A floor water disaster prevention method based on mine pressure regulation

Abstract

The application discloses a floor water disaster prevention method based on mine pressure regulation and control, and belongs to the technical field of mine disaster prevention and control. The method is characterized in that: a large-diameter pressure relief borehole is constructed at the working face roadway side, the concentrated stress is transferred to the deep part, and a shallow coal body impedance area is formed; roof blasting is performed at the goaf side, the collapsed gangue is accumulated on the goaf floor to form a collapsed gangue impedance layer, and pressure stress is generated on the floor; the floor damage depth is dynamically monitored, the ratio of the floor aquiclude thickness to the safe aquiclude thickness is obtained, and the borehole spacing, the blasting hole spacing and the charge amount are adjusted in a graded progressive manner according to the 1.3 times and 1.1 times two-level threshold values. The application actively inhibits the downward expansion of the floor damage from the mechanical source, is simple and convenient to construct, has low cost, realizes parameter optimization through graded progressive regulation, and effectively reduces the floor water disaster risk.

Description

Technical Field

[0001] This invention relates to the field of mine disaster prevention and control technology, specifically a method for preventing floor water hazards based on mine pressure regulation. Background Technology

[0002] In coal mining, floor water hazards are one of the major hazards threatening safe production. From a mechanical perspective, the redistribution of mine pressure caused by mining leads to the downward extension of floor damage. When the damage penetrates the aquifer, a water inrush channel is formed. Currently, prevention and control technologies for floor water hazards mainly focus on passive treatment, i.e., sealing the floor cracks after they have formed or have affected the aquifer. For example, floor grouting reinforcement reduces permeability by injecting grout into the cracks and aquifer; leaving waterproof coal pillars isolates the impact of mining by preserving a portion of unmined coal. These methods involve large-scale engineering and high costs, and heavily rely on accurate prediction of the extent of floor damage. If the judgment is inaccurate or the construction is not in place, the risk of water inrush remains. Under conditions of high-pressure water and deep mining, floor crack development is sudden and concealed, making it difficult for traditional methods to achieve timely and effective full-process control.

[0003] Compared to simply relying on blocking hydraulic channels, proactively controlling mine pressure distribution during mining operations and suppressing the development of floor damage depth can reduce the likelihood of water hazards at their source. Existing research indicates that large-diameter boreholes in the ribs can transfer stress to deeper areas, and pre-splitting blasting of the roof can alter cantilever structures and utilize collapsed waste rock to fill goafs. However, these are mostly applied as independent technologies in rockburst prevention or roof control, and a systematic solution for synergistic floor water hazard prevention has yet to be found. Furthermore, existing dynamic monitoring methods are mostly post-hoc analyses, lacking a tiered, progressive control mechanism based on measured damage depth.

[0004] In view of this, the present invention proposes a method for preventing water damage to the mine floor based on mine pressure regulation, which solves the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] A method for preventing floor water hazards based on mine pressure regulation includes the following steps: S1: Based on the mine's geological and hydrogeological data, determine the location of the aquifer in the foundation, the thickness of the safe water-retaining layer, and the dangerous area for foundation damage; S2: Construct large-diameter stress relief boreholes in the coal seam in the vertical mining direction of the sidewall of the working face roadway. The boreholes are more than 200m ahead of the working face, and the borehole diameter is 150-300mm. The plastic zone formed by the boreholes will create a shallow coal body resistance zone and transfer the shallow concentrated stress to the deep coal body, thereby inhibiting floor slippage and damage propagation. S3: Roof blasting is carried out through roof blasting holes on the side of the goaf to cause the exposed roof to break and collapse in time, compact the goaf and form a collapse gangue resistance layer, reduce the sliding stress of the floor and enhance the floor's anti-sliding ability. S4: Dynamically monitor the depth of damage to the base plate, arrange test boreholes in the base plate, and periodically measure the thickness of the aquifer (the distance between the aquifer and the maximum damage value of the base plate). S5: Based on the changes in the thickness of the bottom slab waterproof layer and the thickness of the safety waterproof layer obtained from monitoring, adjust the subsequent construction parameters: when the thickness of the bottom slab waterproof layer reaches 1.3 times the thickness of the safety waterproof layer, increase the spacing of the large-diameter pressure relief boreholes; when the thickness of the bottom slab waterproof layer reaches 1.1 times the thickness of the safety waterproof layer, simultaneously increase the borehole spacing, the spacing of the top slab blasting holes, and the amount of explosives per hole. S6: Repeat steps S3 to S5 until the mining of the working face is completed or the pretreatment of water hazards on the bottom plate is completed.

[0007] Preferably, in step S2, the initial spacing of the large-diameter pressure relief boreholes is 3m. When the monitored thickness of the bottom plate waterproof layer reaches 1.3 times the thickness of the safe waterproof layer, a densified borehole is constructed between the two boreholes, that is, the spacing of the large-diameter pressure relief boreholes is reduced to 1.5m; when it reaches 1.1 times, another densified borehole is constructed between the two large-diameter pressure relief boreholes, that is, the spacing of the large-diameter pressure relief boreholes is densified to 0.75m.

[0008] Preferably, in step S3, the initial spacing of the top plate blasting holes is 15m, and the initial charge per hole is 25-40kg. When the monitored thickness of the bottom plate waterproof layer reaches 1.1 times the thickness of the safe waterproof layer, an additional blasting hole is drilled between the two blasting holes, that is, the spacing of the top plate blasting holes is reduced to 7.5m, and the charge is increased by 10%-20%.

[0009] Preferably, in step S4, the bottom plate damage depth measuring points are arranged in the roadways on both sides of the working face, with a group of points spaced 30 to 50 m apart along the advancing direction, and the damage depth is measured using high-density electrical resistivity or ultrasonic methods.

[0010] Preferably, when adjusting the construction parameters in step S5, the densification of large-diameter pressure relief boreholes is performed first. If the depth of damage continues to increase within two consecutive monitoring cycles after densification, and the advance distance corresponding to each monitoring cycle is 30-50m, then the parameters of the top plate blasting holes are adjusted.

[0011] Preferably, the formation mechanism of the shallow coal body resistance zone is as follows: after the construction of the large-diameter pressure relief borehole, the coal body around the borehole undergoes plastic deformation, which causes the stress in the shallow coal body to transfer to the deeper part. At the same time, the shallow coal body can resist the sliding of the bottom strata, thereby limiting the downward extension of the bottom failure depth.

[0012] Preferably, the enhancement mechanism of the collapsed gangue resistance layer is as follows: after the roof is blasted, the exposed length of the roof is reduced, thereby reducing the stress transmitted to the bottom plate. At the same time, the collapsed gangue resistance layer accumulates in the bottom plate of the lateral goaf area, generating compressive stress on the bottom plate, thereby inhibiting the heave and slippage of the bottom plate.

[0013] Preferably, the large-diameter pressure relief borehole in step S2 and the roof blasting in step S3 are coordinated in terms of construction sequence: the large-diameter pressure relief borehole and roof blasting are completed 200m ahead of the working face, so that the shallow coal body impedance zone and the collapsed gangue impedance layer form a continuous impedance barrier in space.

[0014] Preferably, when there is a fault or fracture zone in the bottom plate of the working face, the spacing of the large-diameter pressure relief boreholes in the fault-affected area is increased to 0.75m, and the hole spacing of the top plate blasting holes is reduced to 7.5m, with the single hole charge increased by 10% to 20%.

[0015] Preferably, in step S4, the monitoring frequency is to measure the depth of damage to the base plate every 30-50m of advancement, and compare the measurement results with the thickness of the safety waterproof layer in real time, dynamically adjust the subsequent construction parameters, until the thickness of the base plate waterproof layer is stable at more than 1 times the thickness of the safety waterproof layer.

[0016] The beneficial effects of this invention are: This invention utilizes large-diameter stress-relief boreholes drilled in the sidewalls of the working face roadway to transfer concentrated stress to deeper layers, forming a shallow coal seam resistance zone and reducing shear stress in the floor. Simultaneously, combined with blasting of the roof sidewall in the goaf, the accumulated collapsed rock forms a collapsed rock resistance layer, generating compressive stress on the floor and inhibiting fracture opening. These two resistance measures are spatially coordinated to form a continuous resistance barrier. Based on the ratio of the floor water-resistant layer thickness to the safe water-resistant layer thickness, the borehole spacing, blast hole spacing, and charge amount are adjusted progressively in two threshold stages: 1.3 times and 1.1 times. This method proactively controls the extent of floor damage from a mechanical perspective, is simple to construct, reduces costs, and avoids over-construction through tiered control, making it highly adaptable to various engineering projects. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] in: Figure 1 A schematic diagram showing the distribution of mine pressure and water hazards before regulation; Figure 2 A schematic diagram showing the distribution of mine pressure and water hazards after regulation; Figure 3 A schematic diagram of the coal seam cross-section after adjustment of mine pressure and water hazard distribution; In the picture: 1. Floor aquifer; 2. Safety water-retaining layer; 3. Working face roadway; 4. Working face mining direction; 5. Large-diameter pressure relief borehole; 6. Shallow coal body resistance zone; 7. Shallow concentrated stress in the coal body before regulation; 8. Deep concentrated stress in the coal body after regulation; 9. Floor slip path; 10. Roof blasting hole; 11. Exposed roof; 12. Fracture collapse; 13. Collapsed gangue resistance layer; 14. Floor failure depth; 15. Floor test borehole; 16. Floor water-retaining layer. Detailed Implementation

[0019] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0020] Example 1: like Figures 1-3 As shown in the figure, this embodiment takes a typical mining face in a coal mine as an example to illustrate the complete implementation process of the bottom water hazard prevention method based on mine pressure control.

[0021] Geological conditions: The working face has a strike length of 800m, a dip length of 220m, a coal seam thickness of 4.5m, and a burial depth of 650m. The first aquifer in the floor is an Ordovician limestone aquifer located 42m below the coal seam floor, and the second safety aquifer is 21m thick. The floor strata are mainly mudstone and siltstone, with an average uniaxial compressive strength of 35MPa, classifying the conditions as mining-induced water hazards.

[0022] Step S1: Based on the mine geological columnar section, hydrogeological survey report and 3D seismic exploration results, it is determined that the bottom aquifer 1 is located 42-58m below the coal seam, with aquifer water pressure of 2.1MPa; the thickness of the safety aquitard 2 is 21m; the dangerous area of ​​bottom failure is mainly distributed in the middle of the working face, 200-600m away from the opening, and there is a set of primary joints in the bottom rock strata in this section.

[0023] Step S2: On the solid coal side of the working face roadway 3, construct a large-diameter stress-relief borehole 5 perpendicular to the mining direction. Borehole parameters: diameter 200mm, depth 25m, construction distance 200m ahead of the working face, initial borehole spacing set at 3m. After construction, the coal around the borehole undergoes plastic deformation or borehole collapse. The stress concentration location in the coal body shifts from the shallow concentrated stress 7 before regulation to the deep concentrated stress 8 after regulation, forming a shallow coal body resistance zone 6. Actual measurements show that the stress in this shallow coal body in this zone decreases from 32MPa to 24MPa, reducing the mining-induced shear stress on the floor strata, thereby inhibiting floor slippage and damage propagation.

[0024] Step S3: Arrange roof blasting holes 10 along the dip side of the goaf. Hole parameters: depth 18m (penetrating the key roof layer), hole diameter 89mm, initial hole spacing 15m, single-hole charge 32kg (permitted emulsion explosive for coal mines). After detonation, the exposed roof 11 fractures and collapses along the predetermined fracture surface 12, compacting and filling the goaf to form a collapsed gangue resistance layer 13. Roof blasting reduces the stress level transmitted to the floor by approximately 30%, and the resistance layer generates compressive stress on the floor, enhancing its resistance to slippage and cracking.

[0025] Step S4: Implement dynamic monitoring of the floor slab failure depth 14. Floor slab test boreholes 15 are arranged in the floor slab of working face roadway 3, spaced 40m apart along the advancing direction, for a total of 16 boreholes 15. Each test borehole 15 is drilled to a depth of 30m below the floor slab, and the floor slab failure depth 14 is measured using a high-density electrical resistivity tomography (EDT). Initial measurements show that the floor slab failure depth 14 is 11m, and the thickness of the floor slab waterproof layer 16 is 30m. The thickness of the floor slab waterproof layer 16 is approximately 1.43 times (greater than 1.3 times) the thickness of the safety waterproof layer 2 (21m). No adjustments are made to the parameters at this time.

[0026] Step S5: As the working face advanced to 450m, monitoring revealed that the depth of damage increased to 15m, and the ratio of the thickness of the bottom slab waterproof layer 16 to the thickness of the safety waterproof layer 2 reached 1.24 (1.3 > 1.24 > 1.1). At this point, the spacing of the large-diameter pressure relief boreholes 5 was increased: a new borehole was drilled between the two existing boreholes, reducing the borehole spacing from the initial 3m to 1.5m. After advancing for one more monitoring cycle (40m), the depth of damage to the bottom slab 14 still increased to 16m, and the ratio of the thickness of the bottom slab waterproof layer 16 to the thickness of the safety waterproof layer 2 reached 1.2 (1.3 > 1.24 > 1.2). Subsequent monitoring showed that the depth of damage to the bottom slab 14 stabilized at 16m and did not increase further. Subsequently, when the ratio of the thickness of the bottom aquitard 16 to the thickness of the safety aquitard 2 reached 1.1, a second-level reinforcement was implemented: the spacing of borehole 5 was increased to 0.75m, the spacing of the top blasting holes 10 was reduced to 7.5m, and the charge was increased by 20% (total 38.4kg). The final damage depth was controlled within 18m, and the aquifer was not breached.

[0027] Step S6: Since the large-diameter pressure relief borehole 5 in step S2 has been completed ahead of schedule, there is no need to repeat S2. Repeat steps S3 to S5 (dynamically adjust blasting parameters and any new boreholes based on monitoring results). Until the entire working face is mined out, the depth of the bottom plate failure 14 is always controlled to be outside the thickness of the safety water-proof layer 2.

[0028] By combining the large-diameter pressure relief borehole 5 with the top plate blasting hole 10, and with a graded and progressive parameter adjustment strategy, proactive prevention and control of water damage at the source of the bottom plate was achieved. At the same time, excessive construction was avoided, and the amount of drilling and blasting work was only about 40% of that of a one-time reinforcement scheme.

[0029] Example 2: Initial parameters: In normal sections without structural influence, the initial spacing of the large-diameter pressure relief boreholes 5 is set at 3m, with a borehole diameter of 200mm and a lead distance of 230m. The initial spacing of the roof blasting holes 10 is 15m, the initial charge per hole is 30kg (permitted emulsion explosives for coal mines), the blasting depth is 18m, and the inter-hole delay detonation method is used.

[0030] First-level adjustment (the thickness of the bottom water-proof layer 16 reaches 1.3 times the thickness of the safe water-proof layer 2): When the measured thickness of the bottom water-proof layer 16 is less than 21m × 1.3 = 27.3m, the first-level reinforcement is implemented. A large-diameter coal seam borehole is drilled between the two boreholes, i.e., the borehole spacing is 3m ÷ 2 = 1.5m. After reinforcement, borehole stress gauges are used for monitoring. The results show that the stress value around the borehole further decreases (from the initial 26MPa to 21MPa), and the growth rate of the bottom failure depth 14 decreases from 0.12m / d to 0.08m / d.

[0031] Second-level adjustment (bottom plate water-resistant layer thickness reaches 1.1 times the thickness of safety water-resistant layer 2): The measured thickness of bottom plate water-resistant layer 16 is less than 21m × 1.1 = 23.1m, so the second-level densification is implemented. The spacing of subsequent large-diameter pressure relief boreholes 5 in the coal seam is increased to 0.75m; the spacing of roof blasting holes 10 is reduced to 7.5m, and the charge per hole is increased by 20%, i.e., 30kg × 1.20 = 36kg (not exceeding the maximum charge of 48kg allowed by the coal mine safety regulations). After densification, the depth of destruction stops increasing and stabilizes at around 18m.

[0032] Comparison of effects: In the comparison section on the same working face (without graded reinforcement), the final damage depth reached 21m, affecting the safety waterproof layer 2 and posing a risk of water inrush. In contrast, the section with graded reinforcement effectively controlled the damage depth to within 18m, demonstrating the effectiveness of the spacing adjustment rules. Furthermore, graded reinforcement saved approximately 25% of the drilling work and 40% of the roof blasting work compared to one-time reinforcement (reinforcement only when necessary).

[0033] Example 3: This embodiment illustrates the arrangement and testing operation of the test hole 15 on the base plate.

[0034] Arrangement of Borehole 15 for Floor Testing: In the floor strata of roadway 3 in the working face, a borehole 15 for floor testing is arranged every 30m along the advancing direction. This working face is 800m long, with approximately 26 boreholes arranged in total, numbered 15-1 to 15-26. Each borehole 15 consists of an inclined borehole with a depth of 30m (45° angle of attack, final borehole location 20m below the coal seam floor, affecting a 21m thick safety aquitard 2), and a borehole diameter of not less than 89mm.

[0035] Measurement Method: This observation was conducted using a DC electrical resistivity tomography (DCIP) instrument in conjunction with electrode cables tailored to the characteristics of the borehole. Copper ring electrodes were fabricated at 2-meter intervals, starting from one end. PVC pipes were used as conduits to guide the electrode cables to the designated locations within the borehole. After the electrode cables were delivered, the borehole was grouted (using a 63.5mm diameter drill rod, grouting began from the bottom of the hole until the borehole was completely filled). Grouting ensured good contact between the electrode cables and the underlying rock mass, reducing the occurrence of anomalies due to poor contact. Strict borehole sealing was required to guarantee the accuracy of the observation data. The DCIP observation plan was implemented after sealing. After each observation, the cable ends were sealed in a bag and hung on the borehole wall to prevent moisture damage to the cable joints.

[0036] Data recording and processing: After each measurement, the damage depth data of each test borehole 15 on the base plate is entered into the database. Kriging interpolation is used to generate a contour map of the damage depth 14 on the base plate, which is used to identify dangerous areas.

[0037] Through systematic placement and periodic measurements of the base plate test boreholes 15, the dynamic evolution curve of the base plate failure depth 14 was obtained. Near the fault, the density of the base plate test boreholes 15 was increased to a spacing of 20m, successfully capturing the anomaly of a sudden increase in failure depth from 16m to 18m, providing an early warning for timely parameter adjustments. Compared to the traditional method of only drilling temporarily in hazardous areas, this scheme provides a higher density of base plate test boreholes 15, continuous data, and a reduced response lag distance to 15m.

[0038] Example 4: This embodiment explains in detail the mechanical mechanism of the impedance region 6 in the shallow coal body and provides numerical simulation verification.

[0039] Formation Process: After constructing large-diameter stress-relief boreholes 5 (200mm diameter, 3m spacing) on ​​the sidewall of the working face roadway 3, the coal around the boreholes underwent plastic deformation due to stress concentration exceeding its yield strength. According to the theory of elastoplastic mechanics, a plastic ring will form around the boreholes. In this embodiment, a combination of FLAC3D numerical simulation and on-site borehole inspection was used to determine that the thickness of the plastic ring is approximately 1.5–2.5m. The coal within this plastic zone underwent irreversible deformation, but did not lose its bearing capacity; instead, it manifested as a stress-reduced zone, i.e., the shallow coal resistance region 6.

[0040] Impedance mechanism: The impedance zone 6 in the shallow coal seam inhibits floor failure in the following ways: Stress transfer: The formation of the plastic zone causes the peak value of the lateral support pressure of the working face to shift to the deeper part of the coal body (the measured peak value position shifted from 8m to 15m from the coal wall), thereby reducing the mining-induced shear stress on the bottom rock strata.

[0041] Shear stress attenuation: Numerical simulations show that after drilling and decompression, the peak shear stress at the key layer of the base plate decreased from 2.8 MPa to 1.9 MPa, a decrease of about 32%, thereby inhibiting the depth expansion of the plastic zone of the base plate.

[0042] Actual results: In the section with large-diameter pressure relief boreholes 5, the stress level of the floor slab was monitored using a borehole stress gauge. The results showed that the stress level of the floor slab decreased from 32 MPa in the un-drilled section to 24 MPa. Simultaneously, the floor slab slippage was monitored using a multi-point displacement gauge. The cumulative slippage of the floor slab in the borehole section (25 mm) was only one-third of that in the un-drilled section (75 mm). This verifies the effective suppression of floor slab slippage and damage propagation by the shallow coal seam impedance zone 6.

[0043] Example 5: This embodiment illustrates the mechanical reinforcement mechanism of the collapsed gangue impedance layer 13 and provides field measurement data.

[0044] Formation process: After the roof blast hole 10 is detonated, the hard, exposed roof 11 (mainly medium sandstone, 8m thick) fractures and collapses along the weak blasting surface. The collapsed gangue gradually compacts in the goaf floor and coal wall area, forming the collapsed gangue resistance layer 13.

[0045] Impedance mechanism: Stress reduction: The fracture and collapse of the hard, exposed roof 11 reduced the volume of the coal seam supporting the rock strata, thereby reducing the stress level transmitted to the floor slab, decreasing the floor slab stress level from 32 MPa to 24 MPa, a reduction of approximately 25%.

[0046] Vertical support: After the collapsed gangue resistance layer 13 filled the goaf, it bore part of the pressure of the overlying rock strata and reduced the vertical load on the solid coal side floor.

[0047] Increased resistance: The collapsed gangue resistance layer 13 generates compressive stress on the bottom rock layer. Using a pressure cell, the pressure of the collapsed gangue resistance layer 13 on the bottom plate is approximately 0.4 to 0.6 MPa.

[0048] Fracture closure: Compressive stress causes existing fractures in the base plate to tend to close. Acoustic wave testing shows that the longitudinal wave velocity of the base plate rock mass increased from 2800 m / s to 3150 m / s after blasting. The increase in wave velocity reflects a decrease in fracture opening and a reduction in permeability coefficient.

[0049] Drilling water pressure tests were conducted in the blasted section of the roof, and the calculated permeability coefficient of the floor was 1.2 × 10⁻⁶, which was higher than that of the unblasted section. -4 cm / s decreased to 4.0 × 10 -5 The cm / s indicates that the collapsed gangue impedance layer 13 effectively blocked the potential water inrush channel.

[0050] Example 6: This embodiment illustrates the coordinated construction sequence of the large-diameter pressure relief borehole 5 and the top plate blasting hole 10, as well as the formation process of the continuous impedance barrier.

[0051] Timing Design: Advance Stage: After the opening of the working face is completed and before formal mining, immediately construct 5 large-diameter pressure relief boreholes on the solid coal side of the working face roadway 3, with an advance distance of 250m (greater than 200m) and a borehole spacing of 3m, for a total of 267 boreholes; immediately construct 10 roof blasting holes on the goaf side of the working face roadway 3, with an advance distance of 210m (greater than 200m) and a borehole spacing of 15m, for a total of 53 boreholes.

[0052] Spatial Connection: The shallow coal seam impedance zone 6 formed by drilling is located on the solid coal side of the working face (0-25m from the working face), while the collapsed gangue impedance layer 13 formed by roof blasting is located on the goaf side of the working face (0-18m). The two form a spatial overlap in the vicinity of the working face (the overlap area is about 30-50m long), together forming a continuous impedance barrier from the solid coal side of the working face to the goaf side.

[0053] Mechanical coupling: The shallow coal seam impedance zone 6 reduces the shear stress of the floor through stress transfer, inhibiting the development of the failure depth; the collapsed gangue impedance layer 13 promotes the closure of fractures through lateral constraint, blocking the water conduction channel. The synergistic effect of the two makes the failure depth 14 of the floor reach the minimum value in the overlapping zone (only 18m in actual measurement).

[0054] Example 7: This embodiment illustrates the special parameter adjustment and implementation process when there are faults or fracture zones in the bottom plate of the working face.

[0055] Geological conditions: At a depth of 580m, 3D seismic exploration and downhole drilling confirmed the existence of a normal fault with a drop of 2.5m and a dip angle of 65°. The fault fracture zone is approximately 6m wide, affecting an area of ​​about 30m before and after the fault. The rock mass within the fault zone is fractured and has reduced strength, making it a prime pathway for the expansion and failure of the floor.

[0056] Parameter adjustment: Large-diameter pressure relief borehole 5: In the fault-affected area (30m before and after the fault, a total range of 60m), the borehole spacing is reduced from 3m in the normal section to 0.75m.

[0057] Roof blasting hole 10: The hole spacing was reduced from 15m in the normal section to 7.5m, and the charge per hole was increased from 32kg to 38.4kg (an increase of 20%, which did not exceed the safety limit of 48kg).

[0058] Within the fault-affected zone, the densified borehole group formed a stronger shallow coal seam resistance zone 6. Borehole inspection showed a significant reduction in the development of floor fractures near the fault zone, with fracture width decreasing from 0.3 mm in the untreated zone to below 0.1 mm. After roof blasting, the collapsed gangue resistance layer 13 accumulated more densely near the fault zone, with a measured pressure reaching 0.45 MPa, approximately 30% higher than in the normal section. Ultimately, the maximum measured depth of floor failure 14 near the fault zone was 18 m. This scheme successfully prevented the fault zone from becoming a water inrush channel.

[0059] Scope of application: This patented method is applicable to structural conditions where the fault displacement is greater than 1m or the fracture zone width is greater than 2m. For minor faults with a displacement of less than 1m, parameters for normal sections can be referenced or appropriate densification can be applied.

[0060] Work process: After determining the location of the aquifer 1, the thickness of the safety water-retaining layer 2, and the dangerous area for floor damage, large-diameter stress-relief boreholes 5 are first constructed perpendicular to the working face mining direction 4 on the solid coal side of the working face roadway 3. The borehole construction is more than 200m ahead of the working face, with a diameter of 150-300mm and an initial spacing of 3m. The plastic zone formed by the large-diameter stress-relief boreholes 5 constructs a shallow coal body resistance zone 6, and transfers the shallow concentrated stress 7 of the coal body before regulation to the deep concentrated stress 8 of the coal body after regulation, inhibiting the floor slip path 9 and damage propagation. On the goaf side, roof blasting is carried out through roof blasting holes 10, causing the exposed roof 11 to fracture and collapse in time 12, compacting the goaf and forming a collapsed gangue resistance layer 13, reducing floor slip stress and enhancing the floor's anti-slip capability.

[0061] During the working face advancement, the depth of damage to the bottom plate 14 is dynamically monitored. Holes 15 are drilled in the bottom plate, and the thickness of the bottom plate aquifer 16 (the distance between the aquifer and the maximum damage value of the bottom plate) is measured periodically. The measuring points are spaced 30–50 m apart. The depth of damage to the bottom plate 14 is measured once after each monitoring zone advances, using a high-density electrical resistivity tomography (EDT) or ultrasonic method. The measured depth of damage is compared with the thickness of the safety aquifer 2: when the bottom plate aquifer 16 reaches 1.3 times the thickness of the safety aquifer 2, the spacing of the large-diameter pressure relief boreholes 5 is increased to 1.5 m. If the depth of damage continues to increase after this increase, the spacing of the large-diameter pressure relief boreholes 5 is simultaneously increased by 0.75 m, the spacing of the roof blasting holes 10 is reduced to 7.5 m, and the charge per hole is increased by 10%–20%.

[0062] When a fault or fracture zone exists in the working face floor, the spacing of the large-diameter pressure relief boreholes 5 should be increased to 0.75m within the fault-affected zone, and the spacing of the roof blasting holes 10 should be reduced to 0.75m, with the charge increased by 10%–20%. Further adjustments should cease when the thickness of the floor water-resistant layer 16 stabilizes at more than 1.3 times the thickness of the safety water-resistant layer 2; if any measurement value is less than 1.1 times, progress should be suspended and supplementary measures taken. The above construction and monitoring process should be repeated until the working face mining is completed.

[0063] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preventing floor water hazards based on mine pressure regulation, characterized in that, Includes the following steps: S1: Based on the mine's geological and hydrogeological data, determine the location of the bottom aquifer (1), the thickness of the safety water-retaining layer (2), and the dangerous area of ​​bottom damage; S2: In the working face roadway (3) in the vertical mining direction (4), construct a large-diameter pressure relief borehole (5) in the coal seam. The distance between the borehole and the working face is more than 200m. The borehole diameter is 150-300mm. The plastic zone formed by the borehole is used to construct a shallow coal body resistance zone (6) and transfer the shallow concentrated stress (7) of the coal body before regulation to the deep concentrated stress (8) of the coal body after regulation, thereby inhibiting the slip path (9) of the bottom plate and the expansion of damage. S3: Roof blasting is carried out through roof blasting holes (10) on the side of the goaf, so that the exposed roof (11) breaks and collapses in time (12), compacts the goaf and forms a collapse gangue resistance layer (13), reduces the sliding stress of the bottom plate and enhances the sliding resistance of the bottom plate. S4: Dynamically monitor the depth of damage to the base plate (14), arrange test boreholes (15) in the base plate, and periodically measure the thickness of the waterproof layer (16) of the base plate and the distance between the aquifer and the maximum value of the damage to the base plate; S5: Based on the changes in the thickness of the bottom slab waterproof layer (16) and the safety waterproof layer (2) obtained from monitoring, adjust the subsequent construction parameters: when the thickness of the bottom slab waterproof layer (16) reaches 1.3 times the thickness of the safety waterproof layer (2), increase the spacing of the large-diameter pressure relief boreholes (5); when the thickness of the bottom slab waterproof layer (16) reaches 1.1 times the thickness of the safety waterproof layer (2), simultaneously increase the spacing of the large-diameter pressure relief boreholes (5), the spacing of the top slab blasting holes (10), and increase the amount of explosives per hole. S6: Repeat steps S3 to S5 until the mining of the working face is completed or the pretreatment of water hazards on the bottom plate is completed.

2. The method for preventing floor water hazards based on mine pressure regulation according to claim 1, characterized in that, In step S2, the initial spacing of the large-diameter pressure relief boreholes (5) is 3m. When the thickness of the monitored bottom plate waterproof layer (16) reaches 1.3 times the thickness of the safety waterproof layer (2), a densified borehole is constructed between the two boreholes, that is, the spacing of the large-diameter pressure relief boreholes (5) is reduced to 1.5m; when it reaches 1.1 times, a densified borehole is constructed between the two boreholes, that is, the spacing of the large-diameter pressure relief boreholes (5) is densified to 0.75m.

3. The method for preventing floor water hazards based on mine pressure regulation according to claim 1, characterized in that, In step S3, the initial spacing of the top plate blasting holes (10) is 15m, and the initial charge per hole is 25-40kg. When the thickness of the bottom plate waterproof layer (16) reaches 1.1 times the thickness of the safety waterproof layer (2), a blasting hole is drilled between the two blasting holes, that is, the spacing of the top plate blasting holes (10) is reduced to 7.5m, and the charge is increased by 10%-20%.

4. The method for preventing floor water hazards based on mine pressure regulation according to claim 1, characterized in that, The bottom plate test boreholes (15) in step S4 are arranged in the working face roadway (3) at intervals of 30-50m along the working face mining direction (4), and the bottom plate damage depth is measured by high-density electrical resistivity or ultrasonic method (14).

5. The method for preventing floor water hazards based on mine pressure regulation according to claim 1, characterized in that, When adjusting the construction parameters in step S5, the densification of the large-diameter pressure relief borehole (5) is performed first. If the damage depth (14) continues to increase within one monitoring cycle after densification, and the advance distance corresponding to each monitoring cycle is 30-50m, the parameter adjustment of the large-diameter pressure relief borehole (5) and the roof blasting hole (10) is then performed.

6. The method for preventing floor water hazards based on mine pressure regulation according to claim 1, characterized in that, The formation mechanism of the shallow coal body impedance region (6) is as follows: after the construction of the large-diameter pressure relief borehole (5), the coal body around the borehole undergoes plastic deformation, which promotes the transfer of the shallow concentrated stress (7) of the coal body before regulation to the deep concentrated stress (8) of the coal body after regulation. At the same time, the shallow coal body can generate an impedance effect on the sliding path (9) of the bottom plate, thereby limiting the downward expansion of the bottom plate failure depth (14).

7. The method for preventing floor water hazards based on mine pressure regulation according to claim 1, characterized in that, The enhancement mechanism of the collapsed gangue resistance layer (13) is as follows: after the roof is blasted, the exposed length of the roof is reduced, which reduces the stress transmitted to the bottom plate. At the same time, the collapsed gangue resistance layer (13) accumulates in the bottom plate of the lateral goaf area, generating compressive stress on the bottom plate, thereby inhibiting the heave and slippage of the bottom plate.

8. The method for preventing floor water hazards based on mine pressure regulation according to claim 1, characterized in that, The large-diameter pressure relief borehole (5) in step S2 and the roof blasting hole (10) in step S3 are coordinated in terms of construction sequence: the construction of the large-diameter pressure relief borehole (5) and the roof blasting hole (10) is completed 200m ahead of the working face, so that the shallow coal body impedance area (6) and the collapsed gangue impedance layer (13) form a continuous impedance barrier in space.

9. The method for preventing floor water hazards based on mine pressure regulation according to claim 1, characterized in that, When there is a fault or fracture zone in the bottom plate of the working face, the spacing of the large-diameter pressure relief boreholes (5) in the fault-affected area is increased to 0.75m, and the hole spacing of the top plate blasting holes (10) is reduced to 7.5m, and the charge per hole is increased by 10% to 20%.

10. The method for preventing floor water hazards based on mine pressure regulation according to claim 1, characterized in that, The monitoring frequency in step S4 is to measure the depth of damage to the base plate (14) every 30-50m of advancement, and compare the measurement results with the thickness of the safety waterproof layer (2) in real time, and dynamically adjust the subsequent construction parameters until the thickness of the base plate waterproof layer (16) is stable at more than 1 times the thickness of the safety waterproof layer.

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