FDEM simulation method and system for tunnel surrounding rock thermal coupling damage

Abstract

The invention discloses an FDEM simulation method and system for tunnel surrounding rock thermal-mechanical coupling failure, and relates to the technical field of rock mechanics and rock engineering. The method comprises the following steps: acquiring thermophysical parameters of a surrounding rock sample in a target tunnel and functional relationship data of mechanical property parameters changing along with temperature; constructing a thermal stress calculation model and a heat conduction model based on the thermophysical parameters and the function relation data; embedding the thermal stress calculation model and the heat conduction model into an FDEM numerical program, and establishing an excavation numerical model of the target tunnel; thermal-mechanical coupling failure simulation is executed based on the excavation numerical model; in the simulation process, when excavation is conducted to a tunnel face, thermal stress and heat conduction calculation is started, and mechanical property parameters of all surrounding rock units in the excavation numerical model are dynamically updated according to current temperature field distribution. According to the invention, surrounding rock heat and force bidirectional coupling effect simulation can be realized, and spatio-temporal evolution characteristics of a temperature field and a stress field can be accurately reflected.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rock mechanics and rock engineering, in particular to a FDEM simulation method and system for thermal-mechanical coupling failure of tunnel surrounding rock. BACKGROUND

[0002] In recent years, underground projects such as traffic tunnels, water tunnels and mine tunnels in China are showing a trend of extending to the west and deepening; as a clean energy, the development of hot dry rock is on the rise. With the increase of the buried depth of underground projects, on the one hand, the self-weight stress and tectonic stress of rock stratum continue to increase, and on the other hand, the temperature of surrounding rock continues to rise; in fact, the ground temperature of rock stratum increases by about 3℃ for every 100m increase in buried depth, such as the ongoing Sichuan-Tibet Railway project, the stratum temperature along the line can reach as high as 97℃. Under the coupling effect of deep high geostress and high temperature environment, the surrounding rock of the tunnel shows significant nonlinear mechanical behavior. Compared with shallow projects where the temperature effect can be ignored, the temperature field has a significant and non-negligible influence on the deformation and failure process of the surrounding rock under deep high temperature conditions. Deep high stress, high temperature hard rock environment may induce new dynamic disasters such as temperature difference rock burst and other high temperature heat damage problems, which seriously threaten the safety of the project.

[0003] Although the finite element-discrete element coupling method (FDEM) can effectively simulate the disaster process of surrounding rock from continuous deformation to failure to block movement, and can capture the geometric characteristics of the fracture network, its application is still concentrated in the failure analysis under the driving of a single stress field. At present, the simulation of the disaster process of deep tunnel surrounding rock only considers the influence of the stress field, and has not realized the simulation of the thermal-mechanical coupling process.

[0004] Under the condition of deep high stress + high temperature, when the tunnel is excavated, on the one hand, it brings about the spatial transfer and temporal evolution of the stress field, and on the other hand, it brings about the change of the temperature field, and the change of the temperature field has a significant influence on the deformation parameters and strength parameters of the surrounding rock, and the temperature field has a space-time evolution process; in addition, the stress field and temperature field of the surrounding rock in different regions are different at different times, that is, the stress field and temperature field have space-time variability. Therefore, how to accurately simulate the deformation and failure disaster process of deep tunnel surrounding rock under the action of thermal-mechanical coupling, especially considering the space-time variability of the stress field and temperature field, has become a technical problem to be solved. SUMMARY

[0005] In order to solve the problems in the prior art, the present application provides a FDEM simulation method and system for thermal-mechanical coupling failure of tunnel surrounding rock, which can realize the simulation of thermal-mechanical coupling of surrounding rock and accurately reflect the space-time evolution characteristics of temperature field and stress field.

[0006] To achieve the above purpose, the present application provides a FDEM simulation method for thermal-mechanical coupling failure of tunnel surrounding rock, comprising:

[0007] acquire the thermal physical property parameters of the surrounding rock sample in the target tunnel, and function relationship data of the mechanical property parameters changing with temperature;

[0008] construct a thermal stress calculation model and a heat conduction model based on the thermal physical property parameters and the function relationship data;

[0009] embed the thermal stress calculation model and the heat conduction model into a FDEM numerical program, and establish an excavation numerical model of the target tunnel;

[0010] perform a thermal-mechanical coupling damage simulation based on the excavation numerical model; in the simulation process, when excavating to the working face, start the thermal stress and heat conduction calculation, and dynamically update the mechanical property parameters of each surrounding rock element in the excavation numerical model according to the current temperature field distribution.

[0011] Optionally, the mechanical property parameters include elastic modulus, Poisson's ratio, tensile strength and compressive strength; and the function relationship data is obtained by carrying out uniaxial compression, Brazilian splitting and triaxial compression tests on surrounding rock samples at different temperatures.

[0012] Optionally, the expression of the thermal stress calculation model is as follows:

[0013]

[0014] In the formula, Δσ xx is the normal thermal stress in the x direction, Δσ yy is the normal thermal stress in the y direction, Δσ xy is the tangential thermal stress in the x direction, Δσ yx is the tangential thermal stress in the y direction; K is the bulk modulus, E is the elastic modulus, v is the Poisson's ratio, a is the thermal expansion coefficient; and ΔT is the temperature difference between the current calculation time step and the last calculation time step.

[0015] Optionally, the transfer calculation formula of the heat flow in the heat conduction model is as follows:

[0016]

[0017] In the formula, Q j→i represents the heat flow flowing from the triangular element j into the triangular element i; A ji is the area of the quadrilateral element between the adjacent triangular element i and the triangular element j, l is the thermal conductivity, T i , T j , T ji are the temperatures of the triangular elements i, j, respectively, d j→i is the centroid distance between the triangular element i and the triangular element j, and At is the calculation time step.

[0018] Optionally, the surrounding rock units include triangular units and quadrilateral units; during the heat conduction calculation process, when a quadrilateral unit connecting two adjacent triangular units is broken and the two adjacent triangular units are not in contact, the heat exchange between the two adjacent triangular units is stopped.

[0019] Optionally, the surrounding rock units include triangular units and quadrilateral units; the mechanical property parameters of each surrounding rock unit in the excavation numerical model are dynamically updated according to the current temperature field distribution, including:

[0020] According to the current temperature field distribution, the elastic modulus and Poisson's ratio of each triangular unit and the cohesion, tensile strength, I-type fracture energy and II-type fracture energy of each quadrilateral unit in the excavation numerical model are updated.

[0021] Optionally, the calculation time step of the heat stress and heat conduction calculation is determined by coupling a longitudinal displacement curve LDP and a surrounding rock convergence characteristic curve; the surrounding rock convergence characteristic curve is obtained based on an ideal elastoplastic model under a two-dimensional plane strain state, the abscissa of the convergence characteristic curve is a core material softening rate, and the ordinate is a ratio of a tunnel surrounding rock convergence displacement to a final convergence displacement; the longitudinal displacement curve LDP is obtained by using the following formula:

[0022]

[0023] In the formula, u * represents a surrounding rock displacement, u0 is a surrounding rock displacement at a working face, u max is a maximum surrounding rock displacement away from the working face; R * represents a plastic zone radius, R0 is a tunnel radius, is a maximum plastic zone radius; X * represents a distance of a simulated section in a longitudinal direction from a working face, X is a longitudinal distance of a simulated section position from a working face; X * <0 indicates a region in front of the working face, X * >0 indicates a region behind the working face, and X*=0 indicates that the simulated section is located at the working face position.

[0024] Optionally, in the simulation process, the inner boundary temperature of the excavation numerical model is consistent with the collected ambient temperature in the target tunnel, and the outer boundary temperature is consistent with the collected surrounding rock temperature at a target position in the target tunnel.

[0025] The application also provides a FDEM simulation system for tunnel surrounding rock thermal force coupling damage, including:

[0026] The data acquisition unit is configured to acquire function relationship data of thermal physical parameters and mechanical performance parameters of a surrounding rock sample in a target tunnel changing with temperature.

[0027] The construction unit is configured to construct a thermal stress calculation model and a thermal conduction model based on the thermal physical parameters and the function relationship data.

[0028] The embedding and construction unit is configured to embed the thermal stress calculation model and the thermal conduction model into an FDEM numerical program, and establish an excavation numerical model of the target tunnel.

[0029] The simulation unit is configured to perform a thermal-mechanical coupling damage simulation based on the excavation numerical model; in the simulation process, when excavation reaches a working face, thermal stress and thermal conduction calculation are started, and mechanical performance parameters of each surrounding rock unit in the excavation numerical model are dynamically updated according to a current temperature field distribution.

[0030] According to the specific embodiments of the present application, the following technical effects are provided.

[0031] The FDEM simulation method for thermal-mechanical coupling damage of a tunnel surrounding rock provided by the present application acquires function relationship data of thermal physical parameters and mechanical performance parameters of a surrounding rock sample changing with temperature, constructs a thermal stress calculation model and a thermal conduction model, and embeds the two models into an FDEM numerical program to establish an excavation numerical model, thereby realizing bidirectional coupling simulation of a stress field and a temperature field in the FDEM framework for the first time. In the simulation process, the extension state of a surrounding rock damage zone is dynamically monitored, thermal stress and thermal conduction calculation are automatically triggered when the damage zone extends to a working face, and the mechanical performance parameters of the surrounding rock unit are updated according to a real-time temperature field distribution, so as to accurately depict the time-space evolution process of the thermal-mechanical coupling effect of the surrounding rock under a deep high-temperature environment.

[0032] The technical solution provided by the present application solves the simulation distortion problem caused by ignoring the time-space variability of the temperature field in the prior art. The thermal stress calculation model quantifies the additional stress field induced by temperature change, and the thermal conduction model dynamically tracks the evolution path of the temperature field, and the cooperative action of the two models completely reproduces the nonlinear mechanical response of the surrounding rock under the coupling action of deep high geostress and high-temperature environment. The present application breaks through the limitation of the existing FDEM technology which only considers a single stress field, and for the first time realizes the simulation of the time-space coupling of the thermal-mechanical fields in the disaster process of deep tunnel excavation, thereby providing reliable technical support for tunnel stability analysis, thermal hazard prevention and early warning in high-temperature rock layers. BRIEF DESCRIPTION OF DRAWINGS

[0033] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout the several views, and in which the exemplary embodiments of the present application are shown.

[0034] Figure 1 A method flowchart of the FDEM simulation method for the thermal coupling damage of the tunnel surrounding rock is shown in the embodiment of the present application.

[0035] Figure 2 A fitting curve diagram of the relationship between the elastic modulus and the temperature is shown in the embodiment of the present application.

[0036] Figure 3 A fitting curve diagram of the relationship between the Poisson's ratio and the temperature is shown in the embodiment of the present application.

[0037] Figure 4 A fitting curve diagram of the relationship between the tensile strength and the temperature is shown in the embodiment of the present application.

[0038] Figure 5 A fitting curve diagram of the relationship between the compressive strength and the temperature is shown in the embodiment of the present application.

[0039] Figure 6 A temperature boundary condition diagram of the excavation numerical model is shown in the embodiment of the present application.

[0040] Figure 7 A simulation result diagram of the thermal coupling damage of the tunnel surrounding rock is shown in the embodiment of the present application.

[0041] Figure 8 A calculation method diagram of the conversion of the thermal stress into the node force is shown in the embodiment of the present application.

[0042] Figure 9 A heat conduction mode diagram between the triangular elements is shown in the embodiment of the present application.

[0043] Figure 10 A coupling relationship diagram between the longitudinal displacement curve LDP and the surrounding rock convergence characteristic curve is shown in the embodiment of the present application.

[0044] Figure 11 A module structure diagram of the FDEM simulation system for the thermal coupling damage of the tunnel surrounding rock is shown in the embodiment of the present application. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0046] Reference is made to Figure 1 , Figure 1A flowchart of a method for FDEM simulation of thermal-mechanical coupled failure of surrounding rock of a tunnel.

[0047] The FDEM simulation method of thermal-mechanical coupled failure of surrounding rock of a tunnel comprises the following steps:

[0048] Step 101: Obtain the thermal physical parameters of the surrounding rock sample in the target tunnel, and the function relationship data of the mechanical performance parameters changing with temperature.

[0049] In the application, the key thermal physical characteristic parameters of the surrounding rock sample can be directly determined through laboratory tests. The thermal physical parameters mainly include the thermal expansion coefficient, the specific heat capacity and the thermal conductivity coefficient. The thermal expansion coefficient represents the volume change rate of the rock after being heated, the specific heat capacity reflects the heat required for unit mass of rock to be heated, and the thermal conductivity coefficient describes the ability of the rock to conduct heat.

[0050] The mechanical performance parameters mainly include the elastic modulus, the Poisson's ratio, the tensile strength and the compressive strength; and the function relationship data can be obtained by carrying out uniaxial compression, Brazilian splitting and triaxial compression tests on the surrounding rock samples at different temperatures. In the specific operation, a plurality of surrounding rock samples can be heated to different preset temperature points, and the temperature gradient is set to not less than 5 groups to ensure the accuracy of data fitting; and the uniaxial compression test, the Brazilian splitting test and the triaxial compression test are carried out on the samples at each temperature state, so as to measure the elastic modulus, the Poisson's ratio, the tensile strength and the compressive strength values corresponding to different temperatures.

[0051] Referring to Figures 2 to 5 , wherein Figure 2 , 3 , 4 and 5, the fitting curves of the elastic modulus and temperature, the fitting curves of the Poisson's ratio and temperature, the fitting curves of the tensile strength and temperature, and the fitting curves of the compressive strength and temperature are sequentially displayed.

[0052] Step 102: Based on the thermal physical parameters and the function relationship data, a thermal stress calculation model and a heat conduction model are constructed.

[0053] The core of the thermal stress calculation model is a physical equation for describing the internal stress of the surrounding rock induced by temperature change, which converts the temperature change into equivalent mechanical stress, and reflects the influence of temperature fluctuation on the stress state of the surrounding rock in real time; the thermal stress calculation model converts the temperature difference into an additional stress field, quantifies the internal stress change of the surrounding rock due to thermal expansion and contraction effect, and provides mechanical input for subsequent thermal-mechanical coupled analysis.

[0054] The heat conduction model focuses on simulating the spatio-temporal evolution process of the internal temperature field of the surrounding rock. The heat conduction model realizes the dynamic evolution of the non-uniform temperature field in the surrounding rock through the real-time response control of the heat flow interaction mechanism and the crack state, and accurately describes the conduction path and rate of heat in the rock mass.

[0055] Step 103: Embed the thermal stress calculation model and the heat conduction model into the FDEM numerical program, and establish the excavation numerical model of the target tunnel.

[0056] In the application, the constructed thermal stress calculation model and heat conduction model are implanted into the core calculation process of the FDEM numerical program. In the embedding process, the thermal stress calculation model directly acts on the finite element discrete system by converting the thermal stress tensor induced by the temperature difference into the equivalent node force of the triangular element; the heat conduction model is integrated into the thermodynamic module of the program, and the heat flow transmission relationship between adjacent triangular elements and the crack state judgment logic are established to drive the temperature field update. In addition, the two are bidirectionally coupled by sharing temperature data and mechanical parameters, and the thermal stress induced by temperature change can be superimposed on the mechanical stress field in real time, while the crack development state caused by mechanical damage is also dynamically fed back to the heat conduction path control, so as to ensure the synchronous evolution of the stress field and the temperature field.

[0057] On this basis, a corresponding three-dimensional excavation numerical model can be established by FDEM according to the actual geological profile and engineering size of the target tunnel; the surrounding rock elements in the excavation numerical model are grid elements, including triangular elements and quadrilateral elements, wherein the triangular elements represent continuous rock mass, and the quadrilateral elements connecting the triangular elements represent potential broken interfaces.

[0058] In addition, when calibrating the II-type fracture energy corresponding to different cohesive forces and the I-type fracture energy corresponding to different tensile strengths in the calibrated excavation numerical model, the calibration method can refer to the standard process described in the invention patent “A fracture energy precise calibration method for eliminating loading rate effect” (Patent No. ZL202211201119.6). The joint penalty value, the normal contact stiffness and the tangential contact stiffness can be valued by the following formulas:

[0059]

[0060] In the formula, P f is the joint penalty value, E0 is the initial elastic modulus under the un-cooled state before the tunnel excavation, P n is the normal contact stiffness, P t is the tangential contact stiffness.

[0061] Step 104: Perform thermal-mechanical coupling damage simulation based on the excavation numerical model. In the simulation process, when the excavation reaches the working face, the thermal stress and heat conduction calculation are started, and the mechanical performance parameters of each surrounding rock element in the excavation numerical model are dynamically updated according to the current temperature field distribution.

[0062] In the application, in the process of simulating the thermal-mechanical coupling damage by using the excavation numerical model, only mechanical calculation is performed in the initial stage to simulate the stress adjustment process of the surrounding rock. When it is monitored that the damage zone of the surrounding rock extends to the position of the working face (i.e., the core material is softened to the excavation front), the opening instruction of the thermal stress and heat conduction calculation module is automatically triggered, and the triggering time can be accurately determined by the coupling analysis of the longitudinal displacement curve and the convergence characteristic curve of the surrounding rock.

[0063] After the thermal-mechanical coupling is opened, the heat conduction model calculates the heat flow exchange between adjacent triangular elements in real time, and dynamically adjusts the heat conduction path according to the fracture state of the quadrilateral element. At the same time, the thermal stress model converts the temperature difference into an equivalent node force and adds it to the stress field to form the additional load caused by the thermal expansion effect.

[0064] In the process of heat conduction calculation, when the quadrilateral element connecting two adjacent triangular elements is broken and the two adjacent triangular elements are not in contact, the heat exchange between the two adjacent triangular elements is stopped. Specifically, when the quadrilateral element connecting the adjacent triangular elements is intact, the heat exchange is normal; if the quadrilateral element is broken but the two sides of the triangular element are still in contact, limited heat conduction is allowed; if the quadrilateral element is completely separated after breaking, that is, the heat conduction path between the two sides of the triangular element is completely broken, the heat exchange between the two triangular elements is immediately interrupted. This design can truly reflect the blocking effect of the fracture on the heat conduction path.

[0065] In the simulation process, the temperature change of each surrounding rock element is tracked in real time, and the mechanical property parameters of each surrounding rock element are dynamically refreshed according to the real-time updated temperature field distribution. Specifically, according to the current temperature field distribution, the elastic modulus and Poisson's ratio of each triangular element in the excavation numerical model are updated, as well as the cohesion, tensile strength, I-type fracture energy and II-type fracture energy of each quadrilateral element. Among them, the temperature of each quadrilateral element is set as the average value of the temperatures of the two adjacent triangular elements.

[0066] Please attend Figure 6 , Figure 6 The temperature boundary condition diagram of the excavation numerical model.

[0067] In the whole simulation process, the inner boundary temperature of the excavation numerical model is consistent with the environment temperature collected in the target tunnel, and the outer boundary temperature is consistent with the temperature of the surrounding rock collected at the target position in the target tunnel. Specifically, the inner boundary (i.e., the tunnel excavation contour surface) of the excavation numerical model is set as a free displacement surface, and the temperature is consistent with the environment temperature monitored in the target tunnel. The exposed surrounding rock around the tunnel is simultaneously instantaneously cooled to the environment temperature, and the outer boundary (the outer boundary of the model calculation domain) is fixed in displacement, and the temperature is anchored to the initial temperature of the surrounding rock collected in the undisturbed area deep in the target tunnel and remains constant, forming a continuous heat exchange driving condition.

[0068] When the simulation continues until the stress field, displacement field and temperature field of the surrounding rock reach a stable state (the rate of change of the key physical quantity is lower than the preset threshold), it indicates that the simulation of the thermal-mechanical coupling disaster process is completed; the simulation results are shown in Figure 7 The present application can completely reproduce the whole process of thermal-mechanical coupling progressive failure of the surrounding rock of a tunnel under a deep high-temperature environment, and provides data support for engineering thermal hazard prevention and control.

[0069] Next, the thermal stress and heat conduction calculation are further described in detail.

[0070] In application, the mechanical parameter relationship of the thermal expansion coefficient and the elastic modulus, Poisson's ratio and the like changing with temperature can be used to establish a thermal stress calculation model. The expression of the thermal stress calculation model is:

[0071]

[0072] In the formula, Δσ xx is the normal thermal stress in the x direction, Δσ yy is the normal thermal stress in the y direction, Δσ xy is the tangential thermal stress in the x direction, Δσ yx is the tangential thermal stress in the y direction; K is the bulk modulus, E is the elastic modulus, v is Poisson's ratio, a is the thermal expansion coefficient; and ΔT is the temperature difference between the current calculation time step and the last calculation time step. In calculation, the triangular element is taken as a basic unit, and it is assumed that the temperature field inside the triangular element is uniformly distributed.

[0073] In the formula, ΔT is the temperature difference:

[0074]

[0075] In the formula, Q total is the total heat flow of the triangular element, including inflow and outflow, and the inflow is positive and the outflow is negative; C p is the specific heat capacity, and M is the mass of the triangular element. It can be understood that only the adjacent triangular elements of a triangular element have heat conduction.

[0076] Referring to Figure 8 , Figure 8 , it is a schematic diagram of the calculation mode of the conversion of the thermal stress into the node force; after the thermal stress is calculated, it can be converted into the node force of the corresponding triangular element by using the following formula:

[0077]

[0078] In the formula, f xi0 , f yi0 , Δσ xx , Δσyy thermal expansion stress in x, y direction, respectively, x i1 , y i1 x, y coordinate value of node i1, respectively, x i2 , y i2 x, y coordinate value of node i2, respectively, nodes i0, i1 and i2 are three nodes of triangle element i arranged counterclockwise.

[0079] Referring to Figure 9 , Figure 9 Fig. 3 is a schematic diagram of heat conduction mode between triangle elements; the heat conduction process can be calculated as follows:

[0080] Suppose that three triangle elements adjacent to triangle element i are marked as j, m and n, respectively, then the total heat flow Q total of triangle element i is:

[0081] Q total = Q m→i + Q j→i + Q n→i ;

[0082] In the formula, Q m→i , Q j→i , Q n→i represent the heat flow relationship between triangle element j, triangle element m, triangle element n and triangle element i, respectively, when taking positive value, it represents inflow, when taking negative value, it represents outflow; for example, when Q m→i is positive, it represents that the heat of triangle element m flows into triangle element i, and vice versa. Heat is transmitted from triangle element with high temperature to triangle element with low temperature; taking Q j→i as an example, its value is:

[0083]

[0084] In the formula, Q j→i represents the heat flow from triangle element j to triangle element i; A ji is the area of quadrilateral element between adjacent triangle element i and triangle element j, λ is the thermal conductivity, T i , T j represent the temperature of triangle element i and j, respectively, d ji is the distance between the centroid of triangle element i and triangle element j, and Δt is the calculation time step.

[0085] The temperature of the triangle element is updated at the next calculation time step by using the following formula:

[0086] T Δt+1 = T Δt + ΔT.

[0087] where T Δt+1 represents the temperature of the current time step, T Δt represents the temperature of the previous time step, and ΔT represents the temperature difference between adjacent time steps.

[0088] See Figure 10 , Figure 10 is a schematic diagram of the coupling relationship between the longitudinal displacement profile LDP and the surrounding rock convergence characteristic curve.

[0089] In applications, the calculation time step for thermal stress and heat conduction calculation can be determined by coupling the longitudinal displacement profile (LDP) and the surrounding rock convergence characteristic curve. The surrounding rock convergence characteristic curve is obtained based on an ideal elastoplastic model under a two-dimensional plane strain state. The abscissa of the convergence characteristic curve is the softening rate of the core material, where the core material refers to the rock mass material occupying the tunnel space and needing to be removed and excavated during tunneling. The ordinate is the ratio of the convergence displacement of the surrounding rock of the tunnel to the final convergence displacement. The longitudinal displacement profile LDP is obtained using the following formula:

[0090]

[0091] where u * represents the displacement of the surrounding rock, u0 is the displacement of the surrounding rock at the working face, and u max is the maximum displacement of the surrounding rock away from the working face; R * represents the radius of the plastic zone, R0 is the radius of the tunnel, is the maximum radius of the plastic zone; X * represents the distance of the simulated section in the longitudinal direction from the working face, X is the longitudinal distance between the simulated section position and the working face; X * <0 indicates the region in front of the working face, X * >0 indicates the region behind the working face, and X*=0 indicates that the simulated section is located at the working face position.

[0092] Corresponding to the foregoing application function implementation method embodiments, the present application also provides an FDEM simulation system for thermal-mechanical coupling failure of tunnel surrounding rock and corresponding embodiments.

[0093] See Figure 11 , Figure 11 is a schematic diagram of the module structure of the FDEM simulation system for thermal-mechanical coupling failure of tunnel surrounding rock. The FDEM simulation system for thermal-mechanical coupling failure of tunnel surrounding rock comprises:

[0094] The data acquisition unit 11 is configured to acquire function relationship data of thermal physical parameters and mechanical property parameters of a surrounding rock sample in a target tunnel varying with temperature.

[0095] The construction unit 12 is configured to construct a thermal stress calculation model and a heat conduction model based on the thermal physical parameters and the function relationship data.

[0096] The embedding and construction unit 13 is configured to embed the thermal stress calculation model and the heat conduction model into a FDEM numerical program, and establish an excavation numerical model of the target tunnel.

[0097] The simulation unit 14 is configured to perform a thermal-mechanical coupling damage simulation based on the excavation numerical model; during the simulation, when excavating to a working face, the thermal stress and heat conduction calculation are started, and the mechanical property parameters of each surrounding rock unit in the excavation numerical model are dynamically updated according to a current temperature field distribution.

[0098] In one embodiment, the surrounding rock unit includes a triangular unit and a quadrilateral unit; during the heat conduction calculation, the simulation unit 14 is further configured to:

[0099] When a quadrilateral unit connecting two adjacent triangular units is broken, and the two adjacent triangular units are not in contact, the heat exchange between the two adjacent triangular units is stopped.

[0100] In one embodiment, the surrounding rock unit includes a triangular unit and a quadrilateral unit; in terms of dynamically updating the mechanical property parameters of each surrounding rock unit in the excavation numerical model according to the current temperature field distribution, the simulation unit 14 is specifically configured to:

[0101] According to the current temperature field distribution, the elastic modulus and Poisson's ratio of each triangular unit in the excavation numerical model are updated, and the cohesion, tensile strength, I-type fracture energy and II-type fracture energy of each quadrilateral unit are updated.

[0102] As to the system in the above embodiment, the specific manner in which each unit module performs operations has been described in detail in the embodiments of the method, and can be specifically referred to the foregoing, which will not be described in detail here.

[0103] The embodiments of the present application have been described above with the best mode, and the description is exemplary rather than exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical application, or improvement to the technology in the market, or to enable other ordinary skilled persons in the art to understand the embodiments disclosed herein.

Claims

1. A FDEM simulation method for thermal-mechanical coupling failure of tunnel surrounding rock, characterized by: include: Obtain the thermophysical parameters of the surrounding rock samples in the target tunnel, as well as the functional relationship data of the mechanical properties parameters with temperature; Based on the thermophysical property parameters and functional relationship data, a thermal stress calculation model and a heat conduction model are constructed; Embedding the thermal stress calculation model and the heat conduction model into the FDEM numerical program, and establishing a numerical model of the excavation of the target tunnel; A thermal-mechanical coupling failure simulation is performed based on the excavation numerical model. During the simulation, when excavation reaches the tunnel face, thermal stress and heat conduction calculations are started, and the mechanical property parameters of each surrounding rock unit in the excavation numerical model are dynamically updated according to the current temperature field distribution.

2. The FDEM simulation method for thermal-mechanical coupling failure of tunnel surrounding rock according to claim 1 is characterized in that: The mechanical performance parameters include elastic modulus, Poisson's ratio, tensile strength and compressive strength; the functional relationship data are obtained by conducting uniaxial compression, Brazilian splitting and triaxial compression tests on surrounding rock samples at different temperatures.

3. The FDEM simulation method for thermal-mechanical coupling failure of tunnel surrounding rock according to claim 1 is characterized in that: The expression of the thermal stress calculation model is: Where Δσ xx is the normal thermal stress in the x-direction, Δσ yy is the normal thermal stress in the y direction, Δσ xy is the tangential thermal stress in the x direction, Δσ yx is the tangential thermal stress in the y direction; K is the bulk modulus, E is the elastic modulus, ν is the Poisson's ratio, α is the thermal expansion coefficient; ΔT is the temperature difference between the current calculation time step and the previous calculation time step.

4. The FDEM simulation method for thermal-mechanical coupling failure of tunnel surrounding rock according to claim 1 is characterized in that: The heat transfer calculation formula in the heat conduction model is: Where Q j→i A represents the heat flow from triangle unit j to triangle unit i; ji is the area of ​​the quadrilateral unit between the adjacent triangular unit i and triangular unit j, λ is the thermal conductivity, T i 、T j represents the temperature of triangular unit i and j, d ji is the centroid distance between triangle element i and triangle element j, and Δt is the calculation time step.

5. The FDEM simulation method for thermal-mechanical coupling failure of tunnel surrounding rock according to claim 1 is characterized in that: The surrounding rock units include triangular units and quadrilateral units; during the heat conduction calculation process, when the quadrilateral unit connecting two adjacent triangular units is broken and the two adjacent triangular units are not in contact with each other, the heat exchange between the two adjacent triangular units is stopped.

6. The FDEM simulation method for thermal-mechanical coupling failure of tunnel surrounding rock according to claim 1 is characterized in that: The surrounding rock units include triangular units and quadrilateral units. The mechanical property parameters of each surrounding rock unit in the excavation numerical model are dynamically updated according to the current temperature field distribution, including: According to the current temperature field distribution, the elastic modulus and Poisson's ratio of each triangular unit, and the cohesion, tensile strength, mode I fracture energy and mode II fracture energy of each quadrilateral unit in the excavation numerical model are updated.

7. The FDEM simulation method for thermal-mechanical coupling failure of tunnel surrounding rock according to claim 1 is characterized in that: The calculation time step of the thermal stress and heat conduction calculation is determined by coupling the longitudinal displacement curve LDP with the surrounding rock convergence characteristic curve; the surrounding rock convergence characteristic curve is obtained based on the ideal elastic-plastic model under the two-dimensional plane strain state, the abscissa of the convergence characteristic curve is the core material softening rate, and the ordinate is the ratio of the tunnel surrounding rock convergence displacement to the final convergence displacement; the longitudinal displacement curve LDP is obtained using the following formula: Where u * represents the displacement of the surrounding rock, u0 is the displacement of the surrounding rock at the tunnel face, u max is the maximum displacement of the surrounding rock far away from the tunnel face; R * represents the radius of the plastic zone, R0 is the tunnel radius, is the maximum plastic zone radius; X * Indicates the distance between the simulated section and the tunnel face in the longitudinal direction, X is the longitudinal distance between the simulated section and the tunnel face; X * <0 indicates the area in front of the face, X * >0 indicates the area behind the tunnel face, and X*=0 indicates that the simulated section is at the tunnel face position.

8. The FDEM simulation method for thermal-mechanical coupled failure of tunnel surrounding rock according to claim 1, characterized in that: During the simulation process, the inner boundary temperature of the excavation numerical model is consistent with the collected ambient temperature in the target tunnel, and the outer boundary temperature is consistent with the collected surrounding rock temperature at the target position in the target tunnel.

9. A FDEM simulation system for thermal-mechanical coupling failure of tunnel surrounding rock, characterized by: include: A data acquisition unit is used to obtain the thermophysical parameters of the surrounding rock samples in the target tunnel, as well as the functional relationship data of the mechanical properties parameters changing with temperature; A construction unit, configured to construct a thermal stress calculation model and a heat conduction model based on the thermophysical property parameters and the functional relationship data; An embedding and construction unit, configured to embed the thermal stress calculation model and the heat conduction model into the FDEM numerical program and establish an excavation numerical model of the target tunnel; A simulation unit is used to perform thermal-mechanical coupling failure simulation based on the excavation numerical model. During the simulation, when excavation reaches the tunnel face, thermal stress and heat conduction calculations are started, and the mechanical performance parameters of each surrounding rock unit in the excavation numerical model are dynamically updated according to the current temperature field distribution.

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