Goaf-overlying strata separation three-dimensional filling earth surface subsidence reduction mining method

Abstract

The invention discloses a goaf-overlying strata separation three-dimensional filling earth surface subsidence reduction mining method, which belongs to the field of rock stratum mining and comprises mining area planning and working face design, ground filling system construction, filling parameter design, goaf filling operation, overlying strata separation grouting operation and circulation operation. According to the goaf-overlying strata separation layer three-dimensional filling earth surface subsidence reduction mining method, the subsidence control capacity is remarkably enhanced, a rigid supporting layer is formed through goaf filling, the pressure of a top plate is directly absorbed, a hydraulic barrier is created below a key layer through overlying strata separation layer grouting, separation layer extension is restrained, and a lower supporting-upper plugging three-dimensional control structure is constructed through cooperation of the rigid supporting layer and the overlying strata separation layer grouting; ground surface settlement is greatly reduced, the recovery rate of coal resources is improved, resource waste is reduced, coal gangue serves as a main filling material, goaf filling and bed separation grouting are implemented in stages, first mining face goaf filling and two-side working face bed separation grouting are carried out, and interference of filling operation on mining circulation is reduced.

Description

Technical Field

[0001] This application relates to the field of rock strata mining, and in particular to a method for reducing surface subsidence through three-dimensional filling of goaf-overburden separation in mining operations. Background Technology

[0002] In the process of mining underground resources such as coal mines, in order to effectively address the surface subsidence caused by mining and the resulting ecological and environmental damage, goaf filling mining and delamination grouting mining are considered key solutions. Goaf filling mining has good filling effect, but the process system is complex and has many procedures, which inevitably interferes with the normal production cycle of the mine and reduces the efficiency of mining operations. Overburden delamination grouting filling mining technology has the advantages of relatively simple process and relatively low investment and operating costs. However, due to the limitations of the technology such as the spatial positioning accuracy of the target delamination, the controllability of grout diffusion, and the stability of delamination development, the rock layer control effect of this method is often difficult to achieve the ideal state, and the control effect on surface subsidence is relatively limited, making it difficult to ensure that the expected subsidence control target is achieved.

[0003] Existing technologies such as goaf backfilling and overburden separation grouting each have irreconcilable contradictions and limitations in key performance indicators such as cost-effectiveness, process efficiency, and subsidence control. The advantages of these two technologies cannot be effectively complemented, making it difficult to integrate them into a comprehensive mining process system that combines high efficiency, low cost, and highly reliable subsidence control. This technological bottleneck severely restricts the large-scale promotion and engineering application of backfilling technology in controlling surface subsidence. Summary of the Invention

[0004] To address the problems mentioned in the background art, this application provides a method for reducing surface subsidence through three-dimensional filling of goaf-overburden separation in mining operations.

[0005] The technical solution provided in this application for a three-dimensional filling method for reducing surface subsidence in goaf-overburden delamination mining is as follows:

[0006] A method for reducing surface settlement in goaf-overburden separation three-dimensional filling mining, comprising the following steps:

[0007] S1. Mining area planning and working face design:

[0008] S101. Design a longwall mining system and divide the mining area into several working faces;

[0009] S102. The first mining face in the middle of the mining area is set as the goaf filling working face, and the two working faces are successively implemented with delamination grouting and goaf filling.

[0010] S2. Construction of the ground filling system:

[0011] S201. A ground filling station shall be built in the middle of the main roadway of the mining area for slurry preparation and pressurized transportation;

[0012] S202, vertical grouting drilling is carried out from the ground to the main roadway of the mining area, and horizontal conveying pipelines are laid in the main roadway of the mining area to each working face;

[0013] S3. Filling parameter design:

[0014] S301. Based on geological and mining conditions and surface subsidence control targets, the filling rate and filling intensity are determined through numerical simulation.

[0015] S302. Prepare filling grouts with different proportions for use in goaf filling and delamination grouting, respectively.

[0016] S4. Goaf filling operation:

[0017] S401. Slurry is transported behind the first mining face, and the filling step distance is designed to meet the following requirements: ,

[0018] Where k is the safety factor, ranging from 0.7 to 0.9, and h is the thickness of the top plate. q represents the tensile strength, and q represents the load on the top plate.

[0019] S402. After the filling material reaches the required strength, the frame is moved, and mining and filling are carried out in cycles.

[0020] S403, isolation coal pillars are left on both sides of the goaf, with a width that meets the following requirements: m is the coal seam thickness, and h is the mining depth;

[0021] S5. Grouting operation for overburden separation:

[0022] S501. Grouting is carried out on both sides of the first mining face. The grouting target layer is located in the overlying delamination development zone below the key layer.

[0023] S502, the grouting hole spacing design meets dual-condition control: ,in For the critical layer thickness, For the tensile strength of the key layer, For critical layer loads;

[0024] S6. Cyclic operation: Sequentially carry out goaf filling and delamination grouting until the mining area is completely mined out.

[0025] Preferably, the ground filling station in S2 integrates grout preparation, pressurization and transportation functions, and the vertical grouting borehole and horizontal pipeline are made of seamless steel pipe with a pressure resistance of ≥10MPa.

[0026] Preferably, the filler grout mix ratio in S3 is:

[0027] Goaf filling grout: gangue aggregate accounts for 60%-70%, cementitious materials (cement + fly ash) account for 20%-30%, and water-cement ratio is 0.8-1.2;

[0028] Delamination grouting slurry: fly ash content ≥50%, clay content ≤20%, additives (retarder + expansion agent) content 3%-5%.

[0029] Preferably, the isolation coal pillar in S403 is replaced by a gangue bag filling body, and the width of the filling body is... Simultaneously satisfy the shear strength verification: τ_filler > 0.3γh, where γ is the unit weight of the overlying rock strata.

[0030] Preferably, the timing of the delamination grouting in S502 is determined based on the periodic collapse characteristics of the roof slab, the dynamic adjustment range of the grouting pressure is 1-5 MPa, and the grout diffusion radius is ≥15 m.

[0031] Preferably, the expansion agent added to the delamination grout is calcium-based bentonite, with a dosage of 3%-5%, and the initial setting time of the grout is controlled to be 2-4 hours.

[0032] Preferably, after the mining area in S6 is completed, the surface subsidence is monitored, and the subsidence control targets are: horizontal deformation ≤ 2 mm / m, curvature deformation ≤ 0.2 mm / m².

[0033] In summary, this application includes the following beneficial technical effects:

[0034] 1. The subsidence control capability is significantly enhanced. The filling of the goaf forms a rigid support layer that directly absorbs the pressure from the roof. The overburden separation grouting creates a hydraulic barrier below the key layer to inhibit the expansion of the separation. The two work together to construct a three-dimensional control structure of lower support and upper sealing, which greatly reduces the amount of surface subsidence. Compared with the single separation grouting method, the control efficiency is improved by more than 40%. In sensitive areas such as farmland or nature reserves, the subsidence deformation can be stably maintained within the safe threshold, avoiding ecological damage. The control of surface subsidence reduces the cost of land reclamation and protects surface buildings.

[0035] 2. The overall resource recovery and utilization rate is improved. The coal pillar-free mining design eliminates the traditional isolation coal pillar, improves the coal resource recovery rate, reduces resource waste, and improves the comprehensive utilization rate of coal gangue as the main filling material. It effectively alleviates the land occupation and environmental pollution caused by gangue stockpiling. Through differentiated slurry ratio, the resource utilization of waste is realized and the cost of raw materials is reduced.

[0036] 3. Optimization of process efficiency and mining continuity: Goaf filling and delamination grouting are implemented in stages. Goaf filling is carried out at the first mining face, and delamination grouting is carried out at the working faces on both sides. This reduces the interference of filling operations on the mining cycle. The precise design of filling step distance and grouting hole spacing ensures rapid formation of the filling body. Seamless connection of frame shifting operations simplifies the overall process, improves mining efficiency, and shortens the mine production cycle. Attached Figure Description

[0037] Figure 1 This is an overall structural block diagram of a three-dimensional filling surface subsidence reduction mining method for goaf-overburden separation in an embodiment of this application;

[0038] Figure 2 This is a three-dimensional filling diagram of a surface subsidence reduction mining method for three-dimensional filling of goaf-overburden separation layer in an embodiment of this application. Detailed Implementation

[0039] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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.

[0040] like Figures 1-2 According to an embodiment of the present invention, a method for reducing surface subsidence through three-dimensional backfilling of goaf-overburden delamination is provided, the method comprising the following steps:

[0041] S1. Mining area planning and working face design:

[0042] S101. Design a longwall mining system and divide the mining area into several working faces;

[0043] S102. The first mining face in the middle of the mining area is set as the goaf filling working face, and the two working faces are successively implemented with delamination grouting and goaf filling.

[0044] S2. Construction of the ground filling system:

[0045] S201. A ground filling station shall be built in the middle of the main roadway of the mining area for slurry preparation and pressurized transportation;

[0046] S202, vertical grouting drilling is carried out from the ground to the main roadway of the mining area, and horizontal conveying pipelines are laid in the main roadway of the mining area to each working face;

[0047] S3. Filling parameter design:

[0048] S301. Based on geological and mining conditions and surface subsidence control targets, the filling rate and filling intensity are determined through numerical simulation.

[0049] S302. Prepare filling grouts with different proportions for use in goaf filling and delamination grouting, respectively.

[0050] S4. Goaf filling operation:

[0051] S401. Slurry is transported behind the first mining face, and the filling step distance is designed to meet the following requirements: ,

[0052] Where k is the safety factor, ranging from 0.7 to 0.9, and h is the thickness of the top plate. q represents the tensile strength, and q represents the load on the top plate.

[0053] S402. After the filling material reaches the required strength, the frame is moved, and mining and filling are carried out in cycles.

[0054] S403, isolation coal pillars are left on both sides of the goaf, with a width that meets the following requirements: m is the coal seam thickness, and h is the mining depth;

[0055] S5. Grouting operation for overburden separation:

[0056] S501. Grouting is carried out on both sides of the first mining face. The grouting target layer is located in the overlying delamination development zone below the key layer.

[0057] S502, the grouting hole spacing design meets dual-condition control: ,in For the critical layer thickness, For the tensile strength of the key layer, For critical layer loads;

[0058] S6. Cyclic operation: Sequentially carry out goaf filling and delamination grouting until the mining area is completely mined out.

[0059] In this embodiment, the ground filling station in S2 integrates grout preparation, pressurization and transportation functions. The vertical grouting borehole and horizontal pipeline are made of seamless steel pipe with a pressure resistance of ≥10MPa.

[0060] This design ensures the stability of high-pressure grout delivery. When vertical drilling penetrates rock strata, the seamless steel pipe's resistance to shear deformation is increased by 50% compared to ordinary steel pipes. Horizontal pipelines are laid along the main roadway of the mining area to each working face, with a pressure resistance of ≥10MPa, allowing them to withstand twice the maximum working pressure (5MPa) of the separation grouting, preventing pipe burst accidents. The filling station is located in the middle of the main roadway of the mining area, shortening the total pipeline length by 30% and reducing pressure loss.

[0061] In this embodiment, the filler grout mix ratio in S3 is:

[0062] Goaf filling grout: gangue aggregate accounts for 60%-70%, cementitious materials (cement + fly ash) account for 20%-30%, and water-cement ratio is 0.8-1.2;

[0063] Delamination grouting slurry: fly ash content ≥50%, clay content ≤20%, additives (retarder + expansion agent) content 3%-5%;

[0064] Differentiated proportions achieve functional adaptation: The high aggregate ratio of the goaf filling grout forms a skeleton structure with a 3-day compressive strength of 2.5MPa, meeting the strength requirements for frame relocation. The fly ash ratio of the delamination grout is ≥50%, which reduces the viscosity to 35mPa·s, ensuring that the grout has a diffusion radius of ≥15m in a 0.5mm crack. The additive contains 0.8%-1.2% hydroxycarboxylate retarder, which precisely controls the initial setting time error by ±10 minutes.

[0065] In this embodiment, the isolation coal pillar in S403 is replaced by a gangue bag filling body, and the width of the filling body is... Simultaneously satisfy the shear strength verification: τ_filler > 0.3γh, where γ is the unit weight of the overlying rock stratum;

[0066] The gangue bag filling body consists of gangue particles encapsulated in double-layer antistatic woven bags with a particle size of 5-20mm, replacing traditional coal isolation pillars. The shear strength formula τ_filling body > 0.3γh ensures that when the mining depth h = 500m and γ = 25kN / m³, the shear strength of the filling body is > 3.75MPa, which is sufficient to resist the lateral pressure of the slurry. Based on a working face length of 200m, this scheme reduces coal loss by approximately 80,000 tons / year.

[0067] In this embodiment, the timing of the delamination grouting in S502 is determined based on the periodic collapse characteristics of the roof slab, the dynamic control range of the grouting pressure is 1-5MPa, and the grout diffusion radius is ≥15m;

[0068] The grouting pressure is linked to the collapse of the roof. The periodic pressure signal is identified by the microseismic monitoring system, and the grouting pressure is automatically increased from the benchmark value of 1MPa to 5MPa. The high-pressure grouting causes the grout to generate a self-cracking effect in the delamination crack, the diffusion radius increases from 8m to 18m, and the delamination filling rate increases from 70% to 92%.

[0069] In this embodiment, the expansion agent added to the delamination grout is calcium-based bentonite, with a dosage of 3%-5%, and the initial setting time of the grout is controlled to be 2-4 hours;

[0070] Calcium-based bentonite has a water swelling rate of ≥300%, effectively compensating for the closed space of the delamination. The initial setting time is controlled by the graded control of the composite retarder. The initial setting time of the filling grout in the goaf is ≤4 hours to ensure the mining cycle. The initial setting time of the grouting grout in the delamination is 2-4 hours to match the grouting operation cycle.

[0071] In this embodiment, after the mining area in S6 is completed, the surface subsidence is monitored. The subsidence control targets are: horizontal deformation ≤ 2 mm / m, curvature deformation ≤ 0.2 mm / m².

[0072] Using a total station and InSAR remote sensing technology for dual verification, the horizontal deformation ≤2mm / m ensures that the width of cracks in the walls of surface buildings is <5mm, and the curvature deformation ≤0.2mm / m² corresponds to a surface subsidence basin radius >500m. After applying this method, the maximum subsidence is only 480mm.

[0073] It should be noted that the first mining face in the middle of the mining area is prioritized for goaf filling to form a high-strength rigid support. When the working faces on both sides are subsequently subjected to delamination grouting, this filling body becomes the stress anchoring base of the key layer. The two form a temporal and spatial progressive synergy. Goaf filling inhibits the collapse of the direct roof, and delamination grouting blocks the development of overburden fissures. Together, they reduce the surface subsidence by 55%-70%, solving the problem of insufficient control effect caused by the lack of lower support in traditional delamination grouting.

[0074] The goaf filling grout is mainly composed of gangue aggregate, accounting for 60%-70%. The high aggregate ratio ensures that the filling body can quickly bear the roof pressure, and its early strength growth rate reaches 0.5MPa / day, which meets the requirements of the working face shifting cycle. The delamination grout uses fly ash-based materials, accounting for ≥50%, and its low viscosity characteristics ensure that the grout has a diffusion radius of ≥15m in the overburden fissures.

[0075] The goaf filling body bears more than 70% of the roof load, reducing the bending deformation of the key layer by 60%; the delamination grouting slurry forms a hydraulic cushion layer below the key layer, and the 5MPa grouting pressure offsets the overburden delamination tension. The coupling effect of the two changes the distribution of the three zones of rock movement, increases the height of the bending zone by 2-3 times, and compresses the development range of the fault zone by 40%, thus inhibiting surface subsidence from the source.

[0076] In the embodiments provided by this invention, it should be understood that the disclosed devices, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and other division methods may exist in actual implementation. Modules described as separate components may or may not be physically separated, and components shown as modules may or may not be physical units, i.e., they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of the method in this embodiment according to actual needs.

[0077] The above embodiments are only used to illustrate the technical methods of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical methods of the present invention without departing from the spirit and scope of the technical methods of the present invention.

Claims

1. A method for reducing surface subsidence through three-dimensional backfilling of goaf-overburden separation mining, characterized in that: Includes the following steps: S1. Mining area planning and working face design: S101. Design a longwall mining system and divide the mining area into several working faces; S102. The first mining face in the middle of the mining area is set as the goaf filling working face, and the two working faces are successively implemented with delamination grouting and goaf filling. S2. Construction of the ground filling system: S201. A ground filling station shall be built in the middle of the main roadway of the mining area for slurry preparation and pressurized transportation; S202, vertical grouting boreholes are drilled from the ground to the main roadway of the mining area, and horizontal conveying pipelines are laid in the main roadway of the mining area to each working face; S3. Filling parameter design: S301. Based on geological and mining conditions and surface subsidence control targets, the filling rate and filling intensity are determined through numerical simulation. S302. Prepare filling grouts with different proportions for use in goaf filling and delamination grouting, respectively. S4. Goaf filling operation: S401. Slurry is transported behind the first mining face, and the filling step distance is designed to meet the following requirements: , Where k is the safety factor, ranging from 0.7 to 0.9, and h is the thickness of the top plate. q represents the tensile strength, and q represents the load on the top plate. S402. After the filling material reaches the required strength, the frame is moved, and mining and filling are carried out in cycles. S403, isolation coal pillars are left on both sides of the goaf, with a width that meets the following requirements: m is the coal seam thickness, and h is the mining depth; S5. Grouting operation for overburden separation: S501. Grouting is carried out on both sides of the first mining face, with the grouting target layer located in the overlying delamination development zone below the key layer. S502, the grouting hole spacing design meets dual-condition control: ,in For the critical layer thickness, For the tensile strength of the key layer, For critical layer loads; S6. Cyclic operation: Sequentially carry out goaf filling and delamination grouting until the mining area is completely mined out.

2. The method for reducing surface subsidence through three-dimensional backfilling of goaf-overburden separation as described in claim 1, characterized in that: The ground filling station in S2 integrates grout preparation, pressurization and transportation functions. The vertical grouting boreholes and horizontal pipelines are made of seamless steel pipes with a pressure resistance of ≥10MPa.

3. The method for reducing surface subsidence through three-dimensional backfilling of goaf-overburden separation as described in claim 1, characterized in that: The filler grout mix ratio in S3 is: Goaf filling grout: gangue aggregate accounts for 60%-70%, cementitious materials (cement + fly ash) account for 20%-30%, and water-cement ratio is 0.8-1.2; Delamination grouting slurry: fly ash content ≥50%, clay content ≤20%, additives (retarder + expansion agent) content 3%-5%.

4. The method for reducing surface subsidence through three-dimensional backfilling of goaf-overburden separation as described in claim 1, characterized in that: The isolation coal pillar in S403 is replaced by a gangue bag filling body, and the width of the filling body is... Simultaneously satisfy the shear strength verification: τ_filler > 0.3γh, where γ is the unit weight of the overlying rock strata.

5. The method for reducing surface subsidence through three-dimensional backfilling of goaf-overburden separation as described in claim 1, characterized in that: The timing of the delamination grouting in S502 is determined based on the periodic collapse characteristics of the roof slab, the dynamic control range of the grouting pressure is 1-5MPa, and the grout diffusion radius is ≥15m.

6. The method for reducing surface subsidence through three-dimensional backfilling of goaf-overburden separation as described in claim 1, characterized in that: The expansion agent added to the delamination grout is calcium-based bentonite, with a dosage of 3%-5%, and the initial setting time of the grout is controlled to be 2-4 hours.

7. The method for reducing surface subsidence through three-dimensional backfilling of goaf-overburden separation as described in claim 1, characterized in that: After the mining area in S6 is completed, the surface subsidence is monitored. The subsidence control targets are: horizontal deformation ≤ 2 mm / m, curvature deformation ≤ 0.2 mm / m².

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