Device and method for testing rock crack propagation parameters under thermal shock

Abstract

The invention discloses a device and a method for testing rock crack propagation parameters under thermal shock. The testing device comprises a base. A first abutting piece is arranged at the end of the supporting plate; the pressure applying mechanism is telescopic, and a second abutting piece is arranged at the end of the pressure applying mechanism; the heating piece comprises a first heating plate and a second heating plate, the first heating plate is provided with a first through hole for the first abutting piece to pass through, and the second heating plate is provided with a second through hole for the second abutting piece to pass through; and the coil surrounds the outer side of the heating piece, and the coil heats the heating piece through electromagnetic induction. According to the testing device, the rock sample is heated through the heating piece, and the rock sample is uniformly heated through the first heating plate and the second heating plate. Through the first abutting piece and the second abutting piece which are arranged in a staggered mode, when the pressure applying mechanism applies pressure, the rock sample can be subjected to torsional force so as to observe the crack propagation condition of the rock sample. The invention relates to the technical field of civil engineering and rock engineering.

Description

Technical Field

[0001] The present application relates to the technical fields of civil engineering and rock engineering, and particularly relates to a device and method for testing rock crack propagation parameters under thermal shock. Background Art

[0002] At present, nuclear energy is an important clean energy source and also has an important position in national defense and military industries. Under this background, the storage of nuclear waste has become a key issue to be studied. According to national standards and the treatment requirements of the International Atomic Energy Agency, high-level radioactive waste must be solidified and then placed in special containers such as stainless steel barrels, and then buried in strata at least 500 meters deep. However, due to the high radioactivity of radioactive waste, heat will be continuously released outward after it is buried, which will affect the stability of the surrounding rock under the long-term action of temperature-stress coupling.

[0003] Since rock itself is a material with micro-cracks inside, during the continuous heat release of high-level radioactive waste, the cracks inside the surrounding rock mass will continuously expand forward in a stable and quasi-static manner, that is, subcritical crack propagation. There is an important connection between the stability of the surrounding rock mass of high-level radioactive waste and rock crack propagation. Therefore, it is of great value to study the subcritical crack propagation of the surrounding rock mass under the heat release state of high-level radioactive waste.

[0004] For this reason, an experimental device needs to be designed that can simulate the subcritical crack propagation of the rock mass after heating and thereby explore the fracture toughness of the rock mass. Summary of the Invention

[0005] The present application aims to solve at least one of the technical problems existing in the prior art. For this purpose, the present application provides a device for testing rock crack propagation parameters under thermal shock, which can simulate the subcritical crack propagation of the rock mass after heating and explore its fracture toughness.

[0006] The present application also provides a testing method using the above-mentioned device for testing rock crack propagation parameters under thermal shock.

[0007] The device for testing rock crack propagation parameters under thermal shock according to the first aspect embodiment of the present application includes:

[0008] A base;

[0009] A support plate detachably connected to the base, with a first abutting member provided at the end of the support plate;

[0010] A pressing mechanism capable of telescoping and having a second abutting member provided at its end;

[0011] A heating element, which includes a first heating plate and a second heating plate connected to each other. There is a heating space reserved between the first heating plate and the second heating plate. The first heating plate is provided with a first through hole for the first abutting member to pass through, and the second heating plate is provided with a second through hole for the second abutting member to pass through;

[0012] A coil, which is wound around the outside of the heating element. The coil heats the heating element through electromagnetic induction;

[0013] Wherein, a rock specimen can be placed in the heating space. The first abutting member supports the rock specimen, and the pressing mechanism applies pressure to the rock specimen. The first abutting member and the second abutting member are arranged non-coaxially.

[0014] The rock crack propagation parameter testing device according to the embodiment of the present application has at least the following beneficial effects: The rock specimen is heated by the heating element, and the first heating plate and the second heating plate are used to make the rock specimen heated evenly. Through the misaligned first abutting member and second abutting member, when the pressing mechanism applies pressure, the rock specimen can be subjected to a torsional force, so as to facilitate observing the crack propagation of the rock specimen under the action of external force.

[0015] According to some embodiments of the present application, the base is provided with a chute, and the support plate slides into one end of the chute to realize the connection between the support plate and the base.

[0016] According to some embodiments of the present application, the number of the support plates is at least two, and the number of the first abutting members is at least four.

[0017] According to some embodiments of the present application, each of the first abutting members is spherical to achieve point-surface contact with the rock specimen.

[0018] According to some embodiments of the present application, the second abutting member is spherical to achieve point-surface contact with the rock specimen.

[0019] According to some embodiments of the present application, the pressing mechanism is provided with at least two of the second abutting members, and the second abutting members are arranged side by side.

[0020] According to some embodiments of the present application, the rock crack propagation parameter testing device under thermal shock further includes a coil bracket, and the coil is fixed to the base through the coil bracket.

[0021] According to some embodiments of the present application, the rock crack propagation parameter testing device under thermal shock further includes a thermocouple, and the thermocouple is installed inside the rock specimen.

[0022] According to some embodiments of the present application, the rock crack propagation parameter testing device under thermal shock further includes an acoustic emission device, and the acoustic emission device is installed on the surface of the rock specimen.

[0023] The testing method according to the second aspect embodiment of the present application is carried out by using the above-mentioned rock crack propagation parameter testing device under thermal shock, and includes the following steps:

[0024] Put the rock specimen into the heating space so that it is supported by the first abutting member on the support plate;

[0025] Energize the coil, and based on electromagnetic induction, generate eddy currents inside the heating element, so that the heating element heats up, and further heat the rock specimen;

[0026] When the rock specimen is heated to a predetermined temperature, start the pressing mechanism so that the second abutting member contacts the rock specimen and applies a force;

[0027] Observe the torsion situation of the rock specimen under high temperature and torsional force, and record the crack propagation situation of the rock specimen.

[0028] The testing method according to the embodiments of the present application has at least the following beneficial effects: the heating element is used to heat the rock specimen to simulate the heating of the rock in a high-radiation environment, and the pressing mechanism is used to apply an external force to the rock specimen to complete the double torsion experiment. Heating and pressing can be carried out simultaneously, so as to be closer to the real situation of the rock in a high-radiation environment.

[0029] Additional aspects and advantages of the present application will be given in part in the following description, become apparent in part from the following description, or be understood through the practice of the present application. Description of the Drawings

[0030] The drawings are used to provide a further understanding of the technical solutions disclosed in the present application, and constitute a part of the specification. Together with the embodiments disclosed in the present application, they are used to explain the technical solutions of the present disclosure, and do not constitute a limitation to the technical solutions disclosed in the present application.

[0031] Figure 1 It is a three-dimensional view of the rock crack propagation parameter testing device under thermal shock according to the first aspect embodiment of the present application;

[0032] Figure 2 It is a three-dimensional view of the support plate in the rock crack propagation parameter testing device under thermal shock according to the first aspect embodiment of the present application;

[0033] Figure 3 It is a three-dimensional view of the pressing mechanism in the rock crack propagation parameter testing device under thermal shock according to the first aspect embodiment of the present application;

[0034] Figure 4 This is a three-dimensional view of the heating element in the rock crack propagation parameter testing device under thermal shock according to the first aspect embodiment of the present application;

[0035] Figure 5 This is a three-dimensional view of the coil and the coil bracket in the rock crack propagation parameter testing device under thermal shock according to the first aspect embodiment of the present application;

[0036] Figure 6 This is a schematic diagram after the thermocouple is installed on the rock specimen in the rock crack propagation parameter testing device under thermal shock according to the first aspect embodiment of the present application.

[0037] Reference numerals: 100 - base, 110 - chute, 200 - support plate, 210 - first abutting member, 300 - pressing mechanism, 310 - second abutting member, 400 - heating element, 410 - first heating plate, 411 - first through hole, 420 - second heating plate, 421 - second through hole, 500 - coil, 600 - coil bracket, 700 - thermocouple, 800 - acoustic emission device, 900 - rock specimen. Detailed Description of the Embodiment

[0038] The following details the embodiments of the present application. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present application and should not be construed as a limitation of the present application.

[0039] In the description of the present application, it should be understood that for the orientation description, such as the orientation or positional relationship indicated by up, down, front, back, left, right, etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device 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 application.

[0040] In the description of the present application, the meaning of several is more than one, the meaning of multiple is more than two, greater than, less than, exceeding, etc. are understood as not including the present number, and above, below, within, etc. are understood as including the present number. If there is a description of first and second, it is only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features.

[0041] In the description of the present application, unless otherwise clearly defined, words such as setting, installing, connecting, etc. should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above words in the present application in combination with the specific content of the technical solution.

[0042] In the description of the present application, the descriptions with reference to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples" 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 application. 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.

[0043] Since rock itself is a material with tiny cracks inside, during the continuous heat release of high-level radioactive waste, the cracks inside the surrounding rock mass will continuously expand forward in a stable and quasi-static manner, that is, subcritical crack growth. The stability of the rock mass around high-level radioactive waste is closely related to the crack growth of the rock, so it is of great value to study the subcritical crack growth of the surrounding rock mass under the heat release state of high-level radioactive waste. For this reason, an experimental device needs to be designed that can simulate the subcritical crack growth of the rock mass after heating and thereby explore the fracture toughness of the rock mass.

[0044] In response to this, the present application proposes a test device for rock crack propagation parameters under thermal shock. The rock specimen 900 is heated by the heating element 400, and the first heating plate 410 and the second heating plate 420 are used to make the rock specimen 900 heated evenly. Through the misaligned first abutting member 210 and the second abutting member 310, when the pressing mechanism 300 applies pressure, the rock specimen 900 can be subjected to a torsional force, so as to facilitate observing the crack propagation of the rock specimen 900 under the action of external forces.

[0045] In addition, the present application also proposes a test method using the above-mentioned test device for rock crack propagation parameters under thermal shock. The temperature of the rock specimen 900 is increased by the heating element 400 to simulate the heating of the rock in a high-radiation environment, and an external force is applied to the rock specimen 900 by the pressing mechanism 300 to complete the double torsion experiment. Heating and pressurization can be carried out simultaneously, so as to be closer to the real situation of the rock in a high-radiation environment.

[0046] Referring to Figure 1 , the test device for rock crack propagation parameters under thermal shock in the first aspect embodiment of the present application includes a base 100, a support plate 200, a pressing mechanism 300, a heating element 400, and a coil 500. Among them, the base 100 is used to carry other components, the support plate 200 is used to support the rock specimen 900, the pressing mechanism 300 is used to apply a force to the rock specimen 900 to simulate the external force extrusion situation, the heating element 400 is used to heat the rock specimen 900, and the coil 500 is used to make the heating element 400 generate heat.

[0047] Specifically, the support plate 200 is detachably connected to the base 100, so that different types of support plates 200 can be selected according to the size and shape of the rock specimen 900 for support. In some embodiments, the support plate 200 is fixed to the base 100 by means of bolt connection, plug connection or pin connection. In this embodiment, a chute 110 is formed in the base 100, and the support plate 200 slides into one end of the chute 110 to realize the connection between the support plate 200 and the base 100. Refer to Figure 2 , a first abutting member 210 is provided at the end of the support plate 200 for contacting the rock specimen 900 and supporting the rock specimen 900.

[0048] Refer to Figure 3 , the pressing mechanism 300 can be telescopic and a second abutting member 310 is provided at the end. The second abutting member 310 is used for contacting the rock specimen 900 and applying a force thereto.

[0049] Refer to Figure 4 , the heating member 400 includes a first heating plate 410 and a second heating plate 420 which are connected to each other. A heating space is reserved between the first heating plate 410 and the second heating plate 420 to accommodate the rock specimen 900. The first heating plate 410 is provided with a first through hole 411 for the first abutting member 210 to pass through, and the second heating plate 420 is provided with a second through hole 421 for the second abutting member 310 to pass through, so that both the first abutting member 210 and the second abutting member 310 can extend into the heating space to contact the rock specimen 900.

[0050] Refer to Figure 5 , the coil 500 surrounds the outside of the heating member 400. The heating member 400 is a metal member. When an alternating current is passed through the coil 500, the coil 500 heats the heating member 400 through electromagnetic induction, so that the rock specimen 900 is heated up.

[0051] Among them, the rock specimen 900 can be placed in the heating space. The first abutting member 210 supports the rock specimen 900, and the pressing mechanism 300 applies a pressure to the rock specimen 900. It should be noted that the first abutting member 210 and the second abutting member 310 are not coaxially arranged. Thus, when the second abutting member 310 applies a pressure to the rock specimen 900, the rock specimen 900 will be subjected to a torsional force, which is convenient for the experimenter to observe the crack propagation of the rock specimen 900 in the torsional state.

[0052] Furthermore, the number of the support plates 200 is at least two, and the number of the first abutting members 210 is at least four, so as to stably support the rock specimen 900.

[0053] Furthermore, each of the first abutting members 210 and the second abutting members 310 is spherical to realize point-surface contact with the rock specimen 900.

[0054] Furthermore, the pressing mechanism 300 is provided with at least two second abutting members 310, and the second abutting members 310 are arranged side by side, so that the pressing mechanism 300 is in stable contact with the rock specimen 900.

[0055] Furthermore, the rock crack propagation parameter testing device under thermal shock of the present invention further includes a coil bracket 600, and the coil 500 is fixed to the base 100 through the coil bracket 600.

[0056] Furthermore, the rock crack propagation parameter testing device under thermal shock of the present invention further includes a thermocouple 700. Refer to Figure 6 , the thermocouple 700 is installed inside the rock specimen 900, and the rock specimen 900 is drilled according to the test requirements. Before the test starts, the thermocouple 700 is inserted into the drilled hole, and the temperature inside the rock specimen 900 can be measured to ensure that the rock specimen 900 is heated completely and prevent the situation where the surface temperature and the internal temperature of the rock specimen 900 are inconsistent.

[0057] Furthermore, the rock crack propagation parameter testing device under thermal shock of the present invention further includes an acoustic emission device 800, which is installed on the surface of the rock specimen 900. The waveguide rod therein abuts against the surface of the rock specimen 900, and the acoustic wave signal is conducted to the acoustic sensor through the waveguide rod to realize acoustic wave detection to accurately detect the crack change of the rock specimen 900.

[0058] A testing method in the second aspect embodiment of the present application is carried out by using the above-mentioned rock crack propagation parameter testing device under thermal shock, and includes the following steps:

[0059] S100. Place the rock specimen 900 into the heating space so that it is supported by the first abutting member 210 on the support plate 200;

[0060] S200. Energize the coil 500, and based on electromagnetic induction, generate eddy currents inside the heating element 400, so that the heating element 400 is heated up, and then heat the rock specimen 900;

[0061] S300. When the rock specimen 900 is heated to a predetermined temperature, start the pressing mechanism 300 so that the second abutting member 310 contacts the rock specimen 900 and applies a force;

[0062] S400. Observe the torsional situation of the rock specimen 900 under high temperature and torsional force, and record the crack propagation situation of the rock specimen 900.

[0063] This testing method is carried out based on the double torsion test principle, and it is beneficial to calculate the fracture toughness and subcritical crack propagation speed at the crack tip from the parameters measured by the double torsion test device.

[0064] Under the double torsion test, the stress intensity factor at the crack tip is calculated as follows:

[0065]

[0066] Where: P is the load applied by the press on the rock specimen 900 through the indenter of the pressing mechanism 300; W m is the length of the torsion arm, i.e., the distance from the indenter action point to the support point; μ is the Poisson's ratio, which varies for different rocks and can be obtained by referring to relevant data; d is the thickness of the rock specimen 900; d n is the thickness of the rock specimen 900 on the crack surface, i.e., the thickness within the middle groove of the rock specimen 900.

[0067] When the load P reaches the critical value P C , that is, the maximum value reached by the pressure during the pre-cracking process, the K I of the specimen will also reach the critical value. At this time, the K I is the fracture toughness K IC of the rock specimen 900:

[0068]

[0069] During the relaxation test, the calculation formula for the subcritical crack growth rate is as follows:

[0070]

[0071] Where: E is the elastic modulus, which varies for different rocks and can be obtained by referring to relevant data; y is the displacement of the loading point along the loading direction, i.e., the distance of descent when the indenter contacts the specimen until 95% of the maximum load.

[0072] Among them, the fracture toughness K IC and the subcritical crack growth rate v are the main parameters describing the subcritical crack growth. According to the parameters measured during the experiment, the changes in the fracture toughness K IC and the subcritical crack growth rate v of the rock at different heating temperatures can be calculated, and the relationship between the subcritical crack growth rate v and the stress intensity factor K I can be established through this test, so as to infer the influence of temperature on the propagation of the rock pressure boundary crack.

[0073] The acoustic emission device 800 can measure parameters such as the internal energy accumulation of the rock specimen 900 and the change in the ring count. Energy can reflect the strength of the specimen under certain conditions. During the test, the smaller the accumulated energy, the more subcritical crack propagation occurs, resulting in more severe specimen damage. The ring count reflects the number of micro-cracks generated in the specimen during the experiment. If there is more subcritical crack propagation, the ring count will be larger. The subcritical crack propagation of the specimen under high-temperature thermal shock can be verified indirectly based on the parameters measured by the acoustic emission device 800. Among them, the opening and closing of the acoustic emission device 800 are synchronized with the start and end of the double torsion test.

[0074] The embodiments of the present application have been described in detail above with reference to the accompanying drawings. However, the present application is not limited to the above embodiments. Various changes can be made within the scope of knowledge possessed by those of ordinary skill in the art without departing from the purpose of the present application. In addition, the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

Claims

1. A device for testing rock crack propagation parameters under thermal shock, characterized in that: include: Base; A support plate, which is detachably connected to the base, and a first abutment member is provided at an end of the support plate; A pressure mechanism, which is retractable and has a second abutment member at its end; The heating element comprises a first heating plate and a second heating plate connected to each other, a heating space is reserved between the first heating plate and the second heating plate, the first heating plate is provided with a first through hole for the first abutting member to pass through, and the second heating plate is provided with a second through hole for the second abutting member to pass through; A coil, which is wrapped around the outside of the heating element, and the coil heats the heating element through electromagnetic induction; Wherein, the rock sample can be placed in the heating space, the first abutment member supports the rock sample, the pressure mechanism applies pressure to the rock sample, and the first abutment member and the second abutment member are not coaxially arranged.

2. The rock crack propagation parameter testing device under thermal shock according to claim 1, characterized in that: The base is provided with a slide groove, and the support plate slides into one end of the slide groove to achieve the connection between the support plate and the base.

3. The rock crack propagation parameter testing device under thermal shock according to claim 2, characterized in that: The number of the supporting plates is at least two, and the number of the first abutting members is at least four.

4. The rock crack propagation parameter testing device under thermal shock according to claim 3 is characterized in that: Each of the first abutment members is spherical in shape to achieve point-to-surface contact with the rock sample.

5. The rock crack propagation parameter testing device under thermal shock according to claim 1, characterized in that: The second abutment member is spherical in shape to achieve point-to-surface contact with the rock sample.

6. The rock crack propagation parameter testing device under thermal shock according to claim 5, characterized in that: The pressure mechanism is provided with at least two second abutment members, and the second abutment members are arranged side by side.

7. The rock crack propagation parameter testing device under thermal shock according to claim 1, characterized in that: The rock crack extension parameter testing device under thermal shock also includes a coil support, and the coil is fixed to the base through the coil support.

8. The device for testing rock crack propagation parameters under thermal shock according to any one of claims 1 to 7, characterized in that: The rock crack propagation parameter testing device under thermal shock also includes a thermocouple, which is installed inside the rock sample.

9. The device for testing rock crack growth parameters under thermal shock according to any one of claims 1 to 7, characterized in that: The rock crack propagation parameter testing device under thermal shock also includes an acoustic emission device, which is installed on the surface of the rock sample.

10. A testing method, using the rock crack growth parameter testing device under thermal shock as claimed in any one of claims 1 to 9, characterized in that: include: Put the rock sample into the heating space so that it is supported by the first abutment member on the support plate; The coil is energized to generate eddy currents inside the heating element based on electromagnetic induction, thereby increasing the temperature of the heating element and further heating the rock sample; When the rock sample is heated to a predetermined temperature, the pressure-applying mechanism is activated so that the second abutment member contacts the rock sample and applies a force; The torsion of the rock sample under high temperature and torsional force is observed, and the crack extension of the rock sample is recorded.

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