Method for preventing and treating separation water through water pumping and drainage of ground well group after coal seam mining

Abstract

The invention relates to the technical field of coal mine water prevention and control, in particular to a method for preventing and controlling separation water through water pumping and drainage of a ground well group after coal seam mining, which comprises the following steps of: constructing a pre-mining ground water pumping drill hole before mining of a working face, and pre-draining underground water of an overlying strata aquifer of a coal seam roof; when overlying strata of a coal seam roof after mining of a working face are basically stable in deformation, a plurality of ground large-diameter pump drainage well groups are sequentially and rapidly constructed in a goaf behind the working face in the direction from the ground to the coal seam, and each well group is provided with n pump drainage wells; the depth of the ground large-diameter pump drainage well is 30-40 m below the bottom boundary of the overlying strata separation layer accumulated water supply aquifer; by actively pumping and draining a replenishment water source in the overlying separation layer space of the coal seam, replenishment of underground water to separation layer accumulated water is reduced, the pressure of the separation layer accumulated water is reduced, and the separation layer space accumulated water is continuously and stably drained. According to the method, the large-diameter pumping drainage well group on the post-mining construction ground actively pumps and drains the separation bed to supply water sources, the underground water level is controlled, the defects of existing measures are avoided, and separation bed water disaster prevention and control are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of coal mine water prevention and control, and in particular to a method for preventing and controlling delamination water by pumping water from a surface well group after coal seam mining. Background Art

[0002] Delamination is a phenomenon of fracture and separation of layers caused by asynchronous bending and settlement of overburden during mining of coal seam roof. The resulting roof delamination water hazard is characterized by large instantaneous water volume, hidden signs of water inrush, and serious hazards, which has long restricted the safe and efficient mining of coal mines. Early prevention and control technologies mainly adopted underground diversion holes, underground drilling interception and other measures to achieve water hazard prevention and control by pre-draining water accumulated in the delamination layer. With the iteration of technology, patent CN106089296B proposed a ground direct drainage drilling method. This method is based on geological condition exploration, and pre-constructs ground drainage boreholes at the potential delamination water inrush location of the working face. During the mining period, the borehole is kept connected to the goaf through repeated drilling to pre-drain water accumulated in the delamination layer and destroy the airtightness of the delamination space, forming a technical evolution from underground drainage to ground prevention and control.

[0003] However, existing technologies still have significant drawbacks in practical applications. Due to the complex construction environment and the significant influence of rock formation stress, underground drilling generally faces difficulties in drilling and a high probability of collapse and blockage, which directly affects the drainage effect. Surface-through drainage boreholes are clearly not adaptable in special geological areas such as the Huanglong Jurassic Coalfield in Shaanxi Province. This area has a high level of strata, a thick stratum between the coal seam roof and the stratum water accumulation zone, and is primarily mudstone and sandy mudstone. Furthermore, post-mining roof overburden damage and severe surface deformation often lead to blockage of drainage boreholes, poor water flow channels, and difficulty in drilling through the borehole, making it difficult to ensure the effective drainage of stratum water. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above problems and propose a method for pumping water from a surface well group to prevent and control abscission water after coal seam mining. To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] A method for pumping water from a surface well group to prevent and control abscission water after coal seam mining comprises the following steps:

[0006] Step S1: constructing a pre-mining ground pumping borehole before mining at the working face to pre-drain groundwater from the overburden aquifer on the coal seam roof;

[0007] Step S2: When the deformation of the coal seam roof overburden is basically stable after the working face is mined, several large-diameter surface drainage well groups are quickly constructed in sequence from the ground to the coal seam in the goaf behind the working face, each well group has n drainage wells, and the number of wells n is ≥ 2;

[0008] Step S3: Deepen the large-diameter surface pumping well to 30-40 m below the bottom boundary of the overburden stratum water recharge aquifer;

[0009] Step S4: By actively pumping out the replenishment water source of the abscission space overlying the coal seam, the supply of groundwater to the abscission water is reduced, the abscission water pressure is lowered, and the abscission water space is continuously and stably drained.

[0010] Furthermore, in step S1, the position of the pre-mining ground pumping drill hole is determined according to the initial closure position of the overburden separation layer of the coal seam roof of the working face; the pre-mining ground pumping drill hole is completed and has the pumping conditions in place one month before the working face is mined.

[0011] Furthermore, in step S1, the diameter of the ground pumping borehole before mining is 22-35 cm, the final hole depth passes through the fracture zone of the coal seam roof, casing is installed in the upper stratum of the borehole to reinforce the hole wall, and a water filter pipe made of high-strength steel of N80 or above is installed in the aquifer section overlying the lower coal seam. The diameter of the upper borehole is larger than that of the lower borehole.

[0012] Furthermore, in step S2, the surface large-diameter pumping and drainage well group is constructed in sequence from the working face cut toward the stop production line, including the first surface large-diameter pumping and drainage well group, the second surface large-diameter pumping and drainage well group, ... the n-1th surface large-diameter pumping and drainage well group, the nth surface large-diameter pumping and drainage well group, where n is an integer greater than or equal to 1; the first surface large-diameter pumping and drainage well group is located in the pre-mining surface pumping drilling site, and the distance from the working face cut is 150-170m, and the distance between the n-1th surface large-diameter pumping and drainage well group and the nth surface large-diameter pumping and drainage well group is 380-400m.

[0013] Furthermore, in step S3, the construction node of the large-diameter surface drainage well is when the deformation of the coal seam roof overburden 150-170m after the working face is basically stable, and a drilling rig and matching well construction technology are used to quickly complete the well, and the well construction time is 10-15 days.

[0014] Furthermore, in step S3, the diameter of the large-diameter surface pumping and drainage wells is 45-60 cm, the well depth is 30-40 m below the bottom boundary of the aquifer recharged by the aquifer, and the spacing between the large-diameter surface pumping and drainage wells in each large-diameter surface pumping and drainage well group is 20-100 m.

[0015] Furthermore, a water-stop casing is installed on the well wall of the upper formation of the large-diameter ground pumping and drainage well, and a water filter pipe made of high-strength steel of N80 or above is installed on the well wall of the aquifer section overlying the lower coal seam. A water level monitoring system and a deep well submersible pump matching the water level and water volume of the aquifer are installed in the well. The deep well submersible pump is installed at a depth of 20m below the bottom boundary of the aquifer supplied by the stratum water.

[0016] Furthermore, the large-diameter surface pumping and drainage well group continuously pumps water and simultaneously monitors the groundwater level in the wells, controlling the dynamic water level in the wells to be 10 m below the bottom boundary of the aquifer recharged by the stratum water accumulation.

[0017] The advantages of the present invention are:

[0018] The present invention constructs a large-diameter ground pumping and drainage well group when the deformation of the overlying rock is basically stable after the working face is mined, and actively pumps out the supply water source of the stratum space overlying the coal seam, effectively avoiding the defects of stratum water prevention and control measures such as underground diversion holes, underground drilling interception and ground direct drainage drilling holes, such as complex underground working environment, greater difficulty in drilling construction, easy hole collapse and blockage, blocked drainage channels and difficulty in drilling. After the working face is mined, a large amount of pumps are concentratedly pumped out the supply water source of the stratum space, and the dynamic water level in the well is controlled below the bottom boundary of the replenishment aquifer, reducing the supply of groundwater to the stratum water, lowering the pressure of the stratum water and continuously and stably draining the stratum water space, thereby achieving the prevention and control of stratum water damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings constituting a part of this application are used to provide a further understanding of this application and make other features, purposes and advantages of this application more apparent. The drawings and descriptions of the exemplary embodiments of this application are used to explain this application and do not constitute an improper limitation on this application.

[0020] In the attached figure:

[0021] Figure 1 This is a plan view of the layout of the large-diameter ground pumping and drainage well group in this embodiment.

[0022] Figure 2 This is a schematic diagram of the cross-sectional structure of the first surface large-diameter pumping and drainage well group in this embodiment.

[0023] Figure 3 This is a schematic diagram of the structure of a large-diameter pumping and drainage well on the ground after mining at the working face in this embodiment.

[0024] Figure 4 This is a schematic diagram of the ground water pumping drilling structure before mining on the working face in this embodiment.

[0025] The symbols in the figure are:

[0026] a. Cutting eye on the working face; b. Stopping line; c. Return air chute; d. Belt chute; e. Ground pumping borehole before mining; f. Ground large-diameter pumping and drainage well; N. Ground large-diameter pumping and drainage well group; N1. First ground large-diameter pumping and drainage well group; N2. Second ground large-diameter pumping and drainage well group; N n-1 , n-1th surface large-diameter pumping and drainage well group; N n , the nth ground large-diameter pumping and drainage well group; A, caving zone; B, fracture zone; C, separation zone; D, bending zone; E, coal seam; 1, water-stopping material; 2, casing; 3, filter pipe. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0028] The present invention is described in detail and specifically below through specific examples to provide a better understanding of the present invention. However, the following examples do not limit the scope of protection of the present invention.

[0029] Example

[0030] A method for pumping water from a surface well group to prevent and control stratum water after coal seam mining. This method is mainly applicable to the prevention and control of high-level stratum water in the coal seam roof under fully-mechanized caving mining conditions in deep and thick coal seams under Cretaceous conglomerate aquifers. It includes the following steps:

[0031] Step S1: construct a pre-mining ground pumping borehole e before mining at the working face to pre-drain groundwater from the overburden aquifer on the coal seam roof;

[0032] Step S2: When the deformation of the coal seam roof overburden is basically stable after the working face is mined, several large-diameter surface drainage well groups are quickly constructed in sequence from the ground to the coal seam in the goaf behind the working face, each well group has n drainage wells, and the number of wells n is ≥ 2;

[0033] Step S3: Deepen the large-diameter surface pumping well f to 30-40 m below the bottom boundary of the overburden stratum water recharge aquifer;

[0034] Step S4: By actively pumping out the supply water source of the abscission space overlying the coal seam, the supply of groundwater to the abscission water is reduced, the abscission water pressure is lowered, and the abscission water is continuously and stably drained to prevent and control the abscission water disaster.

[0035] The initial closure position of the stratum can be calculated based on parameters such as the rock structure and rock properties of the overlying rock, the width of the coal mining face, and the burial depth of the coal seam. Combined with the judgment of the stratum development position of the coal mining face, the mechanical analysis of the stratum duration, and the analysis of the dynamic mechanism of the formation of the stratum water inrush channel, it is known that the initial closure position of the stratum is 300-350m away from the working face cut a, and the subsequent periodic breaking distance is 150-170m.

[0036] Furthermore, in step S1, the position of the pre-mining ground pumping borehole e is determined according to the initial closure position of the overburden separation layer of the coal seam roof of the working face; the pre-mining ground pumping borehole e is completed and has pumping conditions one month before the working face is mined.

[0037] Based on the initial closure position of the abscission layer, a pre-mining surface pumping borehole e was located 150-170 m from the working face cut a. This borehole was constructed to investigate the geological and hydrogeological conditions of the working face, pre-drain groundwater from the overburden aquifer in the coal seam roof, and maintain a low water level. The pre-mining surface pumping borehole e was completed and ready for pumping one month before the working face resumed production.

[0038] Furthermore, in step S1, the diameter of the pre-mining ground pumping borehole e is 22-35 cm, the final hole depth passes through the coal seam roof fracture zone B, a casing 2 is installed in the upper stratum of the borehole to reinforce the hole wall, and a water filter pipe 3 made of high-strength steel of N80 or above is installed in the aquifer section overlying the lower coal seam. The diameter of the upper borehole is larger than that of the lower borehole.

[0039] After the pre-mining surface pumping borehole is completed, a deep well submersible pump is installed in the well to pump water, and the groundwater level in the hole is monitored simultaneously. During this period, according to the deformation of the hole, the hole is drilled at appropriate times to ensure long-term water pumping. After the borehole is used, the entire hole is sealed with cement slurry.

[0040] Furthermore, in step S2, the surface large-diameter pumping and drainage well group N is constructed in sequence from the working face cut a to the stop production line b, including the first surface large-diameter pumping and drainage well group N1, the second surface large-diameter pumping and drainage well group N2,... the n-1th surface large-diameter pumping and drainage well group Nn-1, and the nth surface large-diameter pumping and drainage well group Nn, where n is an integer greater than or equal to 1; the first surface large-diameter pumping and drainage well group N1 is located in the pre-mining surface pumping borehole e drilling site, and the distance from the working face cut a is 150-170m, and the distance between the n-1th surface large-diameter pumping and drainage well group and the nth surface large-diameter pumping and drainage well group is 380-400m.

[0041] Affected by mining, the pumping radius of the large-diameter ground pumping and drainage well group N in the Cretaceous conglomerate aquifer overlying the coal seam after mining of the working face reaches more than 600m. The construction of the large-diameter ground pumping and drainage well f starts 150-170m after the working face is mined. During the construction period, the working face is calculated to advance 50m, that is, the spacing between the large-diameter ground pumping and drainage well group N is 380-400m.

[0042] After the working face begins mining, a large-diameter surface pumping well cluster N is established in advance, and drilling equipment is installed, based on the working face's advancement speed. The first large-diameter surface pumping well cluster N1 is located at the pre-mining surface pumping borehole e drilling site. Each well site is designed to accommodate the simultaneous construction of two pumping wells f.

[0043] There are n drainage wells f in each large-diameter drainage well group N on the ground, and the number of wells n≥2. The number of large-diameter drainage wells is determined based on the water-richness of the aquifer replenished by the stratum water and the control requirements for the water level drop of the drainage wells. Considering the influence of the deformation of the coal seam roof overburden after mining of the working face, each well group equipment uses one drainage well to ensure the stable and continuous drainage of groundwater in the aquifer and stratum water.

[0044] Furthermore, in step S3, the construction node of the large-diameter surface drainage well f is when the deformation of the coal seam roof overburden 150-170m after the working face is basically stable, and a drilling rig and matching well construction technology are used for rapid well construction, and the well construction time is 10-15 days.

[0045] The damage and deformation of the coal seam roof covering 150-170m after the working face is basically stable. This is the construction node of the large-diameter ground pumping and drainage well f. The construction of the first large-diameter ground pumping and drainage well group N1 lags 150m behind the working face. According to the geological conditions of the stratum after mining and the well completion period requirements of the working face, high-efficiency drilling equipment and well completion technology that match it are selected to quickly complete the well, and the well completion time is 10-15 days.

[0046] Furthermore, in step S3, the diameter of the large-diameter surface pumping and drainage well f is 45-60 cm, the well depth is 30-40 m below the bottom boundary of the aquifer recharged by the stratum water, and the spacing between the large-diameter surface pumping and drainage wells f in each large-diameter surface pumping and drainage well group N is 20-100 m.

[0047] The diameter and spacing of the large-diameter surface pumping and drainage wells f are based on comprehensive considerations of the drilling equipment capacity, well site space conditions and economic efficiency. The diameter of the large-diameter surface pumping and drainage wells f after mining is preferably in the range of 45-60 cm, and the well depth should be 30-40 m below the bottom boundary of the aquifer recharged by the aquifer. The spacing between the large-diameter pumping and drainage wells f in each surface large-diameter pumping and drainage well group N is 20-100 m.

[0048] Furthermore, affected by the deformation of the overburden after mining of the working face, in order to ensure the service life of the ground pumping and drainage well group N, a water-stop casing 2 is installed on the upper formation wall of the large-diameter ground pumping and drainage well f, and a water filter pipe 3 made of high-strength steel of N80 or above is installed on the wall of the aquifer section overlying the lower coal seam. A water level monitoring system and a deep well submersible pump matching the water level and water volume of the aquifer are installed in the well. The deep well submersible pump is installed at a depth of 20m below the bottom boundary of the aquifer supplied by the stratum water.

[0049] Furthermore, the large-diameter surface pumping and drainage well group N continuously pumps water and simultaneously observes the groundwater level in the wells, controlling the dynamic water level in the wells to be 10 m below the bottom boundary of the aquifer recharged by the stratum water accumulation.

[0050] After the construction of the large-diameter pumping and drainage well f on the ground is completed, the pumping and drainage operation is carried out immediately. The n pumping and drainage wells f are pumped and discharged simultaneously with large pumping capacity, forming a groundwater drop funnel with a large drop behind the working face, changing the groundwater runoff field of the coal seam roof overburden, reducing the groundwater recharge to the abscission layer water, reducing the abscission layer water pressure and continuously and stably draining the abscission layer space water, so as to achieve the prevention and control of abscission layer water hazards.

[0051] Large-diameter surface pumping and drainage wells (N) continuously pump water while simultaneously monitoring the groundwater level within the wells. The dynamic water level within the wells is controlled to be approximately 10 meters below the bottom boundary of the aquifer recharged by the aquifer's accumulation of water. Simultaneously, based on the pumping data, the hydrogeological parameters of the aquifer affected by coal seam mining at the working face are determined.

[0052] When the working face advances to 550m away from the first surface large-diameter pumping and drainage well group N1, construction of the second surface large-diameter pumping and drainage well group N2 begins 150-170m after the working face is mined. When the working face advances to 550m away from the second surface large-diameter pumping and drainage well group N2, construction of the third surface large-diameter pumping and drainage well group N3 begins, and so on, until the working face is mined.

[0053] After the utilization of each large-diameter ground pumping and drainage well group N is completed, the cement slurry is sealed or left as a long-term observation well for the dynamic groundwater level.

[0054] While the specific embodiments of the present invention have been described in detail above, they are merely exemplary, and the present invention is not equivalent to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions of the present invention are also within the scope of the present invention. Therefore, equivalent changes and modifications made without departing from the spirit and scope of the present invention are intended to be encompassed within the scope of the present invention.

Claims

1. A method for preventing and controlling stratum water by pumping water from a surface well group after coal seam mining, characterized in that: The following steps are involved: Step S1: constructing a pre-mining ground pumping borehole (e) before mining at the working face to pre-drain groundwater from the overburden aquifer in the coal seam roof; Step S2: When the deformation of the coal seam roof overburden is basically stable after the working face is mined, several large-diameter surface drainage well groups are quickly constructed in sequence from the ground to the coal seam in the goaf behind the working face, each well group has n drainage wells, and the number of wells n is ≥ 2; Step S3: The surface large-diameter pumping well (f) is deepened to 30-40 m below the bottom boundary of the overburden stratum water recharge aquifer; Step S4: By actively pumping out the replenishment water source of the abscission space overlying the coal seam, the supply of groundwater to the abscission water is reduced, the abscission water pressure is lowered, and the abscission water space is continuously and stably drained.

2. The method for preventing and controlling stratum water by pumping water from a surface well group after coal seam mining according to claim 1, characterized in that: In step S1, the position of the pre-mining ground pumping borehole (e) is determined according to the initial closure position of the overburden separation layer of the coal seam roof at the working face; the pre-mining ground pumping borehole (e) is completed and has pumping conditions one month before the working face is mined.

3. The method for preventing and controlling stratum water by pumping water from a surface well group after coal seam mining according to claim 2, characterized in that: In step S1, the diameter of the pre-mining ground pumping borehole (e) is 22-35 cm, the final hole depth passes through the coal seam roof fracture zone (B), a casing (2) is installed in the upper stratum of the borehole to reinforce the hole wall, and a water filter pipe (3) made of high-strength steel of N80 or above is installed in the aquifer section overlying the lower coal seam, and the diameter of the upper borehole is larger than that of the lower borehole.

4. The method for preventing and controlling stratum water by pumping water from a surface well group after coal seam mining according to claim 3, characterized in that: In step S2, the surface large-diameter pumping and drainage well group (N) is constructed in sequence from the working face cut hole (a) to the stop production line (b), including the first surface large-diameter pumping and drainage well group (N1), the second surface large-diameter pumping and drainage well group (N2), ... the n-1th surface large-diameter pumping and drainage well group (N n-1 ), nth surface large-diameter pumping well group (N n ), n is an integer greater than or equal to 1; the first surface large-diameter pumping and drainage well group (N1) is located in the pre-mining surface pumping drilling (e) drilling site, and is 150-170m away from the working face cut (a), and the distance between the n-1th surface large-diameter pumping and drainage well group and the nth surface large-diameter pumping and drainage well group is 380-400m.

5. The method for preventing and controlling stratum water by pumping water from a surface well group after coal seam mining according to claim 4, characterized in that: In step S3, the construction node of the large-diameter surface drainage well (f) is when the deformation of the coal seam roof overburden 150-170m after the working face is basically stable, and a drilling rig and matching well construction technology are used to quickly complete the well, and the well construction time is 10-15 days.

6. The method for preventing and controlling stratum water by pumping water from a surface well group after coal seam mining according to claim 5, characterized in that: In step S3, the diameter of the large-diameter surface pumping and drainage well (f) is 45-60 cm, the well depth is 30-40 m below the bottom boundary of the aquifer recharged by the aquifer, and the spacing between the large-diameter surface pumping and drainage wells (f) in each large-diameter surface pumping and drainage well group (N) is 20-100 m.

7. The method for preventing and controlling stratum water by pumping water from a surface well group after coal seam mining according to claim 6, characterized in that: A water-stop casing (2) is installed on the upper stratum wall of the large-diameter ground pumping and drainage well (f), and a water filter pipe (3) made of high-strength steel of N80 or above is installed on the wall of the aquifer section overlying the lower coal seam. A water level monitoring system and a deep well submersible pump that matches the water level and water volume of the aquifer are installed in the well. The deep well submersible pump is installed at a depth of 20m below the bottom boundary of the aquifer supplied by the stratum water.

8. The method for preventing and controlling stratum water by pumping water from a surface well group after coal seam mining according to claim 7, characterized in that: The surface large-diameter pumping and drainage well group (N) continuously pumps water and simultaneously observes the groundwater level in the wells, controlling the dynamic water level in the wells to be 10m below the bottom boundary of the aquifer supplied by the stratum water accumulation.

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