Deep well composite roof mining working face area treatment method

Abstract

The present application relates to the technical field of mining engineering, and discloses a deep well composite roof mining working face area treatment method, which comprises obtaining geological information for parameterized design, determining grouting process parameters and equipment materials; implementing a three-level collaborative treatment framework of grouting operation composed of curtain closure, regional coverage and local reinforcement, the curtain closure forms an isolation zone, the regional coverage adopts directional long boreholes and combines with a segmented retreat grouting process to uniformly cover the whole roof, and the local reinforcement adopts ordinary boreholes to supplement the reinforcement of fault fracture zones. Safety control is performed in parallel during the grouting operation, and multidimensional effect inspection is implemented after the operation. The segmented retreat grouting process uses a high-pressure recyclable packer to perform hole sealing, grouting, backwashing and retreat operations in sections. Through the three-level collaborative treatment framework, the present application realizes whole area treatment from the boundary to the area and from the general to the special, and ensures the uniformity and reliability of large-scale reinforcement through the segmented retreat grouting process.

Description

Technical Field

[0001] This invention relates to the field of mining engineering technology, specifically to a method for managing the area of ​​a deep-well composite roof mining face. Background Technology

[0002] As the depth of mineral resource extraction increases, deep-well composite roofs face multiple challenges, including high ground stress, fractured rock masses, and complex geological structures. Grouting reinforcement is a common technical means to ensure the safety of longwall mining faces; however, existing grouting methods still have shortcomings in dealing with such complex conditions.

[0003] Current methods often focus on reinforcing single targets, lacking a systematic, multi-layered governance system. This makes it easy for grout leakage to occur when dealing with large areas of the roof due to insufficient boundary control, and it is also difficult to take into account the targeted reinforcement of local weak areas such as fault fracture zones, resulting in an incomplete governance effect.

[0004] When reinforcing large areas, if long boreholes are used for one-time grouting, the frictional resistance of the grout will cause a significant decrease in the pressure at the bottom of the hole, resulting in uneven diffusion of the grout at the far end of the borehole and poor filling effect, making it difficult to ensure the quality homogeneity of the large-area reinforced body.

[0005] Furthermore, traditional grouting schemes rely heavily on engineering experience for design, lacking a parametric optimization process tailored to specific geological conditions, resulting in insufficient scientific rigor and specificity. Simultaneously, the evaluation methods for reinforcement effectiveness are relatively limited, lacking a closed-loop verification process that can objectively and quantitatively assess the treatment effect, making it difficult to guarantee the reliability of the entire project. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for managing the area of ​​deep well composite roof mining faces, which solves the problem of difficulty in ensuring the stability of composite roofs composed of weak rock strata and with complex structures during mining under deep high ground stress environments.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for managing the area of ​​a deep well composite roof mining face, comprising the following steps:

[0008] Geological information of the deep well composite roof mining face is obtained. Based on this geological information, numerical simulation analysis is used to determine grouting process parameters and expected reinforcement targets. Equipment and materials, including packers, are selected according to the grouting process parameters. Grouting operations are then carried out based on the grouting process parameters and the selected equipment and materials. These operations include: curtain grouting to form a closed isolation zone; regional grouting reinforcement to uniformly cover the roof of the deep well composite roof mining face; and localized enhanced grouting using ordinary boreholes to supplement the reinforcement of fault fracture zones and blind areas covered by directional boreholes. Throughout the entire grouting operation, full-process construction safety management is implemented to ensure the safe implementation of the grouting operation. After the grouting operation is completed, multi-dimensional effect verification is conducted, and the verification results are compared with the expected reinforcement targets to determine whether the treatment effect of the deep well composite roof mining face has achieved the expected reinforcement targets.

[0009] Preferably, the step of determining the grouting process parameters and expected reinforcement targets based on the geological information using numerical simulation analysis specifically includes: constructing a three-dimensional geomechanical model based on the geological information, and performing numerical simulation of the grout diffusion process in the three-dimensional geomechanical model, analyzing the grout diffusion law under different simulated grouting pressures and borehole spacings, thereby determining the preferred range of the grouting process parameters.

[0010] Preferably, the grouting reinforcement of the area is implemented by directional long drilling combined with segmented retreat grouting process. The directional long drilling adopts a two-stage opening structure, specifically including: drilling with a first hole diameter and inserting a protective casing in the first stage opening section, and continuing to drill to the final hole depth with a second hole diameter at the end of the protective casing, wherein the first hole diameter is larger than the second hole diameter.

[0011] Preferably, the segmented retractable grouting process specifically comprises: expanding the rubber sleeve of the packer by injecting water into it, thereby sealing the grouting hole segment; wherein the packer is a high-pressure recyclable packer; after sealing, preparing a reinforcing grout using the selected material, and injecting the reinforcing grout into the grouting hole segment until the grouting pressure stabilizes for a preset time, then stopping the injection of the reinforcing grout and backwashing the channel conveying the reinforcing grout; after backwashing, unsealing the high-pressure recyclable packer, retracting the high-pressure recyclable packer by a preset distance, and repeating the sealing, grout injection, and backwashing operations for a new grouting hole segment. The preset time is 3 minutes; the preset distance is 30 meters.

[0012] Preferably, the selected material comprises nano-modified single-component grouting material, wherein the maximum particle size of the nano-modified single-component grouting material is not greater than 7.53 μm; the reinforcing grout is prepared by mixing the nano-modified single-component grouting material with water at a water-cement ratio of 0.6:1 to 1:1 and stirring for 10 minutes; the rated pressure bearing capacity of the high-pressure recyclable packer is not less than 40 MPa.

[0013] Preferably, the curtain grouting sealing operation specifically includes: arranging curtain grouting holes in a five-hole pattern consisting of upper, middle, and lower rows of drill holes, and sealing the curtain grouting holes using the packer; injecting polyurethane-based chemical material as sealing grout into the sealed curtain grouting holes, and controlling the curtain grouting pressure within the range of 3MPa to 5MPa; stopping the injection of sealing grout when the curtain grouting pressure is stable and there is no leakage of sealing grout from the hole opening.

[0014] Preferably, the local reinforcement grouting specifically includes: after performing curtain pretreatment on the area to be reinforced to prevent leakage of the reinforcement grout during the main grouting operation, the same segmented retreat grouting process as the regional grouting reinforcement is used to perform main grouting on the ordinary borehole; the trajectory of the ordinary borehole is arranged perpendicular to or oblique to the fault plane.

[0015] Preferably, the multi-dimensional effect verification includes borehole cross-inspection, water pressure test, and borehole inspection; the determination of whether the treatment effect of the deep well composite roof mining face has achieved the expected reinforcement target specifically includes: obtaining the permeability of the reinforced rock mass through the water pressure test, and comparing the permeability with the permeability standard value set in the expected reinforcement target to quantitatively determine the sealing effect of the grouting operation on the rock mass fissures; observing the grout diffusion pattern and surrounding rock integrity on the borehole wall through borehole inspection to determine the degree of filling of the rock mass fissures by the reinforcement grout; and verifying the filling status of the reinforcement grout in the rock mass fissures through the borehole cross-inspection.

[0016] Preferably, the whole-process construction safety management includes using anti-detachment chains to fix the joint of the high-pressure hose, the anti-detachment chains being used to limit the hose from swinging when the joint accidentally comes detached.

[0017] This invention provides a method for managing the area of ​​a deep well composite roof mining face. It has the following beneficial effects:

[0018] 1. This invention constructs a three-level collaborative governance architecture consisting of curtain closure, regional coverage, and local reinforcement. First, curtain closure is used to pre-build a slurry isolation zone, which limits the scope of subsequent main grouting and suppresses slurry leakage. Then, regional coverage is used to achieve overall uniform reinforcement of the roof. Finally, local reinforcement is used to supplement weak links such as fault fracture zones, achieving comprehensive governance from the boundary to the area and from the general to the specific, with comprehensive and targeted governance effects.

[0019] 2. This invention combines directional long drilling technology with segmented retreat grouting process. It achieves comprehensive coverage of a large area of ​​the top plate from a limited drilling site by using directional long drilling. At the same time, by applying a set grouting pressure segment by segmented retreat grouting, it overcomes the problem of pressure at the bottom of the hole caused by friction resistance in traditional long-distance grouting, ensuring the uniformity of the reinforcement grout diffusion throughout the drilling range and improving the quality and effect of reinforcement of a large area.

[0020] 3. This invention establishes a closed-loop workflow from initial design to final evaluation by introducing parametric design and multi-dimensional effect verification. The remediation plan no longer relies on experience but is based on numerical simulation and parameter optimization using geological information, ensuring the scientific validity of the plan. After grouting, the reinforcement effect is cross-verified through various methods such as borehole cross-inspection, water pressure testing, and borehole inspection, making the remediation effect quantifiable and traceable. This places the entire remediation process within a controllable and verifiable framework, significantly improving the reliability of the project. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the overall workflow of a deep-well composite roof mining face area management method according to an embodiment of the present invention.

[0022] Figure 2 This is a borehole layout diagram for localized reinforcement treatment according to an embodiment of the present invention;

[0023] Figure 3 This is a flowchart of a segmented backward grouting process according to an embodiment of the present invention;

[0024] Figure 4 This is a numerical simulation cloud diagram of grouting pressure diffusion according to an embodiment of the present invention;

[0025] Figure 5 This is a cross-sectional schematic diagram of the curtain grouting hole arrangement according to an embodiment of the present invention;

[0026] Figure 6 This is a schematic diagram showing the arrangement of curtain grouting holes according to an embodiment of the present invention;

[0027] Figure 7 This is a schematic diagram of the planar layout of boreholes for regional treatment according to an embodiment of the present invention. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] See attached document Figure 1 To be continued Figure 7 This invention provides a method for managing the area of ​​a deep well composite roof mining face. The method establishes a three-tiered collaborative management framework consisting of curtain closure, regional coverage, and local reinforcement, used to handle composite roofs composed of weak rock strata and with well-developed geological structures in environments with a burial depth of 600 meters or more and under high ground stress.

[0030] The three-tiered collaborative governance architecture divides governance work into three functionally defined and interconnected levels. Curtain sealing, as a pretreatment and boundary control step, creates a closed isolation zone by constructing grouting holes in a specific area. Its function is to limit the effective range of subsequent main grouting operations and prevent grout leakage into non-target areas. Area covering, as the main reinforcement step, uses directional long-hole drilling technology to implement large-scale, systematic, and uniform grouting reinforcement of the entire longwall face roof. Local reinforcement, as a supplementary and key-point reinforcement step, uses ordinary drilling to conduct targeted supplementary grouting in key areas such as blind spots of directional hole coverage and fault fracture zones.

[0031] The three-tiered treatment system described above works in concert in terms of spatial arrangement and in a coordinated manner in terms of construction sequence, together forming a comprehensive treatment system for the composite roof from the boundary to the area, and from general to specific. Curtain closure creates effective grouting conditions for regional coverage and local reinforcement; regional coverage improves the overall stability of the roof; and local reinforcement solves the special stability problems in key geological anomaly areas.

[0032] Reference Appendix Figure 1 The overall workflow of this method includes the following steps:

[0033] S1: Preliminary Preparations. This preparation includes acquiring geological information of the deep-well composite roof recovery face, using numerical simulation analysis based on this information to determine grouting process parameters and expected reinforcement targets, and selecting equipment and materials, including packers, according to the grouting process parameters. Geological exploration is used to obtain geological information on the lithology, structure, and fracture development of the composite roof within the treatment area. Based on the acquired geological information, numerical simulation software is used to simulate the grout diffusion under different grouting pressures, hole spacing, and other key process parameters, determining an optimized range of grouting process parameters for on-site construction. According to design requirements, directional drilling rigs, high-pressure grouting pumps, high-pressure retrievable packers, and nano-modified grouting materials that meet specific technical specifications are selected.

[0034] S2: Implement three-level collaborative grouting. This step follows the logic of a three-level collaborative governance architecture and can be carried out sequentially or in parallel. Specifically, it includes: implementing curtain grouting sealing operations in directional drilling sites, ordinary drilling sites, and surrounding areas to form an isolation zone to prevent leakage during subsequent main grouting.

[0035] By employing directional long borehole drilling combined with segmented retreat grouting technology, regional grouting reinforcement was implemented to achieve uniform coverage of the entire roof of the longwall mining face.

[0036] Using conventional drilling, localized reinforced grouting is implemented in key areas such as fault fracture zones and blind spots covered by directional holes discovered during geological exploration and directional hole construction to supplement and reinforce critical weak points.

[0037] S3: Implement full-process construction safety management. Full-process construction safety management is carried out in parallel throughout the execution of step S2, and its content covers personnel and equipment management, on-site environmental monitoring, and real-time monitoring and recording of grouting process parameters.

[0038] S4: Implement multi-dimensional effect verification. After step S2, implement a multi-dimensional verification system consisting of borehole cross-inspection, water pressure testing, and borehole inspection to comprehensively evaluate the treatment effect. Borehole cross-inspection is used to verify the grout filling status through adjacent boreholes; water pressure testing is used to determine the compaction degree of the reinforced body by quantifying changes in rock permeability; borehole inspection is used to visually observe the grout diffusion pattern and surrounding rock integrity on the reinforced borehole wall. Through this verification system, the treatment effect is comprehensively evaluated.

[0039] Reference Appendix Figure 1 When implementing the overall workflow of the deep well composite roof mining face area treatment method, the first step is S1, which is the preliminary preparation. This step provides basic data, optimized parameters, and material support for subsequent grouting reinforcement operations. Its specific contents include geological information acquisition, parametric design, and equipment and material selection.

[0040] Geological information acquisition aims to accurately understand the geological conditions of the treatment area. This process is achieved through the integrated use of geological drilling and 3D seismic exploration techniques. These exploration methods clarify the lithological composition of the composite roof, the interlayer spacing between strata (e.g., varying from 0 to 5.9 meters), detailed parameters of fault structures, and the development characteristics of rock mass fractures. Fault parameters include the fault's strike, dip, dip angle, and displacement. This geological information collectively constitutes the basic geological model for subsequent parametric design.

[0041] Parametric design is a crucial step after obtaining detailed geological information to ensure the scientific validity and relevance of the grouting scheme. Based on geological information (such as lithology and structural data), parametric design constructs a three-dimensional geomechanical model and numerically simulates the grout diffusion process within this model. It analyzes the grout diffusion characteristics under different simulated grouting pressures and borehole spacings to determine the optimal range of grouting process parameters. Key variables examined in the simulation include grouting pressure (ranged from 5 MPa to 20 MPa), borehole spacing (ranged from 30 meters to 60 meters), and the rheological properties of different types of grouting materials. By analyzing and comparing the grout diffusion characteristics under different parameters, such as... Figure 4 The cloud map showing the grout diffusion range after 30 minutes under 15MPa pressure was shown, and a set of optimized grouting process parameters that could achieve the expected reinforcement range and effect were finally determined.

[0042] Equipment and material selection involves choosing equipment and materials that meet specific technical specifications based on the results of parametric design and on-site construction requirements. This process includes:

[0043] When selecting a directional drilling rig, its maximum drilling depth must be no less than 400 meters to meet the drilling needs for large-scale area coverage and reinforcement; at the same time, a conventional drilling rig should be selected for subsequent local reinforcement and curtain grouting hole construction.

[0044] Choose a high-pressure grouting pump with a rated working pressure of not less than 15MPa to ensure that the grout can be effectively injected into the fine cracks of the composite roof.

[0045] Choose a high-pressure recyclable packer with a rated pressure capacity of no less than 40 MPa, a length of 1.5 meters, and a diameter of 75 mm to ensure sealing reliability and reusability during segmented grouting.

[0046] When selecting grouting materials, nano-modified single-component grouting material is preferred as the main material. Its key performance parameter is a maximum particle size (D95) not exceeding 7.53 μm to ensure the grout's penetration into fine cracks. In special geological conditions involving large-scale grout leakage, nano-modified two-component grouting material is used as a sealing material. Regarding the mixing ratio of nano-modified single-component grouting material, its water-cement ratio... The value range is from 0.6:1 to 1:1. Water-cement ratio. Calculated using the following formula:

[0047] ;

[0048] in: The water-cement ratio represents the ratio of the mass of water in the grout to the mass of the grout (dry powder), and is a dimensionless parameter. Indicates the mass of water; This indicates the quality of the grouting material (dry powder).

[0049] Reference Appendix Figure 1 After completing the preliminary preparations in step S1, the process proceeds to step S2, which involves implementing three-level coordinated grouting. The first step in step S2, or the step carried out in parallel with other grouting steps, is to perform curtain grouting sealing operations in the directional drilling site, the conventional drilling site, and the surrounding area (e.g., within a 20-meter radius). The goal of curtain grouting sealing operations is to construct a closed grout isolation zone to pre-seal shallow fissures and fracture zones at the boundary of the target area, thereby creating a closed grouting environment for subsequent regional grouting reinforcement and localized strengthening grouting, effectively preventing grout leakage, and ensuring the pressure and diffusion range of the main grouting.

[0050] See attached document Figure 5 and attached Figure 6 The curtain grouting holes were constructed using a conventional drilling rig. The parameters for the curtain grouting holes were set as follows: hole diameter 42 mm, hole depth 6 m. They were arranged in a five-hole pattern, consisting of three rows of holes (upper, middle, and lower). Specific parameters are as follows:

[0051] Upper row of holes: The opening position is 0.5 meters to 1 meter away from the top of the roadway, and the construction is carried out at an upward angle of 75 degrees;

[0052] Middle row hole: The hole is located 1.75 meters from the bottom of the tunnel and is constructed perpendicular to the tunnel wall;

[0053] Lower row of holes: The opening position is 1 meter away from the tunnel floor, and the construction is carried out perpendicular to the tunnel side;

[0054] On the same horizontal plane, the spacing between adjacent boreholes is set at 5 meters.

[0055] After the curtain grouting holes are constructed, sealing and grouting operations are carried out. FKSJ-38 / 6 type packers are used for sealing, and the packers are placed 3 meters from the hole opening. Polyurethane-based chemical materials are injected into the sealed curtain grouting holes as sealing grout, and the curtain grouting pressure is controlled within the range of 3MPa to 5MPa.

[0056] The termination criteria for the grouting process are as follows: when the curtain grouting pressure is stable and there is no leakage of sealing grout from the orifice, the injection of sealing grout should be stopped, and the pressure displayed by the grouting pump should be maintained stably for more than 3 minutes. Once this criterion is met, the curtain grouting of the curtain grouting holes is considered complete.

[0057] Reference Appendix Figure 1 In the three-level coordinated grouting in step S2, the secondary treatment step is regional directional borehole full-area grouting reinforcement. The treatment principle of this step is to construct long-length, controllable-trajectory boreholes using directional drilling technology. Starting from a limited drilling site, the borehole trajectory unfolds in a fan shape or parallel pattern within the target layer 2 to 3 meters above the composite roof, thereby achieving comprehensive coverage of a vast roof area. Combined with the use of segmented retreat grouting technology, the set grouting pressure can be applied segment by segment, overcoming the problem of bottom hole pressure attenuation caused by friction resistance in traditional full-length single grouting processes, and ensuring the uniformity of grout diffusion throughout the entire long borehole.

[0058] The goal of this treatment is to inject nano-modified grouting material with low particle size (D95≤7.53μm) into the primary and secondary fracture networks of the roof rock mass through segmented and uniform drilling into long, directional boreholes covering the entire longwall face. Under pressure, the grout diffuses, cements, and solidifies, filling fractures and binding broken rock fragments to form a continuous, homogeneous reinforced body. This reinforced body transforms the originally discrete and weak rock strata into a unified structure, improving the mechanical properties of the composite roof, enhancing its integrity and load-bearing capacity, and ultimately achieving systematic reinforcement of the entire longwall face roof.

[0059] See attached document Figure 7 When implementing directional drilling for full-area reinforcement, the first step is to design the drilling sites and borehole structures. The principle for drilling site layout is to select locations that can effectively control the roof of the entire working face and offer convenient construction conditions. Specifically, suitable locations are selected within the transport roadway and track roadway as directional drilling sites. From each drilling site, one main borehole and several branch boreholes derived from it are constructed, as shown in the attached diagram. Figure 7 The blue lines in the diagram illustrate the planar trajectories of these boreholes. The borehole trajectories are designed to ensure that the final boreholes uniformly cover the entire working face top plate. To achieve this, the horizontal spacing between the final borehole positions of adjacent boreholes is controlled between 60 and 90 meters. Simultaneously, the final boreholes of all boreholes are positioned vertically within 2 to 3 meters above the composite top plate.

[0060] The borehole structure is designed to ensure borehole wall stability during long-distance drilling and the smooth implementation of subsequent segmented grouting operations. The directional long borehole employs a two-stage opening structure. Specific structural parameters are as follows:

[0061] First-stage drilling: The initial section of the borehole, drilled using the first borehole diameter, with a casing installed within this first-stage drilling section. Specifically, a 190 mm borehole diameter is used. Within the first-stage drilling section, a 146 mm diameter casing is installed, with a casing length of no less than 30 meters. The purpose of the casing is to address the poor stability of the surrounding rock near the borehole opening in the high-stress environment of deep wells. Through isolation and support, it seals the fractured rock strata in this section, preventing collapse or grout leakage during subsequent drilling and high-pressure grouting, and providing a reliable sealing foundation for segmented grouting operations.

[0062] Second-stage drilling: Drilling continues forward from the end of the casing, using a second borehole diameter to reach the final drilling depth. Specifically, a 120 mm borehole diameter is used until the designed final drilling depth is reached. The second-stage drilling is the main section for implementing segmented grouting reinforcement.

[0063] Reference Appendix Figure 1 and attached Figure 3 After completing the drilling site layout and borehole structure design, a segmented retreat grouting process was used to reinforce the second-stage opening section of the directional borehole. The segmented retreat grouting process starts from the bottom of the borehole and grouts segment by segment towards the borehole opening in fixed lengths. The specific operation process consists of a series of cyclical operations such as sealing the borehole, grout preparation, grouting, backwashing, and retreat.

[0064] Sealing: A high-pressure recyclable packer with a pressure-bearing capacity of not less than 40 MPa is pushed to the bottom of the section of the borehole to be grouted via the drill pipe. Low-pressure water is injected into the packer through its independent water injection channel, raising the pressure inside the packer to 5 MPa. Under this pressure, the rubber sleeve of the packer expands and fits tightly against the borehole wall, thus forming a high-pressure seal between the section to be grouted and the rest of the borehole.

[0065] Grout Preparation: After sealing, a reinforcing grout is prepared using the selected material. Water is mixed with the nano-modified single-component grout at a water-cement ratio ranging from 0.6:1 to 1:1. The mixture is stirred continuously for 10 minutes using a mixer to ensure that the grout is uniform, free of lumps, and ready for pumping.

[0066] Grouting: The prepared grout is pumped into the grouting section sealed by the packer using a high-pressure grouting pump through an independent grouting channel on the packer. The grouting pressure is controlled at 15 MPa. During the grouting process, grout is continuously injected into the rock mass until the grouting pressure is reached and maintained stably for 3 minutes. At this point, it can be determined that the cracks in the grouting section have been fully filled, and the grouting operation in that section is then stopped.

[0067] Backwashing and Retreat: After grouting is stopped, the channels for delivering the reinforcing grout are backwashed. Specifically, the pipeline is immediately cleaned to prevent the grout from solidifying inside the drill pipe. The water injection channel is connected to the grouting channel by operating the cleaning valve on the packer. A large flow of clean water is introduced through the water injection channel to backwash the grouting channel and any residual grout inside the drill pipe. After cleaning, the packer is released, causing its rubber sleeve to contract and detach from the borehole wall. Subsequently, the entire drill string (including the packer) is retreated towards the borehole opening by a predetermined distance. This predetermined distance is 30 meters.

[0068] Cyclic operation: After the packer retracts into position, the above-mentioned sealing, grouting, and backwashing operations are repeated for the new section. This cyclic operation process is repeated continuously until the packer retracts to a distance from the orifice casing, the final section of grouting is completed, and the packer is withdrawn.

[0069] In the process of implementing segmented retreat grouting technology, corresponding coping strategies are pre-set to deal with special working conditions caused by the complexity of geological conditions, so as to ensure the smooth completion of the regional directional hole full-area coverage reinforcement.

[0070] When encountering sections of particularly fractured surrounding rock and poor borehole wall stability during drilling, resulting in poor borehole quality and difficulty in maintaining borehole integrity for standard segmented retreat grouting, the grouting process will be adjusted to forward-moving sweep grouting. The specific operational procedure for this alternative process is as follows: First, drill forward one segment's length, for example, 30 meters; after completing this segment, immediately pause drilling and perform a sweep grouting on the newly formed borehole segment. After the injected grout solidifies and pre-stabilizes the borehole wall of this segment, continue drilling forward to the next segment. This cyclical operation of drilling and sweeping / grouting one segment progresses segment by segment until the borehole reaches the designed final depth. This strategy ensures the feasibility of long-distance drilling in unstable strata by immediately reinforcing new borehole segments.

[0071] Reference Appendix Figure 1 In the three-level coordinated grouting in step S2, the third-level treatment step is the enhanced grouting of local ordinary boreholes. The third-level treatment step is a supplement and reinforcement to the full coverage reinforcement of regional directional boreholes, constituting the key point reinforcement layer in the treatment system.

[0072] The principle behind the tertiary remediation stage is that while the regional coverage in the secondary stage achieves overall reinforcement of the roof, local weak points still exist. These include coverage blind spots caused by large spacing between directional borehole tracks, and key areas such as fault fracture zones identified in previous geological exploration. Therefore, the tertiary stage utilizes the flexibility and precise layout of conventional borehole construction to target these identified weak points or geological anomalies.

[0073] The goal of this treatment is to supplement the blind spots covered by directional boreholes by drilling a series of conventional boreholes within a specific area, and to reinforce key areas such as fault fracture zones with additional grouting. This ensures that the reinforcement effect throughout the entire treatment area is not only uniform but also provides additional strengthening to critical weak points. Ultimately, through this supplementary and reinforcing approach, structural weaknesses in the roof reinforcement are eliminated, achieving comprehensive reinforcement without blind spots from the boundary to the region and from general to specific areas, ensuring the long-term stability of the composite roof during mining.

[0074] In the three-level treatment process of step S2, the specific implementation of precise reinforcement of local ordinary holes first requires detailed drilling layout and parameter design.

[0075] See attached document Figure 2 , attached Figure 2 The magenta lines in the diagram illustrate the planar trajectory of conventional boreholes used for localized reinforcement. The borehole layout is designed to maximize the reinforcement effect on key areas such as fault fracture zones. Specifically, the boreholes are arranged in parallel, with a spacing of 10 meters between adjacent boreholes. To effectively reinforce fault fracture zones, the borehole trajectories are designed to be perpendicular or oblique to the fault plane, ensuring maximum exposure and penetration of fractures within the fault zone. All boreholes are uniformly positioned 2 meters from the roadway roof. To ensure complete penetration and sealing of the entire fault-affected area, the borehole termination point is required to penetrate 3 to 5 meters into the target fault plane. The specific geometric parameters for the conventional boreholes used for localized reinforcement are set as follows: borehole diameter 94 mm, borehole depth 110 m.

[0076] In the third-level treatment stage of step S2, after the conventional drilling for the local weak areas is completed according to the design, the grouting reinforcement operation immediately begins. This operation includes two steps: curtain pretreatment and main grouting.

[0077] First, to prevent grout leakage during the main grouting process, curtain pretreatment is required. Specifically, before the main grouting, curtain grouting holes are pre-constructed at the coal seam location in the area to be reinforced. The construction parameters for these curtain grouting holes, including hole diameter, hole depth, drilling arrangement, sealing method, grouting material, and grouting pressure, are all consistent with the parameters used in the primary treatment (i.e., curtain grouting pre-sealing operation).

[0078] After completing the curtain pretreatment, the main grouting was carried out on the locally reinforced ordinary boreholes. The main grouting process adopted segmented retreat grouting, and its specific operation process (including borehole sealing, grout preparation, grouting, retreat, etc.) was consistent with the process flow in the secondary treatment (regional directional borehole full-area grouting reinforcement). The grouting material used was the same nano-modified single-liquid grouting material as the secondary treatment.

[0079] The pressure during grouting is controlled within the range of 10MPa to 15MPa. The termination criteria for grouting operations are set as two conditions, and grouting can be stopped if either condition is met: Pressure stability standard: After the grouting pressure reaches the set value, it can be maintained stably for more than 3 minutes; Grout intake standard: The flow rate display of the grouting pump shows that there is no obvious grout intake in the rock mass.

[0080] Reference Appendix Figure 1 After completing all the three-level coordinated grouting reinforcement work, the process moves to step S3, which is the whole-process construction safety management, to ensure the safety of the entire treatment process. This step begins with the safety management of personnel and equipment.

[0081] Firstly, regarding personnel management, all operators of high-pressure grouting pumps must undergo specialized training and pass an examination before being allowed to work. The training content includes not only the basic operating procedures of the equipment but also an understanding of grouting process parameters and the ability to identify and handle emergencies such as abnormal pressure and flow rates.

[0082] Secondly, regarding equipment safety management, a strict inspection procedure must be performed before each pump start-up operation to ensure the equipment is in a safe and reliable working condition. This inspection procedure includes the following: Mechanical condition inspection: Check the oil level of the grouting pump set to ensure the lubrication system is normal and prevent equipment failure or damage due to insufficient lubrication; Piping system inspection: Check the connection status of all high-pressure pipelines, confirm that all joints are tight and there is no risk of leakage, and check the high-pressure hoses themselves for defects such as bulges or damage; Electrical system inspection: Check the integrity of the cable lines supplying power to the pump set, ensuring that the cable insulation layer is undamaged and the grounding protection is reliable to prevent leakage accidents.

[0083] Specifically, the entire construction safety management process includes securing the joints of high-pressure hoses with anti-detachment chains. These chains limit the hose's swinging motion in the event of an accidental detachment. This measure effectively limits the violent swinging of the hose when the joint accidentally detaches due to high-pressure impact or vibration, thereby preventing injury to on-site personnel and equipment.

[0084] In implementing step S3, the entire process of construction safety management includes not only direct management of personnel and equipment, but also monitoring of the work site environment to address potential environmental risks.

[0085] First, to ensure personnel safety during high-pressure grouting operations, strict personnel access control and safety precautions must be implemented. Specifically, before grouting operations begin, physical barriers or clearly visible safety warning signs must be erected around the work area to create a restricted access safety zone. Simultaneously, a strict evacuation and interception system must be enforced. Evacuation refers to removing all non-essential personnel from the restricted area to a safe location; interception means prohibiting any unauthorized personnel from entering the restricted area during grouting operations.

[0086] Secondly, throughout the grouting operation, continuous monitoring of key hazardous gases in the surrounding environment is essential. The key gases monitored include methane and hydrogen sulfide. This monitoring is conducted using portable or stationary gas detectors deployed on-site. If monitoring data shows that the concentration of any gas exceeds the preset safety threshold, an abnormal situation is considered. In this case, an emergency response must be initiated immediately: on-site operators must immediately stop the grouting pump and handle the situation according to procedures, investigate the cause of the abnormal gas concentration, and only resume operations after the risk has been eliminated.

[0087] In the full-process construction safety management of step S3, in addition to monitoring the external environment, it is also necessary to dynamically monitor the key process parameters of the grouting process to ensure that the construction process meets the design requirements and is in a safe state.

[0088] Throughout the grouting process, operators must monitor the grouting pump's operating status in real time. Key parameters to monitor include grouting pressure and grout flow rate. Operators adjust the grouting pump's setting in real time by observing the pressure gauge and flow meter readings to ensure that the grouting pressure and flow rate remain within the design requirements, thus avoiding safety risks or affecting the reinforcement effect due to overpressure or underpressure.

[0089] Simultaneously, it is essential to meticulously record key data during the grouting process. These parameters include, but are not limited to: grouting start and end times, real-time grouting pressure changes, real-time flow rate changes, and the total cumulative amount of grout injected. These records provide fundamental data for assessing grouting effectiveness and analyzing and handling unforeseen problems.

[0090] For grouting operations that need to be carried out continuously across shifts, a strict on-site shift handover system must be implemented. The outgoing shift personnel must clearly hand over to the incoming shift personnel the recorded grouting parameters, the current progress of the operation, the equipment operating status, and any abnormalities observed during the shift. The incoming shift personnel can only take over the operation after confirming that all information is correct, to ensure the accuracy of information transmission and the continuity and safety of the operation.

[0091] Reference Appendix Figure 1 After completing the three-level coordinated grouting reinforcement (step S2) and ensuring construction safety throughout the process (step S3), the process proceeds to step S4, which involves multi-dimensional evaluation of the treatment effect. This step aims to objectively and comprehensively evaluate the final quality of the grouting reinforcement through cross-verification using multiple methods, ensuring that the treatment effect meets design expectations. This evaluation system includes three methods: borehole cross-inspection, water pressure testing, and borehole inspection.

[0092] Cross-drilling inspection is a method that uses subsequently drilled boreholes to verify the reinforcement effect of previously grouted areas. In practice, the construction sequence of directional boreholes or local reinforcement boreholes is adjusted so that later boreholes can penetrate or be adjacent to grouted rock masses. During the drilling process of these later boreholes, the grouting effect can be indirectly judged by analyzing core sampling or changes in drilling parameters. For example, directly observing in the core sample that existing fractures have been filled with solidified grout, and that the grout is well-bonded with the surrounding rock, provides direct evidence of successful reinforcement. Simultaneously, analyzing data during drilling, such as drilling speed, drilling pressure, and circulating fluid consumption, can also reflect the integrity and stability of the rock mass. This method allows for effective verification of grout filling in fractured zones.

[0093] The water pressure test is a standard method for quantitatively evaluating the permeability of rock masses. After the grouting reinforcement work is completed, a test borehole is drilled specifically within the reinforced area. A packer is used to seal a specific test section within the test borehole, and then clean water is injected into this sealed section using a high-pressure pump. The injection volume is recorded under stable pressure. The permeability of the reinforced rock mass can be calculated through the water pressure test. By comparing this permeability with the standard value required by the design, it is possible to quantitatively determine whether the grouting reinforcement has effectively reduced the permeability of the rock mass, thereby evaluating whether the sealing effect of the grout on rock mass fissures meets the design requirements.

[0094] Borehole inspection is an inspection method that provides direct visual evidence. This method utilizes a mining electronic inspection device, a specialized piece of equipment equipped with a camera probe and a lighting source, which is inserted deep into the inspection borehole. The probe travels along the borehole wall, transmitting real-time high-definition images of the borehole interior to a surface display device. By analyzing the inspection images, technicians can directly observe the following: Grout diffusion range: determining the actual distribution of the grout within the rock fracture network. Fracture filling status: clearly showing the degree of grout filling of fractures of varying sizes, indicating whether it is fully filled, partially filled, or unfilled. Surrounding rock integrity: assessing the overall stability of the rock mass surrounding the borehole after grouting and the degree of integration after cementation.

[0095] In summary, the indirect physical evidence provided by borehole cross-inspection, the quantitative hydraulic parameters provided by water pressure testing, and the direct visual images provided by borehole inspection together constitute a multi-dimensional closed-loop effect verification system, ensuring a comprehensive and reliable assessment of the grouting reinforcement effect.

Claims

1. A method for managing the area of ​​a deep-well composite roof mining face, characterized in that, Includes the following steps: Geological information of the deep well composite roof mining face is obtained, and based on the geological information, numerical simulation analysis is used to determine the grouting process parameters and expected reinforcement targets. Equipment and materials, including packers, are selected according to the grouting process parameters. Based on the grouting process parameters and the selected equipment and materials, grouting operations are carried out. These operations include: curtain grouting to form a closed isolation zone; regional grouting reinforcement to uniformly cover the roof of the deep well composite roof recovery face; and localized enhanced grouting using conventional boreholes to supplement the fault fracture zone and the blind area covered by directional boreholes. The regional grouting reinforcement is implemented using long directional boreholes combined with a segmented retreat grouting process. The long directional boreholes employ a two-stage opening structure, specifically including: drilling with a first borehole diameter and inserting a casing in the first-stage opening section; continuing drilling with a second borehole diameter at the end of the casing to the final depth, wherein the first borehole diameter is larger than the required diameter. Regarding the second aperture, the segmented retraction grouting process specifically involves: injecting water into the packer to drive the rubber sleeve of the packer to expand and seal the grouting hole segment, wherein the packer is a high-pressure recyclable packer; after sealing, a reinforcing grout is prepared using the selected material and injected into the grouting hole segment until the grouting pressure stabilizes for a preset time, at which point the injection of the reinforcing grout is stopped, and the channel for conveying the reinforcing grout is backwashed; after backwashing, the high-pressure recyclable packer is unsealed, and the high-pressure recyclable packer is retracted by a preset distance, and the sealing, injection of the reinforcing grout, and backwashing operations are repeated for the new grouting hole segment; Throughout the entire grouting operation, full-process construction safety management is implemented in parallel to ensure the safe implementation of the grouting operation; After the grouting operation is completed, a multi-dimensional effect test is carried out, and the test results are compared with the expected reinforcement target to determine whether the treatment effect of the deep well composite roof mining face has achieved the expected reinforcement target.

2. The method for managing the area of ​​a deep-well composite roof mining face according to claim 1, characterized in that, The steps for determining grouting process parameters and expected reinforcement targets based on the geological information using numerical simulation analysis specifically include: A three-dimensional geomechanical model is constructed based on the geological information, and the grout diffusion process is numerically simulated in the three-dimensional geomechanical model. The grout diffusion law under different simulated grouting pressures and borehole spacings is analyzed, thereby determining the range of the grouting process parameters.

3. The method for managing the area of ​​a deep-well composite roof mining face according to claim 1, characterized in that, The preset duration is 3 minutes; the preset interval is 30 meters.

4. The method for managing the area of ​​a deep-well composite roof mining face according to claim 1, characterized in that, The selected material includes nano-modified single-component grouting material, wherein the maximum particle size of the nano-modified single-component grouting material is no greater than 7.53 μm; The reinforcing grout is prepared by mixing the nano-modified single-component grouting material with water at a water-cement ratio of 0.6:1 to 1:1 and stirring for 10 minutes. The rated pressure bearing capacity of the high-pressure recyclable packer is not less than 40 MPa.

5. The method for managing the area of ​​a deep-well composite roof mining face according to claim 1, characterized in that, The localized reinforcement grouting specifically includes: After pre-treating the area to be reinforced with a curtain to prevent leakage of the reinforcing grout during the main grouting operation, the same segmented retreating grouting process as the grouting reinforcement of the area is used to perform main grouting on the ordinary borehole. The trajectory of the conventional borehole is arranged perpendicularly or obliquely to the fault plane.

6. The method for managing the area of ​​a deep-well composite roof mining face according to claim 1, characterized in that, The curtain grouting sealing operation specifically includes: The curtain grouting holes are arranged in a five-hole pattern consisting of three rows of holes (top, middle, and bottom), and the packer is used to seal the curtain grouting holes. Polyurethane-based chemical materials are injected into the grouting holes of the curtain after sealing, and the curtain grouting pressure is controlled within the range of 3MPa to 5MPa. When the curtain grouting pressure is stable and there is no leakage of the sealing grout from the orifice, the injection of the sealing grout is stopped.

7. The method for managing the area of ​​a deep-well composite roof mining face according to claim 1, characterized in that, The entire construction safety management process includes using anti-detachment chains to fix the joints of high-pressure hoses. The anti-detachment chains are used to limit the hose from swinging when the joints accidentally come detached.

8. The method for managing the area of ​​a deep-well composite roof mining face according to claim 1, characterized in that, The multi-dimensional effect inspection includes borehole cross-inspection, water pressure test and borehole inspection; The determination of whether the treatment effect of the deep well composite roof mining face has achieved the expected reinforcement target specifically includes: The permeability of the reinforced rock mass is obtained through the water pressure test, and the permeability is compared with the permeability standard value set in the expected reinforcement target to quantitatively determine the sealing effect of the grouting operation on the rock mass fissures. By observing the grout diffusion pattern and the integrity of the surrounding rock through borehole inspection, the degree to which the reinforcing grout fills the rock mass fissures can be determined. The filling status of the reinforcing grout in the rock mass fractures was verified by cross-inspection of the boreholes.

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