Coal rock damage and failure characteristic testing device and testing method based on multi-field coupling

Abstract

The present application relates to coal rock damage and destruction characteristic test technical field, provide a kind of coal rock damage and destruction characteristic test device and test method based on multi-field coupling, the test device includes test mechanism, test mechanism includes base, axial pressure loading component and confining pressure loading component;Axial pressure loading component includes first loading plate and second loading plate, the upper surface of first loading plate is connected with the hydraulic assembly for driving first loading plate to move downwards, second loading plate is connected with multiple loading rods, loading rod extends downwards and is connected with pulling assembly after passing through base;Confining pressure loading component includes center cylinder, inner cylinder and outer cylinder nested in order from inside to outside, center cylinder and coal rock sample form center liquid storage cavity for accommodating first confining pressure liquid between, outer peripheral liquid storage cavity for accommodating second confining pressure liquid is formed between inner cylinder and outer cylinder.The present application can test the damage and destruction characteristics of coal rock sample under the conditions of axial impact, circumferential extrusion and temperature change in a short time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coal rock damage and failure characteristics test, in particular to a coal rock damage and failure characteristics test device and test method based on multi-field coupling. BACKGROUND

[0002] The original microstructure of coal rock is complex, and the study of crack propagation law of coal rock under external load can reveal the damage and failure mechanism, thereby preventing disasters in engineering. In the actual environment of coal rock, stress field, temperature field and seepage field have mutual coupling effect on coal rock, making the mechanical behavior research of coal rock, which is a non-homogeneous anisotropic material, very complex.

[0003] In the prior art, the multi-field coupling test of the damage and failure characteristics of coal rock is mainly realized by applying axial load, circumferential confining pressure and controlling temperature to the coal rock sample. During the test, after the multi-field coupling environment is formed, a certain time is maintained, and then the state of the coal rock sample is determined by means of ray scanning, and the damage and failure characteristics of the coal rock sample are determined.

[0004] The main deficiency of the above-mentioned prior art is that the multi-field coupling test environment can only be adjusted smoothly. For example, the axial load is mainly provided by a hydraulic device, and when the axial load needs to be adjusted, the hydraulic device can only be adjusted gradually, so that the axial load received by the coal rock sample is gradually increased or decreased. Similarly, the temperature control unit arranged in the confining pressure liquid also needs to be adjusted gradually. However, in actual engineering scenarios, the load and temperature of coal rock may change in a very short time under the influence of environmental changes. For example, when a water flow channel is formed around the coal rock body, the low-temperature groundwater may directly impact on the coal rock body, causing the temperature of the coal rock body to change rapidly. The existing gradual heating or gradual cooling method cannot test this situation.

[0005] In summary, the existing test device for the damage and failure characteristics of coal rock can test under stable multi-field coupling conditions, but it is difficult to test the instantaneous environmental changes. SUMMARY

[0006] In order to solve the deficiency in the prior art, the present application provides a coal rock damage and failure characteristics test device and test method based on multi-field coupling, which can test the damage and failure characteristics of coal rock samples under conditions such as axial impact, circumferential extrusion and temperature change in a short time. The test results are more abundant, and the damage and failure characteristics of the coal rock sample can be tested more fully.

[0007] In order to achieve the above object, the specific scheme adopted by the present application is: the coal rock damage and failure characteristic test device based on multi-field coupling, comprising a test mechanism and a supporting mechanism for supporting the test mechanism, the test mechanism comprising a base for supporting a coal rock sample, an axial pressure loading assembly for applying an axial load to the coal rock sample, and a confining pressure loading assembly for applying a circumferential load to the coal rock sample;

[0008] The axial pressure loading assembly comprises a first loading plate and a second loading plate arranged in a stack, the upper surface of the first loading plate is connected with a hydraulic assembly for driving the first loading plate to move downward, the second loading plate is connected with a plurality of loading rods, the loading rods extend downward and are fixedly connected with a connecting plate after passing through the base, and the connecting plate is connected with a pulling assembly for pulling the second loading plate to move downward.

[0009] The confining pressure loading assembly comprises a center cylinder, an inner cylinder and an outer cylinder nested in sequence from inside to outside, the center cylinder is located on the peripheral side of the base, and the center cylinder and the coal rock sample form a center liquid storage cavity for accommodating a first confining pressure liquid, the inner cylinder is spaced apart from the center cylinder and the outer cylinder, and the inner cylinder and the outer cylinder form an outer peripheral liquid storage cavity for accommodating a second confining pressure liquid, the temperatures of the first confining pressure liquid and the second confining pressure liquid are different, and a plurality of communication control units are arranged between the center cylinder and the inner cylinder.

[0010] As a further optimization of the above-mentioned coal rock damage and failure characteristic test device based on multi-field coupling, the pulling assembly comprises a plurality of pull rods fixedly connected with the connecting plate, the pull rods extend downward and are fixedly connected with a bearing plate, a tray for supporting a loading block is arranged between the bearing plate and the connecting plate in a lifting manner, and the tray is connected with an elevator for driving the tray to lift through a pull rope.

[0011] As a further optimization of the above-mentioned coal rock damage and failure characteristic test device based on multi-field coupling, the loading block is disc-shaped, a plurality of notches are formed at the edge of the loading block and the edge of the tray, the pull rods correspondingly extend into the notches, and a through hole is formed in the middle of the loading block for the pull rope to pass through.

[0012] As a further optimization of the above-mentioned coal rock damage and failure characteristic test device based on multi-field coupling, the pulling assembly comprises two vertical mounting rods fixedly connected with the supporting mechanism, a horizontal mounting rod is fixedly connected between the two vertical mounting rods, the horizontal mounting rod is rotatably connected with a fixed pulley, the fixed pulley is located above the through hole, and the pull rope passes through the fixed pulley.

[0013] As a further optimization of the above-mentioned coal rock damage and failure characteristic test device based on multi-field coupling: the support mechanism comprises an upper base plate and a lower base plate arranged above and below, the upper base plate is fixedly connected with a top plate, the lower base plate is fixedly connected with a bottom plate, the center cylinder, the inner cylinder and the outer cylinder are located between the top plate and the bottom plate, and the two ends of the center cylinder, the inner cylinder and the outer cylinder are tightly attached to the top plate and the bottom plate to close the center liquid storage cavity and the peripheral liquid storage cavity, and the plunger of the hydraulic assembly is fixedly connected with the first loading plate after penetrating through the upper base plate and the top plate.

[0014] As a further optimization of the above-mentioned coal rock damage and failure characteristic test device based on multi-field coupling: the center liquid storage cavity and the peripheral liquid storage cavity each communicate with a liquid supply assembly, the liquid supply assembly comprises a container for storing the first confining pressure liquid or the second confining pressure liquid, a delivery pump for delivering the first confining pressure liquid into the center liquid storage cavity or for delivering the second confining pressure liquid into the peripheral liquid storage cavity, and a temperature control unit for controlling the temperature of the first confining pressure liquid or the second confining pressure liquid.

[0015] As a further optimization of the above-mentioned coal rock damage and failure characteristic test device based on multi-field coupling: the communication control unit comprises a middle communication pipe made of heat insulation material, each end of the middle communication pipe communicates with an end communication pipe, the end communication pipe is used to communicate with the center cylinder or the inner cylinder, and the middle communication pipe is provided with a valve.

[0016] As a further optimization of the above-mentioned coal rock damage and failure characteristic test device based on multi-field coupling: the two ends of the middle communication pipe are integrally connected with a connecting part, and the outer diameter of the connecting part is smaller than the outer diameter of the middle communication pipe, the end communication pipe is sleeved on the connecting part, and a sealing ring is arranged between the end communication pipe and the middle communication pipe.

[0017] A coal rock damage and failure characteristic test method based on multi-field coupling, based on the above-mentioned coal rock damage and failure characteristic test device based on multi-field coupling, the method comprises the following steps:

[0018] The coal rock sample is arranged on the base;

[0019] The axial load is applied to the coal rock sample by the axial pressure loading assembly, and the circumferential load is applied to the coal rock sample by the confining pressure loading assembly;

[0020] The temperature of the first confining pressure liquid is controlled to reach the target test temperature to heat the coal rock sample.

[0021] As a further optimization of the above-mentioned coal rock damage and failure characteristic test method based on multi-field coupling: the method further comprises the following steps:

[0022] Pull the second loading plate by the pulling assembly, and apply the sudden load to the coal rock sample by the second loading plate;

[0023] Mix the first confining pressure liquid and the second confining pressure liquid by the communication control unit to adjust the temperature of the coal rock sample.

[0024] Beneficial effects: the present application can construct stress field, seepage field and temperature field, realize the test on the damage and destruction characteristics of the coal rock sample in the multi-field coupling environment, and can test the damage and destruction characteristics of the coal rock sample under the conditions of axial impact, circumferential extrusion and temperature change in a short time, the test results are more abundant, and the damage and destruction characteristics of the coal rock sample can be more fully tested. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is the overall structure schematic diagram of the test device of the present application;

[0026] Figure 2 is the structure schematic diagram of the test mechanism;

[0027] Figure 3 is the structure schematic diagram of the pulling unit;

[0028] Figure 4 is the setting mode schematic diagram of the displacement sensor;

[0029] Figure 5 is the structure schematic diagram of the communication control unit.

[0030] BRIEF DESCRIPTION OF DRAWINGS: 1-main support, 2-supporting plate, 3-liquid supply assembly, 4-lower base plate, 5-bottom plate, 6-test mechanism, 7-top plate, 8-upper base plate, 9-hydraulic assembly, 10-connection plate, 11-pulling rod, 12-bearing plate, 13-tray, 14-loading block, 15-pulling rope, 16-pad block, 17-elevator, 18-plunger, 19-pressure sensor, 20-first loading plate, 21-second loading plate, 22-outer cylinder, 23-inner cylinder, 24-outer peripheral liquid storage cavity, 25-communication control unit, 26-loading rod, 27-coal rock sample, 28-center cylinder, 29-center liquid storage cavity, 30-liquid delivery pipe, 31-vertical mounting rod, 32-horizontal mounting rod, 33-through hole, 34-fixed pulley, 35-notch, 36-sleeve ring, 37-displacement sensor, 38-base, 39-end communication pipe, 40-connection part, 41-sealing ring, 42-middle communication pipe, 43-valve. DETAILED DESCRIPTION

[0031] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0032] As shown in Figure 1 and Figure 2 The present application first provides a coal rock damage and failure characteristic test device based on multi-field coupling, which comprises a test mechanism 6 and a support mechanism for supporting the test mechanism 6. The test mechanism 6 comprises a base 38 for supporting a coal rock sample 27, an axial pressure loading assembly for applying an axial load to the coal rock sample 27, and a confining pressure loading assembly for applying a circumferential load to the coal rock sample 27.

[0033] The axial pressure loading assembly comprises a first loading plate 20 and a second loading plate 21 arranged in a stack from top to bottom. The upper surface of the first loading plate 20 is connected with a hydraulic assembly 9 for driving the first loading plate 20 to move downward. The second loading plate 21 is connected with a plurality of loading rods 26. The loading rods 26 extend downward and are fixedly connected with a connecting plate 10 after passing through the base 38. The connecting plate 10 is connected with a pulling assembly for pulling the second loading plate 21 to move downward.

[0034] The confining pressure loading assembly comprises a center cylinder 28, an inner cylinder 23 and an outer cylinder 22 nested in sequence from inside to outside. The center cylinder 28 is located on the peripheral side of the base 38, and a center liquid storage cavity 29 for accommodating a first confining pressure liquid is formed between the center cylinder 28 and the coal rock sample 27. The inner cylinder 23 is spaced apart from the center cylinder 28 and the outer cylinder 22, and an outer peripheral liquid storage cavity 24 for accommodating a second confining pressure liquid is formed between the inner cylinder 23 and the outer cylinder 22. The temperatures of the first confining pressure liquid and the second confining pressure liquid are different. A plurality of communication control units 25 are arranged between the center cylinder 28 and the inner cylinder 23.

[0035] In the damage and failure characteristic test of the coal rock sample 27 by using the present application, first, the coal rock sample 27 is placed on the base 38, and then the first loading plate 20 is pushed down by the hydraulic assembly 9, the second loading plate 21 and the coal rock sample 27 are extruded downward by the first loading plate 20, so as to apply an axial load to the coal rock sample 27, that is, to form a stress field; at the same time, the first confining pressure liquid is introduced into the central liquid storage cavity 29, and the first confining pressure liquid is used to apply a circumferential confining pressure to the coal rock sample 27, that is, to form a seepage field; on the other hand, by controlling the temperature of the first confining pressure liquid, the temperature of the coal rock sample 27 can be controlled, that is, to form a temperature field. The stress field, the seepage field and the temperature field are coupled with each other to form a multi-field coupling test environment, and the coal rock sample 27 is tested for damage and failure characteristics. After a period of time, the damage results of the coal rock sample 27 can be obtained by means of ray scanning, including crack distribution and crack width data, and the specific ray scanning method is a conventional technology in the art, which will not be described here. In the process, the temperature of the second confining pressure liquid in the peripheral liquid storage cavity 24 can be controlled to be substantially lower than the temperature of the first confining pressure liquid.

[0036] Further, after the test duration reaches the preset duration threshold, the second loading plate 21 is pulled down by the pulling assembly, and the second loading plate 21 is used to apply an axial sudden load to the coal rock sample 27 to change the stress field, so that the axial load on the coal rock sample 27 is greatly increased in a short time, thereby testing the damage and failure characteristics of the coal rock sample 27 when subjected to instantaneous axial impact. On the other hand, by controlling the communication control unit 25 to communicate the central liquid storage cavity 29 and the peripheral liquid storage cavity 24, the second confining pressure liquid flows into the central liquid storage cavity 29 through part of the communication control unit 25, and part of the first confining pressure liquid enters the peripheral liquid storage cavity 24 through another part of the communication control unit 25, thereby realizing the exchange of the first confining pressure liquid and the second confining pressure liquid, and the second confining pressure liquid entering the central liquid storage cavity 29 can quickly reduce the temperature of the coal rock sample 27, thereby testing the damage and failure characteristics of the coal rock sample 27 when the temperature changes rapidly. By using multiple communication control units 25, the first confining pressure liquid and the second confining pressure liquid can be quickly exchanged, thereby quickly reducing the temperature of the coal rock sample 27, and ensuring the accuracy of the test results. In addition, in the above-mentioned basic test environment of multi-field coupling, the temperature of the second confining pressure liquid can also be made the same as that of the first confining pressure liquid, and then the second confining pressure liquid can flow to the first confining pressure liquid through the multiple communication control units 25 to pressurize the first confining pressure liquid, thereby quickly increasing the confining pressure, and testing the damage and failure characteristics of the coal rock sample 27 when subjected to instantaneous circumferential extrusion.

[0037] The present application can construct stress field, seepage field and temperature field, realize the damage and destruction characteristics test of the coal rock sample 27 in the multi-field coupling environment, and the present application can test the damage and destruction characteristics of the coal rock sample 27 under the conditions of axial impact, circumferential extrusion and temperature change in a short time, the test results are more abundant, and the damage and destruction characteristics of the coal rock sample 27 can be more fully tested.

[0038] The specific structure of the pulling assembly is that the pulling assembly comprises a plurality of pulling rods 11 fixedly connected with the connecting plate 10, the pulling rods 11 extend downward and are jointly fixedly connected with a bearing plate 12, a tray 13 for supporting loading blocks 14 is arranged in a lifting mode between the bearing plate 12 and the connecting plate 10, and the tray 13 is connected with a hoist 17 for driving the tray 13 to lift through a pull rope 15. After the test starts, a plurality of loading blocks 14 are arranged on the tray 13, and the tray 13 and the loading blocks 14 are pulled upward by the hoist 17 and the pull rope 15, so that the bearing plate 12 is not stressed. When it is needed to apply instantaneous axial impact to the coal rock sample 27, the tray 13 and the loading blocks 14 are released, and then the tray 13 and the loading blocks 14 fall downward under the action of gravity, and when the tray 13 and the loading blocks 14 fall onto the bearing plate 12, the bearing plate 12 can be impacted, and then the second loading plate 21 is pulled through the pulling rod 11, the connecting plate 10 and the loading rod 26, and the impact energy is transmitted to the coal rock sample 27 through the second loading plate 21, so that the coal rock sample 27 is subjected to instantaneous axial impact. Based on the pulling assembly, compared with the conventional way of gradually adjusting the hydraulic assembly 9 to increase the axial load, the present application can apply instantaneous axial impact to the coal rock sample 27, and by adjusting the number of loading blocks 14, the size of the impact force can also be flexibly changed.

[0039] As shown in Figure 3 Further, the loading block 14 is disc-shaped, a plurality of notches 35 are arranged at the edge of the loading block 14 and the edge of the tray 13, the pulling rod 11 corresponds to extend into the notch 35, and a through hole 33 for the pull rope 15 to pass through is arranged at the middle part of the loading block 14. Through the cooperation of the notch 35 and the pulling rod 11, the moving direction of the tray 13 and the loading block 14 can be limited, the loading block 14 is prevented from deviating laterally, and it is ensured that the loading block 14 can impact the bearing plate 12 smoothly. By arranging the through hole 33, it is ensured that the hoist 17 can pull the tray 13 and the loading block 14 upward through the pull rope 15.

[0040] In order to control the direction of the pull rope 15, avoid the pull rope 15 from being damaged by frequent contact and friction with the loading block 14, and ensure that the tray 13 and the loading block 14 can be stably pulled up, the pulling assembly comprises two vertical installation rods 31 fixedly connected with the support mechanism, a horizontal installation rod 32 fixedly connected between the two vertical installation rods 31, a fixed pulley 34 rotationally connected with the horizontal installation rod 32, and the fixed pulley 34 is located above the through hole 33, and the pull rope 15 passes through the fixed pulley 34.

[0041] The supply mode of the first confining pressure liquid and the second confining pressure liquid is that the central liquid storage cavity 29 and the peripheral liquid storage cavity 24 are respectively connected with a liquid supply assembly 3, the liquid supply assembly comprises a container for storing the first confining pressure liquid or the second confining pressure liquid, a delivery pump for delivering the first confining pressure liquid into the central liquid storage cavity 29 or for delivering the second confining pressure liquid into the peripheral liquid storage cavity 24, and a temperature control unit for controlling the temperature of the first confining pressure liquid or the second confining pressure liquid. The temperature control unit can comprise an electric heating wire for heating the first confining pressure liquid or the second confining pressure liquid and a refrigerator for cooling the first confining pressure liquid or the second confining pressure liquid, which is mature prior art and will not be described here.

[0042] The specific structure of the support mechanism is that the support mechanism comprises an upper base plate 8 and a lower base plate 4 arranged in a top-bottom manner, the upper base plate 8 is fixedly connected with a top plate 7, the lower base plate 4 is fixedly connected with a bottom plate 5, the central cylinder 28, the inner cylinder 23 and the outer cylinder 22 are located between the top plate 7 and the bottom plate 5, and the two ends of the central cylinder 28, the inner cylinder 23 and the outer cylinder 22 are tightly attached to the top plate 7 and the bottom plate 5 to close the central liquid storage cavity 29 and the peripheral liquid storage cavity 24, and the plunger 18 of the hydraulic assembly 9 is fixedly connected with the first loading plate 20 after passing through the upper base plate 8 and the top plate 7 downward.

[0043] Further, the support mechanism comprises a main support 1, the main support 1 comprises a plurality of support columns for supporting the lower base plate 4 and at least two support plates 2, and the support plates 2 are fixedly connected between two adjacent support columns, the hoist 17 for pulling the tray 13 and the loading block 14 is arranged on one support plate 2 through the pad 16, and the other support plate 2 is provided with two liquid supply assemblies 3, and the two liquid supply assemblies 3 are respectively used for introducing the first confining pressure liquid into the central liquid storage cavity 29 and for introducing the second confining pressure liquid into the peripheral liquid storage cavity 24. In addition, the central liquid storage cavity 29 and the peripheral liquid storage cavity 24 are respectively connected with two liquid delivery pipes 30, and the liquid delivery pipes 30 are used for cooperating with the liquid supply assemblies 3 to deliver the first confining pressure liquid or the second confining pressure liquid.

[0044] As Figure 5As shown, the specific structure of the communication control unit 25 is that the communication control unit 25 comprises a middle communication pipe 42 made of heat insulation material, one end part communication pipe 39 for communicating the central cylinder 28 or the inner cylinder 23 is communicated at each end of the middle communication pipe 42, and the valve 43 is arranged on the middle communication pipe 42. By controlling the valve 43, the communication or separation of the central cylinder 28 and the inner cylinder 23 can be controlled. By arranging the middle communication pipe 42 made of heat insulation material, the excessive heat exchange of the first confining pressure liquid and the second confining pressure liquid through the communication control unit 25 can be avoided, so that the temperature stability of the first confining pressure liquid and the second confining pressure liquid is ensured.

[0045] The specific connection mode of the middle communication pipe 42 and the end part communication pipe 39 is that the connection part 40 is integrally connected at each end of the middle communication pipe 42, and the outer diameter of the connection part 40 is smaller than the outer diameter of the middle communication pipe 42, the end part communication pipe 39 is sleeved on the connection part 40, and the sealing ring 41 is arranged between the end part communication pipe 39 and the middle communication pipe 42.

[0046] As shown in the figure, Figure 4 In order to monitor the radial displacement of the coal rock sample 27 during the test process, the state of the coal rock sample 27 can be monitored in real time, the loading rod 26 is fixedly sleeved with a sleeve ring 36, the sleeve ring 36 is fixedly connected with a displacement sensor 37 extending to the coal rock sample 27, the input end of the displacement sensor 37 can be fixed on the coal rock sample 27, when the coal rock sample 27 produces radial displacement, the displacement sensor 37 can be driven to act, so that the radial displacement of the coal rock sample 27 is monitored. By means of the loading rod 26, the displacement sensor 37 can be installed without increasing additional installation structure, and the complexity of the structure is reduced. On the other hand, the pressure sensor 19 can be arranged between the plunger 18 of the hydraulic assembly 9 and the first loading plate 20, so as to monitor the axial load applied by the hydraulic assembly 9 to the coal rock sample 27. It should be noted that the pressure sensor 19 and the displacement sensor 37 are both conventional technologies in the field, which will not be described here.

[0047] The application further provides a coal rock damage and destruction characteristic test method based on multi-field coupling, which is based on the coal rock damage and destruction characteristic test device based on multi-field coupling.

[0048] S1, the coal rock sample 27 is arranged on the base 38.

[0049] S2, the axial load is applied to the coal rock sample 27 by the axial pressure loading assembly, and the circumferential load is applied to the coal rock sample 27 by the confining pressure loading assembly. During the process of applying the axial load, the axial load can be monitored by the pressure sensor 19 to ensure the control accuracy of the axial load. Similarly, the pressure sensor can be arranged in the central liquid storage cavity 29 and the peripheral liquid storage cavity 24 to monitor the confining pressure and realize the accurate control of the circumferential load.

[0050] S3, control the temperature of the first confining fluid to reach the target test temperature to heat the coal rock sample 27. Temperature sensors can be provided in the central liquid storage cavity 29 and the peripheral liquid storage cavity 24 to monitor the temperature of the first confining fluid and the second confining fluid.

[0051] S4, use the pulling assembly to pull the second loading plate 21 to apply a sudden load to the coal rock sample 27 by the second loading plate 21. Specifically, a plurality of loading blocks 14 are arranged on the tray 13, and the tray 13 and the loading blocks 14 are lifted upward by the cooperation of the lifting machine 17 and the pulling rope 15. When the sudden load needs to be applied, the lifting machine 17 is loosened, so that the tray 13 and the loading blocks 14 fall under the action of gravity and impact the bearing plate 12.

[0052] S5, use the communication control unit 25 to control the mixing of the first confining fluid and the second confining fluid to adjust the temperature of the coal rock sample 27. According to the adjustment range of the temperature, a part of the communication control units 25 can be selected to be opened. These opened communication control units 25 can be divided into two groups. The first group is used to transport the second confining fluid into the central liquid storage cavity 29 to mix with the first confining fluid, and the second group is used to transport the first confining fluid into the peripheral liquid storage cavity 24.

[0053] The above description of disclosed embodiments enables those skilled in the art to carry out or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A coal rock damage and failure characteristic testing device based on multi-field coupling, characterized in that, The test mechanism (6) and the support mechanism for supporting the test mechanism (6), the test mechanism (6) includes a base (38) for supporting a coal rock sample (27), an axial pressure loading assembly for applying an axial load to the coal rock sample (27), and a confining pressure loading assembly for applying a circumferential load to the coal rock sample (27); The axial pressure loading assembly includes a first loading plate (20) and a second loading plate (21) arranged in a stack, the upper surface of the first loading plate (20) is connected with a hydraulic assembly (9) for driving the first loading plate (20) to move downward, the second loading plate (21) is connected with a plurality of loading rods (26), the loading rods (26) extend downward and are fixedly connected with a connecting plate (10) after penetrating through the base (38), and the connecting plate (10) is connected with a pulling assembly for pulling the second loading plate (21) to move downward; The pulling assembly includes a plurality of pull rods (11) fixedly connected with the connecting plate (10), the pull rods (11) extend downward and are fixedly connected with a bearing plate (12), a tray (13) for supporting a loading block (14) is arranged between the bearing plate (12) and the connecting plate (10) in a lifting manner, and the tray (13) is connected with a hoist (17) for driving the tray (13) to lift through a pull rope (15); The confining pressure loading assembly includes a center cylinder (28), an inner cylinder (23) and an outer cylinder (22) nested in sequence from inside to outside, the center cylinder (28) is located on the periphery of the base (38), and a center liquid storage cavity (29) for accommodating a first confining pressure liquid is formed between the center cylinder (28) and the coal rock sample (27), the inner cylinder (23) is spaced apart from the center cylinder (28) and the outer cylinder (22), and an outer peripheral liquid storage cavity (24) for accommodating a second confining pressure liquid is formed between the inner cylinder (23) and the outer cylinder (22), the temperatures of the first confining pressure liquid and the second confining pressure liquid are different, and a plurality of communication control units (25) are arranged between the center cylinder (28) and the inner cylinder (23); The communication control unit (25) includes a middle communication pipe (42) made of a heat insulation material, each end of the middle communication pipe (42) is connected with an end communication pipe (39) for communicating with the center cylinder (28) or the inner cylinder (23), and a valve (43) is arranged on the middle communication pipe (42).

2. The multi-field coupling based coal rock damage and failure characteristics testing device according to claim 1, wherein The loading block (14) is disc-shaped, a plurality of notches (35) are formed at the edge of the loading block (14) and the edge of the tray (13), the pull rods (11) correspondingly extend into the notches (35), and a through hole (33) is formed in the middle of the loading block (14) for the pull rope (15) to pass through.

3. The multi-field coupling based coal rock damage and failure characteristics testing device according to claim 2, characterized in that, The pulling assembly includes two vertical mounting rods (31) fixedly connected with the support mechanism, a horizontal mounting rod (32) is fixedly connected between the two vertical mounting rods (31), a fixed pulley (34) is rotatably connected with the horizontal mounting rod (32), the fixed pulley (34) is located above the through hole (33), and the pull rope (15) passes around the fixed pulley (34).

4. The multi-field coupling based coal rock damage and failure characteristics testing device according to claim 1, characterized in that, The support mechanism comprises an upper base plate (8) and a lower base plate (4) arranged in a top-bottom manner, the upper base plate (8) is fixedly connected with a top plate (7), the lower base plate (4) is fixedly connected with a bottom plate (5), the center cylinder (28), the inner cylinder (23) and the outer cylinder (22) are located between the top plate (7) and the bottom plate (5), and the two ends of the center cylinder (28), the inner cylinder (23) and the outer cylinder (22) are tightly attached to the top plate (7) and the bottom plate (5) to close the center liquid storage cavity (29) and the peripheral liquid storage cavity (24), and the plunger (18) of the hydraulic assembly (9) is fixedly connected with the first loading plate (20) after penetrating downward through the upper base plate (8) and the top plate (7).

5. The multi-field coupling based coal rock damage and failure characteristics testing device according to claim 1, wherein The center liquid storage cavity (29) and the peripheral liquid storage cavity (24) are each communicated with a liquid supply assembly (3), the liquid supply assembly comprises a container for storing the first confining pressure liquid or the second confining pressure liquid, a delivery pump for delivering the first confining pressure liquid into the center liquid storage cavity (29) or for delivering the second confining pressure liquid into the peripheral liquid storage cavity (24), and a temperature control unit for controlling the temperature of the first confining pressure liquid or the second confining pressure liquid.

6. The multi-field coupling based coal rock damage and failure characteristics testing device according to claim 1, wherein Both ends of the middle communication pipe (42) are integrally connected with a connecting portion (40), and the outer diameter of the connecting portion (40) is smaller than the outer diameter of the middle communication pipe (42), the end communication pipe (39) is sleeved on the connecting portion (40), and a sealing ring (41) is arranged between the end communication pipe (39) and the middle communication pipe (42).

7. The coal rock damage and failure characteristic test method based on multi-field coupling, based on the coal rock damage and failure characteristic test device based on multi-field coupling according to any one of claims 1-6, characterized in that, The method comprises the following steps: The coal rock sample (27) is arranged on the base (38); The axial load is applied to the coal rock sample (27) by using the axial load loading assembly, and the circumferential load is applied to the coal rock sample (27) by using the confining pressure loading assembly; The temperature of the first confining pressure liquid is controlled to reach the target test temperature to heat the coal rock sample (27).

8. The coal rock damage and failure characteristics test method based on multi-field coupling according to claim 7, characterized in that, The method further comprises the following steps: The second loading plate (21) is pulled by using the pulling assembly, and the sudden load is applied to the coal rock sample (27) by using the second loading plate (21); The first confining pressure liquid and the second confining pressure liquid are mixed by using the communication control unit (25) to adjust the temperature of the coal rock sample (27).

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