Indoor geostress testing equipment and method based on optical strain measurement

Abstract

The application provides an indoor geostress test device and method based on optical strain measurement, the test device comprising a stress simulation device capable of simulating a real three-dimensional geostress environment of a test rock mass as much as possible; and a drilling device having a hollow drill bit for drilling an optical strain measurement device installed in the test rock mass, wherein a drilling hole is coaxially arranged with the hollow drill bit. Thus, the method can more accurately simulate a real three-dimensional geostress environment by applying pressure to the test rock mass from multiple directions through multiple hydraulic loading columns, and can record changes in speckle patterns in a speckle coating in real time and continuously by using the optical strain measurement device, obtain hole wall strain data, and then convert the strain data into stress by applying an elastic theory formula to accurately calculate the stress state of the test rock mass.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rock mass mechanics test equipment, and particularly relates to an indoor in-situ stress test equipment and method based on optical strain measurement. BACKGROUND

[0002] At present, in deep engineering, the in-situ stress environment is more complex and changeable than that in shallow part. Dynamic disasters caused by in-situ stress seriously threaten the life and property safety of mining enterprises. Therefore, the measurement of in-situ stress has become an important research content in the fields of geotechnical engineering and mining. With the continuous development of in-situ stress measurement technology, the stress relief method is a relatively common measurement method at present. Through the stress relief method, more accurate in-situ stress related values can be obtained. However, due to the structure and principle of the hollow pack strain gauge used in the test process, there are still some errors in the obtained in-situ stress results. In addition, the stress applied to the test rock mass during the test is mostly biaxial loading. In the two-dimensional stress environment, the real three-dimensional in-situ stress environment cannot be simulated continuously when drilling and punching for stress relief. This will undoubtedly lead to errors in the related values of in-situ stress obtained. This error may affect the safety of engineering design and construction, as well as the stability of geotechnical engineering. Therefore, it is urgent to design a test equipment to make up for the defects of the current research. SUMMARY

[0003] Therefore, the present application aims to provide an indoor in-situ stress test equipment and method based on optical strain measurement, which can improve the accuracy of the related data obtained during the test process, so as to at least partially solve the problems in the related art.

[0004] In order to achieve the above purpose, the present application provides an indoor in-situ stress test equipment based on optical strain measurement, which comprises:

[0005] The stress simulation device comprises a bearing table and a counterforce assembly installed on the bearing table. The bearing table is provided with a placement position for placing a test rock mass. The test rock mass is provided with a mounting hole for installing an optical strain measurement device. The counterforce assembly is provided with an opening for penetrating a hydraulic loading column at each of the two ends arranged oppositely in a first direction. The end of the counterforce assembly away from the placement position is provided with the opening for penetrating the hydraulic loading column. The two ends arranged oppositely in a second direction of the counterforce assembly are respectively provided with a drilling hole and the opening for penetrating the hydraulic loading column.

[0006] The relief drilling device has a hollow drill bit for drilling the optical strain measurement device installed in the mounting hole. The mounting hole, the drilling hole and the hollow drill bit are coaxially arranged.

[0007] Optionally, the counterforce assembly comprises a counterforce frame and a counterforce plate.

[0008] The counterforce frame is connected to the upper surface of the bearing table at one end and connected to the counterforce plate at the other end, the end of the counterforce plate away from the counterforce frame is connected to the bearing table, the counterforce plate is provided with the drilling hole, and the end face of the counterforce frame away from the drilling hole is provided with the opening.

[0009] Optionally, the counterforce frame comprises a fixed plate provided with the opening and a connecting beam for connecting the fixed plate and the counterforce plate, the bearing table is provided with a first plug-in slot for plugging the fixed plate and a second plug-in slot for plugging the counterforce plate, and the two ends of the bearing table arranged opposite in the second direction are respectively provided with a first threaded hole and a second threaded hole, the fixed plate is provided with a first through hole corresponding to the first threaded hole, and the counterforce plate is provided with a second through hole corresponding to the second threaded hole.

[0010] Optionally, the connecting beam comprises a connecting rod and a mounting member fixed to both ends of the connecting rod.

[0011] The mounting member is provided with a clamping slot and a first perforation for screw rod, and the fixed plate and the counterforce plate are both provided with a second perforation corresponding to the first perforation.

[0012] The number of the connecting beams is two, the two connecting beams are arranged opposite in the first direction, and the two connecting beams are both arranged between the fixed plate and the counterforce plate.

[0013] Optionally, the placement site is configured as an open slot recessed in the upper surface of the bearing table.

[0014] The two ends of the open slot arranged opposite in the second direction are respectively a channel opening and a positioning side wall surface.

[0015] Optionally, it further comprises a first uniform force plate, the number of the first uniform force plates is two, and the two first uniform force plates are arranged at the two ends of the open slot arranged opposite in the first direction.

[0016] The first uniform force plate is fixedly connected with a support plate at one end close to the open slot, and the two side wall surfaces of the open slot arranged opposite in the first direction are both provided with a receiving slot for receiving the support plate.

[0017] The positioning side wall surface and the test rock mass are further provided with a second uniform force plate, and the upper surface of the test rock mass is placed with the third uniform force plate.

[0018] Optionally, it further comprises a moving assembly.

[0019] The moving assembly comprises a sliding table and a base, the sliding table is slidingly connected to the base, and the upper surface of the sliding table is installed with the releasing drilling device.

[0020] The drilling device comprises a mounting frame, a driving motor, a first transmission assembly, a driving rod, a second transmission assembly, a transmission rod, a variable-diameter joint, a core sleeve and the hollow drill bit;

[0021] The output shaft of the driving motor is connected with the driving rod through the first transmission assembly, the driving rod is connected with the transmission rod through the second transmission assembly, one end of the transmission rod away from the second transmission assembly is connected with the variable-diameter joint, the variable-diameter joint is used for connecting the core sleeve, and one end of the core sleeve away from the variable-diameter joint is connected with the hollow drill bit;

[0022] The mounting frame is provided with a bearing seat for fixing the driving rod and the transmission rod, and the mounting frame is further fixedly connected with an extension sleeve for supporting the core sleeve, the inner wall surface of the extension sleeve is provided with a ring sleeve, the core sleeve passes through the ring sleeve, and the connecting part of the core sleeve and the ring sleeve is provided with a bearing.

[0023] Optionally, the first transmission assembly comprises a first belt pulley connected with the output shaft of the driving motor and a second belt pulley mounted on the driving rod, the first belt pulley and the second belt pulley are connected through a belt, and the second transmission assembly is configured as a CVT stepless speed change mechanism.

[0024] Optionally, the optical strain measuring device comprises a mounting rack, a plurality of shooting modules and an illuminating device, the shooting modules and the illuminating device are mounted on the mounting rack, the plurality of shooting modules are arranged at intervals along the length direction of the mounting rack, each shooting module comprises a first mounting plate, a second mounting plate and a micro camera, the first mounting plate and the second mounting plate are partially overlapped and fixedly connected and have an included angle therebetween, the first mounting plate is provided with the micro camera at both ends along the length thereof, the second mounting plate is provided with the micro camera at both ends along the length thereof, and the mounting rack has a plurality of mounting surfaces, and each mounting surface is provided with one shooting module.

[0025] Based on the same inventive concept, the application further provides an indoor ground stress test method based on optical strain measurement, which is suitable for the indoor ground stress test device based on optical strain measurement and comprises the following steps:

[0026] The speckle liquid is applied to the inner wall surface of the mounting hole to form a speckle coating;

[0027] The optical strain measuring device is installed through the mounting hole, so that speckles in the speckle coating are continuously imaged and recorded by the optical strain measuring device, and the obtained images are continuously received by an external image data processing computer;

[0028] The hydraulic loading columns exert a preset stress on the test rock mass according to the preset stress value, so as to simulate the ground stress borne by the rock mass in an actual scene;

[0029] The test rock mass is stress-relieved by the hollow drill bit, and the recorded images are processed by the image data processing computer to obtain strain data;

[0030] The strain data are converted into stress values according to an elastic theory formula, the stress values are compared with the preset stress value, and the stress-relieving effect is evaluated based on the comparison result.

[0031] According to the technical solution, the multiple hydraulic loading columns extend to the inside of the reaction force assembly through the openings provided on the reaction force assembly from multiple directions, and then abut against the test rock mass, so as to simulate the real three-dimensional ground stress environment as much as possible, so that the data measured by the optical strain measuring device installed in the test rock mass are closer to the real data, that is, the optical strain measuring device is installed in the test rock mass to ensure that it can continuously image and record speckles in the speckle coating applied on the hole wall, so as to obtain the corresponding hole wall strain data, the strain data are converted into stress values according to the elastic theory formula, and then the obtained stress values are compared with the pre-applied stress, so as to evaluate the stress-relieving effect; meanwhile, the device can simulate the stress-relieving technology of the engineering site ground stress test in the laboratory, and improve the accuracy of the optical strain measuring device, the simulation calculation results in the laboratory can provide more accurate basis for the on-site geotechnical engineering design, which is helpful for personnel to evaluate and predict the risks that may be caused by the change of ground stress, and improve the safety of construction personnel.

[0032] Other features and advantages of the present disclosure will be described in detail in the following detailed description section. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0034] Figure 1is a structural schematic diagram of the original rock stress relief simulation test equipment provided in the exemplary embodiments of the present disclosure;

[0035] Figure 2 is a front view structural schematic diagram of the stress simulation device provided in the exemplary embodiments of the present disclosure, wherein the connecting beams are not shown;

[0036] Figure 3 is a side view structural schematic diagram of the stress simulation device provided in the exemplary embodiments of the present disclosure, wherein the connecting beams are not shown;

[0037] Figure 4 is a structural schematic diagram of the counterforce assembly and the bearing table provided in the exemplary embodiments of the present disclosure;

[0038] Figure 5 is a structural schematic diagram of the bearing table provided in the exemplary embodiments of the present disclosure, wherein the fixed plate and the counterforce plate are installed;

[0039] Figure 6 is a structural schematic diagram of one angle of the bearing table provided in the exemplary embodiments of the present disclosure;

[0040] Figure 7 is a structural schematic diagram of the bearing table provided in the exemplary embodiments of the present disclosure, wherein the first uniform force plate is installed;

[0041] Figure 8 is a structural schematic diagram of the first uniform force plate provided in the exemplary embodiments of the present disclosure;

[0042] Figure 9 is a structural schematic diagram of the connecting beam provided in the exemplary embodiments of the present disclosure;

[0043] Figure 10 is a structural schematic diagram of another angle of the bearing table provided in the exemplary embodiments of the present disclosure;

[0044] Figure 11 is a structural schematic diagram of the fixed plate provided in the exemplary embodiments of the present disclosure;

[0045] Figure 12 is a structural schematic diagram of the counterforce plate provided in the exemplary embodiments of the present disclosure;

[0046] Figure 13 is a structural schematic diagram of the optical strain measurement device provided in the exemplary embodiments of the present disclosure;

[0047] Figure 14 is a structural schematic diagram of the mounting rack provided in the exemplary embodiments of the present disclosure;

[0048] Figure 15is a flowchart of an indoor geostress test method based on optical strain measurement provided in an exemplary embodiment of the present disclosure.

[0049] Legend of reference signs

[0050] 1-bear platform; 101-first plug-in slot; 102-second plug-in slot; 103-first threaded hole; 104-second threaded hole; 105-open slot; 1051-passage opening; 1052-positioning side wall surface; 1053-receiving groove; 2-counterforce frame; 201-fixed plate; 2011-first through hole; 202-connecting beam; 2021-connecting rod; 2022-mounting member; 20221-clamping groove; 20222-first through hole; 3-counterforce plate; 301-drilling hole; 302-second through hole; 4-drilling releasing device; 401-mounting frame; 402-driving motor; 403-first transmission assembly; 4031-first pulley; 4032-second pulley; 404-driving rod; 405-second transmission assembly; 406-transmission rod; 407-reducer; 408-core sleeve; 409-hollow drill bit; 410-extension sleeve; 411-ring sleeve; 5-second through hole; 6-first uniform force plate; 601-supporting plate; 7-second uniform force plate; 8-third uniform force plate; 9-moving assembly; 901-sliding table; 902-base; 10-test rock mass; 11-hydraulic loading column; 12-optical strain measurement device; 1201-first mounting plate; 1202-second mounting plate; 1203-miniature camera. DETAILED DESCRIPTION

[0051] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to specific examples and drawings.

[0052] It should be noted that, unless otherwise defined, technical terms or scientific terms used in the embodiments of the present application should be understood as their common meanings to those skilled in the art to which the present disclosure pertains. The terms "first", "second" and similar terms used in the present disclosure do not indicate any order, number or importance, but are only used to distinguish different components. The terms "include" or "contain" and similar terms mean that the elements or objects before the terms encompass the elements or objects listed after the terms and their equivalents, without excluding other elements or objects. The terms "connect" or "connected" and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms "upper", "lower", "left", "right" and the like are only used to indicate relative positional relationships, and when the absolute positions of the described objects change, the relative positional relationships can also change accordingly.

[0053] As a method of measuring material strain data, the non-contact digital image measurement technology (DIC) analyzes the deformation of an object by comparing the pixel displacement between two or more images. It is widely used in the performance testing of rock materials, metal materials and various organic materials, and has the advantages of low measurement condition requirement, simple data acquisition, non-contact, high measurement accuracy and full-field measurement. The non-contact feature can avoid the influence of many external factors on the data, and the result is more accurate.

[0054] In underground engineering, the casing hole wall stress relief method is a commonly used in-situ stress measurement technique, and is a method for obtaining relatively accurate in-situ stress data. The main principle is to separate the rock sample from the surrounding rock mass by using a casing hole, and then monitor the strain or displacement response of the relieved part. Then, according to the constitutive relation of the rock (the relationship between the relieved strain or displacement and the far-field stress of the surrounding rock), the in-situ stress can be determined. However, due to the structure and principle of the traditional hollow inclusion strain gauge, there are still some errors in the obtained in-situ stress results.

[0055] Based on this, in the specific embodiments provided in the present disclosure, an indoor in-situ stress test equipment based on optical strain measurement is provided, which refers to Figures 1 to 15As shown, the indoor geostress test equipment based on optical strain measurement includes a stress simulation device and a drilling device 4, wherein the stress simulation device can simulate a more realistic three-dimensional geostress environment for the test rock mass 10, that is, the stress simulation device includes a bearing table 1 and a counterforce assembly installed on the bearing table 1, the bearing table 1 is provided with a placement position for placing the test rock mass 10, the counterforce assembly is provided with openings for the hydraulic loading columns 11 to pass through at two ends arranged oppositely in a first direction, and the two hydraulic loading columns 11 extend to the inside of the counterforce assembly through the openings from opposite sides of the first direction and apply pressure to the test rock mass 10; one end of the counterforce assembly away from the placement position is provided with an opening for the hydraulic loading column 11 to pass through, that is, one hydraulic loading column 11 is provided above the placement position, the hydraulic loading column 11 extends to the inside of the counterforce assembly through the opening and applies pressure to the test rock mass 10 from above the test rock mass 10 towards the placement position, and at this time the placement position gives the test rock mass 10 a counterforce towards the upper side; two ends of the counterforce assembly arranged oppositely in a second direction are respectively provided with a drilling hole 301 and an opening for the hydraulic loading column 11 to pass through, that is, one end of the counterforce assembly towards the drilling device 4 is provided with the drilling hole 301 for the hollow drill bit 409 to extend to the inside of the counterforce assembly, so as to ensure that the hollow drill bit 409 can drill the optical strain measurement device 12 installed in the test rock mass 10, therefore, the end of the counterforce assembly provided with the drilling hole 301 cannot be provided with the hydraulic loading column 11 for applying pressure to the test rock mass 10, and a path for the movement of the hollow drill bit 409 needs to be reserved, and at the same time, the end of the counterforce assembly away from the drilling hole 301 can be provided with an opening for the hydraulic loading column 11 to pass through, as shown in Figure 1 The hydraulic loading column 11 can be understood as applying pressure to the test rock mass 10 from the back thereof, and when the hydraulic loading column 11 located at the back of the test rock mass 10 applies pressure thereto, the counterforce assembly can give the test rock mass 10 an opposite force, based on which, as shown in Figure 1 and Figure 2 As shown, pressure is applied to the test rock mass 10 from above, left, right and back thereof respectively by the four hydraulic loading columns 11, and a counterforce is applied to the test rock mass 10 by the bearing table 1 and the counterforce assembly, so as to achieve the purpose of more realistic simulation of a three-dimensional geostress environment, improve the accuracy of relevant data obtained by measurement, reduce data errors as much as possible, and provide more accurate basis for geotechnical engineering design, and at the same time, the drilling device 4 has the hollow drill bit 409 for drilling the optical strain measurement device 12 installed in the test rock mass 10, that is, the optical strain measurement device 12 is installed in the test rock mass 10, so as to ensure that it can continuously take images of speckles in the speckle coating smeared on the hole wall, so as to obtain corresponding hole wall strain data, convert the strain data into stress by an elastic theory formula, compare the obtained stress quantity with the pre-applied stress, and evaluate the stress relief effect.

[0056] By the above technical scheme, the plurality of hydraulic loading columns 11 extend to the inside of the reaction force assembly through the openings provided on the reaction force assembly from multiple directions, and then abut against the test rock mass 10, so as to simulate the real three-dimensional stress environment as much as possible, so that the data measured by the optical strain measuring device 12 installed in the test rock mass 10 is closer to the real data, that is, the optical strain measuring device 12 is installed in the test rock mass 10, so as to ensure that it can continuously image and record the speckles in the speckle coating smeared on the hole wall, and then obtain the corresponding strain data, and then convert the strain data into stress through the elastic theory formula, and then compare the obtained stress quantity with the pre-applied stress, so as to evaluate the stress relief effect; at the same time, the device can simulate the stress relief technology of the engineering site stress test in the laboratory, and improve the accuracy of the optical strain measuring device 12, and according to the simulation calculation result in the laboratory, more accurate basis can be provided for the on-site geotechnical engineering design, which is helpful for personnel to evaluate and predict the risks that may be caused by the change of ground stress, and improves the safety of construction personnel.

[0057] For example, the first direction can be understood as the length direction of the bearing table 1, and the second direction can be understood as the width direction of the bearing table 1.

[0058] In some embodiments, with reference to Figures 4 to 10 As shown, the reaction force assembly includes a reaction force frame 2 and a reaction force plate 3, wherein one end of the reaction force frame 2 is connected to the upper surface of the bearing table 1, and the other end is connected to the reaction force plate 3, the end of the reaction force plate 3 away from the reaction force frame 2 is connected to the bearing table 1, the reaction force plate 3 is provided with a drilling hole 301, and the end face of the reaction force frame 2 away from the drilling hole 301 is provided with an opening, that is, when the hydraulic loading column 11 located at the back of the test rock mass 10 applies pressure to the test rock mass 10, the hydraulic loading column 11 extends to the inside of the reaction force frame 2 through the opening provided on the reaction force frame 2, and then abuts against the test rock mass 10, so that the reaction force plate 3 and the test rock mass 10 abut against each other and apply a reaction force to the test rock mass 10.

[0059] In some embodiments, with reference to Figures 4 to 10 As shown, the reaction force frame 2 includes two parts, namely a fixed plate 201 provided with an opening and a connecting beam 202 used for connecting the fixed plate 201 and the reaction force plate 3, and the fixed plate 201 and the connecting beam 202 are detachably connected, so as to facilitate personnel to classify and store the fixed plate 201 and the connecting beam 202, when the measurement operation is not needed, the reaction force frame 2 can be detached from the bearing table 1 and the fixed plate 201 and the connecting beam 202 are separated, so that the storage space can be significantly saved, especially in the case of limited laboratory space;

[0060] In some embodiments, with reference to Figures 4 to 10As shown, the bearing table 1 is provided with a first insertion slot 101 for inserting the fixed plate 201 and a second insertion slot 102 for inserting the counterforce plate 3. The fixed plate 201 and the counterforce plate 3 are installed on the bearing table 1 by insertion. In order to ensure that the fixed plate 201 and the counterforce plate 3 can be firmly installed on the bearing table 1, the bearing table 1 is provided with a first threaded hole 103 and a second threaded hole 104 at two ends arranged in the second direction, respectively. The fixed plate 201 is provided with a first through hole 2011 corresponding to the first threaded hole 103. The counterforce plate 3 is provided with a second through hole 302 corresponding to the second threaded hole 104. That is, when the fixed plate 201 is inserted into the first insertion slot 101, the first through hole 2011 provided on the fixed plate 201 is coaxial with the first threaded hole 103. At this time, the fixed plate 201 is fixed by a bolt, so that the fixed plate 201 is firmly connected to the bearing table 1. When the counterforce plate 3 is inserted into the second insertion slot 102, the second through hole 302 provided on the counterforce plate 3 is coaxial with the second threaded hole 104. At this time, the counterforce plate 3 is fixed by a bolt, so that the counterforce plate 3 is firmly connected to the bearing table 1.

[0061] In some embodiments not shown, the connecting beam 202 includes a connecting column provided between the fixed plate 201 and the counterforce plate 3 and provided with external threads on the outer wall surface for threadedly connecting nuts. The fixed plate 201 and the counterforce plate 3 are each provided with a through hole for the connecting column to pass through. Each connecting column is connected with four nuts, two nuts as a group for clamping and fixing the fixed plate 201 and the counterforce plate 3. In order to ensure the stability of the connection of the nuts, a gasket can be sleeved on the connecting column. Each nut corresponds to at least one gasket.

[0062] In some embodiments, referring to Figures 4 to 12 As shown, the connecting beam 202 includes a connecting rod 2021 and a mounting piece 2022 fixed to both ends of the connecting rod 2021. The mounting piece 2022 is provided with a clamping slot 20221 and a first through hole 20222 for a screw rod to pass through. The fixed plate 201 and the counterforce plate 3 are each provided with a second through hole 5 corresponding to the first through hole 20222. That is, during installation, the two mounting pieces 2022 at both ends of the connecting rod 2021 are aligned with the fixed plate 201 and the counterforce plate 3, respectively. Then, the clamping slot 20221 on the mounting piece 2022 can be inserted into the fixed plate 201 and the counterforce plate 3. After insertion, the second through hole 5 on the fixed plate 201 and the second through hole 5 on the counterforce plate 3 are coaxial with the first through hole 20222 of the corresponding mounting piece 2022, respectively. Then, the screw rod is passed through and fixed by a nut.

[0063] In some embodiments, the clamping groove 20221 can effectively increase the contact area of the mounting member 2022 with the fixed plate 201 and the counterforce plate 3, thereby effectively increasing the connection strength between the connecting beam 202 and the fixed plate 201 and the counterforce plate 3, so that the counterforce plate 3 can better give the test rock mass 10 a counterforce, ensuring that a more realistic three-dimensional stress environment simulation can be given to the test rock mass 10.

[0064] In some embodiments, the number of connecting beams 202 is two, the two connecting beams 202 are oppositely arranged along the first direction, and the two connecting beams 202 are arranged between the fixed plate 201 and the counterforce plate 3. The fixed plate 201, the counterforce plate 3 and the two connecting beams 202 enclose an opening, so that the hydraulic loading column 11 located above the test rock mass 10 can extend from the opening to the inside of the counterforce assembly to exert pressure on the test rock mass 10.

[0065] In some embodiments, referring to Figure 6 and Figure 10 , the placement site is configured as an open slot 105 recessed on the upper surface of the bearing table 1. The two ends of the open slot 105 oppositely arranged along the second direction are respectively a passage opening 1051 and a positioning side wall surface 1052. The passage opening 1051 is arranged to facilitate personnel to carry the test rock mass 10 into the open slot 105. In order to ensure that the test rock mass 10 can be better subjected to pressure by the plurality of hydraulic loading columns 11, the test rock mass 10 placed on the upper surface of the open slot 105 needs to be in a suitable position. In order to improve the work efficiency when placing the test rock mass 10 and improve the placement accuracy, the positioning side wall surface 1052 is used to position the test rock mass 10, that is, the test rock mass 10 can be directly abutted against the positioning side wall surface 1052 during the process of carrying the test rock mass 10. In order to further improve the placement accuracy, two marking lines can be marked on the positioning side wall surface 1052 according to the size of the test rock mass 10. When placing, the test rock mass 10 should be between the two marking lines.

[0066] In some embodiments, referring to Figure 7 and Figure 8 , in order to make the hydraulic loading column 11 more uniformly exert pressure on the test rock mass 10, the first force equalizing plate 6 can be used, that is, the number of the first force equalizing plate 6 is two, and the two first force equalizing plates 6 are arranged at the two ends of the open slot 105 oppositely arranged along the first direction. The two hydraulic loading columns 11 oppositely arranged along the first direction of the test rock mass 10 are respectively abutted against the test rock mass 10 through the corresponding first force equalizing plate 6. The first force equalizing plate 6 can uniformly transmit the force exerted by the hydraulic loading column 11 to the entire contact surface of the test rock mass 10, thereby avoiding local stress concentration.

[0067] In some embodiments, referring to Figure 7 andFigure 8 As shown, the first force equalizing plate 6 can effectively transmit the force applied by the hydraulic loading column 11 to the entire contact surface of the test rock mass 10, thereby improving the accuracy of the data tested by the optical strain measuring device 12, making the test result more reliable. At the same time, the first force equalizing plate 6 can also protect the test rock mass 10 from direct high-pressure impact and reduce the damage to the rock mass caused by uneven pressure. Therefore, before the three-dimensional stress environment simulation is performed by the hydraulic loading column 11, the first force equalizing plate 6 needs to be placed in the appropriate position to ensure that it can uniformly transmit the force applied by the hydraulic loading column 11 to the entire contact surface of the test rock mass 10, avoiding affecting the accuracy of the test result. Based on this, in order to save manpower and improve the safety of operation, the first force equalizing plate 6 is fixedly connected with a support plate 601 near one end of the open groove 105. The included angle between the connection part of the support plate 601 and the first force equalizing plate 6 is 90°. The first force equalizing plate 6 can be erected on the upper surface of the open groove 105 through the support plate 601. Before the test rock mass 10 is subjected to pressure by the hydraulic loading column 11, the position of the first force equalizing plate 6 can be adjusted by adjusting the placement position of the support plate 601. The correct placement position can ensure that the pressure applied to the test rock mass 10 is uniformly distributed, making the measured data more reliable and facilitating subsequent data interpretation and analysis, thereby improving the accuracy of the test result.

[0068] In some embodiments, with reference to Figures 6 to 8 As shown, the two side walls of the open groove 105 arranged opposite in the first direction are each provided with a receiving groove 1053 for receiving the support plate 601. That is, before the three-dimensional stress environment simulation is performed by the hydraulic loading column 11, the first force equalizing plate 6 can be arranged on the upper surface of the open groove 105. In order to enable the first force equalizing plate 6 to be stably placed in the open groove 105, the support plate 601 fixedly connected with the first force equalizing plate 6 can be inserted into the receiving groove 1053 to limit the support plate 601, so that the first force equalizing plate 6 is in an erected state and placed on the upper surface of the open groove 105.

[0069] In some embodiments, with reference to Figure 2 and Figure 3 As shown, the second force equalizing plate 7 and the third force equalizing plate 8 are also provided in the present application. The second force equalizing plate 7 is arranged between the positioning side wall 1052 and the test rock mass 10. The second force equalizing plate 7 corresponds to the hydraulic loading column 11 located at the back of the test rock mass 10, so that the hydraulic loading column 11 located at the back of the test rock mass 10 can more uniformly apply pressure to the test rock mass 10. The third force equalizing plate 8 is placed on the upper surface of the test rock mass 10, thereby corresponding to the hydraulic loading column 11 located above the test rock mass 10. The third force equalizing plate 8 enables the hydraulic loading column 11 located above the test rock mass 10 to more uniformly apply pressure to the test rock mass 10.

[0070] In some implementations, reference Figure 1 As shown, it also includes a moving component 9, which includes a slide 901 and a base 902. The slide 901 is slidably connected to the base 902. A release drilling device 4 is installed on the upper surface of the slide 901. That is, the slide 901 can drive the release drilling device 4 to move along the length direction of the base 902 so that the hollow drill bit 409 can extend through the drilling hole 301 to the inside of the reaction component and then contact the test rock mass 10, thereby drilling down the optical strain gauge 12 installed in the test rock mass 10.

[0071] In some embodiments not shown, a slide rail is fixedly connected to the base 902, and a slider matching the slide rail is provided at the bottom of the slide table 901. A drive device for moving the base 902 is installed on the base 902. The drive device can be a pneumatic cylinder or a hydraulic cylinder, and the output end of the drive device is connected to the slide table 901.

[0072] In some embodiments not shown, the slide 901 and the base 902 can be ball screw slides 901. That is, two support shaft seats are installed on the base 902, and the screw shaft is installed between the support shaft seats. One end of the screw shaft is connected to the output shaft of the motor through a coupling. A screw nut is installed on the screw shaft. The slide 901 is detachably connected to the screw nut. The base 902 is also provided with a guide rail. The lower surface of the slide 901 is provided with a guide rail block that matches the guide rail. The screw shaft is driven to rotate by the drive motor 402 so that the screw nut moves linearly along the length direction of the screw shaft. By controlling the forward and reverse rotation of the motor output shaft, the screw nut can reciprocate along the length direction of the screw shaft. When the screw nut moves, it can synchronously drive the slide 901 to move, thereby realizing the movement of the drilling device 4 and drilling down the optical strain gauge 12 installed in the test rock mass 10.

[0073] In some implementations, reference Figure 1As shown, the releasing drilling device 4 comprises a mounting frame 401, a driving motor 402, a first transmission assembly 403, a driving rod 404, a second transmission assembly 405, a transmission rod 406, a variable-diameter joint 407, a core sleeve 408 and a hollow drill bit 409, wherein the output shaft of the driving motor 402 is connected with the driving rod 404 through the first transmission assembly 403, the driving rod 404 is connected with the transmission rod 406 through the second transmission assembly 405, one end of the transmission rod 406 away from the second transmission assembly 405 is connected with the variable-diameter joint 407, the variable-diameter joint 407 is used for connecting the core sleeve 408, one end of the core sleeve 408 away from the variable-diameter joint 407 is connected with the hollow drill bit 409, that is, the output shaft of the driving motor 402 can drive the driving rod 404 to rotate through the transmission of the first transmission assembly 403, when the driving rod 404 rotates, the driving rod 404 can drive the transmission rod 406 to rotate through the second transmission assembly 405, one end of the transmission rod is connected with the core sleeve 408 and the hollow drill bit 409 through the variable-diameter joint 407, therefore, the transmission rod 406 can drive the core sleeve 408 and the hollow drill bit 409 to rotate, when it is needed to remove the optical strain gauge 12 installed in the test rock 10, the moving assembly 9 can be started to drive the sliding table 901 to move the releasing drilling device 4 as a whole, so that the hollow drill bit 409 can contact the test rock 10 through the drilling hole 301 and start the drilling operation, the optical strain gauge 12 drilled and the part of the rock wrapped outside the optical strain gauge 12 are located in the core sleeve 408.

[0074] In some embodiments, with reference to Figure 1 As shown, in order to enable the driving rod 404 and the transmission rod 406 to rotate stably, a bearing seat for fixing the driving rod 404 and the transmission rod 406 can be arranged on the mounting frame 401, and in order to enable the core sleeve 408 to rotate stably, an extension sleeve 410 for supporting the core sleeve 408 is fixedly connected to the mounting frame 401, the inner wall surface of the extension sleeve 410 is provided with a ring 411, the core sleeve 408 passes through the ring 411 and a bearing is arranged at the connecting part of the core sleeve 408 and the ring 411, that is, the extension sleeve 410 and the ring 411 support the core sleeve 408, and the bearing arranged at the connecting part of the core sleeve 408 and the ring 411 can reduce the friction between the core sleeves 408, so that the core sleeve 408 can rotate more smoothly.

[0075] In some embodiments, with reference to Figure 1 As shown, the first transmission assembly 403 comprises a first belt pulley 4031 connected to the output shaft of the driving motor 402 and a second belt pulley 4032 mounted on the driving rod 404, and the first belt pulley 4031 and the second belt pulley 4032 are connected through a belt.

[0076] In some embodiments not shown, the first transmission assembly 403 comprises a first sprocket connected to the output shaft of the drive motor 402 and a second sprocket mounted on the drive rod 404, and the first sprocket and the second sprocket are connected by a chain.

[0077] Similarly, the second transmission assembly 405 can also be selected by belt drive or chain drive.

[0078] In some embodiments, referring to Figure 1 As shown, the second transmission assembly 405 is configured as a CVT variable speed transmission mechanism, that is, when the hollow drill bit 409 drills the optical strain gauge 12 in the real reproduction of the downhole stress test work in the laboratory, many factors such as the drilling speed of the hollow drill bit 409 when drilling the optical strain gauge 12 and the rotation speed of the hollow drill bit 409 may cause the measured values to have errors compared to the true values. In order to reduce the error value, the CVT variable speed transmission mechanism can overcome the problem of reduced rotation speed of the hollow drill bit 409 caused by resistance when the hollow drill bit 409 contacts the test rock mass 10, and as much as possible to ensure that the entire drilling process is more stable. The drive rod 404 and the transmission rod 406 are each provided with a variable gear, and the two variable gears are connected by a steel belt drive. At the same time, a hydraulic assembly (including a hydraulic pump, a hydraulic cylinder, and a control valve, wherein the hydraulic pump provides hydraulic power to deliver hydraulic oil to the hydraulic cylinder of the variable gear; the hydraulic cylinder is connected to the variable gear and is driven by the pressure of the hydraulic oil to change the diameter of the gear; the control valve is used to adjust the flow direction and pressure of the hydraulic oil to accurately control the diameter change of the variable gear) can be installed on the upper surface of the sliding table 901, which facilitates the control and adjustment of the variable gear.

[0079] In some embodiments, when the hollow drill bit 409 drills the optical strain gauge 12, in order to prevent the temperature from being too high during drilling to cause the surrounding rock to crack, a water spraying cooling device can be provided, wherein the water spraying pipe of the water spraying cooling device is aimed at the drilling position, thereby reducing the temperature during drilling.

[0080] Device usage instructions: Before testing, the test rock mass 10 needs to be placed on the upper surface of the open slot 105 and the first uniform force plate 6, the second uniform force plate 7 and the third uniform force plate 8 are placed in the appropriate position in turn. Then the counterforce assembly is installed, that is, after the fixed plate 201 and the counterforce plate 3 are inserted into the first insertion slot 101 and the second insertion slot 102 respectively, the fixed plate 201 and the counterforce plate 3 are fixed by bolts, and then the connecting beam 202 is installed between the fixed plate 201 and the counterforce plate 3. The fixed plate 201 and the counterforce plate 3 are partially overlapped by the clamping groove 20221 and the mounting part 2022 to increase the connection strength. Before drilling, it is necessary to ensure that the hollow drill bit 409 can contact the test rock mass 10 through the drilling hole 301 on the counterforce plate 3, and then the optical strain gauge 12 installed inside is drilled.

[0081] Description of optical strain measurement device 12: Referring to Figure 13 and Figure 14 As shown in the figure, the optical strain measurement device 12 comprises a mounting frame, a shooting module and an illuminating device for supplementing light inside the mounting hole so that the shooting module can clearly and continuously record the speckle in the speckle coating on the hole wall of the mounting hole. The shooting module and the illuminating device are both mounted on the mounting frame. For example, the number of shooting modules is multiple, and the multiple shooting modules are arranged along the length direction of the mounting frame. The shooting module comprises a first mounting plate 1201, a second mounting plate 1202 and a micro camera 1203. The first mounting plate 1201 and the second mounting plate 1202 are partially overlapped and fixed, and have an included angle therebetween. The first mounting plate 1201 is mounted with a micro camera 1203 at both ends of its length. The second mounting plate 1202 is mounted with a micro camera 1203 at both ends of its length. The mounting frame has multiple mounting surfaces, and each mounting surface is mounted with one shooting module. For the convenience of understanding, the contour of the mounting frame is an equilateral triangle. Each group of shooting modules has four micro cameras 1203, and the focal points of the four micro cameras 1203 in each group are concentrated at one point, that is, as shown in the figure, there are three focal points A, B and C, and each group of shooting modules corresponds to one focal point. Figure 13

[0082] For example, the image data processing computer comprises a DIC image data processing computer. The DIC image data processing computer is built-in with a three-dimensional DIC image processing software and a ground stress calculation software. The three-dimensional DIC image processing software can form a three-dimensional strain data model through three-dimensional reconstruction of the collected curved surface images.

[0083] The optical strain measurement device 12 further comprises a glass cover, a power supply unit, a connector, a data storage and transmission unit and a remote control unit. The glass cover is provided outside the mounting frame for protection. The illuminating device can be provided with multiple illuminating devices according to actual needs, and the multiple illuminating devices are arranged on the mounting frame in intervals. The included angle between the first mounting plate 1201 and the second mounting plate 1202 is 45°. The power supply unit can provide power support for the micro camera 1203 and the illuminating light source in the DIC image data collector, so as to keep the system stable. The data storage and transmission unit can transmit the DIC image data recorded by the micro camera 1203 to the DIC image data processing computer. The storage function can also avoid the problem of image loss caused by poor signal inside the mounting hole. The stored images are convenient for checking in the later period. The remote control unit adjusts the brightness of the internal illuminating light source and performs zooming operation on the camera through wireless transmission technology.

[0084] ​For example, taking the miniature camera 1203 mounted on the first mounting plate 1201 as an example, the two miniature cameras 1203 on the first mounting plate 1201 are symmetrically arranged and the lens angle of the miniature camera 1203 has an angle of 15° with the central axis of the miniature camera 1203 body. The same applies to the miniature camera 1203 on the second mounting plate 1202, so that the focus of each group of four miniature cameras 1203 will be concentrated on one point.

[0085] For example, the image data captured by the miniature camera 1203 is transmitted to the DIC image data processing computer terminal via Bluetooth for real-time observation and remote control via Bluetooth.

[0086] The principle of 3D DIC full-field strain measurement is to create some randomly distributed, high-contrast speckles on the surface of the measured area. By capturing the movement of speckle features at the pixel level, and using optimized 3D digital image correlation algorithms, it provides a method for measuring the morphology, displacement and strain data of the entire field of view in three-dimensional space for the experiment. It is usually divided into four steps: speckle creation, system calibration, strain measurement and image analysis. To obtain the strain on the curved surface, dual micro-cameras 1203 (two micro-cameras 1203 on the first mounting plate 1201 or the second mounting plate 1202 with an angle of 15° between the micro-camera 1203 body and the central axis of the micro-camera 1203 body) are used to monitor the area to be measured. The surface strain of the curved surface is reconstructed in three dimensions through algorithm correction. This technology can obtain the horizontal and vertical strain of the curved surface. Since the ground stress has the maximum principal stress, intermediate principal stress, and minimum principal stress and different azimuth angles, it is necessary to add strain in two more directions to obtain strain in four different directions. By setting the positional relationship of the micro-cameras 1203, the two micro-cameras 1203 are symmetrically arranged. Through the micro-cameras 1203 at different angles in the camera holder, the coordinates of the same point can be indirectly transformed, thereby obtaining two strains with an angle of 45° with the horizontal strain and the vertical strain. Therefore, four sets of strain data in different directions can be obtained at a measurement point (focus A, focus B, or focus C). Another advantage of non-contact three-dimensional strain optical measurement technology is that it can measure the full-field strain across the entire surface, rather than being limited to a single measurement point. This allows for the acquisition of more data for calculation, thereby reducing computational errors. For simplicity, as shown... Figure 13 As shown, the present invention divides the entire measurement space into three strain regions along the axial and circumferential directions in the measurement area. A point is selected from each of the three regions as a measurement point (focus A, focus B, or focus C). Focus A, focus B, and focus C are distributed at intervals along the depth direction of the mounting hole, thereby forming three strain regions. After DIC image post-processing by the DIC image data processing computer, a total of 12 sets of strain data are obtained. Finally, the ground stress data is obtained by using the formula built into the ground stress calculation software in the DIC image data processing computer.

[0087] Based on the same inventive concept, as Figure 15 shown, the application also provides an indoor geo-stress test method based on optical strain measurement, which is suitable for any one of the above-mentioned indoor geo-stress test devices based on optical strain measurement, and comprises the following steps:

[0088] Step 101, spray the mounting hole on the test rock mass 10 for installing the optical strain measurement device 12, so that the mounting hole is covered with a speckle coating, and the speckles on the speckle coating are used to capture the speckle characteristics by the micro camera 1203.

[0089] Step 102, after the spraying is completed and the coating is dried, the optical strain measurement device 12 is installed into the mounting hole, so that the speckles in the speckle coating are continuously recorded by image shooting by the optical strain measurement device, and the obtained images are continuously received by the external image data processing computer.

[0090] Step 103, the test rock mass 10 is subjected to a preset geo-stress by the above-mentioned indoor geo-stress test device based on optical strain measurement, at this time the micro camera 1203 is required to shoot the speckles and capture the speckle characteristics (record the speckle strain images before stress relief, three measurement points are recorded by three groups of shooting modules respectively), then the optical strain measurement device 12 is subjected to stress relief by the relief drilling device 4, during the relief process the micro camera 1203 also records the speckle characteristics in real time, and the image data recorded by the micro camera 1203 can be transmitted to the DIC image data processing computer through the data storage and transmission unit, and the recorded images are processed by the DIC image data processing computer, wherein the DIC images of the three measurement points before stress relief are converted into initial strain data by the DIC image data processing computer; the DIC images after stress relief are converted into final relief strain data, specifically, taking one group of shooting modules as an example, two micro cameras 1203 installed on the first mounting plate 1201 record DIC images, which are processed by the DIC image data processing computer to obtain a horizontal strain and a vertical strain, in order to facilitate understanding, the horizontal strain and the vertical strain are defined as the first direction strain and the second direction strain, because the first mounting plate 1201 and the second mounting plate 1202 have a 45° angle, two micro cameras 1203 installed on the second mounting plate 1202 record DIC images, which are processed by the DIC image data processing computer to obtain a third direction strain and a fourth direction strain, similarly, the three measurement points (focal point A, focal point B, focal point C) obtain 12 direction strain data.

[0091] In some embodiments, mechanical parameter determination is performed, the test rock mass 10 is processed and subjected to basic mechanical test, and the elastic modulus and Poisson's ratio of the test rock mass 10 are obtained.

[0092] Step 104, converting the 12-directional strain data into stress values according to the elastic theory formula, comparing the stress values with preset stress values, and evaluating the stress relief effect based on the comparison result.

[0093] The specific formula is as follows:

[0094]

[0095]

[0096] wherein, E is the elastic modulus of the rock sample; the matrix M is a coefficient matrix for solving stress components according to the strain data directions obtained by different optical strain measurement devices, v is the Poisson's ratio of the rock sample;

[0097] For example, for the monitoring angles of the three groups of shooting modules, for the convenience of understanding, the positive direction of the horizontal Y axis is set as 0°, at this time, the monitoring angles of the three groups of shooting modules are 90°, -30° and -150° respectively.

[0098] The preset stress value is the stress applied by the hydraulic loading column 11, as shown in Figures 2 to 4 for the convenience of understanding, three coordinate axes are established, including X, Y and Z, wherein, the Z direction (the direction of the maximum principal stress) is perpendicular to the bearing table, the Y direction (the direction of the intermediate principal stress) is along the length direction of the bearing table 1, and the X direction (the direction of the minimum principal stress) is along the mounting hole direction, based on this, σ x 、 σ y 、 σ z that is, the minimum principal stress, the intermediate principal stress and the maximum principal stress; σ x 、 σ y 、 σ z is the preset stress value in the three directions.

[0099] ε n is the initial strain before relief, ε' n is the final strain after relief, Δ ε n = ε' n - ε n based on this, the above-mentioned 12-directional initial strain data are respectively ε 1、ε 2. ε 3. ε 4. ε 5. ε 6. ε 7. ε 8. ε 9. ε 10 , ε 11 , ε 12 The final release strain data for the above 12 directions are as follows: ε '1、 ε '2、 ε '3、 ε '4、 ε '5、 ε '6、 ε 7. ε '8、 ε '9、 ε ' 10 , ε ' 11 , ε ' 12 ,by ε Taking 1 as an example, Δ ε 1= ε '1- ε 1;

[0100] The six stress components are respectively σ' x , σ' y , σ' z , τ xy , τ yz , τ zx， in, τ xy This represents the shear stress acting on the x-plane and along the y-direction. τ yz This represents the shear stress acting on the y-plane along the z-direction. τ zx Let represent the shear stress acting on the z-plane along the x-direction, where σ' x , σ' y , σ' z The strain data is obtained by using the optical strain gauge 12 and then solving the problem using elasticity theory formulas.

[0101] Step 105, data processing of recorded images is performed by the DIC image data processing computer, real-time strain data is converted by the DIC image data processing computer during the stress relief process, and the real-time strain data is plotted into a strain-relief footage curve, wherein by observing the fitting of the strain-relief footage curve, among the data curves of the twelve directions, if the data curves of more than 10 directions are relatively smooth, the stress relief effect is excellent; if the data curves of more than 8 directions are relatively smooth, the stress relief effect is good; if the data curves of more than 6 directions are relatively smooth, the stress relief effect is medium; and if the data curves of less than 6 directions are relatively smooth, the stress relief effect is poor.

[0102] In addition to observing the data curve, it can also be checked whether the extracted core is broken. During the core extraction process, if the diameter of the hollow drill bit is small or the footage of the hollow drill bit is long, it is very likely that the core will be broken during the contact process. Therefore, if it is not broken, the stress relief effect is good, otherwise the stress relief effect is poor.

[0103] It should be understood by those of ordinary skill in the art that the above discussion of any embodiment is only exemplary and is not intended to imply that the scope (including claims) of the present disclosure is limited to these examples; under the idea of the present application, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of the present application as described above. In order to be brief, they are not provided in details.

[0104] Embodiments of the present application are intended to cover all such alternatives, modifications and variations as fall within the broad scope of the appended claims. Accordingly, any and all such modifications, variations or equivalents that fall within the spirit and scope of the application are intended to be included within the scope of the application.

Claims

1. An indoor geostress testing apparatus based on optical strain measurement, characterized in that, The stress simulation device comprises a bearing table and a counterforce assembly installed on the bearing table, the bearing table is provided with a placing position for placing a test rock mass, the test rock mass is provided with an installation hole for installing an optical strain measuring device, the counterforce assembly is provided with openings for penetrating a hydraulic loading column at two ends oppositely arranged along a first direction, the counterforce assembly is provided with an opening for penetrating the hydraulic loading column at an end away from the placing position, the counterforce assembly is provided with a drilling hole and an opening for penetrating the hydraulic loading column at two ends oppositely arranged along a second direction, and the first direction is perpendicular to the second direction. The stress simulation device further comprises a stress relieving device, the stress relieving device is provided with a hollow drill bit for drilling the optical strain measuring device installed in the installation hole, the installation hole, the drilling hole and the hollow drill bit are coaxially arranged, the optical strain measuring device is used for continuously recording images of speckles in a speckle coating applied on a hole wall of the installation hole to obtain corresponding strain data, a stress test equipment is used for applying a preset ground stress on the test rock mass, at this time, the optical strain measuring device installed in the installation hole records speckle characteristics before stress relief. Then, the optical strain measuring device records speckle characteristics at this time in a process of relieving stress of the optical strain measuring device in the installation hole by the stress relieving device. The optical strain measuring device comprises a mounting frame, a shooting module and an illuminating device. The counterforce assembly comprises a counterforce frame and a counterforce plate, the counterforce plate is provided with the drilling hole, the counterforce frame comprises a fixed plate provided with the opening and a connecting beam used for connecting the fixed plate and the counterforce plate, the bearing table is provided with a first plug-in slot for plugging the fixed plate and a second plug-in slot for plugging the counterforce plate, the bearing table is provided with a first threaded hole and a second threaded hole at two ends oppositely arranged along the second direction, the fixed plate is provided with a first through hole corresponding to the first threaded hole, and the counterforce plate is provided with a second through hole corresponding to the second threaded hole. The placing position is configured as an open slot recessed on an upper surface of the bearing table. Two ends oppositely arranged along the second direction of the open slot are respectively a channel opening and a positioning side wall surface, and the positioning side wall surface is used for positioning the test rock mass. The stress simulation device further comprises first uniform force plates, the number of the first uniform force plates is two, and the two first uniform force plates are arranged at two ends oppositely arranged along the first direction of the open slot. An end of the first uniform force plate close to the open slot is fixedly connected with a support plate, the support plate is perpendicular to the first uniform force plate, and both side wall surfaces of the open slot oppositely arranged along the first direction are provided with receiving grooves for plugging and receiving the support plate. A second uniform force plate is further arranged between the positioning side wall surface and the test rock mass, and a third uniform force plate is placed on an upper surface of the test rock mass. An end surface of the counterforce frame away from the drilling hole is provided with an opening.

2. The indoor ground stress testing apparatus based on optical strain measurement according to claim 1, characterized in that, The connecting beam comprises a connecting rod and mounting pieces fixedly connected at two ends of the connecting rod.

3. The indoor geostress testing apparatus based on optical strain measurement according to claim 1, characterized in that, The mounting pieces are provided with clamping grooves and first through holes for penetrating a screw rod, and the fixed plate and the counterforce plate are provided with second through holes corresponding to the first through holes. ​ The number of the connecting beams is two, the two connecting beams are oppositely arranged along a first direction, and the two connecting beams are arranged between the fixed plate and the counterforce plate.

4. The optical strain measurement based laboratory in-situ stress testing apparatus according to claim 1, wherein, The stress testing device further comprises a moving assembly; The moving assembly comprises a sliding table and a base, the sliding table is slidingly connected to the base, and the unloading drilling device is mounted on the upper surface of the sliding table; The unloading drilling device comprises a mounting frame, a driving motor, a first transmission assembly, a driving rod, a second transmission assembly, a transmission rod, a variable-diameter joint, a core sleeve and the hollow drill bit; The output shaft of the driving motor is connected to the driving rod through the first transmission assembly, the driving rod is connected to the transmission rod through the second transmission assembly, one end of the transmission rod away from the second transmission assembly is connected to the variable-diameter joint, the variable-diameter joint is used for connecting the core sleeve, and one end of the core sleeve away from the variable-diameter joint is connected to the hollow drill bit; The mounting frame is provided with a bearing seat for fixing the driving rod and the transmission rod, and an extension sleeve for supporting the core sleeve is fixedly connected to the mounting frame, the inner wall surface of the extension sleeve is provided with a ring, the core sleeve passes through the ring, and bearings are arranged at the connection parts of the core sleeve and the ring.

5. The indoor geostress testing apparatus based on optical strain measurement according to claim 4, characterized in that, The first transmission assembly comprises a first belt pulley connected to the output shaft of the driving motor and a second belt pulley mounted on the driving rod, the first belt pulley and the second belt pulley are connected through a belt, and the second transmission assembly is configured as a stepless speed change mechanism.

6. The optical strain measurement based laboratory in-situ stress testing apparatus of claim 1, wherein, The shooting modules and the lighting devices are mounted on the mounting rack, the number of the shooting modules is multiple, the multiple shooting modules are arranged at intervals along the length direction of the mounting rack, each shooting module comprises a first mounting plate, a second mounting plate and a micro camera, the first mounting plate and the second mounting plate are partially overlapped and fixedly connected, the first mounting plate and the second mounting plate have an included angle therebetween, the micro camera is mounted on both ends of the first mounting plate along the length direction of the first mounting plate, the micro camera is mounted on both ends of the second mounting plate along the length direction of the second mounting plate, and the mounting rack has multiple mounting surfaces, one shooting module is mounted on each mounting surface.

7. A method of optical strain measurement-based laboratory geostress test using the optical strain measurement-based laboratory geostress test apparatus according to any one of claims 1 to 6, characterized by, Comprise: The speckle liquid is applied to the inner wall surface of the mounting hole to form a speckle coating; The optical strain measuring device is installed through the mounting hole, so that the speckles in the speckle coating are continuously imaged and recorded by the optical strain measuring device, and the obtained images are continuously received by an external image data processing computer; According to the preset stress value, the hydraulic loading column applies a preset stress to the test rock mass, so as to simulate the ground stress borne by the rock mass in an actual scene; The test rock mass is subjected to stress relief through the hollow drill bit, and then the recorded images are subjected to data processing by the image data processing computer to obtain strain data. The strain data is converted into stress values according to the elastic theory formula, the stress values are compared with the preset stress values, and stress relief effects are evaluated based on the comparison results.

Images