Grouting method for advanced treatment of high-pressure-bearing karst water disasters of coal seam floor

Abstract

According to the grouting method for advanced treatment of the high-pressure-bearing karst water disasters of the coal seam floor, the specific grouting process is set, normal-pressure grouting is adopted at the initial stage of grouting, only too grey water exists in cracks, and after grouting slurry is injected, due to the fact that the density of the slurry is larger than that of the too grey water in the cracks, the slurry can enter the cracks through self weight, and the grouting effect is achieved. The effect of replacing too grey water by the slurry is achieved; the pressurization grouting stage aims to block a small crack channel, under the action of pressure, grout is further diffused in the transverse direction and the longitudinal direction, the control range of drilling grouting is widened, and originally isolated cement is firmly connected into a whole; later-stage high-pressure grouting is used for consolidating the early-stage grouting effect, and due to the fact that the water head pressure of a corresponding area is high and generally ranges from 6 Mpa to 8 Mpa, the solidification anti-pressure capacity of pressurized grouting cement is 1t; in the later stage of the pressurized grouting stage, grouting needs to be conducted, the cement injection amount is adjusted, and the grouting pressure is increased; therefore, the effective protection layer thickness is increased, and the purpose of safe coal mining is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of mineral resource development, and in particular to a grouting method for advanced treatment of high-pressure karst water hazards in coal seam floors. Background Art

[0002] Coal is one of the important energy sources. Safe and efficient mining of coal is crucial to maintaining social stability and promoting economic development. As the mining of upper coal resources gradually dries up, the mining of lower coal resources often faces the threat of deep mining and high-pressure water hazards. There are many mines in China that are threatened by high-pressure karst water hazards in the bottom plate. The high-pressure karst water hazard accidents in the bottom plate are extremely harmful. Once water bursts, it will bring disaster to the coal mine. Therefore, the advanced prevention and control of high-pressure water hazards in the coal seam bottom plate has become a hot issue at present and in the future.

[0003] After searching, the Chinese invention patent with application number "CN202210583614.1" discloses a segmented grouting system and a pre-grouting method for a soft coal seam working face in the field of coal mine disaster prevention and control. The grouting system includes a feeding and stirring assembly, a grouting pump, a pressure gauge, a flow meter, a grouting device, a section of a hollow grouting pipe of specification A and multiple sections of a hollow grouting pipe of specification B; the pre-grouting method includes the following steps: step one: drilling and installing a grouting pipe; step two: determining the timing of pre-grouting; step three: performing deep hole segmented grouting; step four: re-injection at some locations; step five: grouting of the next grouting pipe. The determination of the timing of pre-grouting in the pre-grouting method of the present invention makes the pre-grouting work more standardized and scientific, reduces blindness, and is more conducive to the injection of slurry into soft coal seams; the design of the grouting system can avoid local leakage and serious slurry leakage, so that the soft coal body within the entire working face can be fully grouted, improving the grouting reinforcement effect.

[0004] The above-mentioned segmented grouting system and advance grouting method for the working face of the soft coal seam can fully grout the soft coal body, but no analysis is conducted on different grouting environments, and no measures are taken to adapt to local conditions. It is also impossible to evaluate the treatment effect of high-pressure grouting and plugging of limestone karst gaps, fissures and other structures exposed during the drilling process, and the treatment effect is poor.

[0005] In summary, there is an urgent need for a grouting method for advanced control of high-pressure karst water hazards in coal seam floors to solve the above problems. Summary of the invention

[0006] In order to make up for the above shortcomings, the present invention provides a grouting method for advance control of high-pressure karst water hazards in the coal seam floor, which is used to solve the above-mentioned existing segmented grouting system and advance grouting method for the working face of the soft coal seam. The soft coal body can be fully grouted, but no analysis is conducted on different grouting environments, and it is not adapted to local conditions. It is also impossible to evaluate the control effect of high-pressure grouting and sealing of the limestone karst gaps, cracks and other structures revealed during the drilling process, and the control effect is poor.

[0007] The present invention is achieved in that:

[0008] A grouting method for advanced treatment of high-pressure karst water hazards in coal seam floors, comprising the following steps:

[0009] S1. Drill normally and observe the leakage;

[0010] When observing the leakage, it is specifically divided into no leakage, leakage greater than 5 times the normal value, and leakage greater than 3m 3 / h;

[0011] After drilling to the end hole position of the branch hole, the horizontal section of the branch hole needs to be flushed.

[0012] The specific operation steps are as follows: after drilling to the terminal hole position of the branch hole, circulate the drilling fluid. During the circulation process, the drill tool needs to be moved up and down, with an amplitude of not less than 5m to ensure the safety of the drill tool. The remaining rock debris in the hole is brought up through circulation until there is no rock debris in the drilling fluid returned to the hole. Then replace the slurry in the borehole with clean water, and circulate it with clean water. The circulation time should be not less than 1h. The drill tool must be moved frequently during the circulation process. During the circulation process, the drill tool is lifted to ensure the safety of the hole.

[0013] S2. Use the full-hole section grouting method of segmented water pressure. Before grouting, a water pressure test is carried out, and the unit water absorption of the grouting section is calculated based on the water pressure test results;

[0014] Specifically, a water pressure test is conducted for the cases where there is no leakage or the leakage is 5 times greater than the normal value, and then the slurry type and proportion are calculated and determined;

[0015] For leakage not less than 3m 3 / h, continue drilling for 10m before pulling out the drill and observe the water level in the hole;

[0016] The specific water pressure test before grouting is:

[0017] Before grouting each branch hole for exploration and treatment, a water pressure test must be carried out, and the grouting pump capacity must be adjusted according to the water pressure conditions;

[0018] Before grouting, a water pressure test is carried out with clean water, and the results of the water pressure test are expressed as the water permeability q.

[0019] q=Q / (P×L)

[0020] Where: q—water permeability (Lu)

[0021] Q—pressure flow rate (L / min)

[0022] P—Total pressure acting in the pressure test section (MPa)

[0023] L—Test pressure section length (m)

[0024] Determine the density of the slurry based on the results of the water pressure test. Generally speaking, a trial injection must be carried out with a thin slurry to understand the amount of slurry consumed by the leak and the orifice pressure.

[0025] S3. Grouting, principles of grouting management and grouting stopping methods: follow the principle of first thin and then thick, and re-inject thick slurry, stop slurry at the hole mouth, and grout the horizontal branch holes in sections or in a forward grouting method; combine continuous grouting with intermittent grouting, and the intermittent grouting time is not less than 12 hours;

[0026] The grouting was carried out on the principle of "finish one hole, grout one hole, and grout as leakage occurs". A water pressure test was carried out every 100m during the drilling process. After the test, the grouting material ratio was determined based on the calculated permeability q value, and then the grouting work was continued. Only after the grouting was completed could the next branch hole be drilled.

[0027] The specific grouting process includes:

[0028] S3.1, normal pressure grouting stage;

[0029] S3.2, pressurized grouting stage: the grouting pressure is generally 2-3Mpa, and the grouting is carried out in a state of still water and gradually increasing pressure at the orifice;

[0030] S3.3, high-pressure grouting stage: the water head pressure is generally around 6-8Mpa, and the cement injection volume is adjusted. According to the requirements, the pressure at the bottom of the grouting hole during the high-pressure grouting stage is 1.5-2 times the hydrostatic pressure of the corresponding area. When the pressure stabilizes, stop grouting and perform hole sweeping;

[0031] Preferably, the grouting adopts the continuous grouting method, the slurry is thin at first and then thick, and the water-cement ratio of the slurry is adjusted in time according to the slurry consumption, and the specific gravity of the slurry is controlled at 1.1-1.5.

[0032] Preferably, a grouting station is built on the ground, and grouting is injected into the grouting hole through a grouting pump and a grouting pipeline. The grouting equipment and production use a semi-automatic bulk cement system. The main equipment includes bulk cement tanks, screw propellers, jet mixers, grouting pumps, grouting pipelines and other supporting facilities and tools. The equipment is required to operate well at all times to ensure normal and smooth grouting.

[0033] Preferably, the main grouting material is 32.5 slag silicate cement; medium and fine sand is added as aggregate.

[0034] Preferably, when encountering larger karst fissures, materials such as sand, fly ash, and early setting agent can be added.

[0035] Preferably, after each single-hole grouting is completed, water is pressed into the hole. The amount of water pressed is 1 to 1.5 times the sum of the volume from the next branch side drilling point to the hole mouth and the pipeline volume. After the water is pressed, the hole mouth gate valve is closed and the pressure is held for 3 to 4 hours. After that, the drill bit is promptly lowered to sweep the hole to a position near the next side drilling point.

[0036] S4. Grouting is terminated after reaching the design pressure and passing the inspection;

[0037] Preferably, for the case where there is no leakage and the leakage is 5 times greater than the normal value, the grouting end standard is:

[0038] 1.1 The final pressure of the grouting hole is determined according to the regional elevation, and the final grouting pressure (total pressure) shall not be less than 1.5 times the maximum hydrostatic pressure of the aquifer in the corresponding area.

[0039] 1.2 Pump volume reaches 3m 3 / h or less and the grouting pressure reaches the design pressure and is stable for more than 30 minutes. At the same time, the unit water absorption rate of the grouting section is not greater than 0.01 (L / min·m 2 ), the single hole grouting can be completed.

[0040] Preferably, the leakage is not less than 3m 3 / h, grouting end standard:

[0041] 2.1 Stop grouting, sweep the hole to the original hole depth, and use the water pressure test to verify the grouting quality. When the grouting pressure has reached the design pressure value and the pressure continues to rise due to continuous grouting with a large pump volume, reduce the pump volume step by step to keep the pressure value as stable as possible until the grouting end standard is reached.

[0042] It should be noted that it is strictly forbidden to adjust the pump volume in a jumpy manner.

[0043] Preferably, when the grouting pressure does not reach the design pressure value, S3-S4 are repeated until the grouting quality is qualified.

[0044] S5, sealing the hole;

[0045] After drilling each branch hole, if there is no leakage at the end of the hole, after the water pressure test, the branch section will be selected for high-pressure grouting or hole sealing according to the test results. If the hole is sealed, the sealing cement slurry should be returned from the bottom of the hole to the next branch inclination point, and a high-grade cement should be used as a cement plug at the inclination point.

[0046] The hole sealing cement slurry injection should be carried out by the segmented grouting method of lowering the bare drill pipe, that is, after injecting a certain height of cement slurry, the drill tool of the corresponding height is pulled out, and each injection generally does not exceed 100m; after the cement slurry is injected back from the drill pipe mouth at the bottom of the well, the drill tool must be moved until the drill tool is completely in the casing or pulled out of the wellhead.

[0047] Compared with the prior art, the technical solution of this application has the following beneficial effects:

[0048] 1. The grouting method for advanced control of high-pressure karst water hazards in the coal seam floor shown in the present invention is to perform a water pressure test before grouting, and calculate the unit water absorption of the grouting section according to the result of the water pressure test; and perform a water pressure test for the cases where there is no leakage or the leakage is 5 times greater than the normal value, and then calculate and determine the slurry type and ratio; its main purpose is to dredge the grouting pipeline and the rock cracks in the hole, measure the permeability of the unit injected layer, and re-determine the amount of leakage through changes, so as to provide a solid basis for grouting and ensure the effect of grouting.

[0049] 2. The grouting method for advance control of high-pressure karst water hazards in the coal seam floor shown in the present invention requires flushing of the horizontal section of the branch hole after the borehole is drilled to the final hole position. The purpose is to remove the mud skin on the hole wall through circulating mud and achieve the purpose of flushing the cracks in the hole, thereby avoiding interference with the grouting and resulting in unqualified grouting quality.

[0050] 3. The grouting method for advance control of high-pressure karst water hazards in the coal seam floor demonstrated in the present invention, by setting up an evaluation of the grouting control effect, ends the grouting after reaching the design pressure and passing the inspection, strictly ensures the safety of the drilling process, achieves the purpose of safe coal mining, and provides guarantee for safe and efficient mining of coal mines.

[0051] 4. The grouting method for advanced control of high-pressure karst water hazards in the coal seam floor shown in the present invention comprises a normal pressure grouting stage, a pressurized grouting stage and a high-pressure grouting stage by setting a specific grouting process. At the beginning of grouting, normal pressure grouting is adopted, and there is only lime water in the cracks. After the grouting slurry is injected, since the density of the slurry is greater than the density of the lime water in the cracks, the slurry can enter the cracks by its own weight, and plays the role of the slurry replacing the lime water; the purpose of the pressurized grouting stage is to block the small crack channels, and under the action of pressure, the slurry is further diffused horizontally and vertically, increasing the control range of drilling grouting, and making the originally isolated cement firmly connected into a whole; the later high-pressure grouting is to consolidate the effect of the early grouting. Since the water head pressure in the corresponding area is high, the head pressure is generally around 6 to 8 MPa, and the solidification compressive strength of the pressurized grouting cement is less than the head pressure, so in the later stage of the pressurized grouting stage, the cement injection amount should be adjusted by grouting, and the grouting pressure should be increased; thereby increasing the thickness of the effective protective layer and achieving the purpose of safe coal mining. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0053] Figure 1 A grouting construction flow chart of an embodiment of a grouting method for advanced treatment of high-pressure karst water hazards in a coal seam floor according to the present invention;

[0054] Figure 2 The present invention is a schematic diagram of drilling construction of an embodiment of a grouting method for advanced treatment of high-pressure karst water hazards in a coal seam floor. DETAILED DESCRIPTION

[0055] First of all, it should be pointed out that in the different described embodiments, the same parts are provided with the same reference numerals or the same component names, wherein the disclosure contained in the entire description can be transferred to the same parts with the same reference numerals or the same component names. Selected positional descriptions in the description, such as top, bottom, lateral, etc., also refer to the directly described and shown figures and are transferred to the new positions in the case of a change in position.

[0056] Embodiment 1:

[0057] See also Figure 1 - Figure 2 , the present invention provides a technical solution:

[0058] like Figure 1 As shown, a grouting method for advanced treatment of high-pressure karst water hazards in coal seam floors includes the following steps: S1, normal drilling and observation of leakage;

[0059] Specifically, during normal drilling, thin mud or solid-free mud is used for drilling, and the full mud properties are measured every 8 hours, and the general mud properties (density, viscosity) are measured every 2 hours; the water level (mud pool liquid level, well liquid level) is measured once after each drilling and before drilling; the drilling fluid consumption is monitored automatically by the system, and the system is set to record once every 30 minutes, and more frequent observations are conducted when necessary;

[0060] When observing the leakage, it is specifically divided into no leakage, leakage greater than 5 times the normal value, and leakage greater than 3m 3 / h;

[0061] It is worth noting that after the borehole is drilled to the end hole position of the branch hole, the horizontal section of the branch hole needs to be flushed. The purpose is to remove the mud skin on the hole wall through circulating mud and achieve the purpose of flushing the cracks in the hole.

[0062] The specific operation steps are as follows: after drilling to the terminal hole position of the branch hole, circulate the drilling fluid. During the circulation process, the drill tool needs to be moved up and down, with an amplitude of not less than 5m to ensure the safety of the drill tool. The remaining rock debris in the hole is brought up through circulation until there is no rock debris in the drilling fluid returned to the hole. Then replace the slurry in the borehole with clean water, and circulate it with clean water. The circulation time should be not less than 1h. The drill tool must be moved frequently during the circulation process. During the circulation process, the drill tool is lifted to ensure the safety of the hole.

[0063] S2. Use the full-hole section grouting method of segmented water pressure. Before grouting, a water pressure test is carried out, and the unit water absorption of the grouting section is calculated based on the water pressure test results;

[0064] Specifically, a water pressure test is conducted for the cases where there is no leakage or the leakage is 5 times greater than the normal value, and then the slurry type and proportion are calculated and determined;

[0065] For leakage not less than 3m 3 / h, continue drilling for 10m before pulling out the drill and observe the water level in the hole;

[0066] The specific water pressure test before grouting is:

[0067] Before grouting each branch hole for exploration and treatment, a water pressure test must be carried out, and the grouting pump capacity must be adjusted according to the water pressure conditions;

[0068] Before grouting, a water pressure test is carried out with clean water, and the results of the water pressure test are expressed as the water permeability q.

[0069] q=Q / (P×L)

[0070] Where: q—water permeability (Lu)

[0071] Q—pressure flow rate (L / min)

[0072] P—Total pressure acting in the pressure test section (MPa)

[0073] L—Test pressure section length (m)

[0074] Determine the density of the slurry based on the results of the water pressure test. Generally speaking, a trial injection must be carried out with a thin slurry to understand the amount of slurry consumed by the leak and the orifice pressure.

[0075] S3. Grouting, principles of grouting management and grouting stopping methods: follow the principle of first thin and then thick, and re-inject thick slurry, stop slurry at the hole mouth, and grout the horizontal branch holes in sections or in a forward grouting method; combine continuous grouting with intermittent grouting, and the intermittent grouting time is not less than 12 hours;

[0076] The grouting was carried out on the principle of "finish one hole, grout one hole, and grout as leakage occurs". A water pressure test was carried out every 100m during the drilling process. After the test, the grouting material ratio was determined based on the calculated permeability q value, and then the grouting work was continued. Only after the grouting was completed could the next branch hole be drilled.

[0077] The specific grouting process includes:

[0078] S3.1, Normal pressure grouting stage: At the beginning of grouting, there is only lime water in the cracks. After the grouting slurry is injected, since the density of the slurry is greater than the density of the lime water in the cracks, the slurry can enter the cracks by its own weight, playing the role of replacing the lime water;

[0079] S3.2, pressurized grouting stage: The grouting pressure at this stage is generally 2-3Mpa. Grouting is carried out in a state of static water and gradual pressure increase at the hole mouth. Its purpose is to block small crack channels. Under the action of pressure, the slurry is further diffused horizontally and vertically, increasing the control range of drilling grouting and making the originally isolated cement firmly connected into a whole;

[0080] S3.3, High-pressure grouting stage: The purpose of high-pressure grouting in the later stage is to consolidate the effect of grouting in the earlier stage. Since the head pressure of the water in the corresponding area is high, the head pressure is generally around 6-8Mpa, and the solidification compressive strength of the pressurized grouting cement is less than the head pressure. Therefore, in the later stage of the pressurized grouting stage, the cement injection volume should be adjusted and the grouting pressure should be increased. According to the requirements, the bottom pressure of the grouting hole in the high-pressure grouting stage is 1.5-2 times the hydrostatic pressure of the water in the corresponding area. When the pressure is stable, stop grouting and perform hole sweeping;

[0081] Preferably, the grouting adopts the continuous grouting method, the slurry is thin at first and then thick, and the water-cement ratio of the slurry is adjusted in time according to the slurry consumption, and the specific gravity of the slurry is controlled at 1.1-1.5.

[0082] Preferably, a grouting station is built on the ground, and grouting is injected into the grouting hole through a grouting pump and a grouting pipeline. The grouting equipment and production use a semi-automatic bulk cement system. The main equipment includes bulk cement tanks, screw propellers, jet mixers, grouting pumps, grouting pipelines and other supporting facilities and tools. The equipment is required to operate well at all times to ensure normal and smooth grouting.

[0083] Preferably, the main grouting material is 32.5 slag silicate cement; medium and fine sand is added as aggregate.

[0084] Preferably, after each single-hole grouting is completed, water is pressed into the hole. The amount of water pressed is 1 to 1.5 times the sum of the volume from the next branch side drilling point to the hole mouth and the pipeline volume. After the water is pressed, the hole mouth gate valve is closed and the pressure is held for 3 to 4 hours. After that, the drill bit is promptly lowered to sweep the hole to a position near the next side drilling point.

[0085] S4. Grouting is terminated after reaching the design pressure and passing the inspection;

[0086] Preferably, for the case where there is no leakage and the leakage is 5 times greater than the normal value, the grouting end standard is:

[0087] 1.1 The final pressure of the grouting hole is determined according to the regional elevation, and the final grouting pressure (total pressure) shall not be less than 1.5 times the maximum hydrostatic pressure of the aquifer in the corresponding area.

[0088] 1.2 Pump volume reaches 3m 3 / h or less and the grouting pressure reaches the design pressure and is stable for more than 30 minutes. At the same time, the unit water absorption rate of the grouting section is not greater than 0.01 (L / min·m 2 ), the single hole grouting can be completed.

[0089] Preferably, the leakage is not less than 3m 3 / h, grouting end standard:

[0090] 2.1 Stop grouting, sweep the hole to the original hole depth, and use the water pressure test to verify the grouting quality. When the grouting pressure has reached the design pressure value and the pressure continues to rise due to continuous grouting with a large pump volume, reduce the pump volume step by step to keep the pressure value as stable as possible until the grouting end standard is reached.

[0091] It should be noted that it is strictly forbidden to adjust the pump volume in a jumpy manner.

[0092] Preferably, when the grouting pressure does not reach the design pressure value, S3-S4 are repeated until the grouting quality is qualified.

[0093] S5, sealing the hole;

[0094] After drilling each branch hole, if there is no leakage at the end of the hole, after the water pressure test, the branch section will be selected for high-pressure grouting or hole sealing according to the test results. If the hole is sealed, the sealing cement slurry should be returned from the bottom of the hole to the next branch inclination point, and a high-grade cement should be used as a cement plug at the inclination point.

[0095] The hole sealing cement slurry injection should be carried out by the segmented grouting method of lowering the bare drill pipe, that is, after injecting a certain height of cement slurry, the drill tool of the corresponding height is pulled out, and each injection generally does not exceed 100m; after the cement slurry is injected back from the drill pipe mouth at the bottom of the well, the drill tool must be moved until the drill tool is completely in the casing or pulled out of the wellhead.

[0096] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0097] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A grouting method for advanced treatment of high-pressure karst water hazards in coal seam floors, characterized in that it comprises the following steps: S1. Drill normally and observe the leakage; The leakage observation time is divided into: no leakage, leakage greater than 5 times the normal value, and leakage greater than 3m 3 / h S2. Use the full-hole section grouting method of segmented water pressure. Before grouting, a water pressure test is carried out, and the unit water absorption of the grouting section is calculated based on the water pressure test results; S3. Grouting, principles of grouting management and grouting stopping methods: follow the principle of first thin and then thick, and re-inject thick slurry, stop slurry at the hole mouth, and grout the horizontal branch holes in sections or in a forward grouting method; combine continuous grouting with intermittent grouting, and the intermittent grouting time is not less than 12 hours; S4. Grouting is terminated after reaching the design pressure and passing the inspection; For the case of no leakage or leakage amount greater than 5 times the normal value, the grouting end standard is: 1.1 The final pressure of the grouting hole is determined according to the regional elevation, and the final pressure (total pressure) of grouting shall not be less than 1.5 times the maximum hydrostatic pressure of the aquifer in the corresponding area; 1.2 Pump volume reaches 3m 3 / h or less and the grouting pressure reaches the design pressure and is stable for more than 30 minutes. At the same time, the unit water absorption rate of the grouting section is not greater than 0.01 (L / min·m 2 ), the single hole grouting can be completed; For leakage not less than 3m 3 / h, grouting end standard: 2.1 Stop grouting, sweep the hole to the original hole depth, and use the water pressure test to verify the grouting quality. When the grouting pressure has reached the design pressure value and the pressure continues to rise with large pump volume, reduce the pump volume step by step to keep the pressure value as stable as possible until the grouting end standard is reached; when the grouting pressure has not reached the design pressure value, repeat S3-S4 until the grouting quality is qualified. S5. Seal the hole.

2. A grouting method for advanced treatment of high-pressure karst water hazards in coal seam floors according to claim 1, characterized in that: In step S1, after the borehole is drilled to the end hole position of the branch hole, the horizontal section of the branch hole needs to be flushed.

3. The grouting method for advanced treatment of high-pressure karst water hazards in coal seam floors according to claim 1 is characterized in that: In step S2, a water pressure test is performed for the cases where there is no leakage or the leakage amount is 5 times greater than the normal value, and then the slurry type and ratio are calculated and determined.

4. A grouting method for advanced treatment of high-pressure karst water hazards in coal seam floors according to claim 3, characterized in that: For leakage not less than 3m 3 / h, continue drilling for 10m and then stop drilling and observe the water level in the hole.

5. A grouting method for advanced treatment of high-pressure karst water hazards in coal seam floors according to claim 4, characterized in that: In step S3, this grouting is carried out in the principle of "complete one hole, grout one hole, and grout as leakage occurs". A water pressure test is carried out every 100m during the drilling process. After the test, the grouting material ratio is determined according to the calculated permeability q value, and then the grouting work is continued; only after the grouting is completed can the next branch hole be drilled.

6. A grouting method for advanced treatment of high-pressure karst water hazards in coal seam floors according to claim 5, characterized in that: In step S3, the specific grouting process includes: S3.1, normal pressure grouting stage; S3.2, pressurized grouting stage: the grouting pressure is generally 2-3Mpa, and the grouting is carried out in a state of still water and gradually increasing pressure at the orifice; S3.3, high-pressure grouting stage: the head pressure is generally around 6-8Mpa. Adjust the cement injection volume. According to the requirements, the bottom pressure of the grouting hole in the high-pressure grouting stage is 1.5-2 times the hydrostatic pressure of the corresponding area. When the pressure stabilizes, stop grouting and sweep the hole.

7. The grouting method for advanced treatment of high-pressure karst water hazards in coal seam floors according to claim 1 is characterized in that: In step S5, after drilling of each branch hole is completed, if there is no leakage at the end of the hole, after a water pressure test, high-pressure grouting or sealing of the branch section is selected according to the test result.

8. A grouting method for advanced treatment of high-pressure karst water hazards in coal seam floors according to claim 4, characterized in that: In step S2, the water pressure test before grouting is specifically as follows: Before grouting each branch hole for exploration and treatment, a water pressure test must be carried out, and the grouting pump capacity must be adjusted according to the water pressure conditions; Before grouting, a water pressure test is carried out with clean water, and the results of the water pressure test are expressed as the water permeability q. q=Q / (P×L) Where: q—water permeability (Lu) Q—pressure flow rate (L / min) P—Total pressure acting in the pressure test section (MPa) L—Test pressure section length (m) To determine the density of the slurry based on the results of the water pressure test, it is necessary to first conduct a trial injection with a thin slurry to understand the amount of slurry consumed by the leak and the orifice pressure.

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