Slope dynamic safety coefficient calculation method based on large rock mass shear displacement

Abstract

The invention discloses a slope dynamic safety coefficient calculation method based on large rock mass shear displacement. The slope dynamic safety coefficient calculation method comprises the following steps: establishing a relational expression between shear stress tau and a rock interface total area S; constructing a shear constitutive model of the small-size rock sample in combination with a classical structural surface shear stress-displacement curve and Weibull distribution; converting parameters in the shear constitutive model of the small-size rock sample into corresponding large rock mass parameters, and constructing a large rock mass shear constitutive model; and the real-time shear displacement of the slip mass is substituted into the large rock mass shear constitutive model, and the dynamic safety coefficient of the slope is obtained. According to the method, a new large rock mass shear constitutive model is constructed, and based on an expression of the large rock mass shear constitutive model, the shear displacement of the sliding mass is substituted into the large rock mass shear constitutive model, so that the shear displacement of the rock mass can be used for calculating the dynamic safety coefficient of the slope.

Description

Technical Field

[0001] The invention relates to the technical field of rock structural surface constitutive models, and in particular to a method for calculating the dynamic safety factor of a slope based on shear displacement of a large rock mass. Background Art

[0002] Landslides are a type of geological disaster that frequently occurs in human society and can cause great damage to human life and social economy. Under the influence of long-term gravity and external factors such as rainfall and earthquakes,

[0003] The sliding body in the slope will undergo shear failure along the potential sliding surface, thus forming a large-scale landslide disaster, such as mountain debris flow and high-speed debris flow landslide. At present, there are many research methods on slope stability, such as limit equilibrium method, minimum potential energy method and numerical simulation method. The role of these methods in slope stability research has been widely recognized by engineers, and some remarkable research results have been achieved. However, the slope stability calculated by these theories is static. However, as the shear displacement of the sliding body on the sliding surface increases, the rock on the sliding surface undergoes shear deformation and failure, that is, the shear strength of the rock will change nonlinearly with the increase of shear displacement. Existing theories ignore the influence of the shear characteristics of the sliding body on the slope stability.

[0004] As the sliding body continues to slowly shear and slide on the sliding surface, the originally intact rock interface on the sliding surface will be damaged, and the anti-sliding force on the sliding body will decrease. Therefore, the stability of the slope will change dynamically with the increase of the shear displacement of the landslide, and most of the existing theoretical methods such as the limit equilibrium method ignore this point, which is not conducive to monitoring the dynamic safety factor of the slope. Summary of the invention

[0005] Based on this, the purpose of the present invention is to provide a method for calculating the dynamic safety factor of the slope based on the shear displacement of large rock masses, bringing the shear displacement of the sliding body into the shear constitutive model of the large rock mass, so that the shear displacement of the rock mass can be used to calculate the dynamic safety factor of the slope.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for calculating the dynamic safety factor of a slope based on shear displacement of a large rock mass, which comprises the following steps:

[0008] Step S1, establishing a relationship between shear stress τ and the total area S of the rock interface;

[0009]

[0010] Among them, τ represents the shear stress, that is, the average shear strength per unit area on the rock interface, S represents the total area of ​​the rock interface, and τ u and τ d They represent the shear strength of the undamaged unit and the damaged unit, respectively, S u and S d represent the total area of ​​undamaged cells and damaged cells respectively;

[0011] Step S2, constructing a shear constitutive model of a small-sized rock sample by combining the classical structural plane shear stress-displacement curve and Weibull distribution;

[0012] Step S3, converting the parameters in the shear constitutive model of the small-sized rock sample into corresponding large-scale rock mass parameters, and constructing a shear constitutive model of the large-scale rock mass;

[0013] Step S4: Divide the sliding body on the slope into multiple strips and blocks, and obtain the dynamic safety factor of the slope based on the safety factor calculation formula of the slope.

[0014] In one embodiment, the steps of step S2 include:

[0015] Step S21: Introduce the damage concept D, where D represents the damage to the rock interface during the shearing process and is the damaged unit area S d The ratio of the total rock interface area S is:

[0016] D=S d / S (2);

[0017] Step S22, combining formula (1) and formula (2), dividing both sides of formula (1) by S, and obtaining shear stress τ = τ u (1-D)+τ d D(3);

[0018] Step S23: Analyze the shear stress-displacement curve of the classical structural surface, and do not destroy the unit shear strength τ u Satisfy τ u =ku(4), combining formula (3) and formula (4), we can get τ = ku(1-D) + Dτ d (5); where k represents the slope of the elastic phase of the shear stress-displacement curve of the classic structural surface, and u represents the shear displacement;

[0019] Step S24: Use Weibull distribution to describe the number of damaged units. The function expression of Weibull distribution is: u k The displacement value corresponding to the boundary point between the elastic stage and the plastic yield stage in the shear stress-displacement curve is represented by the damage D, which is the integral of the Weibull distribution function with the shear displacement as the upper and lower limits:

[0020]

[0021] Step S25, substituting formula (7) into formula (5), the shear constitutive model of the small-sized rock sample can be obtained:

[0022]

[0023] In one embodiment, after step S25, the method further includes:

[0024] Step S26: Determine the parameter F in the shear constitutive model of the small-sized rock sample. 1 、F 2 .

[0025] In one embodiment, the specific steps of step S26 are as follows:

[0026] Based on the peak point of the shear stress-displacement curve (u f , τ f ), and the derivative of the peak point is 0, we can get:

[0027] The peak point (u f , τ f ) also satisfies formula (8). Combining formulas (8) and (9), we can obtain the parameter F in the shear constitutive model of small-size rock specimens: 1 、F 2 The calculation formula is:

[0028]

[0029] In one embodiment, the steps of step S3 include:

[0030] Step S31, the slope k is expressed by the shear modulus G of the rock mass, and the relationship between the slope k and the shear modulus G of the rock mass satisfies:

[0031] Where A represents the reduction factor, and the value range of A is 0 to 1. interface represents the length of the shear surface, ε τ represents shear strain;

[0032] Step S32: The shear modulus G can be expressed by the elastic modulus E. The relationship between the shear modulus G and the elastic modulus E satisfies:

[0033] Where E represents the elastic modulus of the rock mass, and μ represents the Poisson’s ratio of the rock mass;

[0034] Step S33, substituting formula (12) and formula (11) into formula (8), the shear constitutive model of large rock mass can be obtained:

[0035]

[0036] In one embodiment, after step S33, the method further includes:

[0037] Step S34: Determine the parameter F in the shear constitutive model of the large rock mass. 1 、F 2 .

[0038] In one embodiment, the specific steps of step S34 are as follows:

[0039] Based on the Mohr-Coulomb criterion, the maximum shear resistance of large rock mass satisfies:

[0040] Where σ represents the normal pressure on the sliding surface, represents the internal friction angle of the rock mass, and c represents the cohesion of the rock mass;

[0041] Substituting formula (11), formula (12) and formula (13) into formula (10), we can obtain the parameter F in the shear constitutive model of large rock mass: 1 、F 2 The calculation formula is:

[0042]

[0043] In one embodiment, the specific steps of step S4 are as follows:

[0044] The sliding body on the slope is divided into a plurality of cuboid blocks with a cross-sectional shape approximately rectangular;

[0045] The weight of block i is known to be W i , the angle between bar i and the horizontal is α i , then the sliding force generated by block i is

[0046] F slide-force =W i sinα i (16)

[0047] The sliding force on block i is

[0048] F antislide-force =τ i L i (17)

[0049] Among them, L i Indicates the bottom length of bar i;

[0050] The safety factor calculation formula based on the slope is the sum of the anti-sliding forces on all strips divided by the sum of the sliding forces. Combining formula (15), formula (16) and formula (17), the dynamic safety factor F of the slope can be obtained: s The calculation expression is

[0051]

[0052] ; The subscript i of each parameter represents the parameter value corresponding to the i-th block.

[0053] In one embodiment, after step S4, the following step is also included:

[0054] Step S5, judging whether the dynamic safety factor of the slope is greater than 1. When the dynamic safety factor of the slope is greater than 1, the slope is in a stable state; when the dynamic safety factor of the slope is not greater than 1, the slope is in an unstable state.

[0055] In summary, the present invention constructs a new shear constitutive model of large rock mass, and based on the expression of the shear constitutive model of large rock mass, brings the shear displacement of the sliding body into the shear constitutive model of large rock mass, so that the shear displacement of the rock mass can be used to calculate the dynamic safety factor of the slope. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 A schematic diagram of the structure of a rock interface unit in a damaged state provided by an embodiment of the present invention;

[0057] Figure 2 A schematic diagram of a curve showing damage accumulation during shearing provided by an embodiment of the present invention;

[0058] Figure 3 A schematic diagram of a curve showing a rock unit failure process during a shearing process provided by an embodiment of the present invention;

[0059] Figure 4 A schematic diagram of data comparison between the shear constitutive model of a small-sized rock sample provided by an embodiment of the present invention and experimental data;

[0060] Figure 5 A schematic flow chart of a method for calculating the dynamic safety factor of a slope based on large rock mass shear displacement provided by an embodiment of the present invention;

[0061] Figure 6 A schematic diagram of a structure in which an irregular sliding body provided in an embodiment of the present invention is divided into a plurality of strips with a cross-sectional shape approximately rectangular;

[0062] Figure 7 A schematic diagram of the structure of the angle between the strip and the horizontal provided in an embodiment of the present invention;

[0063] Figure 8 A schematic diagram of the structure of parameters and dimensions of an assumed slope model provided by an embodiment of the present invention;

[0064] Fig. 9 A schematic diagram of a slope safety factor obtained based on the limit equilibrium method provided in an embodiment of the present invention;

[0065] Fig.10 A schematic diagram of a structure in which a sliding body provided in an embodiment of the present invention is divided into a plurality of strips;

[0066] Fig.11 A schematic diagram of curves showing different shear curves for different strips provided in an embodiment of the present invention;

[0067] Fig.12 A schematic diagram of a curve showing the change in slope safety factor with shear displacement provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0068] In order to further understand the features, technical means, specific objectives and functions of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0069] Figure 5 is a flow chart of a method for calculating the dynamic safety factor of a slope based on large rock mass shear displacement provided by an embodiment of the present invention, such as Figure 5 As shown in FIG. 1 , the slope dynamic safety factor calculation method based on large rock mass shear displacement specifically includes the following steps:

[0070] Step S1, establish the relationship between shear stress τ and the total area S of the rock interface:

[0071]

[0072] Among them, τ represents the shear stress, that is, the average shear strength per unit area on the rock interface, S represents the total area of ​​the rock interface, and τ u and τ d They represent the shear strength of the undamaged unit and the damaged unit, respectively, S u and S d Represent the total area of ​​undamaged units and damaged units respectively; the rock interface includes undamaged units and damaged units.

[0073] The damage of rock units on the shear interface is the main reason for the deterioration of rock materials during the shear process. Therefore, the rock units on the shear interface can be divided into two parts: damaged and undamaged, such as Figure 1 As the shearing behavior continues, more and more units on the rock interface change from undamaged to damaged.

[0074] Step S2: Construct a shear constitutive model of small-sized rock specimens by combining the classical structural plane shear stress-displacement curve and Weibull distribution.

[0075] The specific steps of step S2 include:

[0076] Step S21, introduce the damage concept D, D represents the damage generated on the rock interface during the shearing process, such as Figure 2 As shown, the damage D is specifically the damaged unit area S d The ratio of the total rock interface area S is

[0077] D=S d / S (2);

[0078] Step S22, combining formula (1) and formula (2), dividing both sides of formula (1) by S, and obtaining shear stress τ = τ u (1-D)+τ d D(3);

[0079] Step S23, analyzing the shear stress-displacement curve of the classical structural surface, which includes an elastic stage (OA), a plastic yield stage (AB), a strain softening stage (BC) and a residual stage (CD). The intersection of the elastic stage and the plastic yield stage is the yield point. The shear stress in the elastic stage is The shear displacement curve shows a linear or approximately linear change, that is, damage has not occurred yet. In the plastic yield stage, the relationship between shear stress and shear displacement has obviously deviated from the straight line, indicating that the rock material has been damaged at this stage. The starting point of the damage is defined at the yield point; therefore, the unit shear strength τ is not destroyed. u satisfy

[0080] τ u =ku (4),

[0081] Combining formula (3) and formula (4), we can get τ=ku(1-D)+Dτ d (5);

[0082] Where k represents the slope of the elastic stage of the shear stress-displacement curve of the classic structural surface, u represents the shear displacement; damage D represents the ratio of the damaged unit area to the total area of ​​the rock interface. When D = 1, the rock interface is in a completely damaged state, at which τ = τ d , corresponding to the residual stage of the shear stress-displacement curve, such as Figure 2 and Figure 3 shown.

[0083] Step S24: Use Weibull distribution to describe the number of damaged units. The function expression of Weibull distribution is: u kIt represents the displacement value corresponding to the boundary point between the elastic stage and the plastic yield stage in the shear stress-displacement curve. Then the damage D is the integral of the Weibull distribution function with the shear displacement as the upper and lower limits.

[0084]

[0085] Step S25, substituting formula (7) into formula (5), the shear constitutive model of the small-sized rock sample can be obtained:

[0086]

[0087] Furthermore, after step S25, the method further includes:

[0088] Step S26: Determine the parameter F in the shear constitutive model of the small-sized rock sample. 1 、F 2 .

[0089] The specific steps of step S26 are as follows:

[0090] Based on the peak point of the shear stress-displacement curve (u f , τ f ), and the derivative of the peak point is 0, we can get:

[0091] The peak point (u f , τ f ) also satisfies formula (8). Combining formulas (8) and (9), we can obtain the parameter F in the shear constitutive model of small-sized rock specimens: 1 、F 2 The calculation formula is:

[0092]

[0093] The shear constitutive model of the small-sized rock sample constructed in the present invention is compared with the actual shear test data, and the correlation coefficient R 2 As an indicator for evaluating the accuracy of the model, R 2 The value range of R is between 0 and 1. 2 The closer it is to 1, the higher the accuracy of the model.

[0094] Please refer to Figure 4 , Figure 4 The schematic diagram shows the comparison between the shear deformation curve calculated by the shear constitutive model of small-sized rock specimens and the actual shear deformation results. The actual shear constitutive relationship is in good agreement with the predicted curve of the shear constitutive model of small-sized rock specimens. From the results, the two are quite consistent, among which the correlation coefficient R 2They are all greater than 0.95, which is quite significant. The shear constitutive model of small-sized rock specimens can fully simulate the linear and nonlinear behaviors in the shear deformation of the structural surface.

[0095] Step S3, converting the parameters in the shear constitutive model of the small-sized rock sample into the corresponding large-scale rock mass parameters, and constructing the shear constitutive model of the large-scale rock mass; a shear constitutive model of the small-sized rock sample corresponding to the shear stress-displacement curve constructed in step S2. Due to the existence of size effect, the shear constitutive model of the small-sized rock sample cannot be applied to the large-scale rock mass model. It is necessary to convert the parameters in the shear constitutive model of the small-sized rock sample into the parameters of the large rock mass such as the slope, so as to construct the shear constitutive model of the large rock mass.

[0096] The specific steps of step S3 include:

[0097] Step S31: In the shear stress-displacement curve, k represents the shear stress increase rate per unit distance, in units of Pa / m. In actual rock mass, the shear modulus G represents the shear stress increase rate per unit strain.

[0098] Therefore, the slope k is expressed by the shear modulus G of the rock mass. The relationship between the slope k and the shear modulus G of the rock mass satisfies:

[0099]

[0100] Where A represents the reduction coefficient, and the value range of A is 0 to 1. Due to the initial voids and microcracks inside the rock sample, the k obtained in the test curve will be smaller than the shear modulus G of the ideal elastic body. Therefore, the parameter A is introduced to reduce the shear modulus G. interface represents the length of the shear surface, ε τ represents shear strain.

[0101] Step S32: The shear modulus G can be expressed by the elastic modulus E. The relationship between the shear modulus G and the elastic modulus E satisfies:

[0102]

[0103] Among them, E represents the elastic modulus of the rock mass, and μ represents the Poisson's ratio of the rock mass.

[0104] Step S33, substituting formula (12) and formula (11) into formula (8), the shear constitutive model of large rock mass can be obtained:

[0105]

[0106] Furthermore, after step S33, the method further includes:

[0107] Step S34: Determine the parameter F in the shear constitutive model of the large rock mass. 1 、F 2 .

[0108] The specific steps of step S34 are as follows:

[0109] Based on the Mohr-Coulomb criterion, the maximum shear resistance of large rock mass is τ f satisfy:

[0110] Where σ represents the normal pressure on the sliding surface, represents the internal friction angle of the rock mass, and c represents the cohesion of the rock mass;

[0111] In the shear constitutive model of small-sized rock specimens, the parameter F can be solved by the shear stress-displacement curve. 1 、F 2 However, a large rock mass such as a slope cannot be directly subjected to shear tests. In the shear constitutive model of large rock mass, the maximum shear resistance of the large rock mass can be calculated using the Mohr-Coulomb criterion.

[0112] Substituting formula (11), formula (13) and formula (14) into formula (10), we can obtain the parameter F in the shear constitutive model of large rock mass: 1 、F 2 The calculation formula is:

[0113]

[0114] Step S4: Bring the shear displacement of the sliding body into the shear constitutive model of the large rock mass to obtain the dynamic safety factor F of the slope s .

[0115] In step S3, the shear constitutive model of large rock mass has been obtained. In this model, as the shear displacement of the sliding body increases, the anti-sliding force provided by the sliding surface to the sliding body will also change. However, the shear constitutive model of large rock mass is derived based on the shear constitutive model of indoor tests, and the samples used in indoor shear tests are all regular rectangular specimens, such as Figure 1 shown.

[0116] However, if Figure 6 As shown in the figure, the sliding body is a large rock mass with an irregular shape compared to a small rectangular rock sample. This results in different normal loads at different positions on the sliding surface of the large rock mass. Therefore, it is necessary to divide the irregular sliding body into multiple rectangular blocks. The shear displacement of the sliding body is brought into the shear constitutive model of the large rock mass, and the sliding body on the slope is divided into multiple blocks. Based on the safety factor calculation formula of the slope, the dynamic safety factor of the slope F is obtained. s .

[0117] The specific steps of step S4 include:

[0118] Step S41, dividing the sliding body on the slope into a plurality of cuboid blocks with a cross-sectional shape approximately rectangular;

[0119] Step S42: The weight of the known block i is W i , the angle between bar i and the horizontal is α i ,like Figure 7 As shown, the sliding force generated by block i is

[0120] F slide-force =W i sinα i (16)

[0121] The sliding force on block i is

[0122] F antislide-force =τ i L i (17)

[0123] Among them, L i Indicates the bottom length of bar i;

[0124] Step S43: Bring the shear displacement of the sliding body into the shear constitutive model of the large rock mass. The safety factor calculation formula of the slope is the sum of the anti-sliding forces on all blocks divided by the sum of the sliding forces. Combining formulas (15), (16) and (17), the dynamic safety factor F of the slope can be obtained: s The calculation expression is ;

[0125] The subscript i of each parameter represents the parameter value corresponding to the i-th block.

[0126] Furthermore, after step S4, the method further includes:

[0127] Step S5, determine whether the dynamic safety factor of the slope is greater than 1. When the dynamic safety factor of the slope is greater than 1, the slope is in a stable state; when the dynamic safety factor of the slope is not greater than 1, the slope is in an unstable state and a landslide warning signal is issued.

[0128] The shear displacement of the rock mass is the sliding displacement of the rock mass. As the shear displacement changes, the shear force will also change. Formula u represents the shear displacement, that is, the sliding displacement. The shear constitutive model of large rock mass includes shear displacement, that is, sliding displacement. When the safety factor of the slope is greater than 1, that is, the sliding force of the sliding body is less than the anti-sliding force, the slope is in a stable state. When the safety factor of the slope is equal to 1, that is, the sliding force of the sliding body is equal to the anti-sliding force, the slope is in a critically stable state. When the safety factor is less than 1, it means that the sliding force of the sliding body is greater than the anti-sliding force, and the slope is in an unstable state. The shear displacement generated by the sliding body can be captured by an external displacement monitoring device, and the shear displacement can be brought into the dynamic safety factor calculation expression of the slope. If it is found that the slope safety factor decreases to 1 or less than 1 with the increase of shear displacement, a landslide warning can be issued.

[0129] In summary, the present invention constructs a new large-scale rock mass shear constitutive model, and based on the expression of the large-scale rock mass shear constitutive model, brings the shear displacement of the sliding body into the large-scale rock mass shear constitutive model, so that the shear displacement of the rock mass can be used to calculate the dynamic safety factor of the slope. In actual engineering, the shear displacement of the rock mass can be determined by the displacement monitoring equipment installed inside the rock mass, and the slope safety factor can be calculated by the displacement to determine whether the slope is in a stable state. The method of calculating the dynamic safety factor of the slope of the invention effectively improves the early warning efficiency of the slope and has important engineering significance.

[0130] Compared with the existing shear constitutive model, the invention has strong repeatability and can be applied to various geological rock masses such as field slopes, open-pit mines, and large dams. It has a very wide range of applications and can serve as a reference for the sliding shear characteristics of various engineering rock and soil.

[0131] For example, for a large slope, engineers can obtain the landslide displacement and landslide rate of the slope through the installed displacement monitor. Bringing these data into the slope dynamic safety factor calculation formula based on large rock mass shear displacement of the present invention can help engineers better judge whether the slope is about to be destroyed, and then cooperate with landslide warning to effectively improve the stability of the slope or organize personnel evacuation through grouting, anchoring, etc.

[0132] In order to intuitively and conveniently verify the adaptability and rationality of the proposed method for calculating the dynamic safety factor of large rock mass shear displacement slopes, Figure 6 and Figure 8 As shown in the figure, it is assumed that there is a large slope with a slope angle of 45° and rock mass γ = 26Kn / m 3 , slope height H = 300m, adhesion c = 4.14MPa, internal friction angle The Poisson's ratio μ is 0.21. The calculation method of the dynamic safety factor of this large slope is used as an example for verification.

[0133] like Fig. 9 As shown in the figure, the static safety factor of the slope calculated using the traditional limit equilibrium method is 5.42.

[0134] The calculation method of the dynamic safety factor of the slope of the present invention first divides the potential sliding body into multiple strips, such as Fig.10 As shown in the figure, each bar has different sizes and the pressure acting on the sliding surface is also different. By combining formula (13), formula (14) and formula (15), the shear constitutive curve of each bar can be obtained respectively, as shown in Fig.11 shown.

[0135] Substituting formula (13), formula (14) and formula (15) into the dynamic safety factor F of the slope s After calculating the expression, we can get the curve of slope safety factor changing with sliding body shear displacement, such as Fig.12 shown.

[0136] The slope safety factor changes with the shear displacement of the sliding body as shown in Fig.12 As shown. Fig.12 In the figure, when the shear displacement of the slope reaches a peak value of 0.595m, the safety factor reaches a maximum value of 4.98. The slope safety factor calculated based on the limit equilibrium method is 5.42. The difference between the calculation method of the present invention and the calculation result of the limit equilibrium method is (5.42-4.98) / 5.42=8.12%. The main reason for this phenomenon is that the slope safety factor calculated by the limit equilibrium method is a static safety factor. The limit equilibrium method ideally assumes that the shear strength at every point on the sliding surface reaches the maximum value. Fig.11 It can be seen that when the shear displacement reaches the maximum value of 0.595m, many models in the 59 shear constitutive curves have not yet reached the peak or have entered the residual strength stage. Therefore, the slope safety factor calculated based on the shear displacement will be smaller than the calculation result of the limit equilibrium method, which has a higher early warning efficiency and can avoid unknown risks in time, thereby carrying out effective support and organizing personnel evacuation.

[0137] The above-described embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A method for calculating the dynamic safety factor of a slope based on shear displacement of a large rock mass, characterized in that: The steps include: Step S1, establishing a relationship between shear stress τ and the total area S of the rock interface; Among them, τ represents the shear stress, that is, the average shear strength per unit area on the rock interface, S represents the total area of ​​the rock interface, and τ u and τ d They represent the shear strength of the undamaged unit and the damaged unit, respectively, S u and S d represent the total area of ​​undamaged cells and damaged cells respectively; Step S2, constructing a shear constitutive model of a small-sized rock sample by combining the classical structural plane shear stress-displacement curve and Weibull distribution; Step S3, converting the parameters in the shear constitutive model of the small-sized rock sample into corresponding large-scale rock mass parameters, and constructing a shear constitutive model of the large-scale rock mass; Step S4: Bring the shear displacement of the sliding body into the shear constitutive model of the large rock mass to obtain the dynamic safety factor of the slope.

2. The method for calculating the dynamic safety factor of slope based on large rock mass shear displacement according to claim 1 is characterized in that: The steps of step S2 include: Step S21: Introduce the damage concept D, where D represents the damage to the rock interface during the shearing process and is the damaged unit area S d The ratio of the total rock interface area S is: D=S d / S (2); Step S22, combining formula (1) and formula (2), dividing both sides of formula (1) by S, and obtaining shear stress τ = τ u (1-D)+τ d D(3); Step S23: Analyze the shear stress-displacement curve of the classical structural surface, and do not destroy the unit shear strength τ u Satisfy τ u =ku(4), combining formula (3) and formula (4), we can get τ = ku(1-D) + Dτ d (5); where k represents the slope of the elastic phase of the shear stress-displacement curve of the classic structural surface, and u represents the shear displacement; Step S24: Use Weibull distribution to describe the number of damaged units, where the function expression of Weibull distribution is: u k The displacement value corresponding to the boundary point between the elastic stage and the plastic yield stage in the shear stress-displacement curve is represented. The damage D is the integral of the Weibull distribution function with the shear displacement as the upper and lower limits: Step S25, substituting formula (7) into formula (5), the shear constitutive model of the small-sized rock sample can be obtained:

3. The method for calculating the dynamic safety factor of slope based on large rock mass shear displacement according to claim 2 is characterized in that: After step S25, the method further includes: Step S26, determining parameters F1 and F2 in the shear constitutive model of the small-sized rock sample.

4. The method for calculating the dynamic safety factor of slope based on large rock mass shear displacement according to claim 3 is characterized in that: The specific steps of step S26 are as follows: Based on the peak point of the shear stress-displacement curve (u f , τ f ), and the derivative of the peak point is 0, we can get: The peak point (u f , τ f ) also satisfies formula (8). Combining formulas (8) and (9), we can obtain the calculation formulas of parameters F1 and F2 in the shear constitutive model of small-sized rock specimens:

5. The method for calculating the dynamic safety factor of slope based on large rock mass shear displacement according to claim 4 is characterized in that: The steps of step S3 include: Step S31, the slope k is expressed by the shear modulus G of the rock mass, and the relationship between the slope k and the shear modulus G of the rock mass satisfies: Where A represents the reduction factor, and the value range of A is 0 to 1. interface represents the length of the shear surface, ε τ represents shear strain; Step S32: The shear modulus G can be expressed by the elastic modulus E. The relationship between the shear modulus G and the elastic modulus E satisfies: Where E represents the elastic modulus of the rock mass, and μ represents the Poisson’s ratio of the rock mass; Step S33, substituting formula (12) and formula (11) into formula (8), the shear constitutive model of large rock mass can be obtained:

6. The method for calculating the dynamic safety factor of slope based on large rock mass shear displacement according to claim 5, characterized in that: After step S33, the method further includes: Step S34, determining parameters F1 and F2 in the shear constitutive model of the large rock mass.

7. The method for calculating the dynamic safety factor of slope based on large rock mass shear displacement according to claim 6, characterized in that: The specific steps of step S34 are as follows: Based on the Mohr-Coulomb criterion, the maximum shear resistance of large rock mass satisfies: Where σ represents the normal pressure on the sliding surface, represents the internal friction angle of the rock mass, and c represents the cohesion of the rock mass; Substituting formula (11), formula (12) and formula (13) into formula (10), we can obtain the calculation formulas of parameters F1 and F2 in the shear constitutive model of large rock mass:

8. The method for calculating the dynamic safety factor of slope based on large rock mass shear displacement according to claim 7, characterized in that: The specific steps of step S4 are as follows: The sliding body on the slope is divided into a plurality of cuboid blocks with a cross-sectional shape approximately rectangular; The weight of block i is known to be W i , the angle between bar i and the horizontal is α i , then the sliding force generated by block i is F slide-force =W i sinα i (16), The sliding force on block i is F antislide-force =t i L i (17), Among them, L i Indicates the bottom length of bar i; The shear displacement of the sliding body is introduced into the shear constitutive model of the large rock mass. The safety factor of the slope is calculated based on the formula of the sum of the anti-sliding forces on all blocks divided by the sum of the sliding forces. Combining formulas (15), (16) and (17), the dynamic safety factor of the slope F can be obtained: s The calculation expression is ； The subscript i of each parameter represents the parameter value corresponding to the i-th block.

9. The method for calculating the dynamic safety factor of slope based on large rock mass shear displacement according to claim 1, characterized in that: After step S4, the following steps are also included: Step S5, judging whether the dynamic safety factor of the slope is greater than 1. When the dynamic safety factor of the slope is greater than 1, the slope is in a stable state; when the dynamic safety factor of the slope is not greater than 1, the slope is in an unstable state.

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