Method for determining key rock stratum of large dumping deformation body

Abstract

The invention discloses a method for determining a key rock stratum of a large dumping deformation body. Geological condition system investigation is carried out, and key geological information of the large dumping deformation body is ascertained; determining the characteristics of the fracture surface of the large toppling deformation body by drilling; if an embedded rock beam which is good in lithology, has a certain thickness and is complete in structure exists from the front part to the middle-rear part in the large dumping deformed body, the large dumping deformed body is determined to be an embedded rock beam type key rock stratum; otherwise, the residual unbalanced thrust of each unit rock stratum is calculated based on the superposed stress type cantilever beam, the independent stress type cantilever beam and the fracture mechanics multi-element fracture extension theory, and the peak position of the residual unbalanced thrust can be determined as the progressive dumping type key rock stratum. According to the method, accurate characterization and judgment of the key rock stratum of the large-scale toppling deformation body are achieved, and meanwhile key guidance is provided for instability mechanism research, reinforcement design and disaster early warning of the large-scale toppling deformation body.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of large-scale dumping deformation body slope stability identification and disaster evolution mechanism exploration, and particularly relates to a large-scale dumping deformation body key stratum determination method. BACKGROUND

[0002] In recent years, driven by major hydropower and transportation projects and extreme weather events, and with the rapid development of detection technology, the number of large-scale dumping deformation bodies and their instability disasters recorded in China has increased significantly. In the Sanjiang (Nujiang-Lancang-Jinsha) region, the scale and harm of such geological disasters are particularly prominent, and the personnel casualties and economic losses caused by them have become a major problem that cannot be ignored. However, the current understanding of the disaster mechanism of large-scale dumping deformation bodies is insufficient, and the deformation evolution of large-scale dumping deformation bodies is influenced by multiple factors such as geology and groundwater, which is hidden and nonlinear, making it difficult to accurately identify the instability critical condition; disaster prediction and early warning methods rely on surface monitoring and are difficult to fully reflect deep deformation, with limited accuracy; reinforcement methods such as anti-slide piles and anchoring have poor prevention and control effect on large-scale dumping deformation bodies, and at the same time, they have high cost and difficulty, which limits disaster prevention and control and management. Therefore, it is urgent to explore the deformation instability characteristics of large-scale dumping deformation bodies and understand their disaster evolution rules, which will provide an important basis for the prediction, early warning and management of large-scale dumping deformation body dumping deformation instability disasters.

[0003] During the deformation instability process of a large-scale dumping deformation body, layer-by-layer bending-tensile fracture occurs from bottom to top in the initial instability stage, and although slight bending deformation occurs in the upper rock layers of the slope, the overall integrity of the rock layers is good. At this stage, the displacement of the large-scale dumping deformation body increases at a small rate, and the overall stability decreases slightly. However, as the stability of the large-scale dumping deformation body further decreases, when a rock layer undergoes bending-tensile fracture, the rock layers above it almost fracture at the same time. At this time, the displacement of the large-scale dumping deformation body increases significantly, and it undergoes complete instability and destruction. Therefore, this rock layer has a key control effect on the overall stability of the large-scale dumping deformation body and the disaster evolution process, and it is called the key stratum of the large-scale dumping deformation body. At the same time, if the position of the key stratum of the large-scale dumping deformation body can be determined, the disaster evolution process and instability characteristics of the large-scale dumping deformation body can be characterized in detail. In addition, the key stratum of the large-scale dumping deformation body is often poorly developed in fissures and has good integrity, high strength and stiffness, and thick thickness. According to the related theories of material mechanics and structural mechanics, stress concentration is likely to occur in the key stratum during the instability process of the large-scale dumping deformation body, causing the peak value of the residual unbalanced thrust on the key stratum. At the same time, the rock layers above the key stratum mainly undergo dumping-bending failure, and the rock layers below the key stratum mainly undergo dumping-sliding failure. SUMMARY

[0004] In view of the deficiencies of the prior art, the technical problem to be solved by the present application is to provide a method for determining key rock strata of a large-scale toppling deformation body.

[0005] The technical solution of the present application for solving the technical problem is to provide a method for determining key rock strata of a large-scale toppling deformation body, characterized in that the method comprises the following steps: Step 1: Conduct a geological survey to obtain the geological structure, strike, trend and dip angle of the large-scale toppling deformation body, prove the rock lithology and thickness, determine the key engineering geological information of the large-scale toppling deformation body including the physical and mechanical material parameters of the rock-soil body, the erosion damage phenomenon and range of the slope surface, the rock strata cracking and toppling damage area of the large-scale toppling deformation body, and count the existing toppling instability area of each type of rock strata; Step 2: Along the elevation direction of the large-scale toppling deformation body, at least 6 drill holes are uniformly arranged at certain distances and elevations from the slope toe to the slope top, i.e. at least 2 drill holes are arranged in the slope toe, middle and top regions; in addition, the drill hole direction should be parallel to the rock strata dip angle direction, and then the depth and shape distribution law of the large-scale toppling deformation body are determined according to the RQD value, fracture surface distribution and weak plane distribution of the drill core; Step 3: According to the geological survey results of step 1, if the embedded rock beam type rock strata with relatively complete rock strata structure, thick rock strata thickness, high compressive, tensile and shear strength of the rock strata are found in the large-scale toppling deformation body, and the embedded rock beam type rock strata are distributed in the middle front to the middle back region of the large-scale toppling deformation body, it is considered that the region where the embedded rock beam type rock strata are located is the embedded rock beam type key rock strata of the large-scale toppling deformation body; Step 4: According to the geological survey results of step 1, if there is no embedded rock beam in the large-scale toppling deformation body, and there is only one rock strata lithology, the progressive toppling type key rock strata need to be determined by calculating the residual unbalanced thrust of each rock strata of the large-scale toppling deformation body; Step 5: If the rock strata integrity is good, the rock strata between each rock strata are closely adhered, there is no obvious erosion and hollowing damage of the rock strata at the slope toe of the large-scale toppling deformation body or there is no free surface formed under a complete rock strata, the residual unbalanced thrust calculation theory of each rock strata of the large-scale toppling deformation body is improved based on the multi-crack propagation theory of fracture mechanics and the cantilever beam model of superimposed stress type, and then the residual unbalanced thrust of each rock strata of the large-scale toppling deformation body is obtained; Step 6: If there is obvious erosion and hollowing damage of the rock strata at the slope toe of the large-scale toppling deformation body or there is a free surface formed under a complete rock strata, the residual unbalanced thrust calculation theory of each rock strata of the large-scale toppling deformation body is improved based on the multi-crack propagation theory of fracture mechanics and the cantilever beam model of single stress type, and then the residual unbalanced thrust of each rock strata of the large-scale toppling deformation body is obtained; Step 7: according to the calculation results of the residual unbalanced thrust of each rock layer of the large-scale dumping deformation body in step 5 or step 6, a residual unbalanced thrust distribution curve along the elevation of each rock layer is drawn, and the peak area of the residual unbalanced force of each rock layer is determined; at the same time, the geological survey results in step 1 need to be combined to judge whether the peak area of the residual unbalanced thrust is located at the boundary between the dumping damage area and the dumping-sliding damage area of the large-scale dumping deformation body; if yes, the rock layer in the peak area of the residual unbalanced thrust is considered as the gradual dumping type key rock layer of the large-scale dumping deformation body.

[0006] Compared with the prior art, the present application has the beneficial effects that: (1) The present application takes the geological conditions and stress characteristics of the large-scale dumping deformation body as the starting point, proposes a direct survey method, and improves the residual unbalanced thrust calculation method based on the superimposed stress type cantilever beam, the single stress type cantilever beam and the multi-element crack propagation theory of fracture mechanics, which provides clear basis for determining the positions of the two types of key rock layers (embedded rock beam type and gradual dumping type) of the large-scale dumping deformation body, and realizes the key breakthrough from qualitative judgment to quantitative characterization.

[0007] (2) The key rock layer determination method of the large-scale dumping deformation body proposed in the present application provides important guidance for exploring the instability and damage law of the large-scale dumping deformation body, clarifying the disaster evolution mode of the large-scale dumping deformation body, reasonably designing the slope reinforcement scheme of the large-scale dumping deformation body, and establishing the disaster prediction and early warning model of the large-scale dumping deformation body. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 The key technical process diagram of the present application; Figure 2 The large-scale dumping deformation body and its key rock layer schematic diagram; Figure 3 The stress intensity factor calculation model schematic diagram of the unit rock layer under the action of the basic load; Figure 4 The large-scale dumping deformation body superimposed stress type cantilever beam calculation model schematic diagram; Figure 5 The large-scale dumping deformation body single stress type cantilever beam calculation model schematic diagram; Figure 6 The residual unbalanced thrust distribution curve of each rock layer of the large-scale dumping deformation body; Figure 7 The centrifuge model schematic diagram of the large-scale dumping deformation body; Figure 8 The residual unbalanced thrust distribution curve of each rock layer in the centrifuge model of the large-scale dumping deformation body; In the figure: 1, key rock layer; 2, key rock layer thickness; 3, rock layer thickness; 4, rock layer inclination; 5, dumping-bending damage area; 6, dumping-sliding damage area. DETAILED DESCRIPTION

[0009] The application is further described below in conjunction with the accompanying drawings and examples Figures 1-8 The application is further described below in conjunction with the accompanying drawings and examples

[0010] The application is mainly aimed at large-scale dumping deformation bodies, and is particularly suitable for large-scale dumping deformation bodies with soft and hard interbedded characteristics.

[0011] The corresponding technical flowchart of the application can be seen from Figure 1 .

[0012] Step 1: Comprehensive geological survey of large-scale dumping deformation bodies is carried out, mainly collecting geological structure, rock stratum lithology, rock stratum dip angle 4, rock stratum thickness 3, etc.; indoor or field tests are carried out to determine the key physical and mechanical parameters of the rock stratum of the large-scale dumping deformation body, such as tensile strength, shear strength and compressive strength; the slope surface erosion damage phenomenon and range of the large-scale dumping deformation body, the rock stratum cracking characteristics are found out, and the dumping damage area of various rock strata is counted; and then the key engineering geological information of the large-scale dumping deformation body is obtained.

[0013] Preferably, in step 1, the geological survey work needs to comprehensively use satellite remote sensing, multi-angle unmanned aerial vehicle panoramic photography, field reconnaissance and various technical methods such as adit drilling, to realize three-dimensional and comprehensive survey analysis; the determination of the tensile and shear strength of the rock stratum is focused on, and the test method is mainly field direct shear test or indoor biaxial / three-axis test; for large-scale dumping deformation bodies significantly affected by rainfall or reservoir water level fluctuation, the saturated mechanical parameters and permeability characteristics of the rock stratum need to be determined in detail, and the precipitation law and reservoir water fluctuation characteristics of the area are found out.

[0014] Step 2: At least 6 drill holes are uniformly arranged at certain distances and elevations along the elevation direction of the large-scale dumping deformation body from the slope toe to the slope top, i.e. at least 2 drill holes are arranged in the slope toe, middle and top regions; in addition, the drill hole direction should be parallel to the rock stratum dip angle 4 direction, and then the RQD value, the distribution of the fracture surface and the distribution of the weak surface of the drill core are used to determine the fracture surface depth and morphological distribution law of the large-scale dumping deformation body; Preferably, in step 2, the core RQD is lower than 50% or decreases sharply at a certain depth, or there is a tensile fracture surface and a weak layer in the core, which can be used as a basis for identifying the fracture position of the large-scale dumping deformation body; after determining the fracture surface depth revealed by each drill hole, the spatial morphological diagram of the fracture surface, i.e. the fracture surface distribution map of the large-scale dumping deformation body, can be finally drawn by sequentially connecting.

[0015] Step 3: Based on the geological survey results of Step 1, if an embedded rock beam type rock layer with a relatively complete rock structure, thick rock layer, and high compressive, tensile, and shear strength is found in the large toppled deformation body, and this embedded rock beam type rock layer is distributed in the middle-front to middle-rear area of ​​the large toppled deformation body, then the area where the embedded rock beam type rock layer is located can be considered as the key embedded rock beam type rock layer of the large toppled deformation body. Preferably, in step 3, the thickness of the key rock strata embedded in the large-scale tilting deformed body is at least three times the thickness of the conventional rock strata; the thickness of the conventional rock strata is obtained by calculating the average thickness of the rock strata in the large-scale tilting deformed body.

[0016] Step 4: Based on the geological survey results in Step 1, if there are no embedded rock beams in the large-scale toppling deformation body and the rock strata have only one type of lithology, then the key rock strata for the gradual toppling type need to be determined by calculating the remaining unbalanced thrust of each rock stratum in the large-scale toppling deformation body. Step 5: If the rock strata are relatively intact and the rock strata are closely bonded, and there is no obvious erosion or hollowing damage to the rock strata at the toe of the large overturned deformed body, or no free surface is formed on the underside of a certain intact rock strata, then based on the fracture mechanics multi-element crack propagation theory and the superimposed stress type cantilever beam model, the theory for calculating the residual unbalanced thrust of each rock strata of the large overturned deformed body is improved, and the residual unbalanced thrust of each rock strata of the large overturned deformed body is obtained. Preferably, in steps 5-6, since the formation of the fracture surface of a large toppled deformed body is essentially caused by the propagation of internal rock strata fissures, and the rock strata fissures of the large toppled deformed body are under complex stress, the fissure propagation caused by bending-tension fracture of the rock strata within the large toppled deformed body is considered to be a multi-component composite fissure propagation. Based on the multi-component fissure propagation theory of fracture mechanics, the fracture toughness of the rock strata within the large toppled deformed body under multi-component complex stress is calculated. The specific process is as follows: See Figure 3 The rock strata fissures of large-scale overturned deformed bodies are decomposed into fissure propagation models under three basic loads: tension (normal stress), shear (shear stress), and bending (bending moment). The formulas for calculating the stress intensity factor of the three basic loads are shown in equations (1) and (2): (1) (2) In equations (1) to (2), Rock strata within a large toppling deformation caused by normal stress I Type Crack Intensity Factor; Rock strata within a large toppling deformation caused by shear stress II Type Crack Intensity Factor; This refers to the rock strata within the body that undergo large toppling deformation due to bending moment. I Type Crack Intensity Factor;F σ , F τ as well as F M These are the intensity factor coefficients; σ This represents the normal stress experienced by the rock strata within a large toppled deformation body. τ The resultant shear stress is the stress exerted on the rock strata fissures within a large toppled deformation body. M The bending moment exerted on the rock fissures within a large toppling deformation body. d The length of a single rock stratum fracture. m The thickness of a single rock layer; The stress intensity factor at the crack tip of the rock strata in a large toppling deformation body is equal to the superposition of the intensity factors under the above three basic loads. The compressive-shear fracture criterion of the rock strata in a large toppling deformation body under multiple complex stress states is shown in Equation (3): (3) In equation (3), K Ⅰc For the fracture toughness of rock strata within a large toppled deformation body. λ It represents the compressive-shear coefficient of the rock strata within a large toppling deformation body.

[0017] Preferably, in step 5, if the rock strata are relatively intact and tightly bonded, and there is no significant erosion or hollowing damage at the toe of the large toppling deformed body, and no free surface is formed below the intact rock strata, then the ideal physical calculation model of the large toppling deformed body can be simplified to: Figure 4 This model simplifies all rock layers of a large toppled deformable body into a superimposed, fractured cantilever beam under stress; see [link / reference]. Figure 4 Take the first large tilted deformed body j A detailed stress analysis was conducted on the rock strata, including the first... j The rock strata are mainly subjected to their own weight, as well as the normal and tangential forces generated by the compression and displacement with adjacent rock strata; subsequently, by combining equation (1), the first... j rock strata I Type Crack Intensity Factor and II Type-3 fracture intensity factor, see Equation (4) for details; (4) In equation (4), G j For the first j The self-weight of the rock mass above the fracture surface of the rock strata M Gj For the first j The bending moment generated by the self-weight of the rock strata on the fractures; d j and m j The firstj fracture width of the rock stratum and the thickness of the rock stratum; h j and h j+1 is the first j is the contact length of the rock stratum above the fracture surface and the upper and lower rock strata, c is the rock stratum bedding plane cohesion of the large-scale slump deformation body, φ is the rock stratum bedding plane internal friction angle of the large-scale slump deformation body, T j and T j+1 is the first j is the normal force (i.e. the residual unbalanced thrust) of the rock stratum above the fracture surface and the upper and lower rock strata, R j and R j+1 is the first j is the tangential force of the rock stratum above the fracture surface and the upper and lower rock strata, wherein R j = T j tan φ + ch j , R j+1 = T j+1 tan φ + ch j+1 ; α is the rock stratum dip angle 4; Preferably, in step 5, the simultaneous equations (3) and (4) can be used to obtain the residual unbalanced thrust of any rock stratum, as shown in equation (5); the residual unbalanced thrust of all rock strata of the large-scale slump deformation body can be obtained by iterative calculation of equation (5); (5) Referring to Figure 4 , Y j and Y j+1 is the first j is the distance from the equivalent action point of the normal force and the tangential force of the rock stratum to the fracture surface, wherein Y j = ηh j , Y j+1 = ηh j+1 , η ∈(0,1).

[0018] Step 6: If there is obvious erosion and hollowing damage to the rock strata at the toe of the large overturned deformed body or a free surface is formed on the underside of a certain intact rock strata, then based on the fracture mechanics multi-element crack propagation theory and the individual stress type cantilever beam model, the calculation theory of the residual unbalanced thrust of each rock stratum of the large overturned deformed body is improved, and then the residual unbalanced thrust of each rock stratum of the large overturned deformed body is obtained. Preferably, in step 6, the ideal physical calculation model of the large tilting deformable body is simplified to... Figure 5 This model simplifies all rock layers of a large toppled deformable body as a single, fractured cantilever beam under stress; see [link to model]. Figure 5 Take the first large tilted deformed body i A detailed stress analysis was conducted on the rock strata, including the first... i The rock strata are mainly subjected to their own weight, as well as the normal and tangential forces generated by the compression and displacement with adjacent rock strata; subsequently, by combining equation (1), the first... i rock strata I Type Crack Intensity Factor and II Type II fracture intensity factor, see equation (6) for details: (6) In equation (6), G i For the first i The self-weight of the rock mass above the fracture surface of the rock strata M Gi For the first i The bending moment generated by the self-weight of the rock strata on the fractures; d i and m i The first i The width of the fractures in the rock strata is related to the thickness of the rock strata; h i For the first i The contact length between the fracture surface of the rock stratum and the overlying rock stratum. T i For the first i The normal force (i.e., residual unbalanced thrust) acting on the rock strata above the fracture surface and the rock strata above it. R i For the first i The tangential force acting between the fracture surface of the rock stratum and the overlying rock stratum, among which R i = T i tan φ + ch i .

[0019] Preferably, in step 6, by combining equations (3) and (6), the remaining unbalanced thrust of any rock layer can be obtained, as detailed in equation (7); the remaining unbalanced thrust of all rock layers of the large toppling deformation body can be obtained by iterative calculation using equation (7): (7) See Figure 5 , Y i For the first i The distance from the fracture surface to the equivalent point of application of the normal and tangential forces acting on the rock strata, where Y i = ηh i , η ∈(0,1).

[0020] Step 7: Based on the calculation results of the remaining unbalanced thrust of each rock layer in Steps 5 and 6 for the large overturned deformation body, plot the distribution curve of the remaining unbalanced thrust rock elevation of the rock layers (e.g., Figure 6 As shown, the horizontal axis represents the rock stratum number, and the vertical axis represents the remaining unbalanced thrust. The peak area of ​​the remaining unbalanced force of each rock stratum is determined. At the same time, it is necessary to combine the geological survey results of step 1 to determine whether the peak area of ​​the remaining unbalanced thrust is located at the boundary between the toppling-bending failure area 5 and the toppling-slip failure area 6 of the large toppling deformation body. Based on this, the rock stratum in the peak area of ​​the remaining unbalanced thrust is considered to be the key rock stratum of the progressive toppling type of the large toppling deformation body.

[0021] Preferably, in step 7, the thickness of the progressively tilting key rock layer is at least 5 times the thickness of the conventional rock layer.

[0022] Example 1: Large tilting deformable model of centrifuge, such as Figure 7 As shown, during the model's failure process, a clear key rock layer phenomenon was observed. Specifically, after the failure of the 13th rock layer, the deformation of the large-scale toppling deformable body suddenly increased, and it became completely unstable. The fracture surface extended to the top of the slope. Therefore, the 13th rock layer can be considered the progressively toppling key rock layer of this large-scale toppling deformable body. The control failure surface of the large-scale toppling deformable body model is a broken line shape, with the angles between the front and rear sections and the horizontal plane being 40° and 60°, respectively. A total of 19 fractured rock layers remain on the failure surface. Furthermore, during the model's failure process, a clear free surface was observed at the lower part of the rock layer unit, and the rock layer at the toe of the slope was completely destroyed. Therefore, the method described in step 6 of this invention can be used to determine the progressively toppling key rock layer of the large-scale toppling deformable body model, thereby verifying the accuracy of the method for determining the key rock layer of the large-scale toppling deformable body.

[0023] The thickness of each unit rock layer of the large-scale slump deformation body is 4 cm, the slope angle and the unit rock layer angle are both 60°, the cohesion and internal friction angle between the unit rock layer surfaces are 33 kPa and 13° respectively, and the unit rock layer bulk density is 37.65 kN / m 3 The unit rock layer structure surface length is 0.5 cm, the strength factor coefficient of the unit rock layer is calculated according to the formula (1) and (2) of the application F σ=2.83、 F τ=1.56 and FM =1.50, the fracture toughness of the rock layer in the large-scale slump deformation body is taken as K Ⅰc =0.9 MPa m 1 / 2 , the compression-shear coefficient of the rock layer in the large-scale slump deformation body is taken as λ =1. Then, the residual unbalanced thrust of each unit rock layer is calculated according to the formula (7) of the application, and the calculation result is shown in Figure 8 It can be seen from Figure 8 that the residual unbalanced thrust of the large-scale slump deformation body gradually increases from the slope top to the slope foot, reaches the peak at the 13th unit rock layer, and then gradually decreases, so the 13th unit rock layer is determined as the key rock layer of the large-scale slump deformation body by the key rock layer determination method of the application, which is consistent with the centrifuge model test phenomenon, and the accuracy of the method of the application is proved.

[0024] The unmentioned part of the application is applicable to the prior art.

Claims

1. A method for determining key rock strata in a large toppled deformed body, characterized in that, The method includes the following steps: Step 1: Conduct a geological survey to obtain the geological structure, strike, dip and dip angle of the rock strata of the large-scale toppling deformation body, determine the lithology and thickness of the rock strata, determine the key engineering geological information of the large-scale toppling deformation body, including the physical and mechanical material parameters of the rock and soil, the phenomenon and extent of slope erosion and damage, the rock strata cracking and rock strata toppling failure areas of the large-scale toppling deformation body, and count the existing toppling and instability areas of various rock strata. Step 2: Along the elevation direction of the large overturned deformed body, at least 6 boreholes are evenly set from the toe of the slope to the top of the slope, that is, at least 2 boreholes are arranged in the toe, middle and top areas of the slope; in addition, the drilling direction is parallel to the dip angle of the rock strata. Then, the depth and morphological distribution of the fracture surface of the large overturned deformed body are determined based on the RQD value of the borehole core, the distribution of fracture surfaces and the distribution of weak surfaces. Step 3: Based on the geological survey results in Step 1, determine whether there is a thick embedded rock beam with a complete structure and significantly higher strength than other rock layers in the large toppled deformation body. At the same time, the embedded rock beam is located in the front to rear part of the toppled deformation body. If it exists, the area where the embedded rock beam is located is the key rock layer of the embedded rock beam type in the large toppled deformation body. Step 4: Based on the geological survey results of Step 1, if there are no embedded rock beams in the large-scale toppling deformation body and the rock strata are of a single type, then the key rock strata for gradual toppling need to be determined by calculating the remaining unbalanced thrust of each rock stratum in the large-scale toppling deformation body. Step 5: If the rock strata are intact and tightly bonded, and there is no obvious erosion or hollowing damage to the rock strata at the toe of the large overturned deformed body, or no free surface is formed on the underside of a certain intact rock strata, then the remaining unbalanced thrust of each rock stratum of the large overturned deformed body is calculated based on the multi-element crack propagation theory of fracture mechanics and the superimposed stress type cantilever beam model. Step 6: If there is obvious erosion and hollowing damage to the rock strata at the toe of the large overturned deformed body or a free surface is formed on the underside of a certain intact rock strata, the remaining unbalanced thrust of each rock stratum of the large overturned deformed body is calculated based on the multi-element fracture propagation theory of fracture mechanics and the cantilever beam model of individual stress type. Step 7: Based on the calculation results of the remaining unbalanced thrust of each rock layer in Step 5 or Step 6 for the large toppled deformation body, plot the distribution curve of the remaining unbalanced thrust of the rock layer along the elevation to determine the peak area of ​​the remaining unbalanced force of each rock layer; at the same time, combined with the geological survey results in Step 1, determine whether the peak area of ​​the remaining unbalanced thrust is located at the boundary between the toppling-bending failure area and the toppling-slip failure area of ​​the large toppled deformation body; if so, the rock layer in the peak area of ​​the remaining unbalanced thrust is considered to be the key rock layer of the gradual toppling type of the large toppled deformation body.

2. The method for determining key rock strata in a large toppled deformed body according to claim 1, characterized in that, In step 2, if the core RQD is below 50% or drops sharply at a certain depth, or if there are tensile fracture surfaces and weak layers in the core, it serves as the basis for identifying the fracture location of large overturned deformed bodies. After determining the depth of the fracture surface exposed by each borehole, a spatial morphology diagram of the fracture surface is finally drawn by connecting them sequentially.

3. The method for determining key rock strata in a large toppled deformed body according to claim 1, characterized in that, If the rock strata are intact and tightly packed, and there is no significant erosion or hollowing damage at the toe of the large toppling deformation body, and no free surface is formed below the intact rock strata, then the remaining unbalanced thrust of all rock strata in the large toppling deformation body can be calculated using the following formula: ， in ，F σ、 F τ and FM These are the intensity factor coefficients; K Ⅰc For the fracture toughness of rock strata within a large toppled deformation body. λ The compressive-shear coefficient of the rock strata within a large toppling deformation body; G j For the first j The self-weight of the rock mass above the fracture surface of the rock strata M Gj For the first j The bending moment generated by the self-weight of the rock strata on the fractures; d j and m j The first j The width of the fractures in the rock strata is related to the thickness of the rock strata; h j and h j+1 For the first j The length of contact between the fracture surface of the rock stratum and the rock strata above and below it. c For the cohesion of the rock strata in a large toppled deformed body, φ The internal friction angle of the rock strata in a large toppled deformed body. T j and T j+1 The first j The normal force acting between the rock stratum above the fracture surface and the rock strata above and below it. η ∈(0,1), α The dip angle of the rock strata; If there is significant erosion and hollowing damage to the rock strata at the toe of a large toppling deformed body, or if a free surface is formed beneath a certain intact rock stratum, the remaining unbalanced thrust of all rock strata in the large toppling deformed body can be calculated using the following formula: ， in, G i For the first i The self-weight of the rock mass above the fracture surface of the rock strata M Gi For the first i The bending moment generated by the self-weight of the rock strata on the fractures; d i and m i The first i The width of the fractures in the rock strata is related to the thickness of the rock strata; h i For the first i The contact length between the fracture surface of the rock stratum and the overlying rock stratum. T i For the first i The normal force (i.e., residual unbalanced thrust) acting on the rock strata above the fracture surface and the rock strata above it.

4. The method for determining key rock strata in a large toppled deformed body according to claim 1, characterized in that, The thickness of the key rock strata in the embedded rock beam type of the large-scale toppling deformed body is at least 3 times the thickness of the conventional rock strata, and the thickness of the key rock strata in the progressive toppling type is at least 5 times the thickness of the conventional rock strata; the thickness of the conventional rock strata is obtained by calculating the average thickness of the rock strata in the large-scale toppling deformed body.

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