Analysis method of landslide disaster-causing effect considering three-dimensional stability and finite difference

Abstract

The application is a landslide disaster-causing effect analysis method considering three-dimensional stability and finite difference, through FSLAM real-time calculation of groundwater level change under event rainfall, interaction with the stability analysis module, realizing closed-loop feedback of rainfall infiltration-stability coefficient-motion simulation; taking the stability coefficient as the strength reduction factor of Massflow input to dynamically adjust the material parameters, realizing full-chain analysis from instability judgment to motion simulation. Through the use of high-resolution DEM data, the sliding surface search range can be dynamically defined, supporting the modeling of non-circular surfaces and accurately capturing irregular geometric shapes. The limitations of simplifying the landslide geometry and soil mechanical properties in traditional two-dimensional analysis are overcome, the complex mechanical behavior in the landslide instability process is more accurately captured, and the reliability of stability calculation is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of engineering geology, and particularly relates to a landslide disaster-causing effect analysis method and system considering three-dimensional stability and finite difference. BACKGROUND

[0002] Landslide disaster is a common and serious geological disaster, widely distributed in various landforms around the world, especially in mountainous, hilly and coastal steep slope areas. The occurrence of landslide is often influenced by natural factors and human activities, such as heavy rainfall, earthquake, volcanic activity, river erosion and unreasonable engineering construction. As a sudden and destructive geological phenomenon, landslide not only threatens human life and property safety, but also may trigger secondary disasters such as debris flow and barrier lake, thereby exacerbating the chain effect of disasters. Due to the characteristics of concealment, suddenness and complexity, the prediction and prevention of landslide face great challenges. Therefore, scientific understanding of the mechanism of landslide occurrence, accurate assessment of landslide risk, and development of reasonable prevention measures are important tasks to mitigate the impact of landslide disaster and ensure the sustainable development of social economy.

[0003] However, most of the traditional landslide analysis methods are based on two-dimensional model, which cannot accurately consider the three-dimensional spatial characteristics and geological structure of landslide body. In actual situation, the shape and geological condition of landslide body are often complex, and the two-dimensional analysis method is difficult to accurately simulate the deformation and failure process of landslide body, resulting in low accuracy and reliability of the analysis results. The existing three-dimensional landslide stability analysis method such as the method of Sun Benbo et al. in “A landslide hazard assessment and prediction method under rainfall condition in reservoir area” simplifies the sliding surface by using spherical surface cutting method, but the actual landslide slope terrain is complex, and there are irregular geometric characteristics (such as multi-stage landslide, steep terrain), which leads to large errors in moment balance analysis and Bishop method under complex geological conditions. For example, the spherical surface cutting cannot accurately reflect the spatial distribution of the actual sliding surface, and the sensitivity to the mechanical parameters of non-homogeneous rock-soil body is insufficient. In the method of Zhou Lin et al. in “Landslide stability analysis method based on Morgenstern-Price method”, the steady or transient seepage model is used to calculate the pore water pressure, and the cumulative effect of rainfall infiltration is ignored, such as the influence of previous rainfall on groundwater level.

[0004] In view of the limitations of two-dimensional analysis of landslide and the deficiencies of the existing stability analysis methods, the present application provides a landslide disaster-causing effect analysis method and system considering three-dimensional stability and finite difference. SUMMARY

[0005] In view of the deficiencies of the prior art, the technical problem to be solved by the present application is to provide a landslide disaster-causing effect analysis method and system considering three-dimensional stability and finite difference.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0007] In a first aspect, the present application provides a landslide disaster-causing effect analysis method considering three-dimensional stability and finite difference, which comprises the following steps:

[0008] S1, obtaining the relevant information of the landslide by using satellite remote sensing technology, ground sensor network or public meteorological database, wherein the relevant information of the landslide includes landslide watershed range, landslide soil information, landslide rainfall data, digital elevation model DEM, and soil property parameters; the soil property parameters include density, porosity, cohesion, friction angle, unit weight, basal friction coefficient, pore water pressure, runoff curve number, and average saturation;

[0009] S2, importing the DEM into GIS software, and calculating the initial groundwater level height h a and the groundwater level height h a after the event rainfall under the cumulative rainfall of each grid e ; wherein,

[0010]

[0011] In the formula, h e is the change height of the groundwater level after the event rainfall; CN is the runoff curve number; P e is the event rainfall; n f is the fillable porosity, n f =n·(1-S r ), n is the porosity, and S r is the average saturation of the entire depth before the event rainfall;

[0012] S3, taking (h a , h a +h e ) as the elevation range, and based on the DEM data and the landslide boundary of the research area, the spatial range in which the sliding surface is possibly distributed is determined, the sliding surface search range is set for each grid according to the elevation range and the spatial range in which the sliding surface is possibly distributed, the distance from h a to the slope surface is taken as the maximum depth, and h a +h eThe distance to the slope surface is taken as the minimum depth, and then the depth range of the sliding surface is set for each grid. Each sliding surface search range is considered as a sliding body. Then, the stability coefficients of all sliding bodies in the analyzed landslide are calculated respectively to obtain the landslide stability coefficient distribution map, the sliding body volume file, and the ratio file of the sliding body volume and area.

[0013] S4, importing the digital elevation model DEM into the Massflow software, constructing a three-dimensional model of the landslide in the sliding surface search range, taking the sliding body volume output in step S3 as the volume of the sliding source area, and taking the ratio of the sliding body volume and area output in step S3 as the average depth of the sliding body, and dynamically reducing the mechanical parameters of the sliding body by using the landslide stability coefficient obtained in step S3, and directly using the mechanical parameters of the sliding body after strength reduction for landslide motion numerical simulation to obtain the landslide influence range, velocity and flow depth, and to evaluate various disaster effects that may be caused by the landslide.

[0014] Further, the calculation formula of the stability coefficient Fs is:

[0015]

[0016] wherein e i，j is the horizontal seismic force arm of the grid column, the value of which is the vertical distance from the centroid of the grid column to the elevation of the rotation axis, G i，j is the gravity of the grid column, k i，j is the horizontal seismic coefficient, a i,j is the force arm of the grid column in the direction of gravity, the value of which is the horizontal distance from the rotation axis to the centroid of the grid column, A i，j is the potential sliding surface area of the grid column located in the i-th row and j-th column, S i，j is the distance from the bottom surface of the grid column to the rotation axis, α i,j is the apparent inclination angle of the bottom surface of the grid column in the sliding direction, σ i，j is the normal stress of the grid column in the i-th row and j-th column, c i，j and are the shear strength parameters of the sliding surface of the grid column in the i-th row and j-th column, u i，j is the pore water pressure.

[0017] Further, the calculation formula of the stability coefficient Fs is simplified by using the Fellenius method and the Bishop simplified method respectively, and any one of the simplified formulas is taken as the basis for determining the landslide stability coefficient distribution map.

[0018] Further, when the DEM data based on the research area and the landslide boundary demarcate the spatial range where the sliding surface is possibly distributed, if the terrain feature is a steep region with a slope greater than 30°, the spatial search range is reduced, and if the terrain feature is a gentle region with a slope not greater than 30°, the search range is expanded, so as to determine the spatial range where the sliding surface is possibly distributed.

[0019] In a second aspect, the present application provides a landslide disaster-causing effect analysis system considering three-dimensional stability and finite difference, which comprises:

[0020] A database module is configured to store the information related to the landslide, including the landslide basin range, landslide soil information, landslide rainfall data, digital elevation model DEM, and soil attribute parameters.

[0021] A groundwater level calculation module is configured to calculate the initial groundwater level height under the cumulative rainfall based on the steady-state recharge and the contributing area of the catchment by using the fast shallow landslide assessment model FSLAM, and then calculate the groundwater level change height after the event rainfall by using the event rainfall and the runoff curve, so as to obtain the groundwater level height h after the event rainfall of the landslide to be analyzed. a +h e ;

[0022] A stability analysis module is configured to simplify the stability coefficient formula based on the Bishop simplified method or the Fellenius method, calculate the stability coefficient by using the simplified formula, and analyze the landslide stability to determine the sliding body volume and the ratio of the sliding body volume to the area.

[0023] A three-dimensional numerical simulation module is configured to use the Massflow software to numerically simulate the landslide movement.

[0024] A result analysis module is configured to analyze the landslide disaster-causing effect based on the landslide movement range, speed, and depth map under different working conditions obtained by the three-dimensional numerical simulation module.

[0025] The FSLAM is used to calculate the groundwater level change under the event rainfall in real time, and the stability analysis module is interacted with, so as to realize the closed-loop feedback of the rainfall infiltration-stability coefficient-movement simulation. The stability coefficient is used as the strength reduction factor of the Massflow input to dynamically adjust the material parameters, so as to realize the whole-chain analysis from the instability judgment to the movement simulation.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] (1) The present application can dynamically define the search range of the sliding surface by using high-resolution DEM data, and can support the modeling of non-circular surfaces (such as polyline or multi-stage sliding surfaces), and can accurately capture irregular geometric shapes (such as multi-stage landslides or steep terrain changes). It overcomes the limitations of traditional two-dimensional analysis on the simplification of landslide geometry and soil mechanical properties, more accurately captures the complex mechanical behavior in the landslide instability process, and improves the reliability of stability calculation. It supports accurate modeling and dynamic analysis of various types of landslides, including landslides with high width / depth ratio or non-homogeneous strata, and has strong adaptability.

[0028] (2) The present application uses the finite difference method (such as Massflow software) to model the three-dimensional dynamics of the slope, simulates the dynamic evolution process of stress and displacement field in the landslide body, and can effectively capture the whole process from the initial instability to large-scale movement of the landslide, thereby improving the accuracy of stress and displacement analysis, having high numerical stability and flexibility, and being suitable for landslide dynamics research under multi-field coupling conditions (such as rainfall infiltration and earthquake action). By combining the strength reduction method to dynamically adjust the rock and soil parameters, the errors caused by simplification are reduced and the prediction of slope stability is improved.

[0029] (3) The present application uses high-resolution digital elevation model (DEM) data and combines terrain parameters to dynamically adjust the search range of the sliding surface. For example, if the terrain feature within the landslide boundary is a steep area with a slope greater than 30°, the spatial search range is reduced, and if the terrain feature is a gentle area with a slope not greater than 30°, the search range is expanded, thereby determining the spatial range where the sliding surface may be distributed. This flexibility is crucial for accurately modeling various types of landslides, especially those with irregular geometric shapes (such as multi-stage landslides or steep terrain), ensuring that the model can adapt to the unique characteristics of each slope. At the same time, the finite difference method of Massflow software can be used to simulate the three-dimensional dynamics of the landslide, including stress distribution and displacement field. This is crucial for capturing the behavior of landslides with complex soil layers, non-homogeneous materials, or different boundary conditions (such as steep slopes, etc.). Finally, through strength reduction, rock and soil parameters such as cohesion and friction angle can be dynamically adjusted during simulation. This dynamic adjustment makes the model more adaptable and accurate when dealing with landslides with different rock and soil conditions, and can meet the analysis needs of various types of landslides.

[0030] (4) The present application realizes the dynamic real-time simulation of the whole landslide process from instability to large-scale movement. It directly couples external factors such as rainfall and seismic activity with landslide dynamics, realizes a complete feedback loop of stress, displacement and external influence, and ensures a more comprehensive understanding of the disaster process, and can completely simulate the movement of the landslide from start to finish.

[0031] (5) The present application considers the dynamic cumulative effect of rainfall infiltration by combining topography, soil mechanical parameters and hydrological conditions, calculates the groundwater level change before and after rainfall in real time through the FSLAM model, and dynamically changes the pore water pressure with event rainfall. The value of the stability coefficient is dynamically calculated and updated based on the water level change each time, which can accurately evaluate the various disaster effects that may be caused by landslides, such as landslide volume, movement path, and impact range, providing a scientific basis for landslide disaster risk management and emergency decision-making. The output results include three-dimensional landslide distribution map, stability coefficient distribution, landslide volume and downstream impact prediction, etc., which have intuitive and practicality. According to the rainfall event, the total rainfall is updated in real time, i.e. the event rainfall P e , dynamically calculates h e , and reflects the influence of previous rainfall on soil saturation through S r . For example, the previous rainfall causes S r to rise and n f to decrease, thereby amplifying the correction amplitude of h e to the height of groundwater level change.

[0032] (6) The present application dynamically defines the search range of the sliding surface through high-resolution DEM data, and combines the finite difference method (Massflow software) to perform grid-by-grid mechanical analysis on the three-dimensional sliding surface, fully considering the dynamic cumulative effect of rainfall infiltration (such as the influence of previous rainfall on groundwater level), realizing the real-time interaction of hydrological conditions and mechanical analysis, dynamically adjusting the rock-soil parameters through strength reduction method, and simulating the gradual change process of landslide from stability to instability.

[0033] In summary, the method and system of the present application integrate advanced three-dimensional stability analysis and finite difference calculation technology, making up for the shortcomings of traditional landslide analysis methods, significantly improving the accuracy and efficiency of landslide disaster effect analysis, and providing strong technical support for landslide prevention and disaster management. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is the flow depth diagram of the Gouhebeilandslide in Example 1 of the present application under 50-year return period.

[0035] Figure 2 is the velocity diagram of the Gouhebeilandslide in Example 1 of the present application under 50-year return period. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application will be further described in detail below in combination with the drawings and examples. Of course, the specific examples described here are only used to explain the present application, and are not used to limit the present application.

[0037] The present application is a landslide disaster effect analysis method considering three-dimensional stability and finite difference, comprising the following steps:

[0038] S1. Obtain relevant information about the landslide by using satellite remote sensing technology, ground sensor networks, or publicly available meteorological databases. The relevant information about the landslide includes the landslide watershed range, landslide soil information, landslide rainfall data, digital elevation model (DEM), and soil property parameters (such as density, porosity, cohesion, friction angle, unit weight, base friction coefficient, pore water pressure, number of runoff curves, and average saturation).

[0039] S2. Import the DEM into the GIS software and calculate the groundwater level height after rainfall for each raster of the landslide event to be analyzed.

[0040] The groundwater level module calculates the initial groundwater level before rainfall based on the Fast Shallow Landslide Assessment Model (FSLAM) using steady-state recharge and catchment area, and then calculates the groundwater level change h after the rainfall event using event rainfall and runoff curves. e Finally, the groundwater level h after rainfall following the landslide event to be analyzed was obtained. a +=h e .

[0041] The Fast Shallow Landslide Assessment Model (FSLAM) is based on the infinite slope theory and determines the pore water pressure distribution in the soil by combining lateral (previous conditions) and longitudinal (event rainfall) flow characteristics. FSLAM uses a steady-state recharge q... a and the area contributed by the water catchment ( a ) as input parameters, Used to calculate the initial groundwater level h under the cumulative rainfall for each grid cell. a This means that the water level height from the base of the soil column is influenced by prerequisite conditions. This process reflects the combined effects of previous accumulated rainfall, topographic features, and soil permeability on the groundwater dynamics, providing important initial hydrological conditions for landslide stability analysis. The initial groundwater level h under accumulated rainfall for each grid cell is shown below. a The calculation formula is as follows:

[0042]

[0043] In the formula K s θ is the saturated permeability coefficient, b is the grid size, and θ is the slope.

[0044] During the event rainfall, the surface runoff is determined by using the runoff curve number (CN), which is a simple hydrological model that takes into account the land use and land cover (LULC) and soil type. The event rainfall-induced groundwater level change height is calculated according to the following formula in combination with the event rainfall and the runoff curve number:

[0045]

[0046] where h e is the rise of the groundwater level during the rainfall, i.e., the event rainfall-induced groundwater level change height; CN is the runoff curve number, which is only related to the vegetation type, and the CN value is different for different vegetation types; P e is the event rainfall, n f is the fillable porosity,

[0047] The expression of the fillable porosity n f is:

[0048] n f = n·(1-S r )

[0049] where n is the porosity, S r is the average saturation of the entire depth before the event rainfall, i.e., the average saturation during the previous cumulative rainfall, and S r reflects the influence of the previous cumulative rainfall on the soil saturation, and is obtained by monitoring with soil temperature and humidity sensors arranged in a number of profiles along the landslide, and dynamically changes with the event rainfall process Sr.

[0050] Further, h a +h e is the groundwater level height after the event rainfall of the landslide.

[0051] S3, calculate the stability coefficients of all sliding bodies in the landslide in the GIS software:

[0052] (h a , h a +h e ) as the elevation range, and based on the DEM data and the landslide boundary of the study area, the spatial range of the possible distribution of the sliding surface is determined, the search range of the sliding surface is set for each grid according to the elevation range of each grid and the spatial range of the possible distribution of the sliding surface, the distance from h a to the slope surface is taken as the maximum depth, and h a +h eThe distance to the slope surface is taken as the minimum depth, and then the depth range of the sliding surface is set for each grid. Each sliding surface search range is considered as a sliding body. Then, the stability coefficient of all sliding bodies in the landslide to be analyzed is calculated respectively to obtain the landslide stability coefficient distribution map, the sliding body volume file, and the ratio file of sliding body volume and area. The specific process is as follows:

[0053] (1) Prepare the high-resolution DEM file of the study area, and preprocess the DEM in GIS software (such as ArcGIS or QGIS) to fill in the invalid data in the DEM, repair possible boundary abnormalities, ensure data integrity, crop the DEM to the study area range, and reduce the amount of calculation.

[0054] (2) Import the DEM file as the basic terrain data, check whether the DEM data is loaded correctly, and ensure that the displayed terrain range is consistent with the study area. Secondly, set the DEM cell size, which is usually consistent with the DEM file resolution. Finally, define the analysis area range (such as the landslide boundary). In these two steps, filling is to repair data content defects in order to ensure the accuracy of the analysis results; checking is to verify whether the data is correctly displayed in the GIS software to avoid calculation simulation errors.

[0055] (3) Define the material model and set the soil property parameters of the landslide, including cohesion, friction angle, unit weight, etc. If there is significant soil layering in the area, define the properties of each layer of material, make the soil property parameters of each layer of material as a layered material file, and input through the layered material file.

[0056] (4) Input the initial groundwater level height h a and the groundwater level height h a +h e after rainfall of the landslide, take (h a , = h a +h e ) as the elevation range, and based on the DEM data and landslide boundary of the study area, define the spatial range of the possible distribution of the sliding surface, set the sliding surface search range for each grid according to the elevation range of each grid and the spatial range of the possible distribution of the sliding surface, take the distance from h a to the slope surface as the maximum depth, and take h a +h eThe distance to the slope surface is taken as the minimum depth, and then the depth range of the sliding surface is set for each grid. By setting the maximum and minimum depths, the system only performs mechanical analysis on the soil in the selected depth range, avoiding invalid calculations. Each search range of the sliding surface is considered as a sliding body. The sliding source area and average depth input by the Massflow software directly depend on the depth range of the sliding surface set in this step. The sliding body volume calculation only covers the soil within this depth. The sliding surface volume range can also be set to about 0.01 to 10,000 cubic meters, limiting the possible landslide size in the calculation area.

[0057] (5) Stability analysis of the landslide to be analyzed:

[0058] When calculating the stability coefficient, the moment balance method is used for calculation. The ordinary Fellenius method and the simplified Bishop method are mainly used. In general, all limit equilibrium methods (including the moment balance method) will F S defined as the average shear strength τ f ratio of the shear stress τ along the sliding direction of the sliding surface:

[0059]

[0060] When the sliding body is in a state of limit equilibrium, it is assumed that the F S of each grid column in the disaster reduction sliding body is the same, and the average downward force T is the sum of the downward forces of all grid columns corresponding to the row number i and column number j in the x and y directions, i.e.

[0061]

[0062] In the formula, A is the total surface area of the potential sliding surface; A i，j is the potential sliding surface area of the grid column located in the i row and j column.

[0063] The force arm a i,j of each grid column in the gravity direction is the horizontal distance from the rotation axis to the centroid (approximately the geometric center) of the column, which can be obtained from the geometric relationship:

[0064] a i,j = S i,j sin α i,j

[0065] In the formula, S i，j is the distance from the bottom surface of the grid column to the rotation axis, which changes with the column. In two dimensions, the value is the radius of the circle; αi,j is the apparent inclination angle of the column bottom surface in the sliding direction.

[0066] Therefore, the rotation moment M dG , M dEQrespectively are:

[0067] M dG =∑S i,j G i,j sinα i,j

[0068] M dEQ =∑G i,j k i,j e i,j

[0069] In the formula, e i，j is the horizontal seismic force arm of the grid column, the value is the vertical distance from the centroid of the grid column to the elevation of the rotation axis, G i，j is the gravity of the grid column, and k i，j is the horizontal seismic coefficient.

[0070] The anti-rotation moment is the sum of the product of the shear strength of the bottom of all grid columns and the anti-rotation arm, and the total anti-rotation moment M r of all grid columns is:

[0071]

[0072] In the formula, σ i，j is the normal stress of the grid column in the ith row and jth column; c i，j and are the shear strength parameters of the sliding surface of the grid column in the ith row and jth column, and u i，j is the pore water pressure.

[0073] Therefore, the stability factor F S of the potential sliding body is:

[0074]

[0075] Fellenius method and Bishop simplified method use different normal pressure calculation methods to evaluate the stability of landslide, and the stability calculation formula is simplified by using Fellenius method and Bishop simplified method respectively, and after simplification, they are:

[0076]

[0077] Where, β i，j is the inclination angle of the potential sliding surface of the grid column in the ith row and jth column, and k eq is the equivalent seismic coefficient.

[0078] (6) Output the landslide stability coefficient distribution map and the file of the volume of the sliding body, and the file of the ratio of the volume to the area of the sliding body. In the landslide stability coefficient distribution map, the distribution state of a piece by piece can be presented, and each piece can be considered as a sliding body. The stability coefficient calculated above is the stability coefficient of a sliding body.

[0079] S4, import the digital elevation model DEM into the Massflow software, generate the Massflow landslide model, search the sliding surface in the range, and use the landslide stability coefficient obtained in S3 to dynamically reduce the mechanical parameters of the sliding body, and directly use the mechanical parameters of the sliding body after strength reduction for landslide numerical simulation, obtain the landslide influence range, speed and flow depth, and use them to evaluate the various disaster effects that may be caused by the landslide. The specific steps are as follows:

[0080] (1) Obtain and process the digital elevation model DEM data: In step S3, the DEM data is cut by using the ArcGIS software, irrelevant or irrelevant areas are removed, and the data is optimized to ensure the accuracy and calculation efficiency of the model. This step converts the DEM data into the projection coordinate format that can be accepted by AutoCAD based on the data in step S3, converts these data into ASCII format files, and names the basic terrain data and the spatial distribution information of the landslide source area required for landslide modeling as m.txt and s.txt respectively, so that the processed data can be effectively recognized by modeling software such as Massflow. Then, these ASCII format files are imported into the Massflow software for further processing.

[0081] (2) In the Massflow software, input the volume of the source area (i.e. the total amount of landslide material) and the average depth of the landslide. The volume is the volume of the sliding body output in step S3, and the average depth is the ratio of the volume to the area of the sliding body output in step S3. After completing these preliminary settings, run the Landslide Volume.exe program, and the Massflow software will generate the final terrain elevation z and fluid height h files according to the input landslide area data (volume and average depth).

[0082] (3) Three-dimensional modeling of the landslide. The complete three-dimensional model of the landslide is generated directly according to the z and h files. The z file is assigned as terrain data, and the h file represents the height of the fluid in the landslide process.

[0083] (4) Set the model material parameters. In the Massflow software, select the Coulomb model and set the material parameters, including density, cohesion, and base friction coefficient, etc. These parameters need to be strength-reduced using the stability factor output in step S3 when setting. The mechanical parameters of the landslide body after strength reduction are directly used for numerical simulation of landslide movement, and static-dynamic coupling analysis is realized. Through the parameter reduction mechanism, the stability analysis and movement simulation are integrated into a unified process, improving the accuracy and efficiency of landslide disaster effect analysis.

[0084] (5) Perform dynamic numerical simulation of the landslide movement, output the landslide influence range and velocity, and flow depth files. Finally, according to the output files, the various disaster effects that may be caused by the landslide can be accurately evaluated, providing a scientific basis for landslide disaster risk management and emergency decision-making.

[0085] Example 1

[0086] The research example is the Gouhebei landslide, which is located in Gouhebei Village, Guanzhuang Town, Jizhou District, Tianjin, China. For the Gouhebei landslide, rainfall is the most important factor that triggers landslide instability, so it is necessary to analyze extreme rainfall scenarios to predict the potential stability and danger of the landslide in advance.

[0087] Step S1: Obtain the landslide digital elevation model (DEM), soil property parameters, and landslide rainfall data, such as saturated permeability coefficient, porosity, cohesion, and friction angle, from the system database module. The rainfall is divided into 50-year and 100-year return period rainfall, with values of 130 mm / day and 150 mm / day, respectively.

[0088] In the groundwater level calculation module, the steady-state recharge q a , the contributing area ( a ), saturated permeability coefficient K s , and the grid size b and slope θ are used to calculate the change in groundwater level height of the landslide under different event rainfall conditions.

[0089] Step S2: Process the terrain data obtained in step S1 using ArcGIS, import the digital elevation model (DEM) into the stability analysis module, and ensure that the displayed terrain range is consistent with the study area. Set the DEM cell size to 0.5 m, define the landslide boundary, and define the material model.

[0090] Step S3: The groundwater level change heights calculated by the groundwater level module under two working conditions of rainfall with a 50-year return period and rainfall with a 100-year return period are set to the stability analysis module, and stability analysis is performed in the stability analysis module. The stability coefficient of the landslide under the condition of rainfall with a 50-year return period is 0.957, and the stability coefficient of the landslide under the condition of rainfall with a 100-year return period is 0.939.

[0091] Step S4: The terrain data obtained in step S1 is processed by ArcGIS to determine the scope of the sliding source area of the landslide occurrence area, and a corresponding terrain file is generated according to the terrain features of the area. These data are converted into ASCII format files and named as m.txt and s.txt respectively. These files contain basic terrain data and spatial distribution information of the landslide source area required for landslide modeling. Then, these ASCII format files are imported into the Massflow software of the three-dimensional numerical simulation module for further processing to generate a three-dimensional landslide model of Gouhebei landslide.

[0092] The stability coefficient of the landslide under the condition of rainfall with a 50-year return period is 0.957, so the strength reduction factor is 0.957. The rock and soil strength parameter values under the natural scenario are multiplied by 0.957 to obtain the rock and soil strength parameter values under the condition of rainfall with a 50-year return period. Similarly, under the condition of rainfall with a 100-year return period, these parameter values are assigned to determine the parameters in the Massflow software to obtain the three-dimensional landslide model under the current scenario.

[0093] Step S5: Based on the three-dimensional landslide models under different scenarios obtained in step S4, the motion of the landslide is numerically simulated in the Massflow software, and the motion range, velocity, and flow depth map under different working conditions are output. The three-dimensional motion characteristics of the landslide under different scenarios are analyzed.

[0094] To better show the three-dimensional motion process of Gouhebei landslide, four time nodes of T=5s, 20s, 30s, and 60s are selected to analyze the motion characteristics, as shown in FIGS. 1-4. Figure 1 、 2

[0095] Finally, the motion range, velocity, and flow depth map under the conditions of rainfall with a 50-year return period and rainfall with a 100-year return period are analyzed in the system result analysis module, and it is concluded that the velocity, flow depth, and disaster-causing effect of the landslide under the condition of rainfall with a 100-year return period are greater than those under the condition of rainfall with a 50-year return period.

[0096] Example 2

[0097] This example considers a three-dimensional stability and finite difference landslide disaster effect analysis system, which includes:

[0098] ​A database module is configured to store high-resolution remote sensing, high-resolution digital elevation model, rainfall and other high-resolution topographic data of landslides.

[0099] A groundwater level calculation module is configured to calculate the initial groundwater level height under cumulative rainfall based on steady-state recharge and catchment contribution area by using a Fast Shallow Landslide Assessment Model (FSLAM), and then calculate the groundwater level change height after event rainfall by using event rainfall and runoff curve, so as to obtain the groundwater level height h after event rainfall of the landslide to be analyzed. a + = h e .

[0100] A stability analysis module is configured to simplify a landslide stability coefficient formula based on a Bishop simplified method or a Fellenius method, calculate the stability coefficient by using the simplified formula, and perform landslide stability analysis to determine the landslide volume and the ratio of the landslide volume to the area.

[0101] In the present application, the two-dimensional radius is expanded into a visual inclination angle in a three-dimensional sliding direction, the geometric center of the grid column is dynamically calculated to obtain the force arm, the pore water pressure term is introduced, and finally the stability coefficient is used to dynamically reduce the cohesion and internal friction angle of the rock-soil mass to reduce the error caused by the simplification assumption.

[0102] A three-dimensional numerical simulation module is configured to perform motion numerical simulation on the landslide by using the Massflow software based on finite difference.

[0103] A result analysis module is configured to perform disaster-causing effect analysis on the landslide based on the landslide motion range, speed and depth map under different working conditions output by the three-dimensional numerical simulation module, so as to obtain the disaster-causing effect of the landslide under different working conditions. The three-dimensional landslide distribution map, stability coefficient distribution map, landslide volume and downstream impact prediction can also be output.

[0104] The present application defines the sliding surface search range by grid based on DEM data, supports non-circular arc sliding surface modeling (such as polyline, multi-stage sliding surface), dynamically adjusts the material parameters by taking the stability coefficient as the strength reduction factor of the Massflow input, realizes the whole-chain analysis from instability judgment to motion simulation, realizes the linkage analysis of the instability threshold (the landslide starts to slide when the instability threshold is reached) and the motion simulation by dynamically feeding back the stability coefficient to the Massflow software to adjust the material parameters.

[0105] The above merely provides the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0106] The present application is not described, which is applicable to the prior art.

Claims

1. A landslide disaster-causing effect analysis method considering three-dimensional stability and finite differences, characterized by, The analysis method comprises the following steps: S1, obtaining the relevant information of the landslide by using satellite remote sensing technology, ground sensor network or public meteorological database, wherein the relevant information of the landslide comprises the landslide watershed range, landslide soil information, landslide rainfall data, digital elevation model DEM and soil attribute parameters; the soil attribute parameters comprise density, porosity, cohesion, friction angle, unit weight, basal friction coefficient, pore water pressure, runoff curve number and average saturation; S2, import DEM into GIS software, calculate the initial groundwater level height h of each grid under the cumulative rainfall a and groundwater level height h after event rainfall a +h e ; wherein, where h e is the change in groundwater level after the event; CN is the curve number; P e is the event rainfall; n f is the fillable porosity, n f = n · (1 - S r ), n is the porosity, S r is the average saturation over the entire depth before the event; S3, with (h) a h a +h e The elevation range is used as the basis, and the spatial range of possible sliding surface distribution is delineated based on the DEM data of the study area and the landslide boundary. The sliding surface search range is set grid by grid according to the elevation range and the possible spatial range of sliding surface distribution for each grid, with h as the reference. a The distance to the slope surface is taken as the maximum depth, denoted by h. a +h e The distance to the slope surface is used as the minimum depth, and then the depth range of the sliding surface is set grid by grid. Each sliding surface within the search range is considered as a sliding body. Then, the stability coefficient is calculated for all sliding bodies in the landslide to be analyzed, and the landslide stability coefficient distribution map, sliding body volume file, and sliding body volume to area ratio file are obtained. S4, importing the digital elevation model DEM into the Massflow software, constructing a three-dimensional model of the landslide in the sliding surface search range, taking the sliding body volume output in step S3 as the square of the sliding source area, taking the ratio of the sliding body volume and area output in step S3 as the average depth of the sliding body, and dynamically reducing the mechanical parameters of the sliding body by using the landslide stability coefficient obtained in S3, so as to directly use the mechanical parameters of the sliding body after strength reduction for landslide motion numerical simulation, and obtain the landslide influence range, speed and flow depth for evaluating various disaster effects possibly caused by the landslide.

2. The method of claim 1, wherein, The calculation formula of the stability coefficient Fs is: where e i，j is the horizontal seismic force arm of the grid column, which is the vertical distance from the centroid of the grid column to the elevation of the rotation axis, G i，j is the gravity of the grid column, k i，j is the horizontal seismic coefficient; a i,j is the force arm of the grid column in the direction of gravity, which is the horizontal distance from the rotation axis to the centroid of the grid column; A i，j is the potential sliding surface area of the grid column located in the i-th row and j-th column; S i，j is the distance from the bottom surface of the grid column to the rotation axis; a i,j is the apparent inclination angle of the bottom surface of the grid column in the sliding direction; s i，j is the normal stress of the grid column in the i-th row and j-th column; c i，j and is the shear strength parameter of the sliding surface of the grid column in the i-th row and j-th column, u i，j is the pore water pressure.

3. The method of claim 2, wherein, The calculation formula of the stability coefficient Fs is simplified by using Fellenius method and Bishop simplified method respectively, and any one of the simplified formulas is used as the basis for determining the distribution map of the landslide stability coefficient.

4. The method of claim 2, wherein, When the DEM data of the research area and the landslide boundary are used to determine the spatial range in which the sliding surface may be distributed, if the terrain feature in the landslide boundary is an abrupt region with a slope greater than 30°, the spatial search range is reduced, and if the terrain feature is a gentle region with a slope not greater than 30°, the search range is expanded, so as to determine the spatial range in which the sliding surface may be distributed.

5. A landslide disaster-causing effect analysis system considering three-dimensional stability and finite differences, characterized by, The system adopts the method of any one of claims 1-4, comprising: a database module for storing the relevant information of the landslide, including the landslide watershed range, landslide soil information, landslide rainfall data, digital elevation model DEM and soil attribute parameters; a groundwater level calculation module, configured to calculate an initial groundwater level height under cumulative rainfall based on steady-state recharge and catchment contribution area by using a fast shallow landslide assessment model (FSLAM), and then calculate a groundwater level change height after event rainfall by using event rainfall and a runoff curve, so as to obtain a groundwater level height h after event rainfall of a landslide to be analyzed a +h e ; a stability analysis module for simplifying the stability coefficient formula based on Bishop simplified method or Fellenius method, calculating the stability coefficient by using the simplified formula, and determining the sliding body volume and the ratio of the sliding body volume and area; a three-dimensional numerical simulation module for using the Massflow software to simulate the motion of the landslide; a result analysis module for analyzing the disaster-causing effect of the landslide based on the landslide motion range, speed and depth map obtained under different working conditions by the three-dimensional numerical simulation module; FSLAM is used to calculate the change of groundwater level under event rainfall in real time, interact with the stability analysis module, realize the closed-loop feedback of rainfall infiltration-stability coefficient-motion simulation, take the stability coefficient as the strength reduction factor of the Massflow input to dynamically adjust the material parameters, and realize the whole-chain analysis from instability judgment to motion simulation.

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