Cross-period multi-working face optical fiber monitoring method based on proximal surface entity coal roadway drilling

Abstract

The application discloses a cross-period multi-working face optical fiber monitoring method based on an adjacent surface entity coal roadway drilling, which comprises the following steps: S1, selecting an entity coal roadway of a working face to be connected and mined as a monitoring carrier roadway; S2, continuously arranging a tendency directional drilling hole along the carrier roadway; S3, constructing a plurality of roof tendency directional long drilling holes, and the drilling holes extend perpendicularly to the advancing direction of the working face; S4, arranging a DAS optical fiber in each tendency directional long drilling hole; S5, establishing a panel zonal three-dimensional monitoring network by relying on the DAS optical fiber; S6, collecting an acoustic signal of the DAS optical fiber, and realizing full-period monitoring of the working face; S7, judging and analyzing a hanging roof range of a boundary roof of a goaf, and guiding targeted treatment; and S8, after a goaf side optical cable is broken, monitoring the back overburden by using an entity coal side optical fiber. The application solves the problems that an existing monitoring system cannot cross the working face to relay monitoring and long-term monitoring of the goaf, a large panel area lacks a segmented arrangement scheme, and a hanging roof area cannot be identified to guide treatment.

Description

Technical Field

[0001] This invention belongs to the field of monitoring of rockburst disasters in coal mine panels and monitoring of dynamic evolution of overburden caused by joint mining in multiple working faces. Specifically, it relates to a cross-cycle multi-working-face fiber optic monitoring method based on boreholes in adjacent coal roadways. Background Technology

[0002] With the intensive mining of coal mining panels, large panels often have several or even more than ten consecutive working faces. The disturbances from the excavation of adjacent working faces, the disturbances from the mining of the current working face, and the compaction and sliding of the overlying rock in the goaf can all overlap, easily inducing high-energy mine tremors and rockburst disasters. Currently, DAS fiber optic monitoring and microseismic monitoring systems generally adopt an independent deployment mode for a single working face, which has several shortcomings: 1. Monitoring systems are mostly deployed in the current mining face roadways and adjacent roadways, located in the mining-affected area. The co-location of mining operations and monitoring equipment in the same area poses high risks of equipment damage and personnel safety during maintenance. After mining ends, the microseismic equipment is moved, rendering monitoring impossible, and most fiber optic cables break, rendering the monitoring system unusable. When the next mining face begins, monitoring boreholes need to be re-drilled and fiber optic cables repeatedly laid, resulting in significant redundant investment. 2. Existing monitoring networks struggle to achieve cross-face relay monitoring, failing to continuously capture the evolution of overburden disturbance under the complete timeline of "previous mining face → adjacent mining face → adjacent mining face → long-term compaction of the goaf," and lack long-term monitoring methods for the overburden in the goaf area. 3. Conventional fiber optic monitoring often uses strike boreholes deployed along the working face advance direction, making it difficult to form a strip-shaped, full-area monitoring network covering multiple continuous working faces, resulting in insufficient energy event capture capabilities at the large panel scale. 4. Large working faces in a large area have numerous locations. Deploying monitoring across the entire area at once would require a huge upfront investment. Existing monitoring solutions lack a segmented deployment approach suitable for large areas, making it difficult to balance monitoring coverage with project costs. 5. Existing monitoring methods struggle to accurately identify overhanging roof areas at the boundaries of goaf areas, failing to effectively delineate the morphology of surrounding rock damage at the goaf edges, and thus failing to provide targeted treatment data for the next working face's goaf tunnel excavation.

[0003] In existing technologies, some solutions utilize directional drilling in adjacent roadways to carry out hydraulic fracturing and depressurization treatment of the roof. However, these boreholes are merely used as channels for rock strata modification. After the drilling and fracturing processes are completed, they are mostly left idle and abandoned. There is no long-term monitoring array built on these boreholes for continuous mining of multiple working faces in the panel. Furthermore, permanent channels such as stable solid coal roadways or drainage roadways within coal pillars at the panel boundary have not been fully utilized to establish a cross-working-face monitoring system that isolates the production area from the monitoring area. There is also no complete set of methods for identifying roof overhangs in goaf areas and guiding the management of goaf hazards in adjacent areas based on cross-working-face monitoring. Summary of the Invention

[0004] The purpose of this invention is to provide a cross-cycle multi-working-face fiber optic monitoring method based on adjacent physical coal roadway boreholes, which solves the problems of existing monitoring systems being unable to perform relay monitoring across working faces and long-term monitoring of goaf areas, lacking segmented deployment schemes in large-scale monitoring areas, and being unable to identify overhanging areas to guide governance.

[0005] The technical solution adopted in this invention is a cross-cycle multi-working-face fiber optic monitoring method based on adjacent solid coal roadway boreholes, comprising the following steps: S1. Select the actual coal roadway of the working face to be mined as the monitoring carrier roadway; S2. Continuously lay out inclined directional boreholes along the carrier roadway; S3. Multiple long, inclined directional boreholes are drilled into the roof slab, with the boreholes extending perpendicular to the working face's advancing direction. S4. DAS optical fibers are laid into each inclined long borehole. S5. A three-dimensional monitoring network in the panel area is constructed by relying on multiple DAS optical fibers inclined into the borehole. S6. Acquire DAS fiber optic acoustic signals to achieve full-cycle monitoring of the working face; S7. Assess the extent of roof overhang at the boundary of the goaf to guide targeted remediation; S8. After the optical cable on the goaf side breaks, the optical fiber on the solid coal side is used to continuously monitor the overburden behind it.

[0006] The invention is further characterized by: In S1, the carrier roadway is the main coal roadway of the next or the next working face to be mined, or the drainage roadway at the panel boundary; monitoring and demodulation equipment and fiber optic output terminals are installed in the carrier roadway to physically isolate the monitoring area from the mining and production area; the carrier roadway is a complete solid coal roadway or a permanent channel at the panel boundary, which is not subject to strong mining disturbances of the current working face for a long time, and serves as a permanent operation and maintenance channel for the monitoring system.

[0007] In S2 and S3, monitoring arrays are planned differently based on the size of the panel: for small panels, directional boreholes are continuously deployed along the carrier roadway to achieve full coverage; for large panels, a strip monitoring array is deployed every 2 to 3 consecutive working faces, with a service life of 2 to 3 years for each array. The monitoring ranges of adjacent monitoring arrays overlap to ensure that there are no blind spots in panel monitoring; directional optical fibers are also deployed inside the working face to form a three-dimensional monitoring network together with the DAS optical fibers in the directional boreholes; the directional boreholes are monitoring boreholes constructed specifically for this purpose, or directional boreholes for roof disaster management constructed in advance.

[0008] In S2 and S3, multiple long dipping-oriented boreholes are drilled at intervals along the direction of the carrier roadway based on the effective monitoring radius of the DAS optical fiber. The effective monitoring radius is determined according to the vibration energy level of the monitoring target. It is 100m~150m for monitoring micro-fractures caused by conventional mining and 300m~500m for monitoring large energy events. The spacing between adjacent dipping-oriented boreholes is designed according to the effective monitoring radius of the DAS optical fiber, so that the monitoring range of each borehole overlaps with each other and eliminates blind spots in panel monitoring.

[0009] In S4, the DAS optical fiber is inserted into the inclined directional borehole using a flexible tube integrated pushing process. The DAS optical fiber is arranged along the entire borehole, with one end remaining in the solid coal carrier roadway and the other end extending to the roof area of ​​the target working face. When the DAS optical fiber is laid out, a relaxation deformation margin is reserved to buffer the tensile load on the optical fiber caused by the deformation of the surrounding rock.

[0010] In S4, the relaxation deformation allowance reserved for DAS optical fiber is 1% to 2% of the borehole length. This is used to buffer the tensile load on the optical fiber caused by the deformation of the surrounding rock. When the deformation of the surrounding rock generates a tensile load, the relaxation section will expand first to absorb the tensile load, so as to avoid the tensile load being directly transmitted to the optical fiber body inside the borehole and ensure that the optical fiber is not broken during the deformation of the surrounding rock.

[0011] In S5, multiple independent directional boreholes contain DAS optical fibers forming a strip-shaped monitoring network. Each monitoring channel is independent of the others, and the monitoring ranges of adjacent boreholes overlap to eliminate blind spots in panel monitoring. Combined with the directional optical fibers within the working face, a spatial three-dimensional monitoring system is formed. The strip-shaped three-dimensional monitoring network is linked and integrated with the optical fiber monitoring system deployed in the current production working face roadway. The regional directional borehole monitoring network is responsible for capturing large-scale events at the panel scale and dynamically judging the boundaries of the goaf. The optical fibers within the working face roadway are responsible for localized, refined monitoring of the mining space. The data fusion of the two improves the accuracy of micro-fracture location.

[0012] Specifically, S6 involves continuously collecting DAS fiber optic acoustic signals throughout the entire mining process across multiple working faces, enabling full-cycle monitoring of pre-mining disturbances, in-mining overburden fracturing, and post-mining goaf overburden long-term evolution. It identifies high-energy micro-fracture events in the panel area and conducts early warning of rockburst hazards when the micro-seismic energy per unit time exceeds a set threshold or when a high-energy event accumulation trend occurs.

[0013] S7 specifically refers to: relying on the vibration signals continuously collected by the cross-working face monitoring array, judging the range of roof overhang and high stress concentration areas by the spatial concentration degree and energy release rate of micro-fracture events at the boundary of the goaf, outlining the failure mode of the surrounding rock at the edge of the goaf, and implementing key pressure relief and roof cutting treatment in the goaf danger area during the next working face goaf roadway excavation stage based on the judgment results.

[0014] S8 specifically refers to the following: When the optical cable of the directional borehole close to the goaf breaks due to the mining of the working face, the DAS optical fiber segment on the solid coal side maintains normal acquisition and continuously receives vibration signals generated by the collapse of the overlying rock, interlayer slippage, and compaction in the goaf, so as to realize long-term observation of the overlying rock evolution in the goaf after the mining of the working face is completed.

[0015] The beneficial effects of this invention are: (1) Safety advantages: The monitoring equipment and operation and maintenance channels are arranged in the actual coal roadway of the working face to be mined, which is isolated from the mining operation area. This avoids the deployment of monitoring facilities in the roadway and mining face, and significantly reduces the safety risks of underground equipment inspection and maintenance.

[0016] (2) Adapt to different panel sizes and balance investment costs: small panels can be continuously deployed with full coverage at one time; when there are many working faces in large panels, a segmented deployment scheme with intervals of 2 to 3 working faces is adopted, and a single monitoring system can be used for 2 to 3 years without large-scale investment at one time; daily maintenance only focuses on the main optical fiber in the physical carrier roadway, and optical fiber in the working face is provided as needed, greatly reducing the investment in repetitive projects.

[0017] (3) Realize full life cycle monitoring: A monitoring network serves multiple successive working faces in sequence, fully covering the entire process of tunneling disturbance, mining fracture, and goaf compaction evolution, making up for the shortcomings of traditional monitoring which only monitors the mining stage.

[0018] (4) Unique fault-tolerant monitoring capability in goaf: After the optical cable on the goaf side breaks, the DAS optical fiber in the solid coal section can still work normally, continuously capturing the overburden sliding and compaction signals in the goaf behind the face, realizing long-term post-mining observation of the working face.

[0019] (5) Three-dimensional monitoring network to capture large energy events in the whole area: the directional drilling array is combined with the working face direction optical fiber to form a three-dimensional monitoring system, eliminate blind spots in panel monitoring, and improve the accuracy of identification and location of large energy mine seismic events at the panel scale.

[0020] (6) Forming a monitoring-treatment closed loop: It can dynamically identify the overhanging area of ​​the roof at the boundary of the goaf and delineate the damage pattern of the surrounding rock at the edge of the goaf; based on the monitoring results, the dangerous area can be treated in the next working face during the goaf tunneling process, and the monitoring and early warning results can be directly transformed into the basis for disaster prevention and control, solving the pain point of traditional monitoring that "only warns but is difficult to implement". Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the cross-cycle multi-working-face fiber optic monitoring method based on adjacent solid coal roadway drilling according to the present invention. Figure 2 This is a schematic diagram of a large disk segmented monitoring array in an embodiment of the present invention; Figure 3 This is a schematic diagram of the cross-sectional view of the directional drilling and the direction fiber optic three-dimensional monitoring in an embodiment of the present invention.

[0022] In the figure: 1. Panel boundary; 2. First working face; 3. Second working face; 4. Third working face; 5. Solid coal carrier roadway; 6. Inclined directional borehole for DAS optical fiber deployment; 7. Goaf; 8. Goaf boundary overhang area. Detailed Implementation

[0023] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0024] This invention relates to a cross-cycle, multi-face fiber optic monitoring method based on adjacent-face solid coal roadway boreholes, such as... Figure 1 As shown, it includes the following steps: S1. Select the actual coal roadway of the working face to be mined as the monitoring carrier roadway; In S1, the carrier roadway is the main coal roadway of the next or the next working face to be mined, or the drainage roadway at the panel boundary. Monitoring and demodulation equipment and fiber optic output terminals are installed in the carrier roadway to physically isolate the monitoring area from the mining and production area. The carrier roadway is a complete solid coal roadway or a permanent passage at the panel boundary, which is not subject to strong mining disturbances from the current working face for a long time, and serves as a permanent operation and maintenance passage for the monitoring system. By arranging the monitoring equipment and operation and maintenance passage in the solid coal roadway of the working face to be mined, and isolating it from the mining and operation area, the deployment of monitoring facilities in the goaf roadway and the longwall mining face is avoided, which significantly reduces the safety risks of underground equipment inspection and maintenance, and solves the problems of easy equipment damage and high personnel safety risks when the existing monitoring system is deployed in the mining disturbance area. S2. Continuously lay out inclined directional boreholes along the carrier roadway; S3. Multiple long, inclined directional boreholes are drilled into the roof slab, with the boreholes extending perpendicular to the working face's advancing direction. In S2 and S3, monitoring arrays are planned differently based on the size of the panel: for small panels, directional boreholes are continuously deployed along the carrier roadway to achieve full coverage; for large panels, a strip-shaped monitoring array is deployed every 2-3 consecutive working faces, with a service life of 2-3 years for each array. The monitoring ranges of adjacent arrays overlap to ensure no blind spots in panel monitoring; directional optical fibers are also deployed inside the working face to form a three-dimensional monitoring network together with the DAS optical fibers in the directional boreholes; the directional boreholes are specially constructed monitoring boreholes, or... Pre-constructed directional boreholes for roof disaster mitigation; through a segmented deployment scheme, large panels do not need to be fully invested at once. A single monitoring array can independently serve for 2-3 years to cover the entire mining process of 2-3 working faces. When subsequent working faces are mined, there are already existing borehole arrays available for reuse. Routine maintenance only requires key maintenance of the main optical fiber in the physical carrier roadway, which greatly reduces the investment in repetitive projects. At the same time, the pre-constructed directional boreholes for roof disaster mitigation can be directly reused as DAS fiber optic monitoring boreholes, realizing multiple uses for one borehole and avoiding project waste caused by borehole abandonment. In S2 and S3, multiple long dipping-oriented boreholes are drilled at intervals along the direction of the carrier roadway based on the effective monitoring radius of the DAS optical fiber. The effective monitoring radius is determined according to the vibration energy level of the monitoring target. It is 100m~150m for monitoring micro-fractures caused by conventional mining and 300m~500m for monitoring large-energy events. The spacing between adjacent dipping-oriented boreholes is designed according to the effective monitoring radius of the DAS optical fiber, so that the monitoring range of each borehole overlaps with each other and eliminates blind spots in panel monitoring. By combining the dipping-oriented borehole array with the working face direction optical fiber, a three-dimensional monitoring system of dipping + direction is formed, which overcomes the limitation of conventional direction boreholes that cannot cover multiple continuous working faces, eliminates large-scale monitoring blind spots in the panel, and improves the identification and location accuracy of large-energy mine seismic events at the panel scale. S4. DAS optical fibers are laid into each inclined long borehole. In S4, the DAS optical fiber is inserted into the inclined directional borehole using a flexible tube integrated pushing process. The DAS optical fiber is arranged along the entire borehole, with one end remaining in the solid coal carrier roadway and the other end extending to the roof area of ​​the target working face. When the DAS optical fiber is laid out, a relaxation deformation margin is reserved to buffer the tensile load on the optical fiber caused by the deformation of the surrounding rock. In S4, the relaxation deformation margin reserved for DAS optical fiber is 1% to 2% of the borehole length. This margin is used to buffer the tensile load on the optical fiber caused by the deformation of the surrounding rock. When the surrounding rock deformation generates tensile load, the relaxation section will expand first to absorb the tensile load, preventing the tensile load from being directly transmitted to the optical fiber body inside the borehole. This ensures that the optical fiber is not broken during the deformation of the surrounding rock. By reserving the relaxation deformation margin, when the rock strata are deformed and the borehole is subjected to axial tension due to mining later, the relaxation section will expand first to absorb the deformation, preventing the tensile load from being transmitted to the optical fiber body inside the hole. This ensures that the optical fiber does not break and the signal is continuous throughout the entire monitoring cycle, so that the optical fiber inside the borehole can continue to work after the mining is completed. S5. A three-dimensional monitoring network in the panel area is constructed by relying on multiple DAS optical fibers inclined into the borehole. In S5, multiple independent dipping-oriented DAS optical fibers form a strip-shaped monitoring network. Each monitoring channel is independent of the others, and the monitoring ranges of adjacent boreholes overlap to eliminate blind spots in panel monitoring. Combined with the directional optical fibers in the working face, a spatial three-dimensional monitoring system is formed. The strip-shaped three-dimensional monitoring network is linked and integrated with the optical fiber monitoring system deployed in the current production working face roadway. The regional dipping borehole monitoring network is responsible for capturing large-scale events at the panel scale and dynamically judging the boundary of the goaf. The optical fibers in the working face roadway are responsible for local fine-grained monitoring of the mining space. The data fusion of the two improves the accuracy of micro-fracture location. Through multi-channel independent monitoring and data linkage and integration, it not only achieves wide-area capture of large-energy events at the panel scale, but also ensures accurate location of local seismic sources in the mining space, solving the problem of insufficient location accuracy of large-energy events in conventional single deployment mode. S6. Acquire DAS fiber optic acoustic signals to achieve full-cycle monitoring of the working face; Specifically, S6 involves continuously acquiring DAS fiber optic acoustic signals throughout the entire mining process across multiple working faces, enabling full-cycle monitoring of pre-mining disturbances, mining overburden fracturing, and post-mining goaf overburden long-term evolution. It identifies high-energy micro-fracture events in the panel and conducts early warning of rockburst hazards when the micro-seismic energy per unit time exceeds a set threshold or a high-energy event accumulation trend occurs. A single monitoring network sequentially serves multiple consecutive working faces, fully covering the entire process of tunneling disturbances, mining fracturing, and goaf compaction evolution, making up for the shortcomings of traditional monitoring that only monitors the mining stage, and achieving long-term monitoring of working faces across cycles. S7. Assess the extent of roof overhang at the boundary of the goaf to guide targeted remediation; Specifically, S7 involves: relying on the vibration signals continuously collected by the cross-working-face monitoring array, analyzing the spatial concentration and energy release rate of micro-fracture events at the goaf boundary to determine the range of roof overhang and high-stress concentration areas, outlining the failure morphology of the surrounding rock at the goaf edge, and implementing key pressure relief and roof cutting treatment in the goaf roadway excavation stage of the next working face based on the assessment results; dynamically identifying the roof overhang area at the goaf boundary through the cross-working-face monitoring array, directly transforming the monitoring and early warning results into a basis for disaster prevention and control, solving the pain point of traditional monitoring that "only provides early warnings but is difficult to implement", and forming a monitoring-treatment closed loop; S8. After the optical cable on the goaf side breaks, the optical fiber on the solid coal side is used to continuously monitor the overburden behind it. Specifically, S8 involves the following: When the optical cable of the directional borehole near the goaf breaks during the mining of the working face, the DAS optical fiber segment remaining on the solid coal side continues to acquire data, continuously receiving vibration signals generated by overburden collapse, interlayer slippage, and compaction within the goaf. This enables long-term observation of the overburden evolution in the goaf after mining is completed. Through the goaf-tolerant monitoring capability, the DAS optical fiber in the solid coal section can still function normally after the optical cable on the goaf side breaks, continuously capturing overburden slippage and compaction signals behind the face. This achieves long-term post-mining observation of the working face, solving the problems of traditional monitoring systems being directly rendered obsolete after mining and the inability to obtain long-term patterns of overburden migration in the goaf.

[0025] Example 1 The fiber optic monitoring method for cross-cycle multi-working-face based on adjacent-face solid coal roadway boreholes proposed in this embodiment includes the following steps: A large mining area comprises seven consecutive working faces, with a total strike length of 3500m and individual working face lengths of 300m. The coal transport roadway of the third working face to be mined was selected as the carrier roadway. A segmented deployment scheme was adopted, with three monitoring arrays deployed at the third, fifth, and seventh working faces. Each array covered 2-3 working faces, with a 100m overlap between arrays. Each array underwent directional drilling at 250-300m intervals along the carrier roadway, with a depth of 800-1000m. After deploying DAS fiber optic cables, a strip-shaped monitoring network was formed, providing continuous service for three years, covering the entire mining process of all seven working faces. During the mining phase, the network successfully captured a cluster of microseismic events at the goaf boundary, identified two areas of roof overhang hazard, and guided the early construction of pressure relief boreholes in adjacent goaf roadways, ensuring safe tunneling.

[0026] Example 2 The fiber optic monitoring method for cross-cycle multi-working-face based on adjacent-face solid coal roadway boreholes proposed in this embodiment includes the following steps: A small mining panel has two consecutive working faces, with a total strike length of 2000m and a single working face length of 300m. The return airway of the next working face is selected as the carrier roadway. Three dipping directional boreholes, each 700m deep, are continuously drilled at once, all equipped with DAS fiber optic cables. One monitoring system serves the consecutive mining of both working faces, with a monitoring cycle of 2 years, saving approximately 60% of the engineering investment compared to traditional independent monitoring of a single working face.

[0027] Example 3 The fiber optic monitoring method for cross-cycle multi-working-face based on adjacent-face solid coal roadway boreholes proposed in this embodiment includes the following steps: S1. Selection of Monitoring Carrier Roadway: A small panel has two consecutive working faces, with a total length of 1500m and a single working face length of 200m. The return airway of the first working face to be mined is selected as the monitoring carrier roadway. This roadway is a complete solid coal roadway and is not subject to strong mining disturbances from the current working face. All monitoring and demodulation equipment and fiber optic cables are arranged within this carrier roadway, physically isolating the monitoring area from the mining production area and serving as a permanent maintenance channel for the monitoring system.

[0028] S2. Monitoring Array Zoning Planning: This area is a small area (number of working faces ≤ 3). A continuous directional drilling scheme along the carrier roadway is adopted to achieve full coverage in one go. Three directional drilling locations are planned within the carrier roadway, evenly distributed at 100m intervals along the roadway direction, with the drilling extending perpendicular to the working face advance direction. At the same time, directional optical fibers are deployed inside the working face to form a three-dimensional monitoring network together with the DAS optical fibers in the directional drilling.

[0029] S3. Dip-direction drilling: Based on the effective monitoring radius of the DAS fiber optic cable (100m for conventional mining-induced micro-fracture monitoring), three dip-direction long boreholes are drilled at 100m intervals along the direction of the carrier roadway, with a single borehole depth of 600m. The boreholes extend perpendicular to the working face advance direction into the target strata of the overburden. The monitoring ranges of each borehole overlap to eliminate blind spots in the panel monitoring. The three dip-direction boreholes are arranged to form a continuous strip-shaped monitoring array, jointly covering two successive working faces within the panel.

[0030] S4. DAS Fiber Deployment: DAS fibers are deployed into the long boreholes in each direction using a flexible, integrated casing-type push-down process. The DAS fibers are laid along the entire length of the borehole, with one end remaining within the solid coal carrier roadway and the other end extending to the roof area of ​​the target working face. A relaxation deformation allowance of 1% of the borehole length (6m) is reserved during DAS fiber deployment to buffer the tensile load on the fiber caused by surrounding rock deformation. When tensile loads are generated by surrounding rock deformation, the relaxed section expands first to absorb the tensile load, preventing the tensile load from being directly transferred to the fiber body inside the borehole, thus ensuring that the fiber is not broken during surrounding rock deformation.

[0031] S5. Establishing a Panel-Style Three-Dimensional Monitoring Network: After the DAS optical fibers in the three directional boreholes are fully deployed, a panel-style three-dimensional monitoring network will be established based on the DAS optical fibers in multiple directional boreholes. This network consists of multiple independent directional boreholes forming a strip-shaped monitoring system. Each monitoring channel is independent, while the monitoring ranges of adjacent boreholes overlap, eliminating blind spots in panel monitoring. Combined with the directional optical fibers within the working face, this forms a spatial three-dimensional monitoring system. This panel-style monitoring network will be linked and integrated with the optical fiber monitoring system deployed in the current production working face roadways. The regional directional borehole monitoring network will be responsible for capturing large-scale events at the panel scale and dynamically assessing the boundaries of the goaf, while the optical fibers within the working face roadways will be responsible for localized, refined monitoring of the mining space.

[0032] S6. Continuous Monitoring Throughout the Entire Lifecycle: DAS fiber optic acoustic signals are continuously acquired throughout the entire mining process across two working faces to achieve full-cycle monitoring, including pre-mining disturbance monitoring, in-mining overburden fracturing monitoring, and post-mining long-term overburden evolution monitoring, identifying high-energy micro-fracture events in the panel. The monitoring cycle for this panel is two years. When the microseismic energy per unit time exceeds a set threshold or a trend of high-energy event accumulation occurs, a rockburst hazard warning is issued.

[0033] S7. Assessment and Targeted Treatment Guidance for Overhanging Roofs at Goaf Boundaries: Based on the continuous collection of vibration signals from cross-working face monitoring arrays, the extent of overhanging roofs and high-stress concentration areas are assessed by analyzing the spatial concentration and energy release rate of micro-fracture events at the goaf boundary, thus outlining the failure morphology of the surrounding rock at the goaf edge. Based on the assessment results, targeted pressure relief and roof cutting treatment are implemented in the overhanging danger areas during the next working face goaf roadway excavation stage.

[0034] S8. Goaf Overburden Fault Tolerance Monitoring: When the optical cable of the directional borehole near the goaf breaks due to mining of the working face, the DAS optical fiber segment remaining on the solid coal side continues to collect data normally, continuously receiving vibration signals generated by overburden collapse, interlayer slippage, and compaction within the goaf. This enables long-term observation of the evolution of the goaf overburden after mining of the working face is completed. In this embodiment, one monitoring system serves two working faces in succession, saving approximately 60% of the engineering investment compared to traditional independent monitoring of a single working face.

[0035] Example 4 The fiber optic monitoring method for cross-cycle multi-working-face based on adjacent-face solid coal roadway boreholes proposed in this embodiment includes the following steps: S1. Selection of Monitoring Carrier Roadway: A medium-sized panel has 5 consecutive working faces, with a total length of 2500m and a single working face length of 250m. The main coal roadway of the second working face to be mined is selected as the monitoring carrier roadway. This roadway is a complete solid coal roadway and is not subject to strong mining disturbances from the current working face. All monitoring and demodulation equipment and fiber optic cables are arranged in this carrier roadway, physically isolating the monitoring area from the mining production area, serving as a permanent operation and maintenance channel for the monitoring system.

[0036] S2. Monitoring Array Zoning Plan: This is a medium-sized monitoring area, employing a segmented deployment scheme. Two sets of strip-shaped monitoring arrays are deployed at the second and fourth working faces, each covering 2-3 working faces. The service life of a single array is 2.5 years. The monitoring ranges of adjacent monitoring arrays are designed with an 80m overlap area to ensure no blind spots in the monitoring of the area. Simultaneously, directional optical fibers are deployed inside the working faces to form a three-dimensional monitoring network together with the DAS optical fibers in the directional boreholes.

[0037] S3. Dip-directional drilling: Based on the effective monitoring radius of the DAS fiber optic cable (125m for conventional mining-induced micro-fracture monitoring), multiple dip-directional long boreholes are drilled at 125m intervals along the direction of the carrier roadway, with a single borehole depth of 800m. The boreholes extend perpendicular to the working face advance direction into the target overburden strata. The monitoring ranges of each borehole overlap to eliminate blind spots in the panel monitoring. Multiple dip-directional boreholes are arranged to form a continuous strip-shaped monitoring array, jointly covering five consecutive working faces within the panel. The dip-directional boreholes are specially constructed monitoring boreholes.

[0038] S4. DAS Fiber Deployment: DAS fibers are deployed into the long boreholes in each direction using a flexible, integrated casing-type push-down process. The DAS fibers are laid along the entire length of the borehole, with one end remaining within the solid coal carrier roadway and the other end extending to the roof area of ​​the target working face. A relaxation deformation allowance of 1.5% (12m) of the borehole length is reserved during DAS fiber deployment to buffer the tensile load on the fiber caused by surrounding rock deformation. When tensile loads are generated by surrounding rock deformation, the relaxed section expands first to absorb the tensile load, preventing the tensile load from being directly transferred to the fiber body inside the borehole, thus ensuring that the fiber is not broken during surrounding rock deformation.

[0039] S5. Establish a panel-scale strip-shaped three-dimensional monitoring network: After all DAS optical fibers are deployed in multiple directional boreholes, a panel-scale strip-shaped three-dimensional monitoring network is established based on these fibers. The strip-shaped monitoring network consists of multiple independent directional boreholes, with each monitoring channel operating independently. The monitoring ranges of adjacent boreholes overlap, eliminating blind spots in panel monitoring. This network, in conjunction with the fiber optic cables within the working face, forms a spatial three-dimensional monitoring system. This panel-scale strip-shaped monitoring network is linked and integrated with the fiber optic monitoring system deployed in the current production working face roadways. The regional directional borehole monitoring network is responsible for capturing large-scale events at the panel scale and dynamically assessing the boundaries of the goaf, while the fiber optic cables within the working face roadways are responsible for localized, refined monitoring of the mining space.

[0040] S6. Continuous Monitoring Throughout the Entire Lifecycle: DAS fiber optic acoustic signals are continuously acquired throughout the entire mining process across five working faces to achieve full-cycle monitoring of pre-mining disturbance, in-mining overburden fracturing, and post-mining goaf overburden long-term evolution, identifying high-energy micro-fracture events in the panel. When the micro-seismic energy per unit time exceeds a set threshold or a trend of high-energy event accumulation occurs, a rockburst hazard warning is issued.

[0041] S7. Assessment and Targeted Treatment Guidance for Overhanging Roofs at Goaf Boundaries: Based on the continuous collection of vibration signals from cross-working face monitoring arrays, the extent of overhanging roofs and high-stress concentration areas are assessed by analyzing the spatial concentration and energy release rate of micro-fracture events at the goaf boundary, thus outlining the failure morphology of the surrounding rock at the goaf edge. Based on the assessment results, targeted pressure relief and roof cutting treatment are implemented in the overhanging danger areas during the next working face goaf roadway excavation stage.

[0042] S8. Goaf Overburden Fault Tolerance Monitoring: When the optical cable of the directional borehole near the goaf breaks due to the back mining of the working face, the DAS optical fiber segment remaining on the solid coal side continues to collect data normally, continuously receiving vibration signals generated by overburden collapse, interlayer slippage, and compaction within the goaf, enabling long-term observation of the evolution of the goaf overburden after the working face has been back mined. In this embodiment, two sets of monitoring arrays provide relay service, covering the entire mining cycle of five working faces.

[0043] Example 5 The fiber optic monitoring method for cross-cycle multi-working-face based on adjacent-face solid coal roadway boreholes proposed in this embodiment includes the following steps: S1. Selection of Monitoring Carrier Roadway: A large panel has 8 consecutive working faces, with a total strike length of 4000m and a single working face length of 300m. The main coal roadway of the third working face to be mined is selected as the monitoring carrier roadway. This roadway is a complete solid coal roadway and is not subject to strong mining disturbances from the current working face. All monitoring and demodulation equipment and fiber optic cables are arranged within this carrier roadway, physically isolating the monitoring area from the mining production area and serving as a permanent operation and maintenance channel for the monitoring system.

[0044] S2. Monitoring Array Zoning Plan: This is a large monitoring area (with numerous working faces), so a segmented deployment scheme is adopted. A strip-shaped monitoring array is deployed every 2-3 consecutive working faces. Two monitoring arrays are deployed at the third and sixth working faces, each covering 3-4 working faces. Each array has a service life of 3 years. The monitoring ranges of adjacent arrays overlap by 100m to ensure no blind spots in the monitoring area. Simultaneously, directional optical fibers are deployed inside the working faces to form a three-dimensional monitoring network together with the DAS optical fibers in the directional boreholes.

[0045] S3. Dip-direction drilling: Based on the effective monitoring radius of the DAS fiber optic cable (300m for high-energy event monitoring), multiple dip-direction long boreholes are drilled at 300m intervals along the carrier roadway, with a single borehole depth of 1000m. The boreholes extend perpendicular to the working face advance direction into the target overburden strata. The monitoring ranges of each borehole overlap to eliminate blind spots in the panel monitoring. Multiple dip-direction boreholes are arranged to form a continuous strip-shaped monitoring array, jointly covering 8 consecutive working faces within the panel. The dip-direction boreholes are pre-constructed directional boreholes for roof disaster management, achieving multiple uses for a single borehole.

[0046] S4. DAS Fiber Deployment: DAS fibers are deployed into the long boreholes in each direction using a flexible, integrated casing-type push-down process. The DAS fibers are laid along the entire length of the borehole, with one end remaining within the solid coal carrier roadway and the other end extending to the roof area of ​​the target working face. A relaxation deformation allowance of 2% (20m) of the borehole length is reserved during DAS fiber deployment to buffer the tensile load on the fiber caused by surrounding rock deformation. When tensile loads are generated by surrounding rock deformation, the relaxed section expands first to absorb the tensile load, preventing the tensile load from being directly transferred to the fiber body inside the borehole, thus ensuring that the fiber is not broken during surrounding rock deformation.

[0047] S5. Establish a panel-scale strip-shaped three-dimensional monitoring network: After all DAS optical fibers are deployed in multiple directional boreholes, a panel-scale strip-shaped three-dimensional monitoring network is established based on these fibers. The strip-shaped monitoring network consists of multiple independent directional boreholes, with each monitoring channel operating independently. The monitoring ranges of adjacent boreholes overlap, eliminating blind spots in panel monitoring. This network, in conjunction with the fiber optic cables within the working face, forms a spatial three-dimensional monitoring system. This panel-scale strip-shaped monitoring network is linked and integrated with the fiber optic monitoring system deployed in the current production working face roadways. The regional directional borehole monitoring network is responsible for capturing large-scale events at the panel scale and dynamically assessing the boundaries of the goaf, while the fiber optic cables within the working face roadways are responsible for localized, refined monitoring of the mining space.

[0048] S6. Continuous Monitoring Throughout the Entire Lifecycle: DAS fiber optic acoustic signals are continuously acquired throughout the entire mining process across the eight working faces to achieve full-cycle monitoring, including pre-mining disturbance monitoring, in-mining overburden fracturing monitoring, and post-mining long-term overburden evolution monitoring, identifying high-energy micro-fracture events in the panel. When the micro-seismic energy per unit time exceeds a set threshold or a trend of high-energy event accumulation occurs, a rockburst hazard warning is issued.

[0049] S7. Assessment and Targeted Treatment Guidance for Overhanging Roofs at Goaf Boundaries: Based on the continuous collection of vibration signals from cross-working face monitoring arrays, the extent of overhanging roofs and high-stress concentration areas are assessed by analyzing the spatial concentration and energy release rate of micro-fracture events at the goaf boundary, thus outlining the failure morphology of the surrounding rock at the goaf edge. Based on the assessment results, targeted pressure relief and roof cutting treatment are implemented in the overhanging danger areas during the next working face goaf roadway excavation stage.

[0050] S8. Goaf Overburden Fault Tolerance Monitoring: When the optical cable of the dip-direction borehole near the goaf breaks during the working face mining, the DAS optical fiber segment remaining on the solid coal side continues to collect data, continuously receiving vibration signals generated by overburden collapse, interlayer slippage, and compaction within the goaf. This enables long-term observation of the evolution of the goaf overburden after the working face mining is completed. In this embodiment, two monitoring arrays provided continuous service for three years, covering the entire mining process of eight working faces, significantly improving the ability to capture large-scale energy events at the panel scale.

[0051] Example 6 The fiber optic monitoring method for cross-cycle multi-working-face based on adjacent-face solid coal roadway boreholes proposed in this embodiment, such as Figure 2 , 3 As shown, it includes the following steps: S1. Selection of Monitoring Carrier Roadway: A large mining panel has four consecutive working faces within its boundary 1: the first consecutive working face 2, the second consecutive working face 3, and the third consecutive working face 4. Several more working faces awaiting mining follow. The panel's strike length is 3000m, with each working face being 280m long. The solid coal transport roadway of the third consecutive working face 4 is selected as the solid coal carrier roadway 5. This solid coal carrier roadway 5 is a complete solid coal roadway, unaffected by the strong mining disturbances of the current working face. All monitoring and demodulation equipment and fiber optic cables are located within the solid coal carrier roadway 5, physically isolating the monitoring area from the mining production area, serving as a permanent maintenance channel for the monitoring system.

[0052] S2. Monitoring Array Zoning Planning: This area is a large area (with many working faces), and a segmented deployment scheme is adopted, with a strip-shaped monitoring array deployed every two consecutive working faces. Based on the working face layout, a monitoring array is deployed at the second and fourth consecutive working faces, each covering two working faces. Each array has a service life of 3 years, and the monitoring ranges of adjacent arrays overlap by 100m to ensure no blind spots in the monitoring of the area. Simultaneously, directional optical fibers are deployed inside the working faces, forming a three-dimensional monitoring network together with the DAS optical fibers deployed in the directional boreholes 6.

[0053] S3. Dip-direction drilling construction: Based on the effective monitoring radius of DAS optical fibers (350m for high-energy event monitoring), multiple long dip-direction boreholes (DSH) with DAS optical fibers are constructed at 350m intervals along the strike of the solid coal carrier roadway 5. These are called DSH boreholes 6 with DAS optical fibers, each with a depth of 900m, extending perpendicular to the working face advance direction into the target overburden strata. The monitoring ranges of each DSH borehole 6 with DAS optical fibers overlap, eliminating blind spots in the panel monitoring. Multiple DSH boreholes 6 with DAS optical fibers are arranged to form a continuous strip-shaped monitoring array, jointly covering multiple consecutive working faces within the panel. The DSH boreholes 6 with DAS optical fibers are pre-constructed directional boreholes for roof disaster management, achieving multiple uses from a single borehole.

[0054] S4. DAS Fiber Deployment: DAS fibers are deployed into each directional borehole 6, using a flexible tubing integrated pushing process. The DAS fibers are deployed along the entire length of the directional borehole 6, with one end remaining in the solid coal carrier roadway 5 and the other end extending to the roof area of ​​the target working face. A relaxation deformation allowance of 2% (18m) of the borehole length is reserved during DAS fiber deployment to buffer the tensile load on the fiber caused by surrounding rock deformation. When tensile loads are generated by surrounding rock deformation, the relaxation section expands first to absorb the tensile load, preventing the tensile load from being directly transferred to the fiber body inside the directional borehole 6, thus ensuring that the fiber is not broken during surrounding rock deformation.

[0055] S5. Establishing a Panel-Style Three-Dimensional Monitoring Network: After all DAS fibers are deployed in the directional boreholes 6, multiple directional boreholes are used to establish a panel-style three-dimensional monitoring network. The DAS fibers in the multiple independently deployed directional boreholes 6 form a strip-shaped monitoring network. Each monitoring channel is independent, and the monitoring ranges of adjacent directional boreholes 6 overlap, eliminating blind spots in panel monitoring. Combined with the fiber optic cables within the working face, a spatial three-dimensional monitoring system is formed. This panel-style monitoring network is linked and integrated with the fiber optic monitoring system deployed in the current production working face roadways. The regional directional borehole monitoring network is responsible for capturing large-scale events at the panel scale and dynamically assessing the boundaries of the goaf 7. The fiber optic cables within the working face roadways are responsible for localized, refined monitoring of the mining space. Data fusion between the two improves the accuracy of micro-fracture location.

[0056] S6. Continuous Monitoring Throughout the Entire Lifecycle: DAS fiber optic acoustic signals are continuously collected throughout the entire mining process across multiple working faces, including the first, second, and third consecutive working faces (face 2, face 3, and face 4). This enables full-cycle monitoring of pre-mining disturbances, in-mining overburden fracturing, and post-mining long-term evolution of the overburden in the goaf (face 7), identifying high-energy micro-fracture events in the mining area. When the micro-seismic energy per unit time exceeds a set threshold or a trend of high-energy event accumulation occurs, a rockburst hazard warning is issued.

[0057] S7. Assessment and Targeted Treatment Guidance for Overhanging Roofs at the Goaf Boundary: Based on the vibration signals continuously collected by the cross-working face monitoring array, the spatial concentration and energy release rate of micro-fracture events at the boundary of goaf 7 are used to assess the extent of overhanging roofs and high-stress concentration areas, identify overhanging roof zone 8 at the goaf boundary, and delineate the failure morphology of the surrounding rock at the edge of goaf 7. Based on the assessment results, in the next working face goaf roadway excavation stage, key pressure relief and roof cutting treatment will be implemented in the dangerous area of ​​overhanging roof zone 8 at the goaf boundary.

[0058] S8. Monitoring of Overburden Fault Tolerance in Goaf Area: When the directional drilling rig 6, where DAS optical fibers are deployed, breaks near the goaf area 7 during the mining of the first continuous working face 2, the DAS optical fiber segment remaining on the solid coal side continues to collect data, continuously receiving vibration signals generated by overburden collapse, interlayer slippage, and compaction within the goaf area 7. This enables long-term observation of the overburden evolution in the goaf area 7 after the mining of the first continuous working face 2. When the second continuous working face 3 and the third continuous working face 4 are subsequently mined, the same monitoring network continues to operate, successively undertaking the long-term monitoring tasks of the goaf area 7 after the mining of each working face. In this embodiment, the monitoring network has provided continuous service for more than 3 years, covering the entire mining process of multiple working faces within the panel boundary 1. The monitoring system is isolated from the mining area, significantly reducing operational safety risks. During the mining period, the cluster of microseismic events in the goaf boundary overhanging area 8 near the panel boundary 1 was successfully identified, providing accurate evidence for targeted treatment of the goaf roadway and realizing a closed-loop monitoring-treatment system.

Claims

1. A cross-cycle multi-working-face fiber optic monitoring method based on adjacent-face solid coal roadway boreholes, characterized in that, include: S1. Select the actual coal roadway of the working face to be mined as the monitoring carrier roadway; S2. Continuously lay out inclined directional boreholes along the carrier roadway; S3. Multiple long, inclined directional boreholes are drilled into the roof slab, with the boreholes extending perpendicular to the working face's advancing direction. S4. DAS optical fibers are laid into each inclined long borehole. S5. A three-dimensional monitoring network in the panel area is constructed by relying on multiple DAS optical fibers inclined into the borehole. S6. Acquire DAS fiber optic acoustic signals to achieve full-cycle monitoring of the working face; S7. Assess the extent of roof overhang at the boundary of the goaf to guide targeted remediation; S8. After the optical cable on the goaf side breaks, the optical fiber on the solid coal side is used to continuously monitor the overburden behind it.

2. The cross-cycle multi-working-face fiber optic monitoring method based on adjacent-face solid coal roadway boreholes according to claim 1, characterized in that, In S1, the carrier roadway is the main coal roadway of the next or the next working face to be mined, or the drainage roadway at the boundary of the panel; monitoring and demodulation equipment and fiber optic output terminals are installed in the carrier roadway to physically isolate the monitoring area from the mining and production area; the carrier roadway is a complete solid coal roadway or a permanent channel at the boundary of the panel, which is not subject to strong mining disturbances of the current working face for a long time, and serves as a permanent operation and maintenance channel for the monitoring system.

3. The cross-cycle multi-working-face fiber optic monitoring method based on adjacent-face solid coal roadway boreholes according to claim 2, characterized in that, In S2 and S3, the monitoring arrays are planned differently according to the size of the panel: for small panels, directional boreholes are continuously deployed along the carrier roadway to achieve full coverage; for large panels, a strip monitoring array is arranged every 2 to 3 consecutive working faces, with a service life of 2 to 3 years for each array, and the monitoring ranges of adjacent monitoring arrays are set to overlap to ensure that there are no blind spots in the panel monitoring; directional optical fibers are also deployed inside the working face to form a three-dimensional monitoring network together with the DAS optical fibers in the directional boreholes; the directional boreholes are monitoring boreholes constructed specifically for this purpose, or directional boreholes for roof disaster management constructed in advance.

4. The cross-cycle multi-working-face fiber optic monitoring method based on adjacent-face solid coal roadway drilling according to claim 3, characterized in that, In S2 and S3, multiple long dipping-oriented boreholes are drilled at intervals along the direction of the carrier roadway based on the effective monitoring radius of the DAS optical fiber. The effective monitoring radius is determined according to the vibration energy level of the monitoring target. It is 100m~150m for monitoring micro-fractures caused by conventional mining and 300m~500m for monitoring large energy events. The spacing between adjacent dipping-oriented boreholes is designed according to the effective monitoring radius of the DAS optical fiber, so that the monitoring range of each borehole overlaps with each other and eliminates blind spots in panel monitoring.

5. The cross-cycle multi-working-face fiber optic monitoring method based on adjacent-face solid coal roadway boreholes according to claim 1, characterized in that, In S4, the DAS optical fiber is inserted into the inclined directional borehole using a flexible tube integrated pushing process. The DAS optical fiber is arranged along the entire borehole, with one end remaining in the solid coal carrier roadway and the other end extending to the roof area of ​​the target working face. When the DAS optical fiber is laid out, a relaxation deformation margin is reserved to buffer the tensile load on the optical fiber caused by the deformation of the surrounding rock.

6. The cross-cycle multi-working-face fiber optic monitoring method based on adjacent-face solid coal roadway boreholes according to claim 5, characterized in that, In S4, the relaxation deformation allowance reserved for the DAS optical fiber is 1% to 2% of the borehole length, which is used to buffer the tensile load on the optical fiber caused by the deformation of the surrounding rock. When the deformation of the surrounding rock generates a tensile load, the relaxation section will expand first to absorb the tensile load, so as to avoid the tensile load being directly transmitted to the optical fiber body inside the borehole and ensure that the optical fiber is not broken during the deformation of the surrounding rock.

7. The cross-cycle multi-working-face fiber optic monitoring method based on adjacent-face solid coal roadway boreholes according to claim 1, characterized in that, In S5, multiple independent directional DAS optical fibers in the boreholes form a strip-shaped monitoring network. Each monitoring channel is independent of the others, and the monitoring ranges of adjacent boreholes overlap to eliminate blind spots in panel monitoring. Combined with the directional optical fibers in the working face, a spatial three-dimensional monitoring system is formed. The strip-shaped three-dimensional monitoring network is linked and integrated with the optical fiber monitoring system deployed in the current production working face roadway. The regional directional borehole monitoring network is responsible for capturing large-scale events at the panel scale and dynamically judging the boundary of the goaf. The optical fibers in the working face roadway are responsible for local fine-grained monitoring of the mining space. The data fusion of the two improves the accuracy of micro-fracture location.

8. The cross-cycle multi-working-face fiber optic monitoring method based on adjacent-face solid coal roadway boreholes according to claim 1, characterized in that, Specifically, S6 involves continuously acquiring DAS fiber optic acoustic signals throughout the entire mining process across multiple working faces, enabling full-cycle monitoring of pre-mining disturbance, mid-mining overburden fracturing, and post-mining goaf overburden long-term evolution. It also identifies high-energy micro-fracture events in the panel area and conducts early warning of rockburst hazards when the micro-seismic energy per unit time exceeds a set threshold or when a high-energy event accumulation trend occurs.

9. The cross-cycle multi-working-face fiber optic monitoring method based on adjacent-face solid coal roadway boreholes according to claim 1, characterized in that, Specifically, S7 involves: relying on the vibration signals continuously collected by the cross-working face monitoring array, judging the range of roof overhang and high stress concentration areas by the spatial concentration degree and energy release rate of micro-fracture events at the boundary of the goaf, outlining the failure morphology of the surrounding rock at the edge of the goaf, and implementing key pressure relief and roof cutting treatment in the goaf danger area during the next working face goaf roadway excavation stage based on the judgment results.

10. The cross-cycle multi-face fiber optic monitoring method based on adjacent solid coal roadway boreholes according to claim 1, characterized in that, Specifically, S8 means that when the optical cable of the directional borehole close to the goaf breaks due to the mining of the working face, the DAS optical fiber segment on the solid coal side maintains normal acquisition and continuously receives vibration signals generated by the collapse of the overlying rock, interlayer slippage, and compaction in the goaf, so as to realize long-term observation of the overlying rock evolution in the goaf after the mining of the working face is completed.

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