Coal rock single-side free surface plane strain compression test device and method

Abstract

The invention discloses a coal rock unilateral free surface plane strain compression test device and method, and relates to the technical field of rock mechanics and mine engineering.The coal rock unilateral free surface plane strain compression test device comprises a main base and supporting legs, a limiting column is fixedly installed on the main base, a pressing plate body driven by a hydraulic push rod is arranged on the limiting column, and a linear guide rail is further installed on the main base; a linear guide rail is arranged on the main base, the linear guide rail is provided with a displacement seat driven by a driving mechanism, a lateral baffle is further connected to the main base in a sliding mode, an observation frame driven by an adjusting mechanism is further arranged on the main base, and an experiment area used for containing a coal rock mass is jointly formed between the pressing plate body and the lateral baffle. During use, the hydraulic push rod drives the pressing plate main body to vertically apply pressure to simulate uniaxial compression, and meanwhile, the displacement seat is matched to drive the lateral baffles to extrude the two sides of a sample to simulate a direct shear test; the two stress states are combined to accurately simulate the actual stress condition of the coal and rock mass under the condition of a single-side free surface.

Description

Technical Field

[0001] This invention relates to the fields of rock mechanics and mining engineering, specifically to a device and method for a single-sided free-plane plane strain compression test of coal and rock. Background Technology

[0002] In underground space engineering, the mechanical properties of coal and rock masses are key factors affecting the safety and stability of the project.

[0003] The study of the mechanical properties of coal and rock masses is of crucial significance for engineering design, disaster prediction, and prevention. Single-sided free-face conditions are a common stress environment in underground space engineering, such as in tunnel excavation, roadway excavation, and slope excavation, where one side of the coal and rock mass is typically exposed to a free-face environment. Under these conditions, the stress distribution, deformation characteristics, and failure modes of the coal and rock mass differ significantly from those under conventional test conditions.

[0004] Currently, research on the mechanical properties of coal and rock mainly relies on conventional triaxial tests, uniaxial compression tests, and direct shear tests. However, while uniaxial compression tests are simple to operate, they neglect lateral constraints and cannot reflect the lateral stress on coal and rock masses in actual engineering. Direct shear tests focus on studying the shear strength of coal and rock, but they also cannot simulate the overall stress state under unilateral free surface conditions. Therefore, they cannot effectively simulate the stress state and working conditions of coal and rock masses under unilateral free surface conditions in underground space engineering. Furthermore, the observation equipment used is mostly fixed support, which makes it difficult to adjust the viewing angle and creates many blind spots, making it difficult to fully observe the changes in the fracture surface of coal and rock masses. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention is proposed.

[0006] Therefore, the purpose of this invention is to provide a plane strain compression test device and method for coal and rock on a single-sided free surface. The problem to be solved is that the uniaxial compression test and direct shear test used in the existing research on the mechanical properties of coal and rock cannot simulate the overall stress state of coal and rock mass under the condition of a single-sided free surface. Thus, they cannot effectively simulate the real stress state and working conditions of coal and rock mass in underground space engineering under the condition of a single-sided free surface. Moreover, due to the use of fixed support, the viewing angle is difficult to adjust, there are many blind spots, and it is difficult to fully observe the changes in the fracture surface of coal and rock mass.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a coal and rock single-sided free surface plane strain compression test device, comprising a main base and legs, wherein vertically distributed limiting columns are fixedly installed on the main base, and a pressure plate body driven by a hydraulic push rod is provided on the limiting columns; a linear guide rail is also fixedly installed on the main base, and a displacement seat driven by a driving mechanism is provided on the linear guide rail; the displacement seats are slidably connected to both ends of the linear guide rail; a side baffle corresponding to the displacement seat is also slidably connected on the main base; and an observation frame driven by an adjustment mechanism is also provided on the main base. The pressure plate bodies are distributed in parallel above the main base, and the pressure plate bodies are located between the side baffles. The pressure plate bodies and the side baffles together form an experimental area for placing coal and rock bodies. An observation surface for observing the free surface is provided on the side of the experimental area away from the limiting column. A visual probe for recording the fracture of the observation surface is also provided on the observation frame.

[0008] As a preferred embodiment of the coal and rock single-sided free surface plane strain compression test device of the present invention, wherein: the displacement seat is provided with an integrally formed traction slider, and one end of the traction slider extends into the linear guide rail, the displacement seat is slidably connected to the linear guide rail through the traction slider, and an auxiliary wheel is also connected to the side of the displacement seat away from the traction slider, and the auxiliary wheel is in contact with the surface of the main base.

[0009] As a preferred embodiment of the single-sided free surface plane strain compression test device for coal and rock according to the present invention, the driving mechanism includes a traction motor fixedly installed on a linear guide rail, and the output shaft of the traction motor is drivenly connected to a bidirectional screw. The bidirectional screw is rotatably connected to the linear guide rail through the traction motor, and the two sets of traction sliders extend to one end of the linear guide rail and are respectively threadedly connected to the two ends of the bidirectional screw.

[0010] As a preferred embodiment of the single-sided free surface plane strain compression test device for coal and rock according to the present invention, the hydraulic push rod is fixedly installed at the top of the limiting column, and the pressure plate body is fixedly connected to the piston shaft of the hydraulic push rod. The two sides of the pressure plate body are respectively provided with integrally formed side protrusions, and the inner side of the side baffle is respectively provided with guide grooves adapted to the side protrusions. The pressure plate body is slidably connected in the guide grooves through the side protrusions.

[0011] As a preferred embodiment of the coal and rock single-sided free surface plane strain compression test device of the present invention, wherein: the limiting column and the side baffle are both provided with pressure sensors for monitoring pressure changes on the side near the test area, and the pressure sensors are respectively connected to the external computing device by wires.

[0012] As a preferred embodiment of the coal and rock single-sided free surface plane strain compression test device of the present invention, the observation frame is located between the lateral baffles, and the visual probe is located on the side of the observation frame closer to the observation surface. The visual probes are arranged in concentric circles with multiple densities on the observation frame. The visual probes are also connected to the external computing device via wires. An integrally formed lifting slide is also provided on the side of the observation frame away from the visual probe.

[0013] As a preferred embodiment of the coal and rock single-sided free surface plane strain compression test device of the present invention, the adjustment mechanism includes an adjustment slide block slidably connected to the main base, and an adjustment lever is rotatably connected to the adjustment slide block, the end of the adjustment lever away from the adjustment slide block being threadedly connected to a protrusion on the main base; The guide frame is fixedly installed at one end of the adjusting slide that protrudes from the main base. The observation frame is slidably connected to the guide frame via the lifting slide. A lifting lever is rotatably connected to the guide frame, and the end of the lifting lever away from the guide frame is threadedly connected to the lifting slide.

[0014] A method for using a single-sided free-plane plane strain compression testing device for coal and rock, characterized by comprising the following steps: Step 1: When using the device, first start the traction motor to drive the bidirectional screw to rotate, causing the displacement seat to move the side baffles in opposite directions, thus expanding the experimental area. Step 2: Place the cut rectangular coal and rock sample, which has the same length and width and a height twice the length and width, vertically on the main base and lean it against the limiting post. Step 3: After placing the sample into the test area, rotate the bidirectional screw in the opposite direction to bring the lateral baffle closer to the confining coal and rock mass, forming a semi-enclosed space; Step 4: Activate the hydraulic push rod to apply pressure to the main body of the pressure plate to simulate uniaxial compression, and the side baffles squeeze both sides of the sample to simulate direct shear, while the pressure sensor transmits data; Step 5: Adjust the position of the observation frame so that the visual probe can record the fracture of the observation surface.

[0015] In summary, the present invention has at least one of the following beneficial effects: 1. This invention simulates uniaxial compression by driving the pressure plate body vertically with a hydraulic push rod, while simultaneously using a displacement seat to drive the lateral baffle to squeeze both sides of the sample to simulate a direct shear test. The combination of these two stress states can accurately simulate the actual stress situation of coal and rock mass under unilateral free surface conditions.

[0016] 2. The present invention uses a drive mechanism to flexibly adjust the width of the experimental area by moving the side baffles. This can accommodate the placement of cuboid coal and rock samples with the same length and width but a height twice the length and width. The side baffles can also be moved closer together to stabilize and restrict the sample, keeping it in a semi-enclosed space and ensuring the stability of the sample position during the test.

[0017] 3. This invention adjusts the horizontal and vertical positions of the observation frame through an adjustment mechanism, and combined with a visual probe arranged in concentric circles at multiple densities, it can record the fracture situation of the coal and rock mass observation surface from all directions, effectively reducing blind spots in observation, and is especially adaptable to the fracture morphology of rocks that gradually fracture from the middle outward after being compressed. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0019] Figure 1 This is a three-dimensional structural diagram of the present invention; Figure 2 This is a cross-sectional perspective view of the present invention; Figure 3 This is a structural diagram showing the installation of the drive mechanism and the side baffle of the present invention. Figure 4 This is a structural diagram showing the installation of the displacement seat and the side baffle of the present invention. Figure 5 This is a structural diagram showing the installation of the limiting post and pressure plate body of the present invention: Figure 6 This is a structural diagram showing the installation of the adjustment mechanism and the observation frame of the present invention.

[0020] Explanation of reference numerals in the attached figures: 1. Main base; 2. Support leg; 3. Limiting post; 4. Hydraulic push rod; 5. Pressure plate body; 501. Side protrusion; 6. Linear guide rail; 7. Displacement seat; 701. Traction slider; 702. Auxiliary wheel; 8. Side baffle; 801. Guide groove; 9. Pressure sensor; 10. Traction motor; 11. Bidirectional screw; 12. Observation frame; 1201. Vision probe; 1202. Lifting slide; 13. Adjusting lever; 14. Adjusting slide; 1401. Guide frame; 15. Lifting lever. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] This invention discloses a device and method for a single-sided free-plane plane strain compression test of coal and rock.

[0023] Example 1 Reference Figure 1-6 This invention provides a first embodiment of a coal and rock single-sided free surface plane strain compression test device and method. The device includes a main base 1 and support legs 2. Vertically distributed limiting columns 3 are fixedly installed on the main base 1, and each limiting column 3 has a pressure plate body 5 driven by a hydraulic push rod 4. A linear guide rail 6 is also fixedly installed on the main base 1, and the linear guide rail 6 has displacement seats 7 driven by a driving mechanism. The displacement seats 7 are slidably connected to both ends of the linear guide rail 6. The main base 1 also has slidably connected to the displacement seats. The main base 1 is equipped with an observation frame 12 driven by an adjustment mechanism, and the side baffles 8 corresponding to the base 7. The pressure plate body 5 is distributed parallel above the main base 1 and is located between the side baffles 8. The pressure plate body 5 and the side baffles 8 together form an experimental area for placing coal and rock mass. An observation surface for observing the free surface is provided on the side of the experimental area away from the limiting column 3. The observation frame 12 is also equipped with a visual probe 1201 for recording the fracture of the observation surface. The main base 1 serves as the installation foundation of the entire device and works with the support legs 2 to ensure stability during the detection process. The limiting column 3 not only provides structural support but also vertically limits the coal and rock mass to be tested, preventing it from loosening or shifting. The hydraulic push rod 4 provides stable and precisely controllable pressure to the pressure plate body 5, equivalent to a traditional uniaxial compression test. The linear guide rail 6 provides a precise track for the sliding of the displacement seat 7, ensuring the linearity of its movement and facilitating the placement and limiting of the coal and rock mass. The movement of the displacement seat 7 drives the lateral baffle 8 to move synchronously, thereby compressing both sides of the coal and rock mass sample, equivalent to a traditional direct shear test. The observation frame 12 can be adjusted to change the observation position according to the experimental requirements through the adjustment mechanism, thereby reducing the blind spot of observation. The experimental area formed by the pressure plate body 5 and the side baffle 8 is used to place the coal and rock mass, and together with the limiting column 3 and the main base 1, it forms a semi-enclosed space for storing the observation surface. The setting of the observation surface ensures that the changes of the free surface of the coal and rock mass can be clearly observed during the experiment. The visual probe 1201 on the observation frame 12 is responsible for recording the fracture of the coal and rock mass observation surface in real time, thereby effectively simulating the stress state and working conditions of the coal and rock mass in underground space engineering under the condition of a single free surface.

[0024] The displacement seat 7 is provided with an integrally formed traction slider 701, and one end of the traction slider 701 extends into the linear guide rail 6. The displacement seat 7 is slidably connected to the linear guide rail 6 through the traction slider 701. An auxiliary wheel 702 is also connected to the side of the displacement seat 7 away from the traction slider 701, and the auxiliary wheel 702 is in contact with the surface of the main base 1. The displacement seat 7 forms a stable sliding connection with the linear guide rail 6 through the traction slider 701, which ensures the accuracy of the displacement seat 7 during movement. The auxiliary wheel 702 can effectively share the pressure of the displacement seat 7 on the linear guide rail 6, reduce sliding friction, and make the movement of the displacement seat 7 smoother and more stable.

[0025] The drive mechanism includes a traction motor 10 fixedly mounted on the linear guide rail 6, and the output shaft of the traction motor 10 is driven by a bidirectional screw 11. The bidirectional screw 11 is rotatably connected to the linear guide rail 6 through the traction motor 10, and two sets of traction sliders 701 extend to one end in the linear guide rail 6 and are respectively threadedly connected to the two ends of the bidirectional screw 11. The traction motor 10 can drive the bidirectional screw 11 to rotate, and the two sets of traction sliders 701 will move towards or away from each other along the linear guide rail 6, thereby driving the displacement seat 7 to move synchronously, realizing the adjustment of the distance between the side baffles 8, which facilitates the placement of coal and rock mass or the application of pressure to the side of coal and rock mass.

[0026] The hydraulic push rod 4 is fixedly installed on the top of the limiting post 3, and the pressure plate body 5 is fixedly connected to the piston shaft of the hydraulic push rod 4. The two sides of the pressure plate body 5 are respectively provided with integrally formed side protrusions 501. The inner side of the side baffle 8 is respectively provided with guide grooves 801 that are adapted to the side protrusions 501. The pressure plate body 5 is slidably connected in the guide grooves 801 through the side protrusions 501. The hydraulic push rod 4 can provide vertical pressure to the coal and rock mass through the pressure plate body 5. The pressure plate body 5 can maintain vertical movement through the cooperation of the side protrusions 501 and the guide grooves 801, and increase the connection stability between the pressure plate body 5 and the side baffle 8, so as to avoid deviation or shaking during the application of pressure.

[0027] Pressure sensors 9 for monitoring pressure changes are installed on the side of the limiting column 3 and the side baffle 8 near the test area. The pressure sensors 9 are connected to the external computing device by wires. The pressure sensors 9 can sense the pressure generated by the coal and rock mass on the limiting column 3 and the side baffle 8 in real time during the compression process. The pressure sensors 9 transmit the pressure data they monitor to the external computing device in a timely manner through wires.

[0028] The observation frame 12 is located between the side baffles 8, and the visual probe 1201 is located on the side of the observation frame 12 closer to the observation surface. The visual probe 1201 is arranged in concentric circles with multiple densities on the observation frame 12. The visual probe 1201 is also connected to the external computing device via wires. The side of the observation frame 12 away from the visual probe 1201 is also provided with an integrally formed lifting slide 1202. The concentric circle multi-density layout of the visual probe 1201 can record the observation surface from multiple angles and all directions, thereby adapting to the pressure applied to the rock by the pressure plate body 5, and the rock fracture from the middle outwards from the fracture point or surface.

[0029] The adjustment mechanism includes an adjustment slide 14 slidably connected to the main base 1, and an adjustment lever 13 rotatably connected to the adjustment slide 14. The end of the adjustment lever 13 away from the adjustment slide 14 is threadedly connected to a protrusion on the main base 1. A guide frame 1401 is fixedly mounted on the end of the adjustment slide 14 protruding from the main base 1. The observation frame 12 is slidably connected to the guide frame 1401 via a lifting slide 1202. A lifting lever 15 is rotatably connected to the guide frame 1401, and the end of the lifting lever 15 away from the guide frame 1401 is threadedly connected to the main base 1. The lifting slide 1202 is threadedly connected, and the adjusting slide 14 can slide horizontally on the main base 1, driving the observation frame 12 to adjust its horizontal position. The adjusting lever 13 is threadedly connected to the protrusion on the main base 1, which can also lock the horizontal position after adjustment. When the lifting lever 15 is rotated, it can drive the observation frame 12 to slide up and down along the guide frame 1401, realizing the vertical position adjustment of the observation frame 12. The position of the observation frame 12 can be flexibly adjusted to ensure that the visual probe 1201 is always in the best observation state.

[0030] When conducting a single-sided free-plane plane strain compression test on coal and rock using the device, the coal and rock must first be cut into cuboid specimens with the same length and width as the main body of the pressure plate, but with a height twice the length and width. The specimens are then placed vertically on the main base 1, so that the coal and rock specimens lean vertically against the limiting post 3. During this process, the traction motor 10 in the drive mechanism drives the bidirectional screw 11 to rotate. Since the threads at both ends of the bidirectional screw 11 are opposite, the two sets of traction sliders 701 that are threaded with the bidirectional screw 11 will drive the displacement seat 7 to move in opposite directions, thereby driving the side baffles 8 to move synchronously. This adjusts the width of the test area, and the coal and rock specimens are placed in the test area. When the traction motor 10 drives the bidirectional screw 11 to rotate in the opposite direction, the side baffles 8 move closer to each other to restrict the coal and rock. At this time, the coal and rock are restricted in a semi-enclosed space formed by the limiting post 3 and the main base 1, which also contains the observation surface. Pressure is applied to the coal and rock mass. The hydraulic push rod 4 on the limiting column 3 provides stable and precisely controllable pressure to the pressure plate body 5, so that the pressure plate body 5 slides vertically in the guide groove 801 of the lateral baffle 8 through the side protrusions 501 on both sides, simulating the operation of the traditional uniaxial compression test. As the displacement seat 7 moves closer to each other on the main base 1 with the cooperation of the auxiliary wheel 702, the corresponding lateral baffle 8 squeezes the coal and rock mass on both sides, simulating the stress situation of the traditional direct shear test. During the test, the pressure sensor 9 on the limiting column 3 and the lateral baffle 8 senses the pressure generated by the coal and rock mass in real time and transmits the data to the external computing device through the wire. When observing the free surface fracture state of the coal and rock mass, the sliding block 14 is adjusted to slide horizontally on the main base 1, and the horizontal position is locked by the adjusting lever 13. The lifting lever 15 drives the observation frame 12 to slide up and down along the guide frame 1401 to achieve vertical adjustment, thereby reducing the blind spot of observation. The visual probes 1201 arranged in concentric circles on the observation frame 12 can record the fracture of the coal and rock mass observation surface in real time. In particular, it can adapt to the fracture points or surfaces that appear in the rock under pressure, starting from the middle and gradually moving outward, thereby reducing the blind spot of observation. Moreover, the shape of the rock fracture surface projected is similar to a U-shape, and the fracture starts from the middle of the fracture surface and moves obliquely downward.

[0031] A method for using a single-sided free-plane plane strain compression testing device for coal and rock includes the following steps: Step 1: When using the device, first start the traction motor 10 to drive the bidirectional screw 11 to rotate, so that the displacement seat 7 drives the side baffle 8 to move in opposite directions, thereby expanding the experimental area. Step 2: Place the cut rectangular coal and rock sample, which has the same length and width and a height twice the length and width, vertically on the main base 1 and lean it against the limiting column 3. Step 3: After placing the sample into the test area, rotate the bidirectional screw 11 in the opposite direction to bring the lateral baffle 8 close to the confined coal and rock mass, forming a semi-enclosed space. Step 4: Activate the hydraulic push rod 4 to apply pressure to the pressure plate body 5 to simulate uniaxial compression, the side baffle 8 squeezes the two sides of the sample to simulate direct shear, and the pressure sensor 9 transmits data. Step 5: Adjust the position of the observation frame 12 so that the visual probe 1201 can record the fracture of the observation surface.

[0032] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A plane strain compression test apparatus for a single-sided free surface of coal and rock, characterized in that: Includes a main base (1) and a support leg (2). Vertically distributed limiting posts (3) are fixedly installed on the main base (1), and a pressure plate body (5) driven by a hydraulic push rod (4) is provided on the limiting posts (3). A linear guide rail (6) is also fixedly installed on the main base (1), and a displacement seat (7) driven by a driving mechanism is provided on the linear guide rail (6). The displacement seat (7) is slidably connected to both ends of the linear guide rail (6), and a side baffle (8) corresponding to the displacement seat (7) is also slidably connected on the main base (1). An observation frame (12) driven by an adjustment mechanism is also provided on the main base (1). The pressure plate body (5) is distributed in parallel above the main base (1), and the pressure plate body (5) is located between the side baffles (8). The pressure plate body (5) and the side baffles (8) together form an experimental area for placing coal and rock bodies. An observation surface for observing the free surface is provided on the side of the experimental area away from the limiting column (3). A visual probe (1201) for recording the fracture of the observation surface is also provided on the observation frame (12).

2. The coal and rock single-sided free surface plane strain compression test device according to claim 1, characterized in that, The displacement seat (7) is provided with an integrally formed traction slider (701), and one end of the traction slider (701) extends into the linear guide rail (6). The displacement seat (7) is slidably connected to the linear guide rail (6) through the traction slider (701). An auxiliary wheel (702) is also connected to the side of the displacement seat (7) away from the traction slider (701), and the auxiliary wheel (702) is in contact with the surface of the main base (1).

3. The coal and rock single-sided free surface plane strain compression test device according to claim 2, characterized in that, The drive mechanism includes a traction motor (10) fixedly mounted on a linear guide rail (6), and the output shaft of the traction motor (10) is connected to a bidirectional screw (11). The bidirectional screw (11) is rotatably connected to the linear guide rail (6) through the traction motor (10), and the two sets of traction sliders (701) extend to one end of the linear guide rail (6) and are respectively threaded to both ends of the bidirectional screw (11).

4. The coal and rock single-sided free surface plane strain compression test device according to claim 1, characterized in that, The hydraulic push rod (4) is fixedly installed on the top of the limiting post (3), and the pressure plate body (5) is fixedly connected to the piston shaft of the hydraulic push rod (4). The two sides of the pressure plate body (5) are respectively provided with integrally formed side protrusions (501). The inner side of the side baffle (8) is respectively provided with guide grooves (801) that are adapted to the side protrusions (501), and the pressure plate body (5) is slidably connected in the guide grooves (801) through the side protrusions (501).

5. The coal and rock single-sided free surface plane strain compression test device according to claim 4, characterized in that, The limiting post (3) and the side baffle (8) are both equipped with pressure sensors (9) for monitoring pressure changes on the side near the test area, and the pressure sensors (9) are respectively connected to the external computing device via wires.

6. The coal and rock single-sided free surface plane strain compression test device according to claim 1, characterized in that, The observation frame (12) is located between the side baffles (8), and the visual probe (1201) is located on the side of the observation frame (12) closer to the observation surface. The visual probe (1201) is arranged in concentric circles with multiple densities on the observation frame (12). The visual probe (1201) is also connected to the external computing device via wires. The side of the observation frame (12) away from the visual probe (1201) is also provided with an integrally formed lifting slide (1202).

7. The coal and rock single-sided free surface plane strain compression test apparatus according to claim 6, characterized in that, The adjustment mechanism includes an adjustment slide (14) slidably connected to the main base (1), and an adjustment lever (13) is rotatably connected to the adjustment slide (14). The end of the adjustment lever (13) away from the adjustment slide (14) is threadedly connected to a protrusion on the main base (1). The adjusting slide (14) is fixedly mounted with a guide frame (1401) at one end protruding from the main base (1). The observation frame (12) is slidably connected to the guide frame (1401) via a lifting slide (1202). A lifting lever (15) is rotatably connected to the guide frame (1401), and the end of the lifting lever (15) away from the guide frame (1401) is threadedly connected to the lifting slide (1202).

8. A method of using a coal and rock single-sided free surface plane strain compression test apparatus, which is applied to the coal and rock single-sided free surface plane strain compression test apparatus of claim 7, characterized in that: Includes the following steps: Step 1: When using the device, first start the traction motor (10) to drive the bidirectional screw (11) to rotate, so that the displacement seat (7) drives the side baffle (8) to move in opposite directions, thereby expanding the experimental area; Step 2: Place the cut rectangular coal and rock sample, which has the same length and width and a height twice the length and width, vertically on the main base (1) and vertically lean against the limiting column (3); Step 3: After placing the sample into the test area, rotate the bidirectional screw (11) in the opposite direction to bring the side baffle (8) close to the confining coal and rock mass, forming a semi-enclosed space; Step 4: Start the hydraulic push rod (4) to apply pressure to the main body of the pressure plate (5) to simulate uniaxial compression, the side baffle (8) squeezes the two sides of the sample to simulate direct shear, and the pressure sensor (9) transmits data. Step 5: Adjust the position of the observation frame (12) so that the visual probe (1201) can record the fracture of the observation surface.

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