Energy and environmental rock-soil multiphase flow multi-field coupling finite element automatic modeling method

Abstract

The invention discloses an energy and environmental rock-soil multiphase flow multi-field coupling finite element automatic modeling method. The method comprises the steps that a universal control equation for describing multiphase substance mass conservation, momentum conservation and energy conservation in energy and environmental engineering is deduced based on porous medium mechanics and unsaturated rock-soil mechanics; constructing a weak general format of an energy and environmental geotechnical engineering multiphase multi-field coupling control equation based on a Galerkin method and a Petroleum-Galerkin method; constructing a stiffness matrix of a control equation after multiphase multi-field coupling discretization of the energy and environmental geotechnical engineering; generating an input file of a finite element program automatic generation system FEPG; according to the method, numerical modeling is carried out on energy and environmental rock and soil problems through a unified method.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy and environmental geotechnical engineering, and particularly relates to an energy and environmental geotechnological multi-phase flow multi-field coupling finite element automatic modeling method. BACKGROUND

[0002] The multi-phase multi-field coupling problem in the field of energy and environmental geotechnical engineering has always been the focus of attention of the engineering and academic circles. With the acceleration of industrialization and the growing demand for resources and energy, the stability and safety of energy and environmental geotechnical bodies under the action of multiple physical fields have become particularly important. Energy and environmental geotechnical engineering involves complex multi-phase multi-field coupling problems, including the interaction of multiple physical fields such as temperature field, concentration field, stress field, and pressure field. In recent years, with the increasing prominence of energy and environmental problems, the research on energy and environmental geotechnological multi-phase multi-field coupling model has attracted widespread attention. The energy and environmental geotechnological multi-phase multi-field coupling model not only involves the mechanical behavior of soil, but also includes solute transport, heat transfer, chemical reaction, multi-phase seepage, stress deformation and other processes, which interact with each other to form complex coupling effects. This multi-component multi-phase multi-field coupling effect makes the problems in energy and environmental geotechnical engineering more complex, and requires more sophisticated models to describe and predict.

[0003] Significant progress has been made in the research of multi-phase and multi-field coupling model of energy and environmental geotechnical by domestic and foreign scholars, but most of them are aimed at deep geotechnical or non-soil porous medium materials. The research on multi-phase and multi-field coupling modeling of unsaturated soil is mainly based on the following three assumptions, including: ① High saturation compressible fluid assumption; ② Gas pressure can be ignored assumption; ③ Viscous-captivity-density complex multi-phase flow assumption. The first assumption is suitable for unsaturated soil with high water content and low suction, which considers that the gas phase is dissolved in the liquid phase or exists in the form of micro-bubbles in the liquid phase, ignores the capillary effect and the gas-liquid fluid compression is related to pressure and temperature. The second assumption is suitable for the case of containing isolated gas bubbles or the density, pressure and energy change of gas can be ignored. The assumption considers the capillary effect, and the Darcy law, continuity equation and SWCC are used to derive the water head type or saturation type Richard equation to describe the seepage. The third assumption is suitable for most actual working conditions compared with the first two assumptions. The assumption can consider the change of gas pressure, density and energy and the interaction between gas-liquid-solid three phases. At present, there are many software that can simulate the thermal-flow-force coupling response of rock-soil containing complex multi-phase flow, and table 1 lists the widely used rock-soil thermal-flow-force coupling analysis software, which is mainly divided into two types of software for deep rock mechanics analysis and soil mechanics analysis. For the software for deep rock mechanics, the current software mainly uses a semi-coupled way to realize the description of the mechanical behavior based on the thermal stress and effective stress principle, and less involves the nonlinear influence of capillary effect and material component change on the mechanical properties of rock-soil. At present, the simulation software for soil mechanics more involves the influence of water migration and capillary effect on the mechanical behavior of rock-soil, and the description of the exchange and migration of different component materials is often simplified or ignored in modeling, and more focus is on the coupling of gas-liquid two-phase seepage after mixing and the stress deformation of soil skeleton. At present, there is no unified modeling method that considers both the factors of pore multi-component and multi-phase system and the influence of thermal-flow-force-chemical full coupling.

[0004] Table 1 widely used energy and environmental geotechnical multi-phase and multi-field coupling analysis software

[0005]

[0006] In view of the above background, the present application provides a unified modeling method of energy and environmental multi-phase flow multi-field full coupling geotechnical physical mechanics model, so as to realize the complex multi-phase and multi-field coupling problem faced in the analysis of environmental geotechnical engineering problems. SUMMARY

[0007] In order to solve the problems in the prior art, the purpose of the present application is to provide an energy and environmental geotechnical multi-phase flow multi-field coupling finite element automatic modeling method, and the present application carries out numerical modeling on energy and environmental geotechnological problems by a unified method.

[0008] To achieve the above object, the technical scheme adopted by the present application is: an energy and environment geotechnical multiphase flow multi-field coupling finite element automatic modeling method, comprising the following steps:

[0009] Step 1, based on porous medium mechanics and unsaturated geotechnical mechanics, deriving general control equations for describing mass conservation, momentum conservation and energy conservation of multiphase substances in energy and environmental engineering;

[0010] Step 2, based on the Galerkin method and Petrov-Galerkin method, constructing a weak form general format of the multiphase multi-field coupling control equation of energy and environmental geotechnical engineering;

[0011] Step 3, constructing the stiffness matrix of the discrete control equation of the multiphase multi-field coupling of energy and environmental geotechnical engineering;

[0012] Step 4, generating the input file of the finite element program automatic generation system FEPG.

[0013] As a further improvement of the present application, in step 1, according to the porous medium mechanics, the porosity is defined as , wherein, is the volume of the pores in the medium, V is the total volume of the medium; the volume ratio of the i-th phase substance in the entire medium in the porous medium is defined as , wherein, is the volume of the i-th phase substance; the saturation of the i-th phase substance in the pores is defined as ; the general control equation specifically includes:

[0014] ① Porous multiphase flow Darcy seepage equation:

[0015] Selecting the m-th phase substance among the n-phase substances, the saturation of the m-th phase is:

[0016]

[0017] The calculation formula of the pressure of the i-th phase is established:

[0018]

[0019] , wherein, , is the m-th phase, is the capillary force function;

[0020]

[0021] , wherein, is the derivative of the capillary force function with respect to the saturation of the j-th phase substance;

[0022] The Darcy's equation of porous media multiphase flow is given by the continuity equation and Darcy's law of each phase in the pore:

[0023]

[0024] where, is the density of the i-th phase, k is the intrinsic permeability, is the relative permeability, is the dynamic viscosity of the fluid, is the gravitational acceleration, is the mass source;

[0025] Summing i from 1 to n, the equation is:

[0026]

[0027] ② Mass transfer equation with molar concentration as independent variable:

[0028] Define the molar concentration of the a-th solute in the i-th phase as , and establish the mass transport equation of the substance:

[0029]

[0030] where, is the chemical reaction source and sink of the a-th solute in the i-th phase, is the concentration diffusion coefficient of the a-th solute in the i-th phase, is the Darcy's velocity of the i-th phase;

[0031] ③ Mass transfer equation with mass fraction as independent variable:

[0032] Define the mass fraction of the substance a in the i-th phase as , and establish the mass transport equation of the substance:

[0033]

[0034] where, is the mass diffusion coefficient of the a-th solute in the i-th phase;

[0035] ④ System heat transfer equation:

[0036] Define the temperature of the system as T, and establish the total heat balance equation of the system:

[0037]

[0038] where, is the heat source and sink of the i-th phase, is the thermal conductivity of the system, is the specific heat capacity of the system, Ci is the specific heat capacity of the ith phase;

[0039] ⑤ Force balance equation:

[0040] Definition of effective stress , the force balance equation is:

[0041]

[0042] where, is the pore pressure, is the Biot coefficient, is the Kronecker operator;

[0043] According to the generalized Hooke's law:

[0044]

[0045] where B is the strain-displacement transformation matrix, and D is the stiffness matrix.

[0046] As a further improvement of the present application, in step 2, the weak form of equations (4)-(9) is established by the Galerkin method, obtaining:

[0047] ① General format of the weak form of the Darcy's flow equation of multiphase flow in porous media:

[0048] Weak form: expressed by the solving variables of the field and the derivative with respect to time, where may contain variables of the field or coupled fields, may contain variables of the coupled fields, and the results of the previous time step or iteration step are substituted:

[0049]

[0050]

[0051] The weak form is finally arranged as:

[0052]

[0053] Weak form: expressed by the solving variables of the field and , the derivative with respect to time:

[0054]

[0055]

[0056]

[0057] The weak form is finally arranged as:

[0058]

[0059] The weak form general format of mass transfer equation with mole concentration as independent variable:

[0060] Expressed by the solving variables in this field The derivative with respect to time:

[0061]

[0062] The weak form is finally arranged as:

[0063]

[0064] The weak form general format of mass transfer equation with mass fraction as independent variable:

[0065]

[0066] The weak form general format of system heat transfer equation:

[0067]

[0068] The weak form general format of force balance equation:

[0069]

[0070] .

[0071] As a further improvement of the present application, in step 3, the stiffness matrix is given by arranging the weak form equation:

[0072] ① Porous multiphase flow Darcy seepage equation:

[0073] :

[0074]

[0075]

[0076]

[0077]

[0078]

[0079]

[0080]

[0081]

[0082]

[0083]

[0084]

[0085]

[0086] :

[0087]

[0088]

[0089]

[0090]

[0091]

[0092]

[0093]

[0094]

[0095]

[0096]

[0097]

[0098]

[0099]

[0100]

[0101]

[0102]

[0103]

[0104] ② Mass transfer equation with molar concentration as independent variable:

[0105]

[0106]

[0107]

[0108]

[0109]

[0110]

[0111]

[0112]

[0113] ③ Mass transfer equation with mass fraction as independent variable:

[0114]

[0115]

[0116]

[0117]

[0118]

[0119]

[0120] ④ System heat transfer equation:

[0121]

[0122]

[0123]

[0124]

[0125]

[0126]

[0127] ⑤ Force balance equation:

[0128]

[0129]

[0130]

[0131]

[0132] .

[0133] As a further improvement of the application, the step 4 specifically comprises:

[0134] (1) input and store project related information, including user-defined parameters, user-defined functions, physical fields, solution schemes;

[0135] (2) for each user-defined parameter, hash its name, and the names of other parameters and solution variables contained in its expression, and record the relevant information;

[0136] (3) for each user-defined parameter, count its order and whether its expression is associated with node information;

[0137] (4) process each physical field;

[0138] (5) write out files according to the recorded information.

[0139] As a further improvement of the application, in (4), for each physical field, the following processing is performed:

[0140] a) hash the expression of the parameters in the field control equation, and record all user-defined parameters, solution variables and corresponding physical fields involved in the expression in the field class object;

[0141] b) hash the expression of the parameters in the Neumann boundary condition of the field, and record all user-defined parameters, solution variables and corresponding coupled physical fields involved in the expression in the boundary condition class object;

[0142] c) calculate the derivative of some parameters in the field control equation;

[0143] d) record the user-defined parameters and coupled physical fields involved in the calculation of the derived field of the field;

[0144] e) hash the expression of the initial condition of the field, and record all user-defined parameters, solution variables and corresponding coupled physical fields involved in the expression in the condition class object;

[0145] f) hash the expression of the Dirichlet boundary condition of the field, and record all user-defined parameters, solution variables and corresponding coupled physical fields involved in the expression in the boundary condition class object.

[0146] As a further improvement of the application, in (5), according to the recorded information, the following types of files are written out:

[0147] a) FEPG input script, including:.mdi,..gcn,.pos,.pde,.fbc files;

[0148] b) a record file for modifying the generated C language file, and a supplementary C language file;

[0149] c) a file recording the geometric entities of initial and boundary conditions for generating a grid data file;

[0150] d) a project batch file.bat for generating a control calculation flow.

[0151] The present application proposes a unified modeling method of a geotechnical physical and mechanical model considering the full coupling of energy and environment multiphase flow and multiple fields; the present application is based on the basic theories of porous medium mechanics and unsaturated soil mechanics, and considers the mutual influence between different phase materials. Starting from the mass conservation, momentum conservation and energy conservation, combined with related auxiliary equations, the main partial differential control equations are derived to describe the mass transport, mechanical and heat behavior changes of different component materials in energy and environment geotechnical engineering. Based on the Galerkin method, the above partial differential equations are constructed in weak form, and the finite element method, separation iteration method, Petrov-Galerkin method, backward Euler integration method and generalized minimum residual method are used to realize the unified modeling of the multi-phase and multi-field coupling behavior in energy and environment geotechnical engineering.

[0152] The present application has the following beneficial effects:

[0153] The model of the present application is based on the basic theories of porous medium mechanics and unsaturated soil mechanics, adopts a general form of partial differential equation, and establishes the coupling relationship between the concentration of material components, the pressure of multiphase materials in pores, the temperature of mixed phase, and the stress-strain of soil skeleton. Based on the modularization idea, different types of control equations are constructed and discretized. In the equations, the diffusion and convection migration of multi-component materials, the material conversion between different components, the conversion between different phases, the diffusion and convection migration of heat in the mixed phase system, the heat generated and absorbed by material conversion, and the changes of stress field and strain field of soil skeleton accompanying the whole energy and mass transport process are considered. At the same time, the Petrov-Galerkin method is used to adjust the energy and mass transfer under strong convection condition, the backward Euler integration and BDF form are used to realize the stability of time integration, the construction idea of the whole model is clear, the algorithm development is convenient, the program is easy to write, and the scalability is good. BRIEF DESCRIPTION OF DRAWINGS

[0154] Figure 1 The flowchart of the input method for converting the mathematical physics model in the embodiment of the present application into FEPG program is shown;

[0155] Figure 2 The format diagram of multi-field iteration solution in the embodiment of the present application is shown;

[0156] Figure 3 The grid and size diagram used for model verification in the embodiment of the present application is shown;

[0157] Figure 4 This is a comparison chart of pore gas pressure simulation results in embodiments of the present invention;

[0158] Figure 5 This is a graph showing the concentration simulation results in an embodiment of the present invention;

[0159] Figure 6 This is a diagram showing the temperature simulation results in an embodiment of the present invention;

[0160] Figure 7 This is a schematic diagram of the Biot consolidation problem in an embodiment of the present invention;

[0161] Figure 8 This is a schematic diagram of the evolution of the sphere core pressure in an embodiment of the present invention;

[0162] Figure 9 This is a schematic diagram of radial strain distribution and pore pressure dissipation process in an embodiment of the present invention. Detailed Implementation

[0163] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0164] Example

[0165] like Figures 1-9 As shown, an automated finite element modeling method for multiphase flow coupled with multiple fields in energy and environmental soil and rock includes:

[0166] Suppose that a certain energy and environmental geotechnical engineering problem involves n phases of matter. Here, a phase refers to a substance that can be clearly distinguished from other substances by its volume percentage and has different physical and mechanical properties. For example, non-aqueous fluids can be distinguished from other liquids by their volume percentage and can therefore be considered as independent phases.

[0167] According to pore media mechanics, porosity is defined as... ,in, Let V be the volume of the pores in the medium, and V be the total volume of the medium. The volume percentage of the i-th phase in the porous medium is defined as... ,in, This is the volume of phase i. The saturation of phase i in the pores is defined as... It is worth noting that when calculating the saturation of the i-th phase material, i cannot be the medium skeleton material. In environmental geotechnical engineering, the skeleton medium is solid soil.

[0168] (1) Based on porous media mechanics and unsaturated soil mechanics, the general governing equations for mass conservation, momentum conservation and energy conservation of multiphase materials in energy and environmental engineering are derived and described:

[0169] ① Darcy's equation for multiphase flow in pores:

[0170] The mth phase material in the selected n phase materials, the m phase saturation is:

[0171]

[0172] The calculation formula of the i th phase pressure :

[0173]

[0174] Wherein, , The mth phase, The capillary force function:

[0175]

[0176] Wherein, The derivative of the capillary force function to the jth phase material saturation.

[0177] The Darcy seepage equation of multiphase flow in porous media is given by the continuity equation of each phase material in the pore and Darcy law:

[0178]

[0179] In the formula, The density of the ith phase material, k is the intrinsic permeability, The relative permeability, The fluid dynamic viscosity, The gravitational acceleration, The mass source.

[0180] Summing i from 1 to n gives the equation:

[0181]

[0182] ② The mass transfer equation with molar concentration as the independent variable:

[0183] Define the molar concentration of the a th solute in the ith phase as , and establish the mass transport equation:

[0184]

[0185] Wherein, The chemical reaction source and sink of the a th solute in the ith phase. The concentration diffusion coefficient of the a th solute in the ith phase, The Darcy flow rate of the ith phase.

[0186] ③ The mass transfer equation with mass fraction as the independent variable:

[0187] Definition of the mass fraction of substance α in the i-th phase The mass transport equation of substance is established:

[0188]

[0189] Wherein, is the mass diffusion coefficient of the α-th solute in the i-th phase.

[0190] ④ System heat transfer equation:

[0191] The temperature of the system is defined as T, and the total heat balance equation of the system is established:

[0192]

[0193] Wherein, is the heat source and sink of the i-th phase, is the thermal conductivity of the system, is the specific heat capacity of the system, is the specific heat capacity of the i-th phase.

[0194] ⑤ Force balance equation:

[0195] The effective stress is defined as The force balance equation is established as:

[0196]

[0197] Wherein, is the pore pressure, is the Biot coefficient, is the Kronecker operator.

[0198] According to the generalized Hooke's law,

[0199]

[0200] The B matrix is the conversion matrix of strain and displacement, and D is the stiffness matrix.

[0201] (2) Based on the Galerkin method and Petrov-Galerkin method, the weak form general format of the multi-phase and multi-field coupling control equation of energy and environmental geotechnical engineering is constructed:

[0202] The weak form of equations (4)-(9) is established by the Galerkin method, which can be obtained:

[0203] ① The weak form general format of the Darcy seepage equation of porous media multi-phase flow:

[0204] Weak form:

[0205] Expressed by the solving variables of the physical field and The derivative with respect to time, where Possibly containing the variable of the field or the coupling field, Possibly containing the variable of the coupling field, all are substituted by the results of the last time step or iteration step,

[0206]

[0207]

[0208] The weak form is finally arranged as:

[0209]

[0210] Weak form:

[0211] Expressed by the solving variable of the field And , The derivative with respect to time:

[0212]

[0213]

[0214]

[0215] The weak form is finally arranged as:

[0216]

[0217] ②The weak form general format of the mass transfer equation with molar concentration as the independent variable:

[0218] Expressed by the solving variable of the field The derivative with respect to time,

[0219]

[0220] The weak form is finally arranged as:

[0221]

[0222] ③The weak form general format of the mass transfer equation with mass fraction as the independent variable:

[0223]

[0224] ④The weak form general format of the system heat transfer equation:

[0225]

[0226] ⑤The weak form general format of the force balance equation:

[0227]

[0228]

[0229] (3) The stiffness matrix of the discrete post-control equation of the multi-phase and multi-field coupling of energy and environmental geotechnical engineering is constructed:

[0230] The stiffness matrix is given by arranging the weak form equation:

[0231] ① The Darcy seepage equation of pore multi-phase flow:

[0232] :

[0233]

[0234]

[0235]

[0236]

[0237]

[0238]

[0239]

[0240]

[0241]

[0242]

[0243]

[0244]

[0245] :

[0246]

[0247]

[0248]

[0249]

[0250]

[0251]

[0252]

[0253]

[0254]

[0255]

[0256]

[0257]

[0258]

[0259]

[0260]

[0261]

[0262]

[0263] Equation of mass transfer with mole concentration as independent variable:

[0264]

[0265]

[0266]

[0267]

[0268]

[0269]

[0270]

[0271]

[0272] Equation of mass transfer with mass fraction as independent variable:

[0273]

[0274]

[0275]

[0276]

[0277]

[0278]

[0279] (4) System heat transfer equation:

[0280]

[0281]

[0282]

[0283]

[0284]

[0285]

[0286] (5) Force balance equation:

[0287]

[0288]

[0289]

[0290]

[0291]

[0292] (4) Generate FEPG-based finite element program input file:

[0293] This method needs to use FEPG computer intelligent programming to generate a discrete model into a finite element program. The specific implementation method is as follows:

[0294] 1. Input and store project-related information, mainly including custom parameters, custom functions, physical fields, and solution schemes.

[0295] 2. For each custom parameter, hash its name and the names of other parameters and solution variables contained in its expression, and record the relevant information.

[0296] 3. For each custom parameter, count its order and whether its expression is associated with node information.

[0297] 4. For each physical field, the following processing is performed:

[0298] a) Hash the expression of the parameters in the field control equation, and record all custom parameters, solution variables and corresponding physical fields involved in the field class object.

[0299] b) Hash the expression of the parameters in the Neumann boundary condition of the field, and record all the custom parameters, dependent variables and corresponding coupled physical fields involved in the boundary condition class object.

[0300] c) Calculate the derivative of some parameters in the governing equation of the field.

[0301] d) Record the custom parameters and coupled physical fields involved in the calculation of the field derived field.

[0302] e) Hash the expression of the initial condition of the field, and record all the custom parameters, dependent variables and corresponding coupled physical fields involved in the condition class object.

[0303] f) Hash the expression of the Dirichlet boundary condition of the field, and record all the custom parameters, dependent variables and corresponding coupled physical fields involved in the boundary condition class object.

[0304] 5. According to the recorded information, write the following files:

[0305] a) FEPG input script, including:.mdi,.gcn,.pos,.pde,.fbc files.

[0306] b) Record file for modifying the generated C language file, and supplementary C language file.

[0307] c) File recording the geometric entities affected by the initial and boundary conditions, for generating the grid data file.

[0308] d) Project batch file.bat for controlling the calculation flow.

[0309] The above embodiments only express the specific implementation of the present application, and the description is more specific and detailed, but it cannot be understood as the limitation of the scope of the present application. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, a number of variations and improvements can be made, which are within the scope of the present application.

Claims

1. An energy and environment geotechnical multiphase flow multi-field coupling finite element automatic modeling method, characterized in that, The method comprises the following steps: Step 1, deriving general control equations for mass conservation, momentum conservation and energy conservation of multiphase materials in energy and environmental engineering based on porous medium mechanics and unsaturated soil mechanics; Step 2, constructing a weak form general format of the multiphase and multi-field coupling control equations of energy and environmental geotechnical engineering based on the Galerkin method and the Petrov-Galerkin method; Step 3, constructing the stiffness matrix of the discrete control equations of the multiphase and multi-field coupling of energy and environmental geotechnical engineering; Step 4, generating an input file of a finite element program automatic generation system FEPG.

2. The energy and environment geotechnical multiphase flow multi-field coupling finite element automated modeling method according to claim 1, characterized in that, In step 1, according to the mechanics of porous media, the porosity is defined as wherein, is the volume of pores in the medium, V is the total volume of the medium; the volume fraction of the i-th phase material in the entire medium in the porous medium is defined as wherein, is the volume of the i-th phase material; the saturation of the i-th phase material in the pores is defined as ; the general control equation specifically includes: ① Porous multiphase flow Darcy seepage equation: Selecting the mth phase of n phases of substances, the mth phase saturation is: ； Establish the calculation formula of the pressure of the i-th phase : ； wherein , is the mth phase, is a capillary force function; ； wherein, is the derivative of the capillary force function with respect to the saturation of the jth phase material The porous medium multiphase flow Darcy seepage equation is given by the continuity equation of each phase of substances in the pores and the Darcy law: ； wherein is the density of the ith phase material, k is the intrinsic permeability, is the relative permeability, is the fluid dynamic viscosity, is the gravitational acceleration, is the mass source; Summing up i from 1 to n, the equation is: ； ② Mass transfer equation with molar concentration as the independent variable: The molar concentration of the a-th solute in the i-th phase is defined as The mass transport equation is established as ； wherein, is the chemical reaction source sink of the a-th solute in the i-th phase, is the concentration diffusion coefficient of the a-th solute in the i-th phase, is the Darcy velocity of the i-th phase; ③ Mass transfer equation with mass fraction as the independent variable: Defining the mass fraction of species a in the i-th phase The species mass transport equation is established: ； wherein, Dαi is the mass diffusion coefficient of the αth solute in the ith phase; ④ System heat transfer equation: Defining the temperature of the system as T, the total heat balance equation of the system is established: ； wherein, is the heat source and sink of the ith phase, is the thermal conductivity of the system, is the specific heat capacity of the system, is the specific heat capacity of the ith phase; ⑤ Force balance equation: Defining effective stress The force balance equation is established as: ； wherein, is the pore pressure, is the Biot coefficient, is the Kronecker operator; According to the generalized Hooke's law: ； Wherein, the B matrix is the conversion matrix of strain and displacement, and D is the stiffness matrix.

3. The energy and environment geotechnical multiphase flow multi-field coupling finite element automated modeling method according to claim 2, characterized in that, In step 2, the weak form of equations (4)-(9) is established by the Galerkin method, and the following is obtained: ① Weak form general format of porous medium multiphase flow Darcy seepage equation: Weak form: expressed in terms of the solution variable of the physical field and derivative with respect to time, where may contain the variable of the field or of the coupling field, may contain the variable of the coupling field, are all evaluated using the results of the previous time step or iteration step: ； ； The weak form is finally arranged as: ； Weak form: expressed in terms of the solution variable at the current field and , derivative with respect to time: ； ； ； The weak form is finally arranged as: ； ② Weak form general format of mass transfer equation with molar concentration as the independent variable: Expressed in terms of the solution variables of the present field Derivative with respect to time: ； The weak form is finally arranged as: ； ③ Weak form general format of mass transfer equation with mass fraction as the independent variable: ； ④ Weak form general format of system heat transfer equation: ； ⑤ Weak form general format of force balance equation: ； 。 4. The energy and environment geotechnical multiphase flow multi-field coupling finite element automated modeling method according to claim 3, characterized in that, In step 3, the stiffness matrix is given by arranging the weak form equation: ① Porous multiphase flow Darcy seepage equation: : ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ② Mass transfer equation with molar concentration as the independent variable: ； ； ； ； ； ； ； ； ③ Mass transfer equation with mass fraction as the independent variable: ； ； ； ； ； ； ④ System heat transfer equation: ； ； ； ； ； ； ⑤ Force balance equation: ； ； ； ； 。 5. The energy and environmental geotechnical multiphase flow multi-field coupling finite element automated modeling method according to claim 1, wherein, The step 4 specifically comprises: (1) input and store project related information, including custom parameters, custom functions, physical fields, solution schemes; (2) for each custom parameter, hash processing is performed on its name and other parameters and solution variable names contained in its expression, and relevant information is recorded; (3) for each custom parameter, the order thereof and whether the expression thereof is associated with node information are counted; (4) each physical field is processed; (5) according to the recorded information, a file is written.

6. The energy and environment geotechnical multiphase flow multi-field coupling finite element automated modeling method according to claim 5, characterized in that, In (4), for each physical field, the following processing is performed: a) hash processing is performed on the expression of the parameters in the field control equation, and all custom parameters, solution variables and corresponding physical fields involved in the expression are recorded in the field class object; b) hash processing is performed on the expression of the parameters in the Neumann boundary condition of the field, and all custom parameters, solution variables and corresponding coupled physical fields involved in the expression are recorded in the boundary condition class object; c) the derivative of certain parameters in the field control equation is calculated; d) the custom parameters and coupled physical fields involved in the calculation of the derived field of the field are recorded. e) Hash the expression of initial condition of field, and record all the custom parameters, solving variables and corresponding coupled physical fields involved in the expression in the condition class object; f) Hash the expression of Dirichlet boundary condition of field, and record all the custom parameters, solving variables and corresponding coupled physical fields involved in the expression in the boundary condition class object.

7. The energy and environment geotechnical multiphase flow multi-field coupling finite element automated modeling method according to claim 6, characterized in that, In (5), according to the recorded information, the following files are written: a) FEPG input script, including:.mdi,.gcn,.pos,.pde,.fbc files; b) Record file for modifying the generated C language file, and supplementary C language file; c) File recording the geometric entities affected by initial and boundary conditions, used for generating mesh data file; d) Project batch file.bat for controlling the calculation flow.

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