A coal mine machine reaming pressure relief method based on multi-dimensional closed loop monitoring

Abstract

The present application relates to a kind of coal mine machinery reaming pressure relief method based on multidimensional closed loop monitoring, comprising the following steps: coal seam and roof and floor coal rock sample is collected, physical mechanics parameter is determined, and tendency identification is carried out, to divide weak, medium, strong impact dangerous area;Three-dimensional model is established using numerical simulation software, simulate the stress distribution of surrounding rock, plastic zone expansion and anchor force condition under the diameter of unreamed section, reaming section diameter, drilling spacing, combined with monitoring threshold requirement, and the optimal parameter combination is obtained by optimization;The total depth of drilling is calculated, and the final optimized parameter is obtained;Special drilling machine and variable diameter drill bit are used, and drilling and reaming are carried out along the direction of parallel coal seam in roadway area, and after reaming is completed, step back drilling is carried out, to form the variable-diameter pressure relief borehole of "small hole section + reaming section", multiple variable-diameter pressure relief boreholes are arranged in single row to form continuous pressure relief zone, and pressure relief is carried out through pressure relief zone;Different safety indicators are monitored by multidimensional closed loop monitoring system.

Description

Technical Field

[0001] This invention relates to the field of coal mine rockburst prevention technology, specifically to a method for mechanical borehole expansion and pressure relief in coal mines based on multi-dimensional closed-loop monitoring. Background Technology

[0002] Rockburst is a typical destructive dynamic disaster in the process of deep coal mining. The large amount of elastic energy released in a short period of time can directly lead to roadway damage, equipment damage, and even casualties, seriously restricting the safe and efficient mining of deep coal resources.

[0003] Borehole pressure relief is a widely used method for preventing rockbursts in the coal mining industry. Existing rockburst prevention technologies mainly include conventional borehole pressure relief (including large-diameter and small-diameter boreholes), hydraulic fracturing, and deep-hole blasting. The core disadvantages of each technology are as follows: Conventional small-diameter drilling (<150mm): has a limited pressure relief range and cannot effectively transfer high stress concentration areas. It requires denser drilling layout, which greatly increases the workload and cost of construction. Conventional large-diameter boreholes (>200mm): The boreholes penetrate the roadway anchorage zone, destroying the integrity of the surrounding rock, reducing the anchorage strength of the anchor bolts, accelerating roadway deformation, and highlighting the contradiction between the pressure relief effect and support protection. Hydraulic fracturing technology: It is difficult to accurately control the depressurization area and the range of fracture development, which can easily lead to insufficient or excessive depressurization and poor stability of depressurization effect; Deep-hole blasting technology: The release of blasting energy is difficult to control, which may cause secondary dynamic disasters and cause excessive disturbance to the surrounding rock, damaging the integrity of the support structure; Furthermore, existing monitoring methods are mostly single-dimensional and lack systematic coordination; a closed-loop mechanism of "monitoring-analysis-adjustment" has not been established, construction parameters remain unchanged, and they cannot adapt to dynamic changes in coal seam geological conditions; monitoring point placement is arbitrary, equipment selection lacks standards, and threshold settings rely on experience, resulting in low data reliability and guidance value, leading to frequent problems of insufficient or excessive pressure relief. Existing borehole pressure relief parameters rely heavily on engineering experience, failing to fully integrate coal seam geological conditions and stress distribution characteristics, and failing to achieve spatial matching between the roadway anchoring zone and stress concentration zone. Additionally, there is a lack of linkage and optimization with monitoring data, resulting in low pressure relief efficiency and poor adaptability. Summary of the Invention

[0004] To address the aforementioned problems, the purpose of this invention is to provide a method for mechanical borehole enlargement and pressure relief in coal mines based on multi-dimensional closed-loop monitoring. This method adopts an integrated process of "preliminary parameter optimization - small hole drilling - directional borehole enlargement - step-by-step drilling withdrawal - multi-dimensional closed-loop monitoring". The core lies in the deep integration of "variable borehole structure design" and "multi-dimensional closed-loop monitoring system" to achieve synergy in pressure relief effect, support protection and dynamic adaptation.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for mechanical borehole expansion and pressure relief in coal mines based on multi-dimensional closed-loop monitoring, comprising the following steps: Coal seam and roof and floor coal and rock samples were collected, and physical and mechanical parameters were measured using a servo rock mechanics testing system. Tension identification was also performed to delineate the danger zones of weak, medium and strong impacts. Based on the tendency identification, a three-dimensional model was established using numerical simulation software to simulate the stress distribution of the surrounding rock, the expansion of the plastic zone, and the stress on the anchor bolts under the diameter of the unreamed section, the diameter of the reamed section, and the borehole spacing. Combined with the monitoring threshold requirements, the optimal parameter combination was obtained. Based on the optimal parameter combination, the total borehole depth is calculated using the total borehole depth calculation formula, and the final optimized parameters are obtained. The final optimized parameters include the total borehole depth, the size parameters of the unreamed section, the size parameters of the reamed section, and the borehole spacing. Using a special drilling rig and a variable diameter drill bit, holes are drilled and enlarged in the roadway area along the direction parallel to the coal seam. After the enlargement is completed, the drill is withdrawn in stages to form a variable diameter pressure relief borehole consisting of a "small hole section + enlargement section". Multiple variable diameter pressure relief boreholes are arranged in a single row to form a continuous pressure relief zone, through which pressure is relieved. During the drilling and reaming process, a multi-dimensional closed-loop monitoring system is used to monitor different safety indicators.

[0006] The coal mine mechanical borehole expansion and pressure relief method based on multi-dimensional closed-loop monitoring preferably includes the following physical and mechanical parameters: density, elastic modulus, cohesion, and internal friction angle of the rock sample.

[0007] The aforementioned method for mechanical borehole enlargement and pressure relief in coal mines based on multi-dimensional closed-loop monitoring, preferably, uses the following formula for calculating the total borehole depth: Where: Rt is the total drilling depth; L is the tunnel span, h is the tunnel height; ω=1.15 is the stress disturbance coefficient.

[0008] The aforementioned coal mine mechanical borehole expansion and pressure relief method based on multi-dimensional closed-loop monitoring preferably has a total borehole depth of 20m. The dimensions of the unexpanded section are: diameter 150mm and length 7m. The dimensions of the enlarged section are: diameter 350mm and length 13m; The borehole spacing is 2m.

[0009] The aforementioned coal mine mechanical borehole enlargement and pressure relief method based on multi-dimensional closed-loop monitoring, preferably, involves drilling and enlarging boreholes along the direction parallel to the coal seam in the roadway area, specifically including the following steps: A special drilling rig is used to drill holes in the roadway area along the direction parallel to the coal seam. When the hole reaches the set depth, a special variable diameter drill bit is deployed to reciprocate from the bottom of the hole to the opening to enlarge the hole by a set distance. During the enlargement process, high-pressure water is used to flush away coal dust to promote the development of fractures and ensure that the diameter of the enlarged section is uniform. After the enlargement is completed, the drill bit is closed and the hole is slowly withdrawn.

[0010] The aforementioned method for mechanical borehole expansion and pressure relief in coal mines based on multi-dimensional closed-loop monitoring, preferably, involves monitoring different safety indicators through a multi-dimensional closed-loop monitoring system, specifically including the following steps: By setting up different monitoring devices in different areas and setting monitoring thresholds, different safety indicators are monitored, including: drill cuttings volume, coal stress, micro-vibration, and surrounding rock deformation. Real-time monitoring data of different safety indicators are collected in different dimensions, and the monitoring data is integrated and analyzed. The monitoring data is assessed for safety by using monitoring thresholds to obtain results of normal, warning, or exceeding limits. If a warning is issued, a pop-up message will be displayed; if the limits are exceeded, an audible and visual alarm will be triggered. The hole enlargement steps are categorized and adjusted. Monitoring is strengthened immediately after the adjustment is implemented. If the data returns to the safe threshold, construction continues; otherwise, the adjustment is repeated. After construction, continuous monitoring was conducted for a set number of days, focusing on observing the stability of surrounding rock deformation, microseismic energy release, and coal stress balance. All data and adjustment records were archived, and a correlation model of "geological conditions - construction parameters - monitoring results" was established to provide a basis for parameter optimization in subsequent work.

[0011] The aforementioned coal mine mechanical borehole expansion and pressure relief method based on multi-dimensional closed-loop monitoring preferably involves monitoring different safety indicators by setting different monitoring devices in different areas and setting monitoring thresholds. Specifically: Drill cuttings monitoring: A dedicated collection area is set up below the opening of each pressure relief borehole, with a leak-proof mat laid out. Drill cuttings are collected using high-temperature resistant cemented collection bags, weighed using an electronic scale, and the collection height is measured using a tape measure. The safe threshold for drill cuttings is: average drill cuttings per hole ≥ 2005 kg. The warning threshold is: average drill cuttings per hole 1500-2005 kg. The over-limit threshold is: average drill cuttings per hole < 1500 kg. Coal stress monitoring: At least three monitoring sections are set up on the main flank, with at least seven stress gauges installed on each section, at monitoring depths of 2m, 4m, 6m, 8m, 10m, 12m, and 14m respectively; at least two stress gauges are installed on the corresponding sections of the auxiliary flank, at monitoring depths of 2m and 3m respectively, with borehole diameters... The boreholes were filled and fixed with epoxy resin and left to cure for 24 hours. The safe threshold for coal stress is: coal stress reduction ≥ 45%, and stress increase in the anchoring zone ≤ 1 MPa. The warning threshold is: coal stress reduction 30%-45%, and stress increase in the anchoring zone 1-2 MPa. The over-limit threshold is: coal stress reduction < 30%, and stress increase in the anchoring zone > 2 MPa. Microseismic monitoring: One seismic sensor is installed 5m from each end of the pressure relief area. The sensor is fixed to the anchor bolts on the top slab. Four probes are evenly distributed on the top, bottom, left, and right sides to form a 50m coverage circle. The sensor is connected to the main control unit. The microseismic safety threshold is: total energy reduction ≥52%, no ≥10 5 The warning threshold for a strong earthquake event J is: a 20%-52% reduction in total energy, and a 10% warning threshold for sporadic occurrences. 4 -10 5 Event J has the following over-limit thresholds: total energy reduction <20%, ≥10 5 J has ≥2 events; Surrounding rock deformation monitoring: One monitoring section is set up every 5m, and additional sections are set up at both ends by 10m. Each section uses a cross-point layout method to set monitoring points at the center of the two sides, the top plate of the rock stratum, and the bottom plate of the rock stratum. The safe threshold for surrounding rock deformation is: the distance between the two sides ≤240mm and the distance between the top plate of the rock stratum and the bottom plate of the rock stratum ≤350mm. The warning threshold is: the distance between the two sides 200-240mm and the distance between the top plate of the rock stratum and the bottom plate of the rock stratum 300-350mm. The over-limit threshold is: the distance between the two sides >240mm and the distance between the top plate of the rock stratum and the bottom plate of the rock stratum >350mm. Crack detection: The crack detection is carried out on the same cross-section as the coal seam stress monitoring section, with one crack detection point constructed on each cross-section. The detection hole with a depth of 5m should be ≥1m away from the pressure relief drill hole; the safety threshold for crack detection is: the loosening zone is 1.7-1.8m, the warning threshold is: the loosening zone is 1.6-1.7m or 1.8-1.9m, and the over-limit threshold is: the loosening zone is <1.6m or >1.9m.

[0012] The aforementioned method for mechanical borehole expansion and pressure relief in coal mines based on multi-dimensional closed-loop monitoring, preferably, involves the real-time acquisition of monitoring data for different safety indicators across multiple dimensions, specifically as follows: Drill cuttings: Stop collecting coal dust and weigh it every 1m of drilling or reaming, record the depth and time, and calculate the total weight and average value after the construction is completed; Coal stress: 8-hour baseline values ​​were collected 24 hours before construction. Coal stress was continuously collected at a frequency of 1Hz during construction, and a curve was generated every 30 minutes. During the borehole expansion stage, the depth of 7-20m was monitored. Coal stress was collected 2 hours / time within 24 hours after construction and once / day thereafter. Microseismic data: The equipment is started 12 hours before construction, and microseismic data is continuously collected at a sampling frequency of 1000Hz. Data with a seismic intensity ≥10 is automatically filtered.3 J event and push to the terminal; Rock deformation: Baseline values ​​were collected 24 hours before construction, and the baseline values ​​were averaged after being repeated 3 times. Rock deformation data were collected every 6 hours during construction. Rock deformation was measured immediately after hole enlargement and drilling withdrawal. Rock deformation data were collected once a day for the first 7 days after construction and once every 3 days thereafter. Fracture detection: The first detection is carried out 24 hours after the single hole is drilled, and the second detection is carried out 7 days after all holes are completed, with fracture images captured simultaneously.

[0013] The aforementioned method for mechanical borehole expansion and pressure relief in coal mines based on multi-dimensional closed-loop monitoring, preferably, includes the following steps for integrating and analyzing the monitoring data: Data transmission and aggregation: Data is automatically collected and transmitted to the field control terminal via wired connection. Manually collected data is entered in real time, forming a related database of "time-location-multi-dimensional data". Cross-validation analysis: Compare the amount of drill cuttings, stress reduction at corresponding depth, and micro-vibration energy of the same borehole to identify data discrepancies and verify the quality of hole enlargement or equipment condition; Overall regional verification: By comparing monitoring data from multiple boreholes, we can identify areas with weak pressure relief or excessive disturbance. Trend prediction: Fit the change curve of continuous 24-hour data to predict whether it may exceed the limit in the future and avoid risks in advance.

[0014] The aforementioned method for mechanical borehole enlargement and pressure relief in coal mines based on multi-dimensional closed-loop monitoring, preferably, includes the following steps: The classification and adjustment of borehole enlargement steps specifically include: Insufficient pressure relief: Check the quality of the hole enlargement, repeat the enlargement process 1-2 times, increase the high-pressure hydraulic pressure to 12-15MPa, extend the flushing time, and if necessary, increase the drilling density or extend the enlargement length to 14-15m. Risks of excessive pressure relief or support: Immediately stop borehole reaming, shorten the reaming length to 11-12m, and adjust the number of reciprocating borehole reaming cycles to 1; add anchor cables to areas with excessive deformation. Warning: The monitoring frequency for the corresponding dimension will be doubled, equipment and construction parameters will be checked, and construction will be suspended until the data returns to the safe threshold.

[0015] The present invention has the following advantages due to the adoption of the above technical solutions: Significant stress relief effect: The peak stress of the surrounding rock in the roadway decreased by 62%, and the peak stress shifted from 6m from the roadway wall to more than 22m; the micro-vibration energy release per unit area decreased by 68%, with no ≥10 5 J-force impact energy release, rockburst occurrence rate is 0, effectively preventing rockburst; Good support and protection: In the unexpanded section, the effective restraint force of the anchor bolts is maintained above 5MPa in the protected anchor zone, the deformation of the two sides of the roadway is reduced by 63%, the deformation of the roof and floor is reduced by 51%, the stress increase in the anchor zone is ≤1MPa, and the support structure is intact and undamaged. Improved construction efficiency: Single-hole construction time ≤ 8 hours, borehole spacing of 2m without the need for additional drilling, reducing workload by 40% compared to conventional large-diameter borehole pressure relief technology; mining efficiency increased by 30%. Precise and efficient monitoring: Cross-validation of data from five dimensions eliminates contradictions and misjudgments, improving data reliability by 80%; Response time for rectification of insufficient or excessive pressure relief is ≤1 hour, with a 100% rectification compliance rate; Wide adaptability: Parameters can be adjusted through numerical simulation, making it suitable for high-stress, hard coal seams with uniaxial compressive strength ≥30MPa and burial depth ≥680m, as well as working face roadways with medium to strong impact hazard levels, without requiring significant adjustments to the core logic. Attached Figure Description

[0016] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts. In the drawings: Figure 1 This is a schematic diagram of the coal mine strata structure according to the present invention; Figure 2 This is a flowchart of the multi-dimensional closed-loop monitoring logic of the coal mine mechanical borehole expansion and pressure relief method based on multi-dimensional closed-loop monitoring according to the present invention. Figure 3 This is a schematic diagram of the mechanical hole expansion and pressure relief structure and stress transfer of the present invention; Figure 4 This is a schematic diagram of the planar arrangement for drill cuttings detection according to the present invention; Figure 5 This is a planar schematic diagram of the stress gauge installation position according to the present invention.

[0017] The labels for the attached figures are as follows: 1, 2, 3 - Roof of rock strata; 4 - Coal seam; 5, 6, 7 - Floor of rock strata; 8 - Small borehole section; 9 - Enlarged borehole section; 10 - Roadway; 11 - Anchor bolt; 12 - Fractured zone of surrounding rock; 13 - Plastic zone of surrounding rock; 14 - Elastic zone of surrounding rock. Detailed Implementation

[0018] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0019] This invention provides a method for mechanical borehole enlargement and pressure relief in coal mines based on multi-dimensional closed-loop monitoring. It adopts an integrated process of "preliminary parameter optimization - small hole drilling - directional borehole enlargement - step-by-step drilling withdrawal - multi-dimensional closed-loop monitoring". Its core lies in the deep integration of "variable borehole structure design" and "multi-dimensional closed-loop monitoring system" to achieve synergy in pressure relief effect, support protection and dynamic adaptation.

[0020] like Figure 1 As shown, the structure of the coal mine strata of the present invention is as follows: the middle part is coal seam 4, the top of coal seam 4 is a three-layer rock stratum roof plate, labeled 1, 2 and 3 in the figure, the bottom of coal seam 4 is a three-layer rock stratum floor plate, labeled 5, 6 and 7 in the figure, the center of coal seam 4 is roadway 10, the two sides of roadway 10 are small hole sections 8, the free ends of the small hole sections extend to both sides to form enlarged hole sections 9, anchor bolts 11 are installed on roadway 10, the area around roadway 10 is the surrounding rock fracture zone 12, the area around the surrounding rock fracture zone 12 is the surrounding rock plastic zone 13, and the area around the surrounding rock plastic zone 13 is the surrounding rock elastic zone 14.

[0021] The present invention provides a method for mechanical borehole expansion and pressure relief in coal mines based on multi-dimensional closed-loop monitoring, comprising the following steps: S1. Collect coal seam and roof and floor coal and rock samples, determine physical and mechanical parameters through servo rock mechanics testing system, and conduct orientation identification to classify weak, medium and strong impact hazard zones. S2. Based on the tendency identification, a three-dimensional model is established using numerical simulation software to simulate the stress distribution of the surrounding rock, the expansion of the plastic zone, and the stress on the anchor bolts under the diameter of the unreamed section, the diameter of the reamed section, and the borehole spacing. Combined with the monitoring threshold requirements, the optimal parameter combination is obtained. S3. Based on the optimal parameter combination, calculate the total borehole depth using the total borehole depth calculation formula, and obtain the final optimized parameters, which include the total borehole depth, the size parameters of the unreamed section, the size parameters of the reamed section, and the borehole spacing. S4. Using a special drilling rig and a variable diameter drill bit, drill holes and enlarge them in the roadway area along the direction parallel to the coal seam. After the enlargement is completed, the drill is withdrawn in stages to form a variable diameter pressure relief borehole consisting of a "small hole section + enlargement section". Multiple variable diameter pressure relief boreholes are arranged in a single row to form a continuous pressure relief zone, through which pressure is relieved. S5. During the drilling and reaming process, a multi-dimensional closed-loop monitoring system is used to monitor different safety indicators.

[0022] In the above embodiments, preferably, the physical and mechanical parameters include: the density, elastic modulus, cohesion, and internal friction angle of the rock sample.

[0023] In the above embodiments, preferably, the formula for calculating the total borehole depth is: Where: Rt is the total drilling depth; L is the tunnel span, h is the tunnel height; ω=1.15 is the stress disturbance coefficient.

[0024] In the above embodiments, preferably, as follows: Figure 4 As shown, the total depth of the borehole is 20m; The dimensions of the unexpanded section are: diameter 150mm and length 7m. The dimensions of the enlarged section are: diameter 350mm and length 13m; The borehole spacing is 2m.

[0025] In the above embodiments, preferably, as follows: Figure 3 As shown, drilling and enlarging holes along the direction parallel to the coal seam in the roadway area specifically includes the following steps: A special drilling rig is used to drill holes in the roadway area along the direction parallel to the coal seam. When the hole reaches the set depth, a special variable diameter drill bit is deployed to reciprocate from the bottom of the hole to the opening to enlarge the hole by a set distance. During the enlargement process, high-pressure water is used to flush away coal dust to promote the development of fractures and ensure that the diameter of the enlarged section is uniform. After the enlargement is completed, the drill bit is closed and the hole is slowly withdrawn.

[0026] In the above embodiments, preferably, as follows: Figure 2 As shown, the monitoring of different safety indicators through a multi-dimensional closed-loop monitoring system specifically includes the following steps: By setting up different monitoring devices in different areas and setting monitoring thresholds, different safety indicators are monitored, including: drill cuttings volume, coal stress, micro-vibration, and surrounding rock deformation. Real-time monitoring data of different safety indicators are collected in different dimensions, and the monitoring data is integrated and analyzed. The monitoring data is assessed for safety by using monitoring thresholds to obtain results of normal, warning, or exceeding limits. If a warning is issued, a pop-up message will be displayed; if the limits are exceeded, an audible and visual alarm will be triggered. The hole enlargement steps are categorized and adjusted. Monitoring is strengthened immediately after the adjustment is implemented. If the data returns to the safe threshold, construction continues; otherwise, the adjustment is repeated. After construction, continuous monitoring was conducted for a set number of days, focusing on observing the stability of surrounding rock deformation, microseismic energy release, and coal stress balance. All data and adjustment records were archived, and a correlation model of "geological conditions - construction parameters - monitoring results" was established to provide a basis for parameter optimization in subsequent work.

[0027] In the above embodiments, preferably, the step of setting different monitoring devices in different areas and setting monitoring thresholds to monitor different safety indicators specifically involves: Drill cuttings monitoring: A dedicated collection area is set up below the opening of each pressure relief borehole, with a leak-proof mat laid out. Drill cuttings are collected using high-temperature resistant cemented collection bags, weighed using an electronic scale, and the collection height is measured using a tape measure. The safe threshold for drill cuttings is: average drill cuttings per hole ≥ 2005 kg. The warning threshold is: average drill cuttings per hole 1500-2005 kg. The over-limit threshold is: average drill cuttings per hole < 1500 kg. Coal stress monitoring: such as Figure 5 As shown, at least three monitoring sections are set up on the main slope, with at least seven stress gauges installed on each section, at monitoring depths of 2m, 4m, 6m, 8m, 10m, 12m, and 14m respectively; at least two stress gauges are installed on the corresponding sections of the auxiliary slope, with monitoring depths of 2m and 3m respectively, and the borehole diameter is... The boreholes were filled and fixed with epoxy resin and left to cure for 24 hours. The safe threshold for coal stress is: coal stress reduction ≥ 45%, and stress increase in the anchoring zone ≤ 1 MPa. The warning threshold is: coal stress reduction 30%-45%, and stress increase in the anchoring zone 1-2 MPa. The over-limit threshold is: coal stress reduction < 30%, and stress increase in the anchoring zone > 2 MPa. Microseismic monitoring: One seismic sensor is installed 5m from each end of the pressure relief area. The sensor is fixed to the anchor bolts on the top slab. Four probes are evenly distributed on the top, bottom, left, and right sides to form a 50m coverage circle. The sensor is connected to the main control unit. The microseismic safety threshold is: total energy reduction ≥52%, no ≥10 5 The warning threshold for a strong earthquake event J is: a 20%-52% reduction in total energy, and a 10% warning threshold for sporadic occurrences. 4 -10 5 Event J has the following over-limit thresholds: total energy reduction <20%, ≥10 5 J has ≥2 events; Rock deformation monitoring: One monitoring section is set up every 5m, and additional sections are set up at both ends by 10m. Each section uses a cross-point layout method to set monitoring points at the center of both sides (i.e., the main side and the secondary side), the top plate of the rock stratum, and the bottom plate of the rock stratum. The safe threshold for rock deformation is: the distance between the two sides ≤ 240mm, and the distance between the top plate of the rock stratum and the bottom plate of the rock stratum ≤ 350mm. The warning threshold is: the distance between the two sides 200-240mm, and the distance between the top plate of the rock stratum and the bottom plate of the rock stratum 300-350mm. The over-limit threshold is: the distance between the two sides > 240mm, and the distance between the top plate of the rock stratum and the bottom plate of the rock stratum > 350mm. Crack detection: The crack detection is carried out on the same cross-section as the coal seam stress monitoring section, with one crack detection point constructed on each cross-section. The detection hole with a depth of 5m should be ≥1m away from the pressure relief drill hole; the safety threshold for crack detection is: the loosening zone is 1.7-1.8m, the warning threshold is: the loosening zone is 1.6-1.7m or 1.8-1.9m, and the over-limit threshold is: the loosening zone is <1.6m or >1.9m.

[0028] It should be noted that the main side refers to the coal mining face on both sides of the roadway, while the secondary side refers to the non-coal mining face on both sides of the roadway.

[0029] In the above embodiments, preferably, the step of collecting monitoring data of different safety indicators in real time across dimensions specifically includes: Drill cuttings: Stop collecting coal dust and weigh it every 1m of drilling or reaming, record the depth and time, and calculate the total weight and average value after the construction is completed; Coal stress: 8-hour baseline values ​​were collected 24 hours before construction. Coal stress was continuously collected at a frequency of 1Hz during construction, and a curve was generated every 30 minutes. During the borehole expansion stage, the depth of 7-20m was monitored. Coal stress was collected 2 hours / time within 24 hours after construction and once / day thereafter. Microseismic events: The equipment is started 12 hours before construction, and microseismic data is continuously collected at a frequency of 1000Hz. Data with a seismic intensity ≥10 is automatically filtered. 3 J event and push to the terminal; Rock deformation: Baseline values ​​were collected 24 hours before construction. The baseline values ​​were repeated 3 times and the average was taken. Rock deformation data were collected every 6 hours during construction. Rock deformation was measured immediately after hole enlargement and drilling withdrawal. Rock deformation data were collected once a day for 7 days after construction and once every 3 days thereafter. Fracture detection: The first detection is carried out 24 hours after the single hole is drilled, and the second detection is carried out 7 days after all holes are completed, with fracture images captured simultaneously.

[0030] In the above embodiments, preferably, the integration and analysis of the monitoring data specifically includes the following steps: Data transmission and aggregation: Data is automatically collected and transmitted to the field control terminal via wired connection. Manually collected data is entered in real time, forming a related database of "time-location-multi-dimensional data". Cross-validation analysis: Compare the amount of drill cuttings, stress reduction at corresponding depth, and micro-vibration energy of the same borehole to identify data discrepancies and verify the quality of hole enlargement or equipment condition; Overall regional verification: By comparing monitoring data from multiple boreholes, we can identify areas with weak pressure relief or excessive disturbance. Trend prediction: Fit the change curve of continuous 24-hour data to predict whether it may exceed the limit in the future and avoid risks in advance.

[0031] In the above embodiments, preferably, the classification and adjustment hole enlargement step specifically includes: Insufficient pressure relief: Check the quality of the hole enlargement, repeat the enlargement process 1-2 times, increase the high-pressure hydraulic pressure to 12-15MPa, extend the flushing time, and if necessary, increase the drilling density or extend the enlargement length to 14-15m. Risks of excessive pressure relief or support: Immediately stop borehole reaming, shorten the reaming length to 11-12m, and adjust the number of reciprocating borehole reaming cycles to 1; add anchor cables to areas with excessive deformation. Warning: The monitoring frequency for the corresponding dimension will be doubled, equipment and construction parameters will be checked, and construction will be suspended until the data returns to the safe threshold.

[0032] It should be noted that densified drilling refers to adding new holes on the basis of existing holes, which is well known to those skilled in the art and will not be elaborated here.

[0033] In addition, the effectiveness verification data of the present invention is shown in the table below: The experimental results of this invention are as follows: After implementing this solution in the 3106 ventilation roadway, the cross-validation of multi-dimensional monitoring data accurately reflects the pressure relief effect and the surrounding rock condition, achieving synergy between pressure relief effect and support protection; the roadway support structure is intact, and the mining efficiency is improved by 30%, fully verifying the effectiveness, practicality and stability of this technical solution.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for mechanical borehole expansion and pressure relief in coal mines based on multi-dimensional closed-loop monitoring, characterized in that, Includes the following steps: Coal seam and roof and floor coal and rock samples were collected, and physical and mechanical parameters were measured using a servo rock mechanics testing system. Tension identification was also performed to delineate the danger zones of weak, medium and strong impacts. Based on the tendency identification, a three-dimensional model was established using numerical simulation software to simulate the stress distribution of the surrounding rock, the expansion of the plastic zone, and the stress on the anchor bolts under the diameter of the unreamed section, the diameter of the reamed section, and the borehole spacing. Combined with the monitoring threshold requirements, the optimal parameter combination was obtained. Based on the optimal parameter combination, the total borehole depth is calculated using the total borehole depth calculation formula, and the final optimized parameters are obtained. The final optimized parameters include the total borehole depth, the size parameters of the unreamed section, the size parameters of the reamed section, and the borehole spacing. Using a special drilling rig and a variable diameter drill bit, holes are drilled and enlarged in the roadway area along the direction parallel to the coal seam. After the enlargement is completed, the drill is withdrawn in stages to form a variable diameter pressure relief borehole consisting of a "small hole section + enlargement section". Multiple variable diameter pressure relief boreholes are arranged in a single row to form a continuous pressure relief zone, through which pressure is relieved. During the drilling and reaming process, a multi-dimensional closed-loop monitoring system is used to monitor different safety indicators.

2. The method for mechanical borehole expansion and pressure relief in coal mines based on multi-dimensional closed-loop monitoring according to claim 1, characterized in that, The physical and mechanical parameters include: the density, elastic modulus, cohesion, and internal friction angle of the rock sample.

3. The method for mechanical borehole expansion and pressure relief in coal mines based on multi-dimensional closed-loop monitoring according to claim 1, characterized in that, The formula for calculating the total borehole depth is as follows: Where: Rt is the total drilling depth; L is the tunnel span, h is the tunnel height; ω=1.15 is the stress disturbance coefficient.

4. The method for mechanical borehole expansion and pressure relief in coal mines based on multi-dimensional closed-loop monitoring according to claim 1, characterized in that, The total depth of the borehole is 20m; The dimensions of the unexpanded section are: diameter 150mm and length 7m. The dimensions of the enlarged section are: diameter 350mm and length 13m; The borehole spacing is 2m.

5. The method for mechanical borehole expansion and pressure relief in coal mines based on multi-dimensional closed-loop monitoring according to claim 1, characterized in that, The drilling and enlargement of holes in the roadway area along the direction parallel to the coal seam specifically includes the following steps: A special drilling rig is used to drill holes in the roadway area along the direction parallel to the coal seam. When the hole reaches the set depth, a special variable diameter drill bit is deployed to reciprocate from the bottom of the hole to the opening to enlarge the hole by a set distance. During the enlargement process, high-pressure water is used to flush away coal dust to promote the development of fractures and ensure that the diameter of the enlarged section is uniform. After the enlargement is completed, the drill bit is closed and the hole is slowly withdrawn.

6. The method for mechanical borehole expansion and pressure relief in coal mines based on multi-dimensional closed-loop monitoring according to claim 1, characterized in that, The monitoring of different safety indicators through a multi-dimensional closed-loop monitoring system specifically includes the following steps: By setting up different monitoring devices in different areas and setting monitoring thresholds, different safety indicators are monitored, including: drill cuttings volume, coal stress, micro-vibration, and surrounding rock deformation. Real-time monitoring data of different safety indicators are collected in different dimensions, and the monitoring data is integrated and analyzed. The monitoring data is assessed for safety by using monitoring thresholds to obtain results of normal, warning, or exceeding limits. If a warning is issued, a pop-up message will appear; if the limit is exceeded, an audible and visual alarm will be triggered. The hole enlargement steps are categorized and adjusted. Monitoring is strengthened immediately after the adjustment is implemented. If the data returns to the safe threshold, construction continues; otherwise, the adjustment is repeated. After construction, continuous monitoring was conducted for a set number of days, focusing on observing the stability of surrounding rock deformation, microseismic energy release, and coal stress balance. All data and adjustment records were archived, and a correlation model of "geological conditions - construction parameters - monitoring results" was established to provide a basis for parameter optimization in subsequent work.

7. The method for mechanical borehole expansion and pressure relief in coal mines based on multi-dimensional closed-loop monitoring according to claim 6, characterized in that, The method involves setting up different monitoring devices in different areas and establishing monitoring thresholds to monitor different safety indicators. Specifically: Drill cuttings monitoring: A dedicated collection area is set up below the opening of each pressure relief borehole, with a leak-proof mat laid out. Drill cuttings are collected using high-temperature resistant adhesive collection bags, weighed using an electronic scale, and the collection height is measured using a tape measure. The safe threshold for drill cuttings is: the average drill cuttings per hole is ≥2005kg, the warning threshold is: the average drill cuttings per hole is 1500-2005kg, and the over-limit threshold is: the average drill cuttings per hole is <1500kg. Coal stress monitoring: At least three monitoring sections are set up on the main flank, with at least seven stress gauges installed on each section, at monitoring depths of 2m, 4m, 6m, 8m, 10m, 12m, and 14m respectively; at least two stress gauges are installed on the corresponding sections of the auxiliary flank, at monitoring depths of 2m and 3m respectively, with borehole diameters... The drilled holes were filled and fixed with epoxy resin and left to cure for 24 hours. The safe threshold for coal body stress is: coal body stress reduction ≥ 45%, and stress increase in the anchoring zone ≤ 1 MPa. The warning threshold is: coal body stress reduction 30%-45%, and stress increase in the anchoring zone 1-2 MPa. The over-limit threshold is: coal body stress reduction < 30%, and stress increase in the anchoring zone > 2 MPa. Microseismic monitoring: One seismic sensor is installed 5m from each end of the pressure relief area. The sensor is fixed to the anchor bolts on the top slab. Four probes are evenly distributed on the top, bottom, left, and right sides to form a 50m coverage circle. The sensor is connected to the main control unit. The microseismic safety threshold is: total energy reduction ≥52%, no ≥10 5 The warning threshold for a strong earthquake event J is: a 20%-52% reduction in total energy, and a 10% warning threshold for sporadic occurrences. 4 -10 5 Event J has the following over-limit thresholds: total energy reduction <20%, ≥10 5 J has ≥2 events; Surrounding rock deformation monitoring: One monitoring section is set up every 5m, and additional sections are set up at both ends by 10m. Each section uses a cross-point layout method to set monitoring points at the center of the two sides, the top plate of the rock stratum, and the bottom plate of the rock stratum. The safe threshold for surrounding rock deformation is: the distance between the two sides ≤240mm and the distance between the top plate of the rock stratum and the bottom plate of the rock stratum ≤350mm. The warning threshold is: the distance between the two sides 200-240mm and the distance between the top plate of the rock stratum and the bottom plate of the rock stratum 300-350mm. The over-limit threshold is: the distance between the two sides >240mm and the distance between the top plate of the rock stratum and the bottom plate of the rock stratum >350mm. Crack detection: The crack detection is carried out on the same cross-section as the coal seam stress monitoring section, with one crack detection point constructed on each cross-section. The detection hole with a depth of 5m should be ≥1m away from the pressure relief drill hole; the safety threshold for crack detection is: the loosening zone is 1.7-1.8m, the warning threshold is: the loosening zone is 1.6-1.7m or 1.8-1.9m, and the over-limit threshold is: the loosening zone is <1.6m or >1.9m.

8. The method for mechanical borehole expansion and pressure relief in coal mines based on multi-dimensional closed-loop monitoring according to claim 6, characterized in that, The real-time collection of monitoring data for different safety indicators across multiple dimensions specifically includes: Drill cuttings: Stop collecting coal dust and weigh it every 1m of drilling or reaming, record the depth and time, and calculate the total weight and average value after the construction is completed; Coal stress: 8-hour baseline values ​​were collected 24 hours before construction. Coal stress was continuously collected at a frequency of 1Hz during construction, and a curve was generated every 30 minutes. During the borehole expansion stage, the depth of 7-20m was monitored. Coal stress was collected 2 hours / time within 24 hours after construction and once / day thereafter. Microseismic data: The equipment is started 12 hours before construction, and microseismic data is continuously collected at a sampling frequency of 1000Hz. Data with a seismic intensity ≥10 is automatically filtered. 3 J event and push to the terminal; Rock deformation: Baseline values ​​were collected 24 hours before construction, and the baseline values ​​were averaged after being repeated 3 times. Rock deformation data were collected every 6 hours during construction. Rock deformation was measured immediately after hole enlargement and drilling withdrawal. Rock deformation data were collected once a day for the first 7 days after construction and once every 3 days thereafter. Fracture detection: The first detection is carried out 24 hours after the single hole is drilled, and the second detection is carried out 7 days after all holes are completed, with fracture images captured simultaneously.

9. The method for mechanical borehole expansion and pressure relief in coal mines based on multi-dimensional closed-loop monitoring according to claim 6, characterized in that, The integration and analysis of the monitoring data specifically includes the following steps: Data transmission and aggregation: Data is automatically collected and transmitted to the field control terminal via wired connection. Manually collected data is entered in real time, forming a related database of "time-location-multi-dimensional data". Cross-validation analysis: Compare the amount of drill cuttings, stress reduction at corresponding depth, and micro-vibration energy of the same borehole to identify data discrepancies and verify the quality of hole enlargement or equipment condition; Overall regional verification: By comparing monitoring data from multiple boreholes, we can identify areas with weak pressure relief or excessive disturbance. Trend prediction: Fit the change curve of continuous 24-hour data to predict whether it may exceed the limit in the future and avoid risks in advance.

10. The method for mechanical borehole expansion and pressure relief in coal mines based on multi-dimensional closed-loop monitoring according to claim 6, characterized in that, The classification and adjustment hole enlargement step is specifically as follows: Insufficient pressure relief: Check the quality of the hole enlargement, repeat the enlargement process 1-2 times, increase the high-pressure hydraulic pressure to 12-15MPa, extend the flushing time, and if necessary, increase the drilling density or extend the enlargement length to 14-15m. Risks of excessive pressure relief or support: Immediately stop borehole reaming, shorten the reaming length to 11-12m, and adjust the number of reciprocating borehole reaming cycles to 1; add anchor cables to areas with excessive deformation. Warning: The monitoring frequency for the corresponding dimension will be doubled, equipment and construction parameters will be checked, and construction will be suspended until the data returns to the safe threshold.

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