Roof water drainage method for preventing weakening of coal seam immediate roof weakly-cemented mudstone when encountering water
Through dual-stage drilling technology and grouting solid pipe technology, the problem of weak cemented mudstone at the top of the coal seam is weakened, the construction difficulty and cost are reduced, the coal mine production is ensured, and the mud, sand and water mixture is collapsed.
Patent Information
- Application Number
- CN202411520121.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-29
- Publication Date
- 2024-12-13
AI Technical Summary
The weakly cemented mudstone in the coal seam is prone to expand and disintegrate when exposed to water, causing the mud, sand and water mixture to collapse into the mining space, affecting the safety of coal mines. Moreover, the existing roof water discharging method is difficult and costly, and poses safety hazards.
Using double-stage drilling technology, first install a first-stage water stop casing in the first-stage drilling hole, and drill holes into the mudstone in it. Then extend the flower casing in the second-stage drilling hole, and introduce the sandstone through the second-stage solid casing. Water is used to prevent water from flowing into the coal seam, and use grouting and solid pipe technology to seal the orifices to ensure that water does not enter again.
Effectively prevent the weak cemented mudstone from directly over the coal seam from weakening when exposed to water, reduce construction difficulty and cost, improve the safety of coal mines, avoid the collapse of mud, sand and water mixture, and improve construction safety.
Smart Images
Figure CN119122608A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of mine water hazard prevention and control methods, and specifically relates to a roof drainage method for preventing weakly cemented mudstone directly on the top of a coal seam from being weakened by water. Background Art
[0002] The direct roof of the Jurassic coal seam is generally a weakly cemented mudstone layer, which has a small internal cohesive force, weak interlayer bonding force, poor stability, and is easy to swell and disintegrate when exposed to water. When the roof is drained in the underground tunnel, the water from the sandstone aquifer on the roof flows into the weakly cemented mudstone layer on the direct roof of the coal seam along the drainage borehole, causing the mudstone layer to weaken when exposed to water, swell and disintegrate, and form a mud-sand-water mixture that breaks into the mining space, affecting the safe production of the coal mine. Due to the different thicknesses of the weakly cemented mudstone layer on the roof of the coal seam in different regions, the thickness of the weakly cemented mudstone on the roof of the coal seam in some regions is greater than 50m. At present, if the construction length of the water stop casing at the borehole mouth is too long during roof drainage, it will lead to high construction difficulty and high cost, and there are also certain safety issues. Therefore, it is necessary to study a method for preventing the weakly cemented mudstone on the direct roof of the coal seam from being weakened by water with low construction difficulty and low cost, so as to avoid the weakly cemented mudstone on the direct roof of the coal seam being weakened by the water from the sandstone aquifer on the roof, thereby affecting the safe production of the coal mine. Summary of the invention
[0003] The purpose of the present invention is to provide a roof drainage method to prevent the weakly cemented mudstone at the direct roof of the coal seam from being weakened by water, thereby solving the problem that the weakly cemented mudstone at the direct roof of the coal seam is weakened by the water from the roof sandstone aquifer.
[0004] The technical solution adopted by the present invention is: a method for draining water from the roof to prevent the weakly cemented mudstone directly on the top of the coal seam from being weakened by water, comprising the following steps: Step 1: determine the opening position, inclination and azimuth of the drainage borehole, and at the same time determine the thickness of the coal seam above the opening position and the thickness of the weakly cemented mudstone directly on the top of the coal seam; Step 2, determine the length of the primary water stop casing and the corresponding primary borehole depth, and determine the length of the secondary casing and the corresponding secondary borehole depth according to the borehole inclination, coal seam thickness and mudstone thickness; Step 3, constructing a primary borehole in the coal seam according to the borehole azimuth, inserting a primary water-stopping casing into the primary borehole, and injecting grouting to fix the pipe in the annulus between the primary water-stopping casing and the primary borehole; Step 4, construct a secondary borehole into the mudstone in the primary water-stop casing and drill into the sandstone, connect the secondary flower casing to the upper end of the secondary solid casing and lower it into the secondary borehole through the primary water-stop casing, so that the secondary solid casing extends to the mudstone top plate, and then grouting is performed in the annulus between the secondary solid casing, the secondary borehole and the primary water-stop casing to fix the pipe.
[0005] The present invention is also characterized in that: A Ф133mm drill bit is used for the first-level drilling and a Ф89mm drill bit is used for the second-level drilling.
[0006] The first-level water-stop casing has an outer diameter of 108mm and a wall thickness of 6.5mm. The second-level solid casing and the second-level flower casing both have an outer diameter of 63mm and a wall thickness of 5.5mm.
[0007] The secondary flower casing is a casing with side walls covered with holes.
[0008] In step 4, before constructing the secondary drilling hole, a gate valve is first connected to the bottom end of the primary water-stop casing. After the secondary drilling hole is completed, the gate valve is removed, and the secondary flower casing and the secondary solid casing are lowered and then the gate valve is connected to the bottom end of the primary water-stop casing. After that, grouting is performed in the annulus between the secondary solid casing, the secondary drilling hole and the primary water-stop casing to fix the pipe.
[0009] The grouting and pipe fixing in step 4 is sealed by double-liquid grouting or cement slurry. After the grouting is completed and the grouting is stopped, the grouting is waited for to solidify.
[0010] The beneficial effects of the present invention are as follows: the roof drainage method for preventing the weakly cemented mudstone at the direct top of the coal seam from being weakened by water according to the present invention, after the secondary borehole of the drainage drilling process is drilled, a secondary solid casing is installed from the coal seam hole opening position, the length of the secondary solid casing is not less than the distance from the coal seam hole opening position to the roof of the weakly cemented mudstone at the direct top of the coal seam, and grouting is performed on the annular space between the secondary solid casing and the wall of the secondary borehole, thereby solving the problem that the underground roof drainage drilling hole is constructed under the condition of the weakly cemented mudstone at the direct top of the coal seam, resulting in the sandstone water of the roof aquifer flowing along the borehole into the weakly cemented mudstone at the direct top of the coal seam, causing the weakly cemented mudstone at the direct top of the coal seam to be weakened by water, expand and disintegrate, and form a mud-sand-water mixture that breaks into the mining space and affects the safe production of the coal mine. BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Figure 1 It is a schematic diagram of the working state of the roof drainage method of the present invention for preventing the weakly cemented mudstone directly at the top of the coal seam from being weakened by water.
[0012] In the figure, 1. first-level water-stop casing, 2. first-level borehole, 3. second-level solid casing, 4. second-level borehole, 5. second-level flower casing, 6. flange, 7. gate valve. DETAILED DESCRIPTION
[0013] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.
[0014] Example 1 The present invention provides a roof drainage method for preventing the weakly cemented mudstone directly at the top of the coal seam from being weakened by water, such as Figure 1 As shown, the following steps are included: Step 1: Determine the location, inclination and azimuth of the drainage borehole, and at the same time determine the thickness of the coal seam above the hole location and the thickness of the weakly cemented mudstone directly on the top of the coal seam.
[0015] Step 2: Determine the length of the first-level water-stop casing 1 and the corresponding depth of the first-level borehole 2 according to the corresponding requirements of the Technical Specifications for Underground Water Exploration and Release; determine the length of the second-level casing 3 and the corresponding depth of the second-level borehole 4 according to the borehole inclination, coal seam thickness and mudstone thickness.
[0016] Step 3: construct a primary borehole 2 in the coal seam according to the drilling azimuth, insert a primary water-stop casing 1 into the primary borehole 2, and inject grouting into the annulus between the primary water-stop casing 1 and the primary borehole 2 to fix the pipe.
[0017] Step 4, construct a secondary borehole 4 towards the mudstone in the primary water-stop casing 1 and drill into the sandstone, connect the secondary flower casing 5 to the upper end of the secondary solid casing 3 and lower it into the secondary borehole 4 through the primary water-stop casing 1, so that the secondary solid casing 3 extends to the mudstone top plate, and then grouting is performed in the annulus between the secondary solid casing 3, the secondary borehole 4 and the primary water-stop casing 1 to fix the pipe.
[0018] Through the above manner, the roof drainage method of the present invention for preventing the weakly cemented mudstone at the direct top of the coal seam from being weakened by water, when draining water, the sandstone water enters the interior through the holes on the secondary flower casing 5, and is downwardly discharged along the inner wall of the secondary solid casing 3, thereby solving the problem that the underground roof drainage drilling hole is constructed under the condition of the weakly cemented mudstone at the direct top of the coal seam, resulting in the sandstone water of the roof aquifer flowing along the borehole into the weakly cemented mudstone at the direct top of the coal seam, causing the weakly cemented mudstone at the direct top of the coal seam to be weakened by water, expand, and disintegrate, forming a mud-sand-water mixture that breaks into the mining space and affects the safe production of the coal mine.
[0019] Example 2 The present invention provides a roof drainage method for preventing the weakly cemented mudstone directly at the top of the coal seam from being weakened by water, such as Figure 1 As shown, the following steps are included: Step 1: According to the geological and hydrogeological conditions of the mine, the spatial distribution of the aquifer and impermeable layer in the tunnel and coal seam roof is obtained, and the drilling position, inclination, azimuth and other drilling parameters of the drainage borehole are determined; according to the spatial relationship between the tunnel and the coal seam, the thickness of the coal seam above the opening position and the thickness of the weakly cemented mudstone on the direct roof of the coal seam are determined.
[0020] Step 2, according to the corresponding requirements of the "Technical Specifications for Underground Water Exploration and Release", determine the length of the first-level water-stop casing 1 and the corresponding first-level borehole 2 depth in the coal seam, and convert the length of the second-level solid casing 3 and the corresponding second-level borehole 4 depth according to the borehole inclination, coal seam thickness and mudstone thickness; wherein, after the length of the first-level water-stop casing 1 is obtained according to the corresponding requirements of the "Technical Specifications for Underground Water Exploration and Release", the depth of the first-level borehole 2 is roughly equivalent to the length of the first-level water-stop casing 1, and when constructing the first-level borehole 2, it can exceed the design length of the first-level water-stop casing 1 by about 0.5m to leave a margin; the length of the second-level solid casing 3 can be converted from the total thickness of the coal seam and mudstone and the borehole inclination. Since the second-level solid casing 3 is partially inside the first-level water-stop casing 1, the depth of the second-level borehole 4 located in the mudstone layer can be obtained by subtracting the length of the first-level water-stop casing 1 from the second-level solid casing 3. Finally, the depth of the second-level borehole 4 drilled upward into the sandstone layer ensures that the upper end of the second-level solid casing 3 can be connected to the second-level flower casing 5 and can extend to the mudstone roof.
[0021] Step 3, according to the drilling azimuth, use Ф133mm drill bit to construct the first-level borehole 2 in the coal seam, insert the first-level water-stop casing 1 with an outer diameter of 108mm and a wall thickness of 6.5mm into the first-level borehole 2, and inject grout into the annulus between the first-level water-stop casing 1 and the first-level borehole 2 to fix the pipe. After fixing the pipe, sweep the hole to the bottom of the hole and conduct a pressure test until it passes.
[0022] Step 4, connect the gate valve 7 through the flange 6 at the bottom of the primary water-stop casing 1 to prevent a large amount of water from suddenly gushing out of the roof during subsequent drilling, use a Ф89mm drill bit in the primary water-stop casing 1 to construct the secondary borehole 4 towards the mudstone and drill into the sandstone, remove the gate valve 7 after the construction of the secondary borehole 4 is completed, connect the secondary flower casing 5 with the same inner and outer diameter and side wall covered with holes to the upper end of the secondary solid casing 3 with an outer diameter of 63mm*wall thickness of 5.5mm and lower it into the secondary borehole 4 through the primary water-stop casing 1, and then connect the gate valve 7 through the flange 6 at the bottom of the primary water-stop casing 1, and then grout the pipe in the annulus between the secondary solid casing 3, the secondary borehole 4 and the primary water-stop casing 1. The grouting pipe is sealed by double-liquid grouting. Stop grouting after the slurry is reversed from the secondary solid casing 3, and wait for the slurry to solidify. The solidification time shall not be less than 4 hours.
[0023] Example 3 The present invention provides a roof drainage method for preventing the weakly cemented mudstone directly at the top of the coal seam from being weakened by water, such as Figure 1 As shown, the following steps are included: Step 1: According to the geological and hydrogeological conditions of the mine, the spatial distribution of the aquifer and impermeable layer in the tunnel and coal seam roof is obtained, and the drilling position, inclination, azimuth and other drilling parameters of the drainage borehole are determined; according to the spatial relationship between the tunnel and the coal seam, the thickness of the coal seam above the opening position and the thickness of the weakly cemented mudstone on the direct roof of the coal seam are determined.
[0024] Step 2, according to the corresponding requirements of the "Technical Specifications for Underground Water Exploration and Release", determine the length of the first-level water-stop casing 1 and the corresponding first-level borehole 2 depth in the coal seam, and convert the length of the second-level solid casing 3 and the corresponding second-level borehole 4 depth according to the borehole inclination, coal seam thickness and mudstone thickness; wherein, after the length of the first-level water-stop casing 1 is obtained according to the corresponding requirements of the "Technical Specifications for Underground Water Exploration and Release", the depth of the first-level borehole 2 is roughly equivalent to the length of the first-level water-stop casing 1, and when constructing the first-level borehole 2, it can exceed the design length of the first-level water-stop casing 1 by about 0.5m to leave a margin; the length of the second-level solid casing 3 can be converted from the total thickness of the coal seam and mudstone and the borehole inclination. Since the second-level solid casing 3 is partially inside the first-level water-stop casing 1, the depth of the second-level borehole 4 located in the mudstone layer can be obtained by subtracting the length of the first-level water-stop casing 1 from the second-level solid casing 3. Finally, the depth of the second-level borehole 4 drilled upward into the sandstone layer ensures that the upper end of the second-level solid casing 3 can be connected to the second-level flower casing 5 and can extend to the mudstone roof.
[0025] Step 3, according to the drilling azimuth, use Ф133mm drill bit to construct the first-level borehole 2 in the coal seam, insert the first-level water-stop casing 1 with an outer diameter of 108mm and a wall thickness of 6.5mm into the first-level borehole 2, and inject grout into the annulus between the first-level water-stop casing 1 and the first-level borehole 2 to fix the pipe. After fixing the pipe, sweep the hole to the bottom of the hole and conduct a pressure test until it passes.
[0026] Step 4, connect the gate valve 7 through the flange 6 at the bottom of the primary water-stop casing 1 to prevent a large amount of water from suddenly gushing out of the roof during subsequent drilling, use a Ф89mm drill bit to construct a secondary borehole 4 in the mudstone in the primary water-stop casing 1 and drill into the sandstone, remove the gate valve 7 after the construction of the secondary borehole 4 is completed, connect the secondary flower casing 5 with the same inner and outer diameter and full of holes on the side wall to the upper end of the secondary solid casing 3 with an outer diameter of 63mm*wall thickness of 5.5mm and lower it into the secondary borehole 4 through the primary water-stop casing 1, and then connect the gate valve 7 through the flange 6 at the bottom of the primary water-stop casing 1, and then grout the pipe in the annulus between the secondary solid casing 3, the secondary borehole 4 and the primary water-stop casing 1, and use cement slurry to seal the grouting pipe. Stop grouting after the slurry is reversed from the secondary solid casing 3, and wait for the slurry to solidify. The solidification time shall not be less than 72 hours.
Claims
1. A method for draining water from the roof of a coal seam to prevent the weakly cemented mudstone from being weakened by water, characterized in that: The following steps are involved: Step 1: determine the opening position, inclination and azimuth of the drainage borehole, and at the same time determine the thickness of the coal seam above the opening position and the thickness of the weakly cemented mudstone directly on the top of the coal seam; Step 2, determine the length of the primary water stop casing and the corresponding primary borehole depth, and determine the length of the secondary casing and the corresponding secondary borehole depth according to the borehole inclination, coal seam thickness and mudstone thickness; Step 3, constructing a primary borehole in the coal seam according to the borehole azimuth, inserting a primary water-stopping casing into the primary borehole, and injecting grouting into the annulus between the primary water-stopping casing and the primary borehole to fix the pipe; Step 4, construct a secondary borehole into the mudstone in the primary water-stop casing and drill into the sandstone, connect the secondary flower casing to the upper end of the secondary solid casing and lower it into the secondary borehole through the primary water-stop casing, so that the secondary solid casing extends to the mudstone top plate, and then grouting is performed in the annulus between the secondary solid casing, the secondary borehole and the primary water-stop casing to fix the pipe.
2. The roof drainage method for preventing the weakly cemented mudstone in the direct roof of the coal seam from being weakened by water as claimed in claim 1, characterized in that: The first-level drilling hole is constructed using a Ф133mm drill bit, and the second-level drilling hole is constructed using a Ф89mm drill bit.
3. The roof drainage method for preventing the weakly cemented mudstone in the direct roof of the coal seam from being weakened by water as claimed in claim 1, characterized in that: The first-level water-stop sleeve has an outer diameter of 108 mm and a wall thickness of 6.5 mm, and the second-level solid sleeve and the second-level flower sleeve both have an outer diameter of 63 mm and a wall thickness of 5.5 mm.
4. The roof drainage method for preventing the weakly cemented mudstone in the direct roof of the coal seam from being weakened by water as claimed in claim 1, characterized in that: The secondary flower sleeve is a sleeve with side walls covered with holes.
5. The roof drainage method for preventing the weakly cemented mudstone in the direct roof of the coal seam from being weakened by water as claimed in claim 1, characterized in that: In step 4, a gate valve is first connected to the bottom end of the primary water-stop casing before constructing the secondary borehole, and the gate valve is removed after the secondary borehole is constructed. After the secondary flower casing and the secondary solid casing are lowered, the gate valve is connected to the bottom end of the primary water-stop casing, and then grouting is performed to fix the pipe in the annulus between the secondary solid casing, the secondary borehole and the primary water-stop casing.
6. The roof drainage method for preventing the weakly cemented mudstone in the direct roof of the coal seam from being weakened by water as claimed in claim 1, characterized in that: The grouting and pipe fixing in step 4 is performed by double-liquid grouting or cement slurry for plugging. Grouting is stopped after the slurry is reversed from the secondary solid casing, and the grouting is waited for to solidify.