A method for comprehensively evaluating deformation stability of different lithology combinations

Abstract

The application provides a method for comprehensively evaluating deformation stability of a lithology combination, comprising the following steps: S1, obtaining rock mechanics parameters of rock bodies on both sides of an interface; S2, establishing a basic mechanics model of the lithology interface; S3, analyzing overall deformation coordination of different rock bodies; according to coordination parameters of two kinds of rocks, the coordination of the two kinds of rocks is judged; S4, preparing a composite lithology fracture disc sample; S5, calculating an interface extension opening force of crack propagation at the interface; S6, combining the extension opening force size result in S5 and the rock body coordination in S3, and comprehensively evaluating the deformation stability of the lithology combination. The method innovatively combines experimental testing and mechanics theory to study the stability of different lithology combinations. The method combines experimental testing and mechanics theory to study the stability of different lithology combinations, and is various in research methods, novel in research angle and high in accuracy. The method combines macroscopic rock body overall coordination and interface microscopic fracture mechanism, is rigorous and comprehensive in problem consideration, and is high in practicability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of geological exploration, in particular to a method for comprehensively evaluating the deformation stability of different lithology combinations. BACKGROUND

[0002] In geological exploration, it is often encountered that a whole rock mass is composed of different lithology rocks. Due to the cutting effect of the lithology interface, the integrity of the rock mass is poor, the discrete type is strengthened, and the mechanical properties are discontinuous. In actual engineering, the combination of multiple lithology has an important influence on the construction effect. For example, in the pressure gas storage, the interface of different lithology often has a sudden change in permeability. For another example, the underground chamber may cross multiple lithology strata, which has a significant impact on its stability. The existing methods are mostly for identifying the stability of single rock mass structure. In actual work, they can only be applied to the identification of the state of single rock mass structure and the identification of rock mass stability and coordination. In construction engineering, the deformation and stability of multiple lithology combinations are not evaluated, which may cause induced ground pressure hazards, local rupture deformation instability, and safety accidents, with great harm and strong destructive power. Therefore, a method for comprehensively evaluating the deformation stability of different lithology combinations is proposed to solve the above problems.

[0003] Chinese patent document CN 111337349 A discloses a method for identifying the characteristics of precursory body measurement indexes of deep mining surrounding rock pressure disasters. In the stress-strain relationship of the mining surrounding rock, it is found that local rupture deformation occurs before the compression peak, and the rock mass is in a sub-instability stage after the peak. The changes before and after the peak are reflected by the optical information of the surrounding rock, which is used to identify and predict the deep mining surrounding rock. However, this method does not evaluate the deformation and stability of multiple lithology combinations, which may cause induced ground pressure hazards, local rupture deformation instability, and safety accidents. SUMMARY

[0004] The present application provides a method for comprehensively evaluating the deformation stability of different lithology combinations, which is used for evaluating the stability of multiple lithology combination rock mass under complex stress conditions and can prevent the collapse, collapse and other engineering disasters caused by continuous crack expansion at the junction of multiple rock masses in tunnel, underground chamber and other project constructions.

[0005] To solve the above technical problems, the technical solution adopted by the present application is as follows: a method for comprehensively evaluating the deformation stability of different lithology combinations, comprising the following steps: S1, obtaining the rock mechanics parameters of the rock mass on both sides of the interface: drilling the rock mass on both sides of the interface, and performing uniaxial compression experiment on the rock mass on both sides to obtain the rock mechanics parameters of the rock mass on both sides of the interface;

[0006] S2, establishing a basic mechanical model of the lithology interface;

[0007] S3, analyzing the overall deformation compatibility of different rock bodies: judging the compatibility of two kinds of rocks according to the compatibility parameters of the two kinds of rocks;

[0008] S4, preparing a composite rock fracture disc sample;

[0009] S5, calculating the interface extension opening force of crack propagation at the interface;

[0010] S6, combining the extension opening force size result in S5 and the rock body compatibility in S3 to comprehensively evaluate the deformation stability of the rock combination.

[0011] In the preferred scheme, the step of obtaining the rock mechanics parameters of the rock bodies on both sides of the interface in S1 is:

[0012] A1: drilling or making rock standard cylindrical samples on both sides of the interface to be studied;

[0013] A2: performing uniaxial compression experiments on the two kinds of rocks to calculate the elastic modulus and Poisson's ratio, and obtain the rock mechanics parameters of the rock bodies on both sides of the interface;

[0014] In the preferred scheme, the step of establishing the mechanical model in S2 is:

[0015] B1: simplifying various types of interfaces and establishing a mechanical model of a basic type of interface;

[0016] If the mineral layer between the two kinds of rocks is relatively thick, it is regarded as two interfaces;

[0017] If the mineral layer between the two kinds of rocks is relatively thin, it is regarded as one interface;

[0018] B2: analyzing the continuity conditions of stress and strain at the interface;

[0019] Satisfy: ;

[0020] The subscripts x and y represent the coordinate axis directions corresponding thereto. σ is the normal stress at the interface; τ is the shear stress at the interface; u and v represent the displacements of the x and y coordinate axes at the interface, respectively.

[0021] In the preferred scheme, the step of analyzing the compatibility of different rock bodies in S3 is:

[0022] C1: establishing a basic mechanical equation:

[0023] The equation is:

[0024] ;

[0025] E 1 、E 2 , μ 1 , μ2 are rock mechanics parameters of two rock masses respectively, X1 and X2 are coordination parameters of two rock masses respectively;

[0026] C2: solve the material parameters X1 and X2 of the overall coordination of the rock mass according to the continuity condition at the bonding interface 2；

[0027] C3: judge the stability of the deformation coordination of the rock mass.

[0028] In the preferred scheme, in C3, the method for judging the stability of the deformation coordination of the rock mass is:

[0029] When > 0, stress concentration exists, and the rock mass coordination is poor;

[0030] When = 0, a non-constant stress field exists, and the deformation coordination of the rock mass is good;

[0031] When < 0, the deformation coordination of the rock mass is good, and the overall deformation is stable.

[0032] In the preferred scheme, in S4, the mode of the composite disc sample is: a composite disc sample containing two rock masses is prepared, the rock mass interface is divided into two parts along the diameter, and a crack of a certain length is cut in the middle.

[0033] In the preferred scheme, the step of calculating the interface extension opening force of the crack propagation at the interface is:

[0034] D1: load the composite disc sample until the initial crack propagates along the interface, and the sample is split or completely destroyed;

[0035] D2: record the experimental parameters, and obtain the expression of the interface extension opening force through Euler analysis and Froude Criterion similarity system analysis:

[0036] P is the failure pressure when the sample is destroyed, D is the diameter of the sample, 2a is the length of the interface cut, k i is a unit dimensionless strength factor.

[0037] The beneficial effects of the present application are: innovatively combining experimental testing with mechanical theory to study the stability of different rock mass combinations. By establishing a mechanical model of the two rock masses at the rock mass interface, converting the mechanical properties of the two rock masses into a mechanical formula through the rock mass deformation coordination mechanical model calculation formula, and accurately and quickly calculating the size of the formula value through the calculation mechanical formula, the overall coordination of the two combined rock masses is intuitively and quickly judged on a macroscopic level, and the research method is various, novel and accurate.

[0038] ​By combining the micro fracture mechanism of rock mass, the crack propagation ability experiment is carried out on the micro interface, the interface extension force expression is obtained, the energy required for the crack to propagate along the interface is obtained on the micro interface, and the relative stability of the combined rock mass on the micro interface is quantitatively described.

[0039] The macro rock mass integrity is combined with the interface micro fracture mechanism, the problem is considered rigorous and comprehensive, and the practicability is strong. It has great popularization value. BRIEF DESCRIPTION OF DRAWINGS

[0040] The application will be further described below in combination with the drawings and embodiments.

[0041] Figure 1 Fig. 1 is a schematic diagram of the interface model of the thick filling layer of the application;

[0042] Figure 2 Fig. 2 is a simplified schematic diagram of the model of the thin filling layer of the application;

[0043] Figure 3 Fig. 3 is a schematic diagram of the basic interface unit of the application;

[0044] Figure 4 Fig. 4 is a schematic diagram of the composite lithology disc sample of the application;

[0045] Figure 5 Fig. 5 is a schematic diagram of the composite lithology disc sample of the application under loading and failure. DETAILED DESCRIPTION

[0046] Embodiment 1:

[0047] As Figures 1-5 In the method for comprehensively evaluating the deformation stability of different lithology combinations, S1, rock mechanics parameters of rock masses on both sides of the interface are obtained: drilling the rock masses on both sides of the interface, respectively performing uniaxial compression experiments on the rock masses on both sides to obtain the rock mechanics parameters of the rock masses on both sides of the interface;

[0048] S2, a basic mechanical model of the lithology interface is established;

[0049] S3, the overall deformation compatibility of different rock masses is analyzed: according to the compatibility parameters of the two rocks, the compatibility of the two rocks is judged;

[0050] S4, a composite lithology disc sample is prepared;

[0051] S5, the interface extension force of crack propagation at the interface is calculated;

[0052] S6, the deformation stability of the lithology combination is comprehensively evaluated in combination with the extension force size result in S5 and the rock mass compatibility in S3.

[0053] The step of obtaining the rock mechanics parameters of the rock bodies on both sides of the interface in S1 is:

[0054] Drill enough amount of rock bodies on both sides of the interface, process into standard cylindrical samples of φ25*50mm, and perform uniaxial compression experiment to obtain the rock mechanics parameters of the rock bodies on both sides of the interface, which are E1, E2, μ1 and μ2 respectively.

[0055] In the preferred scheme, the step of establishing the mechanical model in S2 is:

[0056] The interface of natural rock mass is usually filled with a large amount of other mineral components and forms a relatively stable mineral layer with a certain thickness. When the mineral layer is thick, it can be regarded as two interfaces, as shown in Figure 1 When the filling layer is very thin and small enough relative to the scale of the engineering rock mass, it can be regarded as one interface, as shown in Figure 2 For the most basic single-interface unit, as shown in Figure 3 At this time, the following interface continuity conditions are met:

[0057] Satisfy: (1);

[0058] The subscripts x and y represent the coordinate axis directions corresponding thereto. σ is the normal stress at the interface; τ is the shear stress at the interface; u and v represent the displacements of the x and y coordinate axis directions at the interface respectively.

[0059] Figure 3 The coordinate system established for the lithology I and the lithology II.

[0060] The step of analyzing the coordination of different rock bodies in S3 is:

[0061] Establish the basic mechanical equation: for the rock mass combined by two kinds of lithology, four elastic parameters are involved, including two elastic moduli and two Poisson's ratios. However, they are not independent of each other. The basic equation of the complex stress function is:

[0062] (2)

[0063] Substitute (2) into the continuity condition (1) of the interface to obtain:

[0064] (3);

[0065] Here, Г=μ1 / μ2, where κ takes 3-4μ in plane strain and 3-μ / 1+μ in plane stress, and the "￣" on the parameter represents conjugate.

[0066] Integrate along the horizontal direction, and integrate on the horizontal axis:

[0067] (4);

[0068] Considering the variable transformation relation of complex function:

[0069] (5);

[0070] Substitute (4) into (5) and ignore the integral constant:

[0071] (6);

[0072] Let (7);

[0073] Thus (3) is transformed into:

[0074] (8);

[0075] Rewrite (8) into Bogy form:

[0076] (9);

[0077] E 1 、E 2 , μ 1 , μ 2are the rock mechanics parameters of two rock masses respectively, and X1 and X2 are the coordination parameters of two rock masses respectively;

[0078] Through the stress function and the continuity condition of interface, finally the parameters X1 and X2 are obtained to describe the deformation and stress of rock mass. The two parameters actually represent the overall coordination characteristics of mutual constraint of two rock masses.

[0079] Solving the material parameters X1 and X2 of overall coordination of rock mass 2。

[0080] For the coordination parameters X1 and X2, judge the stability of rock mass deformation coordination:

[0081] When > 0, stress concentration exists, and the rock mass coordination is poor;

[0082] When = 0, non-constant stress field, rock mass deformation coordination;

[0083] When < 0, rock mass deformation coordination, overall deformation stability.

[0084] Therefore, when 1-2X2 / X1≤0, there is no stress concentration at the interface, the deformation coordination of two sides of rock mass is good, and the overall strength is high.

[0085] The mode of composite disc sample in S4 is: drilling the rock mass containing interface on site, and processing into Figure 4The diameter D = 25 mm, thickness of 10 mm of the pie-shaped sample, lithology interface and diameter coincide, and the length of 2a = 15 mm of the prefabricated crack is cut at the interface;

[0086] Figure 4 The prefabricated crack of length 2a is cut in the middle of the interface between lithology I and lithology II.

[0087] The step of calculating the interface extension force of crack propagation at the interface in S5 is: the sample is applied with force F in the manner of Figure 5 , and the loading rate is 0.1 MPa / s, until the crack propagates to the boundary of the sample, and the sample is destroyed along the interface. The destruction pressure when the sample is destroyed is P, and through Euler analysis and Froude Criterion similarity system analysis, the expression for calculating the interface extension force is obtained: (10);

[0088] P is the destruction pressure when the sample is destroyed, D is the diameter of the sample, 2a is the length cut at the interface, k i is the unit dimensionless strength factor.

[0089] In the formula, k i is the unit dimensionless strength factor. The larger the value of Br, the more energy is needed for the crack to propagate along the interface, indicating that the cementation of the two lithologies is good, and the rock mass is relatively stable. The deformation stability of the rock mass containing the interface is judged by comprehensively analyzing the rock mass coordination of step 3 and the test results of the interface extension force size obtained in step 5.

[0090] Example 2, further illustrating example 1:

[0091] Taking the Chuan Shan tunnel as the engineering background, a certain thickness of concrete layer is used to support the surrounding rock after excavation, and the interface on both sides is combined with concrete and surrounding rock. Through uniaxial compression experiment, the concrete rock mechanics parameters elastic modulus E1 = 32.14 GPa, μ1 = 0.19, surrounding rock E2 = 17.24 GPa, μ2 = 0.27. The related mechanical parameters are substituted to obtain X1 = 0.28, X2 = 0.07, X1 / (X1-2X2) > 0. It is explained that when the deformation of the supporting concrete layer and the surrounding rock wall is disturbed, stress concentration is easy to occur, and uncoordinated deformation is easy to occur. The interface crack propagation experiment of the composite lithology pie of the tunnel corresponding to the concrete and the surrounding rock wall is carried out, the maximum pressure value is substituted to obtain 0.62 MPa•m0.5, which is small in general rock materials, indicating that the interface combination is poor and easy to crack. In summary, the overall integrity of the concrete and the surrounding rock is weak, and further measures such as increasing anchor rods, steel wire mesh, etc. can be considered for reinforcement.

[0092] The above embodiments are only preferred technical solutions of the present application, and should not be regarded as a limitation of the present application. The protection scope of the present application should be the technical solutions recited in the claims, including equivalent replacement solutions of the technical features recited in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present application.

Claims

1. A method for comprehensively evaluating the deformation stability of lithological aggregates, characterized by: Includes the following steps: S1. Obtain the rock mechanics parameters of the rock masses on both sides of the interface: Drill the rock masses on both sides of the interface and conduct uniaxial compression tests on the rock masses on both sides to obtain the rock mechanics parameters of the rock masses on both sides of the interface. S2. Establish a basic mechanical model of the lithological interface; S3. Analyze the overall deformation compatibility of different rock masses: Evaluate the compatibility of the two types of rocks based on their compatibility parameters. S4. Prepare composite lithological fracture disc specimens; S5. Calculate the interfacial extension force for crack propagation at the interface; S6. Combining the results of the magnitude of the extension force in S5 and the rock mass compatibility in S3, comprehensively evaluate the deformation stability of the lithological bond. The steps for analyzing the compatibility of different rock masses in S3 are: C1: Establishing the fundamental mechanical equations: The equation is: ； E1, E2, μ1, and μ2 are the rock mechanics parameters of the two rock masses, respectively, and X1 and X2 are the coordination parameters of the two rock masses. C2: Based on the continuity condition at the interface, solve for the material parameters X1 and X2 of the overall compatibility of the rock mass; C3: Determine the stability of rock mass deformation coordination; In C3, the method for determining the stability of rock mass deformation coordination is as follows: when >0 indicates stress concentration and poor rock mass compatibility; when = 0, non-zero constant stress field, rock mass deformation is coordinated; when <0 indicates coordinated rock mass deformation and overall stable deformation.

2. The method for comprehensively evaluating the deformation stability of lithological aggregates according to claim 1, characterized in that: The steps for obtaining the rock mechanics parameters of the rock masses on both sides of the interface in S1 are as follows: A1: Drill or prepare standard cylindrical rock samples from both sides of the interface under study; A2: Conduct uniaxial compression tests on two types of rocks, calculate the elastic modulus and Poisson's ratio, and obtain the rock mechanical parameters of the rock masses on both sides of the interface.

3. The method for comprehensively evaluating the deformation stability of lithological aggregates according to claim 1, characterized in that: S2 The steps for establishing a mechanical model are as follows: B1: Simplify various types of interfaces and establish mechanical models for basic types of interfaces; If the mineral layer between two types of rocks is thick, it is considered as two interfaces; If the mineral layer between the two types of rocks is thin, it can be considered as an interface. B2: Analyze the continuity conditions of stress and strain at the interface; satisfy: ; In the subscripts, x and y represent the corresponding coordinate axis directions; σ is the normal stress at the interface; τ is the shear stress at the interface; and u and v represent the displacements in the x and y coordinate axis directions at the interface, respectively.

4. The method for comprehensively evaluating the deformation stability of different lithological aggregates according to claim 1, characterized in that: the composite disk sample in S4 is prepared by: preparing a composite disk sample containing two lithologies, dividing the sample into two equal parts along the diameter at the lithological interface, and cutting a crack of a certain length in the middle.

5. The method for comprehensively evaluating the deformation stability of lithological aggregates according to claim 1, characterized in that: The steps for calculating the interfacial extension force for crack propagation at the interface are: D1: Load the composite disk specimen until the initial crack extends along the interface, and the specimen splits or is completely destroyed. D2: Record experimental parameters and obtain the expression for calculating the interface extension force through Euler analysis and Froude Criterion similarity system analysis: ; P is the failure pressure at which the sample fails, D is the sample diameter, 2a is the cut length at the interface, and k i The unit is a dimensionless intensity factor.

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