A method for unloading and absorbing dangerous situations in high stress areas of coal mine tunnels

Abstract

The present invention relates to the technical field of safe mining of coal mines, and discloses a method for unloading, transferring and absorbing danger in high-stress areas of coal mine tunnels, comprising the following steps: Step 1, pressure relief stage: constructing a drilling hole in the high-stress area of ​​the tunnel to form a pressure relief channel; Step 2, transfer stage: transferring stress to the deep part of the coal rock mass through the layout of the drilling hole; Step 3, energy absorption stage: installing an energy absorption device in the drilling hole, the device comprising an outer steel pipe, an inner polymer material and a monitoring element, the diameter of the drilling hole in Step 1 is 50 to 150 mm, the depth is 5 to 20 m, and the drilling process is constructed using a one-time drilling process. The drilling holes are arranged in a high-stress concentration area 6 to 20 m away from the tunnel surface and are spaced apart along the axial direction of the tunnel. By constructing a three-stage synergistic system of pressure relief, transfer and energy absorption, dynamic regulation of the stress of the tunnel surrounding rock is achieved throughout the entire process, effectively solving the problem of uncontrollable pressure relief effect caused by unclear stress transfer path in the prior art.

Description

Technical Field

[0001] The invention relates to the technical field of safe mining of coal mines, in particular to a method for unloading and absorbing hazards in a high stress zone of a coal mine tunnel. Background Art

[0002] Existing tunnel stress control technologies suffer from systemic flaws. Traditional pressure relief methods rely on dense drilling to disrupt the rock mass structure. While this method can provide short-term stress relief, it suffers from a high rate of borehole collapse, and frequent drilling leads to repeated disturbance of the surrounding rock. More seriously, this passive pressure relief method lacks an energy-guiding mechanism, potentially inducing secondary stress concentrations. Existing technologies fail to establish effective stress migration pathways, resulting in a rapid decline in pressure relief effectiveness as the tunnel extends.

[0003] Current stress transfer technologies suffer from uncontrollable paths. When using directional drilling to guide stress migration, the lack of precise spatial layout design results in a highly dispersed stress conduction path. Drilling clusters exhibit poor synergy, resulting in inefficient energy transfer and an inability to establish a sustained and stable stress release path. Existing solutions lack theoretical guidance for key parameters such as drill hole inclination and spacing, leading to deviations in the stress transfer direction from the intended target area.

[0004] Conventional energy-absorbing support technology suffers from a single structural function. Traditional anchor support systems provide only rigid constraints and are unable to effectively dissipate impact energy. While some solutions have attempted to incorporate damping materials, the material-structure interface is poorly matched, making decoupling failure prone to occur under dynamic loads. Existing energy-absorbing devices lack real-time monitoring and feedback mechanisms, making it impossible to dynamically adjust their energy absorption characteristics based on surrounding rock conditions, resulting in insufficient long-term stability. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the present invention provides a method for unloading and absorbing stress in high-stress areas of coal mine tunnels, which solves the problem of uncontrollable pressure relief effect caused by unclear stress transfer path.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: A method for unloading and absorbing high stress areas in coal mine tunnels, comprising the following steps:

[0007] Step 1, pressure relief stage: drilling holes in high stress areas of the roadway to form pressure relief channels;

[0008] Step 2, transfer stage: transferring stress to the deep part of coal and rock mass through the layout of the drill holes;

[0009] Step 3, energy absorption stage: installing an energy absorption device in the borehole, the device comprising an outer steel pipe, an inner polymer material and a monitoring element.

[0010] Furthermore, tunnel stress regulation is achieved through the synergistic effect of three stages: pressure relief, transfer, and energy absorption. The drilled channels constructed during the pressure relief stage not only release local stress but also provide a physical carrier for subsequent energy transfer. During the transfer stage, the spatial layout of the drilled holes establishes a stress conduction path. During the energy absorption stage, the composite structure deployed achieves dynamic energy management, forming a complete technical chain: stress release, energy transfer, and system stabilization.

[0011] Preferably, the diameter of the drill hole in step 1 is 50 to 150 mm, the depth is 5 to 20 m, and the hole is constructed using a one-time drilling process. The drill holes are arranged in a high stress concentration area 6 to 20 m away from the tunnel surface and are spaced apart along the axial direction of the tunnel.

[0012] Furthermore, a combination of large-diameter drilling (50-150 mm) and deep-hole construction (5-20 m) was used to create a three-dimensional pressure relief network in the high-stress concentration zone, 6-20 m from the roadway surface. This single-hole drilling process avoids multiple disturbances of the rock mass, and the axially spaced arrangement ensures complete coverage of the pressure relief zone.

[0013] Preferably, the drilling axis in step 2 forms an angle of 5° to 30° with the normal line of the tunnel section, the drilling group is radially distributed, the angle between adjacent drilling holes is 10° to 15°, and the drilling end points to the low stress area deep in the coal rock mass.

[0014] Furthermore, the drill holes are radially distributed at inclinations of 5° to 30°, with adjacent holes angled at 10° to 15° to form stress conduction sectors. The spatial arrangement of the drill holes, with their tips pointing toward deep, low-stress zones, creates a clearly defined energy migration pathway.

[0015] Preferably, the outer steel pipe in step 3 is a seamless Q235 steel pipe with a wall thickness of 3 to 8 mm and an inner surface roughened by sandblasting, and the polymer material is an ultra-high molecular weight polyethylene rod.

[0016] Furthermore, seamless Q235 steel pipes and ultra-high molecular weight polyethylene rods form a rigid-flexible composite structure. The steel pipe's inner surface is sandblasted to enhance interfacial friction, while the polyethylene rods' diameters are designed to allow for deformation. This structure combines rigid support with elastic energy storage.

[0017] Preferably, the outer diameter of the polyethylene rod is 0.5-1.5 mm smaller than the inner diameter of the steel pipe, and the rod length is 10-20 cm longer than the steel pipe. During installation, the rod is pressed into the steel pipe by a hydraulic pre-pressing machine so that the rod forms friction contact with the pipe wall.

[0018] Furthermore, hydraulic preloading ensures controlled friction between the rod and the pipe wall, while a length margin is designed to compensate for material creep. This assembly method ensures initial tightness while providing a buffer for subsequent deformation.

[0019] Preferably, the monitoring elements in step 3 include resistance strain gauges and fiber grating sensors, which are arranged in a group 0.5m along the axial direction of the polyethylene rod. The sensor signal line is led out through the reserved hole in the side wall of the steel pipe and connected to the data acquisition terminal in the tunnel.

[0020] Furthermore, a composite sensing network of resistance strain gauges and fiber Bragg grating sensors enables multi-parameter acquisition of material strain states. Sidewall pre-reserved holes for wire threading ensure reliable signal transmission, providing real-time data support for stress evolution analysis.

[0021] Preferably, in step 3, flanges are welded at both ends of the steel pipe, and the end covers are connected and sealed by high-strength bolts. A grouting hole is provided in the center of the end cover, and a high-pressure grouting pipe is pre-buried in the hole.

[0022] Furthermore, the flange end cap and high-strength bolts form a removable seal, and the pre-buried grouting hole pipe design enables secondary filling of the drilled hole gap. This structure not only ensures the integrity of the device, but also enhances the coupling between the surrounding rock and the device.

[0023] Preferably, the drill holes are arranged in 3 to 5 layers according to the tunnel section, the distance between the drill holes in each layer is 3 to 5 times the hole diameter, the upper drill holes are 0.5 to 1.5 m away from the tunnel roof, and the lower drill holes are 1.0 to 2.0 m away from the bottom plate.

[0024] Furthermore, a tiered arrangement of 3 to 5 drill holes combined with a plum blossom array creates a three-dimensional stress control network. Controlled top and bottom plate spacing allows for targeted treatment of different rock formations, while a multi-aperture combination enhances synergistic pressure relief.

[0025] Preferably, the drilling construction is implemented using an intelligent drilling rig, which is equipped with a drilling parameter monitoring module to monitor the drilling speed, torque and vibration frequency in real time and dynamically adjust the drilling parameters according to the monitoring data.

[0026] Furthermore, the drilling parameter monitoring module collects key parameters such as axial thrust and rotational torque in real time, dynamically adjusting drilling speed and feed pressure. This intelligent control mechanism ensures accurate drilling trajectory and avoids the blindness of traditional drilling.

[0027] Preferably, after the energy absorbing device is installed in step 3, the gap between the drill hole and the device is filled by a grouting process.

[0028] Furthermore, the grouting filling process forms a buffer medium layer between the device and the hole wall. This interface layer can not only evenly transmit stress but also absorb the elastic potential energy released by the device, ultimately forming a collaborative bearing system of surrounding rock-device-filling body.

[0029] The present invention provides a method for unloading and absorbing high-stress areas in coal mine tunnels. It has the following beneficial effects:

[0030] 1. This invention achieves dynamic control of tunnel surrounding rock stress throughout the entire process by constructing a three-stage synergistic system: pressure relief, transfer, and energy absorption. Compared to traditional single-pressure relief hole technology, this solution innovatively combines stress release with energy management, effectively resolving the uncontrollable pressure relief effect caused by the unclear stress transfer path in existing technologies.

[0031] 2. This invention utilizes a rigid-flexible composite energy-absorbing structure, innovatively combining the support performance of steel pipes with the energy-dissipating properties of polymer materials. Compared to conventional anchor support, this design significantly improves the system's energy absorption capacity while maintaining structural stability, overcoming the brittle failure vulnerability of traditional rigid supports.

[0032] 3. This invention utilizes drilling trajectory control technology based on intelligent drilling parameter feedback to ensure precise spatial layout of the pressure relief channel. Compared to drilling methods driven by manual experience, this technical solution effectively addresses the blind construction and quality fluctuations associated with traditional processes by driving decision-making through real-time data.

[0033] 4. This invention establishes a multi-parameter fusion stress monitoring network to achieve real-time visual monitoring of the energy status of the tunnel surrounding rock. Compared with traditional point-based stress monitoring methods, this solution utilizes distributed fiber optic sensing technology to obtain continuous strain field data, providing more comprehensive information support for tunnel stability assessment. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Flow chart of the method of the present invention. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the present specification. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] Please see the attached Figure 1 The embodiment of the present invention provides a method for unloading and absorbing high stress areas in coal mine tunnels, comprising the following steps:

[0037] Step 1, pressure relief stage: drilling holes in high stress areas of the roadway to form pressure relief channels;

[0038] Step 2, transfer stage: transferring stress to the deep part of coal and rock mass through the layout of the drill holes;

[0039] Step 3, energy absorption stage: installing an energy absorption device in the borehole, the device comprising an outer steel pipe, an inner polymer material and a monitoring element.

[0040] Step 1: Pressure relief phase

[0041] Directional drilling creates pressure relief channels in areas of high stress concentration in the tunnel's surrounding rock. These areas are located 6 to 20 meters from the tunnel surface, and specific drilling locations are determined based on geological radar detection. Drilling operations utilize an intelligent drilling rig system equipped with a real-time drilling parameter monitoring module that dynamically collects axial thrust, rotational torque, and vibration frequency parameters.

[0042] The drill hole diameter is set between 50 and 150 mm, with a medium diameter of 89 to 108 mm being preferred. This size balances pressure relief and construction efficiency. The drilling depth is controlled between 5 and 20 meters, determined based on the tunnel depth and ground stress test results. During construction, a diamond composite drill bit is used in conjunction with a high-pressure water jet to assist in rock breaking, achieving a single-step drilling operation and avoiding the surrounding rock disturbance caused by multiple hole expansions.

[0043] The drill holes are spaced axially along the roadway, with the spacing between adjacent holes being 3 to 5 times the hole diameter. Preferably, multiple rows of drill holes are formed on the sides and roof of the roadway, with row spacing controlled within a range of 1.5 to 2.5 meters. The drill hole axis forms an inclination angle of 5° to 30° with the normal to the roadway cross section. This angle design facilitates the construction of stress migration channels directed deep into the coal and rock mass.

[0044] The intelligent drilling system is equipped with a measurement-while-drilling device (MWD) that captures real-time drilling trajectory data. During drilling, the control system automatically adjusts feed pressure and speed parameters based on feedback from drilling speed, torque fluctuations, and vibration spectrum characteristics. Preferably, when the monitored torque value exceeds a set threshold, the system automatically initiates a reverse rotation slag removal process to ensure hole quality.

[0045] After drilling is complete, the integrity of the borehole wall is inspected using an in-hole imaging device. Preferentially, any partially collapsed boreholes are cleaned with high-pressure air, and if necessary, low-viscosity epoxy resin is injected to reinforce the borehole wall. This process ensures the effectiveness and stability of the pressure relief channel, providing a structural foundation for the subsequent installation of the energy absorption device.

[0046] The spatial layout of the pressure relief channels is designed based on elastic-plastic mechanics theory. By establishing a mathematical model for the stress distribution of the tunnel surrounding rock, the optimal drilling density and spatial orientation are calculated. Preferably, finite element analysis is used to simulate the stress release effects under different drilling parameters to determine the optimal matching relationship between hole diameter, hole depth, and spacing.

[0047] Step 2: Transfer Phase

[0048] Based on the principles of elastic-plastic mechanics, a three-dimensional stress migration network is constructed through the spatial layout design of the drill hole cluster. The drill hole axis forms a controllable inclination angle of 5° to 30° with the normal line of the tunnel cross section. This angle range, determined through theoretical calculations, effectively guides stress waves to propagate deep into the rock mass. Preferably, a larger inclination angle is used in the tunnel roof, while a smaller angle is used in the sidewalls, forming differentiated stress conduction paths.

[0049] The drill hole cluster is radially distributed with the geometric center of the tunnel cross section as the reference point, with adjacent drill holes forming a fan-shaped angle of 10° to 15° on the horizontal projection plane. This layout is designed based on the principle of stress field superposition, allowing the pressure relief zones generated by each drill hole to connect with each other, forming a continuous energy transfer channel. Preferably, the drill hole distribution is intensified in areas with high stress concentration, constructing a multi-level stress transfer subsystem.

[0050] The borehole tip extends to a low-stress zone deep within the coal and rock mass. Its spatial positioning is determined by combining geological exploration data with numerical simulation. Preferably, FLAC3D software is used to establish a mechanical model of the roadway surrounding rock, calculating the optimal borehole extension length and azimuth to ensure the stress conduction path forms the optimal angle with the rock mass structural plane.

[0051] During the drilling process, real-time trajectory monitoring is implemented, using a borehole inclinometer to obtain actual borehole deviation data. When the drill axis deviates from the designed trajectory beyond an allowable threshold, a drill correction mechanism is activated. Preferably, trajectory correction is achieved by adjusting the lateral cutting force distribution of the drill bit to ensure that the spatial configuration of the drill group meets design requirements.

[0052] After drilling is complete, the borehole wall quality is inspected, using a fiber optic endoscope to scan and image the entire borehole. High-pressure grouting is then applied to any localized fracture zones identified during this inspection. The grouting material is preferably a nano-silicate composite material, whose permeability matches the surrounding rock fractures and effectively improves the structural integrity of the borehole wall.

[0053] The stress transfer mechanism is based on energy redistribution theory, altering the in-situ rock stress distribution through the weakened zones formed by the borehole cluster. Preferably, a mathematical model for stress redistribution is established using the boreholes as nodes to calculate the energy transfer efficiency under different layout parameters and optimize the combination of borehole spacing and inclination angles.

[0054] The spatial arrangement of the borehole clusters synergizes with the tunnel's geological structure. Preferably, the borehole strikes at an angle of 45° to 60° to the main joint plane of the rock formation. This design effectively blocks concentrated stress transfer along the structural plane, promoting energy diffusion and transfer in the desired direction.

[0055] Step 3: Energy absorption stage

[0056] The energy absorption device utilizes a composite structural design, consisting of an outer steel tube, a polymer core, and a monitoring system. The outer steel tube is constructed from low-alloy, high-strength steel, with a wall thickness determined through mechanical calculations to withstand the radial pressure generated by surrounding rock deformation. Preferably, the inner surface of the steel tube is sandblasted to achieve a specific surface roughness to enhance interfacial friction.

[0057] The polymer core is made of ultra-high molecular weight polyethylene, whose molecular chain orientation is regulated through a special process to achieve anisotropic mechanical properties. The core diameter is preferably slightly smaller than the inner diameter of the steel pipe, creating a 0.5-2mm assembly gap. This design allows for deformation space for compressive creep. An annular groove is provided on the surface of the core for embedding distributed optical fiber sensors. The preparation method of ultra-high molecular weight polyethylene comprises the following steps: mixing ultra-high molecular weight polyethylene powder with a molecular weight range of 2.5 million to 4 million with an antioxidant and a lubricating agent in a high-speed mixer, and cold pressing the mixture under a pressure of 150 MPa to form a cylindrical billet; placing the billet in an inert gas environment, and sintering it at a constant temperature of 140°C to 150°C for 4 to 6 hours to form a sintered rod; then, transferring the sintered rod to a solid phase extruder, and stretching and extruding it through a conical die with a convergence angle of 30° and a stretch ratio of 10:1 under temperature control of 125°C to 135°C. This process aligns the polyethylene molecular chains along the extrusion direction; finally, cooling the extruded rod through a gradient cooling device to fix its molecular chain orientation structure.

[0058] During installation, a hydraulic propulsion device is used to press the core into the steel pipe, with the propulsion speed controlled within the range of 0.1 to 0.3 m / min. Preferably, the propulsion resistance is monitored in real time during the pressing process. When the pressure value reaches a set threshold, the operation is suspended and a rotation correction is implemented to ensure that the core axis coincides with the centerline of the steel pipe.

[0059] The monitoring system consists of an array of fiber grating (FBG) sensors, spaced evenly along the core. Ideally, the sensor nodes are spaced 0.5 to 1.0 meters apart, using wavelength division multiplexing (WDM) technology for multi-channel signal transmission. Sensor signal lines are routed through a waterproof junction box prefabricated in the sidewall of the steel pipe and connected to a data acquisition unit within the tunnel.

[0060] The steel pipe is equipped with removable sealing end caps at both ends, and a pre-installed elastic buffer layer inside the end caps. Preferably, the buffer layer is made of polyurethane microporous foam, whose compression modulus matches the core material, effectively absorbing end impact energy. A grouting channel is provided in the center of the end caps, and a high-pressure grouting pipe is pre-embedded in the channel.

[0061] After the device is in place, annular grouting is performed using a cement-based composite material. Preferably, a staged pressure grouting process is employed, with the initial grouting pressure controlled at 0.5-1.0 MPa, and then increased to 2.0-3.0 MPa during the final stabilization phase. After the grouting solidifies, a gradient modulus structure is formed, achieving mechanical coupling between the device and the surrounding rock.

[0062] The energy absorption mechanism is based on viscoelastic dissipation theory. When surrounding rock stress is transmitted to the device, the steel tube undergoes elastic deformation to store energy, while the core dissipates energy through molecular chain slip. Preferably, a constitutive equation for the core material is established to describe its stress-strain response characteristics at different strain rates, providing a theoretical basis for device design.

[0063] The monitoring system collects real-time strain distribution data on the core and analyzes the stress wave propagation characteristics through Fourier transform. Preferably, when the monitored local strain value exceeds a preset threshold, an early warning signal is triggered and an emergency support plan is initiated.

[0064] Example 1: Deep transport tunnel application

[0065] This method was implemented in the east wing transport tunnel, located at a depth of 800 meters. The tunnel has a straight-walled, semicircular arch cross-section (clear width 5.2 meters, clear height 4.0 meters). Pressure relief holes were constructed using a ZY-2300 fully hydraulic intelligent drilling rig equipped with a Φ120mm diamond composite drill bit. The holes were drilled to a depth of 18 meters, 1.5 meters from the tunnel floor, with groups of holes spaced every 4.2 meters along the tunnel's direction. The drill axis was angled 22° with the tunnel normal, and the holes were arranged according to a three-leaf rose trajectory (r = 4.2 sin3θ), forming three main stress relief channels.

[0066] The energy absorption device consists of a Φ120×6mm Q345B seamless steel tube and a Φ118mm ultra-high molecular weight polyethylene rod (molecular weight 2.5 million, tensile strength 180 MPa). The rod's surface is machined with a dovetail groove, 3mm deep and 5mm wide at the base. FBG-8000 fiber Bragg grating sensors are embedded in the groove, with sensor nodes spaced 0.6m apart. During installation, a YQ-300 hydraulic pusher is used to press the rod into the steel tube at a speed of 0.25m / min, maintaining a stable push pressure between 8-12MPa.

[0067] The grouting operation was carried out in three phases: in the first phase, a nanosilicate-based grout was injected at a pressure of 0.8 MPa to fill the annular gap between the steel pipe and the surrounding rock, maintaining the pressure for 10 minutes. In the second phase, the pressure was increased to 1.5 MPa for 20 minutes to enhance penetration. In the third phase, a high-pressure grouting of 2.2 MPa was used, maintaining the pressure for 30 minutes to ensure that the grout fully penetrated the surrounding rock fissures. The grouting solution achieved a compressive strength of 40 MPa and an elastic modulus of 2.5 GPa after 28 days, forming a gradient modulus structure with the surrounding rock.

[0068] Example 2: Composite roof tunnel application

[0069] This scheme was implemented in the return airway of the 15231 working face with a 2.8-m-thick mudstone pseudo-roof. A double-layer drilling structure was designed: the upper drilling hole had a diameter of 100 mm, a depth of 12 m, and an inclination of 15°; the lower drilling hole had a diameter of 80 mm, a depth of 15 m, and an inclination of 25°. The drilling holes were arranged according to the Fibonacci spiral, with a horizontal projection spacing of 3.8 m and a vertical spacing of 2.5 m between adjacent drilling holes. A stress superposition zone of 2.8-3.0 m was formed at the end of the drilling hole. The optimal spatial parameters were determined through FLAC3D simulation.

[0070] The energy absorption device innovatively introduces a Ni-Ti shape memory alloy limit ring with a ring thickness of 6mm, a pre-deformation temperature of 20°C, and a phase transition temperature of 35°C. When the rod strain is monitored to exceed 5000 microstrain, the limit ring is triggered by the surrounding rock temperature to recover its shape and shrink its diameter by 2.5mm, increasing the friction coefficient of the steel pipe-rod interface from 0.15 to 0.35. This design realizes adaptive adjustment of the energy absorption characteristics.

[0071] The monitoring system utilizes BOTDR distributed fiber optic sensing technology, with a 0.9mm tight-buffered optical fiber laid along the entire length of the rod. The system achieves a spatial resolution of 0.5m and features a 1550nm laser source, a sampling frequency of 1Hz, and a strain measurement accuracy of ±15 microstrain. The Brillouin frequency shift signal is processed using a wavelet transform algorithm, reconstructing a cloud map of the strain field distribution across the entire borehole in real time. A Level 3 warning is triggered when the local strain gradient exceeds 50 microstrain per meter.

[0072] Multiple annular grooves are machined into the outer circumference of the ultra-high molecular weight polyethylene (UHMWPE) rod at predetermined axial spacing. The depth and width of each groove are set to exceed the cross-sectional dimensions of the retaining ring. Subsequently, the nickel-titanium retaining ring is radially expanded at a temperature 20°C below its martensitic transition temperature and then installed within the annular grooves of the rod. After installation, the outer diameter of the retaining ring is no larger than that of the polyethylene rod, allowing the rod-retaining ring assembly to be inserted into the outer steel tube. The process proceeds as follows: When the monitoring system measures an axial strain on the polyethylene rod exceeding a threshold of 5000 microstrain, relative slip has occurred between the rod and the inner wall of the steel tube. Frictional heat generated by this slip at the contact interface is transferred to the nickel-titanium retaining ring, causing it to heat up. When the ring temperature reaches or exceeds its austenitic transition temperature of 35°C, the ring material transforms from martensite to austenite. This phase transformation triggers a shape memory effect, causing the ring diameter to shrink by 2.5 mm. This diameter contraction generates radial force, which increases the contact positive pressure between the polyethylene rod and the steel pipe, and ultimately increases the interface friction coefficient from 0.15 to 0.35.

[0073] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for unloading and absorbing high stress areas in coal mine tunnels, characterized in that: The following steps are involved: Step 1, pressure relief stage: drilling holes in high stress areas of the roadway to form pressure relief channels; Step 2, transfer stage: transfer stress to the deep part of coal and rock mass through the layout of the drill holes; Step 3, energy absorption stage: installing an energy absorption device in the borehole, the device comprising an outer steel pipe, an inner polymer material and a monitoring element; The axis of the drill hole in step 2 forms an angle of 5° to 30° with the normal line of the roadway section, the drill hole group is radially distributed, the angle between adjacent drill holes is 10° to 15°, and the end of the drill hole points to the low stress area deep in the coal rock mass; The outer steel pipe in step 3 is a seamless Q235 steel pipe with a wall thickness of 3 to 8 mm and an inner surface roughened by sandblasting, and the polymer material is an ultra-high molecular weight polyethylene rod; The outer diameter of the polyethylene rod is 0.5 to 1.5 mm smaller than the inner diameter of the steel pipe, and the rod length is 10 to 20 cm longer than the steel pipe. During installation, the rod is pressed into the steel pipe by a hydraulic pre-pressing machine so that the rod forms friction contact with the pipe wall. The monitoring elements in step 3 include resistance strain gauges and fiber grating sensors, which are arranged in a group 0.5m along the axial direction of the polyethylene rod. The sensor signal line is led out through the reserved hole in the side wall of the steel pipe and connected to the data acquisition terminal in the tunnel.

2. A method for unloading and absorbing high stress areas in coal mine tunnels according to claim 1, characterized in that: The diameter of the drill hole in step 1 is 50-150 mm, the depth is 5-20 m, and the one-time drilling process is used for construction. The drill holes are arranged in the high stress concentration area 6-20 m away from the tunnel surface and spaced apart along the axial direction of the tunnel.

3. A method for unloading and absorbing high stress areas in coal mine tunnels according to claim 1, characterized in that: Step 3: Weld flanges at both ends of the steel pipe, connect the end cover and seal it with high-strength bolts, set a grouting hole in the center of the end cover, and embed a high-pressure grouting pipe in the hole.

4. A method for unloading and absorbing high stress areas in coal mine tunnels according to claim 1, characterized in that: The drill holes are arranged in 3 to 5 layers according to the tunnel section, the distance between the drill holes in each layer is 3 to 5 times the hole diameter, the upper drill holes are 0.5 to 1.5 meters away from the tunnel roof, and the lower drill holes are 1.0 to 2.0 meters away from the bottom plate.

5. The method for unloading and absorbing high stress areas in coal mine tunnels according to claim 1 is characterized in that: The drilling construction is implemented using an intelligent drilling rig, which is equipped with a drilling parameter monitoring module to monitor the drilling speed, torque and vibration frequency in real time and dynamically adjust the drilling parameters according to the monitoring data.

6. A method for unloading and absorbing high stress areas in coal mine tunnels according to claim 1, characterized in that: After the energy absorbing device described in step 3 is installed, the gap between the drilled hole and the device is filled by a grouting process.

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