A simulation analysis method, device and medium for bank fissure rock mass slope stability during impoundment period based on a DFM model

Abstract

The application provides a kind of based on DFM model's storage period reservoir bank fissure rock mass slope stability simulation analysis method, electronic equipment and storage medium, first, carry out geological investigation to reservoir area fissure rock mass slope, obtain rock mass and control fissure structural plane mechanical parameter and permeability coefficient;Second, the finite element numerical calculation model of reservoir area slope is meshed using matching non-structured grid, wherein the fissure uses no-thickness plane element, and the rock matrix uses solid element;Then, based on the DFM model, the coupling relationship between the "fissure surface stress-fissure opening-permeability coefficient" is established, and the COMSOL Multiphysics software is used for secondary development to realize the numerical simulation of the deformation of the reservoir bank fissure rock mass slope during the storage period, to obtain the safety factor of the slope under different storage conditions, and to realize the evaluation and analysis of the stability of the reservoir bank fissure rock mass slope during the storage process. While considering the permeability characteristics of the rock matrix, the fissure seepage characteristics in the reservoir bank slope can also be simulated explicitly.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of disaster prevention and mitigation of water conservancy and hydropower engineering or geotechnical engineering, and particularly relates to a simulation analysis method, equipment and medium for stability of a fissured rock mass slope of a reservoir bank during a reservoir period based on a DFM model. BACKGROUND

[0002] Most of the high dams in China are located in the southwest mountainous and gully areas. After the valley incision and the tectonic action of the folded mountain system, the soft structural planes such as faults, interlayer and intralayer dislocation zones are generally developed in the bank slopes on both sides, which greatly increases the possibility of slope instability. Compared with the complete rock mass, the large-scale faults in the hub area and the intralayer and interlayer dislocation zones have good water permeability and are the main network of groundwater seepage in the hub area, which plays a key control role in the interaction of surface water and groundwater and the evolution of the hydrogeological conditions in the hub area during the reservoir storage process. From the perspective of the analysis of the groundwater seepage field, when the size ratio of the normal direction to the tangent direction of the structural plane is much smaller than 1, these structural planes can be collectively referred to as fissures. Therefore, it is of important practical significance to carry out the simulation analysis of the stability of the fissured rock mass slope during the reservoir storage process.

[0003] In recent years, to describe the seepage-stress coupling behavior of fractured rock masses, scholars both domestically and internationally have developed various mathematical models. Based on the different seepage characteristics of fractured rock masses, these models can be further subdivided into Equivalent Continuum (EC) models, Dual Porosity (DP) models, Discrete Fracture Network (DFN) models, and Discrete Fracture-Matrix (DFM) models. The EC model does not consider the physical structure and geometric distribution of fractures, but rather treats the fractured rock mass as a homogeneous continuous medium. When the rock strata exhibit strong heterogeneity or the seepage path is controlled by the main fractures, this model will produce significant errors. The DP model considers the flow exchange between pores and fractures and, to some extent, characterizes the preferential flow phenomenon in fractures. However, when performing transient or non-steady seepage analysis, the flow exchange between the pore medium and the fracture medium is difficult to determine. While the DFN model can realistically describe the influence of fractures on the seepage characteristics of rock masses, it does not consider the permeability characteristics of the rock matrix or the flow exchange between the matrix system and the fracture system. Considering the limitations of the three models mentioned above, the DFM model was developed. It can explicitly simulate fracture seepage characteristics while also taking into account the permeability of the rock matrix system, making it suitable for simulating large-scale fractures. Furthermore, this method implicitly incorporates fractures into the governing equations, eliminating the need to consider fracture aperture during preprocessing. Compared to refined fracture simulation, it effectively reduces the difficulty of mesh discretization and simplifies the solution process, making it widely applicable in fields such as groundwater seepage and solute transport in fractured rock masses, geothermal resource development, and unconventional oil and gas extraction. Summary of the Invention

[0004] The first objective of this invention is to provide a simulation and analysis method for the stability of reservoir bank fractured rock mass slopes during the impoundment period based on the DFM model, in order to address the shortcomings of the existing technology. This method reveals the dynamic evolution process of reservoir bank slope deformation and stability during the impoundment process from the perspectives of fracture seepage, rock mass seepage, and fracture deformation, and overcomes the problem of difficult mesh generation for fractured rock mass slopes in existing numerical calculations.

[0005] Therefore, the above-mentioned objective of the present invention is achieved through the following technical solution:

[0006] A method for simulating and analyzing the stability of fractured rock mass slopes on reservoir banks during the impoundment period based on a DFM model, characterized by the following steps:

[0007] S1. Obtain geological information and controlling fracture structure surface information of the fractured rock mass slope in the reservoir area, determine the spatial distribution, mechanical parameters and permeability coefficient of the strata rock mass and fracture structure surface, and establish a geometric model of the reservoir bank slope.

[0008] S2. Discretize the discontinuous fracture structure surface into a thin-film planar element, discretize the stratum rock mass into a solid element, and use the Discrete Fracture-Matrix (DFM) model theory to perform finite element mesh generation on the geometric model.

[0009] S3. Based on the Biot effective stress principle and the Barton-Bandis joint model, a functional relationship between "fracture surface stress - fracture aperture - permeability coefficient" is established. The numerical solution of seepage stress coupling during reservoir bank slope water impoundment is realized through COMSOL Mulyiphysics secondary development.

[0010] S4. Based on the established model solution method, the deformation characteristics of the reservoir bank slope during different water storage processes are analyzed in COMSOL Mulyiphysics finite element software, including the changes in the seepage field and displacement field. Then, the slope safety factor under different reservoir water level conditions is obtained, and the stability of the reservoir bank fractured rock mass slope during water storage is evaluated and analyzed.

[0011] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0012] As a preferred technical solution of the present invention: In step S1:

[0013] Information on the geological conditions of the reservoir bank slope includes the controlling fracture structure planes and the spatial distribution of the strata and rock masses;

[0014] Based on the actual geological report of the project, obtain the physical and mechanical parameters and permeability coefficients of the strata, rock mass and fracture structure.

[0015] As a preferred technical solution of the present invention: In step S2:

[0016] Thickness-free planar elements were used to characterize the seepage characteristics of fissures in the bank slope during water storage.

[0017] Solid units were used to characterize the matrix seepage characteristics within the reservoir bank slope;

[0018] Based on the relevant theories of the DFM model, a matched unstructured mesh is adopted, that is, the crack is used as the internal boundary, and the numerical model finite element mesh is generated using this as a constraint.

[0019] As a preferred technical solution of the present invention: In step S3:

[0020] S301. Based on Biot's effective stress principle and the Barton-Bandis equation, considering the effects of fracture normal closure and shear dilatation during water storage, the evolution equation of fracture aperture with stress can be calculated by equation (1):

[0021]

[0022] In the formula, d f0 Let Δd be the initial aperture of the fracture. n d is the normal closure factor of the fracture. s For the crack opening caused by the dilatation effect, σ n ′ represents the effective normal stress on the fracture surface, K n0 Let d be the initial normal stiffness of the crack. nmax This represents the maximum closure amount of the fracture. Unless otherwise specified, the maximum closure amount of the fracture is d. nmax =d f0 K s Let ψ be the shear stiffness of the crack, ψ be the shear dilatation angle of the crack, and τ be the shear stiffness of the crack. c Let τ be the shear strength of the crack, and τ be the shear stress on the crack surface.

[0023] S302. Under the assumptions of small deformation and linear elasticity, the stress-strain relationship of the rock matrix during water impoundment can be characterized by equation (2):

[0024]

[0025] In the formula, D m Let ε be the elastic tensor of the rock matrix. m and u m These represent the strain and displacement of the matrix, respectively.

[0026] S303. The seepage control equation for the rock matrix and fissures during reservoir impoundment can be expressed as:

[0027]

[0028] In the formula, ρ is the porosity of the matrix, ρ is the density of water, and q is the density of water. m For the source and sink terms of the matrix, k m Let μ be the permeability of the matrix, μ be the dynamic viscosity of water, p be the water pressure, and g be the density of the matrix. z It is the acceleration due to gravity. The difference in height;

[0029]

[0030] In the formula, d f The hydraulic aperture of the fracture. Let ρ be the porosity of the fracture, ρ be the density of water, and q be the density of the water. f q represents the flow rate from the matrix into the fracture. m For the source and sink terms of the matrix;

[0031] S304. The seepage stress coupling control equations expressed by the above formulas (2), (3), and (4) are used to realize the numerical solution of the seepage stress coupling model of fractured rock mass through secondary development based on COMSOL Multiphysics software.

[0032] As a preferred technical solution of the present invention: In step S4:

[0033] S401. The deformation analysis of the reservoir bank rock mass under the coupling of seepage and stress was carried out using the Mohr-Coulomb elastoplastic constitutive model. Based on the initial water level boundary load conditions of the near and far fields of the slope, the initial seepage field and stress field distribution of the reservoir bank slope were simulated and analyzed, and the initial displacement field in the slope was "zeroed out".

[0034] S402. Based on the actual water level scheduling process in the reservoir area, numerical simulation analysis was conducted on the seepage field and stress field of the reservoir bank slope under different reservoir water level conditions to obtain the displacement distribution of the bank slope rock mass.

[0035] S403. The strength reduction method is used to obtain the safety factor of the reservoir bank slope under different water storage conditions, so as to realize the evaluation and analysis of the stability of the reservoir bank fractured rock mass slope during the water storage process.

[0036] The second objective of this invention is to provide an electronic device that addresses the shortcomings of existing technologies.

[0037] Therefore, the above-mentioned objective of the present invention is achieved through the following technical solution:

[0038] An electronic device includes a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other via the communication bus, characterized in that:

[0039] The memory, which is used to store computer programs,

[0040] The processor is used to execute the computer program stored in the memory to implement the steps of the simulation analysis method for the stability of the reservoir bank fractured rock mass slope during the impoundment period based on the DFM model described above.

[0041] Another objective of this invention is to provide a computer-readable storage medium to address the shortcomings of existing technologies.

[0042] Therefore, the above-mentioned objective of the present invention is achieved through the following technical solution:

[0043] A computer-readable storage medium, characterized in that: the computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of the aforementioned method for simulating and analyzing the stability of reservoir bank fractured rock mass slopes during the water storage period based on the DFM model.

[0044] This invention provides a method, electronic device, and storage medium for simulating and analyzing the stability of fractured rock mass slopes on reservoir banks during the impoundment period based on a DFM model. Specifically, firstly, a geological survey is conducted on the fractured rock mass slopes in the reservoir area to obtain the mechanical parameters and permeability coefficients of the rock mass and controlling fracture structural surfaces. Secondly, a matched unstructured mesh is used to mesh the finite element numerical calculation model of the reservoir slope, where the fractures are represented by thin-free planar elements and the rock matrix by solid elements. Then, based on the DFM model, the coupling relationship between "fracture surface stress - fracture aperture - permeability coefficient" is established, and secondary development is performed using COMSOL Multiphysics software to realize the numerical simulation of the deformation of fractured rock mass slopes on reservoir banks during the impoundment period, obtaining the slope safety factor under different impoundment conditions, and realizing the evaluation and analysis of the stability of fractured rock mass slopes on reservoir banks during the impoundment process. This invention considers the permeability characteristics of the rock matrix while explicitly simulating the seepage characteristics of fissures in the reservoir bank slope. Secondly, compared with the refined simulation of fissures using solid elements, this method implicitly incorporates the fissure aperture into the solution equation, which can reduce the difficulty of mesh generation and simplify the solution process.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] 1) Compared with existing methods for simulating and analyzing the stability of fractured rock mass slopes in reservoir banks, this invention effectively reveals the dynamic evolution of slope deformation and stability during water impoundment from the perspectives of fracture seepage, matrix seepage, and fracture deformation.

[0047] 2) By using a matched unstructured mesh, discontinuous fracture structures are discretized into thin-film planar elements, and the rock matrix is ​​discretized into solid elements, which greatly reduces the complexity of mesh generation.

[0048] 3) At the same time, this invention can be well applied to the simulation and analysis of fracture slope stability under complex geological conditions in the fields of water conservancy and hydropower engineering and geotechnical engineering, and the simulation calculation effect is good. Attached Figure Description

[0049] Figure 1 The overall flowchart of the simulation and analysis method for the stability of reservoir bank fractured rock mass slopes during the impoundment period based on the DFM model provided by this invention is shown in the present invention.

[0050] Figure 2 This is a geometric model diagram of a reservoir bank slope.

[0051] Figure 3This is a schematic diagram of the grid division of a reservoir bank slope.

[0052] Figure 4 A schematic diagram of the DFM model assembly.

[0053] Figure 5 This is a schematic diagram of the numerical solution process for the model.

[0054] Figure 6 This shows the initial water pressure distribution within the slope.

[0055] Figure 7 This shows the water pressure distribution at the normal water level within the slope.

[0056] Figure 8 This shows the displacement field distribution within the slope at the normal water level. Detailed Implementation

[0057] The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

[0058] A method for simulating and analyzing the stability of fractured rock mass slopes on reservoir banks during the impoundment period based on the DFM model, such as... Figure 1 As shown, it includes:

[0059] Step 1: Obtain geological information and controlling fracture structure information of the fractured rock mass slope in the reservoir area, determine the mechanical parameters and permeability coefficient of the rock mass and fracture structure, and establish a geometric model of the reservoir bank slope.

[0060] Figure 2 This is a cross-section of the right bank upstream of a hydropower station in Southwest China. The cross-section is 800m wide and 1000m high, with the main geological structures being faults (f13, f14) and weak structural planes (J1-J6). The natural river water level and the normal reservoir water level are 1630m and 1880m, respectively. After the reservoir is filled, the groundwater level at the far end rises from 1630m to 1780m.

[0061] Step 2: Discretize the discontinuous fracture structure surface into thin-film planar elements, discretize the stratum rock mass into solid elements, and use the Discrete Fracture-Matrix (DFM) model theory to perform finite element mesh generation on the geometric model;

[0062] Model mesh generation as follows Figure 3 As shown, it contains a total of 8533 units and 4407 nodes.

[0063] Step 3: Based on Biot's effective stress principle and the Barton-Bandis joint model, establish the functional relationship between "fracture surface stress - fracture aperture - permeability coefficient", and use COMSOL Mulyiphysics to achieve numerical solution of seepage stress coupling during reservoir bank slope water impoundment.

[0064] Figure 4 The diagram shows the assembly of the discrete fracture matrix model, and the flowchart for the secondary development and solution of the model is as follows. Figure 5 As shown.

[0065] Step 4: Based on the established model solution method, analyze the deformation characteristics of the reservoir bank slope during different water storage processes in COMSOL Mulyiphysics finite element software, including the changes in the seepage field and displacement field, and then obtain the safety factor of the slope under different conditions.

[0066] Figure 6 and Figure 7 The distribution of fissure water pressure and pore water pressure within the slope at different water levels was plotted. The horizontal and vertical displacement distribution of the slope at normal water level is shown below. Figure 8 As shown.

[0067] from Figure 6 and Figure 7 As can be seen, the fissure water pressure gradually increases with the rise of the reservoir water level. At the initial water level, the maximum fissure water pressure is 3.24 MPa; when the reservoir reaches its normal water level (1880 m), the fissure water pressure increases to 5.432 MPa. From... Figure 8 It can be seen that the largest horizontal displacement of the slope after water impoundment occurred near the outlet of structural plane J2 and fault f14. Due to the deformation of the fissures, the horizontal displacement of the slope exhibits obvious discontinuous characteristics.

[0068] Compared with existing methods for simulating and analyzing the stability of reservoir bank fractured rock slopes, this invention can effectively reveal the dynamic evolution of reservoir bank slope deformation and stability during water impoundment from the perspective of fracture seepage and fracture deformation.

[0069] The present invention also provides an electronic device, which includes a processor, a communication interface, a memory, and a communication bus. The processor, the communication interface, and the memory communicate with each other via the communication bus. The memory is used to store computer programs.

[0070] The processor is used to execute the computer program stored in the memory to implement the steps of the simulation analysis method for the stability of the reservoir bank fractured rock mass slope during the impoundment period based on the DFM model described above.

[0071] It should be understood that in this embodiment, the processor can be a central processing unit (CPU), or it can be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor, etc.

[0072] Memory may include read-only memory and random access memory, and provides instructions and data to the processor. A portion of memory may also include non-volatile random access memory. For example, memory may also store information about the device type.

[0073] The present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the simulation and analysis method for the stability of reservoir bank fractured rock mass slopes during the impoundment period based on the DFM model described above.

[0074] The above method can be directly implemented by a hardware processor, or implemented using a combination of hardware and software modules within the processor. The software modules can reside in readily available storage media in the field, such as random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, or registers. This storage medium is located in memory, and the processor reads information from the memory and, in conjunction with its hardware, completes the steps of the above method. To avoid repetition, a detailed description is not provided here.

[0075] Those skilled in the art will recognize that the units, i.e., algorithm steps, of the various examples described in connection with this embodiment can be implemented in electronic hardware or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0076] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for simulating and analyzing the stability of fractured rock mass slopes on reservoir banks during the impoundment period based on a DFM model, characterized in that: The method includes the following steps: S1. Obtain geological conditions and controlling fracture structure information of the fractured rock mass slope in the reservoir area, determine the spatial distribution, mechanical parameters and permeability coefficient of the strata rock mass and fracture structure, and establish a geometric model of the reservoir bank slope. S2. Discretize the discontinuous fracture structure surface into a thin-film planar element, discretize the stratum rock mass into a solid element, and use the discrete fracture-matrix model theory to perform finite element mesh generation on the geometric model. S3. Based on the Biot effective stress principle and the Barton-Bandis joint model, a functional relationship between "fracture surface stress - fracture aperture - permeability coefficient" is established. The numerical solution of seepage stress coupling during reservoir bank slope water storage is realized through COMSOL Mulyiphysics secondary development. S4. Based on the established model solution method, the deformation characteristics of the reservoir bank slope during different water storage processes are analyzed in COMSOL Mulyiphysics finite element software, including the changes in the seepage field and displacement field. Then, the slope safety factor under different reservoir water level conditions is obtained, and the stability of the reservoir bank fractured rock mass slope during water storage is evaluated and analyzed. In step S3: S301. Based on Biot's effective stress principle and the Barton-Bandis equation, considering the effects of fracture normal closure and shear dilatation during water storage, the evolution equation of fracture aperture with stress can be calculated by equation (1): (1) In the formula, The initial aperture of the crack. This represents the normal closure amount of the fracture. The crack opening is caused by the dilatation effect. The effective normal stress of the fracture surface, The initial normal stiffness of the crack is... This is the maximum closure amount of the fracture. Unless otherwise specified, the maximum closure amount of the fracture is... , The shear stiffness of the crack. The shear dilatation angle of the crack. The shear strength of the crack. τ This represents the shear stress on the crack surface; S302. Under the assumptions of small deformation and linear elasticity, the stress-strain relationship of the rock mass during water impoundment can be characterized by equation (2): (2) In the formula, For the elastic tensor of the rock matrix, ε m and These represent the strain and displacement of the matrix, respectively. S303. The seepage control equation for the rock matrix and fissures during reservoir impoundment can be expressed as: (3) In the formula, The porosity of the matrix, The density of water, For the source and sink terms of the matrix, The permeability of the matrix, p For water pressure, μ The dynamic viscosity of water, Let ∠z be the acceleration due to gravity, and ∠z be the height difference. (4) In the formula, d f The hydraulic aperture of the fracture. The porosity of the fracture. The density of water, This represents the flow rate from the matrix into the fracture. For the source and sink terms of the matrix; S304. The seepage stress coupling control equations expressed by the above formulas (2), (3), and (4) are used to realize the numerical solution of the seepage stress coupling model of fractured rock mass through secondary development based on COMSOL Multiphysics software.

2. The method for simulating and analyzing the stability of fractured rock mass slopes on reservoir banks during the impoundment period based on the DFM model as described in claim 1, characterized in that: In step S1: Information on the geological conditions of the reservoir bank slope includes the controlling fracture structure planes and the spatial distribution of the strata and rock masses; Based on the actual geological report of the project, obtain the physical and mechanical parameters and permeability coefficients of the strata, rock mass and fracture structure.

3. The method for simulating and analyzing the stability of fractured rock mass slopes on reservoir banks during the impoundment period based on the DFM model as described in claim 1, characterized in that: In step S2: Thickness-free planar elements were used to characterize the seepage characteristics of fissures in the bank slope during water storage. Solid units were used to characterize the matrix seepage characteristics within the reservoir bank slope; Based on the relevant theories of the DFM model, a matched unstructured mesh is adopted, that is, the crack is used as the internal boundary, and the numerical model finite element mesh is generated using this as a constraint.

4. The method for simulating and analyzing the stability of fractured rock mass slopes on reservoir banks during the impoundment period based on the DFM model according to claim 1, characterized in that: In step S4: S401. The deformation analysis of the reservoir bank rock mass under the coupled action of seepage and stress was carried out using the Mohr-Coulomb elastoplastic constitutive model. Based on the initial water level boundary load conditions of the near and far fields of the slope, the initial seepage field and stress field distribution of the reservoir bank slope were simulated and analyzed, and the initial displacement field in the slope was "zeroed out". S402. Based on the actual water level scheduling process in the reservoir area, numerical simulation analysis was conducted on the seepage field and stress field of the reservoir bank slope under different reservoir water level conditions to obtain the displacement distribution of the bank slope rock mass. S403. The strength reduction method is used to obtain the safety factor of the reservoir bank slope under different water storage conditions, so as to realize the evaluation and analysis of the stability of the reservoir bank fractured rock mass slope during the water storage process.

5. An electronic device, comprising a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other via the communication bus, characterized in that: The memory, which is used to store computer programs, A processor, wherein the processor is configured to execute a computer program stored in a memory to implement the steps of the method for simulating and analyzing the stability of reservoir bank fractured rock mass slopes during the impoundment period based on the DFM model as described in any one of claims 1-4.

6. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of the method for simulating and analyzing the stability of fractured rock mass slopes on reservoir banks during the impoundment period based on the DFM model as described in any one of claims 1-4.

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