Physical simulation test method of arch bottom type rock burst induced by deep rectangular cavern under excavation unloading under three-dimensional stress

Abstract

The present application belongs to the field of underground space engineering, and discloses a physical simulation test method for deep rectangular cavern arch bottom type rock burst induced by excavation unloading under three-dimensional stress, comprising: three-dimensional static loading is performed on a cubic rock sample to make the cubic rock sample in an initial three-dimensional ground stress state; a rectangular cavern is formed in the center of the cubic rock sample after real-time drilling unloading of the cubic rock sample is completed by using a Lelos triangle cutting drill bit; after the real-time drilling unloading of the rectangular cavern is completed, a horizontal axial load or a vertical vertical load is applied to the cubic rock sample until rock burst damage phenomenon occurs at the arch bottom or the sidewall of the simulated rectangular cavern; the present application realizes the whole process physical simulation of the rectangular cavern from the initial three-dimensional ground stress balance to the real-time excavation unloading and then to the disturbed stress loading, and provides experimental support for revealing the space-time evolution law of rock burst and optimizing the prevention and control design.

Description

Technical Field

[0001] This invention belongs to the field of underground space engineering technology, and relates to the field of rock mechanics in deep underground engineering. In particular, it relates to a physical simulation test method for rockburst at the bottom of a deep rectangular cavern induced by excavation unloading under three-dimensional stress. Background Technology

[0002] As underground engineering develops towards deeper burial and larger scale, the construction of deep-buried tunnels faces severe challenges from rockburst hazards. In particular, under deep, high-stress environments, the redistribution of stress in the surrounding rock after tunnel excavation can trigger severe brittle failure, making rockbursts a major concern due to their suddenness and high destructiveness. For example, during the construction of a deep-buried railway tunnel, stress concentration at the bottom of the arch caused the track slab to arch beyond the limit, directly threatening the safety of railway operations. However, current rockburst research mainly focuses on the failure of circular tunnels, and there is still a lack of systematic understanding of the inducing conditions, dynamic evolution laws, and prevention and control mechanisms of rockbursts in real-time excavated rectangular tunnels.

[0003] Currently, existing technologies mainly explore the impact of excavation unloading on the stability of surrounding rock through theoretical analysis, three-dimensional loading tests, and numerical simulations. While theoretical analysis and numerical simulations can provide some reference, they lack physical experimental verification under real stress paths. Conventional three-dimensional loading tests, because they do not realize the coupling effect between excavation unloading and stress disturbance, are difficult to reveal the triggering mechanism of rockburst caused by dynamic construction disturbances.

[0004] Specifically, conventional three-dimensional loading tests have the following limitations: (1) The experimental methods are mostly based on prefabricated borehole rock samples, which cannot reflect the real-time excavation unloading effect under the initial three-dimensional stress state of the surrounding rock in actual engineering; (2) Traditional loading methods are mostly static or two-dimensional stress simulations, which are difficult to reproduce the superposition effect of three-dimensional stress dynamic adjustment and horizontal structural stress after the excavation of deep-buried tunnels; (3) There is a lack of research on rockburst simulation for rectangular caverns, while rectangular cross sections are widely used in actual engineering due to their construction convenience. Their stress concentration characteristics are significantly different from those of circular or arched cross sections, especially the arch bottom area is more likely to form a high gradient stress field. Therefore, it is urgent to develop an experimental method that can simulate the three-dimensional initial stress state, real-time excavation unloading and the entire process of subsequent stress disturbance, in order to fill the experimental technology gap in the study of rockburst in rectangular caverns. Summary of the Invention

[0005] To address the technical problems existing in the prior art, this invention provides a physical simulation test method for rockburst at the arch bottom of a deep rectangular cavern induced by excavation unloading under three-dimensional stress. This method solves the technical problem that conventional three-dimensional loading tests fail to realize the coupling effect between excavation unloading and stress disturbance, making it difficult to reveal the triggering mechanism of rockburst caused by dynamic construction disturbance.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a physical simulation test method for rockburst at the arch bottom of a deep rectangular cavern induced by excavation unloading under three-dimensional stress, comprising: Three-dimensional static loading was applied to the cubic rock sample to bring it into an initial three-dimensional geostress state. After the three-dimensional static loading is completed, the cube rock sample is subjected to real-time drilling and unloading of a rectangular cavity using a Reuleaux triangle cutting drill bit to simulate the excavation and unloading process of a rectangular cavity under three-dimensional stress. After the real-time drilling and unloading of the rectangular cavity is completed, a simulated rectangular cavity is formed in the center of the cube rock sample. After the real-time drilling and unloading of the rectangular cavern is completed, a horizontal axial load or a vertical load is applied to the cubic rock sample until the rock burst failure phenomenon of the arch bottom or sidewall of the simulated rectangular cavern occurs.

[0007] Furthermore, the cubic rock sample is subjected to three-dimensional static loading to bring it into an initial three-dimensional geostress state, as follows: Using a true triaxial servo testing machine, horizontal axial load, horizontal lateral load, and vertical load are applied to the cubic rock sample at a predetermined loading rate until the cubic rock sample is in the initial three-dimensional geostress state.

[0008] Furthermore, the true triaxial servo testing machine includes a horizontal axial static hydraulic unit, a vertical static hydraulic unit, and a horizontal lateral static hydraulic unit; A horizontal axial static hydraulic unit is used to apply a horizontal axial load to a cubic rock sample; Vertical static hydraulic unit, used to apply vertical loads to cubic rock samples; A horizontal lateral static hydraulic unit is used to apply horizontal lateral loads to cubic rock samples.

[0009] Furthermore, by using a horizontal axial static hydraulic unit or a vertical static hydraulic unit, a horizontal axial load or a vertical load is applied to a cubic rock sample to simulate tectonic stress disturbance until rockburst failure occurs at the arch bottom or sidewall of the simulated rectangular cavern.

[0010] Furthermore, the true triaxial servo testing machine also includes a dynamic disturbance unit; Using dynamic disturbance units, horizontal axial loads or vertical loads are applied to cubic rock samples to simulate secondary construction disturbances until rockburst failure occurs at the arch bottom or sidewall of the simulated rectangular cavern.

[0011] Furthermore, the axial direction of the simulated rectangular cavity coincides with the direction of the horizontal lateral load applied to the cubic rock sample.

[0012] Furthermore, the rotation axis of the Reuleaux triangle cutting drill bit forms an angle of 5°-15° with the horizontal plane.

[0013] Furthermore, the surface of the cubic rock sample was uniformly coated with lubricant.

[0014] Furthermore, it also includes data analysis steps, including: Record the stress and strain data of the cubic rock sample in the horizontal axis, horizontal lateral direction, and vertical direction during the test, and plot the stress-strain curve of the cubic rock sample. Record the acoustic emission signals of cubic rock samples and video monitoring data of the rockburst damage phenomenon occurring at the arch bottom or sidewall of the simulated rectangular cavern during the experiment, and obtain the temporal and spatial characteristics of the rockburst occurrence at the arch bottom or sidewall of the simulated rectangular cavern.

[0015] Furthermore, the horizontal axial static hydraulic unit, the vertical static hydraulic unit, and the horizontal lateral static hydraulic unit adopt independent control loading or synchronous control loading.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a physical simulation test method for rockburst at the arch bottom of a deep rectangular tunnel induced by excavation unloading under three-dimensional stress. This method achieves a complete physical simulation of the entire process of a rectangular tunnel, from initial three-dimensional geostress equilibrium to real-time excavation unloading and then to disturbance stress loading. It provides crucial experimental support for revealing the spatiotemporal evolution of rockbursts and optimizing prevention and control designs, thereby accurately explaining the triggering mechanism of rockbursts caused by dynamic construction disturbances in rectangular tunnels. Specifically, by applying three-dimensional static loading to cubic rock samples, the initial three-dimensional geostress state of the surrounding rock in deeply buried underground engineering is accurately restored, effectively overcoming the problem that conventional tests based on prefabricated boreholes cannot reflect the real-time excavation unloading effect under initial stress. Secondly, the use of a Reuleaux triangle cutting drill bit enables real-time borehole unloading of the rectangular tunnel, which can... This study realistically simulates the excavation process of rectangular caverns in actual engineering projects, filling the gap in existing research on rockburst simulation of rectangular caverns. It also overcomes the limitations of traditional experiments in reproducing the dynamic adjustment of three-dimensional stress and the superposition of tectonic stress. Finally, by applying horizontal axial or vertical loads, the coupling effect of excavation unloading and stress disturbance is achieved, accurately capturing the rockburst failure process in stress-concentration areas such as the arch bottom and sidewalls of rectangular caverns. This effectively reveals the triggering mechanism of rockburst caused by dynamic construction disturbances, providing realistic and reliable physical experimental support for the study of the induction conditions, evolution laws, and prevention and control measures of rockbursts in deeply buried rectangular cross-section underground engineering. It effectively compensates for the lack of experimental verification under real stress paths in theoretical analysis and numerical simulation. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart of the physical simulation test method provided for the embodiments; Figure 2 This is a top view of the true triaxial servo testing machine and the real-time drilling unloading testing device in the embodiment; Figure 3 for Figure 2 AA cross-section view; Figure 4 This is a schematic diagram of the structure for three-dimensional static loading of a cubic rock sample in the embodiment; Figure 5 This is a side cross-sectional view of a cubic rock sample undergoing real-time rectangular cavity drilling and unloading in the embodiment. Figure 6 This is an axial cross-sectional view of a cubic rock sample undergoing real-time rectangular cavity drilling and unloading in the embodiment. Figure 7 This is a schematic diagram of the Reuleaux triangle cutting drill bit in the embodiment; Figure 8 This is a schematic diagram of the drill bit connecting shaft in the embodiment; Figure 9 This is a schematic diagram of applying a horizontal axial load to a cubic rock sample after real-time borehole decompression is completed in the embodiment.

[0019] Among them, 1 is a true triaxial servo testing machine, 2 is a real-time drilling unloading test device, 3 is a horizontal axial front bearing plate pad, 4 is a horizontal left bearing plate pad, 5 is a vertical upper bearing plate pad, 6 is a horizontal axial rear bearing plate pad, 7 is a vertical lower bearing plate pad, 8 is a horizontal right bidirectional bearing plate pad, 9 is a horizontal right front bearing plate pad, 10 is a horizontal right rear bearing plate pad, 11 is a bearing plate pad connecting four columns, 12 is a cubic rock sample, 13 is a detachable fixed connecting bolt, 14 is a drilling rig, 15 is a rotary gear, 16 is a moving gear rail, 17 is a drill bit clamp, 18 is a Reuleaux triangle cutting drill bit, 19 is an elevation adjustment knob, 20 is a wire lever elevation moving rail, 21 is a drilling rig switch, 22 is a drilling speed regulator, 23 is a drill bit liquid cooling water injection port, 24 is an acoustic emission probe, 25 is a high-speed camera, and 26 is a drill bit connecting shaft; s 1. Horizontal axial static hydraulic unit s 2. Vertical static hydraulic unit s 3 horizontal lateral static hydraulic units, s dDynamic disturbance unit. Detailed Implementation

[0020] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0021] Before describing the specific embodiments of this application, some of the technical terms involved in the embodiments of this application are explained as follows: Deep-buried tunnels refer to tunnels buried at a depth of more than 300 meters.

[0022] A rectangular cavern is an underground engineering structure with a rectangular cross-section.

[0023] Rockburst is a sudden dynamic failure phenomenon in underground engineering, which often occurs in deep areas or areas with high tectonic stress. It is caused by the sudden release of strain energy accumulated in the rock mass, which leads to brittle fracture of the rock mass and ejection of rock fragments.

[0024] The initial three-dimensional geostress state refers to the three-dimensional stress field that exists in the rock mass under natural conditions.

[0025] The Reuleaux triangle cutting drill bit is a special drill bit designed based on the Reuleaux triangle (a constant width curve). Its working principle is to utilize the property that the Reuleaux triangle maintains a constant width during rotation, forming a square hole through the area traversed by the three vertices; it can drill square holes with rounded corners.

[0026] This invention provides a physical simulation test method for rockburst at the arch bottom of a deep rectangular cavern induced by excavation unloading under three-dimensional stress, comprising the following steps: Step 100: Perform three-dimensional static loading on the cubic rock sample 12 to bring the cubic rock sample 12 into the initial three-dimensional geostress state.

[0027] Step 200: After the three-dimensional static loading is completed, the Reuleaux triangle cutting drill bit 18 is used to perform real-time drilling and unloading of the rectangular cavity on the cubic rock sample 12 to simulate the excavation and unloading process of the rectangular cavity under three-dimensional stress. After the real-time drilling and unloading of the rectangular cavity is completed, a simulated rectangular cavity is formed in the center of the cubic rock sample 12.

[0028] Step 300: After the real-time drilling and unloading of the rectangular cavern is completed, apply a horizontal axial load or a vertical load to the cubic rock sample 12 until the simulated rockburst failure phenomenon occurs at the arch bottom or sidewall of the rectangular cavern.

[0029] In the above embodiments, the cubic rock sample 12 is first placed in a real initial three-dimensional geostress state by three-dimensional static loading, and then the Reuleaux triangle cutting drill bit 18 is used to realize real-time drilling unloading of the rectangular tunnel. This effectively avoids the limitation that prefabricated holes in conventional tests cannot reflect the actual excavation process, and allows the surrounding rock to complete the unloading response while maintaining the three-dimensional stress field, thereby realistically reproducing the complete stress path of loading, excavation, and disturbance at the engineering site. On this basis, applying horizontal axial loads or vertical loads can simulate the superposition of subsequent construction disturbances and structural stresses, so as to accurately trigger rockburst failure at the arch bottom or sidewalls, effectively revealing the triggering mechanism of dynamic construction disturbances on rockbursts, and providing reliable physical experimental basis for the prediction and prevention of rockburst disasters in rectangular cross-section tunnels.

[0030] The following specific embodiments further explain the physical simulation test method for deep rectangular cavern arch-bottom rockburst induced by excavation unloading under three-dimensional stress provided by the present invention: Example This embodiment provides a physical simulation test method for inducing rockburst at the arch bottom of a deep rectangular cavern under three-dimensional stress excavation unloading, which is used to realistically simulate the rockburst phenomenon induced during the excavation unloading process of a rectangular cavern. Specifically, the test method is conducted using a true triaxial servo testing machine 1 and a real-time drilling unloading test device 2. The true triaxial servo testing machine 1 is used to apply three-dimensional static loading or disturbance load to a cubic rock sample 12; the real-time drilling unloading test device 2 is used to perform real-time drilling unloading of the cubic rock sample 12 in a rectangular cavern to simulate the excavation unloading process of a rectangular cavern under three-dimensional stress.

[0031] As attached Figure 2-3 As shown, the true triaxial servo testing machine 1 includes a horizontal axial front bearing plate pad 3, a horizontal left-side bearing plate pad 4, a vertical upward bearing plate pad 5, a horizontal axial rear bearing plate pad 6, a vertical downward bearing plate pad 7, a horizontal right-side bidirectional bearing plate pad 8, and a horizontal axial static hydraulic unit. s 1. Vertical static hydraulic unit s 2 and horizontal lateral static hydraulic unit s 3.

[0032] The horizontal axial front bearing plate pad 3, the horizontal left-side bearing plate pad 4, the vertical upward bearing plate pad 5, the horizontal axial rear bearing plate pad 6, the vertical downward bearing plate pad 7, and the horizontal right-side bidirectional bearing plate pad 8 together form a loading frame with a hollow cavity; wherein, the loading frame serves as a space to accommodate the cubic rock sample 12, so as to realize the installation and fixation of the cubic rock sample.

[0033] The horizontal axial front bearing plate pad 3 and the horizontal axial rear bearing plate pad 6 are parallel to each other and spaced apart. The horizontal left bearing plate pad 4 and the horizontal right bidirectional bearing plate pad 8 are parallel to each other and spaced apart. The vertical upper bearing plate pad 5 and the vertical lower bearing plate pad 7 are parallel to each other and spaced apart.

[0034] Optionally, the horizontal right-side bidirectional bearing plate pad 8 includes a horizontal right-side forward bearing plate pad 9, a horizontal right-side backward bearing plate pad 10, and a bearing plate pad connecting four columns 11; the horizontal right-side forward bearing plate pad 9 and the horizontal right-side backward bearing plate pad 10 are parallel to each other and spaced apart; the horizontal axial forward bearing plate pad 3, the horizontal left-side bearing plate pad 4, the vertical upward bearing plate pad 5, the horizontal axial backward bearing plate pad 6, the vertical downward bearing plate pad 7, and the horizontal right-side forward bearing plate pad 8 are also included. The pressure plate pads 9 enclose a hollow cubic chamber to support the cubic rock sample 12 and meet the static loading requirements of the cubic rock sample 12. The pressure plate pad connecting four columns 11 are set between the horizontal right-side forward pressure plate pad 9 and the horizontal right-side backward pressure plate pad 10. One end of the pressure plate pad connecting four columns 11 is connected to the horizontal right-side forward pressure plate pad 9, and the other end of the pressure plate pad connecting four columns 11 is connected to the horizontal right-side backward pressure plate pad 10.

[0035] Horizontal Axial Static Hydraulic Unit s 1. Set at the center of the outer side of the horizontal axial front bearing plate pad 3 or the horizontal axial rear bearing plate pad 6, for applying horizontal axial load to the cubic rock sample 12; Vertical static hydraulic unit s 2. Located at the center of the outer side of the vertically upward bearing plate pad 5 or the vertically downward bearing plate pad 7, used to apply vertical loads to the cubic rock sample 12; Horizontal lateral static hydraulic unit s 3. Set at the outer center of the horizontal left-side bearing plate pad 4 or the horizontal right-side bidirectional bearing plate pad 8, for applying horizontal lateral loads to the cubic rock sample 12; wherein, when the horizontal lateral static hydraulic unit s 3. When the horizontal right-side bidirectional pressure plate pad 8 is set at the outer center, the horizontal lateral static hydraulic unit needs to be... s 3 is placed at the right center of the horizontal right-backward bearing plate pad 10, so as to apply a horizontal lateral load to the horizontal right-backward bearing plate pad 10, and then transfer it to the cubic rock sample 12 through the bearing plate pad connecting the four columns 11 and the horizontal right forward bearing plate pad 9, thereby realizing the application of a horizontal lateral load to the cubic rock sample 12.

[0036] Optionally, a horizontal axial static hydraulic unit s 1. Vertical static hydraulic unit s 2 and horizontal lateral static hydraulic unit s3. Independent or synchronous control loading is employed, capable of applying static loads at different rates and dynamic loads at different frequencies; among which, the horizontal axial static hydraulic unit... s 1. Vertical static hydraulic unit s 2 and horizontal lateral static hydraulic unit s The maximum applied load of the three is 3000kN, and each is equipped with an extensometer with a maximum range of 5mm, thus meeting the requirements for simulating rockburst tests under different tunnel burial depths.

[0037] It should be noted that the horizontal axial front bearing plate pad 3, the horizontal left bearing plate pad 4, the horizontal axial rear bearing plate pad 5, and the horizontal right forward bearing plate pad 9 are all provided with a central through hole. The central through holes on the horizontal axial front bearing plate pad 3, the horizontal left bearing plate pad 4, the horizontal axial rear bearing plate pad 6, and the horizontal right forward bearing plate pad 9 serve as the installation space for the acoustic emission probe; the central through hole on the horizontal right forward bearing plate pad 9 is also used as an operating channel for real-time drilling unloading and as the installation space for the high-speed camera.

[0038] As attached Figure 2-3 As shown, the real-time drilling unloading test device 2 is set between the horizontal right-side forward bearing plate pad 9 and the horizontal right-side backward bearing plate pad 10, and is detachably installed on the bearing plate pad connecting four columns 11 by a detachable fixing bolt 13, so as to facilitate the installation and disassembly of the real-time drilling unloading test device 2.

[0039] The real-time drilling unloading test device 2 includes a drilling rig 14, a rotating gear 15, a moving gear rail 16, a Reuleaux triangular cutting drill bit 18, and a wire lever elevation moving track 20. The wire lever elevation moving track 20 is vertically mounted on the bearing plate pad connecting four-column 11, and the wire lever elevation moving track 20 and the bearing plate pad connecting four-column 11 are detachably connected by a detachable fixing bolt 13. The moving gear rail 16 is horizontally movable and mounted on the wire lever elevation moving track 20, and the axis of the moving gear rail 16 is aligned with that of the cubic rock sample 1. 2. The direction of the applied horizontal lateral load is parallel; wherein, the end of the moving toothed rail 16 is provided with an elevation adjustment knob 19, which is used to adjust the position height of the moving toothed rail 169 on the wire lever elevation moving track 20, so as to adjust the position height of the drilling rig 14, and ensure that the Reuleaux triangle cutting drill bit 18 and the center through hole of the horizontal left-side bearing plate pad 4 and the horizontal right-side forward bearing plate pad 9 are kept at the same level and center, thereby realizing the real-time drilling unloading process of the center inside the cubic rock sample 12, simulating the excavation effect of the rectangular cavern.

[0040] The drilling rig 14 is movably mounted on the moving gear rail 16 via a rotating gear 15; preferably, the rotating gear 15 is an electrically controlled gear, used to drive the drilling rig 14 to move horizontally along the moving gear rail 16; the Reuleaux triangular cutting drill bit 18 is mounted on the front end of the drilling rig 21 via a drill bit chuck 17, and is positioned near the horizontal right side of the forward bearing plate pad 9; wherein, the drill bit chuck 17 is a variable diameter drill bit chuck to meet the clamping function of the Reuleaux triangular cutting drill bit 18 with a diameter of 0-30mm; the drill bit chuck 17 is equipped with a drill bit liquid cooling water inlet 23, used to provide effective cooling for the Reuleaux triangular cutting drill bit 18; the axial direction of the Reuleaux triangular cutting drill bit 18 coincides with the direction of the horizontal lateral load applied to the cubic rock sample 12, and the rotation center axis of the Reuleaux triangular cutting drill bit 18 forms an angle of 5°-15° with the horizontal plane.

[0041] It should be noted that the Reuleaux triangle cutting drill bit 18, due to its constant width characteristic, can reduce offset and improve positioning accuracy during rotary cutting; the Reuleaux triangle cutting drill bit 18 is equipped with a drill bit linking shaft 26, which is used to enable the Reuleaux triangle cutting drill bit 18 to accurately cut rectangular holes, as shown in the attached figure. Figure 7-8 As shown.

[0042] Optionally, the drilling rig 14 is equipped with a drilling rig switch 21 and a drilling speed regulator 22; the drilling rig switch 21 is used to control the opening or closing of the drilling rig 14, and the drilling speed regulator 22 is used to adjust the output drilling speed of the drilling rig 14; preferably, the drilling rig 14 adopts a CNC servo motor of model SG4500 with a maximum power of 4500W; the drilling speed regulator 22 has an adjustment range of 0-800r / min, and features small size, high power, and adjustable speed, which can meet the space requirements of the true triaxial servo testing machine 1.

[0043] As attached Figure 1 As shown in this embodiment, the physical simulation test method for deep rectangular cavern arch-bottom rockburst induced by excavation unloading under three-dimensional stress includes the following steps: Step 1: Prepare a cubic rock sample 12 and install and fix the cubic rock sample 12 within the loading frame of the true triaxial servo testing machine 1. Specifically, the implementation process is as follows: Step 11: Obtain the original rock sample from the construction site and process the original rock sample into a rock sample of a preset size to obtain a cubic rock sample 12; wherein, the preset size is, for example, length × width × height = 100mm × 100mm × 100mm.

[0044] Step 12: Apply lubricant to the surface of the cubic rock sample 12, and then install the cubic rock sample 12 with lubricant evenly applied to its surface into the loading frame of the true triaxial servo testing machine 1; wherein, the lubricant is, for example, grease or petroleum jelly; optionally, simultaneously attach acoustic emission probes 24 into the central through holes of the horizontal axial front bearing plate pad 3 and the horizontal axial rear bearing plate pad 6 and at the center of the cubic rock sample 12 to record the acoustic emission signal during the three-dimensional static loading process.

[0045] Specifically, the cubic rock sample 12 is installed inside the hollow cavity of the loading frame and is in close contact with all four sides of the loading frame; the specific installation procedure for the cubic rock sample 12 is as follows: First, install the horizontal axial rear-side pressure plate pad 6, the vertical upward-side pressure plate pad 5, the vertical downward-side pressure plate pad 7, the horizontal left-side pressure plate pad 4, and the horizontal right-side bidirectional pressure plate pad 8, thus forming a loading frame with an open front end. Then, place the cubic rock sample 12 within the loading frame with the open front end. Finally, install the horizontal axial front-side pressure plate pad 3 to complete the installation and fixing of the cubic rock sample 12. At this point, the front end face of the cubic rock sample 12 is in contact with the horizontal axial front-side pressure plate pad 3, the left end face of the cubic rock sample 12 is in contact with the horizontal left-side pressure plate pad 4, the top surface of the cubic rock sample 12 is in contact with the vertical upward-side pressure plate pad 5, the rear end face of the cubic rock sample 12 is in contact with the horizontal axial rear-side pressure plate pad 6, the bottom surface of the cubic rock sample 12 is in contact with the vertical downward-side pressure plate pad 7, and the right end face of the cubic rock sample 12 is in contact with the left end face of the horizontal right-side forward-side pressure plate pad 9.

[0046] Step 2: Perform three-dimensional static loading on the cubic rock sample 12 to bring it to an initial three-dimensional geostress state. Specifically, using a true triaxial servo testing machine 1, apply horizontal axial load, horizontal lateral load, and vertical load to the cubic rock sample 12 at a predetermined loading rate until the cubic rock sample 12 is in an initial three-dimensional geostress state, as shown in the attached figure. Figure 4 As shown.

[0047] The more detailed implementation process is as follows: In the control program of the true triaxial servo testing machine 1, the horizontal axis static hydraulic unit is set. s 1. Vertical static hydraulic unit s 3. Horizontal lateral static hydraulic unit s3. Apply horizontal axial load, horizontal lateral load, and vertical load to the cubic rock sample 12 at a predetermined loading rate until the target load value is reached, so that the cubic rock sample 12 is in the initial three-dimensional geostress state, thereby accurately reproducing the actual three-dimensional stress state of the surrounding rock before the construction of the rectangular cavern, effectively overcoming the defect that existing indoor physical simulation tests cannot truly reproduce the stress environment of deep rocks; wherein, the predetermined loading rate is, for example, 0.1 MPa / s; for example, taking the stress condition at a burial depth of 1000m as an example, the target load value corresponding to the horizontal axial load is 38.8 MPa, the target load value corresponding to the horizontal lateral load is 18.7 MPa, and the target load value corresponding to the vertical load is 23.6 MPa.

[0048] Step 3: After the three-dimensional static loading is completed, the Reuleaux triangle cutting drill bit 18 is used to drill a rectangular cavity in real time to unload the cubic rock sample 12, so as to simulate the excavation and unloading process of the rectangular cavity under three-dimensional stress. After the real-time drilling and unloading of the rectangular cavity is completed, a simulated rectangular cavity is formed in the center of the cubic rock sample 12.

[0049] Specifically, the experimental process is as follows: First, the real-time drilling unloading test device 2 is installed on the bearing plate pad block connecting four columns 11 through the detachable fixed link 13. At the same time, the internal excavation unloading diameter of the cubic rock sample 12 is determined, and the corresponding Reuleaux triangular cutting drill bit 18 is selected, such as a Reuleaux triangular cutting drill bit with a diameter of 25mm.

[0050] Next, by rotating the elevation adjustment knob 19, the entire drilling rig 14 is adjusted to a suitable height via the wire lever elevation movement track 20, ensuring that the Reuleaux triangle cutting drill bit 18 is level with the center holes of the horizontal left-side bearing plate pad 4 and the horizontal right-side forward bearing plate pad 9.

[0051] Next, the drill rig 14 is controlled to move forward via the rotating gears 15 on both sides and the moving toothed rail 16, until the Reuleaux triangle cutting drill bit 18 passes through the center through hole of the horizontal right-side forward bearing plate 9, approaching the cubic rock sample 12 under the initial three-dimensional geostress state; the drill rig switch 21 is activated, and the drilling speed regulator 22 is adjusted to the predetermined drill speed, such as 800 r / min. Simultaneously, the drill bit liquid cooling water injection port 23 is opened for liquid cooling, and then real-time drilling unloading simulation of deep-buried rectangular tunnel excavation unloading is performed, as shown in the attached figure. Figure 5-6 As shown.

[0052] Step 4: After the real-time drilling and unloading of the rectangular cavern is completed, apply a horizontal axial load or a vertical load to the cubic rock sample 12 until a rockburst failure is simulated at the arch bottom or sidewalls of the rectangular cavern. Specifically, a horizontal axial static hydraulic unit is used. s 1 or vertical static hydraulic unit s 2. Apply horizontal axial loads or vertical loads to cubic rock sample 12 to simulate tectonic stress disturbances until rockburst failure occurs at the arch bottom or sidewall of the simulated rectangular cavern.

[0053] Optionally, the true triaxial servo testing machine 1 also includes a dynamic disturbance unit. s d ; Utilizing dynamic disturbance units s d A horizontal axial load or a vertical load is applied to the cubic rock sample 12 to simulate secondary construction disturbance until rockburst failure occurs at the arch bottom or sidewall of the simulated rectangular cavern.

[0054] More specifically, the implementation process is as follows: After the real-time drilling and unloading test device 2 is completed according to the set target drilling depth, the drilling rig 14 is controlled to rotate the toothed rail 15 to completely withdraw the Reuleaux triangular cutting drill bit 18 to the outside of the cubic rock sample 12, and then withdraw the real-time drilling and unloading test device 2. At this time, the cubic rock sample 12 forms a rock sample containing simulated rectangular holes, as shown in the attached figure. Figure 6 As shown; where the axis of the simulated rectangular cavity coincides with the direction of the horizontal lateral load applied to the cubic rock sample 12.

[0055] Then, a high-speed camera 25 is installed in the center through hole of the forward bearing plate pad 9 on the horizontal right side.

[0056] Then, using a horizontal axial static hydraulic unit s 1 or dynamic disturbance unit s d A horizontal axial load was applied to cubic rock sample 12 at a predetermined loading rate of 0.1 MPa / s or a disturbance frequency of 50 Hz, as shown in the attached figure. Figure 9 As shown, an acoustic emission probe 24 and a high-speed camera 25 are used simultaneously to monitor the acoustic emission signal characteristics and video images of the entire process of rockburst damage at the bottom of the rectangular tunnel arch, in order to simulate the rockburst induced at the bottom of the rectangular tunnel under the influence of horizontal stress after the excavation and unloading of the deep buried rock mass.

[0057] Step 5: Data Analysis. Specifically, record the stress and strain data of the cubic rock sample 12 in the horizontal axial direction, horizontal lateral direction, and vertical direction during the experiment, and plot the stress-strain curve of the cubic rock sample 12; record the acoustic emission signal of the cubic rock sample 12 and the video monitoring data of the rockburst failure phenomenon of the arch bottom or sidewall of the simulated rectangular cavern during the experiment, and obtain the temporal and spatial characteristics of the rockburst occurrence at the arch bottom or sidewall of the simulated rectangular cavern.

[0058] Interpretive analysis was conducted by plotting stress-strain curves based on the load and strain in the horizontal axial, horizontal lateral, and vertical directions recorded by the monitoring. The acoustic emission signals from the monitoring were compiled and combined with video recordings from high-speed cameras to analyze the temporal and spatial characteristics of rockbursts at the bottom of rectangular tunnel arches, so as to comprehensively analyze the mechanism of rockbursts at the bottom of rectangular tunnel arches induced by horizontal load disturbance after rock excavation and unloading.

[0059] A stress acquisition unit installed on the true triaxial servo testing machine 1 was used to record the stress data of the cubic rock sample 12 in the horizontal axial direction, horizontal lateral direction, and vertical direction during the test. An extensometer or strain acquisition instrument installed on the true triaxial servo testing machine 1 was used to record the strain data of the cubic rock sample 12 in the horizontal axial direction, horizontal lateral direction, and vertical direction during the test. An acoustic emission probe 24 was used to record the acoustic emission signal of the cubic rock sample 12 during the test. A high-speed camera 6 was used to record the video monitoring data of the simulated rockburst failure phenomenon at the bottom of the arch of the hole.

[0060] It is worth noting that the acoustic emission probe 24 is affixed to the surface of the rock sample within the central through-holes of the horizontal axial front bearing plate pad 3 and the horizontal axial rear bearing plate pad 6; the lead wire of the acoustic emission probe 24 is led out through the central through-hole of the bearing plate pad; when installing the acoustic emission probe 24, a coupling agent such as Vaseline is required to firmly adhere it to the surface of the rock sample, and a lead breakage test is performed on the rock surface before the test to ensure stable transmission of the acoustic emission signal during the test, thereby enabling the acquisition and recording of acoustic emission data of crack propagation during sample loading; the high-speed camera 25 is installed in the central through-hole of the horizontal right-side forward bearing plate pad 9 to monitor and record the entire process of rockburst induced at the bottom of the arch under the influence of the maximum horizontal principal stress after the rock is unloaded by real-time three-dimensional stress drilling.

[0061] The physical simulation test method for deep rectangular cavern arch-bottom rockburst induced by excavation unloading under three-dimensional stress described in this embodiment utilizes the constant width characteristic of the Reuleaux triangle cutting drill bit to suppress borehole deflection and achieve high-precision excavation of rectangular cross-sections. Secondly, the method can achieve triaxial-borehole collaborative control. Specifically, the mechanical coupling design of the loading frame and the borehole device ensures the stability of dynamic unloading under high confining pressure. In addition, it can be set to support multi-mode disturbance loading, such as supporting static (structural stress simulation) and dynamic (construction disturbance simulation) composite loading modes. Furthermore, it can integrate cross-scale monitoring methods, that is, integrate macro-micro observation means such as strain field, acoustic emission, and crack propagation images to reveal the multi-scale disaster mechanism of rockburst. At the same time, it can realize the physical simulation of the entire process of rectangular cavern from initial geostress equilibrium to real-time excavation unloading and then to disturbance stress loading, filling the experimental technology gap in the study of rockburst in rectangular caverns and providing key experimental support for the study of rockburst mechanism in deep rock masses rectangular caverns.

[0062] The physical simulation test method for rockburst at the arch bottom of a deep rectangular cavern induced by excavation unloading under three-dimensional stress described in this invention uses a Reuleaux triangle cutting drill bit for precise control to reproduce the progressive unloading effect of rectangular cross-section excavation. Combined with horizontal / vertical axial static loading units, it simulates the triggering effect of tectonic stress or secondary construction disturbance on the arch bottom rockburst, providing key experimental support for revealing the spatiotemporal evolution law of rockburst and optimizing prevention and control design.

[0063] This invention combines a true triaxial servo testing machine and a real-time drilling unloading testing device to achieve a full-process physical simulation of a rectangular tunnel, from initial stress equilibrium, real-time excavation unloading, and disturbance stress loading. Specifically, the precise control of the Reuleaux triangle cutting drill bit allows for the replication of the progressive unloading effect during rectangular section excavation. Compared to the circular drill bits used in existing technologies, the Reuleaux triangle drill bit offers the following advantages: a 30% reduction in single-rotation cutting area, better reflecting the progressive unloading characteristics in actual engineering; a constant width characteristic that reduces drill bit deflection error by up to 45%; and the formation of a stress concentration guidance zone at the triangle apex, precisely controlling the initial fracture location. Finally, combined with horizontal / vertical axial static loading units, the triggering effect of tectonic stress or secondary construction disturbances on rockburst at the tunnel base can be simulated, providing crucial experimental support for revealing the spatiotemporal evolution of rockburst induced by real-time excavation in deeply buried rectangular tunnels and optimizing prevention and control design.

[0064] The above embodiments are merely one of the implementation methods for achieving the technical solution of the present invention. The scope of protection claimed by the present invention is not limited to this embodiment, but also includes any variations, substitutions and other implementation methods that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention.

Claims

1. A physical simulation test method for rockburst at the arch bottom of a deep rectangular cavern induced by excavation unloading under three-dimensional stress, characterized in that, include: Three-dimensional static loading was applied to the cubic rock sample (12) to bring it into an initial three-dimensional geostress state; After the three-dimensional static loading is completed, the Reuleaux triangle cutting drill bit (18) is used to drill and unload the rectangular cavity in real time on the cubic rock sample (12) to simulate the excavation and unloading process of the rectangular cavity under three-dimensional stress. After the real-time drilling and unloading of the rectangular cavity is completed, a simulated rectangular cavity is formed in the center of the cubic rock sample (12). After the real-time drilling and unloading of the rectangular cavern is completed, a horizontal axial load or a vertical load is applied to the cubic rock sample (12) until the arch bottom or sidewall of the simulated rectangular cavern is damaged by rock burst.

2. The physical simulation test method for inducing rockburst at the arch bottom of a deep rectangular cavern under three-dimensional stress excavation and unloading as described in claim 1, characterized in that, The process of subjecting the cubic rock sample (12) to three-dimensional static loading to bring it to an initial three-dimensional geostress state is as follows: Using a true triaxial servo testing machine (1), a horizontal axial load, a horizontal lateral load, and a vertical load are applied to a cubic rock sample (12) at a predetermined loading rate until the cubic rock sample (12) is in the initial three-dimensional geostress state.

3. The physical simulation test method for inducing rockburst at the arch bottom of a deep rectangular cavern under three-dimensional stress excavation unloading as described in claim 2, characterized in that, The true triaxial servo testing machine (1) includes a horizontal axial static hydraulic unit ( σ 1) Vertical static hydraulic unit ( σ 2) and horizontal lateral static hydraulic unit ( σ 3); Horizontal axial static hydraulic unit ( σ 1), used to apply a horizontal axial load to a cubic rock sample (12); Vertical static hydraulic unit ( σ 2), used to apply a vertical load to the cubic rock sample (12); Horizontal static hydraulic unit ( σ 3), used to apply horizontal lateral loads to cubic rock samples (12).

4. The physical simulation test method for inducing rockburst at the arch bottom of a deep rectangular cavern under three-dimensional stress excavation unloading as described in claim 2, characterized in that, Using a horizontal axial static hydraulic unit ( σ 1) or vertical static hydraulic unit ( σ 2) Apply horizontal axial load or vertical load to cubic rock sample (12) to simulate tectonic stress disturbance until rockburst failure occurs at the arch bottom or sidewall of the simulated rectangular cavern.

5. The physical simulation test method for inducing rockburst at the arch bottom of a deep rectangular cavern under three-dimensional stress excavation unloading as described in claim 4, characterized in that, The true triaxial servo testing machine (1) also includes a dynamic disturbance unit ( σ d ); Using dynamic disturbance unit ( σ d Apply horizontal axial loads or vertical loads to cubic rock samples (12) to simulate secondary construction disturbances until rockburst damage occurs at the arch bottom or sidewall of the simulated rectangular cavern.

6. The physical simulation test method for rockburst at the arch bottom of a deep rectangular cavern induced by excavation unloading under three-dimensional stress, as described in claim 2, is characterized in that... The axial direction of the simulated rectangular cavity coincides with the direction of the horizontal lateral load applied to the cubic rock sample (12).

7. The physical simulation test method for inducing rockburst at the arch bottom of a deep rectangular cavern under three-dimensional stress excavation unloading as described in claim 1, characterized in that, The rotation center axis of the Reuleaux triangle cutting drill bit (18) forms an angle of 5°-15° with the horizontal plane.

8. The physical simulation test method for inducing rockburst at the arch bottom of a deep rectangular cavern under three-dimensional stress excavation unloading as described in claim 1, characterized in that, The surface of the cubic rock sample (12) was uniformly coated with lubricant.

9. The physical simulation test method for inducing rockburst at the arch bottom of a deep rectangular cavern under three-dimensional stress excavation unloading as described in claim 1, characterized in that, It also includes data analysis steps, including: Record the stress and strain data of the cube rock sample (12) in the horizontal axis, horizontal lateral direction and vertical direction during the test, and plot the stress-strain curve of the cube rock sample (12); Record the acoustic emission signal of the cubic rock sample (12) and the video monitoring data of the rockburst damage phenomenon of the arch bottom or sidewall of the simulated rectangular cavern during the experiment, and obtain the temporal and spatial characteristics of the rockburst occurrence at the arch bottom or sidewall of the simulated rectangular cavern.

10. The physical simulation test method for inducing rockburst at the arch bottom of a deep rectangular cavern under three-dimensional stress excavation unloading as described in claim 3, characterized in that, Horizontal axial static hydraulic unit ( σ 1) Vertical static hydraulic unit ( σ 2) and horizontal lateral static hydraulic unit ( σ 3) Use independent control loading or synchronous control loading.

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