A method for preventing and controlling dynamic disasters in mines based on long boreholes

Abstract

This invention provides a method for preventing and controlling dynamic disasters in mines based on long boreholes, belonging to the field of mine dynamic disaster prevention and control technology. This method determines the type of complex dynamic disasters in the mine based on past dynamic events and risk assessments of various dynamic disasters, identifies key influencing factors of complex dynamic disasters, and identifies areas requiring pretreatment measures. Combining mine production technology conditions and actual geological conditions, it designs a coal and rock structure control scheme and determines the construction parameters for continuous long boreholes. It increases the permeability of gas-bearing strata by using hydraulic fracturing technology through directional long boreholes, reducing the risk of gas and outbursts. It also reduces the stress concentration layer and water hazard risk of aquifers through directional long borehole drilling. This method enables multi-level, large-space continuous operation, achieving multiple uses for a single borehole. It can simultaneously address the problem of excessive stress relief in certain areas while providing multi-level control and pressure relief for complex dynamic disasters in mines.

Description

Technical Field

[0001] This invention relates to the field of mine dynamic disaster prevention and control technology, and in particular to a mine dynamic disaster prevention and control method based on long boreholes. Background Technology

[0002] As mining depths gradually increase, some mining areas in my country have entered the deep mining stage. Deep mining faces severe "high temperature, high humidity, high risk of fire, high temperature, high risk of water inrush, and high risk of disturbance" environments, making it highly susceptible to mine dynamic disasters, mainly including mine tremors, rock bursts, water inrushes, and coal and gas outbursts. Furthermore, with the scientific development of mining technology, increasing emphasis on safety and the environment, and improved ability to identify hazardous factors and disasters, the mechanisms and prevention measures for single mine dynamic disasters have been extensively studied and successfully applied in disaster prevention and control. At the same time, complex dynamic disasters in mines are gradually becoming a major challenge for the safe and efficient mining of deep coal. The mechanisms of deep complex dynamic disasters are unclear, their causes are complex, and the disasters themselves can trigger each other, making their prevention and control even more difficult.

[0003] Currently, due to the complexity of complex dynamic disasters and limitations in research methods, the main form of prevention and control measures for complex dynamic disasters in mines is single-level control, that is, implementing specialized prevention and control measures for each disaster. This easily leads to excessive stress relief in some areas, such as roof fracturing, large deformation of roadways and walls, and difficulties in support. Therefore, there is an urgent need to propose a prevention and control method for complex dynamic disasters in mines that can provide multi-level control and stress relief for complex dynamic disasters while also addressing the problem of excessive stress relief in some areas.

[0004] Given the suddenness, intensity, and destructive nature of mine dynamic disasters, prevention and control measures for complex mine dynamic disasters should possess the following characteristics: eliminating mining disturbances, transferring high stress concentrations, increasing permeability and reducing pressure, and providing space for pressure relief and shock reduction, all based on regulating the coal and rock structure. Therefore, this invention proposes a mine dynamic disaster prevention and control method based on long boreholes. This method utilizes kilometer-long directional drilling equipment, enabling the modification of borehole inclination and azimuth angles without interrupting drilling operations. It increases permeability and desorption in gas-bearing or water-bearing strata to eliminate outburst or water hazard risks, pre-fractures hard roofs to weaken overburden collapse disturbances, and creates cavitation in deep coal seams to form internal support and external energy absorption structures, achieving multi-level, large-space continuous operation and multi-purpose operation from a single borehole. This method reduces the severity of various mine dynamic disasters by regulating the coal and rock structure to reduce the overburden overhang area, weaken stress concentration, enhance the permeability of the coal and rock mass, and provide energy absorption areas with weak structures. It can simultaneously address the problem of excessive pressure relief in certain areas while implementing multi-level regulation and pressure relief for complex mine dynamic disasters. Summary of the Invention

[0005] This invention provides a method for preventing and controlling dynamic disasters in mines based on long boreholes, in order to address the problems of complex existing mine dynamic disaster prevention and control measures, poor construction continuity, and excessive pressure relief in some areas.

[0006] The method includes the following steps:

[0007] S1: Based on the dynamic events that have occurred in the mine and the risk assessment of each dynamic hazard, determine the type of complex dynamic hazard in the mine, identify the key influencing factors of the complex dynamic hazard and the areas where pretreatment measures need to be taken; combine the mine's production technology conditions and actual geological conditions to determine the construction location, sequence, route and parameters of pretreatment methods for each spatial level of the continuous long borehole.

[0008] S2: Conduct directional long borehole construction according to the long borehole construction process determined in S1 to achieve the purpose of preventing mine dynamic disasters;

[0009] S3: After all the pretreatment work for all dynamic hazard influencing factors in a borehole is completed, the process is moved to the next borehole location and repeated until mining ends or the pretreatment work for dynamic hazard influencing factors in the mine is completed.

[0010] Among them, the complex dynamic disaster type in mines in S1 is a combination of more than one dynamic disaster, including rock bursts, coal and gas outbursts, and water inrush.

[0011] The spatial hierarchy in S1 includes high-gas strata, hard rock strata, aquifers and coal seams;

[0012] The key influencing factors are as follows:

[0013] Key influencing factors for hard rock formations include: rock formation thickness, uniaxial compressive strength, uniaxial tensile strength, bending energy index, initial caving step distance, and periodic caving step distance.

[0014] Key influencing factors of high-gas formations include: original formation gas pressure (relative pressure), formation firmness coefficient, formation failure type, and initial gas release velocity of the formation;

[0015] Key influencing factors of aquifers include: the location of the aquifer area (not all areas of the same rock stratum contain water, and the aquifer area needs to be clearly identified through preliminary geophysical exploration) and the water content;

[0016] Key influencing factors of coal seams include: uniaxial compressive strength, dynamic failure time, impact energy index, elastic energy index, coal seam dip angle, coal seam thickness, and coal pillar width.

[0017] S1 includes the spatial and temporal relationship with the goaf, coal pillar retention, bottom coal thickness, roof pressure, layout of the stop line, pushing speed, and selection of protective layer;

[0018] Actual geological conditions include geological structure, stress distribution, burial depth, and coal seam occurrence characteristics.

[0019] The construction of the S1 medium-length borehole begins with the cut-in point of the working face and proceeds sequentially along the mining direction until the stop line of the working face is reached. Construction on this working face then ends, and the equipment is moved to the next working face. Drilling must be carried out ahead of the working face (leading the disturbance range ahead of the working face, generally 200-300m ahead).

[0020] The location of the S1 medium-length borehole is determined according to the distribution level of each dynamic disaster. A 5-10m space with weak energy absorption structure is reserved outside the anchoring zone of the coal seam (generally with an anchor cable length of 4-10m). The borehole route from the coal seam upwards is designed according to the needs of roof breaking, gas extraction, and water drainage.

[0021] The drilling route and depth are recorded and fed back in real time by the drill bit's GPS positioning system (a trajectory will be displayed on the control panel screen). The route is adjusted appropriately according to the drill bit's trajectory to ensure that the drill hole passes through the predetermined position.

[0022] The drilling begins at the final location of the predetermined route through the coal seam roadway. The treatment proceeds sequentially from top to bottom, depending on the distribution of dynamic hazards in each mine. For example, it could be aquifer-hard rock strata-gas strata-coal seam or hard rock strata-gas strata-aquifer-coal seam. Finally, an energy-absorbing weak structure is constructed outside the coal seam anchorage area through drill bit steering and repeated slotting. The borehole diameter is 150mm.

[0023] The pretreatment methods in S1 include hydraulic fracturing, high-pressure hydraulic fracturing, and ultra-high-pressure hydraulic fracturing.

[0024] The directional long borehole construction in S2 includes:

[0025] a. By using directional long boreholes to construct hydraulic fracturing technology in hard rock strata, fractures are developed, the integrity of hard rock strata is destroyed, and long cantilever structures that are unfavorable to the prevention and control of dynamic disasters are adjusted to short cantilever structures, thereby weakening the disturbance transmitted by the overlying rock.

[0026] b. By using directional long boreholes to construct hydraulic fracturing technology in gas-bearing strata, the permeability of coal seams can be increased, and the coal seams can be improved for permeability extraction to reduce the risk of gas outbursts;

[0027] c. By drilling long directional boreholes into the aquifer, drainage channels are provided to reduce stress concentration and water hazard risk in the aquifer;

[0028] d. By creating energy-absorbing weak structures in the deep coal seam through directional long boreholes, and simultaneously reinforcing the shallow roadway with auxiliary support technology, an internal support and external unloading structure is formed, providing energy-absorbing and pressure-relieving space and maintaining the roadway support system.

[0029] In the case of fracturing hard rock formations (a), it is required that the fracturing fractures in two adjacent boreholes be connected. This connection is characterized by observing an increase in water flow from adjacent boreholes during fracturing. For the first borehole, which has no adjacent boreholes for verification, fracture formation is characterized by changes in water pressure and flow rate, and fracture development is ensured by requiring continuous pressure supply for 20 minutes.

[0030] The completion standard for construction in gas-bearing strata (b) is: gas pressure < 0.74 MPa, gas content < 8 m³ / s. 3 / t, structural zone <6m 3 / t.

[0031] The borehole diameter for aquifer c is guaranteed to be 150mm.

[0032] The beneficial effects of the above-described technical solution of the present invention are as follows:

[0033] The above scheme can change the inclination and azimuth of the borehole without interrupting the drilling process, improve the permeability and desorption of gas-bearing or water-bearing strata to eliminate the risk of outbursts or water hazards, pre-fracture the hard roof to weaken the disturbance of overburden collapse, and create cavitation holes in deep coal bodies to form an internal support and external unloading energy absorption structure, thereby realizing multi-level, large-space continuous operation. It can reduce the degree of danger of various mine dynamic disasters through multiple means, and can simultaneously solve the problem of excessive pressure relief in some areas while regulating and relieving pressure on complex mine dynamic disasters at multiple levels. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the borehole layout for the mine dynamic disaster prevention method based on long boreholes according to the present invention;

[0035] Figure 2 This is a schematic diagram of the hydraulic fracturing structure control technology for thick, hard roof plates according to the present invention;

[0036] Figure 3 This is a schematic diagram of the permeability enhancement and desorption technology for gas-bearing or water-bearing strata of the present invention;

[0037] Figure 4 This is a schematic diagram of the internal support and external unloading structure adjustment of the present invention.

[0038] Among them: 1-Long borehole construction location; 2-Long borehole route; 3-Reinforcement support; 4-Energy-absorbing weak structure; 5-Volcanic cavity space; 6-Water-bearing strata; 7-Thick hard roof; 8-Gas-bearing strata; 9-Stress distribution curve of long cantilever structure; 10-Long cantilever structure; 11-Hydraulic fracturing fracture; 12-Stress distribution curve of short cantilever structure; 13-Short cantilever structure; 14-Drainage channel; 15-Hydraulic fracturing permeability enhancement technology for gas-bearing strata; 16-Gas drainage channel. Detailed Implementation

[0039] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0040] This invention provides a method for preventing and controlling dynamic disasters in mines based on long boreholes.

[0041] The method includes the following steps:

[0042] S1: Based on the dynamic events that have occurred in the mine and the risk assessment of each dynamic hazard, determine the type of complex dynamic hazard in the mine, identify the key influencing factors of the complex dynamic hazard and the areas that need to take pretreatment measures; combine the mine's production technology conditions and actual geological conditions, design a coal and rock structure control scheme, and determine the construction location, sequence, route and parameters of pretreatment methods for each spatial level of the continuous long borehole.

[0043] S2: Conduct directional long borehole construction according to the long borehole construction process determined in S1 to achieve the purpose of preventing mine dynamic disasters;

[0044] S3: After all the pretreatment work for all dynamic hazard influencing factors in a borehole is completed, the process is moved to the next borehole location and repeated until mining ends or the pretreatment work for dynamic hazard influencing factors in the mine is completed.

[0045] The S2 medium-length borehole construction includes:

[0046] a. By using directional long boreholes to construct hydraulic fracturing technology in hard rock strata, fractures are developed, the integrity of hard rock strata is destroyed, and long cantilever structures that are unfavorable to the prevention and control of dynamic disasters are adjusted to short cantilever structures, thereby weakening the disturbance transmitted by the overlying rock.

[0047] b. By using directional long boreholes to construct hydraulic fracturing technology in gas-bearing strata, the permeability of coal seams can be increased, and the coal seams can be improved for permeability extraction to reduce the risk of gas outbursts;

[0048] c. By drilling long directional boreholes into the aquifer, drainage channels are provided to reduce stress concentration and water hazard risk in the aquifer;

[0049] d. By creating energy-absorbing weak structures in the deep coal seam through directional long boreholes, and simultaneously reinforcing the shallow roadway with auxiliary support technology, an internal support and external unloading structure is formed, providing energy-absorbing and pressure-relieving space and maintaining the roadway support system.

[0050] The four construction methods mentioned above (a, b, c, and d) can be carried out individually or in combination at will. The specific construction sequence depends on whether the construction project is selected and the type of complex dynamic disaster in the mine.

[0051] The following section will explain the specific implementation process.

[0052] like Figure 1, Figure 2 , Figure 3 , Figure 4 As shown, the specific implementation steps are as follows:

[0053] S1: Based on the dynamic events that have occurred in the mine and the risk assessment of each dynamic hazard, determine the type of complex dynamic hazard in the mine, identify the key influencing factors of the complex dynamic hazard and the areas that need to take pretreatment measures; combine the mine's production technology conditions and actual geological conditions, design a coal and rock structure control scheme, and determine the parameters of the continuous long borehole construction location 1, sequence, long borehole route 2, and pretreatment methods for each spatial level;

[0054] Specifically, core drilling and mechanical parameter determination were performed on the thick, hard roof of the working face. The rock strata thickness exceeded 10m, and the uniaxial compressive strength was >60MPa, classifying it as a hard strata. Then, based on the mechanical parameter test results (according to the impact tendency identification standard), the roof was determined to be a strongly impact-prone roof, and the coal seam to be a weakly impact-prone coal seam. The main parameters of the roof were uniaxial tensile strength (4.99MPa) and bending energy index (U). WQS =136); the main parameters of the coal seam are uniaxial compressive strength (14.74 MPa), impact energy index (1.1), elastic energy index (4.198), and dynamic failure time (297 ms). This indicates that the coal seam and roof have the potential for rockburst, and are assessed as having a moderate rockburst hazard according to the rockburst hazard assessment process. Furthermore, based on the analogy between the initial and periodic rockburst processes during the mining of adjacent working faces, the rockburst step distance is considered relatively long, which has the potential to induce rockburst. Therefore, it is necessary to carry out long-bore hydraulic pressure drilling on the roof above the working face to reduce its disturbance to the mining face.

[0055] Furthermore, based on the preliminary geophysical exploration results of the working face, it was found that aquifers were developed in some of the roof areas, and it was necessary to dewater and depressurize the aquifers.

[0056] Furthermore, based on geological data, the original formation gas pressure (0.76 MPa), formation firmness coefficient (0.4), formation failure type (Ⅳ), and initial gas release velocity (10) were detected, and the formation was determined to be a formation with a risk of gas outburst, requiring long-bore hydraulic fracturing and permeability enhancement extraction.

[0057] Furthermore, the coal pillar is 25m wide and 6m thick. The coal pillar is located in the area affected by the peak lateral support pressure of the goaf, requiring the construction of energy-absorbing weak structures to prevent the occurrence of dynamic disasters.

[0058] S2: Hydraulic fracturing technology is used to construct hydraulic fractures 11 in the thick, hard roof slab 7 through directional long drilling, thereby disrupting the integrity of the thick, hard roof slab and changing the long cantilever structure 10, which is unfavorable for dynamic disaster prevention, into a short cantilever structure 13, thus weakening the disturbance of overburden transmission; among them, the stress distribution curves 9 and 12 of the long cantilever structure are as follows. Figure 2 As shown;

[0059] S3: By constructing hydraulic fracturing technology 15 for gas-bearing strata 8 through directional long boreholes, the permeability of the gas-bearing strata is increased to form a gas drainage channel 16, which is then used to enhance permeability and extract gas, thereby reducing the risk of gas outbursts.

[0060] S4: By drilling into the aquifer through directional long boreholes, a drainage channel 14 is provided for the aquifer 6, reducing the stress concentration layer and the risk of water damage in the aquifer;

[0061] S5: By creating a cavity space 5 in the deep coal seam through directional long drilling, an energy-absorbing weak structure 4 is formed. At the same time, the shallow construction and reinforcement support 3 technology of the roadway is used to form an internal support and external unloading structure. Under the influence of complex dynamic disasters, it can provide energy-absorbing and pressure-relieving space and maintain the roadway support system.

[0062] S6: After all the pretreatment work for all dynamic hazard influencing factors in a borehole is completed, the equipment will be moved to the next borehole location and the cycle will continue until mining is completed or the pretreatment work for the dynamic hazard influencing factors in the mine is completed.

[0063] Specifically, such as Figure 1 The geological conditions, from highest to lowest, are as follows: gas-bearing strata 8, hard rock strata (also known as thick, hard roof 7), water-bearing strata 6, and coal seam. Drilling begins in the roadway, and the drilling route is designed based on identified hazards, allowing space for pre-treatment measures below.

[0064] In this embodiment, directional hydraulic fracturing is used: uniaxial tensile strength 2.817MPa, maximum principal stress 18.1MPa, minimum principal stress 8.92MPa.

[0065] P=1.3(8.92+18.1)=35.13MPa.

[0066] p1=1.3(3σ3-σ1+R t (1)

[0067] p2=1.3(σ1+R t (2)

[0068] p1 -- Estimated start-up pressure for direct hydraulic fracturing (MPa)

[0069] p2 -- Estimated initiation pressure for directional hydraulic fracturing (MPa)

[0070] σ1 -- Maximum principal stress at the fracturing point (MPa)

[0071] σ3 -- Minimum principal stress at the fracturing point (MPa)

[0072] R t --Tensile strength of the rock strata at the fracturing point, (MPa)

[0073] ① First, drill holes into the gas-bearing strata to perform hydraulic fracturing to release the internal energy of the gas and to drain the gas. The water pressure is calculated based on the rock properties and geostress (as shown in Formulas 1 and 2 above). Generally, the borehole spacing is 10m. Hydraulic fracturing is carried out in the gas-bearing strata. For the first hole, the changes in water flow and water pressure are mainly observed to determine whether fracturing is complete. A sudden increase in flow and a sudden decrease in water pressure indicate that a fracture has been created. Maintain fracturing for 30 minutes. During this period, the increasing and decreasing trends in flow and water pressure indicate that fracturing is continuing. For other holes, while considering the changes in pressure and flow, observe the water output of adjacent holes. If the water output of a hole increases during fracturing, it indicates that the fracture between the two holes has been connected.

[0074] ② Retract the drill bit into the hard rock layer to perform hydraulic fracturing, with the same parameters as ①;

[0075] ③ The third layer that needs to be dealt with is the water-bearing stratum, because the borehole has already passed through this layer. During this period, the drainage of the water-bearing stratum is already underway. Ensuring a borehole spacing of 10m can guarantee the normal progress of the drainage.

[0076] ④ When constructing a weak energy-absorbing structure in a coal seam, the drill bit is a directional drill bit, which can repeatedly drill at the construction location to achieve the effect of creating a weak energy-absorbing structure, forming a surrounding rock state of internal support (strong support) and external unloading (pressure-relieving weak energy-absorbing structure).

[0077] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preventing and treating mine dynamic disasters based on long boreholes, characterized in that, The method comprises the following steps: S1: judging the type of the mine compound dynamic disaster according to the occurred dynamic events and the evaluation of the dynamic disaster risk of the mine, determining the key influencing factors of the compound dynamic disaster and the area needing to take pretreatment measures; combining the production technical conditions and the actual geological conditions of the mine, determining the construction position, sequence of the continuous long drill hole and the parameters of the pretreatment means of each spatial level; S2: performing the directional long drill hole construction according to the long drill hole construction process determined in S1, so as to achieve the purpose of preventing and treating the mine dynamic disaster; The construction of the long drill hole starts from the working face cut hole, and the drill holes are constructed in sequence according to the working face mining direction, and the construction is processed until the working face stop line, and then the construction of the working face is ended, and the equipment is transferred to the next working face for construction, and the drill hole needs to be constructed ahead of the working face; S3: after the construction of all the dynamic disaster influencing factors of a drill hole is completed, the next drill hole site is transferred, and the construction is circularly performed until the mining is completed or the pretreatment engineering of the mine dynamic disaster influencing factors is completed; The directional long drill hole construction in S2 comprises: a. developing fissures by the hydraulic fracturing technology of the directional long drill hole to hard rock strata, destroying the integrity of the hard rock strata, adjusting the long cantilever structure which is not conducive to the prevention and treatment of the dynamic disaster into a short cantilever structure, and weakening the disturbance transmitted by the overburden rock; b. increasing the coal seam permeability by the hydraulic fracturing technology of the directional long drill hole to the gas-containing strata, increasing the permeation extraction of the coal seam, and reducing the gas outburst risk; c. drilling the water-containing layer by the directional long drill hole, providing a hydrophobic channel of the water-containing layer, reducing the stress concentration degree of the water-containing layer and the water hazard risk; d. forming an energy-absorbing weak structure by the directional long drill hole to the deep part of the coal seam, and forming an internal support and external unloading structure by the supplemental support technology to the shallow part of the roadway, so as to provide an energy-absorbing and pressure-relieving space and maintain the support system of the roadway; In a, the fracturing of the hard rock strata requires that the fracturing fissures of two adjacent drill holes are connected, the increase of the water yield of the adjacent drill hole when one hole is fractured is observed to represent the connection of the fissures, the first drill hole is not verified by the adjacent drill hole, the fissure formation is represented by the change of the water pressure and the flow rate, and the fissure development is guaranteed by requiring the continuous pressure supply for 20 minutes; The construction completion standard of the gas-containing stratum in b is: gas pressure <0.74 MPa, and gas content is less than 8 m 3 / t, the tectonic belt <6 m 3 / t; In c, the drill hole diameter of the water-containing layer is 150 mm.

2. The long borehole-based mine dynamic disaster prevention method according to claim 1, characterized in that, The spatial levels in S1 comprise the gas-containing strata, the hard rock strata, the water-containing layer and the coal seam; and the key influencing factors are specifically: The key influencing factors of the hard rock strata comprise the rock strata thickness, the uniaxial compressive strength, the uniaxial tensile strength, the bending energy index, the initial caving step distance and the periodic caving step distance; The key influencing factors of the gas-containing strata comprise the original strata gas pressure, the strata firmness coefficient, the strata damage type and the strata gas diffusion initial velocity; The key influencing factors of the water-containing layer comprise the distribution position and the water content of the water-containing area; The key influencing factors of the coal seam comprise the uniaxial compressive strength, the dynamic damage time, the impact energy index, the elastic energy index, the coal seam inclination, the coal seam thickness and the coal pillar width.

3. The long borehole-based mine dynamic disaster prevention method according to claim 1, characterized in that, The mine production technical conditions in S1 comprise the time and space relationship with the goaf, the coal pillar setting, the floor coal thickness, the roof pressure, the stop line arrangement, the mining speed and the protective layer selection. The actual geological conditions include structure, ground stress distribution, buried depth and coal seam occurrence characteristics.

4. The long borehole-based mine dynamic disaster prevention method according to claim 1, characterized in that, The S1 long borehole construction position is determined according to the distribution level of each dynamic disaster, 5-10 m energy absorption weak structure space is reserved outside the anchoring area of the coal seam, the borehole route from the coal seam upward is designed according to the position of the top breaking, gas drainage and water drainage as needed; the route and depth of the borehole are recorded and fed back in real time through the GPS positioning system of the drill bit, the route is adjusted appropriately according to the trajectory of the drill bit, so as to ensure that the borehole passes through the predetermined position; The borehole is constructed from the roadway side of the coal seam to reach the final position of the predetermined route, and then it is processed in turn from top to bottom, the processing sequence is determined according to the distribution position of each mine dynamic disaster, and finally the energy absorption weak structure is constructed outside the anchoring area of the coal seam, and the drill bit is turned and repeatedly cut.

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