times the pile diameter under the bottom size of the elastic composite plate; Verification of symmetrical arrangement principle: The arrangement of abutment pile foundations should be symmetrical along the roadbed section and the longitudinal direction of the roadbed; Step 8: Obtain the final zero differential settlement design combination parameters.

9. A design and use method for highway foundation, characterized in that: A composite pile foundation structure for optimizing the pavement stiffness of a highway transition section according to any one of claims 1 to 7, comprising: Step 1: According to the roadbed design and construction plan, determine the highway grade and the standard value of the vehicle uniform load q, the length of the transition section L1, and the initial height H of the fill when constructing one side of the roadbed t , fill height after preloading construction H y , roadbed and pavement width B, length A of elastic composite plate, width B of elastic composite plate, gravity Q1 of elastic composite plate, elastic deformation coefficient K1; Step 2: Determine the bearing weight Q3, the total amount of transition section roadbed fill Q4, and the bearing capacity of the replaceable material foundation f oa Verify whether the foundation bearing capacity satisfaction rate is greater than 0.5: In the formula, ψ1 is the foundation bearing satisfaction rate; Step 3: Taking the vehicle load on the road surface as the independent variable, establish the post-construction settlement calculation function of the road surface on one side of the roadbed: S L (q)=S C (q)+S S (q)+S E -s GC3 Among them, S C (q) represents the function of the subgrade deformation value with respect to the road vehicle load, S S (q) represents the function of composite foundation settlement value with respect to road vehicle load, S E It represents the self-compaction settlement value caused by the embankment fill load, s GC3 For construction settlement; S C (q) is calculated as follows: Among them, k is the total number of soil layers of embankment fill, α zi is the average vertical additional stress coefficient of the i-th layer of soil, E sti Compression modulus of the i-th layer of embankment fill, H i is the thickness of the i-th fill layer of the embankment; S S (q) is calculated as follows: S S (q)=ψ[S t (q)+S sp ]+S K (q) Where ψ is the settlement calculation correction coefficient; S t (q) is the function of the bottom settlement of the elastic composite slab with respect to the road vehicle load, p0 is the additional stress of the bottom plate of the elastic composite plate; η p is the influence coefficient of pile penetration deformation. When the bearing layer at the pile end is sand, silt, and clay, the values ​​are 1, 1.15, and 3, respectively. x is the initial controlled compression deformation value of the elastic composite plate. n is the number of piles arranged in the composite foundation. m is the number of soil layers included in the calculation depth. The settlement calculation depth is calculated according to σ z =0.1σ c Determine, σ z is the additional stress, σ c is the vertical soil stress, E si is the compression modulus of the i-th layer of soil, q sik is the limiting lateral friction, d is the diameter of the pile, k is the number of soil layers within the length of the pile, and Z i is the distance from the bottom of the elastic composite plate to the i-th soil layer, is the average additional stress coefficient from the bottom of the elastic composite plate to the i-th soil layer; S sp is the settlement caused by the interaction between pile and soil. l i is the thickness of the i-th soil layer, l is the pile length, S K (q) is the total compression of the elastic composite plate, S E The calculation formula is as follows: Among them, γ i-1 and γ i H is the fill weight of the i-1th and i-th layers of the embankment; i-1 is the thickness of the i-1th layer of fill in the embankment; s GC3 The calculation formula is as follows: Among them, ψ SC is the settlement correction factor, P G =Q1+Q3+Q4, B e is the base equivalent width, ν s is the weighted Poisson's ratio of the soil within the pile length range under the elastic composite plate bottom plate, E0 is the average elastic modulus within the pile length range, C is the settlement influence coefficient of the pile group, and A e It is the effective load-bearing area obtained by deducting the pile area from the base area; Step 4: Determine the reasonable design range of pile length according to geological survey conditions, and determine the reasonable design range of pile diameter according to pile type; determine the post-construction settlement requirement of transition section pavement as [s]; determine the seven unknown basic design parameters: pile length l, pile diameter d, number of piles n, initial controlled compression deformation value x of elastic composite plate, thickness h of replaceable filler, and limit lateral friction resistance q of replaceable filler s1k , compression modulus E of replaceable filler s1 , establish the inequality group for overall deformation control of roadbed and pavement: In the formula, l min represents the minimum designable pile length, l max The minimum designable pile length, d min The minimum designable pile diameter, d max represents the minimum designable pile diameter, ··· represents other design requirements; Step 5: Solve the settlement control inequality group to obtain the basic design combination parameters; In the formula, each row of parameters represents each set of basic design combination parameters calculated; Step 6: Verify basic design combination parameters, including: Verify the overall bearing capacity safety, the overall bearing capacity safety K is guaranteed to be no less than 2: Pile spacing verification: The basic design combination parameters are required to meet the requirement that the pile spacing is greater than 6.5 times the pile diameter under the bottom size of the elastic composite plate; Verification of symmetrical layout principle: The pile layout of composite foundation should be symmetrical along the center line of the road surface; Step 7: Establish cost function; M=Cnπr 2 l+Dnπr 2 +EABh+FAB+GABH c +M q In the formula, C represents the cost of pile material per cubic meter, unit: yuan / m 3 ; D represents the cost of the pile end adaptive deformer per square meter, unit: yuan / m 3 ; E represents the cost of replaceable materials per cubic meter, unit: yuan / m 3 ; F represents the local cost of elastic composite board per square meter, unit: yuan / m 3 ; G represents the cost of the foundation material per cubic meter, unit: yuan / m 3 ;H c is the average thickness of the cap; M q represents other costs; Step 8. Calculate the minimum construction cost based on the basic design combination parameters: Among them, M min Indicates the minimum construction cost, M1, M2, M3, M k They represent the construction costs under the first set of basic design parameters, the second set of basic design parameters, the third set of basic design parameters, and the kth set of basic design parameters respectively; Step 9: Obtain the optimal design combination parameters.

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