Method and system for inverting the structure of a seismic-induced soft-hard interbedded back-dipping ancient landslide stratum

Abstract

The application discloses a method and system for inverting a structure of a seismic-induced soft and hard interbedding anti-inclined ancient landslide stratum, and relates to the technical field of seismic-induced landslide simulation and prevention, which comprises the following steps: reconstructing a pre-destabilization topography to obtain a geological profile of a main sliding direction before destabilization; constructing a plurality of soft and hard interbedding anti-inclined slope models with different soft and hard interbedding thickness ratios by using a discrete element numerical simulation technology based on a damage theory, and then simulating a dynamic failure process to obtain a characteristic line of a simulated slope failure surface; determining an actual topographic line based on unmanned aerial vehicle surveying and mapping data, and calculating a geometric matching degree according to the actual topographic line and the characteristic line of the simulated slope failure surface; selecting a soft and hard interbedding anti-inclined slope model with the largest geometric matching degree, and marking a corresponding soft and hard interbedding thickness ratio as a parameter of a seismic-induced pre-destabilization soft and hard interbedding anti-inclined ancient landslide stratum structure. The application can calculate the parameter of the seismic-induced pre-destabilization soft and hard interbedding anti-inclined ancient landslide stratum structure which cannot be directly obtained through field investigation.

Description

Technical Field

[0001] The present application relates to the technical field of earthquake-induced landslide simulation and prevention, and in particular to a method and system for inverting the stratum structure of earthquake-induced soft-hard interlayered reverse-dip ancient landslide. Background Art

[0002] Earthquake-induced landslides are one of the most destructive types of geological hazards, often resulting in severe casualties and enormous property losses. Among them, anti-dip slopes with interbedded soft and hard layers are prone to large-scale damage under earthquakes due to their unique lithologic composition and structural characteristics. Clarifying the instability conditions and failure modes that lead to large-scale failure of anti-dip slopes with interbedded soft and hard layers under seismic loads has important theoretical guidance and practical application value for the early identification of geological hazards, risk assessment, and disaster prevention engineering design.

[0003] In the field, the thickness of soft and hard rock layers often exhibits irregular distribution characteristics. In previous engineering geological research practices, given the significant differences in the mechanical properties of hard and soft rocks, in order to simplify the analysis process, the "soft-hard interlayer thickness ratio" is usually used to generalize the complex interlayer structure, thereby characterizing the spatial combination relationship between soft and hard rocks. It has been found that the soft-hard interlayer thickness ratio is a key structural parameter for evaluating the stability and failure mode of soft-hard interlayer anti-dip slopes. At present, the acquisition of the soft-hard interlayer thickness ratio of soft-hard interlayer anti-dip slopes mainly relies on the engineering geological survey technology system, including outcrop line surveying, borehole sampling, and horizontal tunnel investigation. These methods interpret geological profiles or drill core data, systematically calculate the thickness of soft and hard rock layers, and finally extract the soft-hard interlayer thickness ratio parameter that characterizes the regional stratigraphic structure characteristics.

[0004] However, for soft and hard interbedded reverse-inclined slopes that have undergone large-scale damage, the rear edge of the landslide often forms a steep failure surface due to the brittle bending and breaking of the rock mass. The middle of the sliding surface and the area near the slope foot are also often significantly affected by secondary geological transformation, which is manifested as follows: (1) the sliding surface is structurally disturbed by the erosion of debris flow; (2) the shear outlet area is covered by loose accumulations such as colluvial deposits and boulders. These processes make it difficult to accurately obtain the soft and hard interbedded thickness ratio parameters using traditional engineering geological survey methods. Therefore, establishing a method suitable for obtaining the stratigraphic structural characteristics of soft and hard interbedded reverse-inclined slopes that have undergone large-scale damage has become an urgent need for slope stability research. Summary of the Invention

[0005] The purpose of this application is to provide a method and system for inverting the earthquake-induced soft and hard interlayer anti-dip ancient landslide stratum structure, which can calculate the parameters of the soft and hard interlayer anti-dip ancient landslide stratum structure before the earthquake-induced instability that cannot be directly investigated.

[0006] To achieve the above objectives, this application provides the following solutions:

[0007] In a first aspect, the present application provides a method for inverting the earthquake-induced soft-hard interbedded reverse-dip ancient landslide stratum structure, comprising:

[0008] Based on UAV mapping data of the target landslide area and actual geological survey experimental data, the topography before instability was reconstructed to obtain the geological profile of the main sliding direction before instability.

[0009] Based on the actual geological survey experimental data and the geological profile in the main sliding direction before instability, a discrete element numerical simulation technology based on damage theory is used to construct multiple soft and hard interlayer anti-dip slope models with different soft and hard interlayer thickness ratios.

[0010] For any soft-hard interbedded reverse-inclined slope model, the dynamic failure process is simulated to obtain the characteristic line of the simulated slope failure surface.

[0011] An actual terrain line is determined based on the UAV surveying and mapping data, and a geometric matching degree is calculated according to the actual terrain line and the characteristic line of the simulated slope failure surface.

[0012] From all the soft-hard interlayer anti-dip slope models, the soft-hard interlayer anti-dip slope model with the greatest geometric matching degree is selected, and the corresponding soft-hard interlayer thickness ratio is marked as the parameter of the soft-hard interlayer anti-dip paleolandslide stratigraphic structure before the earthquake-induced instability.

[0013] In a second aspect, the present application provides a system for inverting the earthquake-induced soft-hard interbedded reverse-dip ancient landslide stratum structure, comprising:

[0014] The pre-instability terrain reconstruction module is used to reconstruct the pre-instability terrain based on the UAV mapping data of the target landslide area and the actual geological survey experimental data to obtain the geological profile of the main sliding direction before instability.

[0015] A multi-model construction module is used to construct multiple soft-hard interlayer anti-dip slope models with different soft-hard interlayer thickness ratios based on the actual geological survey experimental data and the geological profile in the main sliding direction before instability, using discrete element numerical simulation technology based on damage theory.

[0016] The dynamic failure simulation module is used to simulate the dynamic failure process of any soft and hard interlayer reverse slope model to obtain the characteristic line of the simulated slope failure surface.

[0017] The matching degree calculation module is used to determine the actual terrain line based on the UAV mapping data, and calculate the geometric matching degree according to the actual terrain line and the characteristic line of the simulated slope failure surface.

[0018] The parameter determination module is used to select the soft-hard interlayer anti-dip slope model with the largest geometric matching degree from all soft-hard interlayer anti-dip slope models, and mark the corresponding soft-hard interlayer thickness ratio as the parameter of the soft-hard interlayer anti-dip ancient landslide stratigraphic structure before earthquake-induced instability.

[0019] According to the specific embodiments provided in this application, this application has the following technical effects: this application combines high-precision UAV mapping data and actual geological survey experimental data obtained from field geological surveys to reconstruct the geological profile of the main sliding direction before instability; uses discrete element numerical simulation technology based on damage theory to construct multiple soft and hard interlayer anti-tilt slope models with different soft and hard interlayer thickness ratios, and then simulates the dynamic destruction process of all models and obtains the simulated slope failure surface characteristic lines under different soft and hard interlayer thickness ratios; finally, calculates the geometric matching degree between the simulated slope failure surface characteristic lines and the actual terrain, and selects the soft and hard interlayer anti-tilt slope model corresponding to the largest geometric matching degree as the optimal solution, thereby realizing the inversion of the geological structure characteristic parameters before large-scale vibration damage occurs on the soft and hard interlayer anti-tilt slope.

[0020] Through the above-mentioned processing steps, this application solves the technical difficulty that traditional exploration technology is difficult to obtain the overall stratigraphic structural characteristic parameters of the soft and hard interlayer anti-dip slope before large-scale instability due to steep terrain and coverage of colluvial deposits, namely, the thickness ratio of the soft and hard interlayers. It provides a new technical approach for reconstructing the stratigraphic structure of the soft and hard interlayer anti-dip slope model before instability, and has certain guiding value for the stability evaluation of rock slopes and disaster prediction in strong earthquake areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 Schematic diagram of the flow of a method for inverting earthquake-induced soft-hard interbedded reverse-dip paleolandslide stratum structure in one embodiment of the present application.

[0023] Figure 2 This is a schematic diagram of the inversion framework in one embodiment of the present application.

[0024] Figure 3 Schematic diagram of calculation of sliding mass volume after instability of soft and hard interlayered anti-inclined slope.

[0025] Figure 4 Schematic diagram of the calculation principle of geometric matching degree.

[0026] Figure 5 This is a full view of the landslide in another embodiment of the present application.

[0027] Figure 6 A schematic diagram of the geological section.

[0028] Figure 7 Schematic diagram of the numerical model of the soft-hard interlayer anti-dip slope with different soft-hard interlayer thickness ratios.

[0029] Figure 8 Schematic diagram of the failure surface morphology of each slope model after dynamic instability.

[0030] Figure 9 Schematic diagram of the calculation results of the geometric matching degree of the failure surface for different soft-hard interlayer thickness ratios. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0032] This application provides a discrete element numerical simulation technology based on damage theory and an inversion method for the thickness ratio of soft and hard interlayers based on the development characteristics of the failure surface of the soft and hard interlayer anti-dip slope under earthquake action. The soft and hard interlayer thickness ratio is inverted based on high-precision UAV remote sensing images and the development characteristics of the failure surface of the soft and hard interlayer anti-dip slope under earthquake action, which provides a new idea for obtaining the pre-destruction stratigraphic structure information of the soft and hard interlayer anti-dip slope that has suffered large-scale damage.

[0033] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0034] In an exemplary embodiment, Figure 1 and Figure 2 As shown, a method for inverting the earthquake-induced soft-hard interbedded reverse-dip paleo-landslide stratum structure is provided. In the embodiment of the present application, the following steps 101 to 105 are included.

[0035] Step 101 : reconstruct the terrain before instability based on the UAV mapping data of the target landslide area and the actual geological survey experimental data to obtain the geological profile of the main sliding direction before instability.

[0036] The drone mapping data are high-precision remote sensing images of the landslide area obtained by the drone (elevation accuracy 0.1m~0.5m).

[0037] The actual geological survey experimental data includes the thickness of the accumulation body at multiple points in the target landslide area, information of the dominant joint surface, and mechanical parameter indicators. Specifically, the determination process of the thickness of the accumulation body includes: in the field investigation, 10-20 characteristic points with obvious boundaries with the underlying basement are selected at the edge of the accumulation body, and the thickness of the accumulation body at each point is measured by using a ruler, a laser range finder and other tools. The determination process of the information of the dominant joint surface includes: the conventional engineering geological investigation method is adopted to identify the stratum lithology of the landslide area, measure the occurrence of the rock stratum, and obtain the information of the dominant joint surface by statistical analysis of the rock mass structure surface network. The determination process of the mechanical parameter indicators includes: indoor tests are performed on the rock samples collected in the field to obtain the mechanical parameter indicators, including the density, uniaxial compressive strength, shear strength, tensile strength and structure surface shear strength indicators of the rock.

[0038] In practical applications, step 101 includes steps (11)-(16) as follows.

[0039] (11) According to the unmanned aerial vehicle surveying and mapping data, a three-dimensional landslide terrain model is established. In the three-dimensional landslide terrain model, the boundaries of the landslide source area, the flow-through area and the accumulation area can be delineated according to the differences in the landforms.

[0040] (12) Based on the three-dimensional landslide terrain model and the thickness of the accumulation body at multiple points in the target landslide area, the volume of the accumulation body is calculated. Specifically, the measurement results (i.e. the thickness of the accumulation body at multiple points) of the thickness of the accumulation body edge obtained from the field are calibrated in the three-dimensional landslide terrain model, the morphology and elevation of the interface between the accumulation body and the underlying basement are inferred in combination with the surrounding terrain, and the volume of the accumulation body is calculated. The above process can be calculated by using ArcScence software.

[0041] (13) Based on the volume of the accumulation body, the landslide failure volume is calculated.

[0042] After the earthquake-induced slope failure causes the landslide body to separate from the parent rock, the landslide body will be severely disintegrated and broken during the movement, and will exhibit the characteristics of clastic movement. After all the clastic materials stop moving, the volume of the accumulation body will expand compared with the landslide body due to the redistribution of the blocks. Therefore, the landslide failure volume can be calculated according to the following formula :

[0043] .

[0044] wherein, V is the volume of the accumulation body, is the porosity of the landslide loose accumulation. The porosity of the loose accumulation The distribution range is 18%-35%, and its specific value is directly related to the particle size distribution of the debris. However, during the rapid movement of landslide debris, there are violent collisions and frictions between the blocks, which leads to a gradual increase in the degree of fragmentation of the blocks during the propagation process. Therefore, the particle size distribution of the blocks inside the accumulation body is not a constant value and is difficult to accurately measure by conventional methods. For reasonable simplification, this application assumes The average value is 26.5%.

[0045] (14) Determine the shear outlet width of the landslide based on the three-dimensional terrain model of the landslide.

[0046] (15) Based on the landslide damage volume and the landslide shear outlet width, the cross-sectional area of ​​the sliding body along the main sliding direction is calculated.

[0047] The failure mode of the soft-hard interlayered reverse-inclined slope is mainly toppling failure, and its failure surface can often be simplified as a circular arc surface passing through the slope foot. Then the unstable sliding body can be simplified as a triangular prism with a horizontal top surface and a bottom surface parallel to the main sliding direction of the landslide, and one of the side surfaces is a circular arc-shaped landslide failure surface. Figure 3 The figure shows the calculation diagram of the sliding body volume after the instability of the soft and hard interlayered anti-inclined slope. According to the calculation principle of the volume of the triangular prism, the cross-sectional area of ​​the sliding body along the main sliding direction is It can be calculated by the following formula:

[0048] .

[0049] in, is the landslide shear outlet width, also Figure 3 The height of the prism in .

[0050] (16) Based on the cross-sectional area of ​​the sliding body along the main sliding direction, a two-dimensional terrain profile is intercepted in the three-dimensional terrain model of the landslide to reconstruct the geological profile in the main sliding direction before the instability. Specifically, after the two-dimensional terrain profile along the main sliding direction is initially intercepted, the slope angle before the instability is repeatedly adjusted. , when the envelope area between the slope surface before instability, the slope top and the actual terrain surface is equal to When the slope is destabilized, a two-dimensional topographic profile in the main sliding direction of the slope failure front can be obtained, that is, a geological profile in the main sliding direction before instability.

[0051] Step 102 : Based on the actual geological survey experimental data and the geological profile in the main sliding direction before the instability, a discrete element numerical simulation technology based on damage theory (UDEC Damage Model, UDEC-DM) is used to construct multiple soft-hard interlayer anti-dip slope models with different soft-hard interlayer thickness ratios.

[0052] Among them, UDEC-DM is a discrete element modeling technology based on damage theory, which has been successfully used to simulate the geometric development characteristics of the failure surface of the soft and hard interbedded anti-dip slope. Step 102 specifically includes the following steps (21)-(23).

[0053] (21) Based on the geological profile of the main sliding direction before the instability, a discrete element numerical simulation technology based on damage theory is used to construct a two-dimensional discrete element numerical model of the reverse-inclined slope foundation; wherein, the thickness ratio of the soft and hard interlayers in the two-dimensional discrete element numerical model of the reverse-inclined slope foundation is 1:1.

[0054] During the construction of the two-dimensional discrete element numerical model for the reverse-dip slope foundation, parameters that induce dynamic slope instability must be rationally selected based on historical local earthquake data. The rock formation dip angle involved is derived from the dominant joint surface attitude data in the dominant joint surface information. Serving as a benchmark for subsequent construction of reverse-dip slopes with varying soft-hard interlayer ratios, this two-dimensional discrete element numerical model also effectively reflects information such as slope height, slope angle, and rock formation dip before earthquake-induced instability. This data can also be obtained from actual geological survey experimental data.

[0055] (22) Based on the two-dimensional reverse-inclined slope basic discrete element numerical model, multiple two-dimensional reverse-inclined slope discrete element numerical models with different soft-hard interlayer thickness ratios are established by changing the thickness of the soft rock layer and the hard rock layer; it should be noted that the external dimensions of these multiple models are consistent, and only the soft-hard interlayer thickness ratios are different.

[0056] In the usual process of constructing geomechanical models, rock layers with a particularly small thickness ratio often do not have a significant impact on the failure mode and geometry of the failure surface of the reverse slope. Therefore, they are often treated as interlayers or directly ignored. Therefore, the thickness ratio gradient of the soft and hard interlayers can be set to 0.25~4.0.

[0057] (23) For multiple two-dimensional discrete element numerical models of reverse-inclined slopes with different ratios of soft-hard interlayer thickness, the same constitutive relations and mechanical parameters are set to obtain multiple models of reverse-inclined slopes with different ratios of soft-hard interlayer thickness. In the existing material constitutive relations of the UDEC software, the Mohr-Coulomb elastoplastic constitutive relation is adopted for rock blocks, and the Coulomb slip constitutive relation is adopted for joints. The mechanical parameters of rock blocks and joints are determined based on the actual geological survey experimental data, including rock density, uniaxial compressive strength, shear strength, tensile strength, and structural plane shear strength index.

[0058] Step 103, for any soft-hard interlayer reverse-inclined slope model, simulate the dynamic failure process to obtain the characteristic line of the simulated slope failure surface; specifically, step 103 includes the following steps (31)-(33).

[0059] (31) Static calculations are performed based on the elastic constitutive theory to determine the initial stress field of the soft-hard interlayer anti-inclined slope model.

[0060] Specifically, for steep rock slopes, ignoring the initial stress field will lead to significant errors in the dynamic calculation results. Therefore, for the reverse-inclined slope model with interbedded soft and hard layers, the elastic constitutive theory is used to perform static calculations to restore the initial stress field.

[0061] Under this condition, only the gravity of the rock mass itself is considered. Therefore, the boundary conditions of the model are set as follows: the displacement in the x-direction is constrained on both sides, the displacement in the y-direction is constrained on the bottom, and the gravitational acceleration is applied to all blocks: Then, a static calculation is performed considering only gravity, and it is assumed that when the maximum unbalanced force The stress field at is the initial stress field of the slope.

[0062] (32) Determine an expression for the velocity of seismic waves, and determine the vibration excitation of normal stress and shear stress based on the expression for the velocity of seismic waves; the vibration excitation of normal stress and shear stress constitute seismic load parameters.

[0063] For ancient landslides with no historical earthquake records, the seismic waves that induce their instability can often be assumed to be sinusoidal simple harmonic waves, expressed as:

[0064] .

[0065] in, is the velocity of the seismic wave applied to the model boundary, unit: m / s; is the peak velocity of the seismic wave, unit: m / s; is the characteristic frequency of earthquake, unit: Hz. It can be calculated by the following formula:

[0066] .

[0067] in, is the peak ground acceleration of the earthquake.

[0068] also, is the effective duration of the earthquake action, in s, which can be determined according to the following empirical relationship:

[0069] .

[0070] in, The magnitude of the earthquake.

[0071] In all the above formulas, 、 、 All of these can be obtained from local earthquake data. The above formula can be used to determine the seismic wave velocity expression that induces slope instability, and then the velocity-time history curve can be converted into vibration excitation in the form of normal stress (normal stress) and shear stress (shear stress) acceptable to UDEC software using the following formula:

[0072] ; .

[0073] in, and are the applied normal stress and shear stress, respectively; is the density of the material; is the seismic wave velocity time history curve; and are the wave velocities of P-wave and S-wave passing through the rock mass, respectively, which can be calculated by the following formula:

[0074] ; .

[0075] in, and are the bulk modulus and shear modulus of the rock mass, respectively, and can be determined based on indoor test results.

[0076] (33) Using the initial stress field as an initial condition, the seismic load parameters are applied to the soft-hard interlayered reverse-inclined slope model to simulate a dynamic failure process and obtain a characteristic line of a simulated slope failure surface. Specifically, the seismic load parameters are applied to the bottom of the soft-hard interlayered reverse-inclined slope model to simulate a dynamic failure process under the action of a seismic load.

[0077] During the dynamic calculation process, each soft and hard interlayer anti-inclined slope model may become dynamically unstable or continue to remain stable. For the former, an irregular curve or broken line passing through the toe of the slope will appear between the landslide body and the bedrock, which can usually characterize the dynamic failure surface of the simulated slope. This application defines it as the characteristic line of the simulated slope failure surface. For the soft and hard interlayer anti-inclined slope model that undergoes earthquake-induced instability, although the change in the soft and hard interlayer thickness ratio will not affect the macroscopic failure mode of the slope, it will cause the failure surface of the slope to exhibit different geometric characteristics, including space and position. Therefore, by simulating the dynamic failure process of the soft and hard interlayer anti-inclined slope model with different soft and hard interlayer thickness ratios, a plurality of simulated slope failure surface characteristic lines with different geometric characteristics are obtained.

[0078] Step 104, determining the actual terrain line based on the UAV mapping data, and calculating the geometric matching degree according to the actual terrain line and the characteristic line of the simulated slope failure surface; specifically, step 104 includes the following steps (41)-(43).

[0079] (41) Based on the UAV mapping data, a three-dimensional landslide terrain model is established. This step is the same as step (11) above, and the established three-dimensional landslide terrain model can be directly called.

[0080] (42) Based on the three-dimensional landslide model, the actual topographic line of the landslide source area along the main sliding direction is extracted.

[0081] (43) Based on the X-axis difference between the actual terrain line and the characteristic line of the simulated slope failure surface, an average value is calculated to obtain the geometric matching degree. Figure 4 As shown, the steps are as follows:

[0082] 1) The actual topographic line and the simulated slope failure surface characteristic line are placed in the same coordinate system. In this process, the actual topographic line and the simulated slope failure surface characteristic line are both based on the slope foot as the origin.

[0083] 2) Evenly divide the actual terrain line and the simulated slope failure surface feature line along the Y-axis direction of the coordinate system to obtain multiple actual-simulated coordinate groups; one actual-simulated coordinate group includes an actual terrain point and a simulated slope failure surface feature point with the same Y-axis coordinate, and the corresponding coordinates can be expressed as: 、 Where N is the number of actual-simulated coordinate sets.

[0084] 3) For any actual-simulated coordinate set, calculate the X-axis difference , the calculation formula is: .

[0085] 4) Calculate the average deviation based on the X-axis differences corresponding to all actual and simulated coordinate groups. The calculation formula is:

[0086] .

[0087] 5) Based on the average deviation and the actual terrain line, calculate the geometric matching degree. The calculation formula of the geometric matching degree is:

[0088] .

[0089] Among them, F is the geometric matching degree, is the mean deviation, is the length of the actual terrain line in the X-axis direction.

[0090] Based on the above calculation principle, the geometric matching degree between the simulated slope failure surface characteristic line and the actual terrain line of all soft and hard interlayer reverse slope models with earthquake-induced instability is calculated respectively. .

[0091] Step 105 , selecting the soft-hard interlayer anti-dip slope model with the greatest geometric matching degree from all soft-hard interlayer anti-dip slope models, and marking the corresponding soft-hard interlayer thickness ratio as a parameter of the soft-hard interlayer anti-dip paleo-landslide stratigraphic structure before earthquake-induced instability.

[0092] According to the calculation principle of the geometric matching degree mentioned above, The larger or closer to 1, the closer the geometric features between the simulated failure surface feature line and the actual terrain line are. The maximum value of the soft-hard interlayer thickness ratio can be considered as the optimal solution of the slope stratigraphic structure before the earthquake-induced instability. The above steps complete the inversion of the stratigraphic structure of the earthquake-induced soft-hard interlayer reverse-dip paleolandslide.

[0093] In practical applications, the obtained inversion results can be compared with the stratigraphic structure information of local outcrops in the landslide source area obtained by conventional engineering geological survey methods to verify the consistency between the inversion results and the field survey results.

[0094] In another exemplary embodiment, the present application takes a landslide in a certain area as an example and provides a detailed process of inverting the earthquake-induced soft and hard interbedded reverse-dip ancient landslide stratigraphic structure, as shown below:

[0095] First, through traditional engineering geological surveys, it was found that the landslide was a reverse-dipping slope composed of soft and hard interlayers of metamorphic sandstone and slate before it failed, with a rock layer dip angle of approximately 55°. The landslide was caused by slope failure induced by an ancient earthquake. The current landslide surface is covered with gravel and slope deposits, and the trailing edge is steep, making it impossible to accurately determine the thickness ratio of the soft and hard interlayers before the failure. Based on this, high-precision drone terrain mapping was performed on the landslide body, and a 3D terrain model was constructed, such as Figure 5 shown.

[0096] Figure 5 In the middle, the landslide source area at the top is in the shape of a round chair. The lower and middle surfaces of the source area are covered by unevenly sized gravel blocks. The rear edge is steep and almost upright, with exposed rock layers and brittle fracture characteristics. During the field survey, the line survey method was used to conduct a statistical analysis of the rock structure surfaces of the stratum outcrops in the central gully, and the occurrence data of 197 joints were statistically analyzed. According to the statistical results, two groups of dominant structural surfaces have developed in the slope strata: JS1, with an inclination of 45°~65°, which is a continuous layer inclined inwardly; JS2, with an inclination of 30°~37°, which is a discontinuous joint inclined outwardly. In addition, there is a group of secondary joints JS3, which are inclined outwardly with an inclination of 35~45°. According to the relationship between the layer and the slope surface, the landslide in this embodiment was a typical reverse-inclined slope before it became unstable.

[0097] Figure 5The lower flow accumulation zone is roughly conchoidal in plan, with the leading edge of the accumulation zone eroded, exposing a longitudinal section where the accumulation zone and river alluvial deposits meet. Assuming the original valley was roughly flat, measurements using drone remote sensing imagery indicate a maximum accumulation thickness of 40 meters, located at the rear of the accumulation zone, with an average thickness of approximately 29 meters.

[0098] The sandstone and slate samples collected in the field were subjected to uniaxial compressive strength tests, direct shear tests, and Brazilian splitting tests using a YZW-50 multifunctional rock press to obtain the physical and mechanical parameters of the rock blocks.

[0099] Secondly, calculate the volume of the accumulation The width of the landslide shear outlet is about 12.8×106m³. =323m. Assuming the porosity of the loose deposits of the landslide before and after failure The average value is 26%, and the landslide damage volume can be obtained 10.2×10 6 m³. Then the cross-sectional area of ​​the sliding body in the direction parallel to the main sliding line is calculated =3.15×10 4 m 2 After repeated attempts, the slope angle before the landslide failure was about 58°, and the geological profile was drawn, as shown in the figure. Figure 6 shown.

[0100] Then, in Figure 6 On the basis of the geological profile of the main sliding direction before instability (A-A'), the discrete element commercial software UDEC was used to construct 11 numerical models of soft-hard interlayer anti-dip slopes with different soft-hard interlayer thickness ratios, such as Figure 7 As shown, they correspond to the soft-hard interlayer thickness ratios = 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 4:1, 1:1.5, 1:2, 1:2.5, 1:3, and 1:4, respectively.

[0101] The numerical model of the soft-hard interbedded counter-inclined slope has a height of 400m, a length of 550m, and a slope height of 346.4m. According to field stratum structural surface network statistics, there are three sets of dominant structural surfaces in the landslide area: JS1, JS2, and JS3. Of these, only JS1 has good connectivity. Therefore, a set of rock layer planes with a 55° inclination angle was set within the slope model. JS2 and JS3 are discontinuous structural surfaces, and their effects can also be reflected through polygonal meshes within the rock layer. According to field survey data, the rock layer thickness of the landslide in this example ranges from 0.8m to 2.2m, but for computational efficiency, this model increases the layer thickness to 15m.

[0102] To effectively control the size effect during UDEC-DM simulations of crack growth, the maximum size of the randomly sized polygonal blocks was set to 1.5 m (1 / 10 of the rock layer thickness). Therefore, the entire model was divided into 1510 randomly sized block elements. Mechanical parameters were then assigned to the sandstone blocks, slate blocks, and rock layer surfaces.

[0103] Furthermore, according to the relevant data from the Earthquake Administration, the time history expression of the seismic wave velocity that induces instability is obtained as follows: Static analysis simulation and dynamic analysis simulation were performed on each model to obtain the failure surface morphology at different soft-hard interlayer thickness ratios, such as Figure 8 shown.

[0104] Finally, MATLAB was used to binarize the curve and set the sampling density to 1000 to extract the coordinates. The geometric matching degree calculation formula was used to obtain the geometric matching degree between the failure surface morphology of the soft-hard interlayer anti-dip slope model after dynamic instability and the actual terrain surface under different soft-hard interlayer thickness ratios. ,like Figure 9 As shown in Figure 2, as the thickness ratio of the soft and hard interlayers increases from 0.33 to 4, the change in geometric matching degree shows a significant nonlinear characteristic of first increasing and then decreasing: when the thickness of the soft and hard interlayers increases from 0.33 to 0.4, The value increases to a peak value; when the thickness of the soft and hard interlayer gradually increases from 0.4 to 4, The value shows a downward trend. This shows that the change of the thickness of the soft and hard interlayer will significantly change the geometric shape of the failure surface of the soft and hard interlayer anti-dip slope model. Specifically, compared with the soft and hard interlayer thickness > 1, the soft and hard interlayer thickness < 1 maintains The high matching degree of >90% indicates that before the dynamic instability, it was a reverse slope model with soft and hard interlayers dominated by hard rock. Among them, when the thickness of the soft and hard interlayers is 0.4, the matching degree is The optimal solution was 97.54%. Therefore, it is believed that the optimal solution for the thickness of the soft and hard interlayers before the landslide dynamic failure is 1:2.5 (mainly hard rock).

[0105] Based on the same inventive concept, embodiments of the present application also provide a system for implementing the aforementioned method to invert the seismically induced soft-hard interbedded reverse-dip paleolandslide stratigraphic structure. The solution provided by this system is similar to the solution described in the aforementioned method. Therefore, the specific limitations in one or more of the system embodiments provided below can be found in the aforementioned method limitations and will not be further elaborated here.

[0106] The system provided in this application for inverting the earthquake-induced soft-hard interlayer anti-dip ancient landslide stratum structure includes:

[0107] The pre-instability terrain reconstruction module is used to reconstruct the pre-instability terrain based on the UAV mapping data of the target landslide area and the actual geological survey experimental data to obtain the geological profile of the main sliding direction before instability.

[0108] A multi-model construction module is used to construct multiple soft-hard interlayer anti-dip slope models with different soft-hard interlayer thickness ratios based on the actual geological survey experimental data and the geological profile in the main sliding direction before instability, using discrete element numerical simulation technology based on damage theory.

[0109] The dynamic failure simulation module is used to simulate the dynamic failure process of any soft and hard interlayer reverse slope model to obtain the characteristic line of the simulated slope failure surface.

[0110] The matching degree calculation module is used to determine the actual terrain line based on the UAV mapping data, and calculate the geometric matching degree according to the actual terrain line and the characteristic line of the simulated slope failure surface.

[0111] The parameter determination module is used to select the soft-hard interlayer anti-dip slope model with the largest geometric matching degree from all soft-hard interlayer anti-dip slope models, and mark the corresponding soft-hard interlayer thickness ratio as the parameter of the soft-hard interlayer anti-dip ancient landslide stratigraphic structure before earthquake-induced instability.

[0112] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0113] This document uses specific examples to illustrate the principles and implementation methods of this application. The description of the above examples is only intended to help understand the method and core concept of this application. At the same time, for those skilled in the art, based on the concept of this application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A method for inverting the stratum structure of earthquake-induced soft and hard interbedded reverse-dip ancient landslides, characterized in that: The method comprises: Based on UAV mapping data and actual geological survey experimental data of the target landslide area, the terrain before instability was reconstructed to obtain the geological profile of the main sliding direction before instability; Based on the actual geological survey experimental data and the geological profile in the main sliding direction before the instability, a discrete element numerical simulation technology based on damage theory is used to construct multiple soft and hard interlayer anti-dip slope models with different soft and hard interlayer thickness ratios; For any soft-hard interbedded reverse-inclined slope model, simulate the dynamic failure process to obtain the characteristic line of the simulated slope failure surface; including: Performing static calculations based on elastic constitutive theory to determine the initial stress field of the soft-hard interlayered reverse-inclined slope model; determining a seismic wave velocity expression, and determining the vibration excitation of normal stress and shear stress based on the seismic wave velocity expression; the vibration excitation of normal stress and shear stress constitutes seismic load parameters; using the initial stress field as an initial condition, applying the seismic load parameters to the soft-hard interlayered reverse-inclined slope model to simulate a dynamic failure process and obtain a simulated slope failure surface characteristic line; When the soft-hard interlayer anti-inclined slope model experiences dynamic instability, an irregular curve or broken line passing through the slope foot appears between the landslide body and the bedrock, which is used to represent the dynamic failure surface of the simulated slope and is defined as the characteristic line of the simulated slope failure surface. Determining an actual terrain line based on the UAV mapping data, and calculating a geometric matching degree based on the actual terrain line and the characteristic line of the simulated slope failure surface; including: The actual terrain line and the simulated slope failure surface characteristic line are placed in the same coordinate system; the actual terrain line and the simulated slope failure surface characteristic line are evenly divided along the Y-axis direction of the coordinate system to obtain multiple actual-simulated coordinate groups; one actual-simulated coordinate group includes an actual terrain point and a simulated slope failure surface characteristic point with the same Y-axis coordinate; for any actual-simulated coordinate group, the X-axis difference is calculated; based on the X-axis differences corresponding to all actual-simulated coordinate groups, the average deviation is calculated; and based on the average deviation and the actual terrain line, the geometric matching degree is calculated; the calculation formula for the geometric matching degree is: ； Among them, F is the geometric matching degree, is the mean deviation, is the length of the actual terrain line in the X-axis direction; From all the soft-hard interlayer anti-dip slope models, the soft-hard interlayer anti-dip slope model with the greatest geometric matching degree is selected, and the corresponding soft-hard interlayer thickness ratio is marked as the parameter of the soft-hard interlayer anti-dip paleolandslide stratigraphic structure before the earthquake-induced instability.

2. The method for inverting the earthquake-induced soft-hard interbedded reverse-dip ancient landslide stratum structure according to claim 1 is characterized in that: Determining an actual terrain line based on the UAV surveying data, and calculating a geometric matching degree based on the actual terrain line and the characteristic line of the simulated slope failure surface, including: establishing a three-dimensional terrain model of the landslide based on the UAV mapping data; Based on the three-dimensional landslide terrain model, extracting the actual terrain line of the landslide source area along the main sliding direction; Based on the X-axis difference between the actual terrain line and the simulated slope failure surface characteristic line, an average value is calculated to obtain a geometric matching degree.

3. The method for inverting the earthquake-induced soft-hard interbedded reverse-dip ancient landslide stratum structure according to claim 1 is characterized in that: The actual geological survey experimental data includes the thickness of the accumulation body at multiple points in the target landslide area; Based on UAV mapping data and actual geological survey experimental data of the target landslide area, the terrain before instability is reconstructed to obtain the geological profile of the main sliding direction before instability, including: establishing a three-dimensional terrain model of the landslide based on the UAV mapping data; Calculating the volume of the accumulation body based on the three-dimensional landslide terrain model and the thickness of the accumulation body at multiple points in the target landslide area; Based on the volume of the accumulation body, back-calculate the landslide damage volume; determining the shear outlet width of the landslide according to the three-dimensional landslide terrain model; Calculating the cross-sectional area of ​​the sliding body along the main sliding direction based on the landslide damage volume and the landslide shear outlet width; Based on the cross-sectional area of ​​the sliding body along the main sliding direction, a two-dimensional terrain profile is intercepted in the three-dimensional terrain model of the landslide to reconstruct the geological profile in the main sliding direction before instability.

4. The method for inverting the earthquake-induced soft-hard interbedded reverse-dip ancient landslide stratum structure according to claim 3 is characterized in that: The landslide damage volume The inverse calculation formula is: ； in, is the volume of the accumulation body, is the porosity of the loose deposits of the landslide; Cross-sectional area of ​​the sliding body along the main sliding direction The calculation formula is: ； in, is the width of the landslide shear outlet.

5. The method for inverting the earthquake-induced soft-hard interbedded reverse-dip ancient landslide stratum structure according to claim 1, characterized in that: Based on the actual geological survey experimental data and the geological profile in the main sliding direction before the instability, a discrete element numerical simulation technology based on damage theory is used to construct multiple soft-hard interlayer anti-dip slope models with different soft-hard interlayer thickness ratios, including: Based on the geological profile in the main sliding direction before the instability, a two-dimensional discrete element numerical model of the reverse-dip slope foundation is constructed using discrete element numerical simulation technology based on damage theory; wherein the thickness ratio of the soft and hard interlayers in the two-dimensional discrete element numerical model of the reverse-dip slope foundation is 1:1; Based on the two-dimensional reverse-dip slope basic discrete element numerical model, multiple two-dimensional reverse-dip slope discrete element numerical models with different soft-hard interlayer thickness ratios are established by changing the thickness of the soft rock layer and the hard rock layer; For multiple two-dimensional discrete element numerical models of reverse-inclined slopes with different soft-hard interlayer thickness ratios, the same constitutive relationship and mechanical parameters are set to obtain multiple soft-hard interlayer reverse-inclined slope models with different soft-hard interlayer thickness ratios; wherein, the mechanical parameters are determined based on the actual geological survey experimental data, including rock density, uniaxial compressive strength, shear strength, tensile strength and structural surface shear strength indicators.

6. A system for inverting the earthquake-induced soft-hard interbedded reverse-dip paleo-landslide stratigraphic structure, characterized by: The system comprises: The pre-instability terrain reconstruction module is used to reconstruct the pre-instability terrain based on UAV mapping data of the target landslide area and actual geological survey experimental data to obtain the geological profile of the main sliding direction before instability; a multi-model construction module for constructing, based on the actual geological survey experimental data and the geological profile in the main sliding direction before the instability, a plurality of soft-hard interlayer anti-dip slope models with different soft-hard interlayer thickness ratios by using a discrete element numerical simulation technology based on damage theory; The dynamic failure simulation module is used to simulate the dynamic failure process of any soft and hard interbedded reverse slope model to obtain the characteristic line of the simulated slope failure surface; it includes: Performing static calculations based on elastic constitutive theory to determine the initial stress field of the soft-hard interlayered reverse-inclined slope model; determining a seismic wave velocity expression, and determining the vibration excitation of normal stress and shear stress based on the seismic wave velocity expression; the vibration excitation of normal stress and shear stress constitutes seismic load parameters; using the initial stress field as an initial condition, applying the seismic load parameters to the soft-hard interlayered reverse-inclined slope model to simulate a dynamic failure process and obtain a simulated slope failure surface characteristic line; When the soft-hard interlayer anti-inclined slope model experiences dynamic instability, an irregular curve or broken line passing through the slope foot appears between the landslide body and the bedrock, which is used to represent the dynamic failure surface of the simulated slope and is defined as the characteristic line of the simulated slope failure surface. A matching degree calculation module is used to determine the actual terrain line based on the UAV mapping data, and calculate the geometric matching degree based on the actual terrain line and the characteristic line of the simulated slope failure surface; including: The actual terrain line and the simulated slope failure surface characteristic line are placed in the same coordinate system; the actual terrain line and the simulated slope failure surface characteristic line are evenly divided along the Y-axis direction of the coordinate system to obtain multiple actual-simulated coordinate groups; one actual-simulated coordinate group includes an actual terrain point and a simulated slope failure surface characteristic point with the same Y-axis coordinate; for any actual-simulated coordinate group, the X-axis difference is calculated; based on the X-axis differences corresponding to all actual-simulated coordinate groups, the average deviation is calculated; and based on the average deviation and the actual terrain line, the geometric matching degree is calculated; the calculation formula for the geometric matching degree is: ； Among them, F is the geometric matching degree, is the mean deviation, is the length of the actual terrain line in the X-axis direction; The parameter determination module is used to select the soft-hard interlayer anti-dip slope model with the largest geometric matching degree from all soft-hard interlayer anti-dip slope models, and mark the corresponding soft-hard interlayer thickness ratio as the parameter of the soft-hard interlayer anti-dip ancient landslide stratigraphic structure before earthquake-induced instability.

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