Regional scale landslide hydraulic triggering modeling method considering depth heterogeneity

Abstract

The invention discloses a regional scale landslide hydraulic triggering modeling method considering depth heterogeneity. The method comprises the following steps: acquiring data such as weather, terrain, soil and vegetation characteristics as input layer data of a subsequent model; based on a GEOtop 3.0 model, obtaining soil moisture content and pore water pressure of each time step of the target area; and constructing a landslide hydraulic triggering process model VH-LHT considering the depth heterogeneity of soil characteristics, and synchronously obtaining the layer-by-layer safety coefficient and damage depth of a landslide unit based on input layer data and an output result of the GEOtop 3.0 model at the current time step. According to the regional scale landslide hydraulic triggering modeling method considering depth heterogeneity, changes of parameters along the depth are considered, force transmission between soil columns is achieved, seamless coupling with a GEOtop 3.0 model is achieved, the depth heterogeneity modeling capacity is improved, and the mass-occurring landslide space prediction precision is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of landslide hydraulic triggering process monitoring, and in particular to a regional-scale landslide hydraulic triggering modeling method considering depth heterogeneity. Background Art

[0002] Physics-based process modeling is achieved by coupling a distributed hydrological model with a slope stability model. The distributed hydrological model calculates soil water potential and moisture content in the target area. After cell mapping, the slope stability model then calculates the slope stability of each cell. Ultimately, the impact of soil water dynamics on the timing, rate, volume, and location of shallow landslides is assessed.

[0003] Driven by computational efficiency and disciplinary limitations, early hydrological models focused on calculating sources and sinks across the entire watershed, treating groundwater flow and saturated and unsaturated seepage in soil layers as black boxes. However, with advances in computer performance and the increasing interdisciplinary nature of hydrological models, hydrological models have gradually evolved into process models with clear physical concepts and are increasingly coupled with models from fields such as climate, geology, and ecology.

[0004] Based on these hydrological models, landslide researchers have conducted basin-scale physical modeling of slope instability. To explain the hydraulic triggering process of rainfall-induced landslides, many studies have implemented more sophisticated coupled modeling, such as using the 3DRichards equation solver and infinite slope stability analysis. Subsequently, optimization of slope stability models has also been gradually developed. A landslide hydraulic-mechanical coupled triggering model (LHT model) was established based on sandpile unit automaton theory, discretizing the soil above the bedrock into hexagonal columns connected by mechanical "keys." This model improves on the traditional infinite slope model, reproducing the local soil strength failure and the interaction between the forces of the columns. It has been widely used in areas with thin weathering layers. To expand the model's application, the slip surface search method was coupled to the LHT model, improving the model's overestimation of landslide volume and thickness in areas with thick weathering layers.

[0005] However, the coupled modeling approach of the Deeply Layered Landslide Hydraulic-Mechanical Triggering Model (D-LHT model), based on the improved LHT, combined with the SWAT model, does not spatially discretize along the slope normal (toward the center of the Earth). This makes it impossible to store heterogeneous information about soil depths (e.g., soil dry density, hydraulic conductivity, root density, and other parameters). This makes the model appear to dynamically search for slip surfaces, but the actual calculation of soil column stability at a given time step is simply a function of depth and moisture content, making it unsuitable for areas with thick weathered layers and high vertical heterogeneity.

[0006] For example, the vegetation coverage rate of the low hilly area in the southeast coastal provinces of China is high, and the root density decreases with depth, which significantly increases the variation gradient of the hydraulic conductivity and cohesion of the root soil and the underlying rootless soil. If all the underground heterogeneity is attributed to the average or "effective" parameters, it is likely that the soil hydraulic parameter "fault" phenomenon caused by vegetation and the phenomenon of root system controlling the position of the sliding surface cannot be captured. Secondly, the modeling strategy of SWAT+D-LHT is to input the soil water content and surface water head of the hydrological response unit calculated by the SWAT model into the D-LHT model, and then divide the saturated and unsaturated zones by calculating the wetting front depth. This method may cause greater deviation between the inversion results and the true values due to overestimation of soil bulk density and simplification of the unsaturated seepage process.

[0007] Based on the problems of the above model, the present application is devoted to constructing a dynamic hierarchical landslide hydro-mechanical coupling triggering model (VH-LHT) considering depth heterogeneity, realizing three-dimensional layered data mapping with a comprehensive hydrological model. Then, the VH-LHT model is coupled with the GEOtop 3.0 model to establish a landslide hydrological triggering process coupling process model for group rainfall landslides with high spatio-temporal resolution and considering depth heterogeneity. SUMMARY

[0008] The purpose of the present application is to provide a regional scale landslide hydrological triggering modeling method considering depth heterogeneity, to solve the transient seepage error caused by the dependence of the traditional model on the "wetting front approximation method" and the slope stability calculation error caused by the uniformization of the input parameters along the depth; to support automatic switching between saturated and unsaturated states, accurately reflect the lag effect of rainfall infiltration; to improve the depth heterogeneity modeling capability and improve the spatial prediction accuracy of group landslides.

[0009] To achieve the above purpose, the present application provides a regional scale landslide hydrological triggering modeling method considering depth heterogeneity, comprising the following steps: Step S1, obtaining meteorological data, topographic data, soil data and vegetation characteristic data as input layer data for the subsequent model; Step S2, obtaining the soil water content and pore water pressure of each time step of the target area based on the GEOtop 3.0 model as the input of the subsequent model; Step S3, constructing a landslide hydrological triggering process model VH-LHT considering the depth heterogeneity of soil properties, based on the input layer data and the output results of the GEOtop 3.0 model at the current time step, synchronously obtaining the safety factor and failure depth of each layer of the landslide unit.

[0010] Preferably, in step S1, meteorological data, topographic data, soil data and vegetation characteristics are obtained as input layer data for the subsequent model; Among them, meteorological data includes but is not limited to temperature and rainfall; terrain data includes but is not limited to digital elevation model, aspect, and slope; soil data includes but is not limited to hydrological characteristics and geotechnical characteristics; vegetation characteristics include but are not limited to leaf area index, evapotranspiration, and root area ratio; in addition to the above data types, it also includes but is not limited to land use and soil type.

[0011] Preferably, in step S2, the input layer data is preprocessed based on the GEOtop 3.0 model, and the specific process is as follows: First, the land use types are mapped to a two-dimensional grid and data are assigned to each data type; Secondly, soil types are mapped to initial values ​​of the three-dimensional grid and data are assigned to each data type; Finally, perform numerical settings and simulation control conditions, including processing time step, maximum number of iterations, convergence residual, and matching simulation start and end dates; Among them, the time step can be adjusted under the premise of complying with the CFL condition; for each grid at a certain time step, its two-dimensional grid uses the D8 topology algorithm to calculate surface runoff as a surface calculation unit, and the three-dimensional grid below it is the underground calculation unit. By calculating the water and energy flux of the unit, real-world inversion and prediction are achieved.

[0012] Preferably, the nonlinear partial differential equation is solved by a three-dimensional Richards equation solver, and the runoff on the grid surface in the target area and the soil moisture content and pore water pressure at different depths below the grid surface are output along the time series; The numerical solution is performed based on the Newton-Raphson iterative method, and the Jacobian matrix is ​​iteratively calculated using the BI-CGSTAB method.

[0013] Preferably, in step S3, based on the sand pile unit automaton model, the implementation method of the LHT model is optimized, and an object-oriented programming method is used to construct a landslide hydraulic triggering process model VH-LHT that takes into account the heterogeneity of soil properties along the depth; the VH-LHT model will be called after the calculation of each time step of the GEOtop 3.0 model.

[0014] Preferably, based on the constructed VH-LHT model, the input layer data and the output result of the current time step of the GEOtop 3.0 model are preprocessed, and the specific process is as follows: First, the landslide unit is instantiated, the unit static parameters are mapped, the unit matrix is ​​constructed, and the static and dynamic parameters of each layer of the landslide unit are assigned; Then, perform numerical settings, including processing time step, spatial resolution, maximum number of iterations, and convergence residual; Finally, the dynamic parameters of the current time step are loaded and mapped to the landslide unit; To balance the output information richness of the integrated hydrological model and the mechanical conduction mechanism of the LHT model, the VH-LHT model is based on the concept of space-time cubes. It discretizes the plane space at the grid resolution of the digital elevation model and regards the entire soil column under the digital elevation model as a landslide unit. Each landslide unit can store Z-dimensional information in a hierarchical manner, achieving seamless coupling with the GEOtop 3.0 model.

[0015] Preferably, based on the established landslide unit object, each layer of soil in the landslide unit can be mapped to the unsaturated moisture content and dry soil weight one by one, and when calculating the total stress borne by each layer of the landslide unit, the stress contributed by the dry soil is used. , stress contributed by water and vegetation additional stress get; Among them, the stress contributed by dry soil is and stress contributed by water The value of is obtained by stratified cumulative sum, as follows: ; in, It is dry soil heavy; is the weight of water; is the depth of the current layer, which is obtained by adding half the thickness of the current layer to the thickness of each layer above it, consistent with the direction of gravity; For the layer thickness; The index of the layer above the current layer; is the current layer thickness; is the current layer number; For the Layer moisture content; is the volumetric moisture content of the current layer.

[0016] Preferably, the safety factor FS of each layer of the landslide unit is obtained by the limit equilibrium method. Assuming that the sliding surface is parallel to the slope surface, the safety factor is the anti-sliding force and sliding force The ratio of In the VH-LHT model, the anti-slip force The expression is as follows: ; in, Shear strength of soil , root reinforcement effect Additional anti-sliding force provided by surrounding soil columns It consists of three parts; is the effective normal stress; is the effective friction angle; For effective cohesion; is the correction coefficient of overestimation of the model; is the average tensile strength of the root system in unit area of soil; is the root direction factor; is the root area ratio; sliding force The expression is as follows: ; wherein, is composed of the self-weight stress component of the soil body , the vegetation additional stress along the slope component and the additional sliding force provided by the surrounding soil column; Therefore, the safety factor of the VH-LHT model in the unsaturated, transient saturated and stable saturated states is as follows: ; wherein, is the current layer pore water pressure, which is negative in the unsaturated state; is the slope; is the residual volume moisture content, is the saturated volume moisture content, is the depth of the groundwater level.

[0017] Preferably, based on the initial safety factor distribution of a single time step, the landslide unit is subjected to force conduction iteration, and finally the safety factor FS and the failure depth of the landslide unit in each time step are obtained; The landslide unit conducts force in eight directions and has a potential instability direction; eight landslide units adjacent to the current landslide unit are regarded as neighborhood units, and the directions are one-to-one corresponding; the potential instability direction of the current landslide unit and the direction with a 45° deviation are regarded as downhill, and the remaining five directions are uphill; If the current landslide unit is unstable, the stable unit in the uphill provides the current landslide unit with additional anti-sliding force not more than the tensile strength of the root system, and the stable unit in the downhill provides the current landslide unit with additional anti-sliding force except for the one used for its own stability; If the current landslide unit is still unstable after reinforcement, the residual sliding force is transmitted to the landslide unit in the downhill; Therefore, if the current landslide unit exists in the downhill of the unstable unit in the uphill, the unstable unit not only cannot provide additional anti-sliding force, but also exerts pressure stress on it.

[0018] Therefore, the application adopts the above-mentioned regional scale landslide hydraulic triggering modeling method considering depth heterogeneity, and has the following beneficial effects: ​​(1) The three-dimensional layered discretization method is used to store soil parameters, which overcomes the homogeneity assumption of traditional models and improves the ability to model deep heterogeneity. It accurately captures the parameter gradient changes caused by vegetation roots and avoids ignoring the phenomenon of "hydraulic parameter faults".

[0019] (2) The dynamic calculation of water migration in the unsaturated zone by the three-dimensional Richards equation solver solves the transient seepage error caused by the traditional model's reliance on the "wetting front approximation"; it supports automatic switching between saturated and unsaturated states, accurately reflecting the hysteresis effect of rainfall infiltration.

[0020] (4) The safety factor is calculated layer by layer based on the infinite slope method, and the mechanical formula is selected dynamically according to the soil state, which significantly reduces the overestimation of landslide volume and thickness. The progressive destruction process of the soil is reproduced through the eight-directional force transmission of hexagonal landslide units, thereby improving the spatial prediction accuracy of group landslides.

[0021] (5) The netCDF data interface of the GEOtop 3.0 model is used to achieve hierarchical mapping between hydrological parameters and mechanical models to avoid data redundancy; the Newton-Raphson iterative method and the BI-CGSTAB sparse matrix solver are used to optimize computational efficiency while ensuring accuracy.

[0022] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a workflow diagram of the GEOtop 3.0+VH-LHT coupling model of the present invention; Figure 2 This is an overview of the GEOtop 3.0 model framework of the present invention; (a) is a three-dimensional spatial discrete map based on DEM; (b) is the calculation unit structure and data mapping mechanism; (c) is the code architecture of the hydrological process module; Figure 3 Figure 1 is a schematic diagram of the modeling process of the VH-LHT model of the present invention; wherein, (a) is the output data of the GEOtop 3.0 model; (b) is the construction of the landslide unit; (c) is the distribution diagram of the initial safety factor FS; (d) is the force transmission mechanism between landslide units; and (e) is the output of the VH-LHT model. DETAILED DESCRIPTION

[0024] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0025] like Figure 1 As shown in Figure 2, a regional-scale landslide hydraulic triggering modeling method considering depth heterogeneity includes the following steps: Step S1: Acquire meteorological data, terrain data, soil data, and vegetation characteristic data as input layer data for subsequent models; Step S2: Based on the GEOtop 3.0 model, the soil moisture content and pore water pressure of the target area at each time step are obtained as inputs for subsequent models; Step S3: Construct a regional-scale landslide hydraulic triggering process model (VH-LHT model) that considers the heterogeneity of soil properties along the depth. Based on the input layer data and the output results of the GEOtop 3.0 model at the current time step, the safety factor and failure depth of each landslide unit are obtained.

[0026] Example Step S1: Acquire meteorological data, terrain data, soil data, vegetation characteristic data, etc. as input layer data for subsequent models.

[0027] Among them, meteorological data include temperature, rainfall, etc.; terrain data include digital elevation model, aspect, slope, etc.; soil data include hydrological characteristics, geotechnical characteristics, etc.; vegetation characteristics include leaf area index, evapotranspiration, root area ratio, etc.; in addition to the above data types, it also includes land use, soil type, etc.

[0028] Step S2: Based on the GEOtop 3.0 model, the soil moisture content and pore water pressure of the target area at each time step are obtained as input for subsequent models.

[0029] GEOtop is built based on the C / C++ language. Its improved version 3.0 uses object-oriented programming to repackage the code of modules such as hydrological processes and energy exchange, making it easier for users to deploy and carry out secondary development on the Linux operating system.

[0030] The GEOtop 3.0 model combines the advantages of hydrological models and land surface models (LSMs), and realizes the coupled inversion of energy transfer from the surface to the underground and hydrological processes under complex terrain conditions at the watershed scale. Based on the grid resolution of the digital elevation model (DEM), the real space is discretized in the plane space, and then the underground space is discretized layer by layer along the center of the earth, such as Figure 2 As shown in (a) in .

[0031] Step S21: pre-process the input layer data based on the GEOtop 3.0 model.

[0032] First, the land use types are mapped to a two-dimensional grid and data are assigned to each data type.

[0033] Second, soil types are mapped to initial values ​​on a three-dimensional grid and data are assigned to each data type.

[0034] Finally, perform numerical settings and simulation control conditions, including processing time step, maximum number of iterations, convergence residual, etc., to match the simulation start and end dates.

[0035] The time step can be adjusted under the premise of complying with the CFL condition. For each grid at a certain time step, the 2D grid uses the D8 topology algorithm to calculate the surface runoff as the surface calculation unit, and the 3D grid below it is the underground calculation unit, such as Figure 2 As shown in (b) in . , Corresponding to the spatial resolution of DEM, The discrete thickness of each soil layer can be adjusted based on data accuracy and computational efficiency. The model calculates the water and energy fluxes of each unit to achieve real-world inversion and prediction.

[0036] Step S22: Drive the model through meteorological events at each time step to perform energy and mass balance.

[0037] This paper focuses on the changes in pore water pressure (matrix suction in the unsaturated zone) and soil moisture content caused by groundwater processes. The GEOtop 3.0 model uses the implicit backward Euler method (BEM) to solve the general partial differential equations of the Richards equation and the energy conservation equation in the form of finite differences to ensure numerical stability. ) for time discretization, for a certain three-dimensional grid cell in the spatial discretization computational domain ( ) is established, and its calculation point is located at the geometric center of the three-dimensional grid.

[0038] Therefore, the constructed difference equation expression is as follows: ; in, and represent the time steps, yes and At some point in the middle, is the time step; is a set of adjacent three-dimensional grid cells ( ) , and Respectively represent the current set of adjacent three-dimensional grid cells along , and The amount of deflection in direction; Represents the distance between two grid cell calculation points, calculated by dx, dy and dz; is the source-sink residual; is the mass / energy conservation residual; Represents the field variable that changes with time and space, and for the Richards equation corresponds to the soil water potential , for the energy conservation equation corresponding to temperature ; Represents the grid ( ) points to the adjacent grid ( ) direction, which corresponds to the permeability coefficient for the Richards equation , for the energy conservation equation the corresponding heat conduction coefficient is ; is a nonlinear function of the state variables, which for the Richards equation corresponds to the soil volumetric water content ; For the energy conservation equation, the internal energy density .

[0039] Step S23: Solve the nonlinear partial differential equation using a three-dimensional Richards equation solver, and output the runoff on the grid surface in the target area and the soil moisture content and pore water pressure at different depths below it along the time series.

[0040] (1) The numerical solution is performed based on the Newton-Raphson iterative method. Since the model considers the lateral seepage process, the value of N is 6, including 2 vertical directions and 4 lateral directions of the three-dimensional grid, as shown in Figure 2. Figure 2 As shown in (b) in .

[0041] (2) The BI-CGSTAB method is used to iteratively calculate the Jacobian matrix to reduce the waste of computing resources caused by sparse matrices. Figure 2 As shown in (c), it shows the key code logical architecture of the reconstructed hydrological process module.

[0042] Because the model uses a three-dimensional Richards equation solver for continuous transient solutions from saturated to unsaturated subsurface conditions, computational efficiency in the steady-state computational domain (the saturated zone) is compromised. However, the dynamically calculated hydraulic conductivity, soil moisture content, and matrix suction enable the model to better simulate the actual seepage conditions in the unsaturated zone, both horizontally and vertically. This overcomes the problem of traditional hydrological models where the wetting front can only advance after the soil reaches saturation. Therefore, the GEOtop 3.0 model is ideally suited to uncovering the "black box" of soil moisture evolution in the unsaturated zone, a prerequisite for landslide researchers to model the hydraulic triggering process of landslides.

[0043] The GEOtop 3.0 model uses a network common data format (netCDF) external library for efficient storage of grid data. GIS data at the watershed scale, such as land use, slope, and soil properties, can be directly mapped to the computational domain based on the DEM discrete grid after preprocessing. Point-scale field or experimental data can be mapped to different land use types and soil types layer by layer, ultimately achieving the mapping of all data and parameters. Figure 2 As shown on the left side of (b).

[0044] This storage and mapping method differs from models that classify hydrological units based on a posteriori knowledge (such as SWAT), storing more raw and heterogeneous underground information in each three-dimensional grid. This makes it possible for landslide researchers to develop progressive destructive hydraulic triggering models using soil columns as calculation units.

[0045] Step S3: Construct a landslide hydraulic triggering process model (VH-LHT model) that takes into account the heterogeneity of soil properties along the depth. Based on the input layer data and the output results of the GEOtop 3.0 model at the current time step, the safety factor and failure depth of each landslide unit are synchronously obtained.

[0046] Step S31: constructing a landslide hydraulic triggering process model (VH-LHT model) that takes into account the heterogeneity of soil properties along the depth.

[0047] Since traditional hydrological models are not conducive to revealing small-scale spatial heterogeneity and surface-subsurface hydrological processes, the present invention develops a dynamic hierarchical landslide hydraulic-mechanical coupling triggering model (VH-LHT model) to meet the needs of fine hydro-mechanical model coupling and realize the mapping of moisture content and pore water pressure calculation units covering vegetation disturbance at high spatial resolution.

[0048] Based on the sandpile cell automaton model, the LHT model implementation method was optimized and the model construction was realized using object-oriented programming. The VH-LHT model will be called after each time step of the GEOtop 3.0 model calculation.

[0049] Step S32: Based on the constructed VH-LHT model, preprocess the input layer data and the output results of the GEOtop 3.0 model.

[0050] First, the landslide unit is instantiated, the unit static parameters are mapped, the unit matrix is ​​constructed, and the static and dynamic parameters of each layer of the landslide unit are assigned.

[0051] Then, perform numerical settings, including processing time step, spatial resolution, maximum number of iterations, convergence residual, etc.

[0052] Finally, the dynamic parameters of the current time step are loaded and mapped to the landslide unit.

[0053] In order to take into account the output information richness of the comprehensive hydrological model and the mechanical transmission mechanism of the LHT model, the VH-LHT model is based on the concept of space-time cube, and discretizes the plane space with the grid resolution of the DEM. The entire soil column under the DEM is regarded as a landslide unit. Each landslide unit can store Z-dimensional information in a hierarchical manner, which can not only consider the change of parameters along the depth, but also realize the transmission of forces between soil columns, thereby achieving more accurate predictions.

[0054] like Figure 3 As shown in (a) and (b) in the figure, the GEOtop 3.0 model output has multiple dimensions of information, which are mapped layer by layer to the landslide unit objects. It is precisely because the VH-LHT model takes into account the heterogeneity of soil properties along the depth that it can be seamlessly coupled with the GEOtop 3.0 model, so that the calculation results of the GEOtop 3.0 model can be fully utilized, and the calculation units are mapped one by one without simplification. , Keep the output resolution consistent with the GEOtop 3.0 model. It can be consistent with the GEOtop 3.0 model or customized by the user.

[0055] Because the landslide unit object is established in this way, each layer of soil in the landslide unit can be mapped to the unsaturated moisture content and dry soil weight one by one, and the stress contributed by the dry soil can be used to calculate the total stress borne by each layer of the landslide unit. , stress contributed by water and vegetation additional stress The stress obtained in this way can better avoid the error caused by homogenization.

[0056] Among them, the stress contributed by dry soil is and stress contributed by water The value of is obtained by stratified cumulative sum, as follows: ; in, It is dry soil heavy; is the weight of water; is the depth of the current layer, which is obtained by adding half the thickness of the current layer to the thickness of each layer above it, consistent with the direction of gravity; For the layer thickness; The index of the layer above the current layer; is the current layer thickness; is the current layer number; For the Layer moisture content; is the volumetric moisture content of the current layer. More parameter descriptions are shown in the table.

[0057] Table 1 Parameter Description ;

[0058] Step S33: Obtain the safety factor FS of each layer of the landslide unit by using the limit equilibrium method.

[0059] Calculate the safety factor of the landslide element using the Infinity Slope Method .when The landslide unit is considered unstable when , the landslide unit is considered stable. Assuming the slip plane is parallel to the slope, the safety factor is the anti-sliding force and sliding force The ratio.

[0060] In the VH-LHT model, the anti-slip force The expression is as follows: ; in, Shear strength of soil , root reinforcement effect Additional anti-sliding force provided by surrounding soil columns It consists of three parts; is the effective normal stress, and its value is a function of soil moisture content and pore water pressure or matrix suction, and has different functional relationships under unsaturated, transient saturated and steady-state saturated conditions. is the effective friction angle; For effective cohesion. Root reinforcement follows the Wu / Waldron model. is the overestimation correction coefficient of the model; is the average tensile strength of roots per unit area of ​​soil; is the root direction factor; is the root area ratio.

[0061] Sliding force The expression is as follows: ; in, From the soil self-weight stress to the component , vegetation additional stress along the slope component and additional sliding forces provided by surrounding soil columns composition.

[0062] Therefore, the safety factors of the VH-LHT model in the three states of non-saturation, transient saturation and stable saturation are as follows: ; in, is the pore water pressure of the current layer, which is a negative value in the unsaturated state; is the slope; is the residual volume moisture content, is the saturated volume water content, is the depth to the groundwater level. Further parameter descriptions are shown in Table 1. Because of the layered calculation method, the soil layers below the groundwater level can use floating weight when calculating the self-weight stress, avoiding the overestimation of self-weight stress caused by homogenization calculations.

[0063] Based on the above parameter mapping and landslide unit stability test ( =0, =0), and obtain the safety factor distribution diagram of the target calculation area along the depth change and time series change, as shown in Figure 3 As shown in (c) in .

[0064] Step S34: Based on the initial safety factor distribution map of a single time step, the landslide unit is subjected to force transmission iteration, and finally the safety factor FS and the failure depth of the landslide unit in each time step are obtained.

[0065] The landslide unit of the VH-LHT model can transmit forces in eight directions and has a potential instability direction. The eight landslide units adjacent to the current landslide unit are regarded as neighboring units and correspond to the directions one by one, such as Figure 3 The potential instability direction of the current landslide unit and The direction with a 45° deviation is considered downhill, and the remaining 5 directions are uphill.

[0066] If the current landslide unit becomes unstable, the stable unit on the upslope can provide the current landslide unit with additional anti-slip force that does not exceed the tensile strength of the root system, and the stable unit on the downslope can provide the current landslide unit with additional anti-slip force in addition to its own stability.

[0067] If the current landslide unit remains unstable after reinforcement, the residual sliding force is transferred to the landslide unit on the downslope. It can be inferred that if the current landslide unit is located downslope from an unstable unit on the upslope, the unstable unit will not only fail to provide additional anti-sliding force but will also exert compressive stress on it, making it even more difficult to stabilize the current landslide unit. This model follows the natural law of force transfer and uses a multi-round, simultaneous algorithm to distribute additional anti-sliding force, more realistically simulating the stress evolution of the soil.

[0068] Therefore, the present invention adopts the above-mentioned regional-scale landslide hydraulic triggering modeling method considering depth heterogeneity, which not only takes into account the change of parameters along the depth, but also realizes the transmission of force between soil columns, and further realizes seamless coupling with the GEOtop 3.0 model, so that the calculation results of the GEOtop 3.0 model can be fully utilized, and the calculation units are mapped one by one without simplification, achieving more accurate predictions, improving the depth heterogeneity modeling capability, improving the spatial prediction accuracy of cluster landslides, supporting automatic switching between saturated and unsaturated states, and accurately reflecting the hysteresis effect of rainfall infiltration.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A regional-scale landslide hydraulic triggering modeling method considering depth heterogeneity, characterized by: The following steps are involved: Step S1: Acquire meteorological data, terrain data, soil data, and vegetation characteristic data as input layer data for subsequent models; Step S2: Based on the GEOtop 3.0 model, the soil moisture content and pore water pressure of the target area at each time step are obtained as inputs for subsequent models; Step S3: construct a landslide hydraulic triggering process model VH-LHT that takes into account the heterogeneity of soil properties along the depth. Based on the input layer data and the output results of the GEOtop 3.0 model at the current time step, the safety factor and failure depth of each landslide unit are synchronously obtained.

2. A regional-scale landslide hydraulic triggering modeling method considering depth heterogeneity according to claim 1, characterized in that: In step S1, meteorological data, terrain data, soil data, and vegetation characteristics are obtained as input layer data for subsequent models; Among them, meteorological data includes but is not limited to temperature and rainfall; terrain data includes but is not limited to digital elevation model, aspect, and slope; soil data includes but is not limited to hydrological characteristics and geotechnical characteristics; vegetation characteristics include but are not limited to leaf area index, evapotranspiration, and root area ratio; in addition to the above data types, it also includes but is not limited to land use and soil type.

3. A regional-scale landslide hydraulic triggering modeling method considering depth heterogeneity according to claim 1, characterized in that: In step S2, the input layer data is preprocessed based on the GEOtop 3.0 model. The specific process is as follows: First, the land use types are mapped to a two-dimensional grid and data are assigned to each data type; Secondly, soil types are mapped to initial values ​​of the three-dimensional grid and data are assigned to each data type; Finally, perform numerical settings and simulation control conditions, including processing time step, maximum number of iterations, convergence residual, and matching simulation start and end dates; Among them, the time step can be adjusted under the premise of complying with the CFL condition; for each grid at a certain time step, its two-dimensional grid uses the D8 topology algorithm to calculate surface runoff as a surface calculation unit, and the three-dimensional grid below it is the underground calculation unit. By calculating the water and energy flux of the unit, real-world inversion and prediction are achieved.

4. A regional-scale landslide hydraulic triggering modeling method considering depth heterogeneity according to claim 3, characterized in that: The nonlinear partial differential equation is solved by a three-dimensional Richards equation solver, and the runoff on the grid surface and the soil moisture content and pore water pressure at different depths below the grid surface in the target area are output along the time series. The numerical solution is performed based on the Newton-Raphson iterative method, and the Jacobian matrix is ​​iteratively calculated using the BI-CGSTAB method.

5. A regional-scale landslide hydraulic triggering modeling method considering depth heterogeneity according to claim 1, characterized in that: In step S3, based on the sandpile unit automaton model, the implementation method of the LHT model is optimized, and an object-oriented programming method is used to construct the landslide hydraulic triggering process model VH-LHT, which takes into account the heterogeneity of soil properties along the depth. The VH-LHT model will be called after the calculation of each time step of the GEOtop 3.0 model.

6. A regional-scale landslide hydraulic triggering modeling method considering depth heterogeneity according to claim 5, characterized in that: Based on the constructed VH-LHT model, the input layer data and the output results of the GEOtop 3.0 model at the current time step are preprocessed. The specific process is as follows: First, the landslide unit is instantiated, the unit static parameters are mapped, the unit matrix is ​​constructed, and the static and dynamic parameters of each layer of the landslide unit are assigned; Then, perform numerical settings, including processing time step, spatial resolution, maximum number of iterations, and convergence residual; Finally, the dynamic parameters of the current time step are loaded and mapped to the landslide unit; To balance the output information richness of the integrated hydrological model and the mechanical conduction mechanism of the LHT model, the VH-LHT model is based on the concept of space-time cubes. It discretizes the plane space at the grid resolution of the digital elevation model and regards the entire soil column under the digital elevation model as a landslide unit. Each landslide unit can store Z-dimensional information in a hierarchical manner, achieving seamless coupling with the GEOtop 3.0 model.

7. A regional-scale landslide hydraulic triggering modeling method considering depth heterogeneity according to claim 6, characterized in that: Based on the established landslide unit object, each layer of soil in the landslide unit can be mapped to the unsaturated moisture content and dry soil weight one by one. When calculating the total stress borne by each layer of the landslide unit, the stress contributed by the dry soil is used. , stress contributed by water and vegetation additional stress get; Among them, the stress contributed by dry soil is and stress contributed by water The value of is obtained by stratified cumulative sum, as follows: ； in, It is dry soil heavy; is the weight of water; is the depth of the current layer, which is obtained by adding half the thickness of the current layer to the thickness of each layer above it, consistent with the direction of gravity; For the layer thickness; The index of the layer above the current layer; is the current layer thickness; is the current layer number; For the Layer moisture content; is the volumetric moisture content of the current layer.

8. A regional-scale landslide hydraulic triggering modeling method considering depth heterogeneity according to claim 7, characterized in that: The safety factor FS of each layer of the landslide unit is obtained by the limit equilibrium method. Assuming that the sliding surface is parallel to the slope surface, the safety factor is the anti-sliding force and sliding force The ratio of In the VH-LHT model, the anti-slip force The expression is as follows: ； in, Shear strength of soil , root reinforcement effect Additional anti-sliding force provided by surrounding soil columns It consists of three parts; is the effective normal stress; is the effective friction angle; For effective cohesion; is the overestimation correction coefficient of the model; is the average tensile strength of roots per unit area of ​​soil; is the root direction factor; is the root area ratio; Sliding force The expression is as follows: ； in, From the soil self-weight stress to the component , vegetation additional stress along the slope component and additional sliding forces provided by surrounding soil columns composition; Therefore, the safety factors of the VH-LHT model in the three states of non-saturation, transient saturation and stable saturation are as follows: ； in, is the pore water pressure of the current layer, which is a negative value in the unsaturated state; is the slope; is the residual volume moisture content, is the saturated volume water content, is the depth of groundwater level.

9. A regional-scale landslide hydraulic triggering modeling method considering depth heterogeneity according to claim 8, characterized in that: Based on the initial safety factor distribution of a single time step, the landslide unit is subjected to force transmission iteration, and finally the safety factor FS and failure depth of the landslide unit in each time step are obtained; The landslide unit transmits the force in eight directions and has a potential instability direction. The eight landslide units adjacent to the current landslide unit are regarded as neighboring units and correspond to the directions one by one. The potential instability direction of the current landslide unit and The direction with a 45° deviation is considered downhill, and the remaining 5 directions are uphill; If the current landslide unit becomes unstable, the stable unit on the upslope will provide the current landslide unit with an additional anti-slip force that does not exceed the tensile strength of the root system, and the stable unit on the downslope will provide the current landslide unit with an additional anti-slip force in addition to the force used for its own stability. If the current landslide unit is still unstable after reinforcement, the residual sliding force will be transferred to the landslide unit in the downslope; Therefore, if the current landslide unit exists in the downslope of the unstable unit in the upslope, the unstable unit will not only fail to provide additional anti-sliding force, but will also exert compressive stress on it.

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