Method for obtaining shear strength of dissimilar structural plane under freeze-thaw environment

Abstract

The present application relates to the technical field of rock wall structure surface shear strength detection, and particularly relates to a method for obtaining shear strength of anisotropic structure surface under freeze-thaw environment. The method comprises: obtaining first rock wall strength and second rock wall strength of upper structure surface and lower structure surface under different freeze-thaw times, and then obtaining upper rock wall strength and lower rock wall strength; obtaining freeze-thaw composite rock wall strength based on the upper rock wall strength and the lower rock wall strength; obtaining freeze-thaw roughness coefficient and freeze-thaw basic friction angle of the anisotropic structure surface under different freeze-thaw times; obtaining freeze-thaw friction angle increment by using the freeze-thaw composite rock wall strength, the freeze-thaw roughness coefficient and the normal stress of the anisotropic structure surface; and calculating the shear strength model of the freeze-thaw anisotropic structure surface based on the freeze-thaw friction angle increment and the freeze-thaw basic friction angle. The present application considers the influence of freeze-thaw environment on the shear strength of the anisotropic structure surface, and can accurately obtain the shear strength of the anisotropic structure surface under freeze-thaw condition.

Description

Technical Field

[0001] This invention relates to the field of shear strength testing technology for rock wall structural surfaces, and specifically to a method for obtaining the shear strength of anisotropic structural surfaces under freeze-thaw conditions. Background Technology

[0002] Rock masses are composed of rock blocks and structural planes. The presence of structural planes significantly reduces the strength of the rock mass. Structural planes become the weakest points within the rock mass and are key factors controlling its mechanical properties. In practical engineering, rock masses commonly experience shear failure along structural planes (i.e., structural plane shear-type disasters). Examples include static disasters such as slope instability and slippage under low stress and dam foundation slippage, and dynamic impact disasters such as rock bursts caused by structural plane slippage and earthquakes caused by fault slippage under high stress. To ensure the safety and stability of large-scale rock mass engineering projects (such as water conservancy and hydropower, deep coal mines, nuclear waste treatment, oil and gas storage, and CO2 geological sequestration), the shear strength of the structural planes of the rock walls is crucial.

[0003] The shear strength of structural surfaces is a core parameter affecting the stability of fractured rock mass engineering. It is mainly controlled by factors such as the roughness of the structural surface, the rock wall strength of the structural surface, the normal stress, and the basic friction angle between the upper and lower structural surfaces. Existing methods for obtaining the shear strength of structural surfaces mainly involve obtaining the compressive-shear failure mechanism of the structural surfaces under normal conditions. Most of these methods fail to fully consider the inconsistency of mechanical properties between the upper and lower structural surfaces, i.e., the different material composition of the upper structural surface. They neglect the influence of the difference in mechanical properties between the upper and lower structural surfaces on the shear strength of the anisotropic structural surfaces. At the same time, freeze-thaw cycles are a key factor that must be considered in the construction and operation of rock mass engineering in cold regions. Therefore, it is necessary to consider the actual mechanical properties of the upper and lower structural surfaces as well as the shear strength of the structural surfaces under freeze-thaw conditions. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a method for obtaining the shear strength of anisotropic structural surfaces under freeze-thaw conditions. The specific technical solution adopted is as follows:

[0005] One embodiment of the present invention provides a method for obtaining the shear strength of anisotropic structural surfaces under freeze-thaw conditions, the method mainly comprising:

[0006] Construct an experimental upper and lower structural surface of a preset size; obtain the first rock wall strength and the second rock wall strength corresponding to the experimental upper and lower structural surfaces under different freeze-thaw cycles, respectively; and obtain the upper rock wall strength and the lower rock wall strength based on the first rock wall strength and the second rock wall strength, respectively.

[0007] The strength of the freeze-thaw composite rock wall is obtained based on the strength of the upper and lower rock walls; the freeze-thaw roughness coefficient of the anisotropic structural surface is obtained based on the experimental upper and lower structural surfaces under different freeze-thaw cycles.

[0008] The basic freeze-thaw friction angles of the anisotropic structural surfaces were obtained based on the experimental upper and lower structural surfaces under different freeze-thaw cycles; the freeze-thaw friction angle increments were obtained using the strength of the freeze-thaw composite rock wall, the freeze-thaw roughness coefficient, and the normal stress of the anisotropic structural surfaces; and the shear strength model of the freeze-thaw anisotropic structural surfaces was calculated based on the freeze-thaw friction angle increments and the basic freeze-thaw friction angles.

[0009] Preferably, constructing the experimental upper and lower structural surfaces of predetermined dimensions includes:

[0010] The upper and lower structural surfaces in the experiment have the same preset dimensions; however, the materials of the upper and lower structural surfaces are different.

[0011] Preferably, the first rock wall strength and the second rock wall strength are used to obtain the upper rock wall strength and the lower rock wall strength, respectively, including:

[0012] Without freeze-thaw cycles, the initial upper rock wall strength corresponding to the experimental upper structural surface and the initial lower rock wall strength corresponding to the experimental lower structural surface are obtained. Rock wall strength tests are conducted under different freeze-thaw cycles to obtain the first and second rock wall strengths of the experimental upper structural surface. The upper rock wall strength is obtained based on the first rock wall strength and the initial upper rock wall strength of the experimental upper structural surface under different freeze-thaw cycles. The lower rock wall strength is obtained based on the second rock wall strength and the initial lower rock wall strength of the experimental lower structural surface under different freeze-thaw cycles.

[0013] Preferably, the strength of the freeze-thaw composite rock wall is:

[0014]

[0015] σ DS =f2(σ S0 ,λ)=σ S0 e c2λ ,

[0016] σ DX =f3(σ X0 ,λ)=σ X0 e c3λ ,

[0017] Where, σ DF Indicates the strength of the freeze-thaw composite rock wall; σ DS Indicates the strength of the upper rock wall; σ DX σ represents the lower rock wall strength; b represents the rock wall strength adjustment parameter; S0 c2 represents the initial upper rock wall strength; c2 represents the upper rock wall strength adjustment parameter; σ X0 Initial lower rock wall strength; c3 represents the lower rock wall strength adjustment parameter; λ represents the number of freeze-thaw cycles; e represents the natural constant.

[0018] Preferably, the freeze-thaw roughness coefficient of the anisotropic structural surface is obtained based on the experimental upper and lower structural surfaces under different freeze-thaw cycles, including:

[0019] The initial roughness coefficients of the experimental upper and lower structural surfaces were obtained before freeze-thaw cycles. The freeze-thaw roughness coefficients were obtained by fitting the roughness coefficients of the experimental upper and lower structural surfaces under different freeze-thaw cycles, based on the initial roughness coefficients.

[0020] Preferably, the basic freeze-thaw friction angle of the anisotropic structural surface is obtained based on the experimental upper and lower structural surfaces under different freeze-thaw cycles, including:

[0021] The initial basic friction angles of the experimental upper and lower structural surfaces without freeze-thaw cycles are obtained. The freeze-thaw basic friction angle is obtained by fitting the basic friction angles obtained from the experimental upper and lower structural surfaces under different freeze-thaw cycles, based on the initial basic friction angles.

[0022] Preferably, the freeze-thaw friction angle increment is:

[0023]

[0024] in, Indicates the increment of the freeze-thaw friction angle; JRC D σ represents the freeze-thaw roughness coefficient; DF Indicates the strength of the freeze-thaw composite rock wall; σ n d1 represents the normal stress; d2 and d3 represent the first coefficient, the second coefficient, and the third coefficient, respectively.

[0025] Preferably, the shear strength model of the freeze-thaw anisotropic structural surface is calculated based on the freeze-thaw friction angle increment and the basic freeze-thaw friction angle, including:

[0026] The basic friction angle for freeze-thaw cycles is:

[0027]

[0028] in, Indicates the basic angle of friction between freeze and thaw cycles; c4 represents the initial basic friction angle; λ represents the basic friction angle adjustment parameter; e represents the number of freeze-thaw cycles; and e represents the natural constant.

[0029] The shear strength model of the freeze-thaw anisotropic structural surface is as follows:

[0030]

[0031] Where, τ DP σ represents the shear strength of the freeze-thaw anisotropic structural surface; n Indicates normal stress; This represents the increment of the freeze-thaw friction angle.

[0032] The embodiments of the present invention have at least the following beneficial effects: The present invention constructs an experimental upper structural surface and an experimental lower structural surface of preset size for experiments, facilitating subsequent analysis of the shear strength of the anisotropic structural surface. Furthermore, by conducting experiments under different freeze-thaw cycles, the first rock wall strength corresponding to the experimental upper structural surface, the second rock wall strength corresponding to the experimental lower structural surface, the freeze-thaw roughness coefficient of the anisotropic structural surface, and the freeze-thaw basic friction angle of the anisotropic structural surface are obtained. This allows for the acquisition of the changes in various factors affecting the shear strength of the anisotropic structural surface under freeze-thaw conditions, enabling a more accurate analysis of the changes in the shear strength of the anisotropic structural surface under freeze-thaw conditions. Simultaneously, the freeze-thaw composite rock wall strength is obtained based on the first and second rock wall strengths, improving the accuracy of the rock wall strength of the anisotropic structural surface under freeze-thaw conditions. The present invention analyzes the factors affecting the shear strength of the anisotropic structural surface under freeze-thaw conditions, while considering the differences in mechanical properties between the upper and lower structural surfaces of the anisotropic structural surface, accurately obtaining the shear strength model of the anisotropic structural surface under freeze-thaw conditions, and calculating the shear strength of the anisotropic structural surface under freeze-thaw conditions. Attached Figure Description

[0033] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a flowchart illustrating a method for obtaining the shear strength of anisotropic structural surfaces under freeze-thaw conditions, as provided in an embodiment of the present invention. Detailed Implementation

[0035] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a method for obtaining the shear strength of anisotropic structural surfaces under freeze-thaw conditions according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0037] The following description, in conjunction with the accompanying drawings, details a specific scheme for obtaining the shear strength of anisotropic structural surfaces under freeze-thaw conditions, provided by the present invention.

[0038] Example:

[0039] The main application scenarios of this invention are as follows: Many factors affect the shear strength of a structural surface, such as the roughness of the structural surface, the rock wall strength of the structural surface, and the normal stress. Therefore, when obtaining the shear strength of a structural surface, it is necessary to carefully consider the factors affecting the shear strength of the structural surface in order to obtain an accurate shear strength. Furthermore, in a freeze-thaw environment, the acquisition of the shear strength of the structural surface has an impact on the subsequent construction of rock mass engineering. Therefore, it is necessary to obtain the shear strength of the structural surface in a freeze-thaw environment.

[0040] Please see Figure 1 The diagram illustrates a method for obtaining the shear strength of anisotropic structural surfaces under freeze-thaw conditions, according to an embodiment of the present invention. The method includes the following steps:

[0041] Step S1: Construct an experimental upper structural surface and an experimental lower structural surface of preset size; obtain the first rock wall strength and the second rock wall strength corresponding to the experimental upper structural surface and the experimental lower structural surface under different freeze-thaw cycles, and obtain the upper rock wall strength and the lower rock wall strength based on the first rock wall strength and the second rock wall strength, respectively.

[0042] Rock masses are composed of rock blocks and fissures. The presence of fissures significantly reduces the strength of the rock mass. The shear mechanical properties of structural planes in rock mass engineering, namely the shear strength of structural planes, are a major factor affecting the stability of rock mass engineering and are very important parameters that require special attention during rock mass engineering construction. Existing research mainly focuses on the compressive-shear failure mechanism of structural planes under normal conditions. Most studies have failed to consider the true roughness characteristics of structural planes, and the main experimental objects of current frozen rock research are intact rock samples and fractured rock samples, with relatively few studies specifically targeting through structural planes under freeze-thaw cycles.

[0043] Shear strength τ of structural surfaces under normal conditions P It mainly depends on the roughness of the structural surface, the rock wall strength σ, and the normal stress σ of the structural surface. n and the basic friction angle between the upper and lower structural surfaces Factors such as these are considered. Therefore, it is necessary to analyze each factor to obtain the shear strength of the structural surface.

[0044] First, it is necessary to construct the experimental bodies required for the experiment. Two experimental bodies are constructed, and the materials of the experimental bodies are different, which are used to form heterogeneous structural surfaces. That is, to construct an upper and lower structural surface of a predetermined size. Since the materials of the experimental bodies are different, the upper and lower structural surfaces are heterogeneous structural surfaces, and the predetermined sizes of the upper and lower structural surfaces are the same, that is, the two experimental bodies have the same size. Preferably, in this embodiment of the invention, the size of the experimental body is 100mm×100mm×50mm. The implementer can choose a suitable size according to the actual situation.

[0045] Furthermore, it is necessary to determine the rock wall strength of the experimental upper and lower structural planes, where the rock wall strength parameters of the structural planes mainly include the compressive strength σ. c and tensile strength σ t However, there is some controversy regarding whether to use compressive strength or tensile strength to determine the rock wall strength of a structural plane, and there is no specific public specification. Therefore, this invention, based on experimental upper and lower structural planes, investigates the time-history evolution of shear fractures and tensile fractures according to the acoustic signals generated during shearing. Based on this, it determines the characterization parameters of the rock wall strength of the experimental upper and lower structural planes, which may be the compressive strength σ. c It could also be the tensile strength σ t In this application, to prevent errors in obtaining the rock wall strength of the upper and lower structural surfaces in the experiment, the compressive strength σ is... c and tensile strength σ t The rock wall strength of the experimental upper and lower structural planes is represented by a combination of these parameters; specifically: σ = a1σ c +a2σ t σ represents the rock wall strength of the experimental upper or lower structural plane, and a1 and a2 represent the first and second weights, respectively. a1 and a2 are determined based on the number of tensile and shear fractures during the shearing process. a1 represents the proportion of shear fractures to the total fractures, and a2 represents the proportion of tensile fractures to the total fractures.

[0046] Specifically, experiments are conducted under different freeze-thaw cycles. Based on the emission signals during the shearing process, the temporal evolution of shear fractures and tensile fractures is investigated, and the anisotropic structural surface is identified, which is a quantitative indicator of the rock wall strength of the experimental upper and lower structural surfaces. Preferably, the freeze-thaw cycles in the embodiments of this invention are 0, 10, 20, 30, and 40 times, respectively. Implementers can adjust the freeze-thaw cycles according to specific circumstances to make it more consistent with the actual environment.

[0047] Experiments were conducted under different freeze-thaw cycles. The compressive strength σ of the upper or lower structural surface under the corresponding freeze-thaw environment was obtained for each cycle. cand tensile strength σ t For example, at zero freeze-thaw cycles, the compressive and tensile strengths corresponding to the upper and lower structural surfaces can be obtained separately. Then, by combining these strengths (i.e., by weighted summation), the rock wall strength corresponding to the upper structural surface can be obtained, denoted as the first rock wall strength. Similarly, the rock wall strength corresponding to the lower structural surface can be obtained, denoted as the second rock wall strength. Thus, by conducting rock wall strength tests at different freeze-thaw cycles, the first and second rock wall strengths corresponding to the upper and lower structural surfaces can be obtained at each freeze-thaw cycle.

[0048] When the number of freeze-thaw cycles is 0, the strength of the first rock wall corresponding to the upper structural surface in the experiment is the initial strength of the upper rock wall, and the strength of the second rock wall corresponding to the lower structural surface in the experiment is the initial strength of the lower rock wall.

[0049] Furthermore, based on the initial upper rock wall strength and the first rock wall strength corresponding to the experimental upper structural surface under different freeze-thaw cycles, the relationship between the rock wall strength of the experimental upper structural surface under freeze-thaw conditions and the number of freeze-thaw cycles is obtained, thereby obtaining the upper rock wall strength of the experimental upper structural surface under freeze-thaw conditions, specifically:

[0050] σ DS =f2(σ S0 ,λ)=σ S0 e c2λ , where σ DS Indicates the strength of the upper rock wall; σ S0 c2 represents the initial upper rock wall strength; c2 represents the upper rock wall strength adjustment parameter; λ represents the number of freeze-thaw cycles; e represents the natural constant.

[0051] Similarly, based on the initial lower rock wall strength and the second rock wall strength corresponding to the experimental lower structural surface under different freeze-thaw cycles, the relationship between the rock wall strength of the experimental lower structural surface under freeze-thaw conditions and the number of freeze-thaw cycles is obtained, thereby obtaining the lower rock wall strength of the experimental lower structural surface under freeze-thaw conditions:

[0052] σ DX =f3(σ X0 ,λ)=σ X0 e c3λ , σ DX Indicates the strength of the lower rock wall; σ X0 c3 represents the initial lower rock wall strength; c3 represents the lower rock wall strength adjustment parameter; λ represents the number of freeze-thaw cycles; and e represents the natural constant.

[0053] It can be observed that as the number of freeze-thaw cycles gradually increases, the rock wall strength of both the upper and lower structural surfaces decreases exponentially. It should also be noted that the upper and lower rock wall strength adjustment parameters are obtained through fitting, with continuous verification and correction during the fitting process to reduce errors and obtain the most suitable adjustment parameters. In this embodiment of the invention, the upper rock wall strength adjustment parameters are determined by statistical analysis of the number of freeze-thaw cycles and the upper rock wall strength of the upper structural surface. Similarly, the lower rock wall strength adjustment parameters are determined by statistical analysis of the number of freeze-thaw cycles and the lower rock wall strength of the lower structural surface. When obtaining the rock wall strength, the experiment conducted in this embodiment of the invention under freeze-thaw conditions is uniaxial compression; implementers can choose other experimental methods according to actual conditions.

[0054] Thus, the upper and lower rock wall strengths of the experimental upper and lower structural surfaces under freeze-thaw conditions were obtained, providing support for subsequent analysis of the shear strength of anisotropic structural surfaces under freeze-thaw conditions.

[0055] Step S2: Obtain the strength of the freeze-thaw composite rock wall based on the strength of the upper rock wall and the strength of the lower rock wall; obtain the freeze-thaw roughness coefficient of the anisotropic structural surface based on the experimental upper and lower structural surfaces under different freeze-thaw cycles.

[0056] As explained in step S1 when constructing the experimental bodies, the two experimental bodies are made of different materials. Considering that the upper and lower structural surfaces in the experiment are composed of different materials, it is first necessary to determine the rock wall strength of the composite structural surface, which is related to the upper rock wall strength σ corresponding to the upper structural surface in the experiment. DS The lower rock wall strength σ corresponding to the experimental structural plane DX There is a close relationship among the three, and the relationship between them follows certain rules, specifically: 1. The rock wall strength of the composite structural surface and the upper rock wall strength σ DS Lower rock wall strength σ DX 1. A positive correlation exists; 2. Actual experimental results and numerical calculation results prove that shear failure of the structural surface tends to occur on the weaker side, meaning that shear failure is more likely to occur from the weaker side of the structural surface. When the upper rock wall strength σ DS and lower rock wall strength σ DX When the values ​​are similar, the composite strength is basically equal to the upper rock wall strength σ. DS When the strength σ of the upper rock wall DS The value is much lower than the lower rock wall strength σ DX At that time, the composite strength is mainly determined by the lower rock wall strength σ. DX Decision; when the upper rock wall strength σ DS The value is much higher than the lower rock wall strength σ DX The composite strength is mainly determined by the strength σ of the upper rock wall. DS Decision. Therefore, it can be proposed to utilize the upper rock wall strength σ DS and lower rock wall strength σDX The strength of the composite rock wall with anisotropic structural surfaces under freeze-thaw conditions is calculated and denoted as the freeze-thaw composite rock wall strength, specifically as follows:

[0057]

[0058] Where, σ DF Indicates the strength of the freeze-thaw composite rock wall; σ DS Indicates the strength of the upper rock wall; σ DX denoted as , b represents the rock wall strength; b represents the rock wall strength adjustment parameter, preferably b = 2 in this embodiment of the invention.

[0059] Furthermore, it is necessary to conduct experiments on the roughness coefficient of the anisotropic structure surface to obtain the roughness coefficient JRC of the anisotropic structure surface under freeze-thaw conditions. Specifically, three-dimensional laser scanning experiments need to be carried out on the upper and lower structure surfaces of the experiment. Then, the root mean square of the first derivative Z2 of the profile is calculated, specifically:

[0060]

[0061] Where, x i and y i Let x and y represent the x and y coordinates of the i-th point, respectively; N represents the number of points.

[0062] After obtaining Z2, the roughness coefficient JRC is further calculated as follows: JRC = 32.2 + 32.47·log(Z2). The roughness coefficient can be calculated based on these two formulas.

[0063] Specifically, the initial roughness coefficients of the experimental upper and lower structural surfaces before freeze-thaw cycles are obtained, denoted as JRC0. Further, for the experimental upper and lower structural surfaces under different freeze-thaw cycles, the roughness coefficients are calculated using the method described above to obtain the roughness coefficients corresponding to different freeze-thaw cycles λ. Then, combined with the initial roughness coefficients, the freeze-thaw roughness coefficients are obtained by fitting using the least squares method. Specifically:

[0064] JRC D =f1(JRC0,λ)=JRC0·e c1 λ,

[0065] Where JRC0 represents the initial roughness coefficient, c1 represents the roughness coefficient adjustment parameter, and the roughness coefficient adjustment parameter can be determined by statistical analysis of different freeze-thaw cycles and corresponding roughness coefficients; λ represents the number of freeze-thaw cycles, and e represents the natural constant. Thus, the relationship between the number of freeze-thaw cycles and the roughness coefficient can be obtained, which can facilitate the subsequent calculation of shear strength.

[0066] Step S3: Obtain the basic freeze-thaw friction angle of the anisotropic structural surface under different freeze-thaw cycles based on the experimental upper and lower structural surfaces; obtain the freeze-thaw friction angle increment using the strength of the freeze-thaw composite rock wall, the freeze-thaw roughness coefficient, and the normal stress of the anisotropic structural surface; calculate the shear strength model of the freeze-thaw anisotropic structural surface based on the freeze-thaw friction angle increment and the basic freeze-thaw friction angle.

[0067] In step S1, an experimental body was constructed, and then a tilting test was conducted. During the tilting test, both the upper and lower structural surfaces of the experimental body were flat. The tilting angle corresponding to the instant when the upper structural surface began to slide is the basic friction angle between the upper and lower structural surfaces. Furthermore, by detecting the fundamental friction angles of the experimental upper and lower structural surfaces under different freeze-thaw cycles, the fundamental friction angles corresponding to different freeze-thaw cycles can be obtained. Then, combined with the initial fundamental friction angle, i.e., the fundamental friction angle before freeze-thaw, a fitting process is performed to obtain the freeze-thaw fundamental friction angle, which is:

[0068]

[0069] in, Indicates the basic angle of friction between freeze and thaw cycles; c4 represents the initial basic friction angle; c4 represents the basic friction angle adjustment parameter, which can be determined by statistical analysis of the number of freeze-thaw cycles and the corresponding basic friction angles; λ represents the number of freeze-thaw cycles; and e represents the natural constant.

[0070] The shear strength of anisotropic structural surfaces can be considered as the sliding friction of a flat structural surface and the shear strength increment caused by the unevenness of the structural surface. These correspond to the basic friction angle and the friction angle increment, respectively. Therefore, it is necessary to calculate and analyze the variation characteristics of the friction angle under freeze-thaw conditions. Experiments have revealed some patterns in the friction angle increment: the friction angle increment is closely related to the ratio of normal stress and rock wall strength, as well as the roughness coefficient. It is positively correlated with the roughness coefficient and rock wall strength, and negatively correlated with normal stress. When the normal stress approaches infinity, the friction angle increment approaches 0; when the normal stress approaches 0, the friction angle increment approaches its maximum value. Therefore, the freeze-thaw friction angle increment can be obtained using the freeze-thaw composite rock wall strength, the freeze-thaw roughness coefficient, and the normal stress of the anisotropic structural surface. Specifically:

[0071]

[0072] in, Indicates the increment of the freeze-thaw friction angle; JRC D σ represents the freeze-thaw roughness coefficient; DF Indicates the strength of the freeze-thaw composite rock wall; σ nThe first coefficient represents the normal stress; d1, d2, and d3 represent the first, second, and third coefficients, respectively. It should be noted that the first, second, and third coefficients are...

[0073] When obtaining the shear strength of anisotropic structural surfaces in a freeze-thaw environment, the shear strength can be considered as the sum of the sliding friction forces on the experimental upper and lower structural surfaces of a flat surface and the shear strength increment caused by the unevenness of the structural surface. It can also be converted into the basic friction angle and the friction angle increment for calculation. The specific expression is as follows:

[0074]

[0075] Where, τ P F1 represents the shear strength; ΔF represents the sliding friction force; ΔF represents the shear strength increment. Indicates the basic angle of friction; This represents the friction angle increment; from this, the shear strength model of the anisotropic structural surface under freeze-thaw conditions can be obtained, specifically:

[0076]

[0077] Where, τ DP σ represents the shear strength of the freeze-thaw anisotropic structural surface; n Indicates normal stress; The increment of the freeze-thaw friction angle is denoted as the shear strength model for anisotropic structures under freeze-thaw conditions. This allows us to obtain the shear strength model for anisotropic structures under freeze-thaw conditions. In practical applications, this model can be used to calculate the shear strength of anisotropic structures under freeze-thaw conditions, while also considering the properties of rock wall strength, thus improving the accuracy of rock wall strength calculations and consequently enhancing the shear strength model under freeze-thaw conditions. d1, d2, and d3 represent the first, second, and third coefficients, respectively. These three coefficients can be obtained through least-squares fitting based on experimental results and the basic form of the shear strength model.

[0078] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, the above description focuses on specific embodiments of this specification. Additionally, the processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired results. In some embodiments, multitasking and parallel processing are possible or may be advantageous.

[0079] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for obtaining the shear strength of anisotropic structural surfaces under freeze-thaw conditions, characterized in that, The method includes: Construct an experimental upper and lower structural surface of a preset size; obtain the first rock wall strength and the second rock wall strength corresponding to the experimental upper and lower structural surfaces under different freeze-thaw cycles, respectively; and obtain the upper rock wall strength and the lower rock wall strength based on the first rock wall strength and the second rock wall strength, respectively. The strength of the freeze-thaw composite rock wall is obtained based on the strength of the upper and lower rock walls; the freeze-thaw roughness coefficient of the anisotropic structural surface is obtained based on the experimental upper and lower structural surfaces under different freeze-thaw cycles. The basic freeze-thaw friction angles of the anisotropic structural surfaces were obtained based on the experimental upper and lower structural surfaces under different freeze-thaw cycles; the freeze-thaw friction angle increments were obtained using the strength of the freeze-thaw composite rock wall, the freeze-thaw roughness coefficient, and the normal stress of the anisotropic structural surfaces; and the shear strength model of the freeze-thaw anisotropic structural surfaces was calculated based on the freeze-thaw friction angle increments and the basic freeze-thaw friction angles. The strength of the freeze-thaw composite rock wall is: ， ， ， in, Indicates the strength of the freeze-thaw composite rock wall; Indicates the strength of the upper rock wall; b represents the lower rock wall strength; b represents the rock wall strength adjustment parameter. c1 represents the initial upper rock wall strength; c2 represents the upper rock wall strength adjustment parameter; c3 represents the initial lower rock wall strength; c3 represents the lower rock wall strength adjustment parameter. Indicates the number of freeze-thaw cycles; e represents the natural constant; The freeze-thaw friction angle increment is: ， in, Indicates the increment of the freeze-thaw friction angle; Indicates the freeze-thaw roughness coefficient; Indicates the strength of the freeze-thaw composite rock wall; Indicates normal stress; , and These represent the first coefficient, the second coefficient, and the third coefficient, respectively. The shear strength model for calculating the anisotropic structure surface based on the freeze-thaw friction angle increment and the basic freeze-thaw friction angle includes: The basic friction angle for freeze-thaw cycles is: ， in, Indicates the basic angle of friction between freeze and thaw cycles; c4 represents the initial basic friction angle; c4 represents the basic friction angle adjustment parameter. Indicates the number of freeze-thaw cycles; e represents the natural constant; The shear strength model of the freeze-thaw anisotropic structural surface is as follows: ， in, Indicates the shear strength of a freeze-thaw anisotropic structural surface; Indicates normal stress; This represents the increment of the freeze-thaw friction angle.

2. The method for obtaining the shear strength of anisotropic structural surfaces under freeze-thaw conditions according to claim 1, characterized in that, The construction of the experimental upper and lower structural surfaces of the preset dimensions includes: The upper and lower structural surfaces in the experiment have the same preset dimensions; however, the materials of the upper and lower structural surfaces are different.

3. The method for obtaining the shear strength of anisotropic structural surfaces under freeze-thaw conditions according to claim 1, characterized in that, The process of obtaining the upper rock wall strength and lower rock wall strength based on the first rock wall strength and the second rock wall strength respectively includes: Without freeze-thaw cycles, the initial upper rock wall strength corresponding to the experimental upper structural surface and the initial lower rock wall strength corresponding to the experimental lower structural surface are obtained. Rock wall strength tests are conducted under different freeze-thaw cycles to obtain the first and second rock wall strengths of the experimental upper structural surface. The upper rock wall strength is obtained based on the first rock wall strength and the initial upper rock wall strength of the experimental upper structural surface under different freeze-thaw cycles. The lower rock wall strength is obtained based on the second rock wall strength and the initial lower rock wall strength of the experimental lower structural surface under different freeze-thaw cycles.

4. The method for obtaining the shear strength of anisotropic structural surfaces under freeze-thaw conditions according to claim 1, characterized in that, The freeze-thaw roughness coefficient of the anisotropic structural surface, obtained based on the experimental upper and lower structural surfaces under different freeze-thaw cycles, includes: The initial roughness coefficients of the experimental upper and lower structural surfaces were obtained before freeze-thaw cycles. The freeze-thaw roughness coefficients were obtained by fitting the roughness coefficients of the experimental upper and lower structural surfaces under different freeze-thaw cycles, based on the initial roughness coefficients.

5. The method for obtaining the shear strength of anisotropic structural surfaces under freeze-thaw conditions according to claim 1, characterized in that, The freeze-thaw basic friction angle of the anisotropic structural surface obtained based on the experimental upper and lower structural surfaces under different freeze-thaw cycles includes: The initial basic friction angles of the experimental upper and lower structural surfaces without freeze-thaw cycles are obtained. The freeze-thaw basic friction angle is obtained by fitting the basic friction angles obtained from the experimental upper and lower structural surfaces under different freeze-thaw cycles, based on the initial basic friction angles.

Images