Indoor testing device and method for tensile strength of rock under in-situ condition

Abstract

The embodiment of the invention provides an indoor testing device and method for the tensile strength of rock under the in-situ condition, and belongs to the technical field of rock mechanics testing. The experiment assembly structure is arranged in the cavity, the experiment assembly structure comprises a chassis, a lower pressure head, an upper pressure head and a load sensor, the lower pressure head is fixedly connected to the chassis, the upper pressure head is fixedly connected with the load sensor, and axial deformation sensors are arranged on the upper pressure head and the lower pressure head; the confining pressure supercharger is connected with the cavity; the servo control device is connected with the cavity; the hydraulic station is connected with the confining pressure supercharger and the servo control device; the data acquisition system is connected with the axial deformation sensor; and the control and display system is connected with the confining pressure supercharger, the servo control device and the data acquisition system. According to the indoor testing device and method for the tensile strength of the rock under the in-situ condition, provided by the embodiment of the invention, the accuracy of testing the tensile strength of the rock can be improved.

Description

Technical Field

[0001] This application relates to the field of rock mechanics testing technology, and more specifically, to an indoor testing device and method for the tensile strength of rocks under in-situ conditions. Background Technology

[0002] Currently, large-scale engineering construction often involves stress release due to tunnel excavation, leading to localized tensile stress states. Since soil and rock materials have compressive strength far exceeding their tensile strength, this poses potential safety risks to the construction project. Similarly, in oil and gas drilling and production, verifying the stability of the wellbore surrounding rock is a crucial step in ensuring safe and rapid production; in bridge construction, prestressing is applied to ensure that the cement structure is under long-term compressive stress. Therefore, determining the true tensile strength of soil and rock materials under actual working conditions is of great significance for improving the safety of various infrastructure and resource extraction projects.

[0003] However, current methods for obtaining the tensile strength of rocks have significant errors. Summary of the Invention

[0004] The present application provides an indoor testing device and method for the tensile strength of rocks under in-situ conditions, aiming to improve the accuracy of testing the tensile strength of rocks.

[0005] The first aspect of this application provides an indoor testing device for the tensile strength of rock under in-situ conditions, comprising: chamber; An experimental assembly structure is set in the chamber. The experimental assembly structure includes a chassis, a lower pressure head, an upper pressure head, and a load sensor. The lower pressure head is fixedly connected to the chassis, and the upper pressure head is fixedly connected to the load sensor. Axial deformation sensors are provided on the upper pressure head and the lower pressure head. A confining pressure booster is connected to the chamber and is used to inject a confining pressure boosting medium into the chamber. A servo control device, connected to the chamber, is used to apply axial pressure toward the experimental assembly structure; A hydraulic station is connected to the confining pressure booster and the servo control device, and the hydraulic station is used to provide hydraulic power to the confining pressure booster and the servo control device; A data acquisition system is connected to the axial deformation sensor, and the data acquisition system is used to acquire the data information generated by the axial deformation sensor. A control and display system is connected to the confining pressure booster, the servo control device, and the data acquisition system; the control and display system is used to control the confining pressure booster and the servo control device to start or stop operation, and to receive and display the data information.

[0006] Optionally, the testing apparatus further includes: A separator is disposed between the upper pressure head and the sample and between the lower pressure head and the sample. The separator includes a first plate and a second plate disposed around the first plate. The first plate and the second plate enclose a first region and a second region with openings. The first region and the second region are respectively located on both sides of the first plate. The first region is used to surround the end of the sample, and the second region is used to contact the upper pressure head or the lower pressure head.

[0007] Optionally, the volume of the first region is greater than the volume of the second region.

[0008] Optionally, the first plate has an opening that penetrates through the first plate.

[0009] Optionally, the chassis has a fixing groove, the end of the pressing head is located in the fixing groove, and the pressing head and the fixing groove are fixedly connected by threads; The upper pressure head and the load sensor are connected by bolts.

[0010] Optionally, the chassis is provided with multiple signal transmission channels, and the axial deformation sensor is connected to the data acquisition system through the signal transmission channels.

[0011] The second aspect of this application provides an indoor testing method for the tensile strength of rock under in-situ conditions, applied to the indoor testing device for the tensile strength of rock under in-situ conditions as provided in the first aspect of this application. The method includes: The sample is installed between the upper and lower pressure heads of the testing device, so that the chamber of the testing device is lowered from directly above the experimental assembly structure of the testing device and surrounds the experimental assembly structure. The sample is loaded using the confining pressure booster and servo control device of the testing apparatus; Raise the upper pressure head until the sample is destroyed, record the axial load value and the initial loading load value at this time, and obtain the tensile strength of the sample.

[0012] Optionally, in the step of mounting the sample between the upper and lower indenters of the testing apparatus, the testing method further includes: A latex film and a heat shrink tube are sequentially wrapped around the outside of the sample. The two ends of the latex film and the heat shrink tube extend to the positions of the upper pressure head and the lower pressure head, respectively, and the two ends of the latex film and the heat shrink tube are sealed to the upper pressure head and the lower pressure head, respectively, using sealing rings.

[0013] Beneficial effects: This application provides an indoor testing device and method for the tensile strength of rock under in-situ conditions. The testing device includes a chamber, an experimental assembly structure, a confining pressure booster, a servo control device, a hydraulic station, a data acquisition system, and a control and display system. The experimental assembly structure can fix the sample in the chamber. The confining pressure booster and servo control device can apply radial and axial loads to the sample, respectively. The data acquisition system collects relevant data, and the control and display system controls the experimental devices and displays the data. This application utilizes standard cylindrical specimens, a compression testing machine, and a few simple components to conduct experimental assembly and testing of the tensile strength of rock under in-situ (compacted) conditions. Combined with rock mechanics theory and methods, it simultaneously obtains the tensile strength of rock under compacted conditions and its equivalent uniaxial tensile strength, providing experimental data support for engineering stability verification. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the structure of an indoor testing device for the tensile strength of rock under in-situ conditions, according to an embodiment of this application. Figure 2 This is a schematic diagram of the experimental assembly structure in an indoor testing device for the tensile strength of rock under in-situ conditions, as proposed in an embodiment of this application. Figure 3 This is a schematic diagram of the structure of the indenter in an indoor testing device for the tensile strength of rock under in-situ conditions, according to an embodiment of this application. Figure 4 This is another structural schematic diagram of the indenter in an indoor testing device for the tensile strength of rock under in-situ conditions, as proposed in one embodiment of this application; Figure 5 This is a schematic diagram of the upper indenter structure in an indoor testing device for the tensile strength of rock under in-situ conditions, as proposed in an embodiment of this application. Figure 6This is another structural schematic diagram of the upper indenter in an indoor testing device for the tensile strength of rock under in-situ conditions, as proposed in one embodiment of this application; Figure 7 This is a schematic diagram of the structure of the separator pad in an indoor testing device for the tensile strength of rock under in-situ conditions, according to an embodiment of this application. Figure 8 This is another structural schematic diagram of the separator pad in an indoor testing device for the tensile strength of rock under in-situ conditions, as proposed in one embodiment of this application; Figure 9 This is a schematic diagram of the installation chamber in an indoor testing method for the tensile strength of rock under in-situ conditions, as proposed in an embodiment of this application. Figure 10 This is a schematic diagram of the method for determining the equivalent uniaxial tensile strength of rock in an indoor test method for the tensile strength of rock under in-situ conditions, as proposed in an embodiment of this application.

[0016] Explanation of reference numerals in the attached drawings: 1. Chamber; 2. Experimental assembly structure; 21. Chassis; 211. Signal transmission channel; 22. Lower pressure head; 23. Upper pressure head; 231. Coarse thread hole; 24. Load sensor; 25. Axial deformation sensor; 26. Separator; 261. First plate; 262. Second plate; 263. Opening; 27. Sensor fixing disc limiting groove; 28. Fluorine sealing ring limiting groove; 3. Confining pressure booster; 4. Servo control device; 5. Hydraulic station; 51. Cooling circulation device; 6. Data acquisition system; 7. Control and display system; 8. Sample; A1. First area; A2. Second area. Detailed Implementation

[0017] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0018] In related technologies, there are two main categories of laboratory testing methods for obtaining the tensile strength of rocks: direct tensile testing and indirect tensile testing. The direct tensile testing method involves processing the material into a shape that is easy to clamp (such as dumbbell or dog bone shape), or by gluing it together, and then conducting a direct tensile test using a tensile testing machine. This method is generally used for tensile testing of metallic materials.

[0019] Indirect tensile testing methods, most commonly the Brazilian test, involve preparing the test material into sheet-like samples with a height-to-diameter ratio of 0.25–0.75. Using a clamp such as two semi-circular (or planar) sections, the material is subjected to indirect tension in the transverse direction under vertical compression, ultimately resulting in brittle failure along the loading direction. Other methods include hydrostatic fracturing, three-point bending, four-point bending, and modified tensile testing. However, the Brazilian test method is widely used in laboratory testing of the tensile strength of geotechnical materials due to its simple sample preparation and high efficiency.

[0020] However, direct stretching methods have inherent drawbacks for rock-like materials: because rocks are more brittle and less ductile than metals, it is more difficult to process them into dog-bone-shaped samples. Furthermore, the bond-stretching method is highly susceptible to uneven stress distribution due to the quality of the bond, leading to premature sample failure.

[0021] Because the hydraulic fracturing method involves axisymmetric stress on the system, the final cracking of the sample is greatly affected by the homogeneity of the sample itself, resulting in strong randomness. In contrast, the three-point bending method and the four-point bending method involve the coupling of local tensile and compressive stresses in the system, and the sample starts to break from a single point, resulting in a large error.

[0022] While the Brazilian splitting test is simpler in sample preparation and operation, the rock sample is under-compacted during loading. This may have little impact on dense rocks such as shale and rocks at shallow depths, but for rocks with higher porosity such as sandstone, the tensile strength under zero confining pressure differs from the tensile strength at depths of several thousand meters. Therefore, the tensile strength of rocks obtained through conventional Brazilian splitting tests is not representative.

[0023] In view of this, this application proposes an indoor testing device and method for the tensile strength of rocks under in-situ conditions, aiming to improve the accuracy of testing the tensile strength of rocks.

[0024] Reference Figure 1 As shown in the embodiment of this application, an indoor testing device for the tensile strength of rock under in-situ conditions is disclosed. The testing device includes a chamber 1, an experimental assembly structure 2, a confining pressure booster 3, a servo control device 4, a hydraulic station 5, a data acquisition system 6, and a control and display system 7.

[0025] Specifically, chamber 1 is used to provide a closed environment for the entire experiment, and during the experiment, chamber 1 is filled with dimethyl silicone oil as a medium to increase the confining pressure.

[0026] Reference Figure 1 and Figure 2As shown, during the experiment, the experimental assembly structure 2 is located inside chamber 1. The experimental assembly structure 2 includes a chassis 21, a lower pressure head 22, an upper pressure head 23, and a load sensor 24. The lower pressure head 22 is fixedly connected to the chassis 21, and the upper pressure head 23 is fixedly connected to the load sensor 24. Axial deformers are installed on both the upper and lower pressure heads 22. It can be understood that before the experiment, the sample 8 can be fixed outside chamber 1 between the upper and lower pressure heads 23 and 22, and then the experimental assembly structure 2 with the sample 8 installed can be inserted into chamber 1.

[0027] In this embodiment of the application, a fixing groove is provided on the chassis 21, the end of the pressing head 22 is located in the fixing groove, and the pressing head 22 and the fixing groove are fixedly connected by threads. That is, the inner sidewall of the fixing groove is provided with connecting threads, and the end of the pressing head 22 is provided with mating threads, so that the fixed connection between the pressing head 22 and the chassis 21 can be realized.

[0028] Reference Figure 2 and Figure 6 As shown, the top of the upper pressure head 23 and the load sensor 24 have the same coarse-pitch threaded hole 231. The upper pressure head 23 and the load sensor 24 are fixedly connected through the coarse-pitch threaded hole 231 on the top of the upper pressure head 23 and the load sensor 24. By directly connecting the upper pressure head 23 and the load sensor 24 with bolts, it can be ensured that the hydraulic pressure only acts on the sample 8 from the side, and that the axial stress is less than the lateral stress.

[0029] Reference Figure 3 , Figure 4 , Figure 5 and Figure 6 As shown, sensor fixing plate limiting grooves and fluorinated sealing ring limiting grooves 28 are provided at the end of the upper pressure head 23 away from the load sensor 24 and at the end of the lower pressure head 22 away from the chassis 21, respectively. These grooves are arranged circumferentially along the upper pressure head 23 and the lower pressure head 22. The sensor fixing plate limiting groove is used to fix the fixing disc of the axial deformation sensor, and the fluorinated sealing ring limiting groove 28 is used to fix the sealing ring. Furthermore, the axial deformation of sample 8 can be calculated by the change in the distance between the two fixing discs on the upper pressure head 23 and the lower pressure head 22.

[0030] Meanwhile, it is understandable that a latex film and heat shrink tubing are typically wrapped around sample 8 in sequence. The ends of the latex film and heat shrink tubing extend to the upper pressure head 23 and lower pressure head 22, respectively, and are sealed to the upper pressure head 23 and lower pressure head 22 using sealing rings. The latex film has good extensibility, resulting in a better seal when in contact with the fluororubber ring; the heat shrink tubing is made of FEP (Fluorinated ethylene propylene copolymer), which has strong pressure resistance and will not be punctured during sample 8 deformation.

[0031] Reference Figure 2 , Figure 7 and Figure 8 As shown in the embodiment of this application, the testing device includes a separator 26 disposed between the upper pressure head 23 and the sample 8, and a separator 26 disposed between the lower pressure head 22 and the sample 8.

[0032] Specifically, the separator 26 includes a first plate 261 and a second plate 262 surrounding the first plate 261. The separator 26 is made of high-strength titanium alloy to ensure its strength. It is understood that in this embodiment, the samples 8 are cylindrical, therefore the first plate 261 is circular. Furthermore, the first plate 261 and the second plate 262 enclose a first region A1 and a second region A2 with openings, respectively located on opposite sides of the first plate 261. When the sample 8 is installed between the upper pressure head 23 and the lower pressure head 22, the end of the sample 8 is located within the first region A1 of the separator 26, while the end of the upper pressure head 23 / lower pressure head 22 is located within the second region A2 of the separator 26. To ensure that the separator 26 can completely surround the end of the sample 8, in this embodiment, the volume of the first region A1 is larger than the volume of the second region A2.

[0033] The spacer 26 can be used to limit the range of confining pressure, ensuring that the confining pressure acts only laterally on the central region of sample 8. The spacer 26 can also ensure that the "step" produced by the heat shrink tubing after shrinkage is not obvious.

[0034] Reference Figure 7 and Figure 8 As shown, an opening 263 is provided on the first plate 261. The opening 263 is located at the center of the first plate 261 and extends through the first plate 261. The diameter of the opening 263 can be about 6 mm. When the sample 8 is stuck in the separator 26 due to excessive deformation, a tool such as a metal rod can be inserted into the opening 263 to push the sample 8 out of the first area A1 of the separator 26.

[0035] Reference Figure 1As shown, both the confining pressure booster 3 and the servo control device 4 are connected to the chamber 1. The confining pressure booster 3 is used to inject confining pressure boosting medium into the chamber 1, and the servo control device 4 is used to apply axial pressure towards the experimental assembly structure 2. The hydraulic station 5 is connected to the confining pressure booster 3 and the servo control device 4, and the hydraulic station 5 is used to provide hydraulic power to the confining pressure booster 3 and the servo control device 4. The testing device also includes a cooling circulation device 51 connected to the hydraulic station 5. The cooling circulation device 51 can use liquid cooling to circulate and cool the hydraulic station.

[0036] Reference Figure 1 As shown, the data acquisition system 6 is connected to the axial deformation sensor 25, and the data acquisition system 6 is used to acquire the data information generated by the axial deformation sensor 25. Specifically, multiple signal transmission channels 211 (such as...) are provided on the chassis 21. Figure 2 The axial deformation sensor 25 is connected to the data acquisition system 6 through the signal transmission channel 211, and the data acquisition system 6 can save all the data generated when the system is powered off.

[0037] Reference Figure 1 As shown, the control and display system 7 is connected to the confining pressure booster 3, the servo control device 4, and the data acquisition system 6. Specifically, the experimenter can use the control and display system 7 to issue operating commands to the confining pressure booster 3 and the servo control device 4 (the confining pressure booster 3, the servo control device 4, and the data acquisition system 6 are connected) to start or stop the confining pressure booster 3 and the servo control device 4; simultaneously, the data acquisition system 6 transmits the collected data information to the control and display system 7, which can then display this data information.

[0038] In practical applications, the data acquisition system 6 can be a chip connected to a computer, and the data acquisition system 6 can convert the acquired analog signals into digital signals for output. The control and display system 7 can be a computer, and the computer runs relevant programs for controlling the confining pressure booster 3 and the servo control device 4, and provides a corresponding interactive interface for experimental personnel to use.

[0039] Based on the testing apparatus provided in the embodiments of this application, the embodiments of this application also provide an indoor testing method for the tensile strength of rock under in-situ conditions, the method comprising: Step 101: Install the sample 8 between the upper pressure head 23 and the lower pressure head 22 of the test device, so that the chamber 1 of the test device is lowered from directly above the experimental assembly structure 2 of the test device and surrounds the experimental assembly structure 2.

[0040] Specifically, during a conventional triaxial compression test, the upper and lower pressure heads 22, the rock, and the sensor are first assembled externally, then pushed in via a slide rail, and finally the high-pressure sealed chamber 1 is lowered. During the experiment, the confining pressure intensifier 3 is controlled to increase the confining pressure at a constant rate. Then, the axial load is applied by controlling the axial servo controller while ensuring a constant strain rate in the sample 8 until the sample 8 fails. Under this installation method, since the confining pressure acts on the rock from both the axial and vertical directions, the total stress in the vertical direction is always no less than the radial stress.

[0041] This application involves testing the tensile strength of rock, therefore it is necessary to ensure that the confining pressure only acts on the side of sample 8 (i.e., sample 8 is not subjected to axial force). Consequently, the chamber 1 of the testing device needs to be lowered directly above the experimental assembly structure 2 of the testing device. Figure 9 As shown. Simultaneously, it must be ensured that all contact in the vertical direction is solid-to-solid, meaning that hydraulic pressure will not act in the vertical direction.

[0042] In step 101, the test method further includes: A latex film and a heat shrink tube are wrapped around the sample 8 in sequence. The two ends of the latex film and the heat shrink tube extend to the upper pressure head 23 and the lower pressure head 22, respectively. The two ends of the latex film and the heat shrink tube are sealed to the upper pressure head 23 and the lower pressure head 22 by a sealing ring.

[0043] Step 102: Load sample 8 using the confining pressure booster 3 and servo control device 4 of the testing device.

[0044] Step 103: Raise the upper pressure head 23 until sample 8 is damaged. Record the axial load value and the initial loading load value at this time to obtain the tensile strength of sample 8.

[0045] Specifically, in conducting the tensile strength test on the rock, sample 8 needs to be subjected to hydrostatic loading, i.e., simultaneous axial and radial loading, to recreate the compressive condition of the rock under in-situ (i.e., compacted) conditions. Then, by raising the indenter 23, it is equivalent to superimposing a tensile stress on sample 8 in the vertical direction, and at this point, the vertical stress must be less than the system confining pressure. After raising the indenter until the axial load decreases to a certain level, sample 8 fails. The axial load value at this point, along with the initial loading load value, is recorded. It can be understood that the difference between the axial load value and the initial loading load value is the in-situ tensile strength of rock sample 8 under the current confining pressure (degree of compaction).

[0046] Furthermore, after conversion, the corresponding data can be plotted on a plane, where , , I1 refers to the first invariant of the stress tensor, and J2 refers to the second invariant of the deviatoric stress tensor. Then, by using multiple sets of data points, the intersection of the extended line of the two-dimensional yield surface with the uniaxial tensile trend line represents the equivalent tensile strength of the rock, such as... Figure 10As shown.

[0047] The tensile strength of rock under compacted conditions can be obtained using the testing apparatus and method provided in the embodiments of this application. Furthermore, this application only requires a cylindrical specimen and a conventional compression testing machine to conduct the experiment. By improving the instrument, it is possible to achieve a stress state where the axial pressure is less than the confining pressure. By adding a separator, the problem of uneven stress distribution at the ends of the cylindrical specimen is solved, while the lateral stress distribution is concentrated. Combined with the yield criterion, by selecting an appropriate yield criterion and extrapolating the result data points, an equivalent uniaxial tensile strength can be obtained. This establishes an indoor testing method for measuring the tensile strength of rock under in-situ (compacted) conditions, providing scientific parameter support for wellbore stability calculations and the optimization of fracturing construction parameters.

[0048] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0049] It should also be noted that, in this document, the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations, nor should they be construed as indicating or implying relative importance. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements, but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. In the absence of further restrictions, an element defined by the phrase "includes a..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes the element.

[0050] The technical solutions provided in this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand this application, and the content of this specification should not be construed as a limitation of this application. Furthermore, for those skilled in the art, there will be different forms of changes in the specific implementation methods and application scope based on this application. It is neither necessary nor possible to exhaustively list all implementation methods here, and obvious changes or modifications derived therefrom are still within the protection scope of this application.

Claims

1. An indoor testing device for the tensile strength of rock under in-situ conditions, characterized in that, include: Chamber; An experimental assembly structure is set in the chamber. The experimental assembly structure includes a chassis, a lower pressure head, an upper pressure head, and a load sensor. The lower pressure head is fixedly connected to the chassis, and the upper pressure head is fixedly connected to the load sensor. Axial deformation sensors are provided on the upper pressure head and the lower pressure head. A confining pressure booster is connected to the chamber and is used to inject a confining pressure boosting medium into the chamber. A servo control device, connected to the chamber, is used to apply axial pressure toward the experimental assembly structure; A hydraulic station is connected to the confining pressure booster and the servo control device, and the hydraulic station is used to provide hydraulic power to the confining pressure booster and the servo control device; A data acquisition system is connected to the axial deformation sensor, and the data acquisition system is used to acquire the data information generated by the axial deformation sensor. A control and display system is connected to the confining pressure booster, the servo control device, and the data acquisition system; the control and display system is used to control the confining pressure booster and the servo control device to start or stop operation, and to receive and display the data information.

2. The indoor testing device for the tensile strength of rock under in-situ conditions according to claim 1, characterized in that, The testing apparatus also includes: A separator is disposed between the upper pressure head and the sample and between the lower pressure head and the sample. The separator includes a first plate and a second plate disposed around the first plate. The first plate and the second plate enclose a first region and a second region with openings. The first region and the second region are respectively located on both sides of the first plate. The first region is used to surround the end of the sample, and the second region is used to contact the upper pressure head or the lower pressure head.

3. The indoor testing device for the tensile strength of rock under in-situ conditions according to claim 2, characterized in that: The volume of the first region is greater than the volume of the second region.

4. The indoor testing device for the tensile strength of rock under in-situ conditions according to claim 2, characterized in that: The first plate has an opening that penetrates through the first plate.

5. The indoor testing device for the tensile strength of rock under in-situ conditions according to claim 1, characterized in that: The chassis has a fixing groove, the end of the pressing head is located in the fixing groove, and the pressing head and the fixing groove are fixedly connected by threads. The upper pressure head and the load sensor are connected by bolts.

6. The indoor testing device for the tensile strength of rock under in-situ conditions according to claim 1, characterized in that: The chassis is provided with multiple signal transmission channels, and the axial deformation sensor is connected to the data acquisition system through the signal transmission channels.

7. A method for indoor testing of the tensile strength of rock under in-situ conditions, applied to any of the indoor testing devices for the tensile strength of rock under in-situ conditions as described in claims 1-6, characterized in that, The method includes: The sample is installed between the upper and lower pressure heads of the testing device, so that the chamber of the testing device is lowered from directly above the experimental assembly structure of the testing device and surrounds the experimental assembly structure. The sample is loaded using the confining pressure booster and servo control device of the testing apparatus; Raise the upper pressure head until the sample is destroyed, record the axial load value and the initial loading load value at this time, and obtain the tensile strength of the sample.

8. The indoor testing method for the tensile strength of rock under in-situ conditions according to claim 7, characterized in that, In the step of mounting the sample between the upper and lower pressure heads of the testing device, the testing method further includes: A latex film and a heat shrink tube are sequentially wrapped around the outside of the sample. The two ends of the latex film and the heat shrink tube extend to the positions of the upper pressure head and the lower pressure head, respectively, and the two ends of the latex film and the heat shrink tube are sealed to the upper pressure head and the lower pressure head, respectively, using sealing rings.

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