A method for simulating landslide surges in variable terrain based on DEM and water wave model

Abstract

This invention discloses a method for simulating landslide surge waves in variable terrain based on DEM and a water wave model, comprising the following steps: (1) establishing a landslide motion calculation model using the DEM method; (2) performing numerical simulation of landslide motion using the landslide motion calculation model, extracting information on all spherical particles constituting the landslide body during the calculation process; (3) constructing a surge wave evolution calculation model using a water wave model, extracting the node coordinates in the surge wave evolution calculation model as the initial terrain node coordinates; (4) reconstructing the terrain of the surge wave evolution calculation model according to the motion characteristics of the landslide body, thereby establishing the terrain that changes with the movement of the landslide body; (5) importing the terrain that changes with the movement of the landslide body into the surge wave evolution calculation model, and performing numerical simulation of surge wave evolution; (6) verifying the effectiveness of the surge wave evolution calculation model using physical model experiments. This invention solves the problem that it is difficult to consider landslide motion and deposition in a water wave model, providing a way to conduct numerical simulation of landslide surge waves.

Description

Technical Field

[0001] This invention relates to a method for simulating landslide sliding processes in the field of landslide surge research, and particularly to a method for simulating landslide surges in variable terrain based on DEM and water wave models. Background Technology

[0002] During the operation of mountain reservoirs, landslide surges induced by slope instability are a significant threat to reservoir safety. After a landslide surge occurs in a mountain reservoir, the energy dissipates slowly due to the narrow river channel. These energy-laden surges often travel for kilometers or even tens of kilometers along the river, causing widespread damage, and the entire landslide surge hazard chain spans different temporal and spatial scales. As hydropower development continues to advance into the southwestern mountainous regions, the need for assessment of landslide surge hazards in mountain reservoirs is constantly increasing.

[0003] Landslide surges mainly involve multiple processes, including the instability and sliding of the landslide mass, its deposition in the river channel, the generation of surges, their propagation along the river channel, their ascent onto the dam surface, their overtopping or reflection on the dam surface, and finally their dissipation. It is a complex chain-like geological hazard. Numerical simulation is an important tool for studying landslide surge hazards. Through coupled calculations using different methods, it is possible to accurately reflect the dynamic evolution of landslides and landslide surges.

[0004] Currently, various coupling methods such as DEM-CFD, DEM-SPH, DDA-SPH, and PD-SPH have been applied in landslide surge research and have achieved good results. However, most coupling models require significant computational resources, resulting in the computational scope being concentrated in the area near the landslide body.

[0005] For surge propagation problems involving large areas, depth integral wave models are typically used for solutions. A key issue in applying these wave models is accurately inputting the initial surge generated by a landslide entering the water: existing methods either determine the initial surge using empirical formulas and then input it into the wave model, or calculate the initial surge characteristics using a master profile model and then input the initial surge waveform at the surge generation boundary. However, these methods neglect the movement and deposition characteristics of the landslide body, potentially leading to some deviations in the calculation results.

[0006] How to adopt a landslide surge simulation method based on variable terrain, and effectively consider the complex motion characteristics of the landslide body in the water wave model, so as to provide an effective way to solve the landslide surge problem, is an urgent technical problem to be solved. Summary of the Invention

[0007] Objective: To address the shortcomings of existing technologies, this invention proposes a method for simulating landslide surge waves in variable terrain based on DEM and a water wave model. The method employs DEM to establish a landslide motion calculation model, and constructs a terrain that changes synchronously with the landslide motion within the water wave model. Based on this terrain change, surge wave evolution simulation is performed. This method solves the problem that water wave models struggle to account for the complex movements and accumulation of landslide bodies, and accurately captures the landslide motion process, providing a valuable approach for rapid and accurate landslide surge wave simulation and analysis.

[0008] Technical solution: This invention provides a method for simulating landslide surge waves in variable terrain based on DEM and water wave models, comprising the following steps:

[0009] (1) Using the DEM method, a landslide motion calculation model is established with the center of the landslide body as the center. The process is as follows: the three-dimensional sliding surface of the landslide body is established from the sliding surface of the landslide body profile and the landslide boundary at the original ground surface; after discretizing the closed space formed by the sliding surface and the original ground surface in the landslide body using spherical particles, the landslide body surface on the original ground surface is deleted, and the sliding surface of the landslide body is connected to the original ground surface to form the bottom boundary of the landslide body sliding. After fixing the bottom boundary, the bottom boundary is discretized using Wall elements.

[0010] (2) The landslide motion calculation model is used to perform numerical simulation of landslide motion until the landslide body stops moving, and the X, Y, Z coordinates and radii of the center of each spherical particle that makes up the landslide body are extracted;

[0011] (3) Based on the river topography and the sliding surface of the landslide, a wave evolution calculation model is constructed using a water wave model. The node coordinates in the wave evolution calculation model are extracted as the initial topographic node coordinates. The river boundary is set as an open boundary. The X, Y and Z coordinates of each node are extracted by traversing each node of the wave evolution calculation model.

[0012] (4) Based on the X, Y, Z coordinates and radius of the center of each sphere in the numerical simulation of landslide movement in step (2), the terrain of the surge evolution calculation model is reconstructed, and then the terrain that changes with the movement of the landslide is established.

[0013] (5) Based on the wave evolution calculation model, the topography that changes with the movement of the landslide body is imported into the water wave model for wave evolution numerical simulation and time iteration calculation is performed to extract the maximum wave height at the thalweg line in the wave evolution calculation model.

[0014] (6) Conduct a large-scale physical similarity model test of landslide surge and obtain the maximum wave height at the measuring point. Compare the maximum wave height at the measuring point with the maximum wave height at the corresponding position in the surge evolution calculation model in step (5) to verify the accuracy of the calculation results in step (5).

[0015] In step (1), the process of discretizing the closed space formed by the sliding surface and the ground surface in the landslide body using spherical particles is as follows: First, determine the particle size range of the spherical particles, then fill a region covering the space where the landslide body is located with spherical particles of the given particle size range until the porosity of the space reaches the set porosity; delete the spherical particles outside the space where the landslide body is located, and finally, take the space where the landslide body is located as the boundary to perform initial equilibrium on the spherical particles inside the space of the landslide body to form a cluster of contacting spherical particles.

[0016] In step (4), the steps for reconstructing the terrain of the surge evolution calculation model are as follows:

[0017] (4.1) Search for the X and Y coordinates of the initial terrain node of the water wave model within the vertical projection area of ​​a single spherical particle, and calculate the elevation h of the upper surface of the spherical particle relative to these X and Y coordinates. The calculation formula is as follows: ;

[0018] In the formula: This represents the elevation of the upper surface of the spherical particle relative to the X and Y coordinates. Let X be the center of the sphere. Let Y be the center of the sphere. R is the Z-coordinate of the center of the sphere; R is the radius of the sphere. The X and Y coordinates of the initial terrain nodes of the water wave model within the vertical projection area of ​​the spherical particle;

[0019] If the elevation of the upper surface of the sphere relative to the X and Y coordinates is higher than the initial terrain node Z coordinate elevation at the X and Y coordinates, then update the initial terrain node Z coordinate elevation at the X and Y coordinates using the elevation of the upper surface of the sphere relative to the X and Y coordinates; otherwise, keep the terrain node Z coordinate elevation unchanged.

[0020] (4.2) Repeat step (4.1) until all spheres have been traversed. During the traversal, if the elevation of the initial terrain node has been updated, the updated elevation of the terrain node shall be used for comparison.

[0021] (4.3) At each landslide motion calculation model, steps (4.1) and (4.2) are executed to construct the surge evolution calculation model terrain corresponding to the landslide motion at the current time. At the beginning of each update time, the initial terrain of the surge evolution calculation model is used as the basis to integrate the reconstructed surge evolution calculation model terrain at each time to form the surge evolution calculation model terrain that changes with the landslide motion.

[0022] (4.4) After the landslide stops moving, the topography of the surge evolution calculation model remains unchanged.

[0023] In step (1), after the bottom boundary is fixed, the bottom boundary is discretized using a Wall unit, the side length of which is greater than the particle size of the spherical particles.

[0024] In step (1), the sliding surfaces of each section are determined based on the engineering geological profile of the landslide body.

[0025] In step (2), the process of using a landslide motion calculation model to perform numerical simulation of landslide motion is as follows:

[0026] (2.1) The parallel bond model is used to characterize the strength and deformation characteristics of the soil and rock mass; the linear elastic model is used to characterize the friction coefficient between the landslide body and the sliding surface during the sliding process;

[0027] (2.2) Apply gravity, buoyancy and drag force to the landslide body in the landslide motion calculation model to simulate the landslide motion and obtain the process of the landslide body sliding down, deforming and disintegrating, sliding into the river channel and accumulating in the river channel.

[0028] In step (2.2), the drag force acts on the submerged ball particles in the opposite direction to the direction of the ball particles' movement. The formula for calculating the drag force is:

[0029] in, The overall drag coefficient; The density of the water body; Let be the cross-sectional area of ​​the spherical particle; Let be the sliding speed of the ball particle.

[0030] In step (2.2), the buoyancy force on the landslide body during the process of entering the water is calculated by the volume of water displaced. The volume of water displaced by the completely submerged spherical particles is equal to the volume of the spherical particles themselves; the volume of water displaced by the partially submerged spherical particles is calculated based on the volume of the spherical particles below the water surface.

[0031] In step (3), the initial topography of the surge evolution calculation model is the original topography of the river channel, and the topography at the landslide body is the sliding surface of the landslide body.

[0032] Preferably, in step (4.1), before reconstructing the terrain of the water wave model, the initial range of terrain nodes to be searched in the water wave model is first determined based on the modeling range of the landslide motion calculation model, so as to avoid searching all terrain nodes in the water wave model and causing computational redundancy.

[0033] Furthermore, in step (4.1), the KD Tree method is used to improve search efficiency during the node search process for each ball particle.

[0034] In step (5), when calculating landslide surge in the water wave model, the terrain that changes with the landslide movement is imported. Affected by the terrain change, the water level at the corresponding location will change to maintain mass conservation, thereby driving fluid movement. As the terrain continues to change, the water level also changes continuously, thus generating surge in the surge evolution calculation model and simulating the surge evolution process.

[0035] The verification method in step (6) is to verify the effectiveness of the surge evolution calculation model by comparing the maximum wave height distribution of the surge evolution calculation model and the landslide surge large-scale physical similarity model.

[0036] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0037] (1) The present invention is a landslide surge simulation method based on DEM and water wave model for variable terrain. The method uses DEM to establish a landslide motion calculation model, and considers the buoyancy and drag force of water on the landslide motion, which can accurately capture the landslide motion evolution process.

[0038] (2) The landslide surge simulation method of the present invention extracts the characteristics of landslide movement, constructs the terrain that changes synchronously with the landslide movement in the water wave model, and carries out surge evolution simulation based on the changes in the terrain, providing a reliable technical approach for carrying out numerical simulation of landslide surge. Attached Figure Description

[0039] Figure 1 This is a flowchart of the variable terrain landslide surge simulation method based on DEM and water wave model of the present invention;

[0040] Figure 2 This is a diagram of the landslide motion calculation model established in an embodiment of the present invention;

[0041] Figure 3 The landslide motion process calculated by the landslide motion calculation model in this embodiment of the invention;

[0042] Figure 4 This is a surge evolution calculation model constructed using a water wave model in an embodiment of the present invention;

[0043] Figure 5 This is the terrain reconstruction result of the surge evolution calculation model at a typical moment in the embodiments of the present invention;

[0044] in, Figure 5 (a) shows the landslide motion characteristics at a typical moment in the embodiments of the present invention;

[0045] Figure 5 (b) shows the terrain reconstruction of the surge evolution calculation model at a typical moment in the embodiment of the present invention;

[0046] Figure 6 This is the surge evolution process obtained in the embodiments of the present invention;

[0047] Figure 7 This is a verification of the surge evolution calculation model in the embodiments of the present invention. Detailed Implementation

[0048] like Figure 1 As shown, the present invention provides a method for simulating landslide surge waves in variable terrain based on DEM and water wave models, comprising the following steps:

[0049] (1) Using the DEM method, a landslide motion calculation model is established for a local area near the landslide body, with the center of the landslide body as the center. The process is as follows:

[0050] (1.1) Based on the original riverbed topography, the center of the landslide body is taken as the model center, and the modeling range ensures that the landslide body accumulation range does not exceed the model boundary when the landslide body stops moving.

[0051] (1.2) Based on the engineering geological profile of the landslide body, determine the potential sliding surface of each profile.

[0052] (1.3) Based on the potential sliding surfaces determined in each profile and the landslide boundary at the ground surface, establish the three-dimensional sliding surface of the landslide body.

[0053] (1.4) The landslide body is defined as a closed space surrounded by the sliding surface and the ground surface. Spherical particles are used to discretize this space. During discretization, the particle size range of the spherical particles is first determined. Then, spherical particles of the given size range are filled into a large area covering the landslide body space until the porosity of the space reaches the set porosity. Next, the spherical particles outside the landslide body space are deleted, retaining only those within the space. Finally, using the landslide body space as the boundary, the spherical particles inside the space are initially balanced, forming a cluster of closely contacting spherical particles, thus completing the discretization of the landslide body.

[0054] (1.5) The landslide surface on the original surface is deleted, and the sliding surface of the landslide is connected to the original surface to form the bottom boundary of the landslide, and its position is fixed. Then, the bottom boundary of the landslide is discretized using Wall elements, where the side length of the Wall element is greater than the particle size of the spherical particles.

[0055] (1.6) Integrate all the spherical particles that make up the landslide body and the discrete bottom boundary of the landslide body of the Wall unit to construct a landslide motion calculation model.

[0056] (2) A landslide motion calculation model is used to perform numerical simulation of landslide motion, taking into account the influence of water on landslide motion, and the calculation continues until the landslide body stops moving. During the simulation, information of all spherical particles that make up the landslide body is extracted, including the X, Y, and Z coordinates of the center of each spherical particle and its radius, for use in the water wave model terrain reconstruction in step 4).

[0057] In step (2), the process of using a landslide motion calculation model to perform numerical simulation of landslide motion is as follows:

[0058] (2.1) Based on the lithology of each rock layer in the landslide body, a parallel bond model was used to characterize the mechanical properties of the soil and rock mass, including strength and deformation characteristics. The calculation parameters in the parallel bond model were determined by numerical simulation inversion, integrating the results of field tests, laboratory tests, and stability analysis. The calculation parameters include parallel bond element parameters and linear elastic element parameters. A linear elastic model was used to characterize the friction coefficient between the landslide body and the sliding surface during the sliding process. This friction coefficient is taken as the residual friction coefficient.

[0059] (2.2) Apply gravity, buoyancy and drag force to the landslide body in the landslide motion calculation model to simulate the landslide motion, obtain the dynamic evolution process of the landslide body sliding down, deforming and disintegrating and sliding into the river channel and accumulating in the river channel.

[0060] The buoyancy force experienced by the landslide body during its entry into the water is calculated using the volume of water displaced. For a completely submerged spherical particle, the volume of water displaced is equal to the volume of the particle itself; when partially submerged, the volume of water displaced is calculated based on the volume of the spherical particle below the water surface.

[0061] Ideally, the drag force of the water acts as an external force on the submerged spheres, in the opposite direction to the spheres' motion. The formula for calculating the drag force is:

[0062] In the formula: The overall drag coefficient; The density of the water body; Let be the cross-sectional area of ​​the spherical particle; For speed.

[0063] (3) Based on the river channel topography and the sliding surface of the landslide in the study area, a wave evolution calculation model was constructed using a wave model. The node coordinates in the wave evolution calculation model were extracted as the initial topographic node coordinates. The river channel boundary in the wave evolution calculation model was set as an open boundary to avoid reflection of wave waves at the model boundary. The water level in the wave evolution calculation model was set to be consistent with the research requirements. By traversing each node of the wave evolution calculation model, the X, Y, and Z coordinates of each node were extracted to provide the initial topography for subsequent topographic updates.

[0064] The initial topography of the surge evolution calculation model is the original topography of the river channel in the study area, and the topography at the landslide body is the sliding surface of the landslide body.

[0065] (4) Based on the X, Y, Z coordinates and radius of the center of each sphere in the numerical simulation of landslide movement in step (2), the terrain of the surge evolution calculation model is reconstructed, and then the terrain that changes with the movement of the landslide is established.

[0066] In step (4), the step of reconstructing the terrain of the surge evolution calculation model is as follows:

[0067] (4.1) Search for the X and Y coordinates of the initial terrain node of the water wave model within the vertical projection area of ​​a single spherical particle, and calculate the elevation h of the upper surface of the spherical particle relative to these X and Y coordinates. The calculation formula is as follows: .

[0068] In the formula: This represents the elevation of the upper surface of the spherical particle relative to the X and Y coordinates. Let X, Y, and Z be the coordinates of the center of the sphere; R be the radius of the sphere. The X and Y coordinates of the initial terrain nodes of the water wave model within the vertical projection range of the spherical particles.

[0069] Then, the elevation h of the upper surface of the sphere relative to the X and Y coordinates is compared with the elevation of the initial terrain node Z coordinate at the X and Y coordinates. If the elevation h of the upper surface of the sphere relative to the X and Y coordinates is higher than the elevation of the initial terrain node Z coordinate at the X and Y coordinates, the elevation h of the upper surface of the sphere relative to the X and Y coordinates is used to update the elevation of the initial terrain node Z coordinate at the X and Y coordinates; if it is lower, the elevation of the terrain node Z coordinate remains unchanged.

[0070] (4.2) Repeat step (4.1) until all spheres have been traversed. During the traversal, if the elevation of the initial terrain node has been updated, the updated terrain node elevation is used for comparison. For terrain outside the landslide-affected area, since it is not affected by landslide movement, the initial terrain data remains unchanged.

[0071] (4.3) At each landslide motion calculation model time point, steps (4.1) and (4.2) are executed to construct the surge evolution calculation model terrain affected by landslide motion at the current time. At the beginning of each update time point, the initial terrain of the surge evolution calculation model is used as the basis. The reconstructed surge evolution calculation model terrains at each time point are integrated to form the surge evolution calculation model terrain that changes with landslide motion.

[0072] (4.4) After the landslide stops moving, the topography of the surge evolution calculation model no longer changes, and the topography reconstructed when the landslide stops remains unchanged.

[0073] Preferably, in step (4.1), before reconstructing the terrain of the water wave model, the initial range of terrain nodes to be searched in the water wave model is first determined based on the modeling area of ​​the landslide motion calculation model, so as to avoid searching all terrain nodes in the water wave model and causing a lot of computational redundancy.

[0074] Furthermore, in step (4.1), the KD Tree method is used to improve search efficiency during the node search process for each ball particle.

[0075] (5) Based on the wave evolution calculation model, the topography that changes with the movement of the landslide body is imported into the water wave model for wave evolution numerical simulation and time iteration calculation is performed to obtain the wave generation and propagation process, and the maximum wave height at the thalweg line in the wave evolution calculation model is extracted.

[0076] (6) The validity of the calculation results was verified by using a large-scale physical similarity model test of landslide surge.

[0077] The verification method involves conducting a large-scale physical model test of landslide surge waves under the same scenario. Measurement points are set up in the large-scale physical model of landslide surge waves to monitor the surge wave fluctuation process and obtain the maximum wave height at each measurement point. Then, the maximum wave height at each measurement point obtained from the large-scale physical similar model test of landslide surge waves is compared with the maximum wave height at the corresponding position in the calculation results to verify the validity of the calculation results.

[0078] Example

[0079] Taking a landslide surge in a mountainous area as an example, this invention provides an example of the variable terrain landslide surge simulation method based on DEM and water wave model.

[0080] (1) Based on the topographic features of the study area, a local area near the landslide body was selected, and a landslide motion calculation model was established using the DEM method. The river channel topography was established based on the actual topography of the study area, and the sliding surface was obtained from the potential sliding surfaces in each landslide body profile. The established landslide motion calculation model is as follows: Figure 2 As shown, the landslide mass was discretized using spherical particles with an average diameter of 3 μm, forming a landslide mass of 60,131 spherical particles. Based on the mechanical properties of each rock layer and the sliding surface within the landslide mass, mechanical parameters of the soil and rock mass and the sliding surface were assigned values. The influence of water on landslide movement was considered.

[0081] (2) Numerical simulation of landslide movement is performed using a landslide motion calculation model to obtain the landslide motion evolution process, such as... Figure 3As shown, the landslide started from a static state and slid down the sliding surface, with the sliding velocity at the rear edge significantly greater than that at the front edge (t=15 s). Subsequently, the landslide slid into the river channel, and the sliding velocity gradually decreased (t=25 s). At t=100 s, the landslide stopped moving and accumulated in the river channel. Information on all the spherical particles that constituted the landslide during its movement was extracted, including the X, Y, and Z coordinates of the center of each particle and its radius, to reconstruct the topography of the water wave model.

[0082] (3) Based on the river channel topography and the sliding surface of the landslide in the study area, a wave evolution calculation model is constructed using a water wave model, such as... Figure 4 The upstream boundary of the surge evolution calculation model is an open boundary to avoid reflection of surge waves at the boundary. The downstream boundary is a dam, a water-retaining structure. The node coordinates in the surge evolution calculation model are extracted as the initial terrain node coordinates to provide initial terrain for subsequent terrain updates.

[0083] (4) Based on the movement characteristics of the landslide, the topography of the surge evolution calculation model is reconstructed, and the topography that changes with the movement of the landslide is established. The topography reconstruction of the surge evolution calculation model at typical moments is as follows: Figure 5 Extract information about all spheres at the current moment, including the X, Y, and Z coordinates of each sphere's center and its radius. Figure 5 (a)). The elevations of each node in the surge evolution calculation model are then updated using information from each individual sphere, while the topography remains unchanged outside the landslide-affected area. Figure 5 (b)).

[0084] (5) Import the terrain that changes with the movement of the landslide body into the surge evolution calculation model, set the water level to be the same as the research water level, and conduct numerical simulation of surge evolution to obtain the spatiotemporal evolution process of the surge, as follows: Figure 6 Influenced by topographic changes in the water wave model, the water body begins to move (t=10 s). Under the continuous influence of topographic changes, swells gradually emerge in the wave evolution calculation model and propagate in an arc towards the opposite bank and upstream and downstream (t=20 s). Subsequently, the swells continue to propagate along the river channel after their formation (t=60 s), reaching the dam at approximately t=190 s.

[0085] (6) Extract the maximum wave height at the thalweg line in the wave evolution calculation model and compare it with the physical model test results of the large-scale physical similarity model test of landslide waves to verify the validity of the calculation results, such as... Figure 7 It can be seen that the numerical calculation results are highly consistent with the physical model test results, proving the validity of the calculation results.

Claims

1. A method for simulating landslide surge waves in variable terrain based on DEM and water wave model, characterized in that: Includes the following steps: (1) Using the DEM method, a landslide motion calculation model is established with the center of the landslide body as the center. The process is as follows: the three-dimensional sliding surface of the landslide body is established from the sliding surface of the landslide body profile and the landslide boundary at the original ground surface; after discretizing the closed space formed by the sliding surface and the original ground surface in the landslide body using spherical particles, the landslide body surface on the original ground surface is deleted, and the sliding surface of the landslide body is connected to the original ground surface to form the bottom boundary of the landslide body sliding. After fixing the bottom boundary, the bottom boundary is discretized using Wall elements. (2) The landslide motion calculation model is used to perform numerical simulation of landslide motion until the landslide body stops moving, and the X, Y, Z coordinates and radii of the center of each spherical particle that makes up the landslide body are extracted; (3) Based on the river topography and the sliding surface of the landslide, a wave evolution calculation model is constructed using a water wave model. The node coordinates in the wave evolution calculation model are extracted as the initial topographic node coordinates. The river boundary is set as an open boundary. The X, Y and Z coordinates of each node are extracted by traversing each node of the wave evolution calculation model. (4) Based on the X, Y, Z coordinates and radius of the center of each sphere in the numerical simulation of landslide movement in step (2), the terrain of the surge evolution calculation model is reconstructed, and then the terrain that changes with the movement of the landslide is established. (5) Based on the wave evolution calculation model, the topography that changes with the movement of the landslide body is imported into the water wave model for wave evolution numerical simulation and time iteration calculation is performed to extract the maximum wave height at the thalweg line in the wave evolution calculation model. (6) Conduct a large-scale physical similarity model test of landslide surge and obtain the maximum wave height at the measuring point. Compare the maximum wave height at the measuring point with the maximum wave height at the corresponding position in the surge evolution calculation model in step (5) to verify the accuracy of the calculation results in step (5).

2. The method for simulating landslide surge waves in variable terrain based on DEM and water wave model according to claim 1, characterized in that: In step (1), the process of discretizing the closed space formed by the sliding surface and the ground surface in the landslide body using spherical particles is as follows: First, determine the particle size range of the spherical particles, then fill a region covering the space where the landslide body is located with spherical particles of the given particle size range until the porosity of the space reaches the set porosity; delete the spherical particles outside the space where the landslide body is located, and finally, take the space where the landslide body is located as the boundary to perform initial equilibrium on the spherical particles inside the space of the landslide body to form a cluster of contacting spherical particles.

3. The method for simulating landslide surge waves in variable terrain based on DEM and water wave model according to claim 1, characterized in that: In step (4), the steps for reconstructing the terrain of the surge evolution calculation model are as follows: (4.1) Search for the X and Y coordinates of the initial terrain node of the water wave model within the vertical projection area of ​​a single spherical particle, and calculate the elevation h of the upper surface of the spherical particle relative to these X and Y coordinates. The calculation formula is as follows: ; In the formula: This represents the elevation of the upper surface of the spherical particle relative to the X and Y coordinates. Let X be the center of the sphere. Let Y be the center of the sphere. R is the Z-coordinate of the center of the sphere; R is the radius of the sphere. The X and Y coordinates of the initial terrain nodes of the water wave model within the vertical projection area of ​​the spherical particle; If the elevation of the upper surface of the sphere relative to the X and Y coordinates is higher than the initial terrain node Z coordinate elevation at the X and Y coordinates, then update the initial terrain node Z coordinate elevation at the X and Y coordinates using the elevation of the upper surface of the sphere relative to the X and Y coordinates; otherwise, keep the terrain node Z coordinate elevation unchanged. (4.2) Repeat step (4.1) until all spheres have been traversed. During the traversal, if the elevation of the initial terrain node has been updated, the updated elevation of the terrain node shall be used for comparison. (4.3) At each landslide motion calculation model, steps (4.1) and (4.2) are executed to construct the surge evolution calculation model terrain corresponding to the landslide motion at the current time. At the beginning of each update time, the initial terrain of the surge evolution calculation model is used as the basis to integrate the reconstructed surge evolution calculation model terrain at each time to form the surge evolution calculation model terrain that changes with the landslide motion. (4.4) After the landslide stops moving, the topography of the surge evolution calculation model remains unchanged.

4. The method for simulating landslide surge waves in variable terrain based on DEM and water wave model according to claim 1, characterized in that: In step (1), after the bottom boundary is fixed, the bottom boundary is discretized using a Wall unit, the side length of which is greater than the particle size of the spherical particles.

5. The method for simulating landslide surge waves in variable terrain based on DEM and water wave model according to claim 1, characterized in that: In step (1), the sliding surfaces of each section are determined based on the engineering geological profile of the landslide body.

6. The method for simulating landslide surge waves in variable terrain based on DEM and water wave model according to claim 1, characterized in that: In step (2), the process of using a landslide motion calculation model to perform numerical simulation of landslide motion is as follows: (2.1) The parallel bond model is used to characterize the strength and deformation characteristics of the soil and rock mass; A linear elastic model was used to characterize the friction coefficient between the landslide body and the sliding surface during the sliding process; (2.2) Apply gravity, buoyancy and drag force to the landslide body in the landslide motion calculation model to simulate the landslide motion and obtain the process of the landslide body sliding down, deforming and disintegrating, sliding into the river channel and accumulating in the river channel.

7. The method for simulating landslide surge waves in variable terrain based on DEM and water wave model according to claim 6, characterized in that: In step (2.2), the drag force acts on the submerged ball particles in the opposite direction to the direction of the ball particles' movement. The formula for calculating the drag force is: ; in, The overall drag coefficient; Density of water; Let be the cross-sectional area of ​​the spherical particle; Let be the sliding speed of the ball particle.

8. The method for simulating landslide surge waves in variable terrain based on DEM and water wave model according to claim 6, characterized in that: In step (2.2), the buoyancy force on the landslide body during the process of entering the water is calculated by the volume of water displaced. The volume of water displaced by the completely submerged spherical particles is equal to the volume of the spherical particles themselves; the volume of water displaced by the partially submerged spherical particles is calculated based on the volume of the spherical particles below the water surface.

9. The method for simulating landslide surge waves in variable terrain based on DEM and water wave model according to claim 1, characterized in that: In step (3), the initial topography of the surge evolution calculation model is the original topography of the river channel, and the topography at the landslide body is the sliding surface of the landslide body.

10. The method for simulating landslide surge waves in variable terrain based on DEM and water wave model according to claim 3, characterized in that: In step (4.1), the KD Tree method is used to perform node search on the sphere particles.

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