Device and method for measuring shear strength of coal seam under gas seepage and pressure

Abstract

The invention discloses a measuring device and method for the shear strength of a coal seam under gas seepage and pressure, which includes a shear combination box, a fixed steel support, a gas inlet bottle, a jack and a jack driving controller. A pushing point on the outer wall of the lower shear box is provided, and the jack driving controller controls the jack to perform pushing and shearing operations. A porous cushion layer and a rubber membrane are arranged at the top of the upper shear cavity of the upper shear box. A gas inlet conduit connected to the porous cushion layer is connected to the top of the upper shear box. The outlet of the gas inlet bottle is hermetically connected to the gas inlet conduit through a flexible rubber gas pipeline D. The invention realizes the simulation of the gas pressure test on the coal sample through the gas inlet bottle, inputs nitrogen into the axial pressure cavity through the nitrogen supply bottle to simulate the normal pressure of the coal sample, and performs the shearing operation on the coal sample by the action of the jack on the lower shear box, and then can respectively realize the test and research on the shear strength parameters of the coal sample under different conditions.

Description

Technical Field

[0001] The present invention relates to the field of research on the mechanical properties of gas-containing coal seams, and particularly to a device and method for measuring the shear strength of coal seams under gas seepage and pressure. Background Art

[0002] With the development of highway construction, there are more and more highway tunnels passing through coal measures strata. Coal measures strata are usually rich in gas. When a tunnel passes through coal measures strata, the gas in the strata will gush out into the tunnel excavation space, resulting in the presence of gas in the tunnel working space and forming a gas tunnel. Due to the extremely poor condition of coal-bearing rock strata as surrounding rocks, the engineering geological conditions of soft surrounding rocks in coal measures strata are very complex. During tunnel excavation, large deformations of surrounding rocks and tunnel collapses may occur at any time. At the same time, the construction of gas tunnels has relatively high construction risks, and there are specific disasters such as gas explosions, personnel poisoning and asphyxiation, and coal and gas outbursts caused by gas, resulting in a large number of casualties and property losses, increasing the tunnel construction cost, delaying the tunnel construction period, and at the same time may also form a bad social impact, and the consequences of accidents are serious. There have been many major safety accidents at home and abroad caused by poor tunnel construction management. To ensure the construction safety of gas tunnels, during the construction of tunnels passing through coal seams, it is often necessary to carry out stability analysis of surrounding rocks of tunnels passing through coal measures strata and research on coal uncovering and outburst prevention technologies through a large number of numerical simulation methods or theoretical calculation means, optimize the tunnel support design and excavation plan, and judge the stability of gas drainage boreholes. At this time, it is necessary to know the shear mechanical properties and shear strength parameter indexes (cohesion and internal friction angle) of gas-containing coal seams.

[0003] The mechanical properties of gas-rich coal seams are very complex. The flow of gas in coal seams is affected by multiple factors such as adsorption and desorption, gas pressure, formation stress, groundwater and temperature. On the one hand, the coal matrix shrinks and deforms due to gas desorption in the coal seam, resulting in an increase in permeability; on the other hand, due to the decrease in gas pressure, the effective stress increases, and the compression deformation of the coal body causes the permeability to decrease. There is a strong dynamic gas-solid coupling relationship between coal and rock masses and gas. Therefore, the influence of in-situ stress, gas pressure, and coal seam permeability on the shear mechanical properties of gas-containing coal seams is very crucial. The direct shear test of geotechnical engineering is the most direct and commonly used method to determine the shear mechanical properties and shear strength indexes of geotechnical materials. However, the current direct shear test instrument for geotechnical tests cannot study the influence of gas pressure and gas seepage in coal seams on their shear mechanical properties. Summary of the Invention

[0004] The object of the present invention is to overcome the technical problems pointed out in the background art, and provide a device and method for measuring the shear strength of coal seams under gas seepage and pressure. The porous cushion is used to receive the gas from the gas inlet cylinder, and simulate the gas pressure test on the coal sample. The vacuum pump is used to evacuate the coal sample to simulate gas seepage. The nitrogen gas cylinder is used to input nitrogen gas into the axial pressure cavity to simulate the normal pressure of the coal sample. The shear box is actuated by a jack to perform the shearing operation on the coal sample, and then the shear strength parameter test research of the coal sample under different conditions can be realized respectively.

[0005] The object of the present invention is achieved by the following technical solutions:

[0006] A device for measuring the shear strength of coal seams under gas seepage and pressure, comprising a shear combination box composed of an upper shear box and a lower shear box. The upper shear box has openings at both the top and the bottom, and the upper shear cavity of the upper shear box and the lower shear cavity of the lower shear box form a coal sample combination cavity. The present invention also includes a fixed steel bracket, a gas inlet cylinder, a jack and a jack driving controller. The upper shear box is fixedly connected to the fixed steel bracket. The jack has a jack telescopic arm, and a lower shear box pushing point corresponding to the end of the jack telescopic arm is provided on the outer side wall of the lower shear box. The jack driving controller controls the jack to perform the pushing and shearing operation. A porous cushion is provided at the top of the upper shear cavity of the upper shear box, and a rubber film is used to seal and cover the top of the porous cushion. A gas inlet conduit connected to the porous cushion is provided at the top of the upper shear box. The outlet of the gas inlet cylinder is hermetically connected to the gas inlet conduit through a flexible rubber gas pipeline D. A gas control ball valve A is provided at the outlet of the gas inlet cylinder, and a gas pressure gauge A is also installed on the flexible rubber gas pipeline D.

[0007] To better implement the present invention, the present invention also includes a shear box steel support. A steel bottom plate is fixed on the top of the shear box steel support. The shear combination box is placed on the steel bottom plate. A jack steel support is fixed on the top of the steel bottom plate. The jack is detachably fixed on the top of the jack steel support. A steel ball auxiliary moving layer is provided between the bottom of the lower shear box and the steel bottom plate. The steel ball auxiliary moving layer is composed of a number of steel balls.

[0008] Preferably, the present invention also includes a vacuum pump. A lower exhaust steel conduit is communicated at the bottom of the lower shear box. The inlet of the vacuum pump is hermetically connected to the lower exhaust steel conduit through a flexible rubber gas pipeline group.

[0009] Preferably, the present invention also includes an axial pressure cavity. The axial pressure cavity has an axial pressure chamber. The axial pressure cavity and the upper shear box overlap up and down, and the bottom of the axial pressure cavity completely wraps and seals the rubber film and the porous cushion.

[0010] Preferably, the present invention further includes a nitrogen gas supply cylinder. An intake steel conduit is connected to the top of the axial pressure cavity in a communicating manner. The outlet of the nitrogen gas supply cylinder and the intake steel conduit are hermetically connected through a flexible rubber gas pipeline A.

[0011] Preferably, a gas control ball valve B is installed at a position of the flexible rubber gas pipeline A close to the outlet of the nitrogen gas supply cylinder, and a gas pressure gauge B is installed at a position of the flexible rubber gas pipeline A close to the intake steel conduit.

[0012] Preferably, a steel top cover is connected to the top of the axial pressure cavity. A left tempered glass baffle and a right tempered glass baffle are detachably connected between the steel top cover and the steel bottom plate. The left tempered glass baffle and the right tempered glass baffle together form a glass baffle assembly, and the glass baffle assembly forms a sealed accommodation cavity.

[0013] Preferably, the flexible rubber gas pipeline group includes a flexible rubber gas pipeline B, a left exhaust conduit, and a flexible rubber gas pipeline C. The left exhaust conduit is installed through the left tempered glass baffle. The flexible rubber gas pipeline B is connected between the vacuum pump and the left exhaust conduit. The flexible rubber gas pipeline C is connected between the vacuum pump and the lower exhaust steel conduit. A gas control ball valve C and a gas pressure gauge C are installed on the flexible rubber gas pipeline B.

[0014] Preferably, the jack driving controller and the jack are connected by a wire. The wire passes through the right tempered glass baffle, and a rubber conduit and a steel conduit for protecting the wire are provided on the right tempered glass baffle.

[0015] A measuring method for a measuring device using gas seepage and shear strength of coal seams under pressure, the method comprising:

[0016] A. Measuring the shear strength of a coal sample under the action of coal seam gas pressure: Making the collected coal sample into a coal sample that matches the coal sample combination cavity, placing the coal sample in the coal sample combination cavity of the shear combination box, opening the gas control ball valve A, inputting gas into the porous cushion through the gas inlet cylinder for the coal seam, and the gas passes through the porous cushion to evenly apply pressure to the coal sample; observing the gas pressure gauge A on the flexible rubber gas pipeline D until the gas pressure gauge A shows that the gas pressure of the gas for the coal seam reaches the set value F1 of the gas pressure for the coal seam and remains stable for a time H1; starting the jack driving controller, controlling the jack by the jack driving controller to gradually increase the jacking force and push the lower shear box to perform a shearing movement, and monitoring and obtaining the jacking force data when the coal sample starts to move under the jacking, then controlling the jack to maintain the jacking, and recording the corresponding data of the jacking force and the jacking displacement;

[0017] B. Measurement of the shear strength of coal samples under coal seam gas pressure and gas seepage: Make the collected coal samples into coal samples that match the coal sample combination cavity, place the coal samples in the coal sample combination cavity of the shear combination box, open the gas control ball valve A, input gas into the porous cushion through the gas inlet cylinder for the gas, and the gas evenly exerts pressure on the coal samples through the porous cushion. At the same time, start the vacuum pump and conduct air extraction treatment on the coal sample combination cavity, generating up-and-down gas seepage in the coal samples; observe the gas pressure gauge A on the flexible rubber gas pipeline D until the gas pressure gauge A shows that the gas pressure reaches the gas pressure set value F2 and remains stable for a time H2; start the jack drive controller, control the jack through the jack drive controller to gradually increase the jacking force and push the lower shear box to perform a shearing motion, and monitor and obtain the jacking force data when starting to push and move the coal sample, then control the jack to maintain the jacking force and record the corresponding data of the jacking force and the jacking displacement.

[0018] C. Measurement of the shear strength of coal samples under the normal pressure of the coal seam: Make the collected coal samples into coal samples that match the coal sample combination cavity, place the coal samples in the coal sample combination cavity of the shear combination box, open the gas control ball valve B, input nitrogen into the axial pressure chamber of the axial pressure cavity through the nitrogen supply cylinder, and the nitrogen evenly exerts pressure on the porous cushion in the axial pressure chamber and transmits it to the top of the coal sample; observe the gas pressure gauge B until the gas pressure gauge B shows that the nitrogen pressure reaches the nitrogen pressure set value F3 and remains stable for a time H3; start the jack drive controller, control the jack through the jack drive controller to gradually increase the jacking force and push the lower shear box to perform a shearing motion, and monitor and obtain the jacking force data when starting to push and move the coal sample, then control the jack to maintain the jacking force and record the corresponding data of the jacking force and the jacking displacement.

[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0020] (1) The present invention receives the gas from the gas inlet cylinder for the gas through the porous cushion and realizes the simulation of the gas pressure test on the coal samples. The air extraction treatment is carried out on the coal samples through the vacuum pump to simulate gas seepage. Nitrogen is input into the axial pressure cavity through the nitrogen supply cylinder to simulate the normal pressure of the coal samples. The lower shear box is acted on by the jack to realize the shearing operation of the coal samples, and then the test research on the shear strength parameters of the coal samples under different conditions can be realized respectively.

[0021] (2) The present invention forms a sealing cover with the left and right tempered glass baffles to keep air leakage from occurring during the shear test process. Gas seepage is formed in the coal seam test through the gas supply and air extraction operations, and gas pressure is applied to the coal seam, so that the true simulation of the shear-gas seepage coupling characteristics of coal and rock can be realized, the influence of gas pressure and coal seam permeability on the shear mechanical properties of the gas-containing coal seam can be studied, and basic data for the research on the stability of coal samples and the like can be further provided. Description of the Drawings

[0022] Figure 1 is the structural schematic diagram of the present invention;

[0023] Figure 2 is Figure 1 the partial enlarged schematic diagram at position A in

[0024] Among them, the names corresponding to the reference numerals in the drawings are as follows:

[0025] 1—nitrogen gas supply cylinder, 2—flexible rubber gas transmission pipe A, 3—ground, 4—fixed steel support, 5—vacuum pump, 6—flexible rubber gas transmission pipe B, 7—left tempered glass baffle, 8—left exhaust duct, 9—flexible rubber gas transmission pipe C, 10—axial pressure cavity, 11—intake steel pipe, 12—steel top cover, 13—rubber membrane, 14—porous cushion, 15—upper shear box, 16—lower shear box, 17—coal sample, 18—right tempered glass baffle, 19—jack steel support, 20—jack drive control wire, 21—shear box steel support; 22—flexible rubber gas transmission pipe D, 23—jack drive controller, 24—gas intake cylinder, 25—gas intake duct, 26—steel ball, 27—lower exhaust steel pipe, 28—steel bottom plate, 29—sealing bolt, 30—jack, 31—rubber pipe, 32—lower shear box pushing point, 33—jack telescopic arm, 34—steel pipe, 35—gas control ball valve A, 351—gas control ball valve B, 36—gas pressure gauge A, 361—gas pressure gauge B. Specific embodiments

[0026] The present invention will be further described in detail below in conjunction with embodiments:

[0027] Embodiment

[0028] Such as Figure 1 、 Figure 2As shown in the figure, a measuring device for the shear strength of coal seams under gas seepage and pressure includes a shear combination box composed of an upper shear box 15 and a lower shear box 16. The top and bottom of the upper shear box 15 are both open, and the upper shear cavity of the upper shear box 15 and the lower shear cavity of the lower shear box 16 form a coal sample combination cavity. The present invention also includes a fixed steel bracket 4, a gas inlet bottle 24, a jack 30, and a jack drive controller 23. The upper shear box 15 is connected and fixed to the fixed steel bracket 4. The jack 30 has a jack telescopic arm 33. A lower shear box push point 32 corresponding to the end of the jack telescopic arm 33 is provided on the outer side wall of the lower shear box 16. The jack drive controller 23 is used to set the control parameters of the jack and control the jack 30 to perform a pushing and shearing operation according to the control parameters. The control parameters include push pressure control (such as gradually increasing control of the set push pressure, set value of the push pressure) and monitoring (the jack drive controller 23 controls the push pressure of the jack 30 and records the push pressure), push speed (when performing shearing, the speed at which the jack 30 controls the movement of the jack telescopic arm 33), push distance control (setting the push limit distance) and monitoring (the jack drive controller 23 controls the jack telescopic arm 33 of the jack 30 to extend and perform a shearing operation on the coal sample 17. When the shearing pressure of the coal sample 17 is reached and the pushing continues beyond the shearing pressure, the jack telescopic arm 33 will perform a shearing operation on the coal sample 17, and at the same time, monitor the moving distance of the jack telescopic arm 33 to monitor the shearing displacement of the coal sample 17. Of course, a displacement sensor can also be set on the lower shear box 16 to monitor the shearing displacement). A porous cushion 14 is provided at the top of the upper shear cavity of the upper shear box 15, and a rubber membrane 13 is provided to seal and cover the top of the porous cushion 14. A gas inlet duct 25 communicating with the porous cushion 14 is connected to the top of the upper shear box 15. The outlet of the gas inlet bottle 24 is hermetically connected to the gas inlet duct 25 through a flexible rubber gas pipeline D22. A gas control ball valve A35 is provided at the outlet of the gas inlet bottle 24, and a gas pressure gauge A36 is also installed on the flexible rubber gas pipeline D22.

[0029] In some embodiments, the present invention also includes a shear box steel support 21. The shear box steel support 21 is placed on the ground 3, a steel bottom plate 28 is fixed to the top of the shear box steel support 21, the shear combination box is placed on the steel bottom plate 28, a jack steel support 19 is fixed to the top of the steel bottom plate 28, and the jack 30 is detachably fixed to the top of the jack steel support 19. A steel ball auxiliary moving layer is provided between the bottom of the lower shear box 16 and the steel bottom plate 28. The steel ball auxiliary moving layer is composed of a number of steel balls 26.

[0030] In some embodiments, the present invention also includes a vacuum pump 5. A lower exhaust steel duct 27 is communicated and provided at the bottom of the lower shear box 16. The inlet of the vacuum pump 5 is hermetically connected to the lower exhaust steel duct 27 through a flexible rubber gas pipeline group.

[0031] In some embodiments, the present invention further includes an axial pressure cavity 10, which has an axial pressure chamber. The axial pressure cavity 10 overlaps with the upper shear box 15 vertically, and the bottom of the axial pressure cavity 10 completely wraps and seals the rubber membrane 13 and the porous cushion 14.

[0032] In some embodiments, the present invention further includes a nitrogen gas supply cylinder 1. An intake steel conduit 11 is connected to the top of the axial pressure cavity 10 in a communicating manner. The outlet of the nitrogen gas supply cylinder 1 and the intake steel conduit 11 are hermetically connected through a flexible rubber gas pipeline A2.

[0033] In some embodiments, a gas control ball valve B351 is installed at the position of the flexible rubber gas pipeline A2 near the outlet of the nitrogen gas supply cylinder 1, and a gas pressure gauge B361 is installed at the position of the flexible rubber gas pipeline A2 near the intake steel conduit 11.

[0034] In some embodiments, a steel top cover 12 is connected to the top of the axial pressure cavity 10. A left tempered glass baffle 7 and a right tempered glass baffle 18 are detachably connected between the steel top cover 12 and the steel bottom plate 28 (as Figure 1 shown, the top of the left tempered glass baffle 7 and the top of the right tempered glass baffle 18 are detachably connected to the steel top cover 12 by a sealing bolt 29 in a threaded manner, and the bottom of the left tempered glass baffle 7 and the bottom of the right tempered glass baffle 18 are detachably connected to the steel bottom plate 28 by a sealing bolt 29 in a threaded manner). The left tempered glass baffle 7 and the right tempered glass baffle 18 jointly form a glass baffle assembly, which is equivalent to a sealing cover body, effectively ensuring that the gas will not leak during the test, and the glass baffle assembly forms a sealed accommodation cavity.

[0035] In some embodiments, the flexible rubber gas pipeline group includes a flexible rubber gas pipeline B6, a left exhaust conduit 8, and a flexible rubber gas pipeline C9. The left exhaust conduit 8 is installed through the left tempered glass baffle 7. The flexible rubber gas pipeline B6 is connected between the vacuum pump 5 and the left exhaust conduit 8, and the flexible rubber gas pipeline C9 is connected between the vacuum pump 5 and the lower exhaust steel conduit 27. A gas control ball valve C and a gas pressure gauge C are installed on the flexible rubber gas pipeline B6.

[0036] In some embodiments, the jack driving controller 23 and the jack 30 are connected by a wire (i.e., Figure 1 the jack driving control wire 20 shown in the figure). The wire passes through the right tempered glass baffle 18, and a rubber conduit 31 and a steel conduit 34 for protecting the wire are provided on the right tempered glass baffle 18.

[0037] A measuring method for a measuring device for measuring the shear strength of a coal seam under gas seepage and pressure, the method comprising:

[0038] A. Measurement of the shear strength of coal samples under the action of coal seam gas pressure: Make the collected coal samples into coal samples that fit the coal sample combination cavity, place the coal sample 17 in the coal sample combination cavity of the shear combination box, open the gas control ball valve A35, input gas through the gas inlet cylinder 24 of gas to the porous cushion layer 14, and the gas evenly exerts pressure on the coal sample through the porous cushion layer 14. Observe the gas pressure gauge A36 on the flexible rubber gas pipeline D22 until the gas pressure gauge A36 shows that the gas pressure reaches the gas pressure set value F1 and remains stable for the time H1. Start the jack drive controller 23, control the jack 30 through the jack drive controller 23 to gradually increase the jacking force and push the lower shear box 16 to perform a shearing motion, and monitor and obtain the jacking force data when starting to push and move the coal sample 17, then control the jack 30 to maintain the jacking force, and record the corresponding data of the jacking force and the jacking displacement.

[0039] B. Measurement of the shear strength of coal samples under the action of coal seam gas pressure and gas seepage: Make the collected coal samples into coal samples that fit the coal sample combination cavity, place the coal sample 17 in the coal sample combination cavity of the shear combination box, open the gas control ball valve A35, input gas through the gas inlet cylinder 24 of gas to the porous cushion layer 14, and the gas evenly exerts pressure on the coal sample through the porous cushion layer 14. At the same time, start the vacuum pump 5 and perform air extraction treatment on the coal sample combination cavity, and upper and lower gas seepage occurs in the coal sample 17. Observe the gas pressure gauge A36 on the flexible rubber gas pipeline D22 until the gas pressure gauge A36 shows that the gas pressure reaches the gas pressure set value F2 and remains stable for the time H2. Start the jack drive controller 23, control the jack 30 through the jack drive controller 23 to gradually increase the jacking force and push the lower shear box 16 to perform a shearing motion, and monitor and obtain the jacking force data when starting to push and move the coal sample 17, then control the jack 30 to maintain the jacking force, and record the corresponding data of the jacking force and the jacking displacement.

[0040] C. Measurement of the shear strength of coal samples under the normal pressure of coal seam: Make the collected coal samples into coal samples that fit the coal sample combination cavity, place the coal sample 17 in the coal sample combination cavity of the shear combination box, open the gas control ball valve B351, input nitrogen into the axial pressure chamber of the axial pressure cavity 10 through the nitrogen supply cylinder 1, and the nitrogen evenly exerts pressure on the porous cushion layer 14 in the axial pressure chamber and transmits it to the top of the coal sample 17. Observe the gas pressure gauge B361 until the gas pressure gauge B361 shows that the nitrogen pressure reaches the nitrogen pressure set value F3 and remains stable for the time H3. Start the jack drive controller 23, control the jack 30 through the jack drive controller 23 to gradually increase the jacking force and push the lower shear box 16 to perform a shearing motion, and monitor and obtain the jacking force data when starting to push and move the coal sample 17, then control the jack 30 to maintain the jacking force, and record the corresponding data of the jacking force and the jacking displacement.

[0041] Method A is to conduct the shear strength test and measurement of coal sample 17 under the action of gas pressure alone through the measuring device of the present invention. Method B is to conduct the shear strength test and measurement of coal sample 17 under the combined action of gas pressure and gas seepage through the measuring device of the present invention. Method C is to conduct the shear strength test and measurement of coal sample 17 under the action of normal pressure alone through the measuring device of the present invention. The present invention can also conduct combined tests on Method A, Method B, and Method C. For example, Method C is superimposed on Method A. The specific method is as follows:

[0042] Make the collected coal sample into a coal sample that fits the coal sample combination cavity, place coal sample 17 in the coal sample combination cavity of the shear combination box, open the gas control ball valve B351, and input nitrogen into the axial pressure chamber of the axial pressure cavity 10 through the nitrogen gas supply cylinder 1. The nitrogen gas evenly applies pressure to the porous cushion 14 in the axial pressure chamber and transmits it to the top of coal sample 17. At the same time, open the gas control ball valve A35, and input gas into the porous cushion 14 through the gas inlet cylinder 24. The gas passes through the porous cushion 14 and evenly applies pressure to the coal sample. Observe the gas pressure gauge A36 on the flexible rubber gas pipeline D22 until the gas pressure gauge A36 shows that the gas pressure reaches the gas pressure set value F4 and remains stable for a holding time H4. Start the jack driving controller 23, control the jack 30 to gradually increase the jacking force and push the lower shear box 16 to shear, monitor and obtain the jacking force data when starting to push and move coal sample 17, then control the jack 30 to maintain the jacking, and record the corresponding data of the jacking force and the jacking displacement.

[0043] Or Method C is superimposed on Method B. The specific method is as follows:

[0044] Make the collected coal sample into a coal sample that fits the coal sample combination cavity, place coal sample 17 in the coal sample combination cavity of the shear combination box, open the gas control ball valve B351, and input nitrogen into the axial pressure chamber of the axial pressure cavity 10 through the nitrogen gas supply cylinder 1. The nitrogen gas evenly applies pressure to the porous cushion 14 in the axial pressure chamber and transmits it to the top of coal sample 17. At the same time, open the gas control ball valve A35, and input gas into the porous cushion 14 through the gas inlet cylinder 24. The gas passes through the porous cushion 14 and evenly applies pressure to the coal sample; at the same time, start the vacuum pump 5 and conduct air extraction treatment on the coal sample combination cavity, and upper and lower gas seepage occurs in coal sample 17. Observe the gas pressure gauge A36 on the flexible rubber gas pipeline D22 until the gas pressure gauge A36 shows that the gas pressure reaches the gas pressure set value F5 and remains stable for a holding time H5. Start the jack driving controller 23, control the jack 30 to gradually increase the jacking force and push the lower shear box 16 to shear, monitor and obtain the jacking force data when starting to push and move coal sample 17, then control the jack 30 to maintain the jacking, and record the corresponding data of the jacking force and the jacking displacement.

[0045] In addition, the present invention can directly sample the gas-containing coal sample for the shear strength test of the actual gas-containing coal sample, and the method is as follows:

[0046] Place the gas-containing coal sample in the coal sample combination cavity of the shear combination box, start the jack drive controller 23, control the jack 30 to gradually increase the jacking force through the jack drive controller 23 and push the lower shear box 16 to perform a shearing movement, and monitor the jacking force data when starting to push and move the gas-containing coal sample. Then, control the jack 30 to maintain the jacking and record the corresponding data of the jacking force and the jacking displacement.

[0047] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A measuring device for the shear strength of coal seams under gas seepage and pressure, comprising a shear combination box composed of an upper shear box (15) and a lower shear box (16). The top and bottom of the upper shear box (15) are both open. The upper shear cavity of the upper shear box (15) and the lower shear cavity of the lower shear box (16) form a coal sample combination cavity, characterized in that: It further includes a fixed steel support (4), a gas inlet cylinder (24), a jack (30) and a jack drive controller (23). The upper shear box (15) is fixedly connected to the fixed steel support (4). The jack (30) has a jack telescopic arm (33). A lower shear box push point (32) corresponding to the end of the jack telescopic arm (33) is provided on the outer side wall of the lower shear box (16). The jack drive controller (23) controls the jack (30) to perform a pushing and shearing operation. A porous cushion layer (14) is provided at the top of the upper shear cavity of the upper shear box (15), and a rubber membrane (13) is provided to sealingly cover the top of the porous cushion layer (14). A gas inlet duct (25) communicating with the porous cushion layer (14) is connected to the top of the upper shear box (15). The outlet of the gas inlet cylinder (24) is hermetically connected to the gas inlet duct (25) through a flexible rubber gas pipeline D (22). A gas control ball valve A (35) is provided at the outlet of the gas inlet cylinder (24), and a gas pressure gauge A (36) is also installed on the flexible rubber gas pipeline D (22). It further includes a vacuum pump (5). A lower exhaust steel duct (27) is communicated and provided at the bottom of the lower shear box (16). The inlet of the vacuum pump (5) is hermetically connected to the lower exhaust steel duct (27) through a flexible rubber gas pipeline group. It further includes an axial pressure cavity (10). The axial pressure cavity (10) has an axial pressure chamber. The axial pressure cavity (10) overlaps with the upper shear box (15) vertically, and the bottom of the axial pressure cavity (10) completely wraps and seals the rubber membrane (13) and the porous cushion layer (14).

2. The measuring device for gas seepage and shear strength of coal seam under pressure according to claim 1, characterized in that: It further includes a shear box steel support (21). A steel bottom plate (28) is fixed to the top of the shear box steel support (21). The shear combination box is placed on the steel bottom plate (28). A jack steel support (19) is fixed to the top of the steel bottom plate (28). The jack (30) is detachably fixed to the top of the jack steel support (19). A steel ball auxiliary moving layer is provided between the bottom of the lower shear box (16) and the steel bottom plate (28). The steel ball auxiliary moving layer is composed of a plurality of steel balls (26).

3. The measuring device for gas seepage and shear strength of coal seam under pressure according to claim 2, characterized in that: It further includes a nitrogen supply cylinder (1). An intake steel duct (11) is communicated and provided at the top of the axial pressure cavity (10). The outlet of the nitrogen supply cylinder (1) is hermetically connected to the intake steel duct (11) through a flexible rubber gas pipeline A (2).

4. The measuring device for gas seepage and shear strength of coal seam under pressure according to claim 3, characterized in that: A gas control ball valve B (351) is installed at a position of the flexible rubber gas pipeline A (2) close to the outlet of the nitrogen supply cylinder (1), and a gas pressure gauge B (361) is installed at a position of the flexible rubber gas pipeline A (2) close to the intake steel duct (11).

5. The measuring device for gas seepage and shear strength of coal seam under pressure according to claim 4, characterized in that: A steel top cover (12) is connected to the top of the axial pressure cavity (10). A left tempered glass baffle (7) and a right tempered glass baffle (18) are detachably connected between the steel top cover (12) and the steel bottom plate (28). The left tempered glass baffle (7) and the right tempered glass baffle (18) jointly form a glass baffle assembly, and the glass baffle assembly forms a sealed accommodation cavity.

6. The measuring device for gas seepage and shear strength of coal seam under pressure according to claim 5, characterized in that: The flexible rubber gas transmission pipe group includes a flexible rubber gas transmission pipe B (6), a left exhaust duct (8), and a flexible rubber gas transmission pipe C (9). The left exhaust duct (8) is installed through the left toughened glass baffle (7). The flexible rubber gas transmission pipe B (6) is connected between the vacuum pump (5) and the left exhaust duct (8), and the flexible rubber gas transmission pipe C (9) is connected between the vacuum pump (5) and the lower exhaust steel duct (27). A gas control ball valve C and a gas pressure gauge C are installed on the flexible rubber gas transmission pipe B (6).

7. The measuring device for gas seepage and shear strength of coal seam under pressure according to claim 6, characterized in that: The jack driving controller (23) is connected to the jack (30) through a wire. The wire passes through the right toughened glass baffle (18), and a rubber duct (31) and a steel duct (34) for protecting the wire are provided on the right toughened glass baffle (18).

8. A measurement method using the measurement device according to claim 7, characterized in that, The measurement method includes: A. Measurement of the shear strength of a coal sample under the action of coal seam gas pressure: Make the collected coal sample into a coal sample that fits the coal sample combination cavity. Place the coal sample (17) in the coal sample combination cavity of the shear combination box. Open the gas control ball valve A (35), and input gas into the porous cushion layer (14) through the gas inlet bottle (24). The gas passes through the porous cushion layer (14) to evenly apply pressure to the coal sample. Observe the gas pressure gauge A (36) on the flexible rubber gas transmission pipe D (22) until the gas pressure gauge A (36) shows that the gas pressure reaches the gas pressure set value F1 and remains stable for a time H1. Start the jack driving controller (23), control the jack (30) through the jack driving controller (23) to gradually increase the jacking force and push the lower shear box (16) to perform a shearing motion, and monitor the jacking force data when starting to push and move the coal sample (17). Then control the jack (30) to maintain the jacking and record the corresponding data of the jacking force and the jacking displacement. B. Measurement of the shear strength of a coal sample under the action of coal seam gas pressure and gas seepage: Make the collected coal sample into a coal sample that fits the coal sample combination cavity. Place the coal sample (17) in the coal sample combination cavity of the shear combination box. Open the gas control ball valve A (35), and input gas into the porous cushion layer (14) through the gas inlet bottle (24). The gas passes through the porous cushion layer (14) to evenly apply pressure to the coal sample. At the same time, start the vacuum pump (5) and perform air extraction on the coal sample combination cavity to generate upper and lower gas seepage in the coal sample (17). Observe the gas pressure gauge A (36) on the flexible rubber gas transmission pipe D (22) until the gas pressure gauge A (36) shows that the gas pressure reaches the gas pressure set value F2 and remains stable for a time H2. Start the jack driving controller (23), control the jack (30) through the jack driving controller (23) to gradually increase the jacking force and push the lower shear box (16) to perform a shearing motion, and monitor the jacking force data when starting to push and move the coal sample (17). Then control the jack (30) to maintain the jacking and record the corresponding data of the jacking force and the jacking displacement. C. Measurement of the shear strength of coal samples under the normal pressure of the coal seam: The collected coal samples are made into coal samples that match the coal sample combination cavity. The coal sample (17) is placed in the coal sample combination cavity of the shear combination box. Open the gas control ball valve B (351), and input nitrogen into the axial pressure chamber of the axial pressure cavity (10) through the nitrogen gas supply cylinder (1). The nitrogen gas evenly exerts pressure on the porous cushion layer (14) in the axial pressure chamber and transmits it to the top of the coal sample (17). Observe the gas pressure gauge B (361) until the gas pressure gauge B (361) shows that the nitrogen gas pressure reaches the nitrogen gas pressure set value F3 and remains stable for the holding time H3. Start the jack drive controller (23), and control the jack (30) by the jack drive controller (23) to gradually increase the jacking force and push the lower shear box (16) to perform a shearing movement, and monitor the jacking force data when starting to push and move the coal sample (17). Then control the jack (30) to maintain the jacking and record the corresponding data of the jacking force and the jacking displacement.

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