Double-notch rock shear strength test device and test method

Abstract

The invention discloses a double-notch rock shear strength test device, comprising a pressure system, a specimen device, a spring device, a roller group device and a control system; the specimen device is a double-notch rock specimen, the rock specimen is placed in the roller group device, and then placed in the center of the test machine press table, the pressure system is above the test machine press table, and there are lateral pressure systems on both sides, and spring devices are arranged in the two notches of the rock specimen, the spring device comprises a spring and an axial force sensor, and the two ends of the spring are respectively fixed on the top of the notch of the rock specimen and the axial force sensor, the control system comprises a computer host and a computer display, the axial force sensor is connected to the computer host, and the computer host is connected to the computer display. The invention adopts a double-notch rock specimen for testing, which makes up for the shortcomings of the complex conditions of conventional shear tests, and the test operation is simple, the specimen processing and installation are convenient, which provides convenience for research, the test actual analysis data is small, and the test results can be obtained relatively quickly.

Description

Technical Field

[0001] The invention relates to the technical field of engineering geology, and in particular to a double-notch rock shear strength testing device and a testing method. Background Art

[0002] In civil engineering, water conservancy and hydropower, railways, highways, mining and other projects, we often face the problem of shear instability and failure of rock slopes, which is related to the shear force on the rock and soil. Shear strength theory is the cornerstone of soil mechanics and the theoretical basis for slope stability analysis. It provides important theoretical parameters for the calculation of rock shear strength stability and slope design. As one of the important mechanical indicators of rock mass, rock shear strength is directly related to the stability and safe use of engineering structures, and is of great significance for the smooth implementation of engineering construction. The existing shear strength tests basically use triaxial tests and direct shear tests. In the fields of metallurgy and energy, variable angle shear methods are also commonly used to test the shear strength of rocks. These methods require relatively complex test conditions, and the test equipment occupies a large area, which is sometimes difficult to meet. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a double-notch rock shear strength testing device with simple structure and convenient operation, and provides a double-notch rock shear strength testing method.

[0004] The technical solution of the present invention to solve the above-mentioned problem is: a double-notch rock shear strength testing device, including a pressure system, a specimen device, a spring device, a roller group device and a control system; the specimen device is a processed double-notch rock specimen, the rock specimen is placed in the roller group device, the roller group device is placed at the center of the test machine press, a top pressure system for applying top pressure to the rock specimen is provided above the test machine press, and side pressure systems for applying side pressure to the rock specimen are provided on both sides of the test machine press, a set of spring devices are provided in the two notches of the rock specimen, each set of spring devices includes a spring with a known elastic coefficient and an axial force sensor, and the two ends of the spring are respectively fixed on the top of the notch of the rock specimen and the axial force sensor, and the control system includes a computer host and a computer display, the axial force sensor is connected to the computer host, and the computer host is connected to the computer display.

[0005] The above-mentioned double-notch rock shear strength testing device, the roller group device includes two L-shaped steel plates and two vertical steel plates, the two L-shaped steel plates are spliced ​​together to form a square frame for placing rock specimens, a vertical steel plate is provided on the outside of the two L-shaped steel plates, and a lateral force sensor is attached to the outside of the vertical steel plates on both sides, and a plurality of steel pipes are longitudinally provided from top to bottom between the outside of the L-shaped steel plate and the vertical steel plate, and the steel pipes are fixed on the vertical steel plates. The lateral pressure system applies pressure on the vertical steel plates, which is transmitted to the L-shaped steel plates through the steel pipes to apply lateral pressure to the rock specimens.

[0006] In the above-mentioned double-notch rock shear strength testing device, the two notches of the rock specimen are respectively distributed on the left and right sides of the rock specimen, one above and one below.

[0007] The double-notch rock shear strength testing device has a rock specimen with a height of 200 mm, a width of 100 mm and a thickness of 100 mm. A prefabricated crack is provided in the middle of the rock specimen, the crack length is 18 mm and the crack angle is 0° to 30°.

[0008] A double-notch rock shear strength testing method comprises the following steps:

[0009] 1) Connect the lower end of the spring of the spring device to the axial force sensor, and place two sets of spring devices into the two notches of the rock specimen respectively;

[0010] 2) A lateral force sensor is fixed on each of the outermost steel plates of the roller assembly, and then the double-notched rock specimen is placed in the square frame of the roller assembly;

[0011] 3) Connect the two axial force sensors in the notch of the rock specimen and the two lateral force sensors on the outermost steel plate of the roller assembly to the computer host;

[0012] 4) Turn on the computer host and the monitor, start the testing machine, and start recording the data collected by the axial force sensor and the lateral force sensor; use displacement control to make the lateral pressure head of the testing machine approach the two sides of the rock specimen. After the pressure head contacts the side surface of the rock specimen, when the pressure of the lateral force sensor is monitored to be 1N, use force control to load the lateral pressure to the test design value at a speed of 100N / s and keep it constant; also use displacement control to make the axial pressure head of the testing machine approach the surface of the rock specimen. After the pressure head contacts the surface of the rock specimen, when the pressure of the axial force sensor is displayed to be 2N, use force control to continue loading at a speed of 100N / s until the rock specimen is destroyed, that is, the shear test is completed;

[0013] 5) After the shear test of the rock specimen is completed, check the test data and select the record with the maximum load value as the failure load P. k , calculated based on the test data.

[0014] In the above-mentioned double-notch rock shear strength test method, in step 5):

[0015] Case 1: When the prefabricated crack angle is 0°, the shear surface is subjected to force analysis, the length L1 of the shear surface is measured, and the shear surface area A1=0.1L1 is calculated based on the specimen thickness. In this case, the normal stress σ1 and shear stress τ1 on the shear surface are respectively,

[0016] σ1=0

[0017] τ1=P k1 / A1

[0018] Case 2: When the prefabricated crack angle is 15° on the left, the shear surface is subjected to force analysis, the length L2 of the shear surface is measured, and the shear surface area A2=0.1L2 is calculated based on the specimen thickness. In this case, the normal stress σ2 and shear stress τ2 on the shear surface are respectively,

[0019] σ2=P k2 ·sin20 / A2=0.342P k2 / A2

[0020] τ2=P k2 ·cos20 / A2=0.940P k2 / A2

[0021] Case 3: When the prefabricated crack angle is 30° on the right side, the shear surface is subjected to force analysis, the length L3 of the shear surface is measured, and the shear surface area A3=0.1L3 is calculated based on the specimen thickness. In this case, the normal stress σ3 and shear stress τ3 on the shear surface are respectively,

[0022] σ3=P k3 ·sin24 / A3=0.407P k3 / A3

[0023] τ3=P k3 ·cos24 / A3=0.914P k3 / A3

[0024] By analyzing the data, we can get the normal stress σ, shear stress τ and failure load P k Mathematical relationship, from Coulomb's law , we get three points (σ1, τ1), (σ2, τ2), (σ3, τ3) composed of normal stress and shear stress. Connect the three points with a smooth curve on the σ-τ stress plane, and draw the σ-τ relationship curve, that is, we get the shear strength parameter internal friction angle , cohesion c.

[0025] The beneficial effects of the present invention are:

[0026] 1. The test device of the present invention adopts double-notched rock specimens for testing, which makes up for the deficiency of complex test conditions required by conventional shear tests. In addition, the test operation is simple and the specimen processing and installation are convenient, which provides convenience for scientific research. The experimental analysis data is small and the test results can be obtained relatively quickly.

[0027] 2. In the test device of the present invention, the spring of the spring device is pressed against the top and bottom of the notch through the axial force sensor. When the axial force is applied to the upper part of the rock specimen, the spring is compressed in the vertical direction by the axial force. Due to the elastic force of the spring, the axial force sensor is given a reaction force, which is indirectly transmitted to the rock specimen, so that the force on the notches on both sides of the rock specimen is uniform without generating concentrated force, thereby playing a role in supporting and protecting the specimen.

[0028] 3. In the test device of the present invention, lateral pressure is applied to the roller assembly to offset the shear force generated by the axial pressure and reduce the test error.

[0029] 4. In the test method of the present invention, load is applied in the axial direction and lateral pressure is applied on the side during the test. The test operation is simple, and the processing of the test piece and the design and implementation of the test plan are relatively easy. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a front view of the rock specimen testing device of the present invention.

[0031] Figure 2 It is a front view of the square frame of the roller assembly device in an embodiment of the present invention.

[0032] Figure 3 This is a left view of a rock specimen with a prefabricated fracture angle of 0° in an embodiment of the present invention.

[0033] Figure 4 This is a left view of a rock specimen in which the prefabricated fracture angle is 15° to the left of the axis in an embodiment of the present invention.

[0034] Figure 5 This is a schematic diagram of the 15° prefabricated crack on the left side of the axis.

[0035] Figure 6 This is a left view of a rock specimen in which the prefabricated fracture angle is 30° to the right of the axis in an embodiment of the present invention.

[0036] Figure 7 This is a schematic diagram of the prefabricated crack sample at 30° on the right side of the axis. DETAILED DESCRIPTION

[0037] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0038] Embodiment 1

[0039] like Figure 1 , Figure 2 , Figure 3As shown, a double-notch rock shear strength testing device includes a pressure system, a specimen device, a spring device, a roller group device 2 and a control system; the specimen device is a processed double-notch rock specimen 7, the rock specimen 7 is 200mm high, 100mm wide and 100mm thick; a prefabricated crack 8 is provided in the middle of the rock specimen 7, the crack length is 18mm, the crack angle is 0°, and the two notches 3 of the rock specimen 7 are distributed on the left and right sides of the rock specimen 7, one above and one below. The rock specimen 7 is placed in the roller group device 2, and the roller group device 2 is placed at the center of the testing machine press table 11. A top pressure system for applying top pressure to the rock specimen 7 is provided above the testing machine press table 11, and side pressure systems for applying side pressure to the rock specimen are provided on both sides of the testing machine press table. A set of spring devices are provided in the two notches 3 of the rock specimen 7, and each set of spring devices includes a spring 6 with a known elastic coefficient and an axial force sensor 4. The axial force sensor 4 is a steel product with a thickness of 2 mm. The spring 6 is fixed on the axial force sensor 4 and pressed tightly against the top and bottom of the notch 3; the control system includes a computer host 1 and a computer display. The axial force sensor 4 is connected to the spring 6 and connected to the computer host 1. The computer host 1 is connected to the computer display, and the data monitored by the axial force sensor 4 is displayed on the computer display.

[0040] The roller group device 2 includes two L-shaped steel plates and two vertical steel plates. The two L-shaped steel plates are spliced ​​together to form a square frame for placing the rock specimen 7. A vertical steel plate is provided on the outside of the two L-shaped steel plates. A lateral force sensor 5 with the same structure as the axial force sensor 4 is attached to the outside of the vertical steel plates on both sides. A number of steel pipes are longitudinally arranged from top to bottom between the outside of the L-shaped steel plate and the vertical steel plate. The steel pipes are fixed on the vertical steel plates. The lateral pressure system applies pressure on the vertical steel plate, which is transmitted to the L-shaped steel plate through the steel pipe, thereby applying lateral pressure to the rock specimen 7.

[0041] The spring 6 of the spring device has a sufficiently large stiffness and a known elastic coefficient. The length of the spring 6 is determined according to the size of the notch 3 of the rock specimen 7 and the thickness of the axial force sensor 4, that is, the spring 6 maintains a zero expansion and contraction state when no force is applied, and the initial length of the spring 6 plus the thickness of the sensor 4 is consistent with the opening size of the notch 3. The spring device is placed in the notch 3. When an axial force is applied to the upper part of the rock specimen 7, the spring 6 is compressed in the vertical direction by the axial force; and due to the elastic force of the spring 6, a reaction force is given to the sensor 4, which is indirectly transmitted to the rock specimen 5, so that the force on the notch 3 on both sides of the rock specimen 7 is uniform without generating concentrated force, which plays a role in supporting and protecting the rock specimen 7. The lower end of the spring 6 is connected to the axial force sensor 4 instead of being directly fixed on the rock specimen 7, so that the force on the spring 6 is evenly dispersed to the rock specimen 7 during the entire loading process, reducing the impact on the experimental results.

[0042] The roller assembly 2 is made of 2 mm thick steel plate, and the wheel assembly is a solid steel pipe with a diameter of 4 mm. During the process of applying lateral pressure, it can have sufficient rigidity to resist the pressure without causing significant deformation.

[0043] A double-notch rock shear strength testing method, characterized by comprising the following steps:

[0044] 1) Connect the lower end of the spring 6 of the spring device to the axial force sensor 4, and place two sets of spring devices into the two notches 3 of the rock specimen 7 respectively;

[0045] 2) A lateral force sensor 5 is fixed on each of the outermost steel plates of the roller assembly 2, and then a double-notched rock specimen 7 is placed in the square frame of the roller assembly 2;

[0046] 3) Connect the two axial force sensors 4 in the notch of the rock specimen and the two lateral force sensors 5 on the outermost steel plate of the roller assembly to the computer host;

[0047] 4) Turn on the computer host 1 and the display, start the testing machine, and start recording the data collected by the axial force sensor 4 and the lateral force sensor 5. Use displacement control to make the lateral pressure head of the testing machine approach the two sides of the rock specimen. After the pressure head contacts the side surface of the rock specimen, when the pressure of the lateral force sensor is monitored to be 1N, use force control to load the lateral pressure to the test design value at a speed of 100N / s and keep it constant. Similarly, use displacement control to make the axial pressure head of the testing machine approach the surface of the rock specimen. After the pressure head contacts the surface of the rock specimen, when the pressure of the axial force sensor is displayed to be 2N, use force control to continue loading at a speed of 100N / s until the rock specimen is destroyed, and the shear test is completed.

[0048] 5) After the shear test of the rock specimen is completed, check the test data and select the record with the maximum load value as the failure load P. k , calculated based on the test data.

[0049] Case 1: When the prefabricated crack angle is 0°, the shear surface is subjected to force analysis, the length L1 of the shear surface is measured, and the shear surface area A1=0.1L1 is calculated based on the specimen thickness. In this case, the normal stress σ1 and shear stress τ1 on the shear surface are respectively,

[0050] σ1=0

[0051] τ1=P k1 / A1

[0052] Case 2: When the prefabricated crack angle is 15° on the left, the shear surface is subjected to force analysis, the length L2 of the shear surface is measured, and the shear surface area A2=0.1L2 is calculated based on the specimen thickness. In this case, the normal stress σ2 and shear stress τ2 on the shear surface are respectively,

[0053] σ2=P k2 ·sin20 / A2=0.342P k2 / A2

[0054] τ2=P k2 ·cos20 / A2=0.940P k2 / A2

[0055] Case 3: When the prefabricated crack angle is 30° on the right side, the shear surface is subjected to force analysis, the length L3 of the shear surface is measured, and the shear surface area A3=0.1L3 is calculated based on the specimen thickness. In this case, the normal stress σ3 and shear stress τ3 on the shear surface are respectively,

[0056] σ3=P k3 ·sin24 / A3=0.407P k3 / A3

[0057] τ3=P k3 ·cos24 / A3=0.914P k3 / A3

[0058] By analyzing the data, we can get the normal stress σ, shear stress τ and failure load P k Mathematical relationship, from Coulomb's law Get three points (σ1, τ1), (σ2, τ2), (σ3, τ3) composed of normal stress and shear stress. Connect the three points with a smooth curve on the σ-τ stress plane and draw the σ-τ relationship curve to obtain the shear strength parameter internal friction angle. Cohesion c.

[0059] 5) Embodiment 2

[0060] like Figure 1 , Figure 2 , Figure 4 As shown, the difference between the second embodiment and the first embodiment is that in the second embodiment, a prefabricated crack 9 is provided in the middle of the rock specimen 7, and the angle of the crack 9 is 15°.

[0061] Embodiment 3

[0062] like Figure 1 , Figure 2 , Figure 6 As shown, a prefabricated crack 10 is provided in the middle of the rock specimen 7, and the angle of the crack 10 is 30°.

Claims

1. A double-notch rock shear strength testing device, characterized in that: It includes a pressure system, a test piece device, a spring device, a roller group device and a control system; the test piece device is a processed double-notch rock test piece, the rock test piece is placed in the roller group device, the roller group device is placed at the center of the test machine press, a top pressure system for applying top pressure to the rock test piece is arranged above the test machine press, and side pressure systems for applying side pressure to the rock test piece are arranged on both sides of the test machine press, a set of spring devices are arranged in the two notches of the rock test piece, each set of spring devices includes a spring with a known elastic coefficient and an axial force sensor, and the two ends of the spring are respectively fixed on the top of the notch of the rock test piece and the axial force sensor, and the control system includes a computer host and a computer display, the axial force sensor is connected to the computer host, and the computer host is connected to the computer display; The double-notch rock shear strength test device performs the following method: A double-notch rock shear strength testing method, characterized by comprising the following steps: 1) Connect the lower end of the spring of the spring device to the axial force sensor, and place the two sets of spring devices into the two notches of the rock specimen respectively; 2) A lateral force sensor is fixed on each of the outermost steel plates of the roller assembly, and then the double-notched rock specimen is placed in the square frame of the roller assembly; 3) Connect the two axial force sensors in the notch of the rock specimen and the two lateral force sensors on the outermost steel plate of the roller assembly to the computer host; 4) Turn on the computer host and monitor, start the testing machine, and start recording the data collected by the axial force sensor and the lateral force sensor; use displacement control to make the lateral pressure head of the testing machine move closer to the two sides of the rock specimen. After the pressure head contacts the side surface of the rock specimen, when the pressure of the lateral force sensor is monitored to be 1N, use force control to load the lateral pressure to the test design value at a speed of 100N / s and keep it constant; also use displacement control to make the axial pressure head of the testing machine move closer to the surface of the rock specimen. After the pressure head contacts the surface of the rock specimen, when the pressure of the axial force sensor is displayed to be 2N, use force control to continue loading at a speed of 100N / s until the rock specimen is destroyed, that is, the shear test is completed; 5) After the shear test of the rock specimen is completed, check the test data and select the record with the maximum load value as the failure load P. k , calculated based on the test data; In the step 5): Case 1: When the prefabricated crack angle is 0°, the shear surface is subjected to force analysis, the length L1 of the shear surface is measured, and the shear surface area A1=0.1L1 is calculated based on the specimen thickness. In this case, the normal stress σ1 and shear stress τ1 on the shear surface are respectively, σ1 = 0 τ1=P k1 / A1 Case 2: When the prefabricated crack angle is 15° on the left, the shear surface is subjected to stress analysis, the length L2 of the shear surface is measured, and the shear surface area A2=0.1L2 is calculated based on the specimen thickness. In this case, the normal stress σ2 and shear stress τ2 on the shear surface are respectively, <h2 style=";text-align:left;direction:ltr">σ2=P<h2 style=";text-align:left;direction:ltr"> k2 <h2 style=";text-align:left;direction:ltr"> sin20 / A2=0.342P<h2 style=";text-align:left;direction:ltr"> k2 <h2 style=";text-align:left;direction:ltr"> / A2 τ2=P k2 ·cos20 / A2=0.940 P k2 / A2 Case 3: When the prefabricated crack angle is 30° on the right side, the shear surface is subjected to force analysis, the length L3 of the shear surface is measured, and the shear surface area A3=0.1L3 is calculated based on the specimen thickness. In this case, the normal stress σ3 and the shear stress τ3 on the shear surface are respectively, <h2 style=";text-align:left;direction:ltr">σ3 = P<h2 style=";text-align:left;direction:ltr"> k3 <h2 style=";text-align:left;direction:ltr"> sin24 / A3=0.407P<h2 style=";text-align:left;direction:ltr"> k3 <h2 style=";text-align:left;direction:ltr"> / A3 <h2 style=";text-align:left;direction:ltr">τ3=P<h2 style=";text-align:left;direction:ltr"> k3 <h2 style=";text-align:left;direction:ltr"> cos24 / A3=0.914P<h2 style=";text-align:left;direction:ltr"> k3 <h2 style=";text-align:left;direction:ltr"> / A3 By analyzing the data, we can get the normal stress σ, shear stress τ and failure load P k Mathematical relationship: Based on Coulomb's law τ=c+σtanϕ, we can get three points (σ1, τ1), (σ2, τ2), (σ3, τ3) composed of normal stress and shear stress. Connect the three points with a smooth curve on the σ-τ stress plane, and draw the σ-τ relationship curve, thus obtaining the shear strength parameters, internal friction angle ϕ and cohesion c.

2. The double-notch rock shear strength testing device according to claim 1 is characterized in that: The roller group device includes two L-shaped steel plates and two vertical steel plates. The two L-shaped steel plates are spliced ​​together to form a square frame for placing rock specimens. A vertical steel plate is provided on the outside of the two L-shaped steel plates. A lateral force sensor is attached to the outside of the vertical steel plates on both sides. A number of steel pipes are longitudinally provided from top to bottom between the outside of the L-shaped steel plate and the vertical steel plate. The steel pipes are fixed on the vertical steel plates. The lateral pressure system applies pressure on the vertical steel plates, which is transmitted to the L-shaped steel plates through the steel pipes to apply lateral pressure to the rock specimens.

3. The double-notch rock shear strength testing device according to claim 1, characterized in that: The two notches of the rock specimen are distributed on the left and right sides of the rock specimen, one above and one below.

4. The double-notch rock shear strength testing device according to claim 1, characterized in that: The rock specimen has a height of 200 mm, a width of 100 mm, and a thickness of 100 mm; a prefabricated crack is provided in the middle of the rock specimen, the crack length is 18 mm, and the crack angle is 0°~30°.

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