Device for measuring expansion speed of subcritical crack of rock

Abstract

The utility model relates to a device for measuring the expansion speed of a subcritical crack of rock. A first supporting table is arranged at the bottom of a rack; the driving mechanism comprises a motor arranged on the upper portion of the rack, and an output shaft of the motor is connected with a lead screw. The moving mechanism comprises a sliding plate, and the back of the sliding plate is slidably connected with the rack. A fixing block with a screw hole is arranged at the front part of the sliding plate, and the lead screw is screwed in the screw hole; a pressing rod is arranged at the lower part of the sliding plate; a pressing head is arranged at the tail end of the pressing rod; the pressure sensor is arranged between the pressing rod and the pressing head; the displacement sensor is arranged on the sliding plate; a heating plate is arranged on the sample table and is used for placing a rock sample, and the rock sample is positioned below the pressure head; according to the device, different temperatures are set through the heating plate to heat the rock sample, the driving mechanism and the moving mechanism are used for providing power for the experiment and controlling the load applied to the rock sample, the load applied to the rock sample and the load and time in the stress release stage are recorded, and then the subcritical crack growth rate of the rock at different temperatures is measured.

Description

Technical Field

[0001] The utility model relates to the technical field of rock mechanics, and particularly relates to a device for measuring the subcritical crack propagation speed of rocks. Background Technique

[0002] Subcritical crack propagation is a major issue in rock mechanics and a fundamental problem faced in the underground disposal of nuclear waste, the exploitation and storage of underground energy, the study of earthquake mechanisms, and the long-term stability evaluation of geotechnical engineering. The common experimental research methods for subcritical crack propagation can be divided into direct methods and indirect methods. The common direct method is represented by the double torsion experiment, which can accurately measure the crack propagation rate and the stress intensity factor. The indirect method, such as the Brazilian disk splitting method, calculates the crack propagation rate based on the measured value of the stress intensity factor, reflecting the average fracture behavior during the fracture time. The double torsion method was proposed by Outwater, Kies, and others in the 1960s and is widely used due to its relatively simple design and rich space for adaptive improvement.

[0003] The double torsion experiment is also divided into three loading methods. Among them, the constant displacement relaxation method is the most commonly used method by current researchers. That is, in the experiment, the displacement of the driving rod is kept unchanged, and the load change curve with time is recorded. Then, through data processing, the fracture toughness of the material can be obtained, and the relationship between the subcritical crack propagation rate of the rock crack and the stress intensity factor at the crack tip can be established.

[0004] As an important influencing factor for the subcritical crack propagation speed of rocks, since the real environment deep in the earth's crust cannot be simulated in the laboratory environment, Barry Kean Atkinson and others have successively proposed the possible influence of temperature on the subcritical crack propagation process of rocks. According to Charles' reaction rate theory, the higher the temperature, the lower the activation energy at the crack tip, that is, it promotes various physical and chemical reactions of the rock, resulting in a faster crack propagation speed and the rock being more fragile. However, there is no complete simulation experiment on rock materials at different temperatures in the existing technology.

[0005] Therefore, there is an urgent need to develop a device that can measure the subcritical crack propagation speed of rocks at different temperatures, which can measure the subcritical crack propagation rate of rocks using the constant displacement relaxation method in different temperature environments. Content of the Utility Model

[0006] Aiming at at least one of the above problems in the existing technology, the purpose of the utility model is to provide a device for measuring the subcritical crack propagation speed of rocks, which can heat the rock sample at different temperatures through a heating plate and can measure the subcritical crack propagation rate of rocks at different temperatures.

[0007] To achieve the above object, the present utility model adopts the following technical solutions:

[0008] A device for measuring the subcritical crack propagation speed of rocks, comprising:

[0009] A frame, with a first support platform provided at its bottom;

[0010] A driving mechanism, including a motor, the motor is provided at the upper part of the frame, and the output shaft of the motor is connected to a lead screw;

[0011] A moving mechanism, including a slide plate, the back of the slide plate is slidably connected to the frame; a fixed block with a threaded hole is provided at the front of the slide plate, and the lead screw is screwed into the threaded hole; a pressure rod is provided at the lower part of the slide plate, and a pressure head is provided at the end of the pressure rod;

[0012] A pressure sensor, provided between the pressure rod and the pressure head;

[0013] A displacement sensor, provided on the slide plate;

[0014] A sample stage, on which a heating plate is provided, the heating plate is used to place the rock sample, and the rock sample is located below the pressure head.

[0015] Preferably, the frame includes the first support platform, the second support platform and a vertical plate. Four columns are provided between the first support platform and the second support platform. The vertical plate is provided on the second support platform. The motor is provided at the upper part of the vertical plate. The slide plate is slidably connected to the vertical plate. A through hole is provided on the second support platform, and the pressure rod passes through the through hole.

[0016] Preferably, a slide rail is provided on the vertical plate, and a sliding groove slidably connected to the slide rail is provided on the slide plate.

[0017] Preferably, the sample stage is provided with a groove for containing a solution.

[0018] Preferably, the bottom surface of the groove is flat, and four arc-shaped bumps are provided on the bottom surface of the groove.

[0019] Preferably, the connection line of the four bumps is a rectangle.

[0020] Preferably, the heating plate is provided with holes equal in number to the bumps. Each bump is inserted into the corresponding hole and protrudes from the hole, and the bottom surface of the heating plate is higher than the bottom surface of the groove. All the bumps are used to support the rock sample.

[0021] Preferably, the bottom surface of the pressure head is provided with four downwardly protruding pressure points.

[0022] Due to the above technical solutions adopted by the present utility model, it has the following advantages:

[0023] 1. The device for measuring the subcritical crack propagation rate of rock provided by the present utility model heats the rock sample by setting different temperatures on the heating plate, uses the driving mechanism and the moving mechanism to provide power for the experiment and control the load applied to the rock sample, records the load and time in the loading and stress release stages applied to the rock sample, and thus realizes the measurement of the subcritical crack propagation rate of rock at different temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 FIG. is a schematic structural diagram of a device for measuring the subcritical crack propagation rate of rock provided by an embodiment of the present utility model.

[0025] Figure 2 FIG. is an enlarged schematic view of the sample stage area of this embodiment of the present utility model.

[0026] Figure 3 FIG. is a top view schematic diagram of the heating plate of this embodiment of the present utility model.

[0027] Reference numerals in the drawings:

[0028] 1 is the first support platform, 2 is the second support platform, 3 is the vertical plate, 4 is the column, 5 is the motor, 6 is the lead screw, 7 is the slide plate, 8 is the fixed block, 9 is the pressure rod, 10 is the pressure head, 11 is the pressure sensor, 12 is the sample stage, 13 is the heating plate, 14 is the rock sample, 15 is the bump, 16 is the hole, 17 is the pressure point, 18 is the displacement sensor. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] To make the objectives, technical solutions and advantages of the present utility model clearer, the technical solutions of the present utility model will be clearly and completely described below with reference to the drawings. Apparently, the described embodiments are some but not all of the embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without making creative efforts shall fall within the protection scope of the present utility model.

[0030] In the description of the present utility model, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the system or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present utility model.

[0031] In the description of the present utility model, it should be noted that unless otherwise clearly specified and defined, the terms "assembly", "installation", and "connection" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0032] A device for measuring the subcritical crack propagation speed of rocks provided by the present utility model can heat a rock sample by setting different temperatures on a heating plate, and can measure the subcritical crack propagation rate of rocks at different temperatures.

[0033] Next, the embodiments of the present utility model will be described in detail with reference to the drawings.

[0034] Embodiment

[0035] Please refer to Figure 1 and Figure 2 As shown, a device for measuring the subcritical crack propagation speed of rocks provided by this embodiment includes a frame, a driving mechanism, a moving mechanism, a pressure sensor, a displacement sensor, and a sample stage:

[0036] The frame includes a first support platform 1, a second support platform 2, and a vertical plate 3. The first support platform 1 is arranged at the bottom of the frame. Both the first support platform 1 and the second support platform 2 are rectangular plates, and both the first support platform 1 and the second support platform 2 can be made of metal materials such as stainless steel.

[0037] Four columns 4 are arranged between the first support platform 1 and the second support platform 2. The four columns 4 are arranged at the four corners of the first support platform 1 and the second support platform 2. The four columns 4 are screwed to the first support platform 1 and the second support platform 2, so that the second support platform 2 is stably supported above the first support platform 1.

[0038] The vertical plate 3 is arranged on the second support platform 2, and the two can be connected by bolts. The vertical plate 3 serves as the supporting main body.

[0039] The driving mechanism includes a motor 5. The motor 5 is arranged at the upper part of the frame, and a lead screw 6 is connected to the output shaft of the motor;

[0040] Specifically, the motor 5 of the driving mechanism is fixedly installed at the upper part of the vertical plate 3; the motor 5 is a stepping motor, and the output shaft of the motor 5 extends vertically downward along the vertical plate 3. There is an installation groove on the vertical plate 3, and the motor 5 is received and fixed in the installation groove.

[0041] The moving mechanism includes a sliding plate 7, the back of the sliding plate 7 is slidably connected to the frame; a fixing block 8 with a threaded hole is arranged at the front of the sliding plate 7, and a lead screw 6 is screwed into the threaded hole; a pressure bar 9 is arranged at the lower part of the sliding plate 7, and a pressure head 10 is arranged at the end of the pressure bar 9;

[0042] Specifically, the vertical plate 3 is provided with a slide rail in the vertical direction, the cross-section of the slide rail is a dovetail-shaped track, and a chute slidably connected to the slide rail is opened on the sliding plate 7, and the chute is a dovetail groove. The slide rail and the chute can ensure that the sliding plate 7 slides along the vertical plate 3 in the vertical direction.

[0043] The fixing block 8 is a square block, the fixing block 8 and the sliding plate 7 are an integral body, a threaded hole is opened in the fixing block 8 in the vertical direction, and the lead screw 6 is screwed into the threaded hole; when the motor 5 is started and the motor 5 drives the lead screw 6 to rotate, the fixing block 8 moves along the lead screw 6, and then drives the sliding plate 7 to slide along the vertical plate 3, and the sliding plate 7 can drive the pressure bar 9 and the pressure head 10 to move.

[0044] The upper part of the pressure bar 9 is fixed on the sliding plate 7 in the vertical direction, the pressure bar 9 is a round steel bar, and a through hole is opened on the second support platform 2, and the pressure bar 9 extends downward through the through hole.

[0045] A notch is opened at the top of the pressure head 10, and the inner diameter of the notch is larger than the outer diameter of the pressure bar 9; a pressure sensor 11 is arranged between the pressure bar 9 and the pressure head 10. Specifically, the pressure sensor 11 is installed on the bottom surface of the notch to connect the pressure bar 9 and the pressure head 10.

[0046] A displacement sensor 18 is arranged on the sliding plate 7 for detecting the displacement of the pressure bar 9 along the axial direction. When the sliding plate 7 moves, the displacement sensor 11 moves with the sliding plate 7, and the pressure bar 9 is fixedly connected, so the displacement of the pressure bar 9 along the axial direction can be detected.

[0047] A heating plate 13 is arranged on the sample stage 12, the heating plate 13 is a silicone rubber heating plate, the heating plate 13 is connected to a temperature control box, and the heating plate 13 is used to place a rock sample 14, and the rock sample 14 is located below the pressure head 10.

[0048] Specifically, a groove for holding a solution is opened at the top of the sample stage 12, the groove is a rectangular groove, the bottom surface of the groove is flat, and four arc-shaped bumps 15 are arranged on the bottom surface of the groove. The connection line of the four bumps 15 is a rectangle.

[0049] Please refer to Figure 2 and Figure 3 As shown, the heating plate 13 is laid flat on the bottom of the groove, the heating plate 13 is provided with holes 16 equal in number to the bumps 15, each bump 15 is inserted into the corresponding hole 16 and protrudes from the hole, and the bottom surface of the heating plate 13 is higher than the bottom surface of the groove. All the bumps 15 are used to support the rock sample 14.

[0050] The bottom surface of the indenter 10 is provided with four downwardly protruding pressing points 17, and the four pressing points 17 are distributed at four different positions at the bottom of the indenter 10. The connection lines of the four pressing points 17 form a rectangle.

[0051] In this embodiment, it further includes a control processor. The control processor includes a data acquisition unit and a data processing unit that are interconnected. The data acquisition unit is connected to the pressure sensor 11 and the displacement sensor 18. The data acquisition unit transmits the acquired data to the data processing unit for data processing and analysis. The data processing unit is connected to the motor 5 for controlling the operation of the motor 5. The data processing unit can be a computer, and the data acquisition unit is a DAQ data acquisition device.

[0052] The working process of the rock subcritical crack propagation speed measuring device in this embodiment is as follows: First, place the rock sample 14 on the four convex points 15 in the groove of the sample stage 12. The bottom of the rock sample 14 has a through notch located between two columns of convex points 15. Specifically, the rock sample 14 is a rectangular thin plate made of ordinary rock by grinding, with a length of 75 mm, a width of 25 mm, and a thickness of 2.5 mm. Then, a through groove with a width of 1 mm and a depth of about 1 / 3 of the thickness is sawn along the central axis of the rock thin plate with a diamond saw blade. This through groove is the notch. Add a solution to the sample groove and set the temperature required for the experiment in the temperature control box. Start the motor 5. The rotation of the motor 5 drives the rotation of the lead screw 6, and the rotation of the lead screw 6 drives the slide plate 7 to move downward. At the same time, the displacement sensor 18 and the pressure rod 9 on the slide plate 7 move synchronously with the slide plate 7 until the indenter 10 at the end of the pressure rod 9 contacts the demonstration rock sample 14 in the groove of the sample stage 12.

[0053] After the rock sample 14 is stably in contact with the indenter 10, set the motor 5 to move downward for loading at a speed of 0.05 mm / s. Cracks start to appear from the moment of contact, and then as the indenter 10 descends and the pressure increases, the cracks gradually expand and eventually cause the rock to break. The DAQ data acquisition device collects the load and time data of the rock sample 14 during loading and observes the load value returned by the pressure sensor 11. When the load value displayed on the pressure sensor 11 tends to be stable, apply pressure again to 80%-90% of the critical value, and then wait for the load to relax and repeat this step until the specimen breaks. Then, control the motor 5 to reverse, move the pressure rod 9 upward, and take out the rock sample 14 to complete a set of experiments.

[0054] The rock subcritical crack propagation velocity measuring device of this embodiment. The driving mechanism and the moving mechanism provide power for the experiment and control the load. The displacement sensor 18 records the displacement of the indenter 10, and the deformation amount of the rock sample 14 is reflected by the displacement amount of the indenter 10 descending. During the fracturing process, the displacement amount of the pressure bar 9 is basically unchanged after the indenter 10 presses on the rock sample 14 and before the sample cracks. When the displacement of the pressure bar 9 occurs, the rock sample 14 fractures, and the stress intensity factor of the rock sample can be obtained. The sample stage 12 places the rock sample 14 specimens, and different liquids can be poured into it. The boiling point of the liquid is greater than 150 °C, and the rock sample 14 is submerged to simulate the subcritical crack propagation experiment under different environmental conditions. The heating plate 13 made of silicone rubber is placed in the sample stage 12 to create different temperature environments for the experiment. The temperature control box is used to control the experiment temperature, and the adjustable temperature range is 0 - 150 °C, and the adjustment accuracy is 0.5 °C. The DAQ data collector and the pressure sensor 11 collect the load and time data of the rock sample 14 during the loading and stress release stages and import them into the data processing unit. The data processing unit generates the load-time curve during the loading and stress release stages and calculates the fracture toughness and the crack propagation velocity.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A rock subcritical crack growth rate measuring device, characterized in that: include: A frame, a first supporting platform is arranged at the bottom of the frame; The driving mechanism comprises a motor, wherein the motor is arranged on the upper part of the frame, and the output shaft of the motor is connected to a lead screw; The moving mechanism comprises a slide plate, the back of which is slidably connected to the frame; a fixing block with a thread hole is arranged at the front of the slide plate, and the lead screw is screwed into the thread hole; a pressure rod is arranged at the lower part of the slide plate, and a pressure head is arranged at the end of the pressure rod; A pressure sensor is arranged between the pressure rod and the pressure head; A displacement sensor is arranged on the slide plate; The sample stage is provided with a heating plate, the heating plate is used to place the rock sample, and the rock sample is located below the pressure head.

2. The rock subcritical crack growth rate measuring device according to claim 1, characterized in that: The frame includes the first support platform, the second support platform and a vertical plate, four columns are arranged between the first support platform and the second support platform, the vertical plate is arranged on the second support platform, the motor is arranged on the upper part of the vertical plate, the slide plate is slidably connected to the vertical plate, a through hole is opened on the second support platform, and the pressure rod passes through the through hole.

3. The rock subcritical crack growth rate measuring device according to claim 2, characterized in that: The vertical plate is provided with a slide rail, and the slide plate is provided with a slide groove which is slidably connected with the slide rail.

4. The rock subcritical crack growth rate measuring device according to claim 1, characterized in that: The sample stage is provided with a groove for holding a solution.

5. The rock subcritical crack growth rate measuring device according to claim 4, characterized in that: The bottom surface of the groove is flat, and four arc-shaped convex points are arranged in the bottom surface of the groove.

6. The rock subcritical crack growth rate measuring device according to claim 5, characterized in that: The connecting line of the four protrusions is a rectangle.

7. The rock subcritical crack growth rate measuring device according to claim 5, characterized in that: The heating plate is provided with holes having the same number as the protrusions, each of the protrusions is inserted into and extends out of the corresponding hole, and the bottom surface of the heating plate is higher than the bottom surface of the groove, and all the protrusions are used to support the rock sample.

8. The rock subcritical crack growth rate measuring device according to claim 1, characterized in that: The bottom surface of the pressure head is provided with four downwardly protruding pressure points.

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