In-situ test method and system for dilation angle of rock mass under true stress

Abstract

The present invention provides an in-situ test method and system for the dilation angle of rock mass under true stress, belonging to the technical field of rock mechanics testing. The invention obtains an in-situ test device for rock mass specimens by installing a hydraulic servo module, a lateral pressure loading module, an axial pressure loading module, a deformation measurement module and a control and processing module at the engineering position of the rock mass specimens, solving the problem of in-situ testing of fractured rock mass specimens at the engineering scale. At the same time, damage tests under true triaxial conditions are carried out to obtain the damage model of the rock mass specimens, and the usability and damage state of the rock mass specimens are judged and evaluated. Finally, through the differential loading of the axial pressure loading module and the lateral pressure loading module, the influence of the intermediate principal stress and the rotation of the principal stress axis on the dilation angle of the rock mass is considered, and by fitting the relationship curve between the plastic axial strain and the plastic volumetric strain, the problem that it is difficult to consider the non-linear change of the dilation angle in different pressure stages in conventional laboratory tests is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of rock mechanics testing, and in particular to an in-situ test method and system for the dilation angle of rock mass under true stress action. Background Art

[0002] With the deepening of underground engineering, the volume expansion caused by the large deformation of rock mass under high stress has led to large-scale collapses, which have become frequent new engineering disasters in recent years. Under the action of high stress, deep rock mass will produce significant irreversible volume expansion before failure, which is called the dilation phenomenon of rock mass. The triaxial test results of a large number of indoor rock specimens show that when the external force exceeds the peak strength, the volume of the rock specimen does not decrease, but increases significantly, and the growth rate increases with the increasing stress, eventually leading to the dilation failure of the rock. Engineering rock mass is in a complex three-dimensional stress state. After the excavation of the tunnel, the near-field surrounding rock will experience the rotation of the principal stress axis and the change of the stress path. If the original principal stress direction before excavation is parallel to the tunnel axis, then after excavation, the radial stress will be quickly unloaded, while the tangential principal stress will increase rapidly, and its dilation angle will be affected by the stress path, stress history and stress state. Therefore, studying the dilation characteristics of rock mass during the loading process is the premise for revealing the deformation and failure mechanism of the surrounding rock loosening and rupture zone and the interaction mechanism between the support structure and the surrounding rock, and is of great significance for revealing the deformation and failure mechanism of rock mass under high stress.

[0003] However, rock mass is composed of geological unit bodies with certain primary or secondary joints, fractures or discontinuity surfaces such as structural planes. Generally, it is considered that rock mass is equal to intact rock + joints. In the prior art, the indoor intact rock is used to obtain the dilation angle of rock, and there is still a lack of a test method for determining the dilation angle of fractured in-situ rock mass on the engineering scale. Secondly, before the test, it is impossible to judge the integrity and damage state of the rock. Finally, during the measurement process, it is also impossible to solve the problem of non-linear change of the dilation angle at different pressure stages. Summary of the Invention

[0004] To solve the problems in the above-mentioned existing technologies, the present invention provides an in-situ test method and system for the dilation angle of rock mass under true stress. By installing a hydraulic servo module, a lateral pressure loading module, an axial pressure loading module, a deformation measurement module and a control and processing module at the engineering position of the rock mass specimen, the in-situ test device for the rock mass specimen is obtained, solving the problem of in-situ testing of fractured rock mass specimens at the engineering scale. At the same time, a damage test is carried out to obtain the damage model of the rock mass specimen, and the usability and damage state of the rock mass specimen are judged to ensure the reliability of the test data of the rock mass specimen. Finally, through the differential loading of the axial pressure loading module and the lateral pressure loading module, the influence of the intermediate principal stress and the rotation of the principal stress axis on the dilation angle of the rock mass is considered, and by fitting the relationship curve between the plastic axial strain and the plastic volumetric strain, the problem of non-linear variation of the dilation angle at different pressure stages is solved. To achieve the above object, the technical solution is as follows:

[0005] On the one hand, the present invention provides an in-situ test method for the dilation angle of rock mass under true stress, and the method includes:

[0006] S1. Select the test tunnel wall in the underground project, and use the method of manual chiseling or mechanical cutting to obtain the rock mass specimen and the position information of the rock mass specimen;

[0007] S2. According to the position information of the rock mass specimen, calculate through the Hoek-Brown strength criterion to obtain the stress level that the in-situ test device needs to apply and the stress cycle path of the in-situ test device;

[0008] S3. According to the rock mass specimen, install a hydraulic servo module, a lateral pressure loading module, an axial pressure loading module, a deformation measurement module and a control and processing module to obtain the in-situ test device for the rock mass specimen;

[0009] S4. According to the stress level that the in-situ test device needs to apply, conduct a damage test and input the test data into the damage model for processing to obtain damage information. If the damage information is normal, proceed to the next step S5. If the damage information is an alarm, terminate the test;

[0010] S5. According to the stress level that the in-situ test device needs to apply and the stress cycle path of the in-situ test device, conduct a cyclic test through the in-situ test device of the rock mass specimen to obtain the pressure data set of the rock mass specimen and the strain data set of the rock mass specimen;

[0011] S6. According to the pressure data set of the rock mass specimen and the strain data set of the rock mass specimen, obtain the dilation angle at different pressure stages and the variation law of the dilation angle through the control and processing module.

[0012] Optionally, the hydraulic servo module includes:

[0013] The oil pump unit is used to provide a stable loading pressure.

[0014] The PLC pressure controller is used to achieve precise control of the loading pressure.

[0015] The pressure regulation device is used to adjust the magnitude of the loading pressure.

[0016] The pressure sensor is used to monitor the change of the loading pressure.

[0017] The pipeline is used for the transportation of hydraulic oil.

[0018] The RS485 hub is used for data transmission between the hydraulic servo module and the control processing module.

[0019] Optionally, the lateral pressure loading module includes:

[0020] The X-direction reaction frame is used to provide a constraint reaction force in the X direction.

[0021] The Y-direction reaction frame is used to provide a constraint reaction force in the Y direction.

[0022] The hydraulic pillow is used to simulate the lateral stress conditions of real rock masses.

[0023] The outer rigid backing plate is used to ensure that the forces of the X-direction reaction frame and the Y-direction reaction frame are evenly applied to the hydraulic pillow.

[0024] The inner rigid backing plate is used to ensure that the hydraulic pillow applies a uniform pressure to the rock mass specimen.

[0025] The friction reduction device is used to reduce the influence generated by friction during the test.

[0026] Both the X-direction reaction frame and the Y-direction reaction frame are rectangular steel frames. The short sides of the X-direction reaction frame and the Y-direction reaction frame are respectively in contact with the hydraulic pillow, and the long sides of the X-direction reaction frame and the Y-direction reaction frame are not in contact with the hydraulic pillow. The X-direction reaction frame and the Y-direction reaction frame are arranged in an upper and lower stacked manner, and the short side of the X-direction reaction frame and the long side of the Y-direction reaction frame are arranged in a 90° angle staggered manner.

[0027] Optionally, the axial pressure loading module includes:

[0028] The jack is used to provide the axial pressure required for loading.

[0029] The force transfer column is used to transfer the axial pressure to the leveling ellipsoid.

[0030] The leveling ellipsoid is used to adjust the loading angle and eliminate the eccentric load generated during the loading process.

[0031] The bottom plate is used to disperse the reaction force exerted by the jack on the surrounding rock.

[0032] The backing plate is used to disperse the reaction force exerted by the jack on the rock mass specimen.

[0033] The bottom plate is arranged on the upper part of the leveling ellipsoid. The bottom plate contacts the surrounding rock. The leveling ellipsoid includes a convex ellipsoid and a concave ellipsoid, and the convex ellipsoid and the concave ellipsoid are butted to support rotation in any direction.

[0034] Optionally, the deformation measurement module includes:

[0035] The vertical displacement sensor is used to measure the deformation amount of the rock mass specimen in the vertical direction.

[0036] The horizontal displacement sensor is used to measure the deformation amount of the rock mass specimen in the horizontal direction.

[0037] The bracket is used to fix the vertical displacement sensor and the horizontal displacement sensor.

[0038] The L-shaped fixing seat is used to adjust the position of the horizontal displacement sensor.

[0039] Optionally, in S2, according to the position information of the rock mass specimen, through the Hoek-Brown strength criterion calculation, the stress level that the in-situ test device needs to apply and the stress cycle path of the in-situ test device are obtained, including:

[0040] S21. According to the position information of the rock mass specimen, the burial depth of the rock mass specimen is obtained.

[0041] S22. According to the burial depth of the rock mass specimen, the initial lateral pressure of the rock mass specimen is obtained.

[0042] S23. According to the initial lateral pressure of the rock mass specimen, through the Hoek-Brown strength criterion calculation, the triaxial peak strength of the rock mass specimen is obtained.

[0043] S24. According to the triaxial peak strength of the rock mass specimen, through formula (1), the axial pressure applied by the in-situ test device to the rock mass specimen is obtained.

[0044] (1)

[0045] In the formula: is the axial pressure applied by the in-situ test device to the rock mass specimen. is the triaxial peak strength of the rock mass specimen.

[0046] S25. According to the initial lateral pressure of the rock mass specimen and the axial pressure applied by the in-situ test device to the rock mass specimen, the stress level that the in-situ test device needs to apply is obtained.

[0047] S26. According to the initial lateral pressure of the rock mass specimen and the axial pressure applied to the rock mass specimen by the in-situ testing device, the stress cycle path of the in-situ testing device is obtained through formula (2).

[0048] (2)

[0049] In the formula: is the lateral pressure of the i-th step loading of the in-situ testing device, is the initial lateral pressure of the rock mass specimen, i is the number of steps, i ∈ n, n is the total number of steps, and n ≥ 5.

[0050] Optionally, the training method of the damage model includes:

[0051] S41. According to the stress level applied to the training rock, a constant initial lateral pressure of the training rock is loaded and measured in the X, Y, and Z directions of the training rock through the in-situ testing device of the rock mass specimen, and the strain data of the training rock is obtained;

[0052] S42. The initial lateral pressure of the training rock is repeatedly loaded and unloaded, and the failure state of the training rock and the characteristic points of the strain curve are observed to obtain the damage information of the training rock;

[0053] S43. Replace the training rock and repeat S41 to S43 to obtain a data set of training rocks;

[0054] S44. By setting an initial reinforcement learning environment, an initial damage model is obtained;

[0055] S45. Input the data set of the training rock into the initial damage model, and through the isolation forest learning method, the parameters of the damage model are obtained;

[0056] S46. Update the parameters of the damage model to the initial damage model to obtain the damage model.

[0057] Optionally, in S5, according to the stress level required to be applied by the in-situ testing device and the stress cycle path of the in-situ testing device, a cyclic test is performed through the in-situ testing device of the rock mass specimen to obtain a pressure data set of the rock mass specimen and a strain data set of the rock mass specimen, including:

[0058] S51. According to the stress level required to be applied by the in-situ testing device, the in-situ testing device of the rock mass specimen applies axial pressure at a rate of 0.1 MPa / s to the stress level required to be applied by the in-situ testing device and keeps it constant, and a rock mass specimen with a constant axial pressure is obtained;

[0059] S52. Apply the stress cycle path of the in-situ testing device to the lateral side of the rock mass specimen with a constant axial pressure through the in-situ testing device of the rock mass specimen. According to the cycle rule, collect data through the control processing module to obtain the lateral pressure of the rock mass specimen and the corresponding lateral deformation, as well as the axial pressure and the corresponding axial deformation. The cycle rule is as follows:

[0060] If , then the rock mass specimen has no yield. If , then the rock mass specimen has yield.

[0061] If the rock mass specimen has no yield, unload the lateral pressure to a predetermined , and at the same time, take the maximum value of the step number i as the total number of steps n, and perform cyclic unloading and loading.

[0062] If the rock mass specimen has yield, stop unloading the lateral pressure, and keep the minimum value of the lateral pressure of the i-th step loading of the in-situ testing device always not less than the lateral pressure value corresponding to the yield during the unloading process , and always keep the pressure greater than during subsequent unloading. At the same time, take the maximum value of the step number i as the total number of steps n, and perform cyclic unloading and loading;

[0063] S53. Cycle the previous step S52 according to the set number of times. By collecting the lateral pressure of the rock mass specimen and the corresponding lateral deformation, as well as the axial pressure and the corresponding axial deformation, obtain the pressure data set of the rock mass specimen and the strain data set of the rock mass specimen.

[0064] Optionally, in S6, according to the pressure data set of the rock mass specimen and the strain data set of the rock mass specimen, through the control processing module, obtain the dilatancy angle and the change law of the dilatancy angle under different pressure stages, including:

[0065] S61. According to the pressure data set of the rock mass specimen, calculate through the control processing module to obtain the deviator stress data set of the rock mass specimen;

[0066] S62. According to the strain data set of the rock mass specimen and the deviator stress data set of the rock mass specimen, calculate through the control processing module to obtain the volumetric strain data set of the rock mass specimen;

[0067] S63. According to the volumetric strain data set of the rock mass specimen and the strain data set of the rock mass specimen, calculate through the control processing module to obtain the plastic strain data set of the rock mass specimen;

[0068] S64. According to the plastic strain data set of the rock mass specimen, use piecewise smooth curves or function fitting to obtain the fitting curve of the relationship between the plastic axial strain and the plastic volumetric strain;

[0069] S65. According to the fitting curve of the relationship between the plastic axial strain and the plastic volumetric strain, the pressure stage is discretized finitely. Through formula (3), the dilation angle at the corresponding pressure stage is obtained.

[0070] (3)

[0071] Where: is the dilation angle of the rock mass specimen; is the plastic axial strain of the rock mass specimen; is the plastic volumetric strain of the rock mass specimen;

[0072] S66. According to the dilation angle at the corresponding pressure stage, the pressure stage is changed to obtain the dilation angles at different pressure stages and the variation law of the dilation angle.

[0073] On the other hand, the present invention provides an in-situ test system for the dilation angle of a rock mass under true stress. This system is applied to an in-situ test method for the dilation angle of a rock mass under true stress. The system includes:

[0074] A first acquisition module, which is used to select the test tunnel wall in the underground project and obtain the rock mass specimen and the position information of the rock mass specimen by means of manual chiseling or mechanical cutting;

[0075] A second acquisition module, which is used to calculate the stress level that the in-situ test device needs to apply and the stress cycle path of the in-situ test device according to the position information of the rock mass specimen through the Hoek-Brown strength criterion;

[0076] A device installation module, which is used to install a hydraulic servo module, a lateral pressure loading module, an axial pressure loading module, a deformation measurement module and a control and processing module according to the rock mass specimen to obtain the in-situ test device for the rock mass specimen;

[0077] A damage module, which is used to perform a damage test according to the stress level that the in-situ test device needs to apply and input the test data into the damage model for processing to obtain damage information. If the damage information is normal, the data collection module is applied. If the damage information is an alarm, the test is terminated;

[0078] A data collection module, which is used to perform a cyclic test through the in-situ test device of the rock mass specimen according to the stress level that the in-situ test device needs to apply and the stress cycle path of the in-situ test device to obtain the pressure data set of the rock mass specimen and the strain data set of the rock mass specimen;

[0079] A data processing module, which is used to obtain the dilation angles at different pressure stages and the variation law of the dilation angle according to the pressure data set of the rock mass specimen and the strain data set of the rock mass specimen through the control and processing module.

[0080] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0081] On the one hand, the above solution solves the in-situ test problem of fractured rock mass specimens at the engineering scale by installing a hydraulic servo module, a lateral pressure loading module, an axial pressure loading module, a deformation measurement module and a control and processing module at the engineering position of the rock mass specimen to obtain an in-situ test device for the rock mass specimen. On the second hand, a damage test is carried out to obtain the damage model of the rock mass specimen, and the usability and damage state of the rock mass specimen are judged to ensure the reliability of the test data of the rock mass specimen. On the third hand, through the differential loading of the axial pressure loading module and the lateral pressure loading module, the influence of the intermediate principal stress and the rotation of the principal stress axis on the dilation angle of the rock mass is considered, and by fitting the relationship curve between the plastic axial strain and the plastic volumetric strain, the problem of the non-linear change of the dilation angle at different pressure stages is solved. Description of the Drawings

[0082] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0083] Figure 1 is a flowchart of an embodiment of the in-situ test method for the dilation angle of a rock mass under true stress of the present invention;

[0084] Figure 2 is a schematic diagram of the in-situ test device in an embodiment of the in-situ test method for the dilation angle of a rock mass under true stress of the present invention;

[0085] Figure 3 is a schematic diagram of the hydraulic servo module in an embodiment of the in-situ test method for the dilation angle of a rock mass under true stress of the present invention;

[0086] Figure 4 is a cross-sectional schematic diagram of the lateral pressure loading module in an embodiment of the in-situ test method for the dilation angle of a rock mass under true stress of the present invention;

[0087] Figure 5 is a schematic diagram of the axial pressure loading module in an embodiment of the in-situ test method for the dilation angle of a rock mass under true stress of the present invention;

[0088] Figure 6 is a schematic diagram of the leveling ellipsoid in an embodiment of the in-situ test method for the dilation angle of a rock mass under true stress of the present invention;

[0089] Figure 7It is a schematic diagram of the deformation measurement module in the in-situ test method for the dilation angle of rock mass under true stress of the present invention;

[0090] Figure 8 It is a flow chart of obtaining the stress level to be applied by the in-situ test device and the stress cycling path of the in-situ test device in the in-situ test method for the dilation angle of rock mass under true stress of the present invention;

[0091] Figure 9 It is a flow chart of the training method of the damage model in the in-situ test method for the dilation angle of rock mass under true stress of the present invention;

[0092] Figure 10 It is a flow chart of obtaining the pressure data set of the rock mass specimen and the strain data set of the rock mass specimen in the in-situ test method for the dilation angle of rock mass under true stress of the present invention;

[0093] Figure 11 It is a flow chart of obtaining the dilation angle and the variation law of the dilation angle at different pressure stages in the in-situ test method for the dilation angle of rock mass under true stress of the present invention;

[0094] Figure 12 It is a curve graph of the variation of deviator stress and lateral stress with time in the in-situ test method for the dilation angle of rock mass under true stress of the present invention;

[0095] Figure 13 It is a curve graph of the relationship between axial strain, lateral strain and deviator stress in the in-situ test method for the dilation angle of rock mass under true stress of the present invention;

[0096] Figure 14 It is a curve graph of the relationship between axial strain and volumetric strain in the in-situ test method for the dilation angle of rock mass under true stress of the present invention;

[0097] Figure 15 It is a curve graph of the relationship between plastic axial strain and plastic volumetric strain in the in-situ test method for the dilation angle of rock mass under true stress of the present invention;

[0098] Figure 16 It is a system block diagram of the in-situ test system for the dilation angle of rock mass under true stress of the present invention.

[0099] Description of reference numerals in the figure: Hydraulic servo module 1, lateral pressure loading module 2, axial pressure loading module 3, deformation measurement module 4, control and processing module 5, rock mass specimen 6, surrounding rock 7, oil pump unit 101, PLC pressure controller 102, pressure regulation device 103, pressure sensor 104, pipeline 105, RS485 hub 106, X-direction reaction frame 201, Y-direction reaction frame 202, hydraulic pillow 203, outer rigid backing plate 204, inner rigid backing plate 205, friction reduction device 206, jack 301, load transfer column 302, leveling ellipsoid 303, bottom plate 304, backing plate 305, convex ellipsoid 3031, concave ellipsoid 3032, vertical displacement sensor 401, horizontal displacement sensor 402, bracket 403, L-shaped fixing seat 404. Detailed implementation manners

[0100] The technical solutions in the present invention will be described below with reference to the accompanying drawings.

[0101] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to represent examples, illustrations or explanations. Any embodiment or design solution described as an "example" in the present invention should not be construed as being more preferred or more advantageous than other embodiments or design solutions. Rather, the use of the word "example" is intended to present concepts in a specific manner. In addition, in the embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one of the two.

[0102] To make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments.

[0103] As Figure 1 The flowchart of the in-situ test method for the dilation angle of rock mass under true stress in the embodiment of the present invention shown and as Figure 2 The schematic diagram of the in-situ test device in the embodiment of the in-situ test method for the dilation angle of rock mass under true stress in the embodiment of the present invention shown, the present invention provides an in-situ test method for the dilation angle of rock mass under true stress, which is implemented by an in-situ test system for the dilation angle of rock mass under true stress, and the method includes:

[0104] S1. Select the test tunnel wall in the underground project, and use the method of manual chiseling or mechanical cutting to obtain the rock mass specimen 6 and the position information of the rock mass specimen;

[0105] Specifically, the length and width of the rock mass specimen 6 are equal, the side length is not less than 30 cm, the height is 2 times the length, the bottom surface of the rock mass specimen 6 is connected to the surrounding rock 7, and the side surface and the top surface of the rock mass specimen 6 need to be polished flat.

[0106] S2. Based on the position information of the rock mass specimen 6, calculate through the Hoek-Brown strength criterion to obtain the stress level that the in-situ test device needs to apply and the stress cycle path of the in-situ test device;

[0107] Specifically, as Figure 8 shown in the flow chart of obtaining the stress level that the in-situ test device needs to apply and the stress cycle path of the in-situ test device in the embodiment of the in-situ test method for the dilation angle of rock mass under true stress of the present invention, in S2, based on the position information of the rock mass specimen 6, calculate through the Hoek-Brown strength criterion to obtain the stress level that the in-situ test device needs to apply and the stress cycle path of the in-situ test device, including:

[0108] S21. Based on the position information of the rock mass specimen 6, obtain the buried depth of the rock mass specimen 6;

[0109] S22. Based on the buried depth of the rock mass specimen 6, obtain the initial lateral pressure of the rock mass specimen 6;

[0110] S23. Based on the initial lateral pressure of the rock mass specimen 6, calculate through the Hoek-Brown strength criterion to obtain the triaxial peak strength of the rock mass specimen 6;

[0111] S24. Based on the triaxial peak strength of the rock mass specimen 6, through formula (1), obtain the axial pressure applied by the in-situ test device to the rock mass specimen 6,

[0112] (1)

[0113] In the formula: is the axial pressure applied by the in-situ test device to the rock mass specimen, is the triaxial peak strength of the rock mass specimen;

[0114] S25. Based on the initial lateral pressure of the rock mass specimen 6 and the axial pressure applied by the in-situ test device to the rock mass specimen 6, obtain the stress level that the in-situ test device needs to apply;

[0115] S26. Based on the initial lateral pressure of the rock mass specimen 6 and the axial pressure applied by the in-situ test device to the rock mass specimen 6, through formula (2), obtain the stress cycle path of the in-situ test device,

[0116] (2)

[0117] In the formula: is the lateral pressure of the i-th step loading of the in-situ test device, is the initial lateral pressure of the rock mass specimen, i is the step number, i ∈ n, n is the total number of steps, n ≥ 5.

[0118] S3. Install the hydraulic servo module 1, lateral pressure loading module 2, axial pressure loading module 3, deformation measurement module 4 and control and processing module 5 according to the rock mass specimen 6 to obtain an in-situ test device for the rock mass specimen.

[0119] Specifically, as Figure 3 the schematic diagram of the hydraulic servo module in the embodiment of the in-situ test method for the rock mass dilation angle under true stress of the present invention shown, this hydraulic servo module 1 includes:

[0120] An oil pump unit 101 for providing a stable loading pressure,

[0121] A PLC pressure controller 102 for achieving precise control of the loading pressure,

[0122] A pressure regulation device 103 for adjusting the magnitude of the loading pressure,

[0123] A pressure sensor 104 for monitoring the change of the loading pressure,

[0124] A pipeline 105 for transporting hydraulic oil,

[0125] An RS485 hub 106 for data transmission between the hydraulic servo module 1 and the control and processing module 5;

[0126] Further, the oil pump unit 101 is composed of 3 groups of independent motors and oil pumps, providing stable loading pressures in the X, Y, and Z directions respectively;

[0127] The PLC pressure controller 102 receives the pressure instruction from the control and processing module 5 through the RS485 hub 106 and sends a pressure regulation instruction to the pressure regulation device 103;

[0128] The pressure regulation device 103 is installed at the output end of the oil pump unit 101 and adjusts the output pressure of the oil pump unit 101 according to the received pressure regulation instruction;

[0129] The pressure sensor 104 is installed at the front end of the pipeline 105, monitors the pressure change of the pipeline 105 in real time, and sends it to the pressure regulation device 103;

[0130] The pipeline 105 connects the hydraulic servo module 1 with the lateral pressure loading module 2 and the axial pressure loading module 3.

[0131] Specifically, as Figure 4 the cross-sectional schematic diagram of the lateral pressure loading module in the embodiment of the in-situ test method for the rock mass dilation angle under true stress of the present invention shown, this lateral pressure loading module 2 includes:

[0132] The X-direction reaction force frame 201 is used to provide the constraint reaction force in the X direction.

[0133] The Y-direction reaction force frame 202 is used to provide the constraint reaction force in the Y direction.

[0134] The hydraulic pillow 203 is used to simulate the lateral stress conditions of the real rock mass.

[0135] The outer rigid backing plate 204 is used to ensure that the forces of the X-direction reaction force frame 201 and the Y-direction reaction force frame 202 are evenly applied to the hydraulic pillow.

[0136] The inner rigid backing plate 205 is used to ensure that the hydraulic pillow 203 applies a uniform pressure to the rock mass specimen 6.

[0137] The friction reduction device 206 is used to reduce the influence generated by friction during the test.

[0138] Furthermore, the X-direction reaction force frame 201 and the Y-direction reaction force frame 202 respectively provide reaction forces for the hydraulic pillow 203 in the X direction and the Y direction.

[0139] The X-direction reaction force frame 201 and the Y-direction reaction force frame 202 are both rectangular steel frames. The short sides of the X-direction reaction force frame 201 and the Y-direction reaction force frame 202 are respectively in contact with the hydraulic pillow 203, and the long sides of the X-direction reaction force frame 201 and the Y-direction reaction force frame 202 are not in contact with the hydraulic pillow 203. The X-direction reaction force frame 201 and the Y-direction reaction force frame 202 are arranged in an up-and-down stacked manner, and the short side of the X-direction reaction force frame 201 and the long side of the Y-direction reaction force frame 202 are arranged in a 90° angle staggered manner.

[0140] The friction reduction device 206 is formed by overlapping two plastic plates with lubricating oil applied in the middle, and is used to reduce the friction between the hydraulic pillow 203 and the rock mass specimen 6.

[0141] Specifically, as Figure 5 shown in the schematic diagram of the axial pressure loading module in the embodiment of the in-situ test method for the dilation angle of the rock mass under the action of the true stress of the present invention, the axial pressure loading module 3 includes:

[0142] The jack 301 is used to provide the axial pressure required for loading.

[0143] The force transfer column 302 is used to transfer the axial pressure to the leveling ellipsoid 303.

[0144] The leveling ellipsoid 303 is used to adjust the loading angle and eliminate the eccentric load generated during the loading process.

[0145] The bottom plate 304 is used to disperse the reaction force exerted by the jack 301 on the surrounding rock 7.

[0146] A backing plate 305 for dispersing the reaction force exerted by the jack 301 on the rock mass specimen 6.

[0147] Further, the lower end of the jack 301 is connected to the rock mass specimen 6 through the backing plate 305, and the force transmission column 302 is arranged at the upper end.

[0148] As Figure 6 The schematic diagram of the leveling ellipsoid in the in-situ test method for the rock mass dilation angle under true stress according to the embodiment of the present invention as shown. The bottom plate 304 is arranged on the upper part of the leveling ellipsoid 303. The bottom plate 304 is in contact with the surrounding rock 7. The leveling ellipsoid 303 includes a convex ellipsoid 3031 and a concave ellipsoid 3032. The convex ellipsoid 3031 and the concave ellipsoid 3032 are butted and support rotation in any direction.

[0149] Specifically, as Figure 7 The schematic diagram of the deformation measurement module in the in-situ test method for the rock mass dilation angle under true stress according to the embodiment of the present invention as shown. The deformation measurement module 4 includes:

[0150] A vertical displacement sensor 401 for measuring the deformation amount of the rock mass specimen 6 in the vertical direction.

[0151] A horizontal displacement sensor 402 for measuring the deformation amount of the rock mass specimen 6 in the horizontal direction.

[0152] A bracket 403 for fixing the vertical displacement sensor 401 and the horizontal displacement sensor 402.

[0153] An L-shaped fixing seat 404 for adjusting the position of the horizontal displacement sensor 402.

[0154] Further, the vertical displacement sensor 401 and the horizontal displacement sensor 402 are connected to the bracket 403 through the L-shaped fixing seat 404. The end of the bottom surface of the L-shaped fixing seat 404 is connected to the bracket 403 by screws.

[0155] One horizontal displacement sensor 402 is arranged at the center position of each of the four side surfaces of the rock mass specimen 6, and one vertical displacement sensor 401 is symmetrically arranged on both sides of the upper end of the rock mass specimen 6.

[0156] The vertical displacement sensor 401 and the horizontal displacement sensor 402 are connected to the RS485 hub 106. The data of the vertical displacement sensor 401 and the data of the horizontal displacement sensor 402 are transmitted to the control processing module 5 through the RS485 hub 106.

[0157] S4. According to the stress level that needs to be applied by the in-situ testing device, conduct a damage test and input the test data into the damage model for processing to obtain damage information. If the damage information is normal, proceed to the next step S5. If the damage information is an alarm, terminate the test;

[0158] Specifically, as Figure 9 shown in the flowchart of the training method of the damage model in the embodiment of the in-situ test method for the rock mass dilation angle under true stress of the present invention, the training method of the damage model includes:

[0159] S41. According to the stress level applied to the training rock, apply a constant initial lateral pressure of the training rock in the X, Y, and Z directions through the in-situ testing device of the rock mass specimen and measure to obtain the strain data of the training rock;

[0160] S42. Repeatedly load and unload the initial lateral pressure of the training rock, observe the failure state of the training rock and the characteristic points of the strain curve to obtain the damage information of the training rock;

[0161] S43. Replace the training rock and repeat S41 - S43 to obtain a data set of the training rock;

[0162] S44. Obtain an initialized damage model by setting an initialized reinforcement learning environment;

[0163] S45. Input the data set of the training rock into the initialized damage model and obtain the parameters of the damage model through the isolation forest learning method;

[0164] S46. Update the parameters of the damage model to the initialized damage model to obtain the damage model.

[0165] S5. According to the stress level of the in-situ testing device and the stress cycle path of the in-situ testing device, conduct a cyclic test through the in-situ testing device of the rock mass specimen to obtain a pressure data set of the rock mass specimen and a strain data set of the rock mass specimen;

[0166] Specifically, as Figure 10 shown in the flowchart of obtaining the pressure data set of the rock mass specimen and the strain data set of the rock mass specimen in the embodiment of the in-situ test method for the rock mass dilation angle under true stress of the present invention, in S5, according to the stress level that needs to be applied by the in-situ testing device and the stress cycle path of the in-situ testing device, conduct a cyclic test through the in-situ testing device of the rock mass specimen 6 to obtain a pressure data set of the rock mass specimen 6 and a strain data set of the rock mass specimen 6, including:

[0167] S51. According to the stress level required by the in-situ testing device, the in-situ testing device for the rock mass specimen 6 applies axial pressure at a rate of 0.1 MPa / s to the stress level required by the in-situ testing device and keeps it constant, obtaining a rock mass specimen with a constant axial pressure;

[0168] S52. Load the stress cycle path required by the in-situ testing device to the side of the rock mass specimen 6 with a constant axial pressure through the in-situ testing device of the rock mass specimen 6. According to the cycle rule, collect data through the control processing module to obtain the lateral pressure of the rock mass specimen 6 and the corresponding lateral deformation, axial pressure and the corresponding axial deformation. The cycle rule is as follows:

[0169] If , then the rock mass specimen 6 has no yield. If , then the rock mass specimen 6 has yield.

[0170] If the rock mass specimen 6 has no yield, unload the lateral pressure to a predetermined . At the same time, take the maximum value of the step number i as the total number of steps n, and perform cyclic unloading and loading.

[0171] If the rock mass specimen 6 has yield, stop unloading the lateral pressure, and keep the minimum value of the lateral pressure of the i-th step loading of the in-situ testing device always not less than the lateral pressure value corresponding to the yield during the unloading process , and always keep the pressure greater than during the subsequent unloading. At the same time, take the maximum value of the step number i as the total number of steps n, and perform cyclic unloading and loading;

[0172] S53. Cycle the previous step S52 according to the set number of times. By collecting the lateral pressure of the rock mass specimen 6 and the corresponding lateral deformation, axial pressure and the corresponding axial deformation, obtain the pressure data set of the rock mass specimen 6 and the strain data set of the rock mass specimen 6.

[0173] S6. According to the pressure data set of the rock mass specimen 6 and the strain data set of the rock mass specimen 6, obtain the dilation angle and the variation law of the dilation angle at different pressure stages through the control processing module.

[0174] Specifically, as Figure 11 shown in the flowchart of obtaining the dilation angle and the variation law of the dilation angle at different pressure stages in the embodiment of the in-situ testing method for the dilation angle of the rock mass under true stress of the present invention, in S6, according to the pressure data set of the rock mass specimen 6 and the strain data set of the rock mass specimen 6, through the control processing module, obtain the dilation angle and the variation law of the dilation angle at different pressure stages, including:

[0175] S61. According to the pressure data set of the rock mass specimen 6, through calculation by the control processing module, the deviator stress data set of the rock mass specimen 6 is obtained;

[0176] Further, the deviator stress calculation method is as shown in formula (4),

[0177] (4)

[0178] In the formula: is the deviator stress, is the axial stress, is the lateral stress;

[0179] As Figure 12 shown in the curve graph of the variation of the deviator stress and the lateral stress with time in the in-situ test method for the dilation angle of the rock mass under the true stress of the present invention, the control processing module plots the curve graph of the variation of the deviator stress and the lateral stress with time.

[0180] S62. According to the strain data set of the rock mass specimen 6 and the deviator stress data set of the rock mass specimen 6, through calculation by the control processing module, the volumetric strain data set of the rock mass specimen 6 is obtained;

[0181] Further, as Figure 13 shown in the curve graph of the relationship between the axial strain, the lateral strain and the deviator stress in the in-situ test method for the dilation angle of the rock mass under the true stress of the present invention, the control processing module plots the curve graph of the relationship between the axial strain, the lateral strain and the deviator stress;

[0182] The calculation method of the volumetric strain is as shown in formula (5),

[0183] (5)

[0184] In the formula: is the total axial strain, is the total lateral strain in the X direction, is the total lateral strain in the Y direction, is the volumetric strain;

[0185] As Figure 14 shown in the curve graph of the relationship between the axial strain and the volumetric strain in the in-situ test method for the dilation angle of the rock mass under the true stress of the present invention, the control processing module plots the curve graph of the relationship between the axial strain and the volumetric strain.

[0186] S63. According to the volumetric strain data set of the rock mass specimen 6 and the strain data set of the rock mass specimen 6, through calculation by the control processing module, the plastic strain data set of the rock mass specimen 6 is obtained;

[0187] Furthermore, according to the characteristics of the irreversible strain increment, in the in-situ test of the dilation angle of rock mass under true stress, the non-recoverable strain at the end of each cycle is the plastic strain corresponding to that cycle.

[0188] S64. According to the plastic strain data set of the rock mass specimen 6, use piecewise smooth curve or function fitting to obtain the fitting curve of the relationship between plastic axial strain and plastic volumetric strain;

[0189] Furthermore, as Figure 15 shown in the curve graph of the relationship between plastic axial strain and plastic volumetric strain in the embodiment of the in-situ test method for the dilation angle of rock mass under true stress of the present invention, the plastic strain can be obtained from the curve graph of the relationship between axial strain and volumetric strain.

[0190] S65. According to the fitting curve of the relationship between the plastic axial strain and the plastic volumetric strain, discretize the pressure stage finitely, and through formula (3), obtain the dilation angle at the corresponding pressure stage,

[0191] (3)

[0192] In the formula: is the dilation angle of the rock mass specimen, is the plastic axial strain of the rock mass specimen, is the plastic volumetric strain of the rock mass specimen;

[0193] Furthermore, as Figure 15 shown in the curve graph of the relationship between plastic axial strain and plastic volumetric strain in the embodiment of the in-situ test method for the dilation angle of rock mass under true stress of the present invention, the control and processing module draws the curve graph of the relationship between plastic axial strain and plastic volumetric strain.

[0194] S66. According to the dilation angle at the corresponding pressure stage, change the pressure stage to obtain the dilation angles at different pressure stages and the variation law of the dilation angle.

[0195] As Figure 16 shown in the system block diagram of the embodiment of the in-situ test system for the dilation angle of rock mass under true stress of the present invention, the present invention provides an in-situ test system for the dilation angle of rock mass under true stress. This system is applied to an in-situ test method for the dilation angle of rock mass under true stress. The system includes a first acquisition module, a second acquisition module, a device installation module, a damage module, a data collection module, and a data processing module. Specifically,

[0196] The first acquisition module is used to select the test tunnel wall in the underground project and obtain the rock mass specimen and the position information of the rock mass specimen by means of manual chiseling or mechanical cutting;

[0197] A second acquisition module, configured to calculate, according to the position information of the rock mass specimen, by using the Hoek-Brown strength criterion, the stress level that the in-situ test device needs to apply and the stress cycle path of the in-situ test device;

[0198] A device installation module, configured to install a hydraulic servo module, a lateral pressure loading module, an axial pressure loading module, a deformation measurement module and a control and processing module according to the rock mass specimen, to obtain an in-situ test device for the rock mass specimen;

[0199] A damage module, configured to perform a damage test according to the stress level that the in-situ test device needs to apply, input test data into a damage model for processing, to obtain damage information. If the damage information is normal, a data collection module is applied; if the damage information is an alarm, the test is terminated;

[0200] A data collection module, configured to perform a cyclic test through the in-situ test device for the rock mass specimen according to the stress level that the in-situ test device needs to apply and the stress cycle path of the in-situ test device, to obtain a pressure data set of the rock mass specimen and a strain data set of the rock mass specimen;

[0201] A data processing module, configured to obtain the dilation angle and the variation law of the dilation angle at different pressure stages through the control and processing module according to the pressure data set of the rock mass specimen and the strain data set of the rock mass specimen.

[0202] The present invention provides a method and a system for in-situ testing of the dilation angle of a rock mass under true stress. By installing a hydraulic servo module, a lateral pressure loading module, an axial pressure loading module, a deformation measurement module and a control and processing module at the engineering position of the rock mass specimen, the in-situ test device for the rock mass specimen is obtained, solving the problem of in-situ testing of fractured rock mass specimens at the engineering scale. At the same time, a damage test is performed to obtain the damage model of the rock mass specimen, to judge the usability and damage state of the rock mass specimen, ensuring the reliability of the test data of the rock mass specimen. Finally, through the differential loading of the axial pressure loading module and the lateral pressure loading module, the influence of the intermediate principal stress and the rotation of the principal stress axis on the dilation angle of the rock mass is considered. By fitting the relationship curve between the plastic axial strain and the plastic volumetric strain, the problem of non-linear variation of the dilation angle at different pressure stages is solved.

[0203] It can be understood that the present invention is described by the above embodiments, and should not be construed as a limitation on the implementation manner and scope of the present invention. As is known to those skilled in the art, various changes or equivalent replacements can be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teaching of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the scope protected by the present invention.

Claims

1. An in-situ test method for the dilation angle of rock mass under true stress, characterized in that The method includes: S1. Select a test tunnel wall in an underground project and use the method of manual chiseling or mechanical cutting to obtain a rock mass specimen and the position information of the rock mass specimen; S2. According to the position information of the rock mass specimen, calculate through the Hoek-Brown strength criterion to obtain the stress level that the in-situ testing device needs to apply and the stress cycle path of the in-situ testing device; The specific steps of S2 include: S21. According to the position information of the rock mass specimen, obtain the buried depth of the rock mass specimen; S22. According to the buried depth of the rock mass specimen, obtain the initial lateral pressure of the rock mass specimen; S23. According to the initial lateral pressure of the rock mass specimen, calculate through the Hoek-Brown strength criterion to obtain the triaxial peak strength of the rock mass specimen; S24. According to the triaxial peak strength of the rock mass specimen, obtain the axial pressure applied by the in-situ testing device to the rock mass specimen through formula (1); （1） In the formula: is the axial pressure applied by the in-situ test device to the rock mass specimen, is the triaxial peak strength of the rock mass specimen; S25. According to the initial lateral pressure of the rock mass specimen and the axial pressure applied by the in-situ testing device to the rock mass specimen, obtain the stress level that the in-situ testing device needs to apply; S26. According to the initial lateral pressure of the rock mass specimen and the axial pressure applied by the in-situ testing device to the rock mass specimen, obtain the stress cycle path of the in-situ testing device through formula (2); （2） Where: is the lateral pressure of the i-th step loading of the in-situ test device, is the initial lateral pressure of the rock mass specimen, i is the step number, i ∈ n, n is the total number of steps, and n ≥ 5; S3. According to the rock mass specimen, install a hydraulic servo module, a lateral pressure loading module, an axial pressure loading module, a deformation measurement module and a control and processing module to obtain an in-situ testing device for the rock mass specimen; S4. According to the stress level that the in-situ testing device needs to apply, conduct a damage test and input the test data into a damage model for processing to obtain damage information. If the damage information is normal, proceed to the next step S5. If the damage information is an alarm, terminate the test; S5. According to the stress level that the in-situ testing device needs to apply and the stress cycle path of the in-situ testing device, conduct a cyclic test through the in-situ testing device of the rock mass specimen to obtain a pressure data set of the rock mass specimen and a strain data set of the rock mass specimen; S6. According to the pressure data set of the rock mass specimen and the strain data set of the rock mass specimen, obtain the dilation angle and the variation law of the dilation angle at different pressure stages through the control and processing module.

2. The in-situ test method for the dilation angle of rock mass under true stress according to claim 1, wherein The hydraulic servo module includes: An oil pump unit for providing a stable loading pressure; A PLC pressure controller for precisely controlling the loading pressure; A pressure regulating device for adjusting the magnitude of the loading pressure; A pressure sensor for monitoring the change of the loading pressure; A pipeline for transporting hydraulic oil; An RS485 hub for data transmission between the hydraulic servo module and the control and processing module.

3. The in-situ test method for the dilation angle of rock mass under true stress according to claim 1, characterized in that The lateral pressure loading module includes: An X-direction reaction frame for providing a constraint reaction force in the X direction; A Y-direction reaction frame for providing a constraint reaction force in the Y direction; A hydraulic pillow for simulating the lateral stress condition of a real rock mass; An outer rigid backing plate for ensuring that the forces of the X-direction reaction frame and the Y-direction reaction frame are evenly applied to the hydraulic pillow. Inner rigid backing plate, which is used to ensure that the hydraulic pillow applies uniform pressure to the rock mass specimen. Friction reduction device, which is used to reduce the influence generated by friction during the test. Both the X-direction reaction frame and the Y-direction reaction frame are rectangular steel frames. The short sides of the X-direction reaction frame and the Y-direction reaction frame are respectively in contact with the hydraulic pillow, and the long sides of the X-direction reaction frame and the Y-direction reaction frame are not in contact with the hydraulic pillow. The X-direction reaction frame and the Y-direction reaction frame are arranged in an up-and-down stacked manner, and the short side of the X-direction reaction frame and the long side of the Y-direction reaction frame are arranged in a 90° angle staggered manner.

4. The in-situ test method for the dilation angle of rock mass under true stress according to claim 1, characterized in that The axial pressure loading module includes: Jack, which is used to provide the axial pressure required for loading. Force transmission column, which is used to transmit the axial pressure to the leveling ellipsoid. The leveling ellipsoid, which is used to adjust the loading angle and eliminate the eccentric load generated during the loading process. Bottom plate, which is used to disperse the reaction force exerted by the jack on the surrounding rock. Backing plate, which is used to disperse the reaction force exerted by the jack on the rock mass specimen. The bottom plate is arranged on the upper part of the leveling ellipsoid, and the bottom plate is in contact with the surrounding rock. The leveling ellipsoid includes a convex ellipsoid and a concave ellipsoid, and the convex ellipsoid and the concave ellipsoid are butt-jointed to support rotation in any direction.

5. The in-situ test method for the dilation angle of rock mass under true stress according to claim 1, characterized in that, The deformation measurement module includes: Vertical displacement sensor, which is used to measure the vertical direction deformation of the rock mass specimen. Horizontal displacement sensor, which is used to measure the horizontal direction deformation of the rock mass specimen. Bracket, which is used to fix the vertical displacement sensor and the horizontal displacement sensor. L-shaped fixing seat, which is used to adjust the position of the horizontal displacement sensor.

6. The in-situ test method for the dilation angle of rock mass under true stress according to claim 1, wherein The training method of the damage model includes: S41. According to the stress level applied to the training rock, apply a constant initial lateral pressure of the training rock in the X, Y, and Z directions to the training rock through the in-situ test device of the rock mass specimen and measure it to obtain the strain data of the training rock. S42. Repeatedly load and unload the initial lateral pressure of the training rock, observe the failure state of the training rock and the characteristic points of the strain curve to obtain the damage information of the training rock. S43. Replace the training rock, repeat S41 - S42 to obtain the data set of the training rock. S44. Obtain the initialized damage model by setting the initialization reinforcement learning environment. S45. Input the data set of the training rock into the initialized damage model, and obtain the parameters of the damage model through the isolation forest learning method. S46. Update the parameters of the damage model to the initialized damage model to obtain the damage model.

7. The in-situ test method for the dilation angle of rock mass under true stress according to claim 1, characterized in that In step S5, according to the stress level required to be applied by the in-situ test device and the stress cycle path of the in-situ test device, perform a cyclic test through the in-situ test device of the rock mass specimen to obtain the pressure data set and the strain data set of the rock mass specimen, including: S51. According to the stress level required to be applied by the in-situ testing device, the in-situ testing device for the rock mass specimen applies axial pressure at a rate of 0.1 MPa / s to the stress level required to be applied by the in-situ testing device and keeps it constant, obtaining a rock mass specimen with a constant axial pressure; S52. Load the stress cycle path of the in-situ testing device onto the lateral side of the rock mass specimen with a constant axial pressure through the in-situ testing device of the rock mass specimen. According to the cyclic rule, collect data through the control and processing module to obtain the lateral pressure of the rock mass specimen and the corresponding lateral deformation, as well as the axial pressure and the corresponding axial deformation. The cyclic rule is as follows: If , then the rock mass specimen has no yield. If , then the rock mass specimen has yield. If the rock mass specimen has no yield, the lateral pressure is unloaded to a predetermined , and at the same time, the maximum value of the step number i is taken as the total number of steps n, and cyclic unloading and loading are carried out. If the rock mass specimen has yield, the lateral pressure unloading stops, and the lateral pressure of the i-th step loading of the in-situ test device is maintained The minimum value is always not less than the lateral pressure value corresponding to the yield during the unloading process , and during subsequent unloading, the pressure is always maintained greater than , meanwhile, the maximum value of the step number i is taken as the total number of steps n, and cyclic unloading and loading are carried out; S53. Repeat the previous step S52 for a set number of times. By collecting the lateral pressure of the rock mass specimen and the corresponding lateral deformation, as well as the axial pressure and the corresponding axial deformation, obtain the pressure data set of the rock mass specimen and the strain data set of the rock mass specimen.

8. The in-situ test method for the dilation angle of rock mass under true stress according to claim 7, characterized in that, In S6, according to the pressure data set of the rock mass specimen and the strain data set of the rock mass specimen, through the control and processing module, obtain the dilation angle and the variation law of the dilation angle at different pressure stages, including: S61. According to the pressure data set of the rock mass specimen, calculate through the control and processing module to obtain the deviator stress data set of the rock mass specimen; S62. According to the strain data set of the rock mass specimen and the deviator stress data set of the rock mass specimen, calculate through the control and processing module to obtain the volumetric strain data set of the rock mass specimen; S63. According to the volumetric strain data set of the rock mass specimen and the strain data set of the rock mass specimen, calculate through the control and processing module to obtain the plastic strain data set of the rock mass specimen; S64. According to the plastic strain data set of the rock mass specimen, use piecewise smooth curves or function fitting to obtain the fitting curve of the relationship between plastic axial strain and plastic volumetric strain; S65. According to the fitting curve of the relationship between plastic axial strain and plastic volumetric strain, discretize the pressure stage finitely. Through formula (3), obtain the dilation angle at the corresponding pressure stage, （3） In the formula: is the dilation angle of the rock mass specimen, is the plastic axial strain of the rock mass specimen, is the plastic volumetric strain of the rock mass specimen; S66. According to the dilation angle at the corresponding pressure stage, change the pressure stage to obtain the dilation angle and the variation law of the dilation angle at different pressure stages.

9. An in-situ test system for the dilation angle of rock mass under true stress, which is used to implement the in-situ test method for the dilation angle of rock mass under true stress as described in any one of claims 1-8, is characterized in that, The system includes: The first acquisition module is used to select the test tunnel wall in the underground project and obtain the rock mass specimen and the position information of the rock mass specimen by means of manual chiseling or mechanical cutting; The second acquisition module is used to calculate the stress level required to be applied by the in-situ testing device and the stress cycle path of the in-situ testing device according to the position information of the rock mass specimen through the Hoek-Brown strength criterion; The device installation module is used to install a hydraulic servo module, a lateral pressure loading module, an axial pressure loading module, a deformation measurement module and a control and processing module according to the rock mass specimen to obtain the in-situ testing device for the rock mass specimen; Damage module, which is used to conduct a damage test according to the stress level that needs to be applied by the in-situ test device and input the test data into the damage model for processing to obtain damage information. If the damage information is normal, the data collection module is applied; if the damage information is an alarm, the test is terminated; Data collection module, which is used to conduct a cyclic test through the in-situ test device of the rock mass specimen according to the stress level that needs to be applied by the in-situ test device and the stress cycling path of the in-situ test device, and obtain a pressure data set of the rock mass specimen and a strain data set of the rock mass specimen; Data processing module, which is used to obtain the dilation angle and the variation law of the dilation angle at different pressure stages through the control processing module according to the pressure data set of the rock mass specimen and the strain data set of the rock mass specimen.

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