Energy pile thermal-mechanical coupling response prediction method and device

Abstract

The invention discloses an energy pile heat-force coupling response prediction method and device. The method comprises the steps that a pile-soil interaction model is constructed and formed; analyzing the pile side cyclic load transfer model and the pile end load transfer model; constructing an energy pile heat-force response control equation; carrying out thermal load circulation, analyzing an initial rigidity coefficient in a heating stage, and constructing an initial rigidity matrix; the energy pile is heated, and the temperature increment is delta Tx; deducing an energy pile response and an interface stress state; updating the rigidity coefficient and the rigidity matrix; a complete load-settlement response and an interface stress state are obtained; the rigidity coefficient of the cooling stage is analyzed, and an initial rigidity matrix is constructed; the energy pile is cooled, and the temperature increment is delta Ty; deducing an energy pile response and an interface stress state; updating a stiffness coefficient and reconstructing a stiffness matrix; the performance of the energy pile under the thermal load cycle is obtained; the method can be applied to a ground source heat pump system, and mechanical response of the pile foundation caused by thermal and cold cycling can be quickly and effectively analyzed and evaluated.

Description

Technical Field

[0001] The present invention relates to the field of energy pile thermal-mechanical coupling response prediction methods and devices, and in particular to an energy pile thermal-mechanical coupling response prediction method and device. Background Art

[0002] As the global energy structure accelerates its transition toward a low-carbon, green energy future, ground-source heat pump systems have gained widespread application as a highly efficient renewable energy source. Energy piles, a novel engineering technology that integrates ground-source heat pump heat exchange tubes with building pile foundations, have the dual functions of bearing building loads and transferring geothermal energy, demonstrating promising applications 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, exchanging geothermal energy. However, over the long-term service life of energy piles, due to seasonal temperature fluctuations and system operating conditions, the pile body undergoes alternating cycles of heating and cooling, resulting in thermal cycling loads. This thermal-mechanical coupling causes the pile body to expand and contract due to thermal expansion and contraction, leading to redistribution of axial forces, displacements, and pile-soil interface stresses. Long-term, repeated thermal cycling can not only lead to cumulative deformation and settlement of the pile body, but can also weaken the bearing capacity of the pile foundation, thereby 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 crucial and holds great theoretical and engineering application value. In the current existing technology, the thermal cycle response analysis method of energy piles still has problems such as complex modeling, low calculation efficiency, insufficient characterization of interface behavior and limited prediction accuracy. Summary of the Invention

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

[0004] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0005] The prediction method of thermal-mechanical coupled response of energy piles includes:

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

[0007] 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.

[0008] S3. Construct the thermal-mechanical response control equation of the energy pile;

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

[0010] S5. Heat the energy pile, and the heating temperature increment is ΔT x =(T max -T min ) / n, n is a positive integer, x=1,2,3,...,n;

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

[0012] S7, updating the stiffness coefficient in the heating stage according to the energy pile response and the interface stress state, and reconstructing the stiffness matrix;

[0013] S8, determine whether the current x is equal to n, if not, enter S9, otherwise, obtain the temperature from T min Increase to T max The complete load-settlement response and interface stress state are then entered into S10;

[0014] S9. Set x = x + 1 and return to S5.

[0015] S10, analyzing the initial stiffness coefficients of all pile units in the cooling stage, and constructing the initial stiffness matrix of the energy pile response;

[0016] S11. Cool the energy pile. The temperature increment of cooling is ΔT. y =(T min -T max ) / n, n is a positive integer, y=1,2,3,...,n;

[0017] S11. Determine the reference point for reverse temperature change, analyze the node displacement increment, shear force and axial force increment by the midpoint increment method, and derive the energy pile response and interface stress state;

[0018] S12, updating the stiffness coefficient in the cooling stage according to the energy pile response and the interface stress state, and reconstructing the stiffness matrix;

[0019] S13, determine whether the current y is equal to n, if not, enter S14, otherwise, obtain the temperature from T max Reduce to T min The complete load-settlement response and interface stress state are then entered into S15;

[0020] S14. Set y = y + 1 and return to S11.

[0021] S15. Determine whether N is equal to the preset number of thermal load cycles. If so, obtain the performance of the energy pile under the thermal load cycle; otherwise, set N=N+1 and return to S4.

[0022] Energy pile thermal-mechanical coupling response prediction device, including:

[0023] Storage; storage storing a computer program;

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

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

[0026] The beneficial effects of the present invention are as follows: This method idealizes the soil around and at the pile end into a series of nonlinear soil spring models, simplifying the analysis of the thermal-mechanical coupling response of energy piles 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 end load transfer model, thereby effectively characterizing the interaction behavior of the pile-soil interface under the action of thermal-mechanical coupling loads. This method comprehensively considers the thermal expansion and contraction effects of energy piles under the action of hot and cold cycles, the nonlinear mechanical behavior of the pile-soil interface in the vertical and tangential directions, the slip characteristics, and the cyclic evolution mechanism of friction resistance. By rationally simplifying the thermal-mechanical control equations of the energy pile and introducing a nonlinear constitutive model of the interface, a set of engineering analysis solutions with high accuracy and high computational efficiency is established. It can be applied to ground-source heat pump systems to quickly and effectively analyze and evaluate the mechanical response of pile foundations caused by hot and cold cycles. It is particularly suitable for engineering projects with complex geological conditions, a large number of pile foundations, or where the service status of pile foundations needs to be quickly evaluated. It has good promotion value and applicability in engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is the pile-soil interaction model of the energy pile thermal-mechanical coupling response prediction method of the present invention;

[0028] Figure 2 Schematic diagram of the energy pile-soil interaction model during the hot and cold cycle of the present invention;

[0029] Figure 3 Schematic diagram of the deformation of the pile unit i and the surrounding soil of the present invention;

[0030] Figure 4 This is the flow chart for calculating the thermal response of energy piles;

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

[0032] Figure 6 is the normalized pile head settlement caused by different cycle temperatures. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the embodiments of the present invention. It should be understood that the described embodiments are only a portion of the embodiments of the present invention, not all of them. Generally, the components of the embodiments of the present invention described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations.

[0034] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0035] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0036] In the description of the present invention, it should be understood that the terms "upper", "lower", "inside", "outside", "left", "right", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the inventive product is conventionally placed when in use, or are the orientations or positional relationships conventionally understood by those skilled in the art. These are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0037] Furthermore, the terms “first”, “second”, etc. are merely used for distinguishing descriptions and should not be understood as indicating or implying relative importance.

[0038] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, terms such as "disposed" and "connected" should be understood in a broad sense. For example, "connected" can mean 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 also mean internal communication between two components. Those skilled in the art will be able to understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0039] The specific embodiments of the present invention are described in detail below 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 pile top, the pile body forms an upward surface friction resistance along the depth direction, and the pile end generates an upward end resistance;

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

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

[0044] Complete thermal cycle effect: After a complete heating-cooling cycle, the loading and unloading states at each depth of the pile-soil interface exhibit asynchronous evolution characteristics; this characteristic causes the mechanical response pattern of the pile to change dynamically along the depth direction, reflecting a typical thermal-mechanical coupling effect.

[0045] The prediction method of thermal-mechanical coupled response of energy piles includes:

[0046] S1, such as Figure 1 As shown in , the energy pile is simplified into an axial one-dimensional rod, and the energy pile is discretized. Nonlinear springs are arranged around the pile and at the pile end of the pile unit to construct a pile-soil interaction model, as shown in Figure 2 As shown in the figure, the soil around the pile and at the pile end is idealized as a series of nonlinear soil spring models, which simplifies the thermal-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 end load transfer model, thereby effectively characterizing the interaction behavior of the pile-soil interface under the action of thermal-mechanical coupling loads. Figure 2 In the figure, with the axial structure of the energy pile as the center, nonlinear soil spring units are arranged along the pile circumference and pile end directions respectively. The stress and deformation states of the soil springs at various positions during the application of thermal-mechanical loads are intuitively displayed through arrows and mechanical parameter annotations.

[0047] 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.

[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:

[0049] ;

[0050] ;

[0051] ;

[0052] ;

[0053] ;

[0054] ;

[0055] ;

[0056] ;

[0057] ;

[0058] Based on the hyperbolic function and the Masin criterion, the pile tip load transfer model constructed by this method is expressed as:

[0059] ;

[0060] ;

[0061] ;

[0062] ;

[0063] ;

[0064] ;

[0065] ;

[0066] ;

[0067] Where, and u s denote the tangential stress and displacement at the pile-soil interface respectively; σ n and ν n represents normal stress and displacement; t represents the thickness of the shear band at the interface; R is the radius of the pile; αpn is the normal thermal expansion coefficient of the pile; ΔT is the temperature increment; K n represents normal stiffness; c1 and c2 are model parameters; k represents state parameter; W p represents the accumulated plastic work, W thr represents the threshold value of plastic work; and denote the plastic strains in the normal and tangential directions, respectively; and is the initial stiffness; e and e0 are the current and initial void ratios; p a is the reference atmospheric pressure; D nn 、D ns 、D ss and D sn is the stiffness matrix element of the interface constitutive model, which is derived from the specified interface constitutive model. b and τ b represent the pile tip displacement and unit resistance respectively; f and g are model parameters; u br and denote the corresponding displacement and unit resistance of the pile tip under different loading conditions; ζ is the proportional factor; ν and G b are the Poisson's ratio and shear modulus of the soil at the pile tip; R bf It is the reduction coefficient of unit end resistance, usually ranging from 0.8 to 0.95. Indicates the ultimate unit end resistance; D r is the relative density of the soil, e max and e min are the maximum and minimum void ratios of the soil, respectively; c′ is the effective cohesion of the soil; N c and N q is the bearing capacity coefficient.

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

[0069] The deformation of pile unit i and its surrounding soil is as follows: Figure 3 As shown in Figure 2. Under thermal-mechanical loading, the unit shear resistance increment generated by the pile element is It will cause shear displacement of the surrounding soil. The soil deformation caused by pile load can be divided into two parts: one is the nonlinear deformation of the pile-soil weak interface (Δu s,i ), and the second is the elastic deformation of the surrounding soil outside the interface (Δu e,i The interface deformation is calculated using the pile side load transfer model, and 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 deformation and thermal deformation of pile element i, the equilibrium equation of axial displacement is expressed as: Where ΔT i is the temperature increment of the pile in section i, α ps is 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 control equation for calculating pile deformation is expressed as: ;

[0074] Among them, {Δu p} represents the incremental node displacement vector, in the form of {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 thermal load vector, which is expressed as: {ΔC}={C1,C1−C2,…,C i-1 −C i ,…,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 units in 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 pile incrementally. At each step, the pile's response is calculated, and the stiffness matrix is ​​updated accordingly. By summing the axial forces, lateral resistances, and deformations at each node in each incremental step, the pile's overall behavior under various coupled thermal-mechanical loading conditions can be accurately determined.

[0077] S5. Heat the energy pile, and the heating temperature increment is ΔT x =(T max -T min ) / n, n is a positive integer, x=1,2,3,...,n;

[0078] S6. Analyze the node displacement increment, shear force and axial force increment by the midpoint increment method, and 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 , σ n,i (x);

[0079] S7. Update the stiffness coefficient k in the heating phase according to 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 whether the current x is equal to n, if not, enter 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 the interfacial stress state , σ n,i (n)), then enter S10;

[0081] S9. Set x = x + 1 and return to S5.

[0082] S10, analyzing the initial stiffness coefficients of all pile units in the cooling stage, and constructing the initial stiffness matrix of the energy pile response;

[0083] S11. Cool the energy pile. The temperature increment of cooling is ΔT. y =(T min -T max ) / n, n is a positive integer, y=1, 2, 3, ..., n;

[0084] S11. Determine the reference point for reverse temperature change, analyze the node displacement increment, shear force and axial force increment by the midpoint increment method, and derive the energy pile response and interface stress state;

[0085] S12, updating the stiffness coefficient in the cooling stage according to the energy pile response and the interface stress state, and reconstructing the stiffness matrix;

[0086] S13, determine whether the current y is equal to n, if not, enter S14, otherwise, obtain the temperature from T max Reduce to T min The complete load-settlement response, then enter S15;

[0087] S14. Set y = y + 1 and return to S11.

[0088] S15. Determine whether N is equal to the preset number of thermal load cycles. If so, obtain the performance of the energy pile under the thermal load cycle; otherwise, set N=N+1 and return to S4.

[0089] The above process follows Figure 4 The flowchart shown was programmed in MATLAB and developed into an app to implement iterative calculations for evaluating 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 the thermal deformation of the pile body and the pile-soil interface reaction, the accuracy of predicting the service behavior of the energy pile under thermal cycling conditions is improved.

[0092] Refine the nonlinear slip behavior of the pile-soil interface: Under thermal-mechanical coupling, the loading, unloading, and reloading paths of the pile-soil interface exhibit significant nonlinear characteristics. This model accurately captures the mechanical response of the pile-soil interface at different loading stages by carefully simulating the interaction between the evolution of frictional resistance and the changes in normal stress.

[0093] Adaptability to different geological conditions and load paths: Since this solution supports the free replacement of different soil-structure interface constitutive relationships, it can be personalized according to the actual soil conditions of the site, energy pile size parameters, and thermal-mechanical load path characteristics, with wide engineering applicability and flexibility.

[0094] Storage; storage storing a computer program;

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

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

[0097] Example calculation

[0098] Through case calculation, the influence of pile head load and pile body temperature on the thermal response and thermal cycle response of energy pile is discussed. The pile diameter is 1 m and the pile length is 20 m. Assuming that the pile material is a linear elastic body, its mechanical parameters are: elastic modulus E p =30 GPa, Poisson's ratio ν p =0.2. For the thermo-mechanical analysis of energy piles, the thermal parameters of the pile material are set as follows: thermal expansion coefficient α = 1×10 -5 1 / °C; thermal conductivity k=1.8W / (m·K); specific heat capacity c=880J / (kg·K). The soil surrounding the energy pile is modeled as an elastic-plastic material that follows the Mohr-Coulomb failure criterion, and its mechanical parameters are: 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), a developed pile-side load transfer model was used; model parameters are shown in Table 1. For the pile-tip-soil interface (pile-tip-soil interaction), a pile-tip load transfer model was used, with contact parameters set as: initial normal pressure p0 = 120 MPa, contact gap c0 = 0.005 mm.

[0099] Table 1 is the pile-soil interface model parameter table

[0100]

[0101] The temperature-displacement curves at the pile top produced by thermal cycles (20℃→35℃→5℃→20℃) under different pile top loads are shown in Figure 2. Figure 5 shown.

[0102] F=0.6P ult Normalized pile head settlement diagrams at different cycle temperatures (ΔT = ±5℃, ±10℃, ±15℃, ±20℃) are shown in Figure 2. Figure 6 shown.

[0103] This method comprehensively considers the thermal expansion and contraction effects of energy piles under hot and cold cycles, the vertical and tangential nonlinear mechanical behavior of the pile-soil interface, the slip characteristics, and the cyclic evolution mechanism of friction resistance. By rationally simplifying the thermal-mechanical control equations of the energy piles and introducing a nonlinear constitutive model of the interface, a set of engineering analysis solutions with high accuracy and high computational efficiency has been established. This technical solution is applicable to ground-source heat pump systems and can quickly and effectively analyze and evaluate the mechanical response of pile foundations caused by hot and cold cycles. It is particularly suitable for engineering projects with complex geological conditions, a large number of pile foundations, or where the service status of pile foundations needs to be quickly evaluated. It has good promotion value and applicability in engineering applications.

[0104] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. Any technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. The method for predicting the thermal-mechanical coupling response of energy piles is characterized by: include: S1. The energy pile is simplified into an axial one-dimensional rod and discretized. Nonlinear springs are arranged in the soil around the pile unit and the soil at the pile end to construct 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. S3. Construct the thermal-mechanical response control equation of the energy pile; S4. Perform the Nth thermal load cycle, analyze the initial stiffness coefficients of all pile units in the heating stage, and construct the initial stiffness matrix of the energy pile response; S5. Heat the energy pile, and the heating temperature increment is ΔT x =(T max -T min ) / n, n is a positive integer, x=1, 2, 3,..., n; S6. Analyze the node displacement increment, shear force and axial force increment by the midpoint increment method to derive the energy pile response and interface stress state; S7, updating the stiffness coefficient in the heating stage according to the energy pile response and the interface stress state, and reconstructing the stiffness matrix; S8, determine whether the current x is equal to n, if not, enter S9, otherwise, obtain the temperature from T min Increase to T max The complete load-settlement response and interface stress state are then entered into S10; S9. Set x = x + 1 and return to S5. S10, analyzing the initial stiffness coefficients of all pile units in the cooling stage, and constructing the initial stiffness matrix of the energy pile response; S11. Cool the energy pile. The temperature increment of cooling is ΔT. y =(T min -T max ) / n, n is a positive integer, y=1, 2, 3, ..., n; S11. Determine the reference point for reverse temperature change, analyze the node displacement increment, shear force and axial force increment by the midpoint increment method, and derive the energy pile response and interface stress state; S12, updating the stiffness coefficient in the cooling stage according to the energy pile response and the interface stress state, and reconstructing the stiffness matrix; S13, determine whether the current y is equal to n, if not, enter S14, otherwise, obtain the temperature from T max Reduce to T min The complete load-settlement response, then enter S15; S14. Set y = y + 1 and return to S11. S15. Determine whether N is equal to the preset number of thermal load cycles. If so, obtain the performance of the energy pile under the thermal load cycle; otherwise, set N=N+1 and return to S4.

2. The method for predicting the thermal-mechanical coupling response of an energy pile according to claim 1, characterized in that: The pile side cyclic load transfer model is expressed as: ； ； ； ； ； ； ； ； ； The pile tip load transfer model is expressed as: ； ； ； ； ； ； ； ； Where, and u s denote the tangential stress and displacement at the pile-soil interface respectively; σ n and ν n represents normal stress and displacement; t represents the thickness of the shear band at the interface; R is the radius of the pile; α pn is the normal thermal expansion coefficient of the pile; ΔT is the temperature increment; K n represents normal stiffness; c1 and c2 are model parameters; k represents state parameter; W p represents the accumulated plastic work, W thr represents the threshold value of plastic work; and denote the plastic strains in the normal and tangential directions, respectively; and is the initial stiffness; e and e0 are the current and initial void ratios; p a is the reference atmospheric pressure; D nn 、D ns 、D ss and D sn is the stiffness matrix element of the interface constitutive model, which is derived from the specified interface constitutive model; u b and represent the pile tip displacement and unit resistance respectively; f and g are model parameters; u br and denote the corresponding displacement and unit resistance of the pile tip under different loading conditions; ζ is the proportional factor; ν and G b are the Poisson's ratio and shear modulus of the soil at the pile tip; R bf It is the reduction coefficient of unit end resistance, usually ranging from 0.8 to 0.

95. Indicates the ultimate unit end resistance; D r is the relative density of the soil, e max and e min are the maximum and minimum void ratios of the soil, respectively; c′ is the effective cohesion of the soil; N c and N q is the bearing capacity coefficient.

3. The method for predicting the thermal-mechanical coupling response of an energy pile 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 deformation and thermal deformation of pile element i, the equilibrium equation of axial displacement is expressed as: Where ΔT i is the temperature increment of the pile in section i, α ps 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 control equation for calculating pile deformation is expressed as: ； Among them, {Δu p } represents the incremental node displacement vector, in the form of {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 thermal load vector, which is expressed as: {ΔC}={C1,C1−C2,…,C i-1 −C i ,…,C m-1 −C m ,C m } T .

4. The method for predicting the thermal-mechanical coupling response of an energy pile according to claim 1, characterized in that: The initial stiffness matrix of the pile-soil interaction model is expressed as: 。 5. The energy pile thermal-mechanical coupling response prediction device is characterized by: include: Storage; The memory stores a computer program; Actuator; The executor is used to execute the computer program stored in the memory, and when executing the computer program, the energy pile thermal-mechanical coupling response prediction method according to any one of claims 1 to 4 is implemented.

6. A computer-readable storage medium, characterized in that include: The computer-readable storage medium stores a computer program, and the computer program is executed by a processor to implement the method for predicting the thermal-mechanical coupling response of an energy pile according to any one of claims 1 to 4.

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