A landslide surge simulation method based on particle discrete element and SPH

Abstract

The present invention discloses a landslide surge simulation method based on particle discrete element and SPH, including: (1) establishing a particle discrete element initial model; (2) calculating the buoyancy and water resistance of particles in water according to the water level when the landslide slides down; (3) extracting the velocity vector of the particles, and exporting the velocity vector as a sliding body particle coordinate file to obtain the motion state of each particle; (4) performing landslide motion particle discrete element calculation to obtain the landslide instability evolution process; (5) establishing an SPH landslide surge calculation model based on the particle discrete element initial model; (6) setting the motion form of each particle of the sliding body part in the SPH landslide surge calculation model to obtain the landslide surge evolution process, the process of the sliding body entering the water to arouse the surge and the surge propagation process. The present invention solves the problem that it is difficult to accurately represent the movement of the landslide body due to boundary conditions in the SPH method, accurately considers the influence of the rock and soil material and the mechanical parameters of the sliding surface on the landslide surge, and makes the calculation results conform to reality.

Description

Technical Field

[0001] The invention relates to a landslide surge simulation method in the field of geotechnical engineering, and in particular to a landslide surge simulation method based on particle discrete element and SPH. Background Art

[0002] Landslide surge is an important factor affecting the safety of the reservoir area, seriously threatening the safety of life and property of people on both sides of the river and the stable operation of the dam. Correctly assessing landslide surge disasters and conducting targeted prevention and control has important scientific significance and engineering value.

[0003] As a meshless particle method, the smoothed particle hydrodynamics (SPH) calculation method has great advantages in solving large deformation, free surface flow, complex interface motion and other processes. It has high computational efficiency and good robustness. It has achieved good results in solving fluid-solid coupling large deformation problems. It has been widely used in the field of hydrodynamics and can better simulate the process of fluid motion.

[0004] However, the SPH method uses regularly distributed particles to establish a calculation model, resulting in a step-shaped sliding surface instead of a smooth plane. The movement of the sliding body is seriously affected by the step-shaped sliding surface, and it is unable to accurately reflect the movement characteristics of the sliding body. At the same time, the mechanical parameters of the sliding surface have a significant control effect on the movement of the landslide, while the boundary conditions in the SPH method are difficult to reflect the influence of the actual sliding surface cohesion and internal friction angle on the movement of the sliding body. This leads to certain difficulties in using the SPH method to calculate the landslide surge problem.

[0005] As an effective method for studying the evolution of landslide movement, the discrete element method can accurately consider the morphological characteristics and physical and mechanical properties of the sliding surface. However, it is difficult to consider the influence of water on particle movement in the discrete element method, and it is impossible to directly calculate the surge caused by the landslide entering the water. Summary of the invention

[0006] Purpose of the invention: In view of the problems existing in the SPH method when simulating and calculating landslide surges, the present invention proposes a landslide surge simulation method based on particle discrete element and SPH, thereby giving full play to the advantages of the particle discrete element calculation method in accurately describing the landslide movement and the SPH method in simulating and calculating surge problems, obtaining the evolution process of landslide surges, the surges caused by the sliding body entering the water, and the process of surge propagation, so that the landslide surge calculation results are more in line with the actual situation, and solving the problem that the SPH method is difficult to accurately represent the movement of the landslide body due to boundary conditions.

[0007] Technical solution: The landslide surge simulation method based on particle discrete element and SPH of the present invention comprises the following steps:

[0008] (1) Establishing the initial particle discrete element model according to geological conditions, including steps (1.1) to (1.2):

[0009] (1.1) Process the geological map to obtain the sliding surface, sliding body and water body;

[0010] (1.2) The sliding body and sliding surface are exported to the particle discrete element calculation software to establish the landslide movement evolution calculation model, in which the sliding body is discretized using particles and the sliding surface is represented by Wall.

[0011] (2) Calculate the buoyancy F of the particles in the water based on the water level when the landslide is sliding down b and water resistance F d ;

[0012] (3) extracting the velocity vector of the particle and deriving the velocity vector to obtain the motion state of each particle;

[0013] (4) Perform discrete element calculation of landslide motion particles to obtain the instability evolution process of the landslide; the specific process is as follows:

[0014] (4.1) Calibrate and set the mechanical parameters of the sliding body and sliding surface according to geological materials, and set the sliding surface as a fixed boundary or a dynamic boundary;

[0015] (4.2) During the calculation process, the influence of water on the particles is calculated based on the water resistance and buoyancy calculation method of the particles moving underwater;

[0016] (4.3) extracting the velocity of the particles during the calculation process, and exporting the velocity as a sliding body particle motion velocity file;

[0017] (4.4) Set the calculation time and use particle discrete elements to simulate the landslide movement. When the landslide movement stops, terminate the simulation.

[0018] (5) The SPH landslide surge calculation model is established based on the particle discrete element initial model. The specific process is as follows:

[0019] (5.1) offsetting the sliding surface obtained in step (1.1) into a sliding surface with thickness, and exporting the offset sliding surface as a sliding surface STL file; closing the water body part and exporting it as a water body STL file;

[0020] (5.2) Export the diameter and coordinates of the particles before the landslide calculation in the particle discrete element landslide motion evolution calculation model as a sliding body particle coordinate file;

[0021] (5.3) Use the water body STL file, sliding surface STL file and sliding body particle coordinate file to establish the landslide surge SPH model.

[0022] (6) Setting the motion form of each particle in the sliding body part of the SPH landslide surge calculation model;

[0023] (7) Set the calculation time, gravity, and smooth length, and use the SPH landslide surge calculation model to calculate the landslide surge, obtain the landslide surge evolution process, the process of the sliding body entering the water to stir up the surge, and the surge propagation process.

[0024] In step (2), when the particle is completely on the water surface, the buoyancy and water resistance of the particle are zero; when the particle is completely submerged in water or half submerged in water, the buoyancy and water resistance of the particle are taken into account.

[0025] In step (2), the buoyancy F of the particle in water is b for:

[0026] F b =-ρ f V i g

[0027] In the formula, ρ f is the density of water; V i is the volume of the particle submerged in water; g is the gravitational acceleration vector. In step (2), the water resistance F of the particle in water is d for:

[0028] F d =-6πη f R

[0029] Where η f is the dynamic viscosity of water; R is the radius of the particle; α is the ratio of the volume submerged by the particle to the total volume of the particle; v is the velocity vector of the particle.

[0030] In step (3), the velocity vector of the particle is extracted, and the velocity vector is derived at a certain time interval to obtain the movement status of each particle.

[0031] In step (3), the velocity vector of the particle is extracted and exported as the coordinate file of the sliding body particle. The specific process of obtaining the motion state of each particle is as follows:

[0032] (3.1) Traverse all particles in the particle discrete element landslide motion evolution calculation model, and create a motion state record file for each particle with the particle ID as the name;

[0033] (3.2) During the calculation process of the particle discrete element landslide movement evolution calculation model, the time step of each calculation step is recorded and accumulated as the movement time of the particles derived this time;

[0034] (3.3) When the derived time interval is reached, the movement time of the particles and the average speed of each particle in this time interval are derived;

[0035] (3.4) When the calculation of the particle discrete element landslide motion evolution calculation model does not reach the set total calculation time, return to (3.2) to continue running; when the model calculation is completed, write a termination statement in each motion state record file.

[0036] In step (3.3), when exporting the motion state of each particle, it is exported to the motion state record file of each particle generated in step (3.1) according to the ID of the particle.

[0037] In step (4.1), the mechanical parameters of the sliding body and the sliding surface are set including the cohesion between the sliding body particles, the friction coefficient, the normal and shear stiffness, and the friction coefficient between the particles and the sliding surface.

[0038] In step (5.3), the water body and the sliding surface use SPH particles with the same spacing to discretize the water body STL file, and the sliding body in the landslide surge SPH model is discretized using SPH particles according to the coordinates and diameters of each particle in the sliding body particle coordinate file.

[0039] In step (6), the method of applying a given motion form to each particle is to integrate the motion state record files of each particle obtained by the particle discrete element landslide motion evolution calculation model into one file, and import it into the SPH landslide surge calculation model.

[0040] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0041] (1) The present invention obtains the movement process of the sliding body through the particle discrete element calculation method and software, and imports the process into the SPH landslide surge calculation model to calculate the surge characteristics, thereby obtaining a landslide surge calculation result that is more in line with the actual situation, and solving the problem that the SPH method is difficult to accurately represent the movement of the landslide body due to boundary condition restrictions.

[0042] (2) The present invention can accurately consider the influence of rock and soil materials and sliding surface mechanical parameters on landslide surge, making the calculation results more realistic. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a flow chart of the SPH landslide surge simulation method based on particle discrete elements of the present invention;

[0044] Figure 2 The particle discrete element landslide motion evolution calculation model established in the embodiment of the present invention;

[0045] Figure 3 The evolution process of landslide motion using particle discrete element in the embodiment;

[0046] Figure 4 The particle sliding velocity variation curve at the center of gravity of the slider in the embodiment;

[0047] Figure 5 The SPH landslide surge calculation model established according to the particle discrete element initial model in the embodiment;

[0048] Figure 6 This is the landslide surge evolution process obtained by SPH landslide surge calculation in the embodiment. DETAILED DESCRIPTION

[0049] like Figure 1 As shown, the SPH landslide surge simulation method based on particle discrete element of the present invention includes the following steps:

[0050] (1) Establishing an initial particle discrete element model based on geological conditions; specifically including steps (1.1) to (1.2):

[0051] (1.1) Process the geological map to obtain the sliding surface, sliding body and water body;

[0052] (1.2) The sliding body and sliding surface are exported to the particle discrete element calculation software to establish a particle discrete element landslide motion evolution calculation model, in which the sliding body is discretized by particles and the sliding surface is represented by Wall.

[0053] (2) Based on the calculation method of water resistance and buoyancy of particles moving underwater, calculate the effect of water on the movement of particles; specifically:

[0054] (2.1) The buoyancy and water resistance of the particles are calculated based on the water level when the landslide is sliding down. When the particles are completely above the water surface, the buoyancy and water resistance of the particles are not considered; when the particles are completely submerged in water or half submerged in water, the buoyancy and water resistance of the particles are considered.

[0055] (2.1.1) The buoyancy F of a particle moving in water b for:

[0056] F b =-ρ f V i g

[0057] In the formula, ρ f is the density of water; V i is the volume of the particle submerged in water; g is the gravitational acceleration vector.

[0058] (2.1.2) Water resistance F of particles moving in water d for:

[0059] Fd =-6πη f R

[0060] Where η f is the dynamic viscosity of water; R is the radius of the particle; α is the ratio of the volume submerged by the particle to the total volume of the particle; v is the velocity vector of the particle.

[0061] (3) Extract the velocity vector of the particle and derive the velocity vector at a certain time interval to obtain the motion state of each particle; the specific process is as follows:

[0062] (3.1) Traverse all particles in the particle discrete element landslide motion evolution calculation model, and create a motion state record file for each particle with the particle ID as the name;

[0063] (3.2) During the calculation process of the particle discrete element landslide movement evolution calculation model, the time step of each calculation step is recorded and accumulated as the movement time of the particles derived this time;

[0064] (3.3) When the derived time interval is reached, the movement time of the particles and the average speed of each particle in this time interval are derived;

[0065] (3.4) When the calculation of the particle discrete element landslide motion evolution calculation model does not reach the set total calculation time, return to (3.2) to continue running; when the model calculation is completed, write a termination statement in each motion state record file.

[0066] In step (3.3), when exporting the motion state of each particle, it is exported to the motion state record file of each particle generated in step (3.1) according to the ID of the particle.

[0067] (4) Perform discrete element calculation of landslide motion particles to obtain the instability evolution process of the landslide; the specific process of discrete element calculation of landslide motion particles is as follows:

[0068] (4.1) Calibrate and set the mechanical parameters of the sliding body and sliding surface based on actual geological materials. The mechanical parameters include cohesion, friction coefficient, normal and shear stiffness between sliding body particles, friction coefficient between particles and sliding surface, and set the sliding surface as a fixed boundary or a dynamic boundary;

[0069] (4.2) During the calculation process, the influence of water on the particles is calculated based on the water resistance and buoyancy calculation method of the particles moving underwater;

[0070] (4.3) During the calculation process, the particle velocity is extracted and exported as a sliding particle motion velocity file;

[0071] (4.4) Set the calculation time, use the particle discrete element to simulate the landslide movement, and terminate the calculation when the landslide movement stops;

[0072] (5) The SPH landslide surge calculation model is established based on the particle discrete element initial model. The specific process is as follows:

[0073] (5.1) offsetting the sliding surface obtained in step (1.1) into a sliding surface with a certain thickness, and exporting the offset sliding surface as a sliding surface STL file; closing the water body part and exporting it as a water body STL file;

[0074] (5.2) Export the diameter and coordinates of the particles before the landslide calculation in the particle discrete element landslide motion evolution calculation model as a sliding body particle coordinate file;

[0075] (5.3) The landslide surge SPH model is established using the water body STL file, the sliding surface STL file and the sliding body particle coordinate file. The water body and the sliding surface are directly discretized using SPH particles with the same spacing on the water body STL file. The sliding body in the landslide surge SPH model is discretized using SPH particles according to the coordinates and diameters of each particle in the sliding body particle coordinate file.

[0076] (6) Setting the motion form of each particle in the sliding body part of the SPH landslide surge calculation model;

[0077] In step (6), the specific method of applying a given motion form to each particle is to integrate the particle motion state record files of each particle obtained by the particle discrete element landslide motion evolution calculation model into one file, and import it into the SPH landslide surge calculation model.

[0078] (7) Set the calculation time, gravity, and smooth length, and use the SPH landslide surge calculation model to calculate the landslide surge, obtain the landslide surge evolution process, the process of the sliding body entering the water to stir up the surge, and the surge propagation process.

[0079] Example

[0080] Taking the landslide surge generated by a certain landslide as an example, the SPH landslide surge simulation method based on particle discrete element of the present invention is introduced.

[0081] 1. First, according to the geological profile, the initial discrete element model of landslide movement evolution particles is established, and the water resistance and buoyancy of particles in underwater movement are calculated according to the calculation method of water resistance and buoyancy of particles in underwater movement. The established model is as follows Figure 2 shown.

[0082] 2. Set the mechanical parameters and boundary conditions of the sliding body and sliding surface, and calculate the movement evolution process of the landslide body. During the calculation process, calculate the influence of water on the movement of particles, and extract the movement speed of the particles and export it to the speed record file named by each particle ID. Figure 3 As shown in Figure 2, where t represents the time after the landslide starts. Figure 3 It can be seen that at t=13.0s, the landslide slid down along the sliding surface; at t=19.5s, the sliding body entered the river channel and continued to slide down; at t=39.0s, the movement of the landslide body stopped and the sliding body accumulated in the river channel.

[0083] The particle sliding velocity variation curve at the center of gravity of the sliding block is as follows: Figure 4 As shown in the figure, it can be seen that after the sliding body particles start to slide down, the speed continues to increase and reaches a peak value, and then the speed continues to decrease due to water resistance and terrain, and finally stops. Figure 4 The horizontal axis is the time after the landslide starts. Figure 4 The vertical axis is the particle sliding velocity at the center of gravity of the slider.

[0084] 3. The SPH landslide surge calculation model is established based on the initial model of landslide movement evolution particle discrete element. The established SPH landslide surge calculation model is as follows: Figure 5 As shown, the sliding body part is established by the coordinates and diameters of the particles in the initial particle discrete element model, and the sliding surface and water body are established according to the geological map.

[0085] 4. The extracted movement of each particle is imported into the SPH landslide surge calculation model as the movement process of the sliding body.

[0086] 5. Set the calculation time, gravity, and smooth length, and use the SPH landslide surge model to calculate and obtain the landslide surge evolution process, such as Figure 6 As shown. Figure 6 It can be seen that in the SPH landslide surge calculation model, the sliding body particles slide down according to the motion state calculated in the particle discrete element model, stirring up surges to propagate to the opposite bank, resulting in a large climb on the opposite bank.

Claims

1. A landslide surge simulation method based on particle discrete element and SPH, characterized by: The following steps are involved: (1) Establishing the initial particle discrete element model according to geological conditions, including steps (1.1) to (1.2): (1.1) Process the geological map to obtain the sliding surface, sliding body and water body; (1.2) Export the sliding body and sliding surface to the particle discrete element calculation software to establish the landslide movement evolution calculation model, in which the sliding body is discretized using particles and the sliding surface is represented by Wall; (2) Calculate the buoyancy F of the particles in the water based on the water level when the landslide is sliding down b and water resistance F d ; (3) Extract the velocity vector of the particle and export the velocity vector as the sliding body particle coordinate file to obtain the motion state of each particle; the process is as follows: (3.1) Traverse all particles in the particle discrete element landslide motion evolution calculation model, and create a motion state record file for each particle with the particle ID as the name; (3.2) During the calculation process of the particle discrete element landslide movement evolution calculation model, the time step of each calculation step is recorded and accumulated as the movement time of the particles derived this time; (3.3) When the derived time interval is reached, deriving the movement time of the particles and the average speed of each particle during the movement time; (3.4) When the calculation of the particle discrete element landslide motion evolution calculation model does not reach the set total calculation time, return to (3.2) to continue running; when the model calculation is completed, write a termination statement in each motion state record file; (4) Perform discrete element calculation of landslide motion particles to obtain the instability evolution process of the landslide; the specific process is as follows: (4.1) Calibrate and set the mechanical parameters of the sliding body and sliding surface according to geological materials, and set the sliding surface as a fixed boundary or a dynamic boundary; (4.2) During the calculation process, the influence of water on the particles is calculated based on the water resistance and buoyancy calculation method of the particles moving underwater; (4.3) extracting the velocity of the particles during the calculation process, and exporting the velocity as a sliding body particle motion velocity file; (4.4) Set the calculation time, use the particle discrete element to simulate the landslide movement, and terminate the simulation calculation when the landslide movement stops; (5) The SPH landslide surge calculation model is established based on the particle discrete element initial model. The specific process is as follows: (5.1) offsetting the sliding surface obtained in step (1.1) into a sliding surface with thickness, and exporting the offset sliding surface as a sliding surface STL file; closing the water body part and exporting it as a water body STL file; (5.2) Export the diameter and coordinates of the particles before the landslide calculation in the particle discrete element landslide motion evolution calculation model as a sliding body particle coordinate file; (5.3) Use the water body STL file, sliding surface STL file and sliding body particle coordinate file to establish the landslide surge SPH model; (6) Setting the motion form of each particle in the sliding body part of the SPH landslide surge calculation model; (7) Set the calculation time, gravity, and smooth length, and use the SPH landslide surge calculation model to calculate the landslide surge, obtain the landslide surge evolution process, the process of the sliding body entering the water to stir up the surge, and the surge propagation process.

2. The landslide surge simulation method based on particle discrete element and SPH according to claim 1 is characterized by: In step (2), when the particle is completely on the water surface, the buoyancy and water resistance of the particle are zero; when the particle is completely submerged in water or half submerged in water, the buoyancy and water resistance of the particle are taken into account.

3. The landslide surge simulation method based on particle discrete element and SPH according to claim 1 is characterized by: In step (2), the buoyancy F of the particle in water is b for: F b =-ρ f V i g In the formula, ρ f is the density of water; V i is the volume of the particle submerged in water; g is the gravitational acceleration vector.

4. The landslide surge simulation method based on particle discrete element and SPH according to claim 1 is characterized by: In step (2), the water resistance F of the particle in water is d for: F d =-6πι f Rav Where η f is the dynamic viscosity of water; R is the radius of the particle; α is the ratio of the volume submerged by the particle to the total volume of the particle; v is the velocity vector of the particle.

5. The landslide surge simulation method based on particle discrete element and SPH according to claim 1 is characterized by: In step (3), the velocity vector of the particle is extracted, and the velocity vector is derived at a certain time interval to obtain the movement status of each particle.

6. The landslide surge simulation method based on particle discrete element and SPH according to claim 1 is characterized by: In step (3.3), when exporting the motion state of each particle, it is exported to the motion state record file of each particle generated in step (3.1) according to the ID of the particle.

7. The landslide surge simulation method based on particle discrete element and SPH according to claim 1 is characterized by: In step (4.1), the mechanical parameters of the sliding body and the sliding surface are set including the cohesion between the sliding body particles, the friction coefficient, the normal and shear stiffness, and the friction coefficient between the particles and the sliding surface.

8. The landslide surge simulation method based on particle discrete element and SPH according to claim 1 is characterized by: In step (5.3), the water body and the sliding surface use SPH particles with the same spacing to discretize the water body STL file, and the sliding body in the landslide surge SPH model is discretized using SPH particles according to the coordinates and diameters of each particle in the sliding body particle coordinate file.

9. The landslide surge simulation method based on particle discrete element and SPH according to claim 1 is characterized by: In step (6), the method of applying a given motion form to each particle is to integrate the motion state record files of each particle obtained by the particle discrete element landslide motion evolution calculation model into one file, and import it into the SPH landslide surge calculation model.

Images