A simulation method, device and storage medium for sand seepage damage

Abstract

The embodiment of the present invention discloses a simulation method, device and storage medium for seepage damage of sand. The method is used to simulate the seepage damage of target fluid to target sand. The method comprises: establishing a fluid simulation model of the target fluid according to the material point method MPM, wherein the fluid simulation model comprises: an MPM fluid domain and MPM particles located in the MPM fluid domain; establishing a sand simulation model of the target sand according to the discrete element method DEM, wherein the sand simulation model comprises: a DEM solid particle domain and DEM particles located in the DEM solid particle domain; and simulating the seepage damage of the target fluid to the target sand according to the fluid simulation model and the sand simulation model. The embodiment of the present invention combines the advantages of both the MPM and DEM methods, and can therefore more realistically simulate the seepage damage of the target fluid to the target sand.

Description

Technical Field

[0001] The present invention relates to the field of numerical simulation technology, and in particular to a simulation method, device and storage medium for sand seepage failure. Background Art

[0002] Sandy soil refers to soil with a sand content greater than 50%. It has a highly fragmented structure and a large number of complex and random pore structures. Under the mechanical or chemical action of infiltrating water, sandy soil particles will gradually break away from the soil skeleton, resulting in gradual erosion of sandy soil particles inside the soil body, and eventually causing pipe bursts, underground cavities or surface collapse, which seriously threatens the safety of buildings such as dams, embankments and foundation pits, and the stability of the accumulated slope. Therefore, simulation of seepage damage to sandy soil bodies is of great significance for predicting and controlling related accidents and disasters.

[0003] In the existing technology, physical test methods can be used to simulate the seepage damage of sand, but the physical test method has problems such as long cycle, high cost, and difficulty in sample preparation to ensure that the experimental results are consistent with the on-site soil. The erosion damage of sand caused by seepage is a complex fluid-solid coupling process, involving particle-particle interaction at the particle scale and fluid-solid coupling at the coarse skeleton pore scale. A more sophisticated method is needed to truly simulate the seepage damage of sand. Summary of the invention

[0004] The main purpose of the present invention is to provide a simulation method, device and storage medium for sand seepage failure, which can simulate sand seepage failure more realistically.

[0005] In order to achieve the above-mentioned invention object, an embodiment of the present invention provides a simulation method for seepage damage of sand, which is used to simulate the seepage damage of a target fluid to a target sand, including: according to a material point method MPM, a fluid simulation model of the target fluid is established, wherein the fluid simulation model includes: an MPM fluid domain and MPM particles located in the MPM fluid domain; according to a discrete element method DEM, a sand simulation model of the target sand is established, wherein the sand simulation model includes: a DEM solid particle domain and DEM particles located in the DEM solid particle domain; according to the fluid simulation model and the sand simulation model, the seepage damage of the target fluid to the target sand is simulated until the simulation time reaches a preset value and stops, specifically including: S1: starting the simulation; S2: calculating the force of the DEM particles on the MPM particles; S3: according to the force of the DEM particles on the MPM particles, calculating the effect of the MPM fluid domain on the DEM solid particle domain to update the DEM particles; and S4: judging whether the simulation time reaches the preset value, if not, returning to step S2, otherwise stopping the simulation.

[0006] Wherein, according to the material point method MPM, a fluid simulation model of the target fluid is established, including: establishing the fluid simulation model with the Euler grid as the background grid and the particles as the Lagrangian units; calculating the motion deformation of the particles on the background grid, and mapping the calculated value of each node in the background grid to the particles in each grid to update the motion deformation of the particles; wherein the background grid serves as the MPM fluid domain, and the particles serve as the MPM particles.

[0007] Among them, the sand simulation model of the target sand is established according to the discrete element method DEM, including: generating a DEM solid particle domain; generating DEM particles representing the target sand in the DEM solid particle domain; and using a parallel bonding contact model to calculate the static force of the DEM particles to a stable state.

[0008] The generating of DEM particles representing the target sand includes: generating DEM particles representing the target sand according to the particle size of the target sand.

[0009] Wherein, the calculation of the force exerted by the DEM particles on the MPM particles includes: searching for background grid nodes corresponding to the MPM particles around the DEM particles; discretizing the momentum of the DEM particles to the corresponding background grid nodes, and synthesizing them with the mapped momentum of the MPM particles; and mapping the synthesized momentum from the background grid back to the MPM particles to complete the calculation of the contact force of the DEM particles on the MPM particles.

[0010] Among them, according to the force of the DEM particles on the MPM particles, the effect of the MPM fluid domain on the DEM solid particle domain is calculated to update the DEM particles, including: reacting the force of the DEM particles on the MPM particles to the centroid of the DEM particles to calculate the force exerted on the DEM particles, and updating the physical parameters of the DEM particles through the DEM motion equation.

[0011] The forces acting on the DEM particles include at least one of the following: drag force, pressure difference force, buoyancy and gravity.

[0012] Wherein, the physical parameters of the DEM particles include at least one of the following: displacement, velocity and acceleration.

[0013] An embodiment of the present invention further provides a simulation device for sand seepage failure, which is used to simulate the seepage failure of a target fluid on target sand, including: a first modeling module, configured to establish a fluid simulation model of the target fluid according to the Material Point Method (MPM), where the fluid simulation model includes: an MPM fluid domain and MPM particles located within the MPM fluid domain; a second modeling module, configured to establish a sand simulation model of the target sand according to the Discrete Element Method (DEM), where the sand simulation model includes: a DEM solid particle domain and DEM particles located within the DEM solid particle domain; and a simulation module, configured to simulate the seepage failure of the target fluid on the target sand according to the fluid simulation model and the sand simulation model, and stop when the simulation time reaches a preset value; wherein, the simulation module specifically includes: a start unit, configured to start the simulation; a first calculation unit, configured to calculate the force exerted by the DEM particles on the MPM particles; a second calculation unit, configured to calculate the effect of the MPM fluid domain on the DEM solid particle domain according to the force exerted by the DEM particles on the MPM particles, so as to update the DEM particles; and a control unit, configured to determine whether the simulation time reaches the preset value. If it does not reach the preset value, the first and second calculation units are repeatedly executed, otherwise the simulation is controlled to stop.

[0014] An embodiment of the present invention further provides a computer-readable storage medium, storing a computer program which, when executed by a processor, implements the simulation method for sand seepage failure as described above.

[0015] Advantages of the embodiment of the present invention:

[0016] In the embodiment of the present invention, the Material Point Method and the Discrete Element Method are combined to simulate the seepage failure of a target fluid on target sand, so that the sand seepage failure can be simulated more realistically. Description of the Drawings

[0017] Figure 1 is a schematic flowchart of an embodiment of the simulation method for sand seepage failure of the present invention;

[0018] Figure 2 is Figure 1 a schematic flowchart of an embodiment of step S13 in

[0019] Figure 3 a schematic distribution diagram of the MPM fluid domain and the DEM solid particle domain of the embodiment of the present invention;

[0020] Figure 4 is a schematic diagram for calculating the contact force of the DEM solid particles on the MPM particles in the embodiment of the present invention;

[0021] Figure 5is a schematic diagram of the force generated by fluid-solid contact acting on DEM particles in an embodiment of the present invention;

[0022] Figure 6 It is a schematic diagram of the flow chart of an embodiment of the device for simulating sand seepage failure of the present invention. DETAILED DESCRIPTION

[0023] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0024] In the subsequent description, the suffixes such as "module", "component" or "unit" used to represent elements are only used to facilitate the description of the present invention, and have no specific meanings. Therefore, "module", "component" or "unit" can be used in a mixed manner.

[0025] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0026] The present invention is described below by way of embodiments with reference to the accompanying drawings.

[0027] As background, DEM (Discrete Element Method) and MPM (Material Point Method) are first explained.

[0028] Among them, DEM (Discrete Element Method) is a granular discrete material analysis method first proposed by American scholar Professor Cundall PA in 1971 based on the principle of molecular dynamics. This method was first applied to the analysis of rock mechanics problems, and then gradually applied to the field of bulk materials and powder engineering. The basic principle of DEM is to regard the jointed rock mass as composed of discrete rock blocks and joint surfaces between rock blocks, allowing rock blocks to translate, rotate and deform, while joint surfaces can be compressed, separated or slide. Therefore, the rock mass is regarded as a discontinuous discrete medium. Large displacement, rotation, sliding and even block separation can exist inside it, so that the nonlinear large deformation characteristics in the jointed rock mass can be simulated more realistically. The general solution process of the discrete element method is: discretize the solution space into a discrete element unit array, and connect two adjacent units with reasonable connecting elements according to the actual problem; the relative displacement between units is the basic variable, and the normal and tangential forces between the two units can be obtained from the relationship between force and relative displacement; the force between the unit and other units in all directions and the external forces caused by other physical fields on the unit are calculated, and the acceleration of the unit can be obtained according to Newton's second law of motion; integrate it over time to obtain the velocity and displacement of the unit. Thus, the physical quantities such as velocity, acceleration, angular velocity, linear displacement and rotation angle of all units at any time are obtained. The discrete element method provides a platform for solving many comprehensive problems involving particles, structures, fluids, electromagnetics and their coupling by establishing a parametric model of the solid particle system. It has become a powerful tool for process analysis, design optimization and product development. At present, the application of DEM in the industrial field has gradually matured, and there are many commercial software that support DEM.

[0029] MPM (Material Point Method) is a numerical method proposed by Sulsky and Chen et al. in 1994. Its origin can be traced back to the particle-in-cell (PIC) method proposed in the late 1950s. In order to solve complex fluid mechanics problems, Harlow of Los Alamos National Laboratory (LANL) and his computational fluid dynamics team proposed the PIC method in 1955 (Harlow 1964). PIC uses Lagrangian and Euler dual descriptions, that is, the material is discretized into a group of particles, which only carry mass and position information to facilitate tracking of material interfaces, and the corresponding physical quantities are calculated on the Euler grid, and the information interaction between the particles and the Euler grid is completed through the interpolation function. In order to solve the defect of high numerical dissipation of the PIC method caused by the particles only carrying mass and position information, Brackbill et al. (1986, 1988) developed the FLIP method based on PIC. In FLIP, particles carry more physical quantities, such as momentum and energy. In order to apply FLIP to solid mechanics problems, Sulsky (1994) made the following improvements to the FLIP method: the particles carry all material information, and the constitutive equations are calculated at the particles to facilitate the processing of history-related materials; the discrete format of the momentum equation is established by using the equivalent integral weak form; explicit time integration is used. The modified FLIP method is called the material point method. Compared with other meshless methods, the single-step calculation of the material point method is similar to the Lagrangian finite element method solution, and there is no need to establish a list of neighboring particles of the particle, so it has advantages in algorithm stability and efficiency. MPM can be used for the calculation of complex flow fields and can well describe the mechanical problems of water-soil interaction in geotechnical problems, so it has a wide range of applications in geotechnical engineering.

[0030] However, in the prior art, only DEM or MPM is generally used alone. In order to take advantage of both methods, the embodiment of the present invention couples the two methods to calculate the seepage damage of sand, so that the seepage damage of sand can be simulated more realistically, providing an effective analysis tool for understanding the microscopic mechanism of sand particle migration. In addition, the fluid-solid coupling implementation method of the embodiment of the present invention is simple and clear, and can reproduce the migration process of fine particles in the coarse skeleton in a concise way. At the same time, the MPM method can reveal the changing laws of local flow velocity and pressure at the pore scale of the sand body, providing a new solution for understanding the seepage damage of the sand body.

[0031] Specifically, if Figure 1FIG. 1 is a flow chart of an embodiment of a method for simulating seepage damage of sand soil according to the present invention. The method is used to simulate the seepage damage of a target fluid to a target sand soil, and specifically includes:

[0032] Step S11: Establish a fluid simulation model of the target fluid according to the material point method MPM.

[0033] The fluid simulation model includes: an MPM fluid domain and MPM particles located in the MPM fluid domain.

[0034] Specifically, step S11 includes: firstly establishing a fluid simulation model with an Euler grid as a background grid and particles as Lagrangian units; then calculating the particle motion deformation on the background grid, and mapping the calculated values ​​of each node in the background grid to the particles in each grid to update the particle motion. The background grid is the MPM fluid domain, and the particles are the MPM particles.

[0035] Step S12: establishing a sand simulation model of the target sand according to the discrete element method DEM.

[0036] The sand simulation model includes: a DEM solid particle domain and DEM particles located in the DEM solid particle domain.

[0037] Specifically, step S12 includes: first generating a DEM solid particle domain; then, generating DEM particles representing the target sand in the DEM solid particle domain; finally, using a parallel bonding contact model, calculating the static force of the DEM particles to a stable state. When generating DEM particles, DEM particles representing the target sand can be generated according to the particle size. The generated DEM particles can all be disc-shaped.

[0038] The MPM fluid domain of step S11 and the DEM solid particle domain of step S12 are adjacent or overlapped, for example, Figure 3 FIG. 1 is a schematic diagram showing the distribution of the MPM fluid domain and the DEM solid particle domain in an embodiment. Figure 3 In the figure, the DEM solid particle domain and the MPM fluid domain overlap, and as shown in the figure, the MPM fluid domain includes: a plurality of MPM particles of uniform size and arranged at equal intervals, and the DEM solid particle domain includes: DEM particles of inconsistent size but uniform shape, and in the figure, the MPM particles surround the DEM particles.

[0039] Step S13: simulating the seepage damage of the target fluid to the target sand according to the fluid simulation model and the sand simulation model, and stopping when the simulation time reaches a preset value.

[0040] The preset values ​​can be designed according to needs. By flexibly setting the preset values, the seepage damage of the fluid to the target sand at different time points can be simulated, which makes it easier for researchers to observe and evaluate the seepage conditions of the target sand.

[0041] Specifically, in step S13, the advantages of both MPM and DEM are combined by combining the fluid simulation model based on MPM and the sand simulation model based on DEM to simulate the seepage failure of sand more realistically. Figure 2 As shown, step S13 may include the following steps:

[0042] Step S21: Start simulation.

[0043] Step S22: Calculate the force exerted by the DEM particles on the MPM particles.

[0044] The calculation of the force exerted by DEM particles on MPM particles specifically includes: searching for the background grid nodes corresponding to the MPM particles around the DEM particles; discretizing the momentum of the DEM particles to the corresponding background grid nodes and synthesizing them with the mapped momentum of the MPM particles; and mapping the synthesized momentum from the background grid back to the MPM particles to complete the calculation of the contact force of the DEM particles on the MPM particles.

[0045] Specifically, in step S22, by adding the fluid stress-strain relationship and state equation, the MPM material points around each DEM particle are found, and the contact penalty function method is used to discretize the DEM particle force into the fluid. Specifically, the stress-strain relationship and state equation are added as follows:

[0046] The governing differential equation for mass conservation is:

[0047]

[0048] Where ρ(x, t) is the fluid density, v(x, t) is the fluid velocity, t is the time, and x is the spatial coordinate at time t.

[0049] The momentum equation in updated Lagrangian format is:

[0050]

[0051] Where: a(x, t) is the acceleration; σ(x, t) is the Cauchy stress tensor, and b(x, t) is the specific volume force.

[0052] The stress-strain relationship is:

[0053]

[0054] Where: λ is the bulk viscosity; μ is the shear viscosity; P is the fluid particle pressure; I is the second-order unit tensor.

[0055] Further, in step S22, the information mapping between the particle and the background grid is performed by the shape function N j (x) is implemented. I is used to represent the variables of the background grid nodes, and p is used to represent the variables carried by the particle. The momentum M of the material point p is p (x) is:

[0056]

[0057] Specifically, the schematic diagram of the contact force calculation between DEM solid particles and MPM fluid particles is as follows: Figure 4 shown.

[0058] Step S23: According to the force of the DEM particles on the MPM particles, the effect of the MPM fluid domain on the DEM solid particle domain is calculated to update the DEM particles.

[0059] Wherein, step S23 specifically includes: reacting the force exerted by the DEM particles on the MPM particles to the centroid of the DEM particles to calculate the force exerted on the DEM particles, and updating the physical parameters of the DEM particles through the DEM motion equation. Wherein, the force exerted on the DEM particles includes at least one of the following: drag force, pressure difference force, buoyancy and gravity. Wherein, the physical parameters of the DEM particles include at least one of the following: displacement, velocity and acceleration.

[0060] Specifically, the force generated by fluid-solid contact is mapped to the centroid of the DEM particles through the background grid nodes, and the motion of the solid particles follows the following formula:

[0061]

[0062] Where F ij is the force exerted by fluid particle i on solid particle j, m j is the mass of solid particle j, a j (x, t) is the acceleration of the solid particle.

[0063]

[0064] Where t 0 is the initial time, t 1 is the moment after one time step, v j t 1 The velocity of the solid particle j at time instant.

[0065]

[0066] The schematic diagram of the force generated by fluid-solid contact acting on DEM particles is shown in Figure 5 As shown. PQ represents DEM particles. M PQ is the rotational torque of particle P from particle Q, F ij is the force generated by fluid-solid contact, is the interaction force between two particles obtained by DEM method, G P is the gravity acting on particle P.

[0067] Step S24: Determine whether the simulation time reaches a preset value. If not, return to step S22; otherwise, stop the simulation.

[0068] The method of this embodiment can combine MPM and DEM. Therefore, it can take advantage of the MPM simulation fluid calculation, quickly calculate the fluid-solid interaction force, and accurately solve the seepage flow field of the sand body pore scale. At the same time, MPM can study the influence of parameters such as permeability coefficient, hydraulic gradient, porosity and the migration rate of sand particles, and provide a new solution for understanding the migration law of sand particles; and DEM can further study the relationship between influencing factors such as gradation continuity, sand particle sequence, and sand mechanical parameters and the migration law of sand particles, which is helpful to analyze the migration law of sand particles under the action of seepage erosion. Therefore, this embodiment can simulate the interaction between sand particles and pore seepage and sand particles more realistically at the sand particle scale and pore scale, realize the simulation of the whole process of erosion damage in the sand body, and can reasonably predict the seepage damage caused by the migration of sand particles caused by seepage;.

[0069] like Figure 6 FIG. 1 is a schematic diagram of the structure of an embodiment of a simulation device for sand seepage damage of the present invention. The simulation device is used to simulate the seepage damage of a target fluid to a target sand, and specifically includes:

[0070] A first modeling module 61 is used to establish a fluid simulation model of the target fluid according to a material point method MPM, wherein the fluid simulation model includes: an MPM fluid domain and MPM particles located in the MPM fluid domain;

[0071] The second modeling module 62 is used to establish a sand simulation model of the target sand according to a discrete element method DEM, wherein the sand simulation model includes: a DEM solid particle domain and DEM particles located in the DEM solid particle domain; and

[0072] The simulation module 63 is used to simulate the seepage damage of the target fluid to the target sand according to the fluid simulation model and the sand simulation model, until the simulation time reaches a preset value and stops. Specifically, as shown in the figure, the simulation module 63 includes: a starting unit 631, used to start the simulation; a first calculation unit 632, used to calculate the force of the DEM particles on the MPM particles; a second calculation unit 633, used to calculate the effect of the MPM fluid domain on the DEM solid particle domain according to the force of the DEM particles on the MPM particles, so as to update the DEM particles; and a control unit 634, used to determine whether the simulation time reaches the preset value, if not, the first and second calculation units are repeatedly executed, otherwise the simulation is controlled to stop.

[0073] It should be noted that the details of the operations performed by the above-mentioned device have been described in the above-mentioned method embodiment and will not be repeated here.

[0074] In addition, an embodiment of the present invention further provides a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, the method for simulating seepage failure of sand as described above is implemented.

[0075] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or system. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or system including the element.

[0076] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0077] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) as described above, and includes a number of instructions for a terminal device (which can be a mobile phone, computer, server, controller, or network device, etc.) to execute the methods described in each embodiment of the present invention.

[0078] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A simulation method for sand seepage damage, used to simulate the seepage damage of target fluid to target sand, It is characterized in that include: According to the material point method MPM, a fluid simulation model of the target fluid is established, wherein the fluid simulation model includes: an MPM fluid domain and MPM particles located in the MPM fluid domain; According to the discrete element method DEM, a sand simulation model of the target sand is established, wherein the sand simulation model includes: a DEM solid particle domain and DEM particles located in the DEM solid particle domain; and According to the fluid simulation model and the sand simulation model, simulating the seepage damage of the target fluid to the target sand until the simulation time reaches a preset value, specifically including: S1: Start simulation; S2: calculating the force exerted by the DEM particles on the MPM particles; S3: Calculate the effect of the MPM fluid domain on the DEM solid particle domain according to the force of the DEM particle on the MPM particle, so as to update the DEM particle; and S4: Determine whether the simulation time reaches a preset value. If not, return to step S2; otherwise, stop the simulation. According to the material point method MPM, a fluid simulation model of the target fluid is established, including: Establishing the fluid simulation model using the Euler grid as the background grid and the particles as the Lagrangian units; Calculating the motion deformation of particles in the background grid, and mapping the calculated value of each node in the background grid to particles in the respective grids to update the motion deformation of the particles; Wherein, the background grid serves as the MPM fluid domain, and the particles serve as the MPM particles; The calculating the force of the DEM particles on the MPM particles comprises: Searching for background grid nodes corresponding to the MPM particles around the DEM particles; Discretizing the momentum of the DEM particles to corresponding background grid nodes and synthesizing it with the mapped momentum of the MPM particles; and The synthesized momentum is mapped back from the background grid to the MPM particles to complete the contact force calculation of the DEM particles on the MPM particles.

2. A method for simulating seepage failure of sand soil as claimed in claim 1, It is characterized in that The method of establishing a sandy soil simulation model of the target sandy soil according to the discrete element method DEM comprises: Generate DEM solid particle domain; In the DEM solid particle domain, generating DEM particles representing the target sand; and The static forces of the DEM particles were calculated to a steady state using a parallel bond contact model.

3. A method for simulating sand seepage failure as claimed in claim 2, It is characterized in that The generating of DEM particles representing the target sand includes: For the target sand, DEM particles representing the target sand are generated according to the particle size.

4. A method for simulating sand seepage failure as claimed in claim 1, It is characterized in that The calculating the effect of the MPM fluid domain on the DEM solid particle domain according to the force of the DEM particles on the MPM particles to update the DEM particles includes: The force exerted by the DEM particle on the MPM particle is reacted to the centroid of the DEM particle to calculate the force exerted on the DEM particle, and the physical parameters of the DEM particle are updated through the DEM motion equation.

5. A method for simulating seepage failure of sand soil as claimed in claim 4, It is characterized in that The forces acting on the DEM particles include at least one of the following: drag force, pressure difference force, buoyancy force and gravity.

6. A method for simulating sand seepage failure as claimed in claim 4, It is characterized in that The physical parameters of the DEM particles include at least one of the following: displacement, velocity and acceleration.

7. A computer-readable storage medium storing a computer program, It is characterized in that When the computer program is executed by a processor, the method for simulating sand seepage failure according to any one of claims 1 to 6 is implemented.

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