A device and method for measuring longitudinal wave velocity in a low-temperature high-pressure environment during rock loading

Abstract

The application discloses a kind of low-temperature high-pressure environment under rock loading process longitudinal wave wave velocity measuring device and test method, belong to geotechnical engineering investigation test field, including press, force transmission cavity, cryostat, sleeve and confining pressure control system;The cryostat and press are fixedly connected with workbench;The inside of the cryostat is installed with the sleeve;The sleeve is connected with the confining pressure control system;The workbench is fixedly installed with pressure-bearing disc at the bottom of the cryostat;The anvil of the press and the pressure-bearing disc are all installed with force transmission cavity;Rock specimen is placed in sleeve in the application, and rock specimen is placed between two pressure columns;Adjust cryostat so that the internal temperature of cryostat reaches measurement requirement;Then control confining pressure control system to apply confining pressure, press drives force transmission cavity and pressure column to give rock specimen top pressure;The longitudinal wave wave velocity of rock specimen is detected by ultrasonic detector probe.

Description

Technical Field

[0001] The present invention relates to the field of geotechnical engineering investigation and testing, and particularly relates to a device and a testing method for measuring the longitudinal wave velocity during the loading process of rocks under low temperature and high pressure environments. Background Art

[0002] Wave velocity testing is one of the common geotechnical engineering investigation methods. It can determine the geological characteristics by measuring the wave propagation velocity in rocks or soils, and is a very practical method. Wave velocity testing in geotechnical engineering can determine the properties of soils or rocks, the groundwater level, and cracks and defects in soils or rocks. However, in the western cold region, frozen rock masses are often encountered during geotechnical excavation. It is difficult to achieve a constant temperature environment when testing the wave velocity of frozen rocks, especially when the wave velocity changes during the loading process. Therefore, a device and a testing method for measuring the longitudinal wave velocity during the loading process of rocks under low temperature and high pressure environments are proposed. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the present invention proposes a device and a testing method for measuring the longitudinal wave velocity during the loading process of rocks under low temperature and high pressure environments.

[0004] The object of the present invention can be achieved by the following technical solutions:

[0005] A device for measuring the longitudinal wave velocity during the loading process of rocks under low temperature and high pressure environments includes a press, a force transmission cavity, a low-temperature box, a sleeve, and a confining pressure control system; the low-temperature box and the press are both fixedly connected to the workbench; the sleeve is installed inside the low-temperature box; the sleeve is connected to the confining pressure control system; the workbench fixedly installs a bearing plate at the bottom of the low-temperature box; both the press head of the press and the bearing plate are equipped with force transmission cavities; an ultrasonic detector probe is installed inside the force transmission cavity; a pressure application column is provided on each of the force transmission cavities; the pressure application column is slidably connected to the low-temperature box; the pressure application column is adapted to the sleeve.

[0006] In some embodiments, two guide rails are symmetrically and fixedly installed on the workbench; sliders are slidably connected to the guide rails; rotating seats are fixedly installed on the sliders; rotating shafts are rotatably connected to the rotating seats; the low-temperature box is fixedly connected to the rotating shafts; the workbench is provided with a support base at the lower end of the low-temperature box; the support base abuts against the low-temperature box; the low-temperature box is further provided with a cover plate; the cover plate is connected to the low-temperature box by screw one; a pressure plate one is fixedly installed on the pressing column close to the press; the pressing column close to the press is fixedly connected to the adjacent force transmission cavity; a pressure plate two is fixedly installed on the pressing column close to the bearing plate; the pressing column close to the bearing plate abuts against the adjacent force transmission cavity; the cover plate is slidably connected to the pressing column; the cover plate is arranged between the pressure plate one and the force transmission cavity; the low-temperature box is provided with a fixing ring at the bottom of the sleeve; the pressure plate two is slidably connected to the sleeve; the fixing ring abuts against the pressure plate two.

[0007] In some embodiments, spur gears one are fixedly installed on the rotating shafts; a motor one is fixedly installed on the workbench; a spur gear two is fixedly installed on the motor one; the spur gear two can be meshed with the spur gear one; a recycling box is slidably connected to one side of the workbench close to the motor one; a telescopic push rod is installed on the workbench at the upper end of the recycling box; a push plate is installed on the telescopic push rod; two threaded holes are provided on each of the guide rails; the slider is threadedly connected to one of the threaded holes by screw two.

[0008] In some embodiments, a support frame is installed on the workbench; a screw rod seat is installed on the support frame; a motor two is installed on the screw rod seat; a screw rod is installed on the motor two; a movable seat is threadedly connected to the screw rod; the movable seat is slidably connected to the support frame; a motor three is installed on the movable seat; a rotary rod is installed on the motor three; a cleaning shaft is rotatably connected to the rotary rod; a cleaning brush and a spur gear three are installed on the cleaning shaft; an internal gear ring is installed on the movable seat; the spur gear three is meshed with the internal gear ring.

[0009] In some embodiments, limiting blocks are provided at both ends of the guide rails.

[0010] In some embodiments, a cylindrical cavity is provided inside the force transmission cavity; the cross-section of the cylindrical cavity is in a shape composed of an arc, a horizontal straight line and a connecting line; wherein the central angle corresponding to the arc is greater than 180 degrees, the line segment where the two end points of the arc are located is parallel to the horizontal straight line, and the two ends of the arc and the two ends of the horizontal straight line are respectively connected by one of the connecting lines; the connecting line is a straight line or a curve.

[0011] The present application further provides a method for measuring the longitudinal wave velocity during the rock loading process under a low-temperature and high-pressure environment, which is implemented by using the above measurement device and includes the following steps:

[0012] Connect the probe of the ultrasonic detector to the main unit of the ultrasonic detector, connect the low-temperature box to the refrigeration main unit, and connect the confining pressure control system to the external oil supply pipeline;

[0013] Place the rock specimen in the sleeve, and place the rock specimen between two pressure application columns; adjust the low-temperature box so that the internal temperature of the low-temperature box reaches the measurement requirement;

[0014] Then control the confining pressure control system to apply confining pressure, and the press drives the force transmission cavity and the pressure application column to apply pressure to the top of the rock specimen; detect the longitudinal wave velocity of the rock specimen through the probe of the ultrasonic detector.

[0015] Advantages of the present invention:

[0016] The present invention can both achieve: testing the longitudinal wave velocity of the original geotechnical specimen at a constant low temperature without loading; and can also achieve: testing the change in the longitudinal wave velocity of the geotechnical specimen during the loading and deformation process. BRIEF DESCRIPTION OF THE DRAWINGS<0OO0036>

[0017] The present invention will be further described below with reference to the accompanying drawings.<00OO038>

[0018] Figure 1 It is a three-dimensional structure schematic diagram of the present application;

[0019] Figure 2 It is a three-dimensional schematic diagram of the present application with a moving mechanism;

[0020] Figure 3 It is a schematic diagram of the interior of the low-temperature box of the present application;

[0021] Figure 4 It is a schematic diagram of the cleaning mechanism of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] In the description of the present invention, it should be understood that the terms "opening", "upper", "lower", "thickness", "top", "middle", "length", "inner", "perimeter", etc. indicating orientation or positional relationships are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the components or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention. <OO00056>In the description of this specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0025] A device for measuring the longitudinal wave velocity during the rock loading process in a low-temperature and high-pressure environment, comprising a press 2, a force transmission cavity 6, a low-temperature box 1, a sleeve 3 and a confining pressure control system 4; the low-temperature box 1 and the press 2 are both fixedly connected to the workbench; the sleeve 3 is installed inside the low-temperature box 1; the sleeve 3 is connected to the confining pressure control system 4; a bearing plate 5 is fixedly installed at the bottom of the workbench inside the low-temperature box 1; force transmission cavities 6 are installed on both the indenter of the press 2 and the bearing plate 5; an ultrasonic detector probe 7 is installed inside the force transmission cavity 6; a pressure application column 8 is provided on each of the force transmission cavities 6; the pressure application column 8 is slidably connected to the low-temperature box 1; the pressure application column 8 is adapted to the sleeve 3.

[0026] The method for testing the longitudinal wave velocity during the rock loading process in a low-temperature and high-pressure environment in this application includes the following steps:

[0027] Connect the ultrasonic detector probe 7 to the ultrasonic detector main unit, connect the low-temperature box 1 to the refrigeration main unit, and connect the confining pressure control system 4 to the external oil supply pipeline;

[0028] Place the rock specimen in the sleeve 3, and place the rock specimen between the two pressure application columns 8; adjust the low-temperature box 1 so that the internal temperature of the low-temperature box 1 reaches the measurement requirement;

[0029] Then control the confining pressure control system 4 to apply confining pressure, and the press 2 drives the force transmission cavity 6 and the pressure application column 8 to apply pressure to the top of the rock specimen; detect the longitudinal wave velocity of the rock specimen through the ultrasonic detector probe 7.

[0030] In this application, the press 2 refers to a device that drives the working mechanism through a transmission mechanism by a motor to apply a process force to the workpiece. The transmission mechanism is a speed reduction mechanism of belt drive or gear drive; the working mechanism includes a screw mechanism, a crank connecting rod mechanism and a hydraulic cylinder.

[0031] In this application, the low-temperature chamber 1 refers to a box structure capable of adjusting the internal temperature; its refrigeration method can be achieved by using a refrigerant in combination with a condenser and a compressor; the refrigeration cycle adopts the reverse Carnot cycle, which consists of two isothermal processes and two adiabatic processes. The process is as follows: The refrigerant is adiabatically compressed by the compressor to a higher pressure, consuming work to raise the exhaust temperature. Then, the refrigerant exchanges heat with the surrounding medium isothermally through the condenser and transfers the heat to the surrounding medium. After that, the refrigerant adiabatically expands through the throttle valve to do work, and at this time the temperature of the refrigerant decreases. Finally, the refrigerant absorbs heat from an object with a higher temperature isothermally through the evaporator, reducing the temperature of the cooled object. This cycle repeats continuously to achieve the purpose of cooling; the low-temperature chamber in this application refers to a heat-insulated box, which is connected to the refrigeration host, and a temperature sensor is set inside the box to control the refrigeration of the host according to the temperature change.

[0032] In this application, the confining pressure control system 4 refers to a rubber sleeve inside an external rigid sleeve, that is, a rubber sleeve is installed inside the sleeve, and the confining pressure is applied by applying pressure to the rubber sleeve; it is similar to the patent CN112268806B, a confining pressure loading device based on a split Hopkinson pressure bar; the sleeve consists of an upper sleeve and a lower sleeve, and the upper sleeve and the lower sleeve are connected by connecting columns; the inner arm of the overall sleeve is connected to the rubber sleeve, and the sleeve is placed inside the oil cylinder of the confining pressure control system. By changing the internal oil pressure, pressure is applied to the rubber sleeve, thereby applying confining pressure to the specimen.

[0033] The fixed connection in this application refers to the connection of parts or components without any relative movement after installation; commonly, such as using connecting parts such as screws, splines, and wedge pins to fix the components together. This connection method can be disassembled during maintenance and will not damage the parts. This method can also be called a detachable fixed connection; there are also methods such as welding, riveting, and mortise fitting. Since these methods require forging, sawing, or oxy-fuel cutting to be disassembled during maintenance or replacement, the spare parts generally cannot be used twice; each component of this application can be selected to be fixedly connected by connecting parts or by welding or other methods according to needs.

[0034] In some embodiments, two guide rails 10 are symmetrically and fixedly installed on the workbench; the guide rails 10 are slidably connected with sliders 11; rotating seats 12 are fixedly installed on the sliders 11; rotating shafts are rotatably connected to the rotating seats 12; the low-temperature box 1 is fixedly connected to the rotating shafts; the workbench is provided with a support seat 13 at the lower end of the low-temperature box 1; the support seat 13 abuts against the low-temperature box 1; the low-temperature box 1 is further provided with a cover plate 14; the cover plate 14 and the low-temperature box 1 are connected by a first screw 15; a first pressing plate is fixedly installed on the pressing column 8 close to the press 2; the pressing column 8 close to the press 2 is fixedly connected to the adjacent force transmission cavity 6; a second pressing plate 17 is fixedly installed on the pressing column 8 close to the bearing plate 5; the pressing column 8 close to the bearing plate 5 abuts against the adjacent force transmission cavity 6; the cover plate 14 is slidably connected with the pressing column 8; the cover plate 14 is arranged between the first pressing plate and the force transmission cavity 6; the low-temperature box 1 is provided with a fixing ring 18 at the bottom of the sleeve 3; the second pressing plate 17 is slidably connected with the sleeve 3; the fixing ring 18 abuts against the second pressing plate 17;

[0035] When conducting an experiment, the support seat 13 abuts against the low-temperature box 1, thereby preventing the low-temperature box 1 from rotating; after the experiment, the first screw 15 is loosened, the press 2 is driven to move the force transmission cavity 6, the pressing column 8 and the first pressing plate upward, and the cover plate 14 will be pulled upward by the first pressing plate, and the cover plate 14 is separated from the low-temperature box 1; then by moving the slider 11, the rotating seat 12 and the low-temperature box 1 are moved away from the bottom of the press 2, and then the low-temperature box 1 is rotated so that the second pressing plate 17 faces upward, and a cushion block or a rectangular pipe can be erected on the guide rail 10 or the slider 11 to abut against the low-temperature box 1, and then the pressing column 8 is knocked, and the pressing column 8 knocks out the rock specimen through the second pressing plate 17; at the same time, when loading the rock specimen, the low-temperature box 1 can also be placed in the above position, but at this time the second pressing plate 17 is at the bottom.

[0036] In some embodiments, a first spur gear 19 is fixedly installed on each rotating shaft; a first motor 20 is fixedly installed on the workbench; a second spur gear 21 is fixedly installed on the first motor 20; the second spur gear 21 can be meshed with the first spur gear 19; a recovery box 22 is slidably connected to one side of the workbench close to the first motor 20; a telescopic push rod 23 is installed on the workbench at the upper end of the recovery box 22; a push plate 24 is installed on the telescopic push rod 23; two threaded holes are provided on each of the guide rails 10; the slider 11 is threadedly connected to one threaded hole by a second screw 25; after loosening the second screw 25, the low-temperature box 1 is moved until the first spur gear 19 is meshed with the second spur gear 21, and then the slider 11 is connected to the threaded hole by the second screw 25; then the first motor 20 is driven to rotate the second spur gear 21 and the first spur gear 19, thereby driving the rotating shaft and the low-temperature box 1 to rotate, so that the pressing column 8 faces the push plate 24, and the telescopic push rod 23 is driven to move the push plate 24, thereby pushing the pressing column 8 and the second pressing plate 17 to move, so as to push the rock specimen, the pressing column 8 and the second pressing plate 17 into the recovery box 22, and then the pressing column 8 and the second pressing plate 17 are retrieved from the recovery box 22; wherein the telescopic push rod 23 can be a hydraulic push rod or an electric push rod.

[0037] In some embodiments, a support frame 26 is installed on the workbench; a screw base is installed on the support frame 26; a second motor 27 is installed on the screw base; a screw 28 is installed on the second motor 27; the screw 28 is threadedly connected to a movable seat 29; the movable seat 29 is slidably connected to the support frame 26; a third motor 30 is installed on the movable seat 29; a rotary rod 31 is installed on the third motor 30; a cleaning shaft 32 is rotatably connected to the rotary rod 31; a cleaning brush 33 and a third spur gear 34 are installed on the cleaning shaft 32; an internal gear ring 35 is installed on the movable seat 29; the third spur gear 34 meshes with the internal gear ring 35; after the rock specimen is taken out, there are residues inside the sleeve 3. At this time, the low-temperature box 1 is driven by the first motor 20 to rotate to the horizontal position, and the opening of the sleeve 3 is directly facing the cleaning brush 33; the screw 28 is driven to rotate by the second motor 27, and the screw 28 drives the movable seat to move along the support frame 26 through the thread, so that the cleaning brush 33 extends into the sleeve 3. Then, the third motor 30 drives the rotary rod 31 and the cleaning shaft 32 to rotate. When the cleaning shaft rotates around the axis of the third motor 30, the third spur gear 34 will rotate around the internal gear ring 35. Thus, under the meshing action of the third spur gear 34 and the internal gear ring 35, the cleaning shaft drives the cleaning brush 33 to rotate, so as to sweep off the debris attached to the inside of the sleeve 3.

[0038] In some embodiments, limit blocks 36 are provided at both ends of the guide rail 10, and the limit blocks 36 are used to prevent the slider 11 from moving out of the guide rail 10.

[0039] In some embodiments, a cylindrical cavity 37 is provided inside the force transmission cavity 6; the cross-section of the cylindrical cavity 37 is in a shape composed of an arc, a horizontal straight line and a connecting line; where the central angle corresponding to the arc is greater than 180 degrees, the line segment where the two end points of the arc are located is parallel to the horizontal straight line, and the two ends of the arc and the two ends of the horizontal straight line are respectively connected by a connecting line; the connecting line is a straight line or a curve; the cross-sectional shape of the cylindrical cavity 37 is approximately a semi-circular arched roadway, the upper part exceeding half is circular, the lower part is a horizontal straight line, and the straight line and the arc are chamfered to reduce stress concentration during the loading process, make the force more reasonable, the deformation of the cavity under pressure is smaller, and the deformation compared with the rock can be ignored.

[0040] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A device for measuring longitudinal wave velocity during rock loading under low temperature and high pressure conditions, characterized in that, The system includes a press (2), a force transmission cavity (6), a cryogenic chamber (1), a sleeve (3), and a confining pressure control system (4); the cryogenic chamber (1) and the press (2) are both fixedly connected to a workbench; the sleeve (3) is installed inside the cryogenic chamber (1); the sleeve (3) is connected to the confining pressure control system (4); a pressure plate (5) is fixedly installed on the bottom of the cryogenic chamber (1) on the workbench; the press head of the press (2) and the pressure plate (5) are both equipped with force transmission cavities (6); an ultrasonic detector probe (7) is installed inside the force transmission cavity (6); each force transmission cavity (6) is provided with a pressure column (8); the pressure column (8) is slidably connected to the cryogenic chamber (1); the pressure column (8) is adapted to the sleeve (3); The workbench is symmetrically and fixedly mounted with two guide rails (10); the guide rails (10) are slidably connected to sliders (11); each slider (11) is fixedly mounted with a rotating seat (12); each rotating seat (12) is rotatably connected to a rotating shaft; the low-temperature chamber (1) is fixedly connected to the rotating shaft; the workbench is provided with a support seat (13) at the lower end of the low-temperature chamber (1); the support seat (13) abuts against the low-temperature chamber (1); the low-temperature chamber (1) is also provided with a cover plate (14); the cover plate (14) is connected to the low-temperature chamber (1) by screws (15); the pressure column (8) near the press (2) is fixedly mounted with a pressure... The pressure plate 1 has a pressure column (8) near the press (2) fixedly connected to the adjacent force transmission cavity (6); the pressure column (8) near the pressure plate (5) is fixedly installed with a pressure plate 2 (17), and the pressure column (8) near the pressure plate (5) abuts against the adjacent force transmission cavity (6); the cover plate (14) is slidably connected to the pressure column (8); the cover plate (14) is disposed between the pressure plate 1 and the force transmission cavity (6); the low temperature chamber (1) has a fixing ring (18) at the bottom of the sleeve (3); the pressure plate 2 (17) is slidably connected to the sleeve (3); the fixing ring (18) abuts against the pressure plate 2 (17).

2. The longitudinal wave velocity measuring device for rock loading under low temperature and high pressure environment as described in claim 1, characterized in that, Each of the rotating shafts is fixedly mounted with a spur gear (19); the workbench is fixedly mounted with a motor (20); the motor (20) is fixedly mounted with a spur gear (21); the spur gear (21) can mesh with the spur gear (19); a recycling bin (22) is slidably connected to the side of the workbench near the motor (20); a telescopic push rod (23) is installed on the upper end of the recycling bin (22) on the workbench; a push plate (24) is installed on the telescopic push rod (23); each of the guide rails (10) is provided with two threaded holes; the slider (11) is threadedly connected to one of the threaded holes by a screw (25).

3. The longitudinal wave velocity measuring device for rock loading under low temperature and high pressure environment according to claim 2, characterized in that, The workbench is equipped with a support frame (26); the support frame (26) is equipped with a screw seat; the screw seat is equipped with a second motor (27); the second motor (27) is equipped with a screw (28); the screw (28) is threadedly connected to a movable seat (29); the movable seat (29) is slidably connected to the support frame (26); the movable seat (29) is equipped with a third motor (30); the third motor (30) is equipped with a rotary rod (31); the rotary rod (31) is rotatably connected to a cleaning shaft (32); the cleaning shaft (32) is equipped with a cleaning brush (33) and a spur gear (34); the movable seat (29) is equipped with an internal gear ring (35); the spur gear (34) meshes with the internal gear ring (35).

4. The longitudinal wave velocity measuring device for rock loading under low temperature and high pressure environment according to claim 3, characterized in that, Limiting blocks (36) are provided at both ends of the guide rail (10).

5. The longitudinal wave velocity measuring device for rock loading under low temperature and high pressure environment according to claim 1, characterized in that, The force transmission cavity (6) has a cylindrical cavity (37) inside; the cross-section of the cylindrical cavity (37) is a shape composed of a circular arc, a horizontal straight line and a connecting line; The central angle corresponding to the arc is greater than 180 degrees, the line segment where the two endpoints of the arc are located is parallel to the horizontal straight line, and the two ends of the arc and the two ends of the horizontal straight line are respectively connected by a connecting line; the connecting line is a straight line or a curve.

6. A method for testing longitudinal wave velocity during rock loading under low temperature and high pressure, implemented using the measuring device described in any one of claims 1 to 5, characterized in that, Includes the following steps: Place the rock specimen in the sleeve (3) and place the rock specimen between the two pressure columns (8); adjust the low temperature chamber (1) so that the internal temperature of the low temperature chamber (1) reaches the measurement requirements; Next, the confining pressure control system (4) applies confining pressure, and the press (2) drives the force transmission cavity (6) and the pressure column (8) to apply pressure to the top of the rock specimen; the longitudinal wave velocity of the rock specimen is detected by the ultrasonic detector probe (7).

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