Uniaxial to conventional triaxial compression conversion test device and use method thereof

Abstract

The invention discloses a uniaxial to conventional triaxial compression conversion test device and a use method thereof, and belongs to the field of mechanical devices. The device comprises a lower pressure head, a confining pressure providing mechanism and an upper pressure head, the lower pressing head is placed on a bottom pressing head of the uniaxial compression testing machine; a sample is placed on the lower pressing head; the confining pressure providing mechanism is provided with a placing cavity and is arranged on the lower pressing head, and the sample is positioned in the placing cavity; the first axial cross section of the sample is similar to the second axial cross section of the placing cavity, and the area of the first axial cross section is equal to that of the second axial cross section; the upper pressure head is arranged at the upper part of the confining pressure providing mechanism and below a top pressure head of the uniaxial compression testing machine, and when the upper pressure head extends into the placing cavity under the pressurization of the top pressure head and presses the sample downwards, the confining pressure providing mechanism can provide reverse constraining force for the side surface of the sample. The uniaxial compression testing machine is simple in structure, easy to machine and manufacture, low in manufacturing cost, high in universality, good in compatibility and suitable for application and popularization.

Description

Technical Field

[0001] The present application relates to the technical field of mechanical devices, and in particular to a uniaxial to conventional triaxial compression conversion test device and a method for using the same. Background Art

[0002] Coal rock is not only subjected to vertical stress underground, but also to lateral stress from the surrounding rock mass. Existing uniaxial loading only applies axial pressure in a single direction to the coal rock mass, and can only simulate the stress of the sample under a single stress state. Under this loading method, the sample is mainly subjected to axial compression, while the stress effects in other directions are ignored.

[0003] Since it is difficult to carry out conventional triaxial loading experimental research on coal rock mass with a uniaxial compression testing machine, in order to more realistically simulate the stress state of coal rock mass in a complex underground stress environment, axial and lateral pressures are applied to the coal rock mass at the same time to simulate the multi-directional stress state, which can more accurately reveal the evolution law of coal rock mass cracks.

[0004] In order to achieve a uniaxial loading method that can more comprehensively reflect the mechanical behavior of coal rock in a three-dimensional stress environment, the conversion of the uniaxial compression testing machine into a conventional triaxial testing machine requires an overall modification and design of the equipment. In theory, the transformation of the uniaxial compressor into a device capable of performing triaxial compression requires major adjustments to its structure, including adding an additional pressure application system, modifying the pressure control system, adding sensors and monitoring equipment, and redesigning the specimen installation and fixing system. However, such transformation technology is difficult and costly. Summary of the invention

[0005] The embodiments of the present application provide a uniaxial to conventional triaxial compression conversion test device and a method of using the same, thereby solving the problem that converting an existing uniaxial compression testing machine into a conventional triaxial testing machine requires overall modification and design of the equipment, and the modification technology is difficult and costly.

[0006] In order to achieve the above object, the technical solution of the embodiment of the present invention is:

[0007] In a first aspect, an embodiment of the present invention provides a uniaxial to conventional triaxial compression conversion test device, characterized in that it includes a lower pressure head, a confining pressure providing mechanism and an upper pressure head;

[0008] The lower pressure head is placed on the bottom pressure head of the uniaxial compression testing machine;

[0009] The sample is placed on the lower pressure head;

[0010] The confining pressure providing mechanism is provided with a placement cavity, which is arranged on the lower pressure head and allows the sample to be located in the placement cavity;

[0011] The first axial cross section of the sample is similar to the second axial cross section of the placement cavity, and the area of ​​the first axial cross section is equal to the area of ​​the second axial cross section;

[0012] The upper pressure head is arranged on the upper part of the confining pressure providing mechanism and below the top pressure head of the uniaxial compression testing machine. When the upper pressure head extends into the placement cavity and presses down the sample under the pressure of the top pressure head, the confining pressure providing mechanism can provide reverse restraint force to the side of the sample.

[0013] In combination with the first aspect, in a possible implementation manner, the confining pressure providing mechanism includes a side plate and a fixing hoop;

[0014] The side panels include a plurality of pieces, and the plurality of side panels surround a columnar body having the placement cavity;

[0015] The fixing hoop comprises at least one, and the at least one fixing hoop is sleeved and fixed on the columnar body.

[0016] In combination with the first aspect, in a possible implementation manner, the side panels include four pieces;

[0017] The four side panels form a prism;

[0018] The two side panels arranged opposite to each other have the same shape;

[0019] Both sides of the opposite surfaces of the first group of side panels are respectively provided with embedded grooves recessed from the inside to the outside;

[0020] The two ends of the second group of side panels respectively abut against the embedding grooves at corresponding positions.

[0021] In combination with the first aspect, in a possible implementation manner, the fixing hoops include two;

[0022] The upper and lower ends of both sides of the first group of side plates are provided with mounting grooves recessed inward from the end surfaces;

[0023] A fixing hoop is arranged at the location of a mounting groove.

[0024] In combination with the first aspect, in a possible implementation manner, the fixing hoop includes a fixing strip and a fixing member;

[0025] There are four fixing bars;

[0026] The two fixing bars are arranged opposite to each other, and the two sides of the opposite surfaces thereof are provided with fixing grooves recessed from the inside to the outside;

[0027] The other two fixing bars are arranged in parallel, and both ends are respectively inserted into the fixing grooves at corresponding positions and fixed by the fixing parts.

[0028] In combination with the first aspect, in a possible implementation manner, a plurality of acoustic emission probe mounting holes are provided on the side plate, and the acoustic emission probe mounting holes are configured to install acoustic emission probes.

[0029] In combination with the first aspect, in a possible implementation manner, the acoustic emission probe mounting holes include four;

[0030] Two acoustic emission probe mounting holes are respectively arranged on each of the side panels that are arranged opposite to each other, and the two acoustic emission probe mounting holes are located at the diagonal positions of the side panels.

[0031] In combination with the first aspect, in a possible implementation manner, a ring groove is provided on the top surface of the pressing head.

[0032] In combination with the first aspect, in a possible implementation manner, the pressing head is provided with a first mounting hole recessed from bottom to top;

[0033] And / or, the upper pressure head is provided with a second mounting hole recessed from top to bottom.

[0034] In a second aspect, an embodiment of the present invention provides a method for using a uniaxial to conventional triaxial compression conversion test device, based on the above-mentioned uniaxial to conventional triaxial compression conversion test device, comprising:

[0035] Place the lower pressure head on the bottom pressure head of the uniaxial compression testing machine;

[0036] placing the sample on the lower pressure head;

[0037] The confining pressure providing mechanism is arranged on the lower pressure head and the sample is located in the placement cavity of the confining pressure providing mechanism;

[0038] The upper pressure head is arranged on the upper part of the confining pressure providing mechanism and below the top pressure head of the uniaxial compression testing machine;

[0039] The upper pressure head extends into the placement cavity under the pressure of the top pressure head and presses down the sample to perform the test.

[0040] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0041] The uniaxial to conventional triaxial compression conversion test device provided by the embodiment of the present invention, when actually simulating the stress state test of coal rock mass in a complex underground stress environment, firstly places the lower pressure head on the bottom pressure head of the uniaxial compression testing machine. Then place the sample on the lower pressure head. Then the confining pressure providing mechanism is arranged on the lower pressure head and the sample is located in the placement cavity of the confining pressure providing mechanism. Finally, the upper pressure head is arranged on the upper part of the confining pressure providing mechanism, below the top pressure head of the uniaxial compression testing machine. Under the pressure of the top pressure head, the upper pressure head extends into the placement cavity and presses down the sample for testing. The confining pressure providing mechanism firmly fixes the sample on the lower pressure head and constrains the sample on all sides. Since the first axial section of the sample is similar to the second axial section of the placement cavity, and the area of ​​the first axial section is equal to the area of ​​the second axial section, the sample is in close contact with the confining pressure providing mechanism. Axial pressure is applied to the top pressure head by hydraulic or mechanical means. In the process of applying axial pressure to the sample by the top pressure head and the upper pressure head, due to the rigid constraint of the confining pressure providing mechanism, the sample is subjected to the reverse constraint force from the confining pressure providing mechanism. The reverse constraint stress forms a uniform confining pressure around the sample, which can simulate the effect of the sample confining pressure environment and simulate the stress state of underground rock or soil in a real environment. By measuring the reverse constraint force, the lateral force of the sample can be obtained, and the conventional triaxial compression of the sample can be achieved, thereby realizing the conversion of the uniaxial compression test machine to the triaxial compression test. Compared with the conventional triaxial test machine that only provides lateral forces in several directions, since the reverse constraint force provided by the confining pressure providing mechanism to the sample surrounds the entire outer wall of the sample, the entire outer wall of the sample is uniformly stressed everywhere, which can accurately simulate the stress state of underground rock or soil in a real environment. The test device of the embodiment of the present application is suitable for a uniaxial compression test machine, does not have a complex mechanical structure, has a simple structure, is easy to process and manufacture, has a reasonable design, is easy to operate, has strong practicality, good effect, low production cost, high versatility, good compatibility, and is suitable for promotion and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0043] Figure 1 Schematic diagram of the structure of the uniaxial to conventional triaxial compression conversion test device provided in the embodiment of the present application Figure 1 ;

[0044] Figure 2 Schematic diagram of the structure of the uniaxial to conventional triaxial compression conversion test device provided in the embodiment of the present application Figure 2 ;

[0045] Figure 3 A top view of the pressure head provided in the embodiment of the present application;

[0046] Figure 4 A front view of the pressure head provided in the embodiment of the present application;

[0047] Figure 5 A top view of the upper pressure head provided in an embodiment of the present application;

[0048] Figure 6 A front view of the upper pressure head provided in an embodiment of the present application;

[0049] Figure 7 A top view of a side panel provided in an embodiment of the present application;

[0050] Figure 8 for Figure 7 A front view of a side panel;

[0051] Fig. 9 A front view of another side panel provided in an embodiment of the present application;

[0052] Fig.10 A front view of another side panel provided in an embodiment of the present application;

[0053] Fig.11 A top view of a fixing hoop provided in an embodiment of the present application;

[0054] Fig.12 A top view of a fixing bar provided in an embodiment of the present application;

[0055] Fig.13 for Fig.12 The left view of the fixed bar;

[0056] Fig.14 A top view of another fixing strip provided in an embodiment of the present application.

[0057] Icons: 1-lower pressure head; 11-first mounting hole; 12-first threaded hole; 13-ring groove; 2-confining pressure providing mechanism; 21-side panel; 211-embedded groove; 212-mounting groove; 213-mounting hole for acoustic emission probe; 214-reserved hole for pressure sensor; 215-placement through hole; 22-fixing hoop; 221-fixing strip; 222-fixing groove; 223-first screw hole; 224-second screw hole; 3-upper pressure head; 31-second mounting hole; 32-second threaded hole; 4-bottom pressure head; 5-top pressure head; 6-storage mechanism. DETAILED DESCRIPTION

[0058] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0059] In the description of the embodiments of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limitations on the present invention. The terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance. In addition, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present invention can be understood according to the specific circumstances.

[0060] Please refer to Figures 1-2 As shown, an embodiment of the present invention provides a uniaxial to conventional triaxial compression conversion test device, including a lower pressure head 1, a confining pressure providing mechanism 2 and an upper pressure head 3.

[0061] The lower pressure head 1 is placed on the bottom pressure head 4 of the uniaxial compression testing machine. The sample is placed on the lower pressure head 1. The confining pressure providing mechanism 2 is provided with a placement cavity (the side wall thickness of the confining pressure providing mechanism 2 is uniform), which is arranged on the lower pressure head 1 and allows the sample to be located in the placement cavity. The first axial section of the sample is similar to the second axial section of the placement cavity, and the area of ​​the first axial section is equal to the area of ​​the second axial section.

[0062] For example, the first axial cross-section of the sample in the embodiment of the present application is a rectangle, and the second axial cross-section of the placement cavity is also a rectangle.

[0063] The upper pressure head 3 is arranged on the upper part of the confining pressure providing mechanism 2 (the axial cross-sectional shape and area of ​​the upper pressure head 3 are generally consistent with the second axial cross-sectional shape of the placement cavity), below the top pressure head 5 of the uniaxial compression testing machine. When the upper pressure head 3 extends into the placement cavity and presses down the sample under the pressure of the top pressure head 5, the confining pressure providing mechanism 2 can provide a reverse restraining force to the side of the sample, and the reverse restraining force is the confining pressure provided to the sample by the confining pressure providing mechanism 2. By measuring the reverse restraining force, the magnitude of the side force of the sample can be obtained. Specifically, a pressure sensor reserved hole 214 is provided on the side wall of the confining pressure providing mechanism 2. A thin-film pressure sensor is attached to the sample, and then the transmission line of the pressure sensor is passed through the pressure sensor reserved hole 214 and connected to the storage mechanism 6 (such as a computer), so that the pressure on the side of the sample can be monitored, collected and measured data can be stored.

[0064] The uniaxial to conventional triaxial compression conversion test device provided in an embodiment of the present invention, when actually simulating the stress state test of coal rock mass in a complex underground stress environment, firstly places the lower pressure head 1 on the bottom pressure head 4 of the uniaxial compression test machine. Then the sample is placed on the lower pressure head 1. Then the confining pressure providing mechanism 2 is arranged on the lower pressure head 1 and the sample is located in the placement cavity of the confining pressure providing mechanism 2. Finally, the upper pressure head 3 is arranged on the upper part of the confining pressure providing mechanism 2, below the top pressure head 5 of the uniaxial compression test machine. Under the pressure of the top pressure head 5, the upper pressure head 3 extends into the placement cavity and presses down the sample for testing. The confining pressure providing mechanism 2 firmly fixes the sample on the lower pressure head 1 and constrains the sample on all sides. Since the first axial section of the sample is similar to the second axial section of the placement cavity, and the area of ​​the first axial section is equal to the area of ​​the second axial section, the sample is in close contact with the confining pressure providing mechanism 2. Axial pressure is applied to the top pressure head 5 by hydraulic or mechanical means. In the process of the top pressure head 5 pressurizing the upper pressure head 3 to apply axial pressure to the sample, due to the rigid constraint of the confining pressure providing mechanism 2, the sample is subjected to a reverse constraint force from the confining pressure providing mechanism 2. The reverse constraint stress forms a uniform confining pressure around the sample, which can simulate the effect of the sample confining pressure environment and simulate the stress state of underground rock or soil in a real environment. By measuring the reverse constraint force, the lateral force of the sample can be obtained, and the conventional triaxial compression of the sample can be achieved, thereby realizing the conversion of the uniaxial compression tester to the triaxial compression test. Compared with conventional triaxial testing machines that only provide lateral forces in several directions, the reverse constraint force provided by the confining pressure providing mechanism 2 to the sample surrounds the entire outer wall of the sample, so that every part of the entire outer wall of the sample is uniformly stressed, which can accurately simulate the stress state of underground rock or soil in a real environment. The test device of the embodiment of the present application is suitable for a uniaxial compression testing machine. It does not have a complex mechanical structure, has a simple structure, is easy to process and manufacture, has a reasonable design, is easy to operate, has strong practicality, has a good effect, has a low manufacturing cost, is highly versatile, has good compatibility, and is suitable for popularization and use.

[0065] Optionally, the confining pressure providing mechanism 2 includes a side plate 21 and a fixing hoop 22. The side plate 21 includes multiple pieces, and the multiple side plates 21 surround a columnar body with a placement cavity. The fixing hoop 22 includes at least one, and at least one fixing hoop 22 is sleeved on the columnar body.

[0066] The test device provided in the embodiment of the present application, since the first axial section of the sample is similar to the second axial section of the placement cavity, and the area of ​​the first axial section is equal to the area of ​​the second axial section, a columnar body with a placement cavity is surrounded by multiple side panels 21, so that during actual installation, the sample can be first placed on the lower pressure head 1, and then the multiple side panels 21 can be installed to conveniently and quickly place the sample in the placement cavity of the confining pressure providing mechanism 2. The provision of at least one fixing hoop 22 can firmly fix the columnar body surrounded by multiple side panels 21. The test device is assembled by simple side panels 21 and fixing hoop 22, without complex mechanical structures or parts, and has a simple structure. When the upper pressure head 3 applies axial pressure, the sample is compressed and tries to expand laterally. However, due to the rigid constraint of the side panel 21 and the clamping effect of the fixing hoop 22, the sample cannot expand freely, so that reverse constraint stress, i.e., confining pressure, is generated around the sample.

[0067] Optionally, the side panels 21 include four. The four side panels 21 form a prism. Figures 3 to 6 As shown, the cross-sectional areas of the upper pressure head 3 and the lower pressure head 1 correspond to quadrilaterals. The two side plates 21 arranged opposite to each other have the same shape. Figure 7 As shown, two sides of the opposite surfaces of the first set of side plates 21 are respectively provided with embedded grooves 211 recessed from the inside to the outside. Both ends of the second set of side plates 21 are respectively against the embedded grooves 211 at corresponding positions.

[0068] During the actual installation, the first set of side panels 21 can be first arranged parallel to the two sides of the lower pressure head 1, and then the second set of side panels 21 can be arranged on the other two sides of the lower pressure head 1, and the two ends of the second set of side panels 21 can be respectively against the embedding grooves 211 at the corresponding positions of the first set of side panels 21. The embedding grooves 211 can play a role in positioning the first set of side panels 21 and the second set of side panels 21 during installation, and the installation is quick and convenient. At the same time, due to the determined position, it can be ensured that the end faces of the first set of side panels 21 and the surfaces of the second set of side panels 21 of the enclosed column are in the same plane, which is convenient for subsequent clamping. In addition, it can prevent the second set of side panels 21 from sliding along the surface of the first set of side panels 21.

[0069] Optional, such as Figure 2 As shown, the four side panels 21 are all provided with reserved holes 214 for pressure sensors. During the actual test, the pressure sensor is attached to the side of the sample, and the data line of the pressure sensor extends from the reserved hole 214 for pressure sensor and is connected to the storage mechanism 6 to obtain the pressure changes around the sample during the loading process.

[0070] Furthermore, the side plate 21 is made of acrylic plate. Acrylic plate has high strength and rigidity. Under the action of axial pressure, acrylic plate is not easy to deform, so that uniform lateral constraint can be applied to the sample. The acrylic plate is transparent, which makes it easy to observe the deformation of the sample. At the same time, the four acrylic plates are clamped by fixing hoops 22 at the upper and lower ends to ensure that the sample will not expand due to lateral deformation during axial compression.

[0071] Furthermore, if Figure 2 As shown, the fixing hoop 22 includes two. Figure 8 As shown, the upper and lower ends of both sides of the first group of side plates 21 are provided with mounting grooves 212 recessed inward from the end surfaces. A fixing hoop 22 is provided at the location of a mounting groove 212. That is, a fixing hoop 22 is provided at both ends of the upper and lower ends of the columnar body for fixing, so that the columnar body can be firmly fixed with a minimum of fixing hoops 22. The fixing hoops 22 at the upper and lower ends clamp the four side plates 21 to ensure that the specimen will not escape due to lateral deformation during axial compression. At the same time, the clamping effect also enhances the lateral constraint of the side plate 21 on the specimen. The rigidity of the side plate 21 and the clamping of the fixing hoop 22 work together to produce a better confining pressure on the specimen.

[0072] Furthermore, the width of the installation groove 212 provided in the first group of side panels 21 is adapted to the width of the fixing hoop 22 , so that after the fixing hoop 22 is provided in the installation groove 212 , the assembly surface of the fixing hoop 22 and the side panel 21 is flat.

[0073] Optional, such as Fig.11 As shown, the fixing hoop 22 includes a fixing strip 221 and a fixing member. There are four fixing strips 221. Figures 11 to 13 As shown, two fixing bars 221 are arranged opposite to each other, and the two sides of the opposite surfaces are provided with fixing grooves 222 recessed from the inside to the outside. The other two fixing bars 221 are arranged in parallel, and the two ends are respectively inserted into the fixing grooves 222 at the corresponding positions and fixed by fixing members. For example, the fixing member is a screw. Fig.12 and Fig.13 As shown, the fixing strip 221 provided with the fixing groove 222 is provided with a first screw hole 223 penetrating from the outer surface toward the groove bottom at the position where the fixing groove 222 is provided. Fig.14 As shown, the two ends of the fixing strips 221 without the fixing grooves 222 are provided with second screw holes 224. When the two ends of the two fixing strips 221 without the fixing grooves 222 are respectively inserted into the fixing grooves 222 at corresponding positions, the fixing strips 221 can be fixed to each other by screwing the screws into the screw holes.

[0074] The fixing hoop 22 of the embodiment of the present application has a stable structure and can firmly fix the column.

[0075] Furthermore, if Figure 1 , Figure 2 , Fig. 9 and Fig.10 As shown, a plurality of acoustic emission probe mounting holes 213 are provided on the side plate 21, and the acoustic emission probe mounting holes 213 are configured to be provided with acoustic emission probes. The acoustic emission probes can collect the acoustic emission signals of sample crushing during the test loading process, and can well reflect the mechanical characteristic behavior of the sample.

[0076] Optionally, the acoustic emission probe mounting holes 213 include four. Fig. 9 and Fig.10 As shown, two acoustic emission probe mounting holes 213 are respectively provided on each of the side panels 21 that are arranged opposite to each other, and the two acoustic emission probe mounting holes 213 are located at the diagonal positions of the side panels 21, so that the acoustic signal of the sample can be accurately obtained. Figure 1 As shown, when the four acoustic emission probe mounting holes 213 in the side projection of the experimental device are located at the four corners of the projection of the side plate 21, the acoustic signal of the sample can be obtained more accurately to obtain the crack development inside the sample and maximize the effect. The experimental device of the embodiment of the present application combines the sample compression test with the acoustic emission test to obtain the acoustic emission signal of the sample during the sample compression process and the sample crushing process.

[0077] Furthermore, if Figure 8 As shown, a through hole 215 is provided in the middle of the side plate 21 on the rear side of the sample. When studying the crack evolution of a sample with a hole, a borehole peep instrument can be placed in the sample hole through the through hole 215 to obtain the crack evolution and development process on the inner surface of the sample hole, which has high versatility.

[0078] Optional, such as Figure 4 As shown, the top surface of the lower pressure head 1 is provided with an annular groove 13, so as to facilitate the positioning of the lower end of the confining pressure providing mechanism 2 during installation, and if the width of the annular groove 13 is consistent with the thickness of the confining pressure providing mechanism 2, it can ensure that the lower end of the confining pressure providing mechanism 2 and the side surface of the lower pressure head 1 are in the same plane. When the confining pressure providing mechanism 2 is installed in place, the side wall of the annular groove 13 will provide a resistance force to the lower end of the confining pressure providing mechanism 2, thereby preventing the confining pressure providing mechanism 2 from slipping.

[0079] If the transverse cross-sectional area of ​​the top pressure head 5 and the bottom pressure head 4 of the uniaxial compression tester is large, the lower pressure head 1 is directly placed on the bottom pressure head 4, the sample is placed on the lower pressure head 1, and the top pressure head 5 directly presses down the upper pressure head 3. However, if the transverse cross-sectional area of ​​the top pressure head 5 and the bottom pressure head 4 of the uniaxial compression tester is small, the lower pressure head 1 is directly placed on the bottom pressure head 4, the sample is placed on the lower pressure head 1, and the top pressure head 5 directly presses down the upper pressure head 3, which easily makes it difficult for the bottom pressure head 4 and the top pressure head 5 to equally press the lower pressure head 1 and the upper pressure head 3 respectively.

[0080] The lower pressure head 1 is provided with a first mounting hole 11 recessed from bottom to top (generally, the first mounting hole 11 is located at the center of the upper pressure head 3); and / or, the upper pressure head 3 is provided with a second mounting hole 31 recessed from top to bottom (generally, the second mounting hole 31 is located at the center of the lower pressure head 1). Without considering the transverse cross-sectional area of ​​the top pressure head 5 and the bottom pressure head 4 of the uniaxial compression testing machine, the bottom pressure head 4 and the top pressure head 5 can well give equal pressure to the lower pressure head 1 and the upper pressure head 3 respectively. Moreover, when the cross-sectional area of ​​the bottom pressure head 4 and the top pressure head 5 is small, the lower pressure head 1 and the upper pressure head 3 can be quickly and firmly fixed by clamping the bottom pressure head 4 and the top pressure head 5 in the first mounting hole 11 or the second mounting hole 31 respectively, so that the test device of the embodiment of the present application can be used in a wider range. Furthermore, the side of the lower pressure head 1 is provided with a first threaded hole 12 penetrating from the side to the first mounting hole 11, and the side of the upper pressure head 3 is provided with a second threaded hole 32 penetrating from the side to the second mounting hole 31. After the bottom pressure head 4 of the uniaxial compression tester is inserted into the first mounting hole 11, a screw is passed through the first threaded hole 12 to abut against the side wall of the bottom pressure head 4 to further fix the bottom pressure head 4. After the top pressure head 5 of the uniaxial compression tester is inserted into the second mounting hole 31, a screw is passed through the second threaded hole 32 to abut against the side wall of the top pressure head 5 to further fix the top pressure head 5.

[0081] The arrangement of the first mounting hole 11 and the second mounting hole 31 enables the test device to realize not only pressurization of a large-sized top pressure head 5 , but also pressurization of a small-sized top pressure head 5 , and has good compatibility.

[0082] For example, the top pressure head 5 and the bottom pressure head 4 of the uniaxial compressor are both cylindrical pressure heads with a diameter of 50 mm. In order to fix the upper pressure head 3 and the lower pressure head 1 to the uniaxial compressor, screws are required for reinforcement. The first mounting hole 11 of the lower pressure head 1 is fixed to the bottom pressure head 4 of the uniaxial compressor, and the screw is passed through the first threaded hole 12 to the side wall of the bottom pressure head 4 for reinforcement. The second mounting hole 31 of the upper pressure head 3 is fixed to the top pressure head 5 of the uniaxial compressor, and the screw is passed through the second threaded hole 32 to the side wall of the top pressure head 5 for reinforcement.

[0083] Another embodiment of the present invention provides a method for using a uniaxial to conventional triaxial compression conversion test device, based on the above-mentioned uniaxial to conventional triaxial compression conversion test device, comprising:

[0084] The lower pressure head 1 is placed on the bottom pressure head 4 of the uniaxial compression tester. When the top pressure head 5 of the uniaxial compressor is a cylindrical pressure head, the first mounting hole 11 of the lower pressure head 1 is fixed to the bottom pressure head 4 of the uniaxial compressor, and the screw is passed through the first threaded hole 12 to press against the side wall of the bottom pressure head 4 for reinforcement.

[0085] Place the sample on the pressing head 1. If the top surface of the pressing head 1 is provided with an annular groove 13, place the sample on the protruding part of the pressing head 1.

[0086] If you need to obtain the pressure around the sample, you need to attach the pressure sensor to the surrounding wall of the sample.

[0087] The confining pressure providing mechanism 2 is arranged on the lower pressure head 1 and the sample is located in the placement cavity of the confining pressure providing mechanism 2 .

[0088] If the confining pressure providing mechanism 2 includes four side plates 21, the two side plates 21 arranged opposite to each other have the same shape, and the two sides of the opposite surfaces of the first group of side plates 21 are respectively provided with embedded grooves 211 recessed from the inside to the outside, and the two ends of the second group of side plates 21 respectively abut against the embedded grooves 211 at corresponding positions, and the fixing hoops 22 include two.

[0089] First, the first set of side plates 21 are arranged parallel to the two sides of the lower pressure head 1, and then the second set of side plates 21 are arranged on the other two sides of the lower pressure head 1, and the two ends of the second set of side plates 21 are respectively against the embedding grooves 211 at the corresponding positions of the first set of side plates 21. The pressure sensor transmission line passes through the pressure sensor reserved hole 214 at the corresponding position and is connected to the storage mechanism 6 to obtain the pressure sensor change data.

[0090] If it is necessary to obtain the acoustic emission signal during the loading process, apply vaseline on the acoustic emission probe and install the acoustic emission probe on the acoustic emission probe installation hole 213. Tap the sample to check whether the acoustic emission probe collects data normally and whether the pressure sensor has a pressure value. Connect the acoustic emission probe to the storage mechanism 6.

[0091] Then, a fixing hoop 22 is provided at both the upper and lower ends of the columnar body for fixing.

[0092] The upper pressure head 3 is arranged at the upper part of the confining pressure providing mechanism 2 and below the top pressure head 5 of the uniaxial compression testing machine. Specifically, the top pressure head 5 of the uniaxial compressor is adjusted to observe whether the lower end of the upper pressure head 3 is aligned with the sample. If it is not aligned with the sample, the sample is adjusted until it is aligned. After the second mounting hole 31 provided on the upper pressure head 3 is aligned and sleeved on the top pressure head 5, the screw is screwed into the second threaded hole 32 for fixing.

[0093] If a sample with a hole is loaded and crack changes in the sample hole need to be obtained, a through hole 215 needs to be provided on the rear side of the confining pressure providing mechanism 2, and a drilling peephole is placed in the sample hole through the through hole 215 and the position is adjusted.

[0094] The upper pressure head 3 extends into the placement cavity under the pressure of the top pressure head 5 and presses down the sample to perform the test, thereby realizing conventional triaxial loading.

[0095] Specifically, the uniaxial compressor, acoustic emission probe, pressure sensor, borehole peep instrument and storage mechanism 6 are started synchronously to obtain the stress-strain curve, acoustic emission energy signal, pressure curve and borehole internal crack evolution video of the sample under conventional triaxial compression.

[0096] When the stress-strain curve displayed by the uniaxial compressor reaches the peak value and shows a clear downward trend, and obvious cracks appear on the sample, the loading is stopped, and the acoustic emission probe, pressure sensor, and borehole peep instrument are turned off at the same time.

[0097] The top pressure head 5 of the uniaxial compressor is moved upward, the acoustic emission probe and the borehole peep instrument are taken out, the fixing hoop 22 and the side plate 21 are disassembled, the sample is removed, and the conventional triaxial compression loading test is completed.

[0098] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other. Each embodiment focuses on the differences from other embodiments.

[0099] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. A uniaxial to conventional triaxial compression conversion test device, characterized in that: It includes a lower pressure head, a confining pressure providing mechanism and an upper pressure head; The lower pressure head is placed on the bottom pressure head of the uniaxial compression testing machine; The sample is placed on the lower pressure head; The confining pressure providing mechanism is provided with a placement cavity, which is arranged on the lower pressure head and allows the sample to be located in the placement cavity; The first axial cross section of the sample is similar to the second axial cross section of the placement cavity, and the area of ​​the first axial cross section is equal to the area of ​​the second axial cross section; The upper pressure head is arranged on the upper part of the confining pressure providing mechanism and below the top pressure head of the uniaxial compression testing machine. When the upper pressure head extends into the placement cavity and presses down the sample under the pressure of the top pressure head, the confining pressure providing mechanism can provide reverse restraint force to the side of the sample.

2. The uniaxial to conventional triaxial compression conversion test device according to claim 1, characterized in that: The confining pressure providing mechanism includes a side plate and a fixing hoop; The side panels include a plurality of pieces, and the plurality of side panels surround a columnar body having the placement cavity; The fixing hoop comprises at least one, and the at least one fixing hoop is sleeved and fixed on the columnar body.

3. The uniaxial to conventional triaxial compression conversion test device according to claim 2, characterized in that: The side panels include four pieces; The four side panels form a prism; The two side panels arranged opposite to each other have the same shape; Both sides of the opposite surfaces of the first group of side panels are respectively provided with embedded grooves recessed from the inside to the outside; The two ends of the second group of side panels respectively abut against the embedding grooves at corresponding positions.

4. The uniaxial to conventional triaxial compression conversion test device according to claim 3, characterized in that: The fixing hoop comprises two; The upper and lower ends of both sides of the first group of side plates are provided with mounting grooves recessed inward from the end surfaces; A fixing hoop is arranged at the location of a mounting groove.

5. The uniaxial to conventional triaxial compression conversion test device according to claim 3 or 4, characterized in that: The fixing hoop comprises a fixing strip and a fixing piece; There are four fixing bars; The two fixing bars are arranged opposite to each other, and the two sides of the opposite surfaces thereof are provided with fixing grooves recessed from the inside to the outside; The other two fixing bars are arranged in parallel, and both ends are respectively inserted into the fixing grooves at corresponding positions and fixed by the fixing parts.

6. The uniaxial to conventional triaxial compression conversion test device according to claim 2, characterized in that: The side plate is provided with a plurality of acoustic emission probe mounting holes, and the acoustic emission probe mounting holes are configured to be used for mounting acoustic emission probes.

7. The uniaxial to conventional triaxial compression conversion test device according to claim 6, characterized in that: The acoustic emission probe mounting holes include four; Two acoustic emission probe mounting holes are respectively arranged on each of the side panels that are arranged opposite to each other, and the two acoustic emission probe mounting holes are located at the diagonal positions of the side panels.

8. The uniaxial to conventional triaxial compression conversion test device according to claim 1, characterized in that: The top surface of the pressing head is provided with an annular groove.

9. The uniaxial to conventional triaxial compression conversion test device according to claim 1 or 6, characterized in that: The lower pressure head is provided with a first mounting hole recessed from bottom to top; And / or, the upper pressure head is provided with a second mounting hole recessed from top to bottom.

10. A method for using a uniaxial to conventional triaxial compression conversion test device, characterized in that: The uniaxial to conventional triaxial compression conversion test device according to claims 1 to 9 above comprises: Place the lower pressure head on the bottom pressure head of the uniaxial compression testing machine; placing the sample on the lower pressure head; The confining pressure providing mechanism is arranged on the lower pressure head and the sample is located in the placement cavity of the confining pressure providing mechanism; The upper pressure head is arranged on the upper part of the confining pressure providing mechanism and below the top pressure head of the uniaxial compression testing machine; The upper pressure head extends into the placement cavity under the pressure of the top pressure head and presses down the sample to perform the test.

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