Energy pile thermo-mechanical coupling response prediction method and device

Abstract

The application discloses an energy pile thermal-mechanical coupling response prediction method and device, comprising: constructing a pile-soil interaction model; analyzing a pile side cyclic load transfer model and a pile end load transfer model; constructing an energy pile thermal-mechanical response control equation; performing thermal load cycling, analyzing the initial stiffness coefficient in the heating stage, and constructing the initial stiffness matrix; heating the energy pile, and the temperature increment is Δ T x ; deducing the energy pile response and the interface stress state; updating the stiffness coefficient and the stiffness matrix; obtaining the complete load-settlement response and the interface stress state; analyzing the stiffness coefficient in the cooling stage, and constructing the initial stiffness matrix; cooling the energy pile, and the temperature increment is Δ T y ; deducing the energy pile response and the interface stress state; updating the stiffness coefficient and the stiffness matrix; obtaining the performance of the energy pile under the thermal load cycling; the method can be applied to the ground source heat pump system, and can quickly and effectively analyze and evaluate the mechanical response of the pile foundation caused by the cold and heat cycling.

Description

Technical Field

[0001] This invention relates to the field of methods and devices for predicting the thermal-mechanical coupling response of energy piles, and particularly to a method and device for predicting the thermal-mechanical coupling response of energy piles. Background Technology

[0002] With the accelerated global energy structure shift towards low-carbon and green directions, ground source heat pump systems have been widely used as a highly efficient way to utilize renewable energy. Energy piles, as a new engineering technology combining ground source heat pump heat exchange pipes with building pile foundation structures, possess the dual functions of bearing building loads and transferring geothermal energy, and have shown broad application prospects in urban infrastructure construction. The working principle of energy piles is to connect the underground heat source to the building structure through the pile body, facilitating the exchange of geothermal energy. However, during the long-term service of energy piles, due to seasonal temperature changes and variations in system operating conditions, the pile body undergoes alternating cycles of heating and cooling, i.e., it is subjected to thermal cycling loads. This thermo-mechanical coupling effect causes the pile body to exhibit thermal expansion and contraction, leading to a redistribution of axial force, displacement, and stress at the pile-soil interface. Long-term repeated thermal cycling may not only cause cumulative deformation and settlement of the pile body but also weaken the bearing capacity of the pile foundation, thus affecting the long-term safety and service life of the structure. Therefore, accurately analyzing the thermodynamic response characteristics of energy piles under thermal cycling loads is particularly important and has significant theoretical and engineering application value. Currently, existing technologies for analyzing the thermal cycle response of energy piles still suffer from problems such as complex modeling, low computational efficiency, insufficient characterization of interface behavior, and limited prediction accuracy. Summary of the Invention

[0003] The purpose of this invention is to design a method and device for predicting the thermal-mechanical coupling response of energy piles in order to solve the above problems.

[0004] The present invention achieves the above objectives through the following technical solutions:

[0005] The method for predicting the thermo-mechanical coupled response of energy piles includes:

[0006] S1. The energy pile is simplified into an axial one-dimensional rod, and the energy pile is discretized. Nonlinear springs are arranged in the soil around the pile and the soil at the pile tip of the pile unit to form a pile-soil interaction model.

[0007] S2. Apply a mechanical load F to the top of the pile and divide it into n incremental loads. Analyze the pile side cyclic load transfer model and the pile end load transfer model under the pile top load.

[0008] S3. Construct the thermal-mechanical response control equations for energy piles;

[0009] S4. Perform the Nth thermal load cycle, analyze the initial stiffness coefficients of all pile elements in the heating stage, and construct the initial stiffness matrix of the energy pile response.

[0010] S5. Heat the energy pile, with a temperature increment of ΔT. x = (T max -T min x = 1, 2, 3, ..., n;

[0011] S6. Analyze the nodal displacement increment, shear force and axial force increment by midpoint increment method to derive the energy pile response and interface stress state;

[0012] S7. Update the stiffness coefficients of the heating stage based on the energy pile response and interface stress state, and reconstruct the stiffness matrix.

[0013] S8. Determine if the current x is equal to n. If not, proceed to S9; otherwise, obtain the temperature from T. min Increase to T max The complete load-settlement response and interface stress state are then processed before proceeding to S10.

[0014] S9. Let x = x + 1, and return to S5;

[0015] S10. Analyze the initial stiffness coefficients of all pile elements during the cooling and temperature reduction stage, and construct the initial stiffness matrix of the energy pile response.

[0016] S11. Cool the energy pile down, with a temperature increment of ΔT. y = (T min -T max y = 1, 2, 3, ..., n;

[0017] S12. Determine the reference point for the reverse temperature change, analyze the nodal displacement increment, shear force and axial force increment using the midpoint increment method, and derive the energy pile response and interface stress state.

[0018] S13. Update the stiffness coefficients of the cooling and cooling stage based on the energy pile response and interface stress state, and reconstruct the stiffness matrix.

[0019] S14. Determine if the current y is equal to n. If not, proceed to S15; otherwise, obtain the temperature from T. max Reduce to T min The complete load-settlement response and interface stress state are then processed before proceeding to S16.

[0020] S15. Let y = y + 1, and return to S11;

[0021] S16. Determine if N is equal to the preset number of heat load cycles. If yes, obtain the performance of the energy pile under heat load cycles; otherwise, set N=N+1 and return to S4.

[0022] The energy pile thermal-mechanical coupling response prediction device includes:

[0023] Storage; storage contains computer programs;

[0024] Actuator; the actuator is used to execute a computer program stored in the storage, and when the computer program is executed, the energy pile thermal-mechanical coupling response prediction method described above is implemented.

[0025] A computer-readable storage medium includes a computer program stored on the computer-readable storage medium, the computer program being executed by a processor to implement the energy pile thermal-mechanical coupling response prediction method as described above.

[0026] The beneficial effects of this invention are as follows: This method idealizes the soil around and at the pile tip as a series of nonlinear soil spring models, simplifying the analysis of the thermo-mechanical coupling response of the energy pile under actual service conditions. The mechanical performance parameters of each soil spring are assigned based on the subsequently established pile side load transfer model and pile tip load transfer model, thereby effectively characterizing the interaction behavior of the pile-soil interface under thermo-mechanical coupling loads. This method comprehensively considers the thermal expansion and contraction effect of the energy pile under thermal cycling, the vertical and tangential nonlinear mechanical behavior of the pile-soil interface, slip characteristics, and the cyclic evolution mechanism of frictional resistance. By reasonably simplifying the thermal-mechanical control equations of the energy pile and introducing an interface nonlinear constitutive model, a set of engineering analysis schemes with both high accuracy and high computational efficiency is established. It can be applied to ground source heat pump systems for rapid and effective analysis and evaluation of the mechanical response of pile foundations caused by thermal cycling. It is particularly suitable for engineering projects with complex geological conditions, a large number of pile foundations, or those requiring rapid assessment of the service status of pile foundations, and has good promotion value and applicability in engineering applications. Attached Figure Description

[0027] Figure 1 This invention relates to the pile-soil interaction model of the energy pile thermo-mechanical coupling response prediction method.

[0028] Figure 2 This is a schematic diagram of the energy pile-soil interaction model during the cold and heat cycle of this invention;

[0029] Figure 3 This is a schematic diagram of the deformation of pile unit i and the surrounding soil in this invention;

[0030] Figure 4 This is a flowchart of the thermal response calculation for energy piles;

[0031] Figure 5It is the normalized pile head settlement caused by thermal cycling under different mechanical loads;

[0032] Figure 6 It is the normalized pile head settlement caused by different cycle temperatures. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0035] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0036] In the description of this invention, it should be understood that the terms "upper," "lower," "inner," "outer," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0037] Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0038] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, terms such as "set" and "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0039] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0040] During the analysis, the load on the energy pile is decomposed into mechanical load F and thermal cycle load T, and applied to the pile body in sequence.

[0041] During the structural load application stage: when a mechanical load F is applied to the top of the pile, the pile body generates upward surface frictional resistance along the depth direction, and the pile end generates upward end resistance;

[0042] Cooling stage: As the temperature decreases, the pile body cools and contracts, resulting in an increase in surface friction at the pile-soil interface at the top of the pile; while the surface friction at the bottom of the pile decreases, and may even reverse direction (from upward to downward); the end resistance of the pile decreases as the pile body contracts; during this process, a neutral point (NP) is formed along the depth of the pile body, at which the pile-soil interface is neither loaded nor unloaded.

[0043] Heating stage: As the temperature rises, the pile expands thermally, the frictional resistance at the upper pile-soil interface decreases or even reverses; the frictional resistance at the lower pile-soil interface increases; the pile end resistance also increases; during the thermal cycle, the position of the neutral point (NP) dynamically shifts with temperature changes.

[0044] Complete thermal cycle effect: After a complete heating-cooling cycle, the loading and unloading states at different depths of the pile-soil interface exhibit asynchronous evolution characteristics; this characteristic leads to dynamic changes in the mechanical response mode of the pile along the depth direction, demonstrating a typical thermo-mechanical coupling effect.

[0045] The method for predicting the thermo-mechanical coupled response of energy piles includes:

[0046] S1, such as Figure 1 As shown, the energy pile is simplified as an axial one-dimensional rod, and the energy pile is discretized. Nonlinear springs are arranged in the soil around the pile element and the soil at the pile tip to construct a pile-soil interaction model, as shown. Figure 2 As shown, the soil around and at the pile tip is idealized as a series of nonlinear soil spring models, simplifying the thermo-mechanical coupling response analysis of the energy pile under actual service conditions. The mechanical performance parameters of each soil spring are assigned based on the subsequently established pile side load transfer model and pile tip load transfer model, thereby effectively characterizing the interaction behavior of the pile-soil interface under thermo-mechanical coupling loads. Figure 2 In the model, nonlinear soil spring elements are arranged along the pile perimeter and pile end directions, with the axial structure of the energy pile as the center. The stress and deformation state of the soil springs at each position during the application of thermal-mechanical loads are intuitively displayed by arrows and mechanical parameter annotations.

[0047] S2. Apply a mechanical load F to the top of the pile and divide it into n incremental loads. Analyze the pile side cyclic load transfer model and the pile end load transfer model under the pile top load.

[0048] Based on the interface constitutive model proposed by Liu and Ling (2008), the pile-side cyclic load transfer model constructed by this method is expressed as follows:

[0049] ;

[0050] ;

[0051] ;

[0052] ;

[0053] ;

[0054] ;

[0055] ;

[0056] ;

[0057] ;

[0058] Based on hyperbolic functions and Massin's criterion, the pile end load transfer model constructed by this method is expressed as follows:

[0059] ;

[0060] ;

[0061] ;

[0062] ;

[0063] ;

[0064] ;

[0065] ;

[0066] ;

[0067] In the formula, τ s and u s These represent the tangential stress and displacement at the pile-soil interface, respectively; σ n and ν n α represents normal stress and displacement; t represents the shear band thickness at the interface; R is the radius of the pile; αpn ΔT is the normal thermal expansion coefficient of the pile; K is the temperature increment. n Indicates normal stiffness; c1 and c2 are model parameters; k represents state parameters; W p W represents the cumulative plastic work. th ᵣ represents the threshold of plastic work; ε n p and ε s p D represents the plastic strain in the normal and tangential directions, respectively; s0 and D n0 The initial stiffness is given by p; e and e0 are the current and initial void ratios, respectively; p is the initial stiffness. a For reference atmospheric pressure; D nn D ns D ss and D sn These are the stiffness matrix elements of the interface constitutive model, derived from the specified interface constitutive model. b and τ b These represent the pile tip displacement and unit resistance, respectively; f and g are model parameters; u br and τ br These represent the corresponding displacement and unit resistance of the pile tip under different loading conditions, respectively; ζ is the scaling factor; ν and G b These are Poisson's ratio and shear modulus of the soil at the pile tip, respectively; R bf It is the reduction factor for unit end resistance, typically ranging from 0.8 to 0.95, τ. bu D represents the limit unit end resistance; r It is the relative density of the soil, e max and e min These represent the maximum and minimum void ratios of the soil; c′ is the effective cohesion of the soil; N c and N q This is the bearing capacity coefficient.

[0068] S3. Construct the thermal-mechanical response control equations for the energy pile; specifically including:

[0069] The deformation of pile unit i and the surrounding soil is as follows: Figure 3 As shown. Under thermal loading, the increment of unit shear resistance (Δτ) generated by the pile element. s The pile load will cause shear displacement of the surrounding soil. Soil deformation caused by pile load can be divided into two parts: one is the nonlinear deformation (Δu) of the weak pile-soil interface. s Secondly, the elastic deformation (Δu) of the surrounding soil outside the interface. e ,ᵢ). Among them, the interface deformation is calculated using the pile side load transfer model, while the elastic deformation of the soil outside the interface is evaluated using the shear displacement method proposed by Randolph and Wroth (1979).

[0070] The axial mechanical equilibrium equation of pile element i is expressed as: ;in, ;

[0071] Considering the mechanical and thermal deformation of pile element i, the equilibrium equation for the axial displacement is expressed as: ; where ΔT i Let α be the temperature increment of the i-th pile segment. ps The tangential thermal expansion coefficient of the pile;

[0072] According to the equilibrium equation of axial displacement, the incremental axial force of pile elements i and i+1 is expressed as: , in, , , ;

[0073] The matrix form of the governing equations for calculating pile deformation is as follows: ;

[0074] Where, {Δu p} represents the incremental node displacement vector, in the form {Δu p}={Δu p ,1,Δu p ,2,…,Δu p ,ᵢ,…,Δu p , m ,Δu p , m ₊1}ᵀ;{ΔF} represents the incremental load vector, expressed as: {ΔF}={ΔF1,0,…,0,…,0,0}ᵀ;{ΔC} represents the incremental heat load vector, expressed as: {ΔC}={C1,C1−C2,…,Cᵢ₋1−Cᵢ,…,C m ₋1−C m C m}ᵀ.

[0075] S4. Perform the Nth thermal load cycle and analyze the initial stiffness coefficient k of all pile elements during the heating stage. s,i (0) and k b (0), and construct the initial stiffness matrix of the energy pile response; the initial stiffness matrix of the pile-soil interaction model is expressed as: .

[0076] Mechanical and thermal loads are applied to the energy pile incrementally. At each step, the energy pile's response is calculated, and the stiffness matrix is ​​updated accordingly. By accumulating the axial forces, side drags, and deformations at each node in each incremental step, the overall behavior of the energy pile under different thermo-mechanical coupling load conditions can be accurately determined.

[0077] S5. Heat the energy pile, with a temperature increment of ΔT. x = (T max -T min x = 1, 2, 3, ..., n;

[0078] S6. Analyze the nodal displacement increment, shear force, and axial force increment using the midpoint increment method to derive the energy pile response and interface stress state. The energy pile response includes u... p,i (x), P i (x) and Q p,i (x), the interface stress state includes τ s,i (x), σ n,i (x);

[0079] S7. Update the stiffness coefficient k during the heating stage based on the energy pile response and interface stress state. s,i (x) and k b (x), and reconstruct the stiffness matrix K p (x);

[0080] S8. Determine if the current x is equal to n. If not, proceed to S9; otherwise, obtain the temperature from T. min Increase to T max The complete load-settlement response (u p,i (n), P i (n), Q p,i (n) and interfacial stress state (τ) s,i (n), σ n,i (n)), then enter S10;

[0081] S9. Let x = x + 1, and return to S5;

[0082] S10. Analyze the initial stiffness coefficients of all pile elements during the cooling and temperature reduction stage, and construct the initial stiffness matrix of the energy pile response.

[0083] S11. Cool the energy pile down, with a temperature increment of ΔT. y = (T min -T max y = 1, 2, 3, ..., n;

[0084] S12. Determine the reference point for the reverse temperature change, analyze the nodal displacement increment, shear force and axial force increment using the midpoint increment method, and derive the energy pile response and interface stress state.

[0085] S13. Update the stiffness coefficients of the cooling and cooling stage based on the energy pile response and interface stress state, and reconstruct the stiffness matrix.

[0086] S14. Determine if the current y is equal to n. If not, proceed to S15; otherwise, obtain the temperature from T. max Reduce to T min The complete load-settlement response is then processed before proceeding to S16;

[0087] S15. Let y = y + 1, and return to S11;

[0088] S16. Determine if N is equal to the preset number of heat load cycles. If yes, obtain the performance of the energy pile under heat load cycles; otherwise, set N=N+1 and return to S4.

[0089] The above process is in accordance with Figure 4 The flowchart shown illustrates how iterative calculations can be implemented using MATLAB programming and developed into an app to evaluate the thermo-mechanical behavior of energy piles.

[0090] The pile-soil interaction model of this method has the following innovative features:

[0091] Introducing the thermally induced radial deformation effect: The radial expansion or contraction effect of the energy pile caused by temperature changes is incorporated into the analysis process. Through the coupling mechanism of pile thermal deformation and pile-soil interface reaction, the accuracy of predicting the service behavior of energy piles under thermal cycling conditions is improved.

[0092] Refining the Nonlinear Slip Behavior of the Pile-Soil Interface: Under thermo-mechanical coupling, the loading, unloading, and reloading paths of the pile-soil interface exhibit significant nonlinear characteristics. This model accurately captures the mechanical response process of the pile-soil interface at different loading stages by meticulously simulating the linkage effect between the evolution of skin friction and the change of normal stress.

[0093] Adaptable to different geological conditions and load paths: Since this scheme supports the free replacement of different soil-structure interface constitutive relationships, it can be customized according to the actual soil conditions, energy pile size parameters and thermal-power load path characteristics, thus possessing wide engineering applicability and flexibility.

[0094] Storage; storage contains computer programs;

[0095] Actuator; the actuator is used to execute a computer program stored in the storage, and when the computer program is executed, the energy pile thermal-mechanical coupling response prediction method described above is implemented.

[0096] A computer-readable storage medium includes a computer program stored on the computer-readable storage medium, the computer program being executed by a processor to implement the energy pile thermal-mechanical coupling response prediction method as described above.

[0097] Instance Computing

[0098] This study investigates the effects of pile head load and pile body temperature on the thermal and thermal cycling responses of an energy pile through a case study. The pile diameter is 1 m and the pile length is 20 m. The pile material is assumed to be a linear elastic body with the following mechanical parameters: elastic modulus E. p =30 GPa, Poisson's ratio ν p =0.2. For the thermo-mechanical analysis of the energy pile, the thermal parameters of the pile material are set as follows: thermal expansion coefficient α = 1 × 10⁻ 5 1 / °C; thermal conductivity k = 1.8 W / (m·K); specific heat capacity c = 880 J / (kg·K). The soil surrounding the energy pile is modeled as an elasto-plastic material following the Mohr-Coulomb failure criterion, with the following mechanical parameters: elastic modulus E s =100 MPa, Poisson's ratio ν s =0.30, unit weight γ=18 kN / m³. For the pile-side-soil interface (pile-side-soil interaction), the developed pile-side load transfer model is adopted, and the model parameters are shown in Table 1. For the pile-end-soil interface (pile-end-soil interaction), the pile-end load transfer model is adopted, and the contact parameters are set as follows: initial normal pressure p0=120 MPa, contact gap c0=0.005 mm.

[0099] Table 1 shows the parameters of the pile-soil interface model.

[0100]

[0101] The temperature-displacement curves at the pile top under different pile top loads and thermal cycles (20℃→35℃→5℃→20℃) are shown below. Figure 5 As shown.

[0102] F=0.6P ult Normalized pile head settlement diagrams at different cyclic temperatures (∆T = ±5℃, ±10℃, ±15℃, ±20℃), as shown below. Figure 6 As shown.

[0103] This method comprehensively considers the thermal expansion and contraction effects of energy piles under thermal cycling, the vertical and tangential nonlinear mechanical behavior of the pile-soil interface, slip characteristics, and the cyclic evolution mechanism of frictional resistance. By reasonably simplifying the thermal-mechanical control equations of the energy piles and introducing an interface nonlinear constitutive model, a set of engineering analysis schemes with both high accuracy and high computational efficiency is established. This technical solution is applicable to ground source heat pump systems, enabling rapid and effective analysis and evaluation of the mechanical response of pile foundations caused by thermal cycling. It is particularly suitable for engineering projects with complex geological conditions, a large number of pile foundations, or those requiring rapid assessment of pile foundation service status, and has good promotional value and applicability in engineering applications.

[0104] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A method for predicting the thermo-mechanical coupled response of energy piles, characterized in that, include: S1. The energy pile is simplified into an axial one-dimensional rod, and the energy pile is discretized. Nonlinear springs are arranged in the soil around the pile and the soil at the pile tip of the pile unit to form a pile-soil interaction model. S2. Apply a mechanical load F to the pile top and divide it into n incremental loads. Analyze the pile-side cyclic load transfer model and the pile-end load transfer model under the pile-top load; specifically: The pile-side cyclic load transfer model is represented as follows: ； ； ； ； ； ； ； ； ； The load transfer model at the pile end is represented as follows: ； ； ； ； ； ； ； ； In the formula, and These represent the tangential stress and displacement at the pile-soil interface, respectively. and Represents normal stress and displacement; t represents the shear band thickness at the interface; R is the radius of the pile; The normal thermal expansion coefficient of the pile; This represents the temperature increment. Indicates normal stiffness; and For model parameters; k represents state parameters; This represents the accumulated plastic work. The threshold representing plastic work; and These represent the plastic strain in the normal and tangential directions, respectively; and For initial stiffness; e and The current and initial porosity ratios; For reference atmospheric pressure; , , and These are the stiffness matrix elements of the interface constitutive model, derived from the specified interface constitutive model; and These represent the pile tip displacement and unit resistance, respectively; f and g are model parameters. and These represent the corresponding displacement and unit resistance of the pile tip under different loading conditions, respectively. It is a scaling factor; v and These are Poisson's ratio and shear modulus of the soil at the pile tip, respectively. It is a reduction factor for unit end resistance, with a value between 0.8 and 0.

95. Indicates the end resistance of the limit unit; It is the relative density of the soil. and These are the maximum and minimum void ratios of the soil, respectively. It is the effective cohesion of the soil; and This is the bearing capacity coefficient; S3. Construct the thermal-mechanical response control equations for energy piles; S4. Perform the Nth thermal load cycle, analyze the initial stiffness coefficients of all pile elements in the heating stage, and construct the initial stiffness matrix of the energy pile response. S5. Heat the energy pile, with a temperature increment of [value missing]. n is a positive integer, x = 1, 2, 3, ..., n; S6. Analyze the nodal displacement increment, shear force and axial force increment by midpoint increment method to derive the energy pile response and interface stress state; S7. Update the stiffness coefficients of the heating stage based on the energy pile response and interface stress state, and reconstruct the stiffness matrix. S8. Determine if the current x is equal to n. If not, proceed to S9; otherwise, obtain the temperature from... Increase to The complete load-settlement response and interface stress state are then processed before proceeding to S10. S9. Let x = x + 1, and return to S5; S10. Analyze the initial stiffness coefficients of all pile elements during the cooling and temperature reduction stage, and construct the initial stiffness matrix of the energy pile response. S11. Cool the energy pile to reduce its temperature. The temperature increment during cooling is: n is a positive integer, y = 1, 2, 3, ..., n; S12. Determine the reference point for the reverse temperature change, analyze the nodal displacement increment, shear force and axial force increment through the midpoint increment method, and derive the energy pile response and interface stress state. S13. Update the stiffness coefficients of the cooling and cooling stage based on the energy pile response and interface stress state, and reconstruct the stiffness matrix. S14. Determine if the current y is equal to n. If not, proceed to S15; otherwise, obtain the temperature from... Reduce to The complete load-settlement response is then processed before proceeding to S16; S15. Let y = y + 1, and return to S11; S16. Determine if N is equal to the preset number of heat load cycles. If yes, obtain the performance of the energy pile under heat load cycles; otherwise, set N=N+1 and return to S4.

2. The method for predicting the thermo-mechanical coupling response of energy piles according to claim 1, characterized in that, In S3, the axial mechanical equilibrium equation of pile element i is expressed as: ;in, ; Considering the mechanical and thermal deformation of pile element i, the equilibrium equation for the axial displacement is expressed as: In the formula The temperature increment of the i-th pile segment. is the tangential thermal expansion coefficient of the pile; According to the equilibrium equation of axial displacement, the incremental axial force of pile elements i and i+1 is expressed as: , in, , , ; The matrix form of the governing equations for calculating pile deformation is as follows: ; in, The incremental node displacement vector is represented as follows: ; The incremental load vector is represented as: ; The incremental heat load vector is represented as: .

3. The method for predicting the thermo-mechanical coupling response of energy piles according to claim 2, characterized in that, The initial stiffness matrix of the pile-soil interaction model is expressed as: .

4. A thermal-mechanical coupling response prediction device for energy piles, characterized in that, include: Storage; The memory stores computer programs; Actuator; The actuator is used to execute a computer program stored in the storage, and when executing the computer program, it implements the energy pile thermal-mechanical coupling response prediction method as described in any one of claims 1-3.

5. A computer-readable storage medium, characterized in that, include: The computer-readable storage medium stores a computer program that is executed by a processor to implement the energy pile thermal-mechanical coupling response prediction method as described in any one of claims 1-3.

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