Method for preparing rock samples with different crushing degrees through quantitative static load collaborative three-dimensional scanning

Abstract

The invention discloses a method for preparing rock samples with different crushing degrees through quantitative static load and three-dimensional scanning, which comprises the following steps: screening the rock samples according to pore fractures of the rock samples, the density of the rock samples and the ultrasonic wave velocity of the rock samples to obtain samples to be prepared; randomly selecting a group of rock samples from the to-be-prepared samples, and carrying out uniaxial compression test to obtain a rock sample total stress-strain curve; setting a strain value of the crushing degree of the rock sample under a static load condition according to the rock sample total stress-strain curve; and based on the strain values, crushing the residual rock samples by adopting a static load quantitative strain method, and screening the porosity of the rock samples to obtain the rock samples with different crushing degrees. According to the method, the rock samples with different crushing degrees can be prepared through the methods of three-dimensional pore crack scanning, rock ultrasonic testing, laboratory testing, qualitative and quantitative analysis and the like, and a premise is provided for research on analyzing the re-bearing mechanical characteristics of rock masses with different crushing degrees or stress paths.

Description

Technical Field

[0001] The invention belongs to the field of rock mechanics property research, and in particular relates to a method for preparing rock samples with different crushing degrees by using quantitative static load and coordinated three-dimensional scanning. Background Art

[0002] With the exploitation of coal resources, the mining depth of coal resources has increased year by year, and the mining depth has shifted from shallow to deep. High ground stress gradually appears, and the surrounding rock of excavation spaces such as tunnels and chambers bears a greater load, resulting in varying degrees of damage to the internal structure of the surrounding rock of the excavation space. It is of great significance to study the stability and support design of the surrounding rock of the excavation space under different degrees of damage. Therefore, it is particularly necessary to study the mechanical properties and bearing capacity of rock masses with different degrees of damage. The premise of the research is to artificially pre-destroy the rock samples. The existing artificial pre-destruction methods cannot accurately and simply characterize the pore and crack states of rock samples with different degrees of damage. Therefore, this technology provides a method for preparing rock samples with different degrees of damage by quantitative static load and coordinated three-dimensional scanning, which provides a research premise for studying the re-bearing mechanical properties of rock masses with different degrees of crushing. Summary of the invention

[0003] In order to solve the above technical problems, the present invention proposes a method for preparing rock samples with different degrees of crushing by quantitative static loading and coordinated three-dimensional scanning, so as to solve the problems existing in the above-mentioned prior art.

[0004] To achieve the above object, the present invention provides a method for preparing rock samples with different degrees of crushing by quantitative static loading and three-dimensional scanning, comprising the following steps:

[0005] The rock samples are screened according to their pores and cracks, density and ultrasonic wave velocity to obtain the samples to be prepared;

[0006] A group of rock samples are randomly selected from the samples to be prepared to perform uniaxial compression tests to obtain full stress-strain curves of the rock samples;

[0007] According to the full stress-strain curve of the rock sample, the strain value of the degree of rock sample crushing under static load conditions is set;

[0008] Based on the strain value, the static load quantitative strain method is used to crush the remaining rock samples and screen the porosity of the rock samples to obtain rock samples with different crushing degrees.

[0009] Preferably, the method for screening rock samples comprises:

[0010] The primary pores and fractures of several rock samples were characterized by three-dimensional scanning, and rock samples with undeveloped primary pores and fractures and similar primary porosity were selected to obtain preliminary screening rock samples;

[0011] The natural density and ultrasonic wave velocity of the preliminary screened rock samples are measured respectively, and rock samples with similar natural density and ultrasonic longitudinal wave velocity are selected as samples to be prepared.

[0012] Preferably, the three-dimensional scanning method includes but is not limited to CT scanning.

[0013] Preferably, when performing the uniaxial compressive test, the difference between the uniaxial compressive strength test values ​​of the rock samples is controlled within 0.5 MPa.

[0014] Preferably, the method for obtaining the strain value of the degree of rock sample crushing under static load conditions includes:

[0015] According to the stress-strain curve of the rock sample, the deformation and failure process of the rock sample is divided into the pre-failure stage and the post-failure stage. The pre-failure stage includes the pore and crack compaction stage, the elastic deformation stage, the stable crack development stage and the unstable crack development stage.

[0016] According to the stress-strain curve of the rock sample, the pre-destruction stage is divided into a slight damage zone, a moderate damage zone and a severe damage zone. The average strain value corresponding to each damage zone is used as the strain value of the crushing degree. Finally, the average value of the strain values ​​of different crushing degrees of the stress-strain curve is set as the strain value of the rock samples with different crushing degrees prepared under static load conditions.

[0017] Preferably, when performing uniaxial compression test on rock samples, a quantitative displacement control method is used to prepare rock samples with different degrees of crushing.

[0018] Compared with the prior art, the present invention has the following advantages and technical effects:

[0019] The present invention aims at the practical problem of the surrounding rock under load damage in the high stress environment of deep coal mines, and the evolution law of its mechanical properties and stability under the influence of different geological conditions. Through three-dimensional pore and crack scanning, rock ultrasonic testing, laboratory testing, qualitative and quantitative analysis and other methods, rock samples with different degrees of crushing are prepared, providing a research basis for subsequent research on the evolution law of mechanical properties of rock masses with different degrees of crushing under the action of different influencing factors. This design method is simple and easy to implement, has strong technical innovation, has high practicality, and has a very broad application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0021] Figure 1 A schematic diagram of a method flow chart of an embodiment of the present invention;

[0022] Figure 2The full stress-strain curve and strain value setting diagram of the rock sample SY-1 according to an embodiment of the present invention;

[0023] Figure 3 The full stress-strain curve and strain value setting diagram of the rock sample SY-7 according to the embodiment of the present invention;

[0024] Figure 4 The full stress-strain curve and strain value setting diagram of the rock sample SY-14 according to the embodiment of the present invention;

[0025] Figure 5 A three-dimensional pore and fracture scanning diagram of a slightly damaged rock sample according to an embodiment of the present invention;

[0026] Figure 6 A three-dimensional pore and fracture scanning diagram of a moderately damaged rock sample according to an embodiment of the present invention;

[0027] Figure 7 This is a three-dimensional pore and fracture scanning diagram of a severely damaged rock sample according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0029] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0030] Embodiment 1

[0031] like Figure 1 As shown, this embodiment provides a method for preparing rock samples with different degrees of crushing by quantitative static loading and three-dimensional scanning, including the following steps:

[0032] The rock samples are screened according to their pores and cracks, density and ultrasonic wave velocity to obtain the samples to be prepared;

[0033] A group of rock samples are randomly selected from the samples to be prepared for uniaxial compression test to obtain the full stress-strain curve of the rock samples;

[0034] According to the full stress-strain curve of the rock sample, the strain value of the rock sample crushing degree under static load conditions is set;

[0035] Based on the strain value, the static load quantitative strain method was used to crush the remaining rock samples and screen the porosity of the rock samples to obtain rock samples with different crushing degrees.

[0036] Further, the method for screening the rock sample includes:

[0037] The primary pores and fractures of several rock samples were characterized by three-dimensional scanning, and rock samples with undeveloped primary pores and fractures and similar primary porosity were selected to obtain preliminary screening rock samples;

[0038] The natural density and ultrasonic wave velocity of the preliminarily screened rock samples were measured respectively, and rock samples with similar natural density and ultrasonic longitudinal wave velocity were selected as the samples to be prepared.

[0039] Furthermore, three-dimensional scanning methods include but are not limited to CT scanning.

[0040] Furthermore, when conducting uniaxial compressive tests, the difference between the uniaxial compressive strength test values ​​of the rock samples is controlled within 0.5 MPa.

[0041] Furthermore, the method for obtaining the strain value of the degree of rock sample crushing under static load conditions includes:

[0042] According to the stress-strain curve of the rock sample, the deformation and failure process of the rock sample is divided into the pre-failure stage and the post-failure stage. The pre-failure stage includes the pore and crack compaction stage, the elastic deformation stage, the stable crack development stage and the unstable crack development stage.

[0043] According to the stress-strain curve of the rock sample, the pre-destruction stage is divided into slight damage zone, moderate damage zone and severe damage zone. The average strain value corresponding to each damage zone is taken as the strain value of the crushing degree. Finally, the average value of the strain values ​​of different crushing degrees of the stress-strain curve is set as the strain value of rock samples with different crushing degrees prepared under static load conditions.

[0044] Furthermore, when the uniaxial compression test is performed on the rock samples, the quantitative displacement control method is used to prepare rock samples with different crushing degrees.

[0045] The specific implementation is as follows:

[0046] Taking a mine as an example, the specific implementation steps are:

[0047] The average thickness of the 4# coal seam in a coal mine is 10m, the coal seam is buried 930m deep, the average thickness of the sandy mudstone on the direct roof is 10m, the sandy mudstone on the direct roof is relatively soft and broken, the roof cracks are developed, the rock quality is poor, and the rock integrity is poor. The average thickness of the basic top fine sandstone is 20m, the rock quality is medium, the rock mass is medium intact, it is a medium stable rock mass, and the rock group belongs to medium stable to weak stable rock formations. The roadway is greatly affected by high ground stress and has a large deformation. It is urgent to study the mechanical properties of different broken roof sandstones. Now, medium-grained sandstones with different degrees of crushing are prepared.

[0048] (1) The prepared 18 50mm×100mm standard uniaxial compression test pieces of sandstone were subjected to three-dimensional pore and fracture scanning, and the porosity of the three-dimensional scanned rock samples is shown in Table 1. Based on the scanning results, two samples with developed primary pores and fractures and a porosity exceeding 15% were eliminated, and the remaining 16 samples had similar porosities and undeveloped primary pores and fractures, with an average porosity of 6.32%. That is, 16 samples with undeveloped primary pores and fractures and similar primary porosity were selected for the next step of preparation;

[0049] Table 1

[0050]

[0051] (2) The natural density and ultrasonic wave velocity of the above samples were measured respectively, and the strength of the rock samples was preliminarily predicted. Rock samples with similar natural density and ultrasonic longitudinal wave velocity were selected as the samples to be prepared. The test results of the natural density and ultrasonic wave velocity of the rock samples are shown in Table 2. Three samples with natural density and ultrasonic wave velocity that were significantly different from others were eliminated based on the test results.

[0052] Table 2

[0053]

[0054] (3) A group of rock samples (SY-1, SY-7, SY-14) were randomly selected from the samples to be prepared for uniaxial compression test, and the total stress-strain curve of the rock samples was obtained, as shown in Figure 2 , Figure 3 , Figure 4 As shown, the strain values ​​of different crushing degrees set for the three specimens are shown in Table 3;

[0055] Table 3

[0056]

[0057] (4) According to the total stress-strain curves of the obtained rock samples (SY-1, SY-7, and SY-14), the strain values ​​of the rock samples with different degrees of crushing prepared under static load conditions were set to be 0.0080 (slight damage), 0.0189 (moderate damage), and 0.0245 (severe damage).

[0058] (5) According to the set strain values ​​of different degrees of damage of the rock samples, the static load quantitative strain method is used to prepare the remaining samples into rock samples with different degrees of crushing;

[0059] (6) Finally, the prepared rock samples with different crushing degrees were subjected to CT three-dimensional pore and fracture scanning. The porosity of the rock samples was used to characterize the different crushing degrees and analyze the pore and fracture ratio of the rock samples. The schematic diagram of the three-dimensional pore scanning is shown in the figure. Figure 5 , Figure 6 , Figure 7As shown, after three-dimensional fracture scanning characterization, the prepared rock sample meets the requirements.

[0060] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for preparing rock samples with different degrees of crushing by quantitative static loading and three-dimensional scanning, characterized in that: The following steps are involved: The rock samples are screened according to their pores and cracks, density and ultrasonic wave velocity to obtain the samples to be prepared; A group of rock samples are randomly selected from the samples to be prepared to perform uniaxial compression tests to obtain full stress-strain curves of the rock samples; According to the full stress-strain curve of the rock sample, the strain value of the degree of rock sample crushing under static load conditions is set; Based on the strain value, the static load quantitative strain method is used to crush the remaining rock samples and screen the porosity of the rock samples to obtain rock samples with different crushing degrees.

2. The method for preparing rock samples with different degrees of crushing by quantitative static loading and three-dimensional scanning according to claim 1 is characterized in that: The method for screening the rock sample comprises: The primary pores and fractures of several rock samples were characterized by three-dimensional scanning, and rock samples with undeveloped primary pores and fractures and similar primary porosity were selected to obtain preliminary screening rock samples; The natural density and ultrasonic wave velocity of the preliminary screened rock samples are measured respectively, and rock samples with similar natural density and ultrasonic longitudinal wave velocity are selected as samples to be prepared.

3. The method for preparing rock samples with different crushing degrees by quantitative static loading and three-dimensional scanning according to claim 2 is characterized in that: The three-dimensional scanning method includes but is not limited to CT scanning.

4. The method for preparing rock samples with different crushing degrees by quantitative static loading and three-dimensional scanning according to claim 1 is characterized in that: When conducting uniaxial compressive tests, the difference between the uniaxial compressive strength test values ​​of the rock samples is controlled within 0.5MPa.

5. The method for preparing rock samples with different crushing degrees by quantitative static loading and three-dimensional scanning according to claim 1 is characterized in that: The method for obtaining the strain value of the rock sample crushing degree under the static load condition includes: According to the stress-strain curve of the rock sample, the deformation and failure process of the rock sample is divided into the pre-failure stage and the post-failure stage. The pre-failure stage includes the pore and crack compaction stage, the elastic deformation stage, the stable crack development stage and the unstable crack development stage. According to the stress-strain curve of the rock sample, the pre-destruction stage is divided into a slight damage zone, a moderate damage zone and a severe damage zone. The average strain value corresponding to each damage zone is used as the strain value of the crushing degree. Finally, the average value of the strain values ​​of different crushing degrees of the stress-strain curve is set as the strain value of the rock samples with different crushing degrees prepared under static load conditions.

6. The method for preparing rock samples with different degrees of crushing by quantitative static loading and three-dimensional scanning according to claim 1 is characterized in that: When conducting uniaxial compression tests on rock samples, the quantitative displacement control method is used to prepare rock samples with different degrees of crushing.

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