Variable-stiffness energy pile group pile thermal-mechanical coupling response calculation method

Abstract

The invention relates to the technical field of thermal-mechanical coupling response calculation, and particularly discloses a variable-rigidity energy pile group pile thermal-mechanical coupling response calculation method which is realized through the following technical steps: firstly, selecting a load transfer model for simulating pile-soil nonlinear interaction, and determining an equal-rigidity energy pile group pile algorithm; secondly, the pile type (variable pile diameter and variable pile length) of the variable-stiffness energy pile group is judged, pile side-pile end soil elastic displacement interaction factors considering pile-pile interaction are calculated, and a pile-soil interaction model of the variable-stiffness energy pile group is determined; then, pile side-and pile end-soil interaction model parameters are determined; and finally, the pile side-pile end-soil interaction model of the variable-rigidity energy pile group is substituted into an equal-rigidity energy pile group algorithm, and the thermal coupling response of the variable-rigidity energy pile group is calculated. The method is simple in principle, simple, convenient and easy to use, and can provide a method and a theoretical basis for improvement and enrichment of an energy pile thermal-mechanical coupling calculation method.

Description

Technical Field

[0001] The invention relates to the technical field of thermal coupling response calculation, and in particular to a method for calculating the thermal coupling response of a variable stiffness energy pile group. Background Art

[0002] Pile foundation can control overall and differential settlement and is an economical and effective deep foundation form. At present, the conventional design of pile foundation mostly adopts equal stiffness design, that is, the single pile foundation in the pile group has the same pile length, pile diameter and material properties. Although this design is convenient and easy to implement, it fails to accurately reflect the actual stress conditions of the pile group, resulting in significant differential settlement, which seriously threatens the service safety of the foundation and superstructure.

[0003] In response to the problems existing in the design of equal-rigidity pile groups, the Technical Specifications for Building Pile Foundations proposed a variable-rigidity leveling design concept. By using pile foundations with different stiffnesses, the overall stiffness of the pile group is increased to offset the uneven stiffness distribution caused by the pile group effect, thereby effectively controlling the differential settlement of the pile group. For example, in deep soft soil or compressible soil layers, the contribution of the raft to the long-term stiffness of the foundation gradually decreases, and the stiffness of the piles needs to be increased to improve the stress characteristics of the foundation and the superstructure. In addition, for flexible rafts and rafts subjected to uneven loads, increasing the diameter or length of the piles in the pile group to increase the stiffness is a necessary measure to control the differential settlement of the pile group.

[0004] In recent years, energy piles, as a derivative form of traditional building pile foundations, organically combine heat exchange tubes and pile foundations, and have both load-bearing and heat exchange functions. They have become an important green geotechnical engineering technology under the background of dual carbon. Since the prerequisite for the application of energy piles is that the load-bearing engineering of the pile foundation is not affected, the arrangement of pile groups is inevitably similar to that of traditional building pile foundations. In particular, for working conditions that require strict control of differential settlement, the arrangement of variable stiffness energy pile groups has a wider range of applications. In the thermal-mechanical coupling design process of energy piles, the load transfer method is simple in concept, easy to use, and can effectively simulate the nonlinear load transfer mechanism of pile-soil interaction, and has been widely used. However, existing studies have focused on the thermal-mechanical coupling characteristics of equal-stiffness energy pile groups, and the calculation method of the thermal-mechanical coupling response of variable stiffness energy pile groups is still lacking, which has become a blank in the field of energy pile technology.

[0005] In addition, compared with traditional variable stiffness pile groups, the response mechanism of variable stiffness energy pile groups is more complicated. Specifically, on the one hand, the response of variable stiffness energy pile groups needs to consider the influence of thermal load on the interaction between energy piles and soil in the pile group; on the other hand, it is necessary to consider the deformation and stress field response characteristics of energy piles and soil around piles under thermal coupling, as well as the complex coupling effects between piles-soil and piles-raft-soil. Therefore, the calculation method of traditional variable stiffness pile group response cannot evaluate the interaction and thermal coupling response of variable stiffness energy pile groups, and a new calculation method is urgently needed to fill this gap. Summary of the invention

[0006] In order to solve the problems existing in the prior art, the present invention provides a method for calculating the thermal-mechanical coupling response of a variable-rigidity energy pile group by analyzing the interactions between pile-soil, pile-raft-soil and pile-pile in a variable-rigidity energy pile group. The method can quickly evaluate the thermal-mechanical coupling performance and solve the problems mentioned in the above background technology.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for calculating the thermal-mechanical coupling response of a variable stiffness energy pile group, comprising the following steps:

[0008] S1. Select the load transfer model to simulate the pile-soil nonlinear interaction and determine the algorithm for equal stiffness energy pile groups;

[0009] S2. Determine the type of the variable stiffness energy pile group, calculate the pile side-soil elastic displacement interaction factor considering the pile-pile interaction, and determine the pile side-soil interaction model of the variable stiffness energy pile group;

[0010] S3, determine the type of the variable stiffness energy pile group, calculate the pile end-soil elastic displacement interaction factor considering the pile-pile interaction, and determine the pile end-soil interaction model of the variable stiffness energy pile group;

[0011] S4, determine the pile side- and pile tip-soil interaction model parameters;

[0012] S5. Substitute the pile side- and pile end-soil interaction models of the variable stiffness energy pile group into the equal stiffness energy pile group algorithm to calculate the thermal-mechanical coupling response of the variable stiffness energy pile group.

[0013] Preferably, in step S1, the pile-soil relative displacement consists of two parts: nonlinear displacement and elastic displacement; the nonlinear displacement is calculated by a load transfer model, and the elastic displacement is obtained by the relevant principles of the shear displacement method.

[0014] Preferably, the load transfer model is an exponential model, a hyperbolic model, a double-broken line model, a three-broken line model or an ideal elastic-plastic model.

[0015] Preferably, in step S2, the following steps are specifically included:

[0016] S21. If the variable stiffness energy pile group type is a variable pile diameter type energy pile group, the pile side-soil elastic displacement interaction factor only considers the replacement of the pile diameter, that is, the pile side-soil interaction model of the variable stiffness energy pile group is obtained;

[0017] S22. If the type of variable stiffness energy pile group is a variable pile length type energy pile group, the pile side-soil elastic displacement interaction factor of any long pile in the pile group should consider the following six factors: 1) axial displacement caused by the load on itself; 2) displacement increment caused by other long piles in the pile group that are within the influence range of the shear radius; 3) displacement reduction caused by the "reinforcement-curtain" effect of other long piles in the pile group that are within the influence range of the shear radius; 4) displacement increment caused by other short piles in the pile group that are within the influence range of the shear radius; 5) displacement reduction caused by the "reinforcement-curtain" effect of other short piles in the pile group that are within the influence range of the shear radius; 6) displacement increment caused by the pile ends of other short piles in the pile group that are within the influence range of the shear radius; that is, the pile side-soil interaction model of the variable stiffness energy pile group is obtained;

[0018] S23. If the type of variable stiffness energy pile group is a variable pile length type energy pile group, the pile side-soil elastic displacement interaction factor of any short pile in the pile group should consider the following five factors: 1) axial displacement caused by the load on itself; 2) displacement increment caused by other short piles in the pile group that are within the influence of the shear radius; 3) displacement reduction caused by the "reinforcement-curtain" effect of other short piles in the pile group that are within the influence of the shear radius; 4) displacement increment caused by other long piles in the pile group that are within the influence of the shear radius; 5) displacement reduction caused by the "reinforcement-curtain" effect of other long piles in the pile group that are within the influence of the shear radius; that is, the pile side-soil interaction model of the variable stiffness energy pile group is obtained.

[0019] Preferably, in step S3, the following steps are specifically included:

[0020] S31. If the variable stiffness energy pile group type is a variable pile diameter type energy pile group, the pile tip-soil elastic displacement interaction factor only considers the replacement of the pile diameter, that is, the pile tip-soil interaction model of the variable stiffness energy pile group is obtained;

[0021] S32. If the variable stiffness energy pile group type is a variable length type energy pile group, then the pile tip-soil elastic displacement interaction factor of any long pile in the pile group only considers the axial displacement caused by the load on itself, that is, the pile tip-soil interaction model of the variable stiffness energy pile group is obtained;

[0022] S33. If the type of variable stiffness energy pile group is a variable pile length type energy pile group, the pile end-soil elastic displacement interaction factor of any short pile in the pile group should consider the following two factors: 1) the pile end displacement caused by the load on itself; 2) the reduction of pile end displacement caused by the "reinforcement-curtain" effect of other long piles in the pile group that are within the influence range of the shear radius; that is, the pile end-soil interaction model of the variable stiffness energy pile group is obtained.

[0023] Preferably, in step S4, the model parameters include 1) pile-soil interface shear strength; 2) pile side-soil initial shear stiffness; 3) pile end ultimate strength; 4) pile end-soil interaction initial stiffness; 5) pile-raft contact stiffness.

[0024] Preferably, in step S5, the algorithm for equal stiffness energy pile group is similar to the general energy pile load transfer algorithm in structure, except that the elastic displacement interaction factor between equal stiffness energy piles is considered. The algorithm for equal stiffness energy pile group comprises the following specific steps:

[0025] S51, select the load transfer model and pile top contact stiffness to simulate the pile-soil nonlinear interaction;

[0026] S52. Calculate the pile side- and pile tip-soil elastic displacement interaction factors considering pile-pile interaction;

[0027] S53, determine the pile side- and pile tip-soil interaction model for equal stiffness energy pile groups;

[0028] S54, determining pile side- and pile tip-soil interaction model parameters;

[0029] S55. Substitute the pile side- and pile end-soil interaction models of the equal-stiffness energy pile group into the energy pile single-pile thermal coupling algorithm to obtain the equal-stiffness energy pile group thermal coupling response.

[0030] The beneficial effects of the present invention are as follows: the variable stiffness energy pile group thermal coupling response calculation method of the present invention can calculate the magnitude and distribution form of the coupling stress, strain and displacement of the variable stiffness energy pile group with different pile diameters and pile lengths; it can consider the "reinforcement-curtain" effect and pile group effect between the variable stiffness energy piles in the pile group. The method is simple in principle, easy to use, and can provide a method and theoretical basis for the improvement and enrichment of the energy pile thermal coupling calculation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a flow chart of a method for calculating thermal-mechanical coupling response of variable-stiffness energy pile groups in an embodiment of the present invention;

[0032] Figure 2 It is a flow chart of the algorithm for medium-rigidity energy pile groups in an embodiment of the present invention;

[0033] Figure 3 It is a schematic diagram of a variable stiffness energy pile group case in an embodiment of the present invention;

[0034] Figure 4 It is a schematic diagram of finite element simulation parameters in a verification case of a variable stiffness energy pile group in an embodiment of the present invention;

[0035] Figure 5 It is a parameter diagram of the calculation method of the present invention in a verification case of a variable stiffness energy pile group in an embodiment of the present invention;

[0036] Figure 6 1 is a comparison diagram of the calculation and simulation results of the variable stiffness energy pile group of the present invention, (a) is the comparison of the axial thermal stress of the long piles in the pile group; (b) is the comparison of the axial thermal stress of the short piles; (c) is the comparison of the axial thermal stress of the energy piles with larger diameters; (d) is the comparison of the axial thermal stress of the energy piles with smaller diameters. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] In the calculation method of the thermal coupling response of the variable stiffness energy pile group of the present invention, the following basic assumptions are made: 1) The load transfer model parameters, the thermal physical and mechanical properties of the pile body material and the surrounding soil do not change with temperature. Existing studies have shown that within the temperature variation range of 15 to 20° C. during the operation of the energy pile, the properties of the pile body concrete and the soil body hardly change; 2) Existing studies have shown that the radial deformation of the pile and the pile side normal stress under the action of thermal coupling have little effect on the change of the mechanical properties of the pile body. Therefore, the influence of the axial deformation of the pile is mainly considered in the study; 3) The stress and strain of the pile body are positive under compression, the friction resistance is positive upward, and the displacement of the pile body is positive upward; 4) The cross-sectional geometry, physical and mechanical properties and temperature changes of the pile body are evenly distributed along the pile body.

[0039] See also Figure 1 The present invention provides a technical solution: a method for calculating the thermal-mechanical coupling response of variable stiffness energy pile groups. Based on the above basic assumptions, the specific implementation steps are as follows:

[0040] (1) Select a load transfer model that simulates the nonlinear interaction between piles and soil and determine the algorithm for equal stiffness energy pile groups;

[0041] (2) Determine the type of variable stiffness energy pile group (variable pile diameter, variable pile length), calculate the pile side-soil elastic displacement interaction factor considering the pile-pile interaction, and determine the pile side-soil interaction model of the variable stiffness energy pile group;

[0042] (3) Determine the type of variable stiffness energy pile group (variable pile diameter, variable pile length), calculate the pile end-soil elastic displacement interaction factor considering the pile-pile interaction, and determine the pile end-soil interaction model of the variable stiffness energy pile group;

[0043] (4) Determine the pile side- and pile tip-soil interaction model parameters;

[0044] (5) The pile side- and pile end-soil interaction models of variable stiffness energy pile groups are substituted into the equal stiffness energy pile group algorithm to calculate the thermal-mechanical coupling response of the variable stiffness energy pile group.

[0045] In the step (1), the pile-soil relative displacement consists of two parts: nonlinear displacement and elastic displacement. The specific calculation method is as follows: the nonlinear displacement can be calculated by a load transfer model, including but not limited to an exponential model, a hyperbolic model, a bilinear model, a trilinear model, an ideal elastic-plastic model, etc.; the elastic displacement can be obtained by the relevant principles of the shear displacement method; the equal-rigidity energy pile group algorithm is similar in structure to the general energy pile load transfer algorithm, except that the elastic displacement interaction factor between equal-rigidity energy piles is considered. The steps of the equal-rigidity energy pile group algorithm are as follows: Figure 2 As shown, specifically:

[0046] 1) Select the load transfer model and pile top contact stiffness to simulate the pile-soil nonlinear interaction.

[0047] 2) Calculate the pile side- and pile tip-soil elastic displacement interaction factors considering pile-pile interaction, as shown in equations (1) and (2) respectively:

[0048]

[0049] Where: G is the shear modulus of the soil on the pile side; r 0 is the pile diameter; r m is the shear influence radius; r ij G is the axial distance between the pile and the adjacent pile in the pile group; b is the shear modulus of soil at the pile end; ν b is the Poisson's ratio of the soil at the pile end.

[0050] 3) Determine the pile side- and pile end-soil interaction models of the equal stiffness energy pile group. Preferably, taking the exponential model as an example, the pile side- and pile end-soil interaction models are respectively expressed as equations (3) and (4).

[0051]

[0052]

[0053] Where: u s is the sum of the nonlinear displacement and elastic displacement of the soil at the pile side; u s0 and τ s0 are the total displacement and shear stress of the pile side at the unloading point or reloading point respectively; η is the loading and unloading state judgment factor; τ su G is the shear strength of the soil at the pile side; s,max is the initial shear stiffness of pile side-soil; τ si is the pile side shear stress; u p is the sum of the nonlinear displacement and elastic displacement of the pile end; u p0 and τ b0 are the total displacement and shear stress at the pile end at the unloading point or reloading point respectively; G b,max Initial stiffness of pile-soil interaction; κ is the loading and unloading state judgment factor; τ bu is the limit end resistance; τ bi Pile end resistance.

[0054] 4) Determine the pile side and pile tip soil interaction model parameters. The main parameters include the pile-soil interface shear strength, pile side-soil initial shear stiffness, pile tip ultimate strength, pile tip-soil interaction initial stiffness, and pile-raft contact stiffness, which can be determined through field test results, unit test results, and corresponding empirical formulas.

[0055] 5) The pile side- and pile end-soil interaction models of equal-stiffness energy pile groups are substituted into the thermal-mechanical coupling algorithm of energy piles to obtain the thermal-mechanical coupling response of equal-stiffness energy pile groups.

[0056] The specific implementation method of step (2) is as follows: if it is a pile group of energy piles of variable pile diameter type, then its elastic displacement interaction factor is similar to the expression of the pile group of energy piles with equal stiffness, and only the corresponding pile diameter needs to be replaced; if it is a pile group of energy piles of variable pile length type, then the pile side-soil elastic displacement interaction factor of any long pile in the pile group needs to consider six factors: 1) axial displacement caused by the load on itself; 2) displacement increment caused by other long piles in the pile group that are within the influence range of the shear radius; 3) displacement reduction caused by the "reinforcement-curtain" effect of other long piles in the pile group that are within the influence range of the shear radius; 4) displacement increment caused by other short piles in the pile group that are within the influence range of the shear radius; 5) displacement reduction caused by the "reinforcement-curtain" effect of other short piles in the pile group that are within the influence range of the shear radius; 6) displacement increment caused by the pile ends of other short piles in the pile group that are within the influence range of the shear radius.

[0057] like Figure 3As shown in the figure, taking the 1×4 variable stiffness energy pile group as an example, the axial displacement caused by any long pile in the pile group under its own load is:

[0058]

[0059] 2) The displacement increment caused by other long piles in the pile group that are within the influence range of the shear radius;

[0060]

[0061] The displacement reduction of other long piles in the pile group that are within the influence range of the shear radius due to the "reinforcement-curtain" effect is:

[0062]

[0063] The displacement increment caused by other short piles in the pile group within the influence range of the shear radius is:

[0064]

[0065] The displacement reduction of other short piles in the pile group within the influence range of the shear radius due to the "reinforcement-curtain" effect is:

[0066]

[0067] The displacement increment caused by the pile ends of other short piles in the pile group within the influence range of the shear radius is:

[0068]

[0069] Then the pile side-soil elastic displacement interaction factor of any long pile in the pile group is:

[0070]

[0071] The pile side-soil elastic displacement interaction factor of any short pile in a pile group needs to consider five factors: 1) the axial displacement caused by the load on itself; 2) the displacement increment caused by other short piles in the pile group that are within the influence of the shear radius; 3) the displacement reduction caused by the "reinforcement-curtain" effect of other short piles in the pile group that are within the influence of the shear radius; 4) the displacement increment caused by other long piles in the pile group that are within the influence of the shear radius; 5) the displacement reduction caused by the "reinforcement-curtain" effect of other long piles in the pile group that are within the influence of the shear radius.

[0072] like Figure 3 As shown in the figure, taking the 1×4 variable stiffness energy pile group as an example, the axial displacement caused by any short pile in the pile group under its own load is:

[0073]

[0074] The displacement increment caused by other short piles in the pile group that are within the influence range of the shear radius is:

[0075]

[0076] The displacement reduction of other short piles in the pile group within the influence range of the shear radius due to the "reinforcement-curtain" effect is:

[0077]

[0078] The displacement increment caused by other long piles in the pile group within the influence range of the shear radius is:

[0079]

[0080] The displacement reduction of other long piles in the pile group that are within the influence range of the shear radius due to the "reinforcement-curtain" effect is:

[0081]

[0082] Then the pile side-soil elastic displacement interaction factor of any short pile in the pile group is:

[0083]

[0084] Combined with the exponential model, the pile side-soil interaction model of variable stiffness energy pile group is:

[0085]

[0086] According to the type of variable stiffness pile group, it is necessary to replace ψ with ψ siL Or siS .

[0087] The specific implementation method of step (3) is as follows: if it is a variable pile diameter type energy pile group, then its elastic displacement interaction factor is similar to the expression of equal stiffness energy pile group, and only the corresponding pile diameter needs to be replaced; if it is a variable pile length type energy pile group, then the pile end-soil elastic displacement interaction factor of any long pile in the pile group needs to consider the axial displacement caused by the load on itself;

[0088] The pile tip-soil elastic displacement interaction factor of any short pile in a pile group needs to consider two factors: 1) the pile tip displacement caused by the load on the pile itself; 2) the reduction in pile tip displacement caused by the "reinforcement-curtain" effect of other long piles in the pile group that are within the influence range of the shear radius.

[0089] like Figure 3As shown in the figure, taking the 1×4 variable stiffness energy pile group as an example, the axial displacement caused by any short pile in the pile group under its own load is:

[0090]

[0091] The reduction in pile tip displacement of other long piles in the pile group that are within the influence range of the shear radius due to the “reinforcement-curtain” effect is:

[0092]

[0093] Then the pile tip-soil elastic displacement interaction factor of any short pile in the pile group is:

[0094]

[0095] The pile tip-soil interaction model of variable stiffness energy pile group is:

[0096]

[0097] According to the type of variable stiffness pile group, it is necessary to replace λ in the formula accordingly.

[0098] The parameter determination method in step (4) is similar to that of equal-rigidity energy pile groups. Taking the exponential model as an example, the main parameters include the shear strength of the pile-soil interface, the initial shear stiffness of the pile side-soil, the ultimate strength of the pile end, the initial stiffness of the pile end-soil interaction, and the pile-raft contact stiffness, which can be determined through field test results, unit test results and corresponding empirical formulas.

[0099] The present invention verifies the reliability and effectiveness of the proposed method in analyzing the thermal-mechanical coupling response of variable-stiffness energy pile groups through finite element simulation cases, and the cases include two working conditions. In working condition one, the pile group consists of two 20m-long energy piles and two 30m-long energy piles, with a pile diameter of 0.6m and a pile spacing of 1.8m; in working condition two, the pile group consists of two energy piles with a pile diameter of 0.6m and two energy piles with a pile diameter of 0.8m, with a pile length of 20m and a pile spacing of 1.8m. Under both working conditions, it is assumed that there is no mechanical load on the pile top, the pile-raft contact stiffness is zero, and the temperature load is 10 and 30°C. The calculation parameters of the finite element simulation and the method proposed in the present invention are respectively as follows: Figure 4 and 5 shown.

[0100] Said Figure 6 The calculation results of the method proposed in this invention are compared with the finite element simulation results. Figure 6 In the figure, (a) is the axial thermal stress comparison of long piles in the pile group; (b) is the axial thermal stress comparison of short piles; (c) is the axial thermal stress comparison of energy piles with larger diameters; (d) is the axial thermal stress comparison of energy piles with smaller diameters. Figure 6It can be found that under different thermal loads, the calculation results and simulation results maintain good consistency, which proves the effectiveness and reliability of the invented method in calculating the thermal-mechanical coupling response of variable stiffness energy pile groups.

[0101] In the embodiments provided by the embodiments of the present invention, the method embodiments described above are merely schematic, for example, the flowcharts and block diagrams in the accompanying drawings show the possible architecture, functions and operations of the methods and computer program products according to the multiple embodiments of the present invention. In this regard, each box in the flowchart or block diagram may represent a module, a program segment or a part of a code, and the module, a program segment or a part of a code contains one or more executable instructions for implementing the specified logical functions. It should also be noted that in some alternative implementations, the functions marked in the box may also occur in an order different from that marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they may sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or the flowchart, and the combination of boxes in the block diagram and / or the flowchart, can be implemented with a dedicated hardware-based system that performs a specified function or action, or can be implemented with a combination of dedicated hardware and computer instructions.

[0102] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0103] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0104] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0105] The "first\second" mentioned in the embodiments is only to distinguish similar objects, and does not represent a specific order for the objects. It is understandable that the "first\second" can be interchanged with the specific order or sequence where permitted. It should be understood that the objects distinguished by "first\second" can be interchanged where appropriate, so that the embodiments described herein can be implemented in an order other than those illustrated or described herein.

[0106] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for calculating the thermal-mechanical coupling response of variable stiffness energy pile groups, characterized in that: The steps include: S1. Select the load transfer model to simulate the pile-soil nonlinear interaction and determine the algorithm for equal stiffness energy pile groups; S2. Determine the type of the variable stiffness energy pile group, calculate the pile side-soil elastic displacement interaction factor considering the pile-pile interaction, and determine the pile side-soil interaction model of the variable stiffness energy pile group; S3, determine the type of the variable stiffness energy pile group, calculate the pile end-soil elastic displacement interaction factor considering the pile-pile interaction, and determine the pile end-soil interaction model of the variable stiffness energy pile group; S4, determine the pile side- and pile tip-soil interaction model parameters; S5. Substitute the pile side- and pile end-soil interaction models of the variable stiffness energy pile group into the equal stiffness energy pile group algorithm to calculate the thermal-mechanical coupling response of the variable stiffness energy pile group.

2. The method for calculating the thermal-mechanical coupling response of variable stiffness energy pile groups according to claim 1 is characterized by: In step S1, the pile-soil relative displacement consists of two parts: nonlinear displacement and elastic displacement; the nonlinear displacement is calculated by the load transfer model, and the elastic displacement is obtained by the relevant principles of the shear displacement method.

3. The method for calculating the thermal-mechanical coupling response of variable stiffness energy pile groups according to claim 2 is characterized by: The load transfer model is an exponential model, a hyperbolic model, a double-broken line model, a three-broken line model or an ideal elastic-plastic model.

4. The method for calculating the thermal-mechanical coupling response of variable stiffness energy pile groups according to claim 1 is characterized by: In step S2, the following steps are specifically included: S21. If the variable stiffness energy pile group type is a variable pile diameter type energy pile group, the pile side-soil elastic displacement interaction factor only considers the replacement of the pile diameter, that is, the pile side-soil interaction model of the variable stiffness energy pile group is obtained; S22. If the type of variable stiffness energy pile group is a variable pile length type energy pile group, the pile side-soil elastic displacement interaction factor of any long pile in the pile group should consider the following six factors: 1) axial displacement caused by the load on itself; 2) displacement increment caused by other long piles in the pile group that are within the influence range of the shear radius; 3) displacement reduction caused by the "reinforcement-curtain" effect of other long piles in the pile group that are within the influence range of the shear radius; 4) displacement increment caused by other short piles in the pile group that are within the influence range of the shear radius; 5) displacement reduction caused by the "reinforcement-curtain" effect of other short piles in the pile group that are within the influence range of the shear radius; 6) displacement increment caused by the pile ends of other short piles in the pile group that are within the influence range of the shear radius; that is, the pile side-soil interaction model of the variable stiffness energy pile group is obtained; S23. If the type of variable stiffness energy pile group is a variable pile length type energy pile group, the pile side-soil elastic displacement interaction factor of any short pile in the pile group should consider the following five factors: 1) axial displacement caused by the load on itself; 2) displacement increment caused by other short piles in the pile group that are within the influence range of the shear radius; 3) displacement reduction caused by the "reinforcement-curtain" effect of other short piles in the pile group that are within the influence range of the shear radius; 4) displacement increment caused by other long piles in the pile group that are within the influence range of the shear radius; 5) displacement reduction caused by the "reinforcement-curtain" effect of other long piles in the pile group that are within the influence range of the shear radius; that is, the pile side-soil interaction model of the variable stiffness energy pile group is obtained.

5. The method for calculating the thermal-mechanical coupling response of variable stiffness energy pile groups according to claim 1 is characterized by: In step S3, the following steps are specifically included: S31. If the variable stiffness energy pile group type is a variable pile diameter type energy pile group, the pile tip-soil elastic displacement interaction factor only considers the replacement of the pile diameter, that is, the pile tip-soil interaction model of the variable stiffness energy pile group is obtained; S32. If the variable stiffness energy pile group type is a variable length type energy pile group, then the pile tip-soil elastic displacement interaction factor of any long pile in the pile group only considers the axial displacement caused by the load on itself, that is, the pile tip-soil interaction model of the variable stiffness energy pile group is obtained; S33. If the type of variable stiffness energy pile group is a variable pile length type energy pile group, the pile end-soil elastic displacement interaction factor of any short pile in the pile group should consider the following two factors: 1) the pile end displacement caused by the load on itself; 2) the reduction of pile end displacement caused by the "reinforcement-curtain" effect of other long piles in the pile group that are located within the influence range of the shear radius; that is, the pile end-soil interaction model of the variable stiffness energy pile group is obtained.

6. The method for calculating the thermal-mechanical coupling response of variable stiffness energy pile groups according to claim 1 is characterized by: In step S4, the model parameters include 1) pile-soil interface shear strength; 2) pile side-soil initial shear stiffness; 3) pile tip ultimate strength; 4) pile tip-soil interaction initial stiffness; 5) pile-raft contact stiffness.

7. The method for calculating the thermal-mechanical coupling response of variable stiffness energy pile groups according to claim 1 is characterized by: In step S5, the equal stiffness energy pile group algorithm comprises the following specific steps: S51, select the load transfer model and pile top contact stiffness to simulate the pile-soil nonlinear interaction; S52. Calculate the pile side- and pile tip-soil elastic displacement interaction factors considering pile-pile interaction; S53, determine the pile side- and pile tip-soil interaction model for equal stiffness energy pile groups; S54, determining pile side- and pile tip-soil interaction model parameters; S55. Substitute the pile side- and pile end-soil interaction models of the equal-stiffness energy pile group into the energy pile single-pile thermal coupling algorithm to obtain the equal-stiffness energy pile group thermal coupling response.

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