Water disaster prevention and control and water resource protection method for water-rich weathered bedrock aquifer

Abstract

According to the water disaster prevention and control and water resource protection method for the water-rich weathered bedrock aquifer, grouting is conducted on the first branch hole, the second branch hole and the third branch hole through a ground directional drilling method, and construction of a directional drilling entrapment type water interception curtain entrapped on a long-distance plane and continuous on a fracture surface is achieved; a coal seam working face or a treatment area is annularly surrounded through horizontal directional drilling to form a peripheral closed curtain, the mining influence and the stratum characteristics are considered, the reasonable distance between the water interception curtain and the coal seam working face is calculated, the effective protection distance is deduced, it is guaranteed that the roof weathered bedrock aquifer water interception curtain is not influenced by underlying coal seam mining, and the construction efficiency is improved. Safe and efficient operation of the water interception curtain is guaranteed, and the technical problem of water inrush threat in the coal seam mining process in the prior art is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of coal mine roof water disaster control, and relates to a method for water disaster prevention and control and water resource protection, in particular to a method for water disaster prevention and control and water resource protection of a water-rich weathered bedrock aquifer. Background Technique

[0002] The Quaternary loose layer and the weathered bedrock layer are the main water-rich aquifers in the coal seam roof in the northwest region of China. The Quaternary loose layer has a loose structure, large pores, strong water permeability, is easy to receive atmospheric precipitation recharge, has good storage conditions, and the occurrence of groundwater is strictly controlled by the ancient topography. Groundwater replenishes the underlying aquifer during lateral movement. The weathered bedrock aquifer is mainly replenished laterally. In some sections, the bedrock is exposed, the rock is weathered and broken, the pores and fissures are developed, and the condition for receiving precipitation recharge is good. The pores and fissures of the weathered bedrock are developed, forming a good water storage body, which is one of the main aquifers in the northwest region. The coal seams in the northwest region of China are shallowly buried. Coal seam mining often leads to the penetration of the overlying weathered bedrock aquifer. Therefore, a large amount of coal resources are overlaid by the weathered bedrock aquifer. When mining coal below it, it may cause the water in the water-rich aquifer to rush into the mine, posing a great threat to the safe production of coal mines. Therefore, coal mines often use inclined upward boreholes constructed underground to drain the water in the weathered bedrock aquifer. The construction of inclined upward boreholes destroys the integrity of the coal seam roof rock mass and increases the roof safety risk; the drained weathered bedrock water is mixed with other water in the mine and then enters the underground drain pipe and is collected in the underground central sump through the drainage pipeline, and is discharged from the central sump to the surface water treatment plant, and is used or discharged after reaching the standard. Draining the water-rich aquifer underground in the roof requires a large amount of costs for constructing inclined upward boreholes, underground pumping and drainage, and sewage treatment. At the same time, the clean weathered bedrock water is mixed with other water in the mine, resulting in pollution and requiring secondary treatment, increasing the mine drainage process, drainage costs and water treatment costs, and wasting precious underground water resources.

[0003] In order to effectively control and protect the water resources of the weathered bedrock aquifer in the mine roof, and achieve the goals of ensuring mine safety, reducing the mine drainage volume, and protecting the water resources of the roof weathered bedrock, it is urgent to develop a method for water disaster prevention and control and water resource protection of a water-rich weathered bedrock aquifer, so as to effectively prevent and control the water disaster of the water-rich weathered bedrock aquifer in the coal seam roof and efficiently protect the water resources, and ensure the green, safe and efficient production of coal mines. Summary of the Invention

[0004] Aiming at the deficiencies existing in the prior art, the present invention proposes a method for water disaster prevention and control and water resource protection of a water-rich weathered bedrock aquifer to solve the technical problem of water inrush threat during the process of coal seam mining in the prior art.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve:

[0006] A method for preventing and controlling water disasters and protecting water resources in a water-rich weathered bedrock aquifer, characterized in that the method specifically includes the following steps:

[0007] Step 1: According to the mining influence and stratum characteristics, calculate the spacing between the water cut-off curtain and the coal seam working face in the weathered bedrock aquifer, and determine the position of the water cut-off curtain line.

[0008] Step 2: Use ground equipment to measure the height of the weathered bedrock aquifer, and determine the positions of the first branch hole, the second branch hole, and the third branch hole according to the position of the water cut-off curtain line in Step 1 and the height of the weathered bedrock aquifer.

[0009] Step 3: According to the position of the first branch hole in Step 2, use a ground pneumatic rammer to ram the pipe obliquely into the weathered bedrock aquifer along the designed trajectory, and the rammed pipe section serves as the main hole.

[0010] Step 4: Set a directional drilling rig at the orifice of the rammed pipe on the ground in Step 3. The directional drilling rig constructs the first grouting section of the first branch hole along the position of the first branch hole of the rammed pipe in the weathered bedrock aquifer, and then withdraws the drill.

[0011] Step 5: First, perform grouting in the first grouting section of the first branch hole established in Step 4. After filling, close the pipe and wait for coagulation. Then, use the directional drilling rig to continue drilling along the rammed pipe and the first grouting section of the first branch hole after grouting to form the second grouting section of the first branch hole, withdraw the drill, fill it up, close the pipe and wait for coagulation. Repeat the operation of all grouting sections until the drilling and grouting of the first branch hole are completed.

[0012] Step 6: According to the position of the third branch hole in Step 2, the directional drilling rig constructs the first grouting section of the third branch hole along the position of the third branch hole of the rammed pipe in the weathered bedrock aquifer, and then withdraws the drill.

[0013] Step 7: Perform grouting in the first grouting section of the third branch hole established in Step 6. After filling, close the pipe and wait for coagulation. Then, use the directional drilling rig to continue drilling along the rammed pipe and the first grouting section of the third branch hole after grouting to form the second grouting section of the third branch hole, withdraw the drill, fill it up, close the pipe and wait for coagulation. Repeat the operation of all grouting sections until the drilling and grouting of the third branch hole are completed.

[0014] Step 8: According to the position of the second branch hole in Step 2, the directional drilling rig constructs the first grouting section of the second branch hole along the position of the second branch hole of the rammed pipe in the weathered bedrock aquifer, and then withdraws the drill.

[0015] Step 9: Grout within the first grouting section of the second branch hole established in Step 8. After filling it up, close the pipe and wait for setting. Then, use a directional drill to continue drilling along the ramming pipe and the first grouting section of the second branch hole after grouting to form the second grouting section of the second branch hole. Withdraw the drill, fill it up, close the pipe and wait for setting. Repeat the operations for all grouting sections until the drilling and grouting of the second branch hole are completed.

[0016] Step 10: Through the above steps, the grouted first branch hole, second branch hole, and third branch hole form a directional drill closed - type water - intercepting curtain that is closed in the plane and continuous in the cross - section.

[0017] The present invention also has the following technical features:

[0018] Step 1 is specifically realized through the following sub - steps:

[0019] Step 1.1: According to the mining influence and stratum characteristics, calculate the spacing S between the water - intercepting curtain in the weathered bedrock aquifer and the coal - seam working face, and determine the position of the water - intercepting curtain line.

[0020] Step 1.2: Analyze the influence of coal - seam mining on the roof strata. Coal - seam mining forms a caving zone and a water - conducting fissure zone above the coal seam. Coal - seam mining causes the roof strata to undergo mining - induced damage to form a mining - influence area, and the length of the mining - influence area is m.

[0021]

[0022] In the formula:

[0023] i is the rock - layer sequence at the top of the water - conducting fissure zone.

[0024] H i is the vertical distance from the top of the coal seam to the i - th layer of rock at the top of the water - conducting fissure zone, with the unit of m.

[0025] φ i is the movement angle of the i - th layer of rock at the top of the water - conducting fissure zone during coal - seam mining, with the unit of °.

[0026] Step 1.3: According to Step 1.1 and Step 1.2, obtain the safety distance △S between the water - intercepting curtain and the mining - influence area. △S is 5 - 10 meters.

[0027] Step 1.4: Determine the spacing S between the water - intercepting curtain in the weathered bedrock aquifer and the coal - seam working face according to Step 1.2 and Step 1.3.

[0028] Step 1.5: Determine the position of the water - intercepting curtain line according to the above steps.

[0029] In Step 2, according to the position of the water cutoff curtain line, it is determined that the first branch hole is located at the water cutoff curtain line; the second branch hole is located 10 meters to the right of the water cutoff curtain line; the third branch hole is located 10 meters to the left of the water cutoff curtain line.

[0030] In Step 2, the height of the weathered bedrock aquifer is measured as H by ground equipment. The vertical distance from the first branch hole to the top interface of the weathered bedrock aquifer is 1 / 6H; the vertical distance from the second branch hole to the bottom interface of the weathered bedrock aquifer is 1 / 6H; the vertical distance from the third branch hole to the first branch hole is 1 / 3H; the vertical distance from the third branch hole to the second branch hole is 1 / 3H.

[0031] In Step 3, the ramming pipe is rammed obliquely into the weathered bedrock aquifer along the designed trajectory at an angle between 10° and 30°; the diameter of the ramming pipe is between 273 mm and 820 mm, and grouting is carried out through the positive circulation method inside the pipe.

[0032] In Step 5, the radius and length of all grouting sections of the first branch hole are equal; in Step 7, the radius and length of all grouting sections of the third branch hole are equal; in Step 9, the radius and length of all grouting sections of the second branch hole are equal.

[0033] The radius and length of all grouting sections of the first branch hole, all grouting sections of the third branch hole, and all grouting sections of the second branch hole are equal.

[0034] The time for the closed pipe to wait for setting is 48 hours.

[0035] When there are through-going joints and fractures in the weathered bedrock aquifer where the grouting section is located:

[0036]

[0037] When there are no through-going joints and fractures in the weathered bedrock aquifer where the grouting section is located:

[0038]

[0039] In the formula:

[0040] R is the diffusion radius of the grout injection, with the unit of m.

[0041] r is the radius of the horizontal borehole, with the unit of m.

[0042] P 浆 is the grout injection pressure, with the unit of kPa.

[0043] P 水 is the water head pressure of the weathered bedrock, with the unit of kPa.

[0044] ρ 浆is the specific gravity of the slurry, with the unit of kg / m 3 .

[0045] h is the vertical buried depth of the grouting section, with the unit of m.

[0046] L is the length of the horizontal drilling grouting section, with the unit of m.

[0047] f 1 is the resistance coefficient between the slurry and the borehole wall, with the unit of kPa / m 2 .

[0048] f 2 is the resistance coefficient between the slurry and the formation fissures, with the unit of kPa / m 2 .

[0049] n is the fracture rate of the weathered bedrock. The porosity and fracture rate n of the weathered bedrock are 3% - 10%.

[0050] τ is the shear stress of the weathered bedrock, with the unit of kPa.

[0051] g is the acceleration due to gravity, with the unit of N / kg.

[0052] In Step Ten, the thickness of the water cutoff curtain is not less than twice the diffusion radius of the slurry grouting.

[0053] Compared with the prior art, the present invention has the following beneficial technical effects:

[0054] (Ⅰ) The method for preventing water disasters and protecting water resources in the water-rich weathered bedrock aquifer proposed by the present invention realizes the construction of a long-distance horizontal directional drilling closed water cutoff curtain through the method of surface directional drilling. The coal seam working face or the treatment area is surrounded by horizontal directional drilling to form a closed curtain around. Considering the mining influence and formation characteristics, the reasonable distance between the water cutoff curtain and the coal seam working face is calculated, and the effective protection distance is deduced, ensuring that the water cutoff curtain in the roof weathered bedrock aquifer is not affected by the mining of the underlying coal seam, and ensuring the safe and efficient operation of the water cutoff curtain, and solving the technical problem of water inrush threat during the coal seam mining process in the prior art.

[0055] (Ⅱ) The present invention has developed a horizontal hole progressive multiple repeated grouting method, determined the optimal grouting section length of the horizontal drilling grouting related to factors such as water pressure and formation shear stress, ensured the efficient and rapid construction of the water cutoff curtain by horizontal hole grouting, improved the construction efficiency, and greatly shortened the construction period.

[0056] (Ⅲ) The present invention has determined and calculated the position of the water cutoff curtain in the weathered bedrock aquifer, the horizontal and vertical distances of the directional holes, and deduced the calculation formula for the diffusion radius of the horizontal drilling grouting related to factors such as water pressure, slurry pressure, formation resistance, and formation shear stress, considering the influence of joints and fissures in the weathered bedrock.

[0057] (Ⅳ) The present invention realizes the advanced treatment of water in the weathered bedrock aquifer of the coal mine roof and the protection of water resources, revolutionizes the way of underground inclined downward drilling drainage, clean water landing, mixed pollution, treatment, and discharge of the water-rich aquifer in the roof, and greatly reduces the costs such as the electricity fee for roof drainage, water resources tax, and water treatment in the mine.

[0058] (Ⅴ) The present invention mainly uses a single or several surface drill sites to realize the whole process construction of drilling and grouting, with a small occupied area and a small area. Compared with the traditional vertical drilling grouting curtain, it reduces the land occupation by more than 90%, reduces unnecessary land acquisition, coordination, and vegetation damage, protects the vegetation and ecology at the construction site, improves the construction efficiency, and greatly shortens the construction period. Description of the Drawings

[0059] Figure 1 It is a schematic diagram of the connection of the overlying weathered bedrock aquifer for coal seam mining.

[0060] Figure 2 It is a schematic diagram of the water cut-off curtain in the weathered bedrock aquifer.

[0061] Figure 3 It is a schematic longitudinal section diagram of the layout of the directional drilling of the water cut-off curtain in the weathered bedrock aquifer.

[0062] Figure 4 It is a schematic plan view of the layout of the directional drilling of the water cut-off curtain in the weathered bedrock aquifer.

[0063] Figure 5 It is a schematic cross-section diagram of the layout of the directional drilling of the water cut-off curtain in the weathered bedrock aquifer.

[0064] Figure 6 It is a schematic diagram of the sectional grouting of the first-order directional drilling of the water cut-off curtain in the weathered bedrock aquifer.

[0065] Figure 7 It is a schematic diagram of the sectional grouting of the second-order directional drilling of the water cut-off curtain in the weathered bedrock aquifer.

[0066] Figure 8 It is a schematic diagram of the sectional grouting of the third-order directional drilling of the water cut-off curtain in the weathered bedrock aquifer.

[0067] Figure 9 It is a schematic diagram of the directional drilling closed water cut-off curtain in the weathered bedrock aquifer.

[0068] Figure 10 It is a schematic diagram of the water cut-off effect of the weathered bedrock aquifer.

[0069] The following further elaborates on the specific content of the present invention in conjunction with the embodiments. Detailed Implementation Modes

[0070] It should be noted that all mechanical equipment and components in the present invention, unless otherwise specified, are all mechanical equipment and components known in the prior art.

[0071] In compliance with the above technical solution, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent transformations made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0072] Embodiment:

[0073] This embodiment provides a method for preventing and controlling water disasters and protecting water resources in a water-rich weathered bedrock aquifer. As Figures 1 to 10 shown, the method specifically includes the following steps:

[0074] Step 1: According to the mining influence and formation characteristics, calculate the spacing between the water cutoff curtain in the weathered bedrock aquifer and the coal seam working face, and determine the position of the water cutoff curtain line.

[0075] Step 2: As Figure 2 and Figure 3 shown, use ground equipment to measure the height of the weathered bedrock aquifer, and determine the positions of the first branch hole, the second branch hole, and the third branch hole according to the position of the water cutoff curtain line in Step 1 and the height of the weathered bedrock aquifer.

[0076] Step 3: According to the position of the first branch hole in Step 2, use a ground pneumatic rammer to ram the pipe obliquely into the weathered bedrock aquifer along the designed trajectory, and the rammed pipe section serves as the main hole.

[0077] Step 4: As Figure 5 shown, set a directional drill at the orifice of the rammed pipe on the ground in Step 3. The directional drill constructs the first grouting section of the first branch hole along the position of the first branch hole of the rammed pipe in the weathered bedrock aquifer, and then withdraws the drill.

[0078] Step 5: As Figure 5 shown, first grout in the first grouting section of the first branch hole established in Step 4. After filling, close the pipe and wait for setting. Then use the directional drill to continue drilling along the rammed pipe and the first grouting section of the first branch hole after grouting to form the second grouting section of the first branch hole, withdraw the drill, fill it up, close the pipe and wait for setting, and repeat the operation of all grouting sections until the drilling and grouting of the first branch hole are completed.

[0079] Step 6: As Figure 6 shown, according to the position of the third branch hole in Step 2, the directional drill constructs the first grouting section of the third branch hole along the position of the third branch hole of the rammed pipe in the weathered bedrock aquifer, and then withdraws the drill.

[0080] Step 7: As Figure 6As shown, grouting is carried out in the first grouting section of the third branch hole established in Step Six. After filling, the pipe is closed and left to set. Then, the directional drill is used to continue drilling along the ramming pipe and the first grouting section of the third branch hole after grouting to form the second grouting section of the third branch hole. The drill is withdrawn, and after filling, the pipe is closed and left to set. The operation of all grouting sections is repeated until the drilling and grouting of the third branch hole are completed.

[0081] Step Eight, as Figure 7 shown, according to the position of the second branch hole in Step Two, the directional drill constructs and establishes the first grouting section of the second branch hole along the position of the ramming pipe in the weathered bedrock aquifer of the second branch hole, and then the drill is withdrawn.

[0082] Step Nine, as Figure 7 shown, grouting is carried out in the first grouting section of the second branch hole established in Step Eight. After filling, the pipe is closed and left to set. Then, the directional drill is used to continue drilling along the ramming pipe and the first grouting section of the second branch hole after grouting to form the second grouting section of the second branch hole. The drill is withdrawn, and after filling, the pipe is closed and left to set. The operation of all grouting sections is repeated until the drilling and grouting of the second branch hole are completed.

[0083] Step Ten, as Figure 8 and Figure 9 shown, through the above steps, the grouted first branch hole, second branch hole, and third branch hole form a directional drill closed - type water - intercepting curtain that is closed in the plane and continuous in the cross - section.

[0084] Specifically in this embodiment, as Figure 1 shown, the roof rock layer above the coal seam is mudstone and sandstone. The roof rock layer serves as an aquitard. Above the roof rock layer is the weathered bedrock aquifer, which is the main aquifer above the coal seam. Above the weathered bedrock aquifer is the loose layer, and above the loose layer is the sand layer. Step One is specifically realized through the following sub - steps:

[0085] Step 1.1, according to the mining influence and stratum characteristics, calculate the distance S between the water - intercepting curtain in the weathered bedrock aquifer and the coal - seam working face, and determine the position of the water - intercepting curtain line.

[0086] Step 1.2, analyze the influence of coal - seam mining on the roof rock layer. Coal - seam mining forms a caving zone and a water - conducting fissure zone above the coal seam. Coal - seam mining causes the roof rock layer to undergo mining - induced damage to form a mining - influence area, and the length of the mining - influence area is m.

[0087]

[0088] In the formula:

[0089] i is the rock - layer sequence at the top of the water - conducting fissure zone.

[0090] H iIt is the vertical distance from the top of the coal seam to the i-th rock stratum at the top of the water-conducting fissure zone, with the unit of m.

[0091] φ i It is the movement angle of the i-th rock stratum at the top of the water-conducting fissure zone during the mining process of the coal seam, with the unit of °.

[0092] Step 1.3: According to Step 1.1 and Step 1.2, obtain the safety distance △S between the water cutoff curtain and the mining influence area. △S is 5 to 10 meters.

[0093] Step 1.4: Determine the spacing S between the water cutoff curtain and the coal seam working face in the weathered bedrock aquifer according to Step 1.2 and Step 1.3.

[0094] Step 1.5: Determine the position of the water cutoff curtain line according to the above steps.

[0095] Specifically in this embodiment, as Figure 4 shown, in Step 2, according to the position of the water cutoff curtain, determine that the first branch hole is located at the water cutoff curtain line; the second branch hole is located 10 meters to the right of the water cutoff curtain line; the third branch hole is located 10 meters to the left of the water cutoff curtain line.

[0096] Specifically in this embodiment, as Figure 2 shown, in Step 2, use the ground equipment to measure the height of the weathered bedrock aquifer as H. The vertical distance from the first branch hole to the top interface of the weathered bedrock aquifer is 1 / 6H; the vertical distance from the second branch hole to the bottom interface of the weathered bedrock aquifer is 1 / 6H; the vertical distance from the third branch hole to the first branch hole is 1 / 3H; the vertical distance from the third branch hole to the second branch hole is 1 / 3H.

[0097] Specifically in this embodiment, in Step 3, the angle at which the ramming pipe is obliquely rammed into the weathered bedrock aquifer along the designed trajectory is between 10° and 30°; the diameter of the ramming pipe is between 273 mm and 820 mm. The cement slurry is injected into the hole by the positive circulation method inside the pipe, and returns at the orifice of the ramming pipe on the ground. The cement slurry consolidates the ramming pipe and the formation into one body, facilitating subsequent grouting.

[0098] Specifically in this embodiment, as Figures 5 to 7 shown, in Step 5, the radii and lengths of all grouting sections of the first branch hole are equal; in Step 7, the radii and lengths of all grouting sections of the third branch hole are equal; in Step 9, the radii and lengths of all grouting sections of the second branch hole are equal.

[0099] Specifically in this embodiment, as Figures 5 to 7 shown, the radii and lengths of all grouting sections of the first branch hole, all grouting sections of the third branch hole, and all grouting sections of the second branch hole are equal.

[0100] Specifically, in this embodiment, the time for the closed - tube waiting for coagulation is 48 hours.

[0101] Specifically, in this embodiment, when there are penetrating joints and fissures in the weathered bedrock aquifer where the grouting section is located:

[0102]

[0103] When there are no penetrating joints and fissures in the weathered bedrock aquifer where the grouting section is located:

[0104]

[0105] In the formula:

[0106] R is the diffusion radius of the grout, and the unit is m.

[0107] r is the radius of the horizontal borehole, and the unit is m.

[0108] P 浆 is the grouting pressure of the grout, and the unit is kPa.

[0109] P 水 is the water - head pressure of the weathered bedrock, and the unit is kPa.

[0110] ρ 浆 is the specific gravity of the grout, and the unit is kg / m 3 .

[0111] h is the vertical buried depth of the grouting section, and the unit is m.

[0112] L is the length of the horizontal borehole grouting section, and the unit is m.

[0113] f 1 is the resistance coefficient between the grout and the borehole wall, and the unit is kPa / m 2 .

[0114] f 2 is the resistance coefficient between the grout and the formation fissures, and the unit is kPa / m 2 .

[0115] n is the fracture rate of the weathered bedrock, and the porosity - fracture rate n of the weathered bedrock is 3% - 10%.

[0116] τ is the shear stress of the weathered bedrock, and the unit is kPa.

[0117] g is the acceleration of gravity, and the unit is N / kg.

[0118] Specifically, in this embodiment, in step ten, the thickness of the water - cut-off curtain is not less than twice the diffusion radius of the grout injection.

[0119] Specifically, in this embodiment, as Figure 9 shown, directional boreholes are successively constructed along the position of the water cutoff curtain around the coal seam working face in the weathered bedrock aquifer to construct the water cutoff curtain in the weathered bedrock aquifer, and finally a closed directional drill water cutoff curtain that is closed on the plane and continuous in the cross section is formed. As Figure 10 shown, the closed directional drill water cutoff curtain in the weathered bedrock aquifer effectively blocks the lateral recharge of the water in the outer aquifer to the coal seam working face and the goaf inside the water cutoff curtain, reduces the water inflow from the roof during the coal seam working face mining process, and at the same time protects the weathered bedrock aquifer outside the coal seam working face, realizing safe, efficient and green coal mining.

Claims

1. A method for preventing and controlling water hazards and protecting water resources in a water-rich weathered bedrock aquifer, characterized in that: The method specifically comprises the following steps: Step 1: Calculate the distance between the cut-off curtain and the coal seam working face in the weathered bedrock aquifer according to the mining impact and formation characteristics, and determine the position of the cut-off curtain line; Step 2: Use ground equipment to measure the height of the weathered bedrock aquifer, and determine the positions of the first branch hole, the second branch hole, and the third branch hole according to the position of the water cut-off curtain line in step 1 and the height of the weathered bedrock aquifer; Step 3: According to the position of the first branch hole in step 2, a ground pneumatic rammer is used to ram the ramming pipe obliquely into the weathered bedrock aquifer along the designed trajectory, and the ramming pipe section is used as the main hole; Step 4: setting a directional drill at the rammed pipe hole located on the ground in step 3, constructing a first grouting section of the first branch hole along the rammed pipe at the position of the first branch hole in the weathered bedrock aquifer, and withdrawing the drill; Step 5: First, grouting is performed in the first grouting section of the first branch hole established in step 4, and after the grouting is full, the pipe is closed and solidified, and then a directional drill is used to continue drilling along the ramming pipe and the first grouting section of the first branch hole after grouting to form a second grouting section of the first branch hole, and the drill is withdrawn. After the grouting is full, the pipe is closed and solidified, and the operation of completing all grouting sections is repeated until the drilling and grouting of the first branch hole are completed; Step 6, according to the position of the third branch hole in step 2, the directional drill constructs a first grouting section of the third branch hole along the ramming pipe at the position of the third branch hole in the weathered bedrock aquifer, and withdraws the drill; Step 7, grouting is performed in the first grouting section of the third branch hole established in step 6, and after being filled, the pipe is closed and solidified, and then a directional drill is used to continue drilling along the rammed pipe and the first grouting section of the third branch hole after grouting to form a second grouting section of the third branch hole, and the drill is withdrawn, and after being filled, the pipe is closed and solidified, and the operation of completing all grouting sections is repeated until the drilling and grouting of the third branch hole are completed; Step eight, according to the position of the second branch hole in step two, the directional drill constructs a first grouting section of the second branch hole along the ramming pipe at the position of the second branch hole in the weathered bedrock aquifer, and withdraws the drill; Step nine, grouting is performed in the first grouting section of the second branch hole established in step eight, and after being filled, the pipe is closed and solidified, and then a directional drill is used to continue drilling along the ramming pipe and the first grouting section of the second branch hole after grouting to form a second grouting section of the second branch hole, and the drill is withdrawn, and after being filled, the pipe is closed and solidified, and the operation of completing all grouting sections is repeated until the drilling and grouting of the second branch hole are completed; Step ten, through the above steps, the first branch hole, the second branch hole and the third branch hole after grouting form a directional drilling closed water-cutting curtain that is closed on the plane and continuous on the cross section.

2. The method for preventing and controlling water hazards and protecting water resources in a water-rich weathered bedrock aquifer according to claim 1, characterized in that: Step 1 is implemented through the following sub-steps: Step 1.1, according to the mining impact and formation characteristics, calculate the distance S between the cut-off curtain and the coal seam working face in the weathered bedrock aquifer, and determine the position of the cut-off curtain line; Step 1.2, analyze the impact of coal seam mining on the roof rock layer. Coal seam mining forms a collapse zone and a water-conducting fracture zone above the coal seam. Coal seam mining causes mining damage to the roof rock layer to form a mining-affected zone. The length of the mining-affected zone is m. Where: i is the rock sequence at the top of the water-conducting fracture zone; H i is the vertical distance from the top of the coal seam to the top of the water-conducting fracture zone, in meters; φ i is the movement angle of the i-th rock layer at the top of the water-conducting fracture zone during coal mining, in degrees; Step 1.3, according to step 1.1 and step 1.2, the safe distance △S between the water cut-off curtain and the mining impact zone is obtained, and △S is 5 to 10 meters; Step 1.4, determine the distance S between the cut-off curtain and the coal seam working face in the weathered bedrock aquifer according to steps 1.2 and 1.3, Step 1.5, according to the above steps, determine the position of the water cut-off curtain line.

3. The method for preventing and controlling water hazards and protecting water resources in a water-rich weathered bedrock aquifer as claimed in claims 1 and 2, characterized in that: In step 2, according to the position of the water-cutting curtain line, determine that the first branch hole is located at the water-cutting curtain line; the second branch hole is located 10 meters to the right of the water-cutting curtain line; and the third branch hole is located 10 meters to the left of the water-cutting curtain line.

4. The method for preventing and controlling water hazards and protecting water resources in a water-rich weathered bedrock aquifer as claimed in claims 1 and 2, characterized in that: In step 2, the height of the weathered bedrock aquifer is measured by ground equipment as H, the vertical distance between the first branch hole and the top interface of the weathered bedrock aquifer is 1 / 6H; the vertical distance between the second branch hole and the bottom interface of the weathered bedrock aquifer is 1 / 6H; the vertical distance between the third branch hole and the first branch hole is 1 / 3H; the vertical distance between the third branch hole and the second branch hole is 1 / 3H.

5. The method for preventing and controlling water hazards and protecting water resources in a water-rich weathered bedrock aquifer according to claim 1, characterized in that: In step three, the ramming pipe is rammed obliquely into the weathered bedrock aquifer along the designed trajectory at an angle between 10° and 30°; the diameter of the ramming pipe is between 273mm and 820mm, and the ramming pipe is grouted by a positive circulation method inside the pipe.

6. The method for preventing and controlling water hazards and protecting water resources in a water-rich weathered bedrock aquifer according to claim 1, characterized in that: In step five, the radius and length of all grouting sections of the first branch hole are equal; in step seven, the radius and length of all grouting sections of the third branch hole are equal; in step nine, the radius and length of all grouting sections of the second branch hole are equal.

7. The method for preventing and controlling water hazards and protecting water resources in a water-rich weathered bedrock aquifer according to claim 6, characterized in that: The radius and length of all grouting sections of the first branch hole, all grouting sections of the third branch hole, and all grouting sections of the second branch hole are equal.

8. The method for preventing and controlling water hazards and protecting water resources in a water-rich weathered bedrock aquifer according to claim 1, characterized in that: The closed-tube waiting time is 48 hours.

9. The method for preventing and controlling water hazards and protecting water resources in a water-rich weathered bedrock aquifer according to claim 1, characterized in that: When there are through joints and fissures in the weathered bedrock aquifer where the grouting section is located: When there are no through joints or fissures in the weathered bedrock aquifer where the grouting section is located: Where: R is the grouting diffusion radius, in m; r is the horizontal drilling radius, in m; P 浆 is the grouting pressure of slurry, in kPa; P 水 is the head pressure of weathered bedrock, in kPa; ρ 浆 is the specific gravity of the slurry, in kg / m 3 ; h is the vertical depth of the grouting section, in meters; L is the length of the horizontal drilling grouting section, in meters; f1 is the resistance coefficient between the slurry and the borehole wall, in kPa / m 2 ; f2 is the resistance coefficient between slurry and formation fractures, in kPa / m 2 ; n is the crack ratio of weathered bedrock, and the porosity and crack ratio of weathered bedrock n is 3% to 10%; τ is the shear stress of weathered bedrock, in kPa; g is the acceleration due to gravity, and its unit is N / kg.

10. The method for preventing and controlling water hazards and protecting water resources in a water-rich weathered bedrock aquifer according to claim 1, characterized in that: In step ten, the thickness of the water-cutting curtain is not less than twice the diffusion radius of the slurry grouting.

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