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] This application relates to the field of composite pile foundation technology, and in particular to a composite pile foundation structure for optimizing the pavement stiffness of highway transition sections and its design and application method. Background Technology

[0002] Differential settlement at the transition section between roads and bridges has been a long-standing problem. For bridge abutment pile foundations, the stiffness on one side of the abutment actually has a large redundancy. Existing methods usually consider increasing the stiffness on the roadbed side to reduce differential settlement of the road surface in the transition section. However, these methods are not easy to control the stiffness precisely and are very costly. There is currently no structure or method to reduce the stiffness on the abutment side.

[0003] Furthermore, the existing design of bridge abutment pile foundations is out of touch with the deformation characteristics of the roadbed. Under the action of reciprocating traffic loads in the later stages, misalignment still exists, and zero differential settlement has not yet been theoretically achieved.

[0004] For roadbed settlement control, the settlement deformation of the foundation accounts for a large proportion. Usually, a relatively dense pile layout is used to reduce 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 high costs.

[0005] For piles, negative skin friction is generally considered an unfavorable factor and has not been properly utilized. Summary of the Invention

[0006] This application provides a composite pile foundation structure and its design and application method for optimizing the pavement stiffness of highway transition sections. It rationally utilizes the negative skin friction of the piles. The load transmission path on the upper part of the pile cap is as follows: the load on the upper part of the pile cap is first transmitted to the replaceable fill material, then to the piles, and finally to the replaceable fill material. The piles fully exert their bearing capacity under normal working conditions. For abutment pile foundations, the overall stiffness is reduced. The abutment pile foundation design is guided by the load settlement characteristics on one side of the roadbed, achieving zero-differential settlement between the abutment and the roadbed transition section. For embankment foundations, precise control of the settlement of the roadbed transition section is achieved, reducing the use of piles and allowing the soil between piles to share more of the load, thus reducing settlement and saving construction costs. This structure and its design and application method provide assurance for the safety, comfort, and smoothness of highway vehicle travel.

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

[0008] The pile cap is embedded in the elastic composite plate. The elastic composite plate undergoes compression deformation during construction to pre-apply negative skin friction to the pile. The elastic composite plate is located on a replaceable material. The replaceable filler is selected based on parameters calculated according to the deformation control equation. The control variables of the replaceable filler include depth, compression modulus, and ultimate side skin friction. Multiple piles are configured, and the spacing between each pile is at least 6.5 times the pile diameter. The piles exert their ultimate bearing capacity under normal working conditions. The pile cap and the pile end adaptive deformer are connected to the top and end of the pile, respectively.

[0009] Furthermore, the elastic deformation coefficient of the elastic composite plate ranges from 0.3 GPa to 0.9 GPa. The elastic composite plate is in the elastic stage during use. The elastic composite plate includes a fixed plate, an elastic plate, and a base plate. The upper surface of the fixed plate is provided with a horizontal groove and a vertical groove. The fixed plate is fixedly connected to the support platform. The elastic plate is located between the fixed plate and the base plate. The elastic plate is rigidly connected to the fixed plate and the base plate.

[0010] Furthermore, the pile has negative skin friction.

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

[0012] Furthermore, the replaceable filler is used to share the incremental load from the upper part after the pile has reached its ultimate bearing capacity, preventing rapid settlement 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 pile cap is first transmitted to the replaceable fill material, then to the pile, and finally to the replaceable fill material.

[0015] The force transmission stage includes:

[0016] Phase 1: The increase in load on the upper part of the pile cap is completely offset by the negative skin friction, and the upper load is completely shared by the replaceable fill material, so the bearing capacity of the pile is not utilized.

[0017] Second stage: The load increment on the upper part of the pile cap is completely shared by the piles, the piles begin to exert their bearing capacity, and the replaceable fill material always shares the load of the total negative skin resistance pre-added during the construction stage.

[0018] Phase 3: The load increment on the upper part of the pile cap is entirely shared by the replaceable filler, the pile is in an elastic support state, the bearing capacity of the pile is fully utilized, and the replaceable filler shares the set load.

[0019] Secondly, this application provides a design and usage method for bridge abutment pile foundations, used for designing composite pile foundation structures for optimizing pavement stiffness in highway transition sections as described in the first aspect, comprising:

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

[0021] Step 2: Initially determine the width 'a' of one side of the bridge abutment pile foundation, the length 'b' of the pile cap along the traffic direction, the pile cap and the non-vehicle load Q2 borne by the pile cap, and the standard value of the ultimate bearing capacity 'f' of the replaceable fill material. oa The following formula can be used to verify whether the foundation bearing capacity satisfaction rate is greater than 0.5:

[0022]

[0023] Wherein, ψ represents the foundation bearing capacity satisfaction rate;

[0024] Step 3: Using the vehicle load on the road surface as the independent variable, establish a post-construction settlement calculation function for 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 post-construction settlement calculation function for the pavement on one side of the roadbed, S C (q) represents the subgrade deformation value as a function of the road vehicle load, S S (q) represents the foundation settlement value as a function of the road vehicle load, S E s represents the self-compaction settlement value caused by the embankment fill load. GC1 Construction settlement on one side of the roadbed;

[0027] S C (q) is calculated using the following formula:

[0028]

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

[0030] S S (q) is calculated using the following formula:

[0031]

[0032] Where, α z z is the average additional stress coefficient of the vehicle load on the bottom of the roadbed. i-1 and Z i Let be the distance from the roadbed surface to the (i-1)th and i-th soil layers. and These are the average additional stress coefficients σi and σi, respectively, within the range from the subgrade surface to the (i-1)th and ith layers of soil. z2 This represents the average additional stress exerted by the roadbed fill on the bottom of the roadbed.

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

[0034]

[0035] Where, γ i-1 and γ i H represents the unit weight of the (i-1)th and i-th layers of fill in the embankment; i-1 The thickness of the (i-1)th 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: Using the vehicle load on the road surface as the independent variable, establish a post-construction settlement calculation function for the road surface on one side of the bridge abutment pile foundation:

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

[0040] Where, ψ q The correction factor for bridge abutment pavement settlement is calculated, and a value of 1 is taken in the absence of empirical values. t (q) is a function of the settlement of the elastic composite plate under the additional pressure on the bottom of the plate with respect to the road vehicle load, S spS represents the settlement caused by the interaction between the pile and the soil. K (q) represents the total compression of the elastic composite plate, s GC2 Construction settlement on one side of the bridge abutment;

[0041] S t (q) is calculated using the following formula:

[0042]

[0043] Where, η p σ represents the pile penetration deformation influence coefficient, with values ​​of 1, 1.15, and 3 for the pile tip bearing layers of sandy soil, silty soil, and cohesive soil, respectively; x represents the initial control compression deformation value of the elastic composite plate; n represents the number of piles arranged in the abutment pile foundation; m represents the number of soil layers included within the calculation depth, and the settlement calculation depth is based on σ. z =0.1σ c Determined, σ z For additional stress, σ c E represents vertical soil stress. si pi is the compression modulus of the i-th soil layer; p0 is the additional stress on the bottom plate of the elastic composite plate.

[0044] q sik σ3 represents the ultimate side friction resistance, d is the pile diameter, k is the number of soil layers within the pile length range, and σ3 is the additional vertical stress exerted by the backfill on the pile end plane.

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

[0046]

[0047] In the formula, This represents the thickness-weighted average side friction resistance within the pile body. l represents the average compression modulus within the pile body. i Let l be the thickness of the i-th soil layer and l be the pile length.

[0048] S K (q) is calculated as follows:

[0049]

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

[0051]

[0052] Where, ψ SC P is the settlement correction factor for pile foundation construction. G =Q1+Q2, B e Based on the equivalent width,

[0053] ν s E0 is the weighted Poisson's ratio of the soil within the pile length range under the elastic composite slab base plate, C is the average elastic modulus within the pile length range, and A is the settlement influence coefficient of the pile group. e The effective load-bearing area is the area of ​​the pile cap minus the area of ​​the piles.

[0054] Step 5: Determine the 7 unknown basic design parameters as follows: pile length l, pile diameter d, number of piles n, initial control compression deformation value x of the elastic composite plate, thickness h of the replaceable filler, and ultimate side friction resistance q of the replaceable filler. s1k The compressive modulus E of replaceable fillers s1 The standard value of the uniformly distributed vehicle load q is divided into 7 levels with equal increments starting from 0: q1, q2, q3, q4, q5, and q6. A set of overall road deformation control equations is established:

[0055]

[0056] 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 pavement on one side of the roadbed under uniformly distributed vehicle loads 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 bridge abutment under the standard values ​​of 0, q1, q2, q3, q4, q5, and q6 of the uniformly distributed vehicle load;

[0057] Step 6: Solve the set of equations governing the overall deformation of the road surface to obtain the basic design combination parameters;

[0058] Step 7: Verify the basic design combination parameters, including:

[0059] The overall load-bearing capacity safety factor K should be not less than 2 for the overall load-bearing capacity safety factor verification.

[0060]

[0061] Pile spacing verification: The basic design combination parameters are required to ensure that the pile spacing is greater than 6.5 times the pile diameter under the bottom dimensions of the elastic composite plate;

[0062] Verification of the symmetrical layout principle: The layout of bridge abutment pile foundations should be symmetrical along both the roadbed cross section and the roadbed longitudinal direction;

[0063] Step 8: Obtain the final zero-difference settlement design combination parameters.

[0064] Thirdly, this application provides a design and usage method for highway subgrades, used to design composite pile foundation structures for optimizing pavement stiffness in highway transition sections as described in the first aspect, comprising:

[0065] Step 1: Based on the roadbed design and construction plan, determine the highway grade and the standard value q of the uniformly distributed vehicle load, the length L1 of the transition section, and clarify the initial height H of the fill during construction on one side of the roadbed. t The backfill height H after preloading construction y , roadbed and pavement width B, elastic composite plate length A, elastic composite plate width B, elastic composite plate weight Q1, elastic deformation coefficient K1;

[0066] Step 2: Determine the foundation weight Q3, the total fill volume of the transition section roadbed Q4, and the foundation bearing capacity f of the replaceable materials. oa Verify that the foundation bearing capacity meets the requirement of 0.5.

[0067]

[0068] In the formula, ψ1 is the foundation bearing capacity satisfaction rate;

[0069] Step 3: Using the vehicle load on the road surface as the independent variable, establish a post-construction settlement calculation function for the road surface on one side of the roadbed:

[0070] S L (q)=S C (q)+S S (q)+S E -s GC3

[0071] Among them, S C (q) represents the subgrade deformation value as a function of the road vehicle load, S S (q) represents the composite foundation settlement as a function of the road vehicle load, S E s represents the self-compaction settlement value caused by the embankment fill load. GC3 For construction settlement;

[0072] S C (q) is calculated using the following formula:

[0073]

[0074] Where k is the total number of soil layers in the embankment fill, α zi E is the average vertical additional stress coefficient of the i-th soil layer. sti The compression modulus of the i-th layer of embankment fill, H i Let be the thickness of the i-th layer of fill in the embankment;

[0075] S S (q) is calculated using the following formula:

[0076] S S (q)=ψ l [S t (q)+S sp ]+S K (q)

[0077] Where, ψ l Correction factors for subgrade and pavement settlement calculation; S t (q) is a function of the settlement of the bottom of the elastic composite plate with respect to the road vehicle load. p0 is the additional stress on the bottom plate of the elastic composite plate; η p The pile penetration deformation influence coefficient is denoted by σ, with values ​​of 1, 1.15, and 3 for the pile tip bearing layers of sand, silt, and cohesive soil, respectively. x represents the initial control compression deformation value of the elastic composite plate, n is the number of piles in the composite foundation, and m is the number of soil layers included within the calculation depth. The settlement calculation depth is based on σ. z =0.1σ c Determined, σ z For additional stress, σ c For vertical soil stress, E si Let be the compression modulus of the i-th soil layer. q sik Z represents the ultimate side skin friction, d is the pile diameter, k is the number of soil layers within the pile length range, and Z is the ultimate side skin friction. i Let be the distance from the bottom of the elastic composite panel to the i-th layer of soil. S is the average additional stress coefficient within the range from the bottom of the elastic composite plate to the i-th soil layer; sp Settlement caused by the interaction between the pile and the soil. l i Let l be the thickness of the i-th soil layer and l be the pile length. S K (q) represents the total compression of the elastic composite plate.

[0078] S E The calculation formula is as follows:

[0079]

[0080] Where, γ i-1and γ i H represents the unit weight of the (i-1)th and i-th layers of fill in the embankment; i-1 The thickness of the (i-1)th layer of fill in the embankment;

[0081] s GC3 The calculation formula is as follows:

[0082]

[0083] Where, ψ SC P is the settlement correction factor for pile foundation construction. G =Q1 + Q3 + Q4, B e Based on the equivalent width, ν s E0 is the weighted Poisson's ratio of the soil within the pile length range under the elastic composite slab base plate, C is the average elastic modulus within the pile length range, and A is the settlement influence coefficient of the pile group. e The effective load-bearing area is the area of ​​the pile cap minus the area of ​​the piles.

[0084] Step 4: Determine the reasonable design range of pile length based on geological exploration, and determine the reasonable design range of pile diameter based on pile type; determine the post-construction settlement requirement of the transition section pavement as [s]; determine the 7 unknown basic design parameters as follows: pile length l, pile diameter d, number of piles n, initial control compression deformation value x of elastic composite plate, thickness h of replaceable filler, and ultimate side friction resistance q of replaceable filler. s1k The compressive modulus E of replaceable fillers s1 Establish a set of inequalities for overall deformation control of roadbed and pavement:

[0085]

[0086] In the formula, l min Indicates the minimum designable pile length, l max d represents the minimum designable pile length. min d represents the minimum designable pile diameter. max Indicates the minimum designable pile diameter, ... indicates other design requirements;

[0087] Step 5: Solve the system of settlement control inequalities to obtain the basic design combination parameters;

[0088]

[0089] In the formula, each row of parameters represents the calculated parameters of each set of basic design combinations;

[0090] Step Six: Verification of basic design combination parameters, including:

[0091] Overall load-bearing capacity safety verification: The overall load-bearing capacity safety factor K is guaranteed to be no less than 2.

[0092]

[0093] Pile spacing verification: The basic design combination parameters are required to ensure that the pile spacing is greater than 6.5 times the pile diameter under the bottom dimensions of the elastic composite plate;

[0094] Verification of the symmetrical layout principle: The pile foundations of composite foundations should be laid out symmetrically along the centerline of the road surface;

[0095] Step 7: Establish the cost function;

[0096] M=Cnπr 2 l+Dnπr 2 +EABh+FAB+GABH c +M q

[0097] In the formula, C represents the cost of each cubic meter of pile material, in yuan / m. 3 D represents the cost per square meter of the adaptive deformer at the pile tip, in yuan / m. 2 E represents the cost of replaceable materials per cubic meter, in yuan / m³. 3 F represents the local cost per square meter of flexible composite panel, in yuan / m². 2 G represents the cost of material per cubic meter of foundation, in yuan / m. 3 H c M represents the average thickness of the foundation; q Other costs;

[0098] Step 8: After steps 6 and 7, the final number of basic design parameter combinations is obtained as k. Calculate the minimum construction cost based on these basic design parameter combinations:

[0099]

[0100] Among them, M min Indicates the minimum construction cost, M1, M2, M3, M k These represent the construction costs under the first group of basic design parameters, the second group of basic design parameters, the third group of basic design parameters, and the kth group of basic design parameters, respectively.

[0101] Step 9: Obtain the optimal design combination parameters.

[0102] This application provides a composite pile foundation structure and its design and application method for optimizing the pavement stiffness of highway transition sections. The structure utilizes an elastic composite plate to pre-apply negative skin friction during the compaction deformation phase of construction, effectively utilizing this negative skin friction. It increases the spacing between piles under the abutment, ensuring the piles operate at their ultimate bearing capacity. The use of replaceable filler controls pile settlement, allowing the piles and soil to share the superstructure load, reducing the overall stiffness of the composite pile foundation structure and significantly saving construction costs. For abutment pile foundation design, this application avoids excessive stiffness redundancy. Guided by the load characteristics on the roadbed side, it proposes a set of overall pavement deformation control equations, achieving zero-difference settlement control at the roadbed junction. For the composite pile foundation design of the roadbed, it uses precise settlement control as a design guide, proposing a set of overall pavement deformation control inequalities to maximize the pile's bearing capacity and significantly save construction costs. The structure and design method provided in this application ensure the safety, comfort, and smoothness of highway vehicle travel. Attached Figure Description

[0103] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0104] 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 this application;

[0105] Figure 2 A top view of a composite pile foundation structure for optimizing pavement stiffness in highway transition sections, provided in an embodiment of this application;

[0106] Figure 3 A side view of a composite pile foundation structure for optimizing pavement stiffness in highway transition sections, provided in an embodiment of this application;

[0107] Figure 4 A schematic diagram of a pile, pile cap, and 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 this application;

[0108] Figure 5 A schematic diagram illustrating the application of a composite pile foundation structure for optimizing the pavement stiffness of a highway transition section in the bridge abutment pile foundation condition, as provided in this application embodiment.

[0109] Figure 6 This is a schematic diagram illustrating the application of a composite pile foundation structure for optimizing the pavement stiffness of a highway transition section in embankment conditions, as provided in an embodiment of this application.

[0110] Explanation of reference numerals in the attached figures:

[0111] 1. Pier cap; 2. Pile cap; 3. Gasket; 4. Embedded plate; 5. Elastic plate; 6. Base plate; 7. Replaceable filler; 8. Pile; 9. Pile end adaptive deformer; 10. Subgrade; 11. Abutment structure; 12. Bridge deck.

[0112] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0113] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0114] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0115] Please see Figure 1 This application provides a composite pile foundation structure for optimizing the pavement stiffness of highway transition sections, including a pile cap 1, a pile cap 2, a gasket 3, a retaining plate 4, an elastic plate 5, a base plate 6, replaceable filler 7, piles 8, and a pile end adaptive deformer 9. The pile cap 1 is embedded and connected to the elastic composite plate. The retaining plate 4, the elastic plate 5, and the base plate 6 together form the elastic composite plate from top to bottom. During the construction stage, the elastic composite plate undergoes compression deformation to pre-apply negative skin friction to the piles. The elastic composite plate is located on top of the replaceable filler 7. The control variables of the replaceable filler 7 include depth, compression modulus, and ultimate side skin friction. The spacing between each pile 8 is 6.5 times the pile diameter or more. The piles 8 exert their ultimate bearing capacity under normal working conditions. The pile cap 2 and the pile end adaptive deformer 9 are connected to the top and end of the piles 8, 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 as follows: the load on the upper part of the pile cap 1 is first transmitted to the replaceable filler 7, then to the piles 8, and finally to the replaceable filler 7.

[0116] In some embodiments, the pile 8 has negative skin friction. This negative skin friction is applied in advance. This embodiment provides a method for pre-applying negative skin friction to a pile, the steps of which include:

[0117] Step 1: Install the flexible composite panel horizontally;

[0118] Step 2: Set the initial control compression deformation value of the elastic composite plate;

[0119] Step 3: Load heavy objects onto the embedded plate 4 to pre-compress the elastic composite plate to the target compression depth;

[0120] Step 4: Complete the construction of all piles 8;

[0121] Step 5: Remove the load from the mounting plate 4.

[0122] See Figure 5 This is a schematic diagram illustrating the application of a composite pile foundation structure for optimizing pavement stiffness in highway transition sections, as provided in this application, to bridge abutment pile foundation conditions. This application provides a design and application method for bridge abutment pile foundations to design a composite pile foundation structure applicable to bridge abutment pile foundation conditions. This design and application method includes the following steps:

[0123] S51. Based on the roadbed design and construction plan, determine the highway grade and the standard value q of the uniformly distributed vehicle load, and determine the filling height H of the fill soil during construction on one side of the roadbed. t The height H after preloading construction y The roadbed width is B; the distance of half the bridge span is L; the weight of the elastic composite plate is Q1, and the elastic deformation coefficient is K1.

[0124] S52. Initially determine the width 'a' of one side of the bridge abutment pile foundation, the length of the pile cap along the traffic direction as 'b', the pile cap and the non-vehicle load Q2 borne by the pile cap, and clarify the standard value of the ultimate bearing capacity f of the replaceable fill material. oa Verify whether the foundation bearing capacity meets the requirement of 0.5.

[0125]

[0126] S53. Using the vehicle load on the road surface as the independent variable, establish a post-construction settlement calculation function for the road surface on one side of the roadbed:

[0127] S L (q)=S C (q)+S S (q)+S E -s GC1

[0128] Among them, S C (q) represents the subgrade deformation value as a function of the road vehicle load, S S (q) represents the foundation settlement value as a function of the road vehicle load, S E s represents the self-compaction settlement value caused by the embankment fill load. GC1This refers to the construction settlement on one side of the roadbed.

[0129] S C (q) is calculated using the following formula:

[0130] k is the total number of soil layers in the embankment fill, α zi The average vertical additional stress coefficient of the i-th soil layer, E sti The compression modulus of the i-th layer of embankment fill, H i Let be the thickness of the i-th layer of fill in the embankment.

[0131] S S (q) is calculated using the following formula:

[0132]

[0133] Where, α z Z represents the average additional stress coefficient of the vehicle load on the bottom of the roadbed. i Let be the distance from the roadbed surface to the i-th soil layer. σ is the average additional stress coefficient within the range from the subgrade surface to the i-th soil layer, taken according to Article J.0.2 of the "Code for Design of Highway Bridge and Culvert Foundations". z2 This represents the average additional stress exerted by the roadbed fill on the bottom of the roadbed.

[0134] S E The calculation formula is as follows:

[0135] γ i The unit weight of the i-th layer of embankment fill;

[0136] s GC1 The calculation formula is as follows:

[0137] s GC1 =H t -H y

[0138] S54. Using the vehicle load on the road surface as the independent variable, establish a post-construction settlement calculation function for the road surface on one side of the bridge abutment pile foundation:

[0139] S q (q)=ψ q [S t (q)+S sp ]+S K (q)-s GC2

[0140] In the formula, ψ q The correction factor for bridge abutment pavement settlement is calculated, and a value of 1 is taken in the absence of empirical values. t(q) is a function of the settlement of the elastic composite plate base plate 6 under additional pressure with respect to the road vehicle load, S sp S represents the settlement caused by the interaction between the pile and the soil. K (q) represents the total compression of the elastic composite plate, s GC2 This is due to construction settlement on one side of the bridge abutment.

[0141] S t (q) is calculated using the following formula:

[0142]

[0143] In the formula, η p σ represents the pile penetration deformation influence coefficient; when the pile tip bearing layer is sandy soil, silty soil, or cohesive soil, the values ​​are 1, 1.15, and 3, respectively; x represents the initial control compression deformation value of the elastic composite plate; n represents the number of piles arranged in the abutment pile foundation; m represents the number of soil layers included within the calculation depth, and the settlement calculation depth is based on σ. z =0.1σ c Determined, σ z For additional stress, σ c E represents vertical soil stress. si p0 is the compression modulus of the i-th soil layer; p0 is the additional stress of the elastic composite plate bottom plate 6. q sik Z represents the ultimate side skin friction, d is the pile diameter, k is the number of soil layers within the pile length range; σ3 is the additional vertical stress exerted by the backfill on the pile tip plane; Z i is the distance from the subgrade surface to the i-th soil layer; The average additional stress coefficient is taken from the subgrade surface to the i-th soil layer, according to Article J.0.2 of the "Code for Design of Highway Bridge and Culvert Foundations".

[0144] S sp The calculation formula is as follows:

[0145]

[0146] In the formula, l i Let l be the thickness of the i-th soil layer and l be the pile length.

[0147] S K (q) is calculated as follows:

[0148]

[0149] s GC2 The calculation formula is as follows:

[0150]

[0151] In the formula, ψSC P is the settlement correction factor for pile foundation construction. G =Q1+Q2, B e Based on the equivalent width,

[0152] ν s Let E0 be the weighted Poisson's ratio of the soil within the length of the piles under the bottom plate of the elastic composite slab, E0 be the average elastic modulus within the pile length, and C be the settlement influence coefficient of the pile group, which can be calculated according to the "Pile Foundation Engineering Handbook". e A is the effective load-bearing area calculated by subtracting the pile area from the foundation area. e =A-nπ(K) P d) 2 / 4,K P The value is typically 1.5.

[0153] S55. The seven unknown basic design parameters are: pile length l, pile diameter d, number of piles n, initial control compression deformation value x of the elastic composite plate, thickness h of the replaceable filler 7, and ultimate side friction resistance q of the replaceable filler 7. s1k The compressive modulus E of replaceable filler 7 s1 The standard value of the uniformly distributed load q of the vehicle is divided into 7 levels with equal increments starting from 0: q1, q2, q3, q4, q5, and q6. A set of control equations for the overall deformation of the road surface is then established.

[0154]

[0155] 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 pavement on one side of the roadbed under uniformly distributed vehicle loads 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 bridge abutment under the standard values ​​of 0, q1, q2, q3, q4, q5, and q6 of the uniformly distributed vehicle load.

[0156] S56. Solve the overall deformation control equations of the road surface to obtain the basic design combination parameters.

[0157] S57. Verification of basic design combination parameters, the process is as follows:

[0158] S571. Overall bearing capacity safety verification: The overall bearing capacity safety factor K should be no less than 2.

[0159]

[0160] S572, Pile Spacing Verification: The basic design combination parameters are required to ensure that the pile spacing is greater than 6.5 times the pile diameter under the bottom dimensions of the elastic composite plate;

[0161] S573. Verification of the principle of symmetrical layout: The layout of bridge abutment pile foundations should be symmetrical along both the roadbed cross section and the roadbed longitudinal direction;

[0162] S574. Post-construction settlement verification: Allowable post-construction settlement shall meet the requirements of Table 7.7.1-2 of the Highway Subgrade Design Specification (JTG D30-2015).

[0163] S58: Obtain the final design combination parameters for zero-difference settlement.

[0164] See Figure 6 This is a schematic diagram illustrating the application of a composite pile foundation structure for optimizing pavement stiffness in highway transition sections in embankment conditions, as provided in this application embodiment. This application embodiment also provides a design and application method for highway foundations to design composite pile foundation structures applicable to embankment conditions, comprising the following steps:

[0165] S61. Based on the roadbed design and construction plan, determine the highway grade and the standard value q of the uniformly distributed vehicle load, 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 The backfill height H after preloading construction 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.

[0166] S62. The weight of the foundation cap is Q3, the total fill volume of the transition section is Q4, and the bearing capacity of the foundation for replaceable fill material is f. oa Verify that the foundation bearing capacity meets the requirement of 0.5.

[0167]

[0168] S63. Using the vehicle load on the road surface as the independent variable, establish a post-construction settlement calculation function for the road surface on one side of the roadbed:

[0169] S L (q)=S C (q)+S S (q)+S E -s GC3

[0170] Among them, S C (q) represents the subgrade deformation value as a function of the road vehicle load, S S (q) represents the composite foundation settlement as a function of the road vehicle load, S E s represents the self-compaction settlement value caused by the embankment fill load. GC3 For construction settlement;

[0171] S C (q) is calculated using the following formula:

[0172] k is the total number of soil layers in the embankment fill, α zi E is the average vertical additional stress coefficient of the i-th soil layer. sti The compression modulus of the i-th layer of embankment fill, H i Let be the thickness of the i-th layer of fill in the embankment;

[0173] S S (q) is calculated using the following formula:

[0174] S S (q)=ψ l [S t (q)+S sp ]+S K (q); ψ l Correction factors for subgrade and pavement settlement calculation; S t (q) is a function of the settlement of the elastic composite plate base plate with respect to the road vehicle load. p0 is the additional stress of the elastic composite plate base plate 6; η p The pile penetration deformation influence coefficient is denoted by σ, with values ​​of 1, 1.15, and 3 for the pile tip bearing layers of sand, silt, and cohesive soil, respectively. x represents the initial control compression deformation value of the elastic composite plate, n is the number of piles in the composite foundation, and m is the number of soil layers included within the calculation depth. The settlement calculation depth is based on σ. z =0.1σ c Determined, σ z For additional stress, σ c For vertical soil stress, E si Let be the compression modulus of the i-th soil layer. q sik Z represents the ultimate side skin friction, d is the pile diameter, k is the number of soil layers within the pile length range, and Z is the ultimate side skin friction. i Let be the distance from the bottom plate 6 of the elastic composite panel to the i-th layer of soil. S represents the average additional stress coefficient within the range of the 6th to the i-th soil layer of the elastic composite slab base plate, taken according to Article J.0.2 of the "Code for Design of Highway Bridge and Culvert Foundations"; sp Settlement caused by the interaction between the pile and the soil. l i Let l be the thickness of the i-th soil layer and l be the pile length. S K (q) represents the total compression of the elastic composite plate.

[0175]

[0176] S E The calculation formula is as follows:

[0177] γ i The unit weight of the i-th layer of embankment fill;

[0178] s GC3 The calculation formula is as follows:

[0179] ψ SC This is the settlement correction factor for pile foundation construction.

[0180] P G =Q1 + Q3 + Q4, B e Based on the equivalent width, ν s Let E0 be the weighted Poisson's ratio of the soil within the length of the piles under the bottom plate of the elastic composite slab, E0 be the average elastic modulus within the pile length, and C be the settlement influence coefficient of the pile group, which can be calculated according to the "Pile Foundation Engineering Handbook". e The effective load-bearing area is the area of ​​the pile cap minus the area of ​​the piles.

[0181] A e =A-nπ(K) P d) 2 / 4,K P The value is typically 1.5;

[0182] S64. Based on the geological exploration, determine the reasonable design range of pile length; based on the pile type, determine the reasonable design range of pile diameter; clarify the post-construction settlement requirements for the transition section pavement as [s]; clarify the seven unknown basic design parameters as follows: pile length l, pile diameter d, number of piles n, initial control compression deformation value x of elastic composite plate, thickness h of replaceable filler, and ultimate side friction resistance q of replaceable filler. s1k The compressive modulus E of replaceable filler 7 s1 Establish a set of inequalities for post-construction settlement control of roadbed and pavement:

[0183]

[0184] In the formula, l min Indicates the minimum designable pile length, l max d represents the minimum designable pile length. min d represents the minimum designable pile diameter.max Indicates the minimum designable pile diameter, ... indicates other design requirements;

[0185] S65. Solve the system of settlement control inequalities to obtain the basic design combination parameters;

[0186]

[0187] In the formula, each row of parameters represents the calculated parameters of each set of basic design combinations;

[0188] S66. Verification of basic design combination parameters, the process is as follows:

[0189] S661. Overall bearing capacity safety verification: The overall bearing capacity safety factor K should be no less than 2.

[0190]

[0191] S662. Pile Spacing Verification: The basic design combination parameters are required to ensure that the pile spacing is greater than 6.5 times the pile diameter under the bottom dimensions of the elastic composite plate.

[0192] S663. Verification of the principle of symmetrical layout: The pile foundations of composite foundations should be symmetrically arranged along the center line of the road surface.

[0193] S67. Establish the cost function;

[0194] M=Cnπr 2 l+Dnπr 2 +EABh+FAB+GABH c +M q

[0195] In the formula, the unit of C is yuan / m 3 , represents the cost of material per cubic meter of pile; D is in yuan / m 2 , represents the cost of the adaptive deformer at the pile tip per square meter; E is in yuan / m 3 , indicates the cost of replacing 7 packing materials per cubic meter; F is in yuan / m 2 G represents the cost per square meter of elastic composite panel; the unit of G is yuan / m². 3 H represents the cost of 1 cubic meter of material for the foundation. c M represents the average thickness of foundation 1; q This indicates other costs.

[0196] S68. Calculate the minimum construction cost based on the basic design combination parameters;

[0197]

[0198] Among them, M minM1, M2, and M3 represent the construction costs under the following basic design parameters: Group 1, Group 2, Group 3, and Group k.

[0199] S69. Obtain the optimal design combination parameters.

[0200] The various embodiments or implementation methods described in this specification are presented in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referred to each other.

[0201] It should be noted that the terms "one embodiment," "embodiment," "exemplary embodiment," "some embodiments," etc., mentioned in the specification indicate that the described embodiment may include a specific feature, structure, or characteristic, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Moreover, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments, whether explicitly described or not, is within the knowledge scope of those skilled in the art.

[0202] Generally speaking, terms should be understood at least in part by their use in context. For example, at least in part by context, the term "one or more" as used in the text can be used to describe any feature, structure, or characteristic of the singular meaning, or a combination of features, structures, or characteristics of the plural meaning. Similarly, at least in part by context, terms such as "a" or "the" can also be understood to convey either singular or plural usage.

[0203] It should be readily understood that the terms “on,” “above,” and “on top of” in this disclosure should be interpreted in the broadest possible sense, such that “on” means not only “directly on something” but also “on something” with an intermediate feature or layer therebetween, and that “above” or “on top of” means not only “on top of something” but also “on top of something” without an intermediate feature or layer therebetween (i.e., directly on something).

[0204] Furthermore, for ease of explanation, spatially relative terms such as "below," "below," "under," "above," and "above" may be used 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 other than those shown in the figures. The device may have other orientations (rotated 90 degrees or in other orientations), and the spatially relative descriptive terms used herein may be interpreted accordingly.

[0205] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A composite pile foundation structure for optimizing pavement stiffness in highway transition sections, characterized in that: This includes pile caps, pile caps, elastic composite plates, replaceable fillers, piles, and pile end adaptive deformers. The pile cap is embedded in the elastic composite plate. The elastic composite plate undergoes compression deformation during construction to pre-apply negative skin friction to the pile. The elastic composite plate is located on a replaceable material. The replaceable filler is selected based on parameters calculated according to the deformation control equation. The control variables of the replaceable filler include depth, compression modulus, and ultimate side skin friction. Multiple piles are configured, and the spacing between each pile is at least 6.5 times the pile diameter. The piles exert their ultimate bearing capacity under normal working conditions. The pile cap and the pile end adaptive deformer are connected to the top and end of the pile, respectively.

2. The composite pile foundation structure for optimizing pavement stiffness in highway transition sections as described in claim 1, characterized in that: The elastic deformation coefficient of the elastic composite plate ranges from 0.3 GPa to 0.9 GPa. The elastic composite plate is in the elastic stage when in use. The elastic composite plate includes a fixed plate, an elastic plate, and a base plate. The upper surface of the fixed plate is provided with horizontal grooves and vertical grooves. The fixed plate is fixedly connected to the support platform. The elastic plate is located between the fixed plate and the base plate. The elastic plate is rigidly connected to the fixed plate and the base plate.

3. The composite pile foundation structure for optimizing pavement stiffness in highway transition sections as described in claim 1, characterized in that: The pile has negative skin friction.

4. The composite pile foundation structure for optimizing pavement stiffness in highway transition sections as described in claim 1, characterized in that: The pile cap is provided at the top of the pile, the pile end adaptive deformer is provided at the end of the pile, a gasket is provided below the pile cap, and the pile passes through the elastic composite plate and the replaceable material and extends into the pile cap and the replaceable filler.

5. The composite pile foundation structure for optimizing pavement stiffness in highway transition sections as described in claim 1, characterized in that: The replaceable filler is used to share the incremental load from the upper part after the pile has reached its ultimate bearing capacity, preventing rapid settlement and deformation.

6. The composite pile foundation structure for optimizing pavement stiffness in highway transition sections as described in 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 pavement stiffness in highway transition sections as described in 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 pile cap is first transmitted to the replaceable fill material, then to the pile, and finally to the replaceable fill material. The force transmission stage includes: Phase 1: The increase in load on the upper part of the pile cap is completely offset by the negative skin friction, and the upper load is completely shared by the replaceable fill material, so the bearing capacity of the pile is not utilized. Second stage: The load increment on the upper part of the pile cap is completely shared by the piles, the piles begin to exert their bearing capacity, and the replaceable fill material always shares the load of the total negative skin resistance pre-added during the construction stage. Phase 3: The load increment on the upper part of the pile cap is entirely shared by the replaceable filler, the pile is in an elastic support state, the bearing capacity of the pile is fully utilized, and the replaceable filler shares the set load.

8. A design and application method for bridge abutment pile foundations, characterized in that, For designing a composite pile foundation structure for optimizing pavement stiffness in highway transition sections as described in any one of claims 1-7, comprising: Step 1: Based on the roadbed design and construction plan, determine the highway grade and the standard value of the uniformly distributed vehicle load as q, and the filling height of the fill soil on one side of the roadbed during construction as H. t The height after preloading is H y The roadbed width is B, the distance of half the bridge span is L, the weight of the elastic composite plate is Q1, and the elastic deformation coefficient is K1. Step 2: Initially determine the width 'a' of one side of the bridge abutment pile foundation, the length 'b' of the pile cap along the traffic direction, the pile cap and the non-vehicle load Q2 borne by the pile cap, and the standard value of the ultimate bearing capacity 'f' of the replaceable fill material. oa The following formula can be used to verify whether the foundation bearing capacity satisfaction rate is greater than 0.5: Wherein, ψ represents the foundation bearing capacity satisfaction rate; Step 3: Using the vehicle load on the road surface as the independent variable, establish a post-construction settlement calculation function for 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 post-construction settlement calculation function for the pavement on one side of the roadbed, S C (q) represents the subgrade deformation value as a function of the road vehicle load, S S (q) represents the foundation settlement value as a function of the road vehicle load, S E s represents the self-compaction settlement value caused by the embankment fill load. GC1 Construction settlement on one side of the roadbed; S C (q) is calculated using the following formula: Where k is the total number of soil layers in the embankment fill, α zi E is the average vertical additional stress coefficient of the i-th layer of fill. sti Let H be the compression modulus of the i-th layer of embankment fill. i Let be the thickness of the i-th layer of fill in the embankment; S S (q) is calculated using the following formula: Where, α z z is the average additional stress coefficient of the vehicle load on the bottom of the roadbed. i-1 and Z i Let be the distance from the roadbed surface to the (i-1)th and i-th soil layers. and These are the average additional stress coefficients σi and σi, respectively, within the range from the subgrade surface to the (i-1)th and ith layers of soil. z2 This represents the average additional stress exerted by the roadbed fill on the bottom of the roadbed. S E The calculation formula is as follows: Where, γ i-1 and γ i H represents the unit weight of the (i-1)th and i-th layers of fill in the embankment; i-1 The thickness of the (i-1)th layer of fill in the embankment; s GC1 The calculation formula is as follows: s GC1 =H t -H y Step 4: Using the vehicle load on the road surface as the independent variable, establish a post-construction settlement calculation function for the road surface on one side of the bridge abutment pile foundation: S q (q)=ψ q [S t (q)+S sp ]+S K (q)-s GC2 Where, ψ q The correction factor for bridge abutment pavement settlement is calculated, and a value of 1 is taken in the absence of empirical values. t (q) is a function of the settlement of the elastic composite plate under the additional pressure on the bottom of the plate with respect to the road vehicle load, S sp S represents the settlement caused by the interaction between the pile and the soil. K (q) represents the total compression of the elastic composite plate, s GC2 Construction settlement on one side of the bridge abutment; S t (q) is calculated using the following formula: Where, η p σ represents the pile penetration deformation influence coefficient, with values ​​of 1, 1.15, and 3 for the pile tip bearing layers of sandy soil, silty soil, and cohesive soil, respectively; x represents the initial control compression deformation value of the elastic composite plate; n represents the number of piles arranged in the abutment pile foundation; m represents the number of soil layers included within the calculation depth, and the settlement calculation depth is based on σ. z =0.1σ c Determined, σ z For additional stress, σ c E represents vertical soil stress. si pi is the compression modulus of the i-th soil layer; p0 is the additional stress on the bottom plate of the elastic composite plate. q sik σ3 represents the ultimate side friction resistance, d is the pile diameter, k is the number of soil layers within the pile length range, and σ3 is the additional vertical stress exerted by the backfill on the pile end plane. S sp The calculation formula is as follows: In the formula, This represents the thickness-weighted average side friction resistance within the pile body. l represents the average compression modulus within the pile body. i Let l be the thickness of the i-th soil layer and l be the pile length. S K (q) is calculated as follows: s GC2 The calculation formula is as follows: Where, ψ SC P is the settlement correction factor for pile foundation construction. G =Q1+Q2, B e Based on the equivalent width, ν s E0 is the weighted Poisson's ratio of the soil within the pile length range under the elastic composite slab base plate, C is the average elastic modulus within the pile length range, and A is the settlement influence coefficient of the pile group. e The effective load-bearing area is the area of ​​the pile cap minus the area of ​​the piles. Step 5: Determine the 7 unknown basic design parameters as follows: pile length l, pile diameter d, number of piles n, initial control compression deformation value x of the elastic composite plate, thickness h of the replaceable filler, and ultimate side friction resistance q of the replaceable filler. s1k The compressive modulus E of replaceable fillers s1 The standard value of the uniformly distributed vehicle load q is divided into 7 levels with equal increments starting from 0: q1, q2, q3, q4, q5, and q6. A set of overall road deformation control equations is 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 pavement on one side of the roadbed under uniformly distributed vehicle loads 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 bridge abutment under the standard values ​​of 0, q1, q2, q3, q4, q5, and q6 of the uniformly distributed vehicle load; Step 6: Solve the set of equations governing the overall deformation of the road surface to obtain the basic design combination parameters; Step 7: Verify the basic design combination parameters, including: The overall load-bearing capacity safety factor K should be not less than 2 for the overall load-bearing capacity safety factor verification. Pile spacing verification: The basic design combination parameters are required to ensure that the pile spacing is greater than 6.5 times the pile diameter under the bottom dimensions of the elastic composite plate; Verification of the symmetrical layout principle: The layout of bridge abutment pile foundations should be symmetrical along both the roadbed cross section and the roadbed longitudinal direction; Step 8: Obtain the final zero-difference settlement design combination parameters.

9. A design and application method for highway subgrade, characterized in that, For designing a composite pile foundation structure for optimizing pavement stiffness in highway transition sections as described in any one of claims 1-7, comprising: Step 1: Based on the roadbed design and construction plan, determine the highway grade and the standard value q of the uniformly distributed vehicle load, the length L1 of the transition section, and clarify the initial height H of the fill during construction on one side of the roadbed. t The backfill height H after preloading construction y , roadbed and pavement width B, elastic composite plate length A, elastic composite plate width B, elastic composite plate weight Q1, elastic deformation coefficient K1; Step 2: Determine the foundation weight Q3, the total fill volume of the transition section roadbed Q4, and the foundation bearing capacity f of the replaceable materials. oa Verify that the foundation bearing capacity meets the requirement of 0.

5. In the formula, ψ1 is the foundation bearing capacity satisfaction rate; Step 3: Using the vehicle load on the road surface as the independent variable, establish a post-construction settlement calculation function for 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 subgrade deformation value as a function of the road vehicle load, S S (q) represents the composite foundation settlement as a function of the road vehicle load, S E s represents the self-compaction settlement value caused by the embankment fill load. GC3 For construction settlement; S C (q) is calculated using the following formula: Where k is the total number of soil layers in the embankment fill, α zi E is the average vertical additional stress coefficient of the i-th soil layer. sti The compression modulus of the i-th layer of embankment fill, H i Let be the thickness of the i-th layer of fill in the embankment; S S (q) is calculated using the following formula: S S (q)=ψ l [S t (q)+S sp ]+S K (q) Where, ψ l Correction factors for subgrade and pavement settlement calculation; S t (q) is a function of the settlement of the bottom of the elastic composite plate with respect to the road vehicle load. p0 is the additional stress on the bottom plate of the elastic composite plate; η p The pile penetration deformation influence coefficient is denoted by σ, with values ​​of 1, 1.15, and 3 for the pile tip bearing layers of sand, silt, and cohesive soil, respectively. x represents the initial control compression deformation value of the elastic composite plate, n is the number of piles in the composite foundation, and m is the number of soil layers included within the calculation depth. The settlement calculation depth is based on σ. z =0.1σ c Determined, σ z For additional stress, σ c For vertical soil stress, E si Let be the compression modulus of the i-th soil layer. q sik Z represents the ultimate side skin friction, d is the pile diameter, k is the number of soil layers within the pile length range, and Z is the ultimate side skin friction. i Let be the distance from the bottom of the elastic composite panel to the i-th layer of soil. S is the average additional stress coefficient within the range from the bottom of the elastic composite plate to the i-th soil layer; sp Settlement caused by the interaction between the pile and the soil. l i Let l be the thickness of the i-th soil layer and l be the pile length. S K (q) represents the total compression of the elastic composite plate. S E The calculation formula is as follows: Where, γ i-1 and γ i H represents the unit weight of the (i-1)th and i-th layers of fill in the embankment; i-1 The thickness of the (i-1)th layer of fill in the embankment; s GC3 The calculation formula is as follows: Where, ψ SC P is the settlement correction factor for pile foundation construction. G =Q1 + Q3 + Q4, B e Based on the equivalent width, ν s E0 is the weighted Poisson's ratio of the soil within the pile length range under the elastic composite slab base plate, C is the average elastic modulus within the pile length range, and A is the settlement influence coefficient of the pile group. e The effective load-bearing area is the area of ​​the pile cap minus the area of ​​the piles. Step 4: Determine the reasonable design range of pile length based on geological exploration, and determine the reasonable design range of pile diameter based on pile type; determine the post-construction settlement requirement of the transition section pavement as [s]; determine the 7 unknown basic design parameters as follows: pile length l, pile diameter d, number of piles n, initial control compression deformation value x of elastic composite plate, thickness h of replaceable filler, and ultimate side friction resistance q of replaceable filler. s1k The compressive modulus E of replaceable fillers s1 Establish a set of inequalities for overall deformation control of roadbed and pavement: In the formula, l min Indicates the minimum designable pile length, l max d represents the minimum designable pile length. min d represents the minimum designable pile diameter. max Indicates the minimum designable pile diameter, ... indicates other design requirements; Step 5: Solve the system of settlement control inequalities to obtain the basic design combination parameters; In the formula, each row of parameters represents the calculated parameters of each set of basic design combinations; Step Six: Verification of basic design combination parameters, including: Overall load-bearing capacity safety verification: The overall load-bearing capacity safety factor K is guaranteed to be no less than 2. Pile spacing verification: The basic design combination parameters are required to ensure that the pile spacing is greater than 6.5 times the pile diameter under the bottom dimensions of the elastic composite plate; Verification of the symmetrical layout principle: The pile foundations of composite foundations should be laid out symmetrically along the centerline of the road surface; Step 7: Establish the cost function; M=Cnπr 2 l+Dnπr 2 +EABh+FAB+GABH c +M q In the formula, C represents the cost of each cubic meter of pile material, in yuan / m. 3 D represents the cost per square meter of the adaptive deformer at the pile tip, in yuan / m. 2 E represents the cost of replaceable materials per cubic meter, in yuan / m³. 3 F represents the local cost per square meter of flexible composite panel, in yuan / m². 2 G represents the cost of material per cubic meter of foundation, in yuan / m. 3 H c M represents the average thickness of the foundation; q 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 These represent the construction costs under the first group of basic design parameters, the second group of basic design parameters, the third group of basic design parameters, and the kth group of basic design parameters, respectively. Step 9: Obtain the optimal design combination parameters.

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