Drilling combined grouting water plugging technology for coal seam post-mining roof composite aquifer

Abstract

The present application relates to a kind of coal seam post-mining roof composite aquifer drilling combined grouting water plugging process, comprising the following steps: constructing coal seam and roof composite aquifer geological model;Drill straight hole in the above goaf, carry out coal seam roof mining overburden failure law detection, obtain the development height of water flowing fractured zone, the vertical spatial development characteristics of mining fissure and the contact relationship of water flowing fractured zone and roof aquifer, select target aquifer section to carry out injectability test;Drill directional borehole outside the influence range of goaf, construct interception structure according to the contact relationship;Establish ground grouting system, according to the plugging grouting process, grouting water plugging to the constructed interception structure.The coal seam post-mining roof composite aquifer drilling combined grouting water plugging process of the present application couples overburden failure law detection, aquifer injectability test and grouting water plugging function by the joint arrangement of ground straight hole and ground directional borehole, realizes the management of coal seam post-mining roof composite aquifer gushing.

Description

Technical Field

[0001] This invention relates to the field of mine water hazard prevention and control technology, specifically to a combined grouting and water plugging process for drilling composite aquifers in the roof of a coal seam after mining. Background Technology

[0002] After coal seam mining, the overlying strata fracture due to mining activities, forming a water-conducting fracture zone. This zone extends from bottom to top, affecting some aquifers and easily connecting to the multi-layered sandstone aquifer in the roof. This leads to continuous water inflow into the roof of the goaf, increasing the mine's drainage burden and threatening safe production.

[0003] In related technologies, limiting the thickness of coal seam mining is used to control the development height of water-conducting fracture zones, thereby reducing their contact with the roof aquifer and thus decreasing the roof water inflow. However, limiting the mining thickness inevitably leads to the loss of coal resources and a reduction in recovery rate. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the related art.

[0005] Therefore, embodiments of the present invention propose a combined drilling and grouting water plugging process for the composite aquifer in the roof of a coal seam after mining, comprising the following steps: Step 1: Construct a geological model of the composite aquifer of coal seam and roof; Step 2: Drill direct boreholes on the surface above the goaf to detect the failure pattern of the overlying strata of the coal seam roof caused by mining, obtain the development height of the water-conducting fracture zone, the vertical spatial development characteristics of the mining fractures, and the contact relationship between the water-conducting fracture zone and the aquifer in the roof, and select the target aquifer section for injection capability test; Step 3: Construct directional boreholes on the ground outside the affected area of ​​the goaf, and build a water-cutting structure based on the aforementioned contact relationship; Step 4: Establish a ground grouting system and inject grout into the water-blocking structure constructed in Step 3 according to the leakage-stopping grouting process.

[0006] The coal seam post-mining roof composite aquifer drilling and grouting water-blocking technology of this invention utilizes direct surface drilling to detect overburden failure patterns, obtain the development height of water-conducting fracture zones, the vertical spatial development characteristics of mining-induced fractures, and the contact relationship between the water-conducting fracture zones and the roof aquifer. Injectability tests provide empirical support for subsequent grouting, providing measured evidence for water inflow sources, mechanisms, and grouting parameters that are difficult to determine in related technologies. A water-cutting structure is constructed through directional surface drilling, achieving sealing after grouting. This invention's coal seam post-mining roof composite aquifer drilling and grouting water-blocking technology, through the combined arrangement of direct and directional surface drilling, couples overburden failure pattern detection, aquifer injectability testing, and grouting water-blocking functions to achieve the control of water inflow in the coal seam post-mining roof composite aquifer.

[0007] In some embodiments, in step 1, the aquifer above the coal seam roof is marked as the i-th aquifer from bottom to top, and the overlying lithology is classified according to the saturated uniaxial compressive strength of the rock: hard, medium hard, soft and very soft. The development height of the water-conducting fracture zone is predicted by empirical formula method and analogy method.

[0008] In some embodiments, in step 2, the ground direct boreholes are arranged above the goaf, at a distance greater than 30m from the starting mining line and not less than 15m from the ending mining line. There are two direct boreholes distributed inside the mining roadway, or there are multiple direct boreholes. The development height of the water-conducting fracture zone is predicted using empirical formulas and analogies.

[0009] In some embodiments, in step 2, a direct borehole is drilled on the ground to expose the first aquifer and the bottom boundary of the aquifer above the influence range of the water-conducting fracture zone. The first aquifer is less than or equal to 50m from the top boundary of the water-conducting fracture zone. Full-section casing is used for water stoppage above the first aquifer. The target aquifer section is the area from the first aquifer to the bottom boundary of the aquifer. When the injectability test is carried out on the target aquifer section, the connectivity between the target aquifer section and the goaf is checked to determine whether the coal seam roof water inflow is involved by the target aquifer section, and a preliminary aquifer grouting parameter adjustment plan is formed.

[0010] In some embodiments, in step 3, the ground directional drilling includes a first-stage, a second-stage, and a third-stage borehole. The first-stage borehole has a first-stage casing that extends at least 5m into the stable bedrock. The second-stage borehole has a second-stage casing that extends to the top of the target aquifer. The third-stage borehole is a bare borehole.

[0011] In some embodiments, in step 3, the contact relationship includes: if the average thickness of the aquifer is less than 40m and the water-conducting fracture zone enters or completely penetrates the aquifer, then a water-cutting wall structure is constructed at the edge of the goaf through ground directional drilling.

[0012] In some embodiments, the ground directional drilling forms the water-cutting wall structure by arranging multiple first horizontal branch holes in the target aquifer section. One or more water-cutting wall structures are set around the working face according to the aquifer runoff pattern. The multiple first horizontal branch holes are located in the same vertical plane, and the vertical distance between adjacent first horizontal branch holes is 10-20m. Multiple water-cutting wall structures are set up by moving the plane position according to the grouting effect. The multiple first horizontal branch holes of adjacent water-cutting wall structures are arranged vertically and horizontally in an alternating manner.

[0013] In some embodiments, in step 3, the contact relationship includes: if the average thickness of the aquifer is greater than 40m and less than 60m, and the top of the water-conducting fracture zone enters the bottom of the aquifer, then a water-cutting plate structure is constructed at the top of the water-conducting fracture zone and the micro-fracture zone at the bottom of the aquifer through directional drilling on the ground; if the contact relationship includes: if the average thickness of the aquifer is greater than 40m and less than 60m, and the top of the water-conducting fracture zone enters the middle of the aquifer, then a water-cutting plate structure is constructed at the top of the water-conducting fracture zone and the micro-fracture zone where the aquifer is damaged through directional drilling on the ground, and a water-cutting wall structure is constructed simultaneously, and the water-cutting wall structure and the water-cutting plate structure form a grouting closed shape after grouting.

[0014] In some embodiments, a plurality of second horizontal branch holes arranged by ground directional drilling form the water-cutting plate structure, the spacing between adjacent second horizontal branch holes is 30-40m, and the coverage area of ​​the water-cutting plate structure is greater than or equal to the influence area of ​​the working face goaf; the water-cutting plate structure is moved up or down according to the grouting and water-blocking effect, and / or a plurality of the water-cutting plate structures are set.

[0015] In some embodiments, in step 4, the grouting process for plugging leaks is as follows: during the ground directional drilling construction in step 3, if the drilling fluid leakage is greater than 5 m³ / h, grouting is initiated, and at least one of the following is adjusted according to the leakage situation: grouting discharge rate, grout density, grout setting time, grout solid ratio, and plugging material.

[0016] In some embodiments, in step 4, if the drilling fluid loss is less than 10m³ 3 The discharge rate is 60-500 L / min, using single-component fly ash slurry. After the grouting pressure reaches the aquifer water pressure, cement-fly ash slurry is selected, with a slurry density of 1.1-1.4 g / cm³. 3 The grouting process ends once the grouting pressure reaches 1.5 times the aquifer water pressure; if the drilling fluid loss exceeds 10m³... 3 / h less than 30m 3 With a discharge rate of 60-800 L / min, fine sand with a particle size of less than 1 mm is used for filling gaps using mine water. After the grouting pressure reaches the aquifer water pressure, cement-fly ash grout is selected, with a grout density of 1.1-1.5 g / cm³. 3 The grouting process ends once the grouting pressure reaches 1.5 times the aquifer water pressure; if the drilling fluid loss exceeds 30m³... 3 / h less than 60m 3 With a discharge rate of 60-1000 L / min, fine sand with a particle size of less than 1 mm is used for filling gaps by conveying mine water. After the grouting pressure reaches 0.5 times the aquifer water pressure, cement-fly ash slurry is selected, mixed with sawdust with a particle size of less than 1 mm. The sawdust dosage is 50-100 kg / h, and the slurry density is 1.1-1.5 g / cm³. 3The grouting process ends once the grouting pressure reaches 1.5 times the aquifer water pressure; if the drilling fluid loss exceeds 60m³... 3 With a discharge rate of 60-1600 L / min, mine water is used to fill cracks with gravel with a particle size of less than 0.5-1.5 cm. After water returns from the wellhead, fine sand with a particle size of less than 1-3 mm is used to seal the cracks. After the grouting pressure reaches 0.5 times the aquifer water pressure, cement-fly ash slurry is selected, mixed with sawdust with a particle size of less than 1 mm. The sawdust dosage is 50-200 kg / h, and the slurry density is 1.1-1.5 g / cm³. 3 The grouting process ends when the grouting pressure reaches 1.5 times the water pressure of the aquifer. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of directional drilling in the vertical plane, showing a cutoff wall; Figure 2 This is a schematic diagram of directional drilling on a horizontal plane, showing a water-cutting plate. Figure label: 1. Primary hole section; 2. Secondary hole section; 3. Tertiary hole section; 31. First horizontal branch hole; 32. Second horizontal branch hole. Detailed Implementation

[0018] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0019] The following describes in detail, with reference to the accompanying drawings, the coal seam post-mining roof composite aquifer drilling and grouting water plugging process of the present invention.

[0020] The coal seam post-mining roof composite aquifer drilling and grouting water plugging process of this embodiment includes the following steps: Step 1: Construct a geological model of the composite aquifer of coal seam and roof; Step 2: Drill direct boreholes on the surface above the goaf to detect the failure pattern of the overlying strata of the coal seam roof caused by mining, obtain the development height of the water-conducting fracture zone, the vertical spatial development characteristics of the mining fractures, and the contact relationship between the water-conducting fracture zone and the aquifer in the roof, and select the target aquifer section for injection capability test; Step 3: Conduct directional drilling on the ground outside the affected area of ​​the goaf, and construct a water-cutting structure based on the contact relationship; Step 4: Establish a ground grouting system and inject grout into the water-blocking structure constructed in Step 3 according to the leakage-stopping grouting process.

[0021] The coal seam post-mining roof composite aquifer drilling and grouting water-blocking technology of this invention utilizes direct surface drilling to detect overburden failure patterns, obtain the development height of water-conducting fracture zones, the vertical spatial development characteristics of mining-induced fractures, and the contact relationship between the water-conducting fracture zones and the roof aquifer. Injectability tests provide empirical support for subsequent grouting, providing measured evidence for water inflow sources, mechanisms, and grouting parameters that are difficult to determine in related technologies. A water-cutting structure is constructed through directional surface drilling, achieving sealing after grouting. This invention's coal seam post-mining roof composite aquifer drilling and grouting water-blocking technology, through the combined arrangement of direct and directional surface drilling, couples overburden failure pattern detection, aquifer injectability testing, and grouting water-blocking functions to achieve the control of water inflow in the coal seam post-mining roof composite aquifer.

[0022] In some embodiments, in step 1, the spatial stratigraphic relationships of coal seams, aquifers, and other rock strata are analyzed to construct a geological model of the composite aquifer structure of coal seams and roof.

[0023] In some embodiments, in step 1, the aquifer above the coal seam roof is marked from bottom to top as the i-th aquifer, where i is a natural number. The overlying lithology is classified according to the saturated uniaxial compressive strength of the rock: hard, medium-hard, weak, and extremely weak. This classification serves as the lithological basis for predicting the development height of the water-conducting fracture zone in step 2. The development height of the water-conducting fracture zone is predicted using empirical formulas and analogy methods. The sequence marking of the aquifer establishes a unified spatial coordinate system, ensuring a clear stratigraphic correspondence for the determination of which aquifer the water-conducting fracture zone affects in step 2. Overlying lithology classification is a prerequisite for predicting the height of the water-conducting fracture zone using empirical formulas—different lithologies correspond to different empirical formulas. Inaccurate classification will lead to deviations in the predicted height, thus affecting the stratigraphic determination of the target aquifer. Specifically, corrections must be made based on the results of surface direct drilling.

[0024] Specifically, the compressive strength of hard rock strata is 40-80 MPa, that of medium-hard rock strata is 20-40 MPa, that of soft rock strata is 10-20 MPa, and that of extremely soft rock strata is <10 MPa.

[0025] In step 2, during the detection of the overburden failure law of the coal seam roof, the relationship between drilling fluid loss and hole depth, and abnormal drilling conditions are recorded. Abnormal drilling conditions refer to situations such as air intake, gas outburst, drill bit loss, and stuck drill bit.

[0026] In some embodiments, in step 2, the surface direct boreholes are arranged above the goaf, at a distance greater than 30m from the starting mining line and not less than 15m from the ending mining line. There are two direct boreholes, distributed inside the mining roadway, or multiple direct boreholes, some of which may be located in the middle of the working face. The development height of the water-conducting fracture zone is predicted using empirical formulas and analogies. Specifically, the empirical formula method refers to selection according to the "Specifications for the Retention of Coal Pillars and Coal Mining under Pressure in Buildings, Water Bodies, Railways and Main Shafts," while the analogy method refers to prediction based on the fracture-to-mining ratio obtained from measured data of adjacent working faces or adjacent mines. The fracture-to-mining ratio is the ratio of the development height of the water-conducting fracture zone to the thickness of the mined coal seam.

[0027] The height of the water-conducting fracture zone was predicted using both empirical formulas and analogy methods. The results of the two methods were mutually verified. If the results were consistent, the reliability of the prediction was improved. If there was a deviation, the actual drilling fluid loss data was used for correction. This provided a reliable basis for the final determination of the casing insertion depth and the injectability test layer.

[0028] In some embodiments, in step 2, a direct borehole is drilled on the ground to expose the first aquifer (marked as the i-th aquifer) and its bottom boundary above the influence range of the water-conducting fracture zone. The distance between the first aquifer (i-th aquifer) and the top boundary of the water-conducting fracture zone is less than or equal to 50m. Full-section casing is used for water shut-off above the first aquifer (i-th aquifer), and the target aquifer section is the area from the first aquifer (i-th aquifer) to its bottom boundary. During the injectionability test of the target aquifer section, the connectivity between the target aquifer section and the goaf is examined to determine whether the coal seam roof water inflow is involved, thus forming a preliminary aquifer grouting parameter adjustment plan.

[0029] The first aquifer (the i-th aquifer) is closest to the water-conducting fracture zone and has the strongest fissure connectivity with the goaf. It is the aquifer most likely to participate in roof water inrush and is also the layer where the grouting slurry is most likely to diffuse along the fissure. Conducting an injection feasibility test here is representative and engineering-specific.

[0030] The purpose of performing full-section casing sealing above the first aquifer (the i-th aquifer) is to strictly limit the injectability test to the target aquifer section and avoid interference from the upper formations with the test results.

[0031] The injectability test refers to conducting grouting parameter adjustment tests in the exposed aquifer section to develop a preliminary aquifer grouting parameter adjustment plan, such as grout type, grout density, grouting flow rate, and grouting pressure. This forms preliminary guiding experience for aquifer grouting modification. Connectivity verification involves placing markers on the ground and observing their appearance at the underground water outlet to determine the connectivity between the aquifer and the goaf. It can also determine whether the aquifer is involved in the coal seam roof water inflow.

[0032] Step 2 drilling process: When the first aquifer (i-th aquifer) above the expected water-conducting fracture zone is exposed by direct drilling on the surface of the goaf, full-section casing is installed above the first aquifer (i-th aquifer) for water sealing. When the bottom boundary of the aquifer is exposed by direct drilling on the surface, an injection test is conducted, and the connectivity between the target aquifer section and the goaf is verified at the same time.

[0033] The injectability test and connectivity test together address whether the target aquifer section can be effectively sealed by grouting, thus determining the feasibility of subsequent grouting of the cutoff structure, and whether the target aquifer section actually participated in the roof water inflow, thus determining the necessity of setting up the subsequent cutoff structure. This provides measured data support for the design of the cutoff structure in step 3, making the design of the cutoff structure more targeted.

[0034] In some embodiments, in step 3, surface directional drilling is carried out outside the influence range of the goaf. The surface directional drilling includes a first-level hole section, a second-level hole section, and a third-level hole section. The first-level hole section is followed by a first-level casing that penetrates into the stable bedrock section for no less than 5m. The second-level hole section is followed by a second-level casing that extends to the top plate of the target aquifer section. The third-level hole section is a bare hole.

[0035] Specifically, in step 3, when drilling the third-level hole in the ground, first drill the first-level hole section, then install the first-level casing, then drill the second-level hole section inside the first-level casing, install the second-level casing, and continue drilling the third-level hole section inside the second-level casing.

[0036] The primary casing extends at least 5 meters into the stable bedrock section, isolating the loose surface layer and shallow strata to prevent borehole instability. The secondary casing extends to the top of the target aquifer section, isolating all strata above the target aquifer section and strictly limiting grouting operations to the target cutoff layer. The tertiary borehole is drilled into the target aquifer section as a grouting channel connecting to the cutoff layer.

[0037] Specifically, the diameter of the first-stage borehole is 311mm, the diameter of the first-stage casing is 273mm, the diameter of the second-stage borehole is 243.3mm, the diameter of the second-stage casing is 219mm, and the diameter of the third-stage borehole is 152mm.

[0038] In some embodiments, in step 3, the contact relationship includes: the average thickness of the aquifer is less than 40m, and the water-conducting fracture zone enters or completely penetrates the aquifer. In this case, a cutoff wall structure is constructed at the edge of the goaf through directional drilling on the ground. Groundwater within the aquifer can flow downwards into the goaf through the vertical channels formed by the fracture zone. At the same time, groundwater within the lateral range of the aquifer continuously replenishes the fracture zone. Lateral replenishment is the main mechanism for maintaining the continuous inflow of water into the roof. Therefore, constructing a cutoff wall structure at the edge of the goaf, and forming a cutoff wall after grouting and sealing, can cut off the lateral replenishment path.

[0039] In some embodiments, such as Figure 1As shown, multiple first horizontal branch holes arranged in the target aquifer section by directional drilling form a cutoff wall structure. One or more cutoff wall structures are set around the working face according to the aquifer runoff pattern. The multiple first horizontal branch holes are located in the same vertical plane, with a vertical spacing of 10-20m between adjacent first horizontal branch holes. Multiple cutoff wall structures are set up by moving the plane position according to the grouting effect, with the multiple first horizontal branch holes of adjacent cutoff wall structures arranged vertically in a staggered manner.

[0040] Specifically, three first horizontal branch holes are arranged in the same vertical plane, with a vertical spacing of 15m between adjacent first horizontal branch holes. After grouting in the first horizontal branch holes, a grouting consolidation body is formed that continuously covers the thickness of the aquifer in the vertical direction.

[0041] For example, when two intercepting wall structures are installed, the first branch holes of the two intercepting wall structures are staggered vertically. For instance, the first branch hole at the upper part of the first intercepting wall structure is located above the first branch hole at the upper part of the second intercepting wall structure, the first branch hole in the middle part of the first intercepting wall structure is located above the first branch hole in the middle part of the second intercepting wall structure, and the first branch hole at the lower part of the first intercepting wall structure is located above the first branch hole at the lower part of the second intercepting wall structure.

[0042] The selection of the two water interception structures (water interception wall and water interception plate) is based on the water inflow mechanism. The blocking position directly acts on the water inflow channel rather than passively intercepting it, so the water interception effect is good and the project reliability is higher.

[0043] In some embodiments, in step 3, the contact relationship includes: the average thickness of the aquifer is greater than 40m and less than 60m, and the top of the water-conducting fracture zone extends into the bottom of the aquifer. In this case, a cutoff structure is constructed by directional drilling at the top of the water-conducting fracture zone and the bottom of the aquifer through micro-fractures. Since the water-conducting fractures do not penetrate the aquifer, groundwater within the lateral range of the aquifer cannot migrate laterally on a large scale through the fracture zone. However, a fissure seepage surface exists between the bottom of the aquifer and the top of the fracture zone, and groundwater seepage downwards through this seepage surface is the main mechanism of water inrush. Constructing a cutoff structure at the top of the water-conducting fracture zone and the bottom of the aquifer, and forming a cutoff plate after grouting, can horizontally seal the seepage channels.

[0044] In some embodiments, in step 3, the contact relationship includes: if the average thickness of the aquifer is greater than 40m and less than 60m, and the top of the water-conducting fracture zone enters the middle of the aquifer, then a cutoff plate structure is constructed at the top of the water-conducting fracture zone and the micro-fracture zone where the aquifer is damaged through directional drilling on the ground. Simultaneously, a cutoff wall structure is constructed. After grouting, the cutoff wall structure and the cutoff plate structure form a grout-sealed structure. The cutoff wall structure forms a cutoff wall after grouting, and the cutoff plate structure forms a cutoff plate after grouting. The connection between the cutoff plate and the cutoff wall forms a closed state. The cutoff plate can horizontally block the seepage channel, and the cutoff wall can cut off the lateral recharge path and block the lateral seepage channel, thereby forming a three-dimensional, all-round sealing to ensure the control of water inrush from the composite aquifer at the top.

[0045] In some embodiments, such as Figure 2 As shown, multiple second-horizontal branch holes arranged by ground directional drilling form a water-cutting plate structure. The spacing between adjacent second-horizontal branch holes is 30-50m, and the coverage area of ​​the water-cutting plate structure is greater than or equal to the influence area of ​​the working face goaf. This ensures that the bottom seepage surface is completely covered, leaving no dead corners for leakage. The upward or downward movement of the water-cutting plate structure is determined based on the grouting and water-stopping effect, and / or multiple water-cutting plate structures are set up. That is, the upward or downward movement of the water-cutting plate structure is determined based on the grouting and water-stopping effect; or, multiple water-cutting plate structures are set up based on the grouting and water-stopping effect; or, the upward or downward movement of the water-cutting plate structure is determined based on the grouting and water-stopping effect, and multiple water-cutting plate structures are set up. This is to address the situation where uneven development of micro-cracks leads to insufficient local sealing.

[0046] Specifically, the distance between adjacent second horizontal branch holes is 40m.

[0047] In some embodiments, the ground grouting system includes grouting equipment, pumping equipment, grouting connection pipelines, grouting pressure testing instruments, grouting parameter adjustment control console, and grouting materials. Grouting materials include ordinary silicate cement, ultrafine cement, clay, fly ash, quick-setting agent, composite sealing material, coarse (fine) sand, gravel, and mica. Grouting parameters include grout discharge rate, grout density, grout setting time, grout solids ratio, and the amount of sealing material added. The system can be flexibly selected based on the aquifer geological conditions and grouting effect. For example, wide fissures can be quickly filled with coarse-grained materials before grouting, while small fissures can be permeated and consolidated using ultrafine cement or chemical grout. Quick-setting agents are used to control the grout diffusion range under high water pressure conditions. The synergistic use of multiple materials helps improve the compactness and overall integrity of the cutoff structure.

[0048] In some embodiments, in step 4, the grouting process for plugging leaks is as follows: during the ground directional drilling construction in step 3, if the drilling fluid leakage is greater than 5 m³ / h, grouting is initiated. During the grouting process of the cutoff wall and cutoff slab, at least one of the following is adjusted according to the leakage situation: grouting discharge rate, grout density, grout setting time, grout solid ratio, and plugging material.

[0049] Different leakage rates correspond to different degrees of fracture development, channel width, and connectivity. Adjusting grout parameters according to the leakage situation can ensure that the grout can enter water-conducting fractures, mining-induced fractures, and fractured zones without excessive loss, thereby improving the matching degree between the grout and the leakage channels.

[0050] When leakage is significant, the grouting flow rate can be increased, the grout density or solids ratio can be increased, and a sealing material with a stronger particle size distribution can be selected to allow the grout to quickly fill large cracks or strong water-conducting channels. When leakage is small, the flow rate can be reduced, and a grout with better fluidity can be used for penetration into fine cracks. This can reduce the blind diffusion and waste of grout and improve the effective filling rate.

[0051] By adjusting the setting time and solids ratio, the grout can be made to set, accumulate, and cement within the target stratum in a timely manner, forming a continuous, stable, and dense sealing body. This prevents the grout from being carried away by groundwater or leakage channels before it has solidified, thus facilitating the formation of reliable cutoff walls and barriers. For areas with high leakage, using fast-setting grout with a high solids ratio or containing plugging particles can shorten the grout's flow distance in fractures, reduce its diffusion into non-target areas, and lower the risk of it entering goafs, deep aquifers, or other undesigned channels. Dynamic grout adjustment can create tiered sealing based on the leakage characteristics of different strata, weakening or severing the hydraulic connections between aquifers and between aquifers and goafs.

[0052] After the grouting parameters are matched with the leakage status, the water-conducting fracture zone and its connected water-bearing channels can be effectively sealed, reducing the amount of water supplied from the roof aquifer to the goaf, thereby reducing the mine's drainage burden. Adjusting the parameters according to the real-time leakage situation can promptly respond to sudden large leakage, sudden fracture penetration, or abnormal grout diffusion, avoiding problems such as borehole loss of control, borehole collapse, and abnormal increase in grouting pressure, thus improving the stability and safety of surface directional drilling grouting construction.

[0053] In step 4, if the drilling fluid loss is less than 10m³ 3 The discharge rate is 60-500 L / min, using single-component fly ash slurry. After the grouting pressure reaches the aquifer water pressure, cement-fly ash slurry is selected, with a slurry density of 1.1-1.4 g / cm³. 3 The grouting process ends once the grouting pressure reaches 1.5 times the aquifer water pressure; if the drilling fluid loss exceeds 10m³... 3 / h less than 30m 3With a discharge rate of 60-800 L / min, fine sand with a particle size of less than 1 mm is used for filling gaps using mine water. After the grouting pressure reaches the aquifer water pressure, cement-fly ash grout is selected, with a grout density of 1.1-1.5 g / cm³. 3 The grouting process ends once the grouting pressure reaches 1.5 times the aquifer water pressure; if the drilling fluid loss exceeds 30m³... 3 / h less than 60m 3 With a discharge rate of 60-1000 L / min, fine sand with a particle size of less than 1 mm is used for filling gaps by conveying mine water. After the grouting pressure reaches 0.5 times the aquifer water pressure, cement-fly ash slurry is selected, mixed with sawdust with a particle size of less than 1 mm. The sawdust dosage is 50-100 kg / h, and the slurry density is 1.1-1.5 g / cm³. 3 The grouting process ends once the grouting pressure reaches 1.5 times the aquifer water pressure; if the drilling fluid loss exceeds 60m³... 3 With a discharge rate of 60-1600 L / min, mine water is used to fill cracks with gravel with a particle size of less than 0.5-1.5 cm. After water returns from the wellhead, fine sand with a particle size of less than 1-3 mm is used to seal the cracks. After the grouting pressure reaches 0.5 times the aquifer water pressure, cement-fly ash slurry is selected, mixed with sawdust with a particle size of less than 1 mm. The sawdust dosage is 50-200 kg / h, and the slurry density is 1.1-1.5 g / cm³. 3 The grouting process ends when the grouting pressure reaches 1.5 times the water pressure of the aquifer.

[0054] By enabling the grouting process to adapt to the dynamic changes in leakage conditions caused by mining fractures and composite aquifers, the effective utilization rate of grout and the forming quality of the sealing body are improved, enhancing the water-blocking reliability of the cutoff wall and cutoff plate, thereby effectively weakening the supply of the roof composite aquifer to the goaf and reducing the risk of mine water inrush.

[0055] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0056] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0057] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0058] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0059] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0060] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A combined drilling and grouting process for water plugging in the composite aquifer of the coal seam roof after mining, characterized in that, Includes the following steps: Step 1: Construct a geological model of the composite aquifer of coal seam and roof; Step 2: Drill direct boreholes on the surface above the goaf to detect the failure pattern of the overlying strata of the coal seam roof caused by mining, obtain the development height of the water-conducting fracture zone, the vertical spatial development characteristics of the mining fractures, and the contact relationship between the water-conducting fracture zone and the aquifer in the roof, and select the target aquifer section for injection capability test; Step 3: Construct directional boreholes on the ground outside the affected area of ​​the goaf, and build a water-cutting structure based on the aforementioned contact relationship; Step 4: Establish a ground grouting system and inject grout into the water-blocking structure constructed in Step 3 according to the leakage-stopping grouting process.

2. The combined drilling and grouting water plugging process for the composite aquifer in the post-mining roof of the coal seam according to claim 1, characterized in that, In step 1, the aquifer above the coal seam roof is marked as the i-th aquifer from bottom to top, and the overlying lithology is classified according to the saturated uniaxial compressive strength of the rock: hard, medium hard, soft and extremely soft. The development height of the water-conducting fracture zone is predicted by empirical formula method and analogy method.

3. The combined drilling and grouting water plugging process for the composite aquifer in the post-mining roof of the coal seam according to claim 1, characterized in that, In step 2, a direct borehole is drilled on the ground to expose the first aquifer and its bottom boundary above the influence range of the water-conducting fracture zone. The first aquifer is less than or equal to 50m from the top boundary of the water-conducting fracture zone. Full-section casing is used for water stoppage above the first aquifer. The target aquifer section is the area from the first aquifer to the bottom boundary of the aquifer. When conducting an injection capability test on the target aquifer section, the connectivity between the target aquifer section and the goaf is checked to determine whether the coal seam roof water inflow is involved by the target aquifer section, thus forming a preliminary aquifer grouting parameter adjustment plan.

4. The combined drilling and grouting water plugging process for the composite aquifer in the post-mining roof of the coal seam according to claim 1, characterized in that, In step 3, the ground directional drilling includes a first-stage, a second-stage, and a third-stage borehole. The first-stage borehole has a first-stage casing that extends at least 5 meters into the stable bedrock. The second-stage borehole has a second-stage casing that extends to the top of the target aquifer. The third-stage borehole is a bare borehole.

5. The combined drilling and grouting water plugging process for the composite aquifer in the post-mining roof of a coal seam according to claim 1, characterized in that, In step 3, the contact relationship includes: if the average thickness of the aquifer is less than 40m and the water-conducting fracture zone enters or completely penetrates the aquifer, then a water-cutting wall structure is constructed at the edge of the goaf through directional drilling on the ground.

6. The combined drilling and grouting water plugging process for the composite aquifer in the post-mining roof of the coal seam according to claim 5, characterized in that, The ground directional drilling arranges multiple first horizontal branch holes in the target aquifer section to form the cutoff wall structure. According to the aquifer runoff pattern, one or more cutoff wall structures are set around the working face. The multiple first horizontal branch holes are located in the same vertical plane, and the vertical distance between adjacent first horizontal branch holes is 10-20m. Multiple water-cutting wall structures are set up according to the grouting effect and the plane position is moved. Multiple first horizontal branch holes of adjacent water-cutting wall structures are arranged vertically and horizontally in an alternating manner.

7. The combined drilling and grouting water plugging process for the composite aquifer in the post-mining roof of a coal seam according to claim 1, characterized in that, In step 3, the contact relationship includes: if the average thickness of the aquifer is greater than 40m and less than 60m, and the top of the water-conducting fracture zone enters the bottom of the aquifer, then a water-cutting plate structure is constructed at the top of the water-conducting fracture zone and the micro-fracture zone at the bottom of the aquifer through directional drilling on the ground; if the average thickness of the aquifer is greater than 40m and less than 60m, and the top of the water-conducting fracture zone enters the middle of the aquifer, then a water-cutting plate structure is constructed at the top of the water-conducting fracture zone and the micro-fracture zone where the aquifer is damaged through directional drilling on the ground, and a water-cutting wall structure is constructed at the same time. The water-cutting wall structure and the water-cutting plate structure form a grouting closed shape after grouting.

8. The combined drilling and grouting water plugging process for the composite aquifer in the post-mining roof of the coal seam according to claim 7, characterized in that, Multiple second horizontal branch holes arranged by ground directional drilling form the water-cutting plate structure. The spacing between adjacent second horizontal branch holes is 30-40m. The coverage area of ​​the water-cutting plate structure is greater than or equal to the influence area of ​​the goaf in the working face. The water-cutting plate structure is moved up or down according to the grouting and water-blocking effect, and / or multiple water-cutting plate structures are set.

9. The combined drilling and grouting water plugging process for the composite aquifer in the post-mining roof of a coal seam according to claim 1, characterized in that, In step 4, the grouting process is as follows: during the ground directional drilling construction in step 3, if the drilling fluid loss is greater than 5 m³ / h, grouting is started, and at least one of the following is adjusted according to the loss: grouting flow rate, grout density, grout setting time, grout solid ratio, and grouting material.

10. The combined drilling and grouting water plugging process for the composite aquifer in the post-mining roof of a coal seam according to claim 9, characterized in that, In step 4, if the drilling fluid loss is less than 10m³ 3 The discharge rate is 60-500 L / min, using single-component fly ash slurry. After the grouting pressure reaches the aquifer water pressure, cement-fly ash slurry is selected, with a slurry density of 1.1-1.4 g / cm³. 3 The grouting process ends once the grouting pressure reaches 1.5 times the aquifer water pressure; if the drilling fluid loss exceeds 10m³... 3 / h less than 30m 3 With a discharge rate of 60-800 L / min, fine sand with a particle size of less than 1 mm is used for filling gaps by conveying mine water. After the grouting pressure reaches the aquifer water pressure, cement-fly ash grout is selected, with a grout density of 1.1-1.5 g / cm³. 3 The grouting process ends once the grouting pressure reaches 1.5 times the aquifer water pressure; if the drilling fluid loss exceeds 30m³... 3 / h less than 60m 3 With a discharge rate of 60-1000 L / min, fine sand with a particle size of less than 1 mm is used for filling gaps by conveying mine water. After the grouting pressure reaches 0.5 times the aquifer water pressure, cement-fly ash slurry is selected, mixed with sawdust with a particle size of less than 1 mm. The sawdust dosage is 50-100 kg / h, and the slurry density is 1.1-1.5 g / cm³. 3 The grouting process ends once the grouting pressure reaches 1.5 times the aquifer water pressure; if the drilling fluid loss exceeds 60m³... 3 With a discharge rate of 60-1600 L / min, mine water is used to fill cracks with gravel with a particle size of less than 0.5-1.5 cm. After water returns from the wellhead, fine sand with a particle size of less than 1-3 mm is used to seal the cracks. After the grouting pressure reaches 0.5 times the aquifer water pressure, cement-fly ash slurry is selected, mixed with sawdust with a particle size of less than 1 mm. The sawdust dosage is 50-200 kg / h, and the slurry density is 1.1-1.5 g / cm³. 3 The grouting process ends when the grouting pressure reaches 1.5 times the water pressure of the aquifer.

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