A coal seam roof local water-permeable skylight ground exploration treatment method

Abstract

The application discloses a coal seam roof local water-permeable skylight ground exploration treatment method, which realizes "from line to surface" regional fine positioning of a coal seam roof water-resisting soil layer missing area by means of a construction directional main hole and a plurality of branch holes. In this way, the problems of great drilling hole position arrangement blindness, great drilling engineering quantity, great coring engineering quantity, many invalid footage and low efficiency and the like of traditional "point position" and "pairing hole" type drilling and coring positioning of a soil layer missing area specific range are overcome. Meanwhile, the soil layer missing area is grouted and reconstructed by means of the construction directional main hole and the plurality of branch holes, so that the missing area is ensured not to exist, advanced grouting treatment of a concentrated water-permeable skylight in a coal seam mining process and control of a ground loose water-bearing layer gushing water and sand collapse and an underground water resource leakage source are realized, and the method is suitable for large-scale use and popularization in industry.

Description

Technical Field

[0001] This invention belongs to the field of mine water control and groundwater resource protection, specifically relating to a method for surface exploration and treatment of local permeable skylights in the roof of coal seams. Background Technology

[0002] As a core area for coal resource development in my country, the Shaanxi-Gansu-Ningxia coal base has numerous soil layer gaps distributed throughout its mining areas. Accurate exploration of these gaps is fundamental to the efficient prevention and control of water hazards to the coal seam roof and the protection of groundwater resources in the near-surface water-rich loose layers. Because these soil layer gaps are typically concealed spatially, their planar boundaries are irregular. Traditional methods involve vertical drilling to locate the specific extent of these gaps by coring from points and then coring the entire borehole section. This process, where adjacent boreholes have soil layers but one does not, gradually approximates the boundary of the gap. This approach often suffers from problems such as haphazard borehole placement, large drilling and coring volumes, numerous ineffective drilling passes through various strata above the soil layer, low efficiency, and the possibility of overlooking areas. Consequently, it fails to provide a fundamental basis for preventing water hazards from permeable windows in soil layer gaps and protecting groundwater resources. Summary of the Invention

[0003] The purpose of this invention is to provide a method for detecting and treating localized water-permeable skylights in the roof of coal seams, so as to solve the problems of low detection efficiency and missed areas in the existing technology.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] A method for surface exploration and remediation of localized water-permeable skylights in coal seam roofs includes the following steps:

[0006] Step 1: Collect geological and hydrogeological borehole data of the area to be treated, and preliminarily delineate the area with missing soil layers as the study area;

[0007] Step 2: Draw a contour map of the top elevation of the soil layer in the study area to identify a set of long axes of potential soil layer missing areas;

[0008] Step 3: Draw contour maps of the thickness of the roof soil layer of the coal seam in the study area, and then identify a set of long axes of potential soil layer missing areas;

[0009] Step 4: Based on the long axes of the two sets of potential soil layer missing areas obtained in Step 2 and Step 3, draw the equidistant lines between the long axes of these two sets of potential soil layer missing areas, and determine the actual long axis of the potential soil layer missing area based on the equidistant lines;

[0010] Step 5: Design a ground directional drilling master hole upstream of the top boundary elevation of the soil layer in the soil-covered area of ​​the study area, along the actual long axis direction of the potential soil layer missing area determined in Step 4.

[0011] Step 6: Perform directional drilling according to the designed ground directional drilling main hole. During the directional drilling process, continuously retrieve rock cuttings. Determine the source type of the rock cuttings each time they are retrieved.

[0012] If the source type of the rock cuttings changed from soil to loose rock, the stratum of the surface directional drilling main borehole was adjusted and drilling continued while continuously retrieval rock cuttings. The source type of the rock cuttings was determined for each retrieval until the surface directional drilling main borehole was formed.

[0013] If the source of the rock cuttings retrieved during directional drilling changes from loose rock layers to soil layers, drilling should be stopped and the borehole already formed should be designated as the main borehole for surface directional drilling.

[0014] Step 7: Design and construct directional branch holes sequentially from the center of the main directional drilling hole on the ground outwards. The closed area formed by all the sequentially constructed directional branch holes is the actual soil layer missing area.

[0015] Step 8: Drill the directional branch holes according to the design sequence. During the drilling process, grouting modification is carried out simultaneously to achieve the treatment of the concentrated permeable skylights in the coal seam roof and the control of the source of roof water inflow.

[0016] The present invention also has the following features:

[0017] Furthermore, in step 2, when drawing the top elevation contour map of the soil layer in the study area, the top elevation contour map of the soil layer is drawn by interpolation with a spacing of 1 to 10 m between the contour lines. A set of potential soil layer missing area long axes are identified by connecting the points of maximum curvature of each contour line.

[0018] Furthermore, in step 3, when drawing the contour map of the thickness of the soil layer on the roof of the coal seam in the study area, the contour map of the thickness of the soil layer on the roof of the coal seam in the study area is drawn by interpolation with a thickness contour line spacing of 1 to 10 m.

[0019] The contour line with the smallest value in the contour map of the soil layer thickness of the coal seam roof is identified as the long axis of the potential soil layer missing area.

[0020] Furthermore, in step 6, during the directional drilling process of the main borehole based on the design, rock scooping is performed every 1m of advance.

[0021] Furthermore, step 6 includes the following sub-steps:

[0022] Step 61: Perform one directional drilling advance along the designed ground directional drilling main hole and perform one rock retrieval cut to determine whether the ground directional drilling main hole has been formed;

[0023] If it has already formed, stop drilling;

[0024] If it does not form, proceed to step 62;

[0025] Step 62: Determine the source type of the rock fragments retrieved this time;

[0026] If the rock fragments retrieved this time are from loose rock strata, then proceed to step 63;

[0027] If the rock fragments retrieved this time are from soil layers, then proceed to step 64;

[0028] Step 63: Pause directional drilling, design a vertical coring borehole at the corresponding ground location, and perform vertical drilling to obtain a core to the bedrock layer; determine whether there is a soil layer based on the coring results;

[0029] If there is a soil layer, proceed to step 65;

[0030] If there is no soil layer, the ground position corresponding to the position when directional drilling was paused will be taken as the upstream boundary of the soil layer missing area, and the process will return to step 61.

[0031] Step 64: Stop drilling, designate the existing borehole as the main borehole for surface directional drilling, and take the ground position corresponding to the rock cut where the soil source was retrieved as the downstream boundary of the soil missing area.

[0032] Step 65: After redesigning the near-horizontal section of the ground directional drilling main hole according to the thickness of the soil layer, return to step 61.

[0033] Furthermore, in step 61, the advance of each directional drilling operation is 1m;

[0034] In step 65, when redesigning the near-horizontal section of the ground directional drilling main hole, the near-horizontal section of the directional drilling is readjusted based on the soil layer thickness confirmed by the core sampling of the vertical borehole, with the middle position of the soil layer as the reference.

[0035] Furthermore, in step 7, directional branch holes are designed and constructed sequentially from the center of the directional drilling main hole outwards with a near-horizontal section hole spacing of 40-60m, and drilling is carried out using the methods in steps 5 and 6;

[0036] By sequentially connecting the starting points of the unretrieved soil layer and the starting points of the retrieved soil layer within the range of each directional branch hole, the enclosed area formed is the actual soil layer missing area.

[0037] Furthermore, in step 8, if the rock cutting starting point is not found in a directional branch hole, during the continued directional drilling process, cement single-liquid grout or mixed grout is used to carry out segmented grouting at intervals of 20-50m until the grouting end standard is reached.

[0038] After the previous grouting is completed, multiple grouting sections will continue to be carried out in 20-50m increments. Each grouting section will be completed after the grouting completion standard is met, and drilling and grouting will stop when the directional branch hole reaches the soil layer rock cut.

[0039] By using the above method to traverse each directional branch hole, grouting modification is completed, thereby achieving the treatment of concentrated permeable skylights in the coal seam roof and the control of the source of roof water inflow.

[0040] Furthermore, the mixing slurry in step 8 is a cement-fly ash mixture or a cement-clay mixture;

[0041] The water-to-solid ratio is 0.8-1.1.

[0042] Furthermore, the grouting end standard in step 8 is: after reaching the maximum grouting pressure standard, reduce the pump flow rate to 60L / min and maintain it for 30min;

[0043] The maximum grouting pressure P is determined using the following formula:

[0044] P = (1.5 - 2) * H / 100

[0045] Where H represents the burial depth of the grouting section, in meters.

[0046] Compared with the prior art, the present invention has the following technical effects:

[0047] The present invention provides a method for surface exploration and remediation of localized permeable roof windows in coal seams. By constructing a directional main borehole and several branch boreholes, it achieves precise "line-to-surface" localization of areas lacking the impermeable soil layer in the coal seam roof. This overcomes numerous problems associated with traditional methods that use vertical drilling to locate the specific extent of soil layer deficiencies through "point-to-point" and "hole-to-hole" coring. These problems include highly arbitrary borehole placement, large drilling and coring workloads, numerous ineffective advances, and low efficiency. Simultaneously, the constructed directional main borehole and several branch boreholes are used to grout and remediate the demarcated soil layer deficiencies, ensuring no areas are missed. This method enables advanced grouting remediation of concentrated permeable roof windows during coal seam mining and source control of water inrush and sand erosion in loose surface aquifers, as well as groundwater resource leakage. It is suitable for large-scale industrial application and promotion. Attached Figure Description

[0048] Figure 1 This is a map showing the distribution of areas with missing impermeable soil layers in a certain mining area of ​​a certain region, based on existing technology.

[0049] Figure 2This is a distribution map of borehole coring exploration projects in areas with missing soil layers in existing technologies;

[0050] Figure 3 and 4 This is a schematic diagram illustrating the preliminary delineation of the spatial range of the soil layer missing area based on the actual borehole spatial distribution of the soil layer in one embodiment of the present invention.

[0051] Figure 5 This is a schematic diagram of the major axis of the soil layer missing area determined by equidistant lines in one embodiment of the present invention;

[0052] Figure 6 This is a schematic diagram of directional drilling rock cutting identification and vertical drilling coring confirmation in one embodiment of the present invention;

[0053] Figure 7 This is a schematic diagram of directional exploration and positioning of a soil layer missing area in one embodiment of the present invention;

[0054] Figure 8 This is a schematic diagram of directional exploration and grouting treatment of soil layer missing areas in one embodiment of the present invention;

[0055] Figure 9 This is a schematic diagram of directional exploration and grouting treatment of permeable skylights in soil missing areas in one embodiment of the present invention. Detailed Implementation

[0056] It should be noted that, unless otherwise specified, all methods in this invention are methods known in the prior art.

[0057] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0058] like Figure 1 As shown, the Shaanxi coal base, as the core area for coal resource development in my country, has numerous soil layer missing areas distributed throughout the mining area. Detailed exploration of these soil layer missing areas is fundamental to achieving efficient prevention and control of water hazards to the coal seam roof and the protection of groundwater resources in the near-surface water-rich loose layer. Because these soil layer missing areas are all concealed spatially (covered by the loose surface layer), their planar boundaries are relatively irregular (the erosion windows created by rainwater gullies generally exhibit an approximately ellipsoidal strip-like distribution pattern).

[0059] like Figure 2As shown, traditional methods use vertical drilling on the ground to locate the specific extent of soil layer gaps by coring in a "point-to-point" or "hole-to-hole" manner (by coring the entire borehole section to analyze whether soil layer gaps exist, the boundary of the gap area can only be gradually confirmed when one adjacent borehole has soil and the other does not). This method often suffers from problems such as blind placement of boreholes, large drilling workload, large coring workload, many ineffective drilling steps (all boreholes need to penetrate the upper strata of the soil layer), low efficiency, and the possibility of overlooking areas. It is difficult to provide a basic basis for the prevention and control of water damage from permeable windows in soil layer gap areas and the protection of groundwater resources.

[0060] In view of the above situation, a specific embodiment of the present invention is given:

[0061] A method for surface exploration and remediation of localized water-permeable skylights in coal seam roofs includes the following steps:

[0062] Step 1: Collect geological and hydrogeological borehole data of the area to be treated, and preliminarily delineate the areas with missing soil layers as the study area, such as... Figure 3 and 4 As shown;

[0063] Step 2: Draw a contour map of the top elevation of the soil layer in the study area to identify a set of long axes of potential soil layer missing areas;

[0064] Step 3: Draw a contour map of the thickness of the soil layer on the roof of the coal seam in the study area. Using the contour line with the smallest value as the reference, identify a set of long axes of potential soil layer missing areas.

[0065] Step 4: Based on the long axes of the two sets of potential soil layer missing areas obtained in Step 2 and Step 3, draw the equidistant lines between the long axes of these two sets of potential soil layer missing areas, and determine the actual long axis of the potential soil layer missing area based on the equidistant lines;

[0066] The soil layers in coal mining areas are generally lacustrine sedimentary strata, similar to a calm lake surface. Under uneroded geological conditions, their thickness and elevation distribution are relatively flat and stable. When a local area is subjected to geological erosion, the strata will become severely thinner, accompanied by a significant decrease in elevation. Therefore, with sufficient geological borehole information, the extent of the skylight area can be preliminarily delineated based on the decrease in elevation or thickness. However, geological boreholes in general mining areas are limited, and the distribution of strata on the top surface of the soil layer is unstable due to geological weathering, wind erosion, and scouring. It is difficult to delineate the area using only one indicator, such as elevation or thickness. Therefore, this case fully utilizes the relatively scarce geological borehole information and identifies the main axis of the skylight area by comprehensively considering both elevation and thickness factors, which has a higher scientific basis and accuracy.

[0067] Step 5: Design a ground directional drilling master hole upstream of the top boundary elevation of the soil layer in the soil-covered area of ​​the study area, along the actual long axis direction of the potential soil layer missing area determined in Step 4.

[0068] Upstream of the top elevation of the soil layer in the soil-covered area, a ground directional drilling main borehole is designed along the long axis of the potential soil layer missing area determined by analysis. Based on the distribution of soil layer thickness contour lines, the ground opening location is located in the confirmed covered area, and the design of the near-horizontal directional section below the surface needs to encounter geological boreholes of the previously exposed soil layer outside the initially delineated soil layer missing area. From there, directional drilling continues along the potential long axis.

[0069] Step 6: Perform directional drilling according to the designed ground directional drilling main hole. During the directional drilling process, continuously retrieve rock cuttings. Determine the source type of the rock cuttings each time they are retrieved.

[0070] If the source type of the rock cuttings changed from soil to loose rock, the stratum of the surface directional drilling main borehole was adjusted and drilling continued while continuously retrieval rock cuttings. The source type of the rock cuttings was determined for each retrieval until the surface directional drilling main borehole was formed.

[0071] If the source of the rock cuttings retrieved during directional drilling changes from loose rock layers to soil layers, drilling should be stopped and the borehole already formed should be designated as the main borehole for surface directional drilling.

[0072] Step 7: Design and construct directional branch holes sequentially from the center of the main directional drilling hole on the ground outwards. The closed area formed by all the sequentially constructed directional branch holes is the actual soil layer missing area.

[0073] Step 8: Drill the directional branch holes according to the design sequence. During the drilling process, grouting modification is carried out simultaneously to achieve the treatment of the concentrated permeable skylights in the coal seam roof and the control of the source of roof water inflow.

[0074] Furthermore, in step 2, based on the actual borehole stratigraphic interface elevation information of the soil layer revealed in the geological and hydrogeological borehole data of the area to be treated, a contour map of the top boundary elevation of the soil layer in the missing soil layer area is drawn by interpolation with a contour line spacing of 1 to 10 m.

[0075] Based on the concavity and convexity of the contour lines at the top interface of the soil layer, and according to the increasing trend of convexity or decreasing trend of concaveness, the long axis of potential soil layer missing areas is identified by connecting the points of maximum curvature of each contour line.

[0076] Because the top surface of soil layers that have not been geologically eroded is relatively flat, while the elevation of soil layer interfaces tends to decrease or even disappear in areas affected by geological erosion, the elevation contour lines of the top soil layer interface can be used to determine whether the top surface is concave or convex, with a tendency to increase in the convex direction or decrease in the concave direction (e.g., ...). Figure 5 As shown in the figure, the long axis of potential soil layer missing areas is identified by connecting the points of maximum curvature of each contour line.

[0077] Furthermore, in step 3, based on the actual borehole stratum thickness information of the soil layer revealed in the geological and hydrogeological borehole data of the area to be treated, a contour map of the thickness of the roof soil layer in the coal seam of the mine area with soil layer missing area is drawn by interpolation with a contour line interval of 1 to 10m.

[0078] The contour line with the smallest value in the contour map of the soil layer thickness of the coal seam roof in the mine field is identified as the long axis of the potential soil layer missing area.

[0079] like Figure 5 As shown, draw an equidistant line between the long axis of the potential soil layer missing area obtained in step 3 and the long axis of the potential soil layer missing area obtained in step 3, and determine the actual long axis of the soil layer missing area based on the position of the equidistant line.

[0080] It should be noted that the soil layers in coal mining areas are generally lacustrine sedimentary strata, similar to a calm lake surface. Under uneroded geological conditions, their thickness and elevation distribution are relatively flat and stable. When a local area is subjected to geological erosion, the strata will become severely thinner, accompanied by a significant decrease in elevation.

[0081] Therefore, with sufficient geological borehole information, the extent of the skylight area can be initially delineated based on the decrease in elevation or the thinning of the soil thickness. However, geological boreholes in general mining areas are limited, and the strata distribution on the top surface of the soil layer is unstable due to geological weathering, wind erosion, and scouring, making it difficult to delineate the area using only elevation or thickness. Therefore, this embodiment makes full use of the relatively scarce geological borehole information and identifies the main axis of the skylight area by comprehensively considering both elevation and thickness factors, resulting in higher scientific basis and accuracy.

[0082] Specifically, in step 6, during the directional drilling process of the main borehole of the ground directional drilling according to the design, rock scooping is performed every 1m of advance.

[0083] Furthermore, in step 6, each time rock cuttings are retrieved, the stratum in which the drilling is located is determined by the rock cuttings.

[0084] If the rock cuttings are of the loose rock strata type, directional drilling should be suspended, and a vertical coring borehole should be designed at the corresponding ground location, and vertical drilling should be carried out to cor the bedrock layer.

[0085] If no soil layer is found during vertical drilling to the bedrock layer, the corresponding ground location is confirmed as the boundary of the soil-deficient area, and directional drilling continues until the directional main borehole is formed.

[0086] If there is a soil layer during the vertical drilling to the bedrock layer, the near-horizontal section of the directional drilling should be readjusted according to the thickness of the soil layer before continuing the directional drilling until the main directional borehole is formed.

[0087] If the rock cut is the source of soil, the corresponding ground location is used as the boundary of the soil-deficient area on the other side, and drilling is stopped.

[0088] During directional drilling of the main borehole, continuous rock cuttings are retrieved at 1-meter intervals. These rock cuttings are used to determine whether the drilled strata are soil. When the retrieved rock cuttings are found to be loose rock, directional drilling is paused. Using this ground location as the borehole position, a vertical coring borehole is designed to confirm the absence of surface soil. Coring is performed through this vertical borehole down to the bedrock layer. If no soil layer is found between the loose layer and the bedrock layer, this is confirmed as the boundary of the soil-deficient zone. Directional drilling then continues. When the retrieved rock cuttings change from a loose rock source to a soil source, this is confirmed as the boundary of the soil-deficient zone on the other side, and drilling is stopped. Figure 6 As shown.

[0089] If the above content is presented in the form of a flowchart, then step 6 specifically includes the following sub-steps:

[0090] Step 61: Perform one directional drilling advance along the designed ground directional drilling main hole and perform one rock retrieval cut to determine whether the ground directional drilling main hole has been formed;

[0091] If it has already formed, stop drilling;

[0092] If it does not form, proceed to step 62;

[0093] Step 62: Determine the source type of the rock fragments retrieved this time;

[0094] If the rock fragments retrieved this time are from loose rock strata, then proceed to step 63;

[0095] If the rock fragments retrieved this time are from soil layers, then proceed to step 64;

[0096] Step 63: Pause directional drilling, design a vertical coring borehole at the corresponding ground location, and perform vertical drilling to obtain a core to the bedrock layer; determine whether there is a soil layer based on the coring results;

[0097] If there is a soil layer, proceed to step 65;

[0098] If there is no soil layer, the ground position corresponding to the position when directional drilling was paused will be taken as the upstream boundary of the soil layer missing area, and the process will return to step 61.

[0099] Step 64: Stop drilling, designate the existing borehole as the directional drilling master hole, and take the ground position corresponding to the rock cut where the soil source is retrieved as the downstream boundary of the soil missing area.

[0100] Step 65: After redesigning the near-horizontal section of the ground directional drilling main hole according to the thickness of the soil layer, return to step 61.

[0101] Furthermore, in step 6, after readjusting the near-horizontal section of the directional drilling according to the soil thickness and continuing the directional drilling, rock retrieval is performed every 1m of advance.

[0102] When the rock fragments retrieved change from the original soil layer source to a loose rock layer source, directional drilling is suspended; and a vertical coring borehole is designed to confirm the absence of the ground soil layer, using the ground location as the borehole position, and the core is taken to the bedrock layer through the vertical borehole.

[0103] If there is no soil layer in the section from the loose layer to the bedrock layer, then the area is confirmed as the boundary of the soil-deficient zone, and directional drilling continues until the directional main borehole is formed;

[0104] If the rock cut is the source of soil, the corresponding ground location is used as the boundary of the soil-deficient area on the other side, and drilling is stopped.

[0105] Furthermore, in step 7, directional branch holes are designed and constructed sequentially from the center of the directional drilling main hole outwards with a near-horizontal section hole spacing of 40-60m, and drilling is carried out using the methods in steps 5 and 6;

[0106] By sequentially connecting the starting points of the unretrieved soil layer and the starting points of the retrieved soil layer within the range of each directional branch hole, the enclosed area formed is the actual soil layer missing area.

[0107] After the main directional borehole is constructed, directional branch boreholes are constructed sequentially from the center outwards, with a borehole spacing of 40-60m in the near-horizontal section (based on actual measurements, the directional grouting radius within the loose layer is 20-30m). This continues until both outermost branch boreholes are drilled into the soil layer (i.e., no loose rock cuttings are retrieved). By sequentially connecting the starting points of the unretrieved and retrieved soil rock cuttings within the area enclosed by the outermost branch boreholes on both sides, a closed loop is formed, which defines the specific extent of the soil layer deficiency zone. Figure 7 As shown.

[0108] Furthermore, in step 8, if the rock cutting starting point is not found in a directional branch hole, during the continued directional drilling process, cement single-liquid grout or mixed grout is used to carry out segmented grouting at intervals of 20-50m until the grouting end standard is reached.

[0109] After the previous grouting is completed, multiple grouting sections will continue to be carried out in 20-50m increments. Each grouting section will be completed after it meets the grouting completion standard, until the directional branch hole reaches the soil layer rock cut and drilling and grouting will stop.

[0110] By using the above method to traverse each directional branch hole, grouting modification is completed, thereby achieving the treatment of concentrated permeable skylights in the coal seam roof and the control of the source of roof water inflow. Figure 8 and 9 As shown.

[0111] Furthermore, the mixing slurry in step 8 is a cement-fly ash mixture or a cement-clay mixture;

[0112] The water-to-solid ratio is 0.8-1.1.

[0113] Furthermore, the grouting end standard in step 8 is: after reaching the maximum grouting pressure standard, reduce the pump flow rate to 60L / min and maintain it for 30min;

[0114] The maximum grouting pressure P is determined using the following formula:

[0115] P = (1.5 - 2) * H / 100

[0116] Where H represents the burial depth of the grouting section, in meters.

[0117] To ensure the effectiveness of grouting treatment in the skylight area, two conditions must be met: First, the hydrostatic pressure in the stratum must be overcome to ensure that the grout can diffuse within the stratum (generally, the hydrostatic pressure is equal to the burial depth of the stratum, hydrostatic pressure = H / 100), meaning the grouting pressure P must be greater than the hydrostatic pressure. Second, the grouting pressure cannot be too high, as this would cause the grout to diffuse to the surface, causing some environmental pollution. Therefore, based on the above two factors and combined with the successful experience of 1.5 to 2 times the hydrostatic pressure when performing directional grouting with a radius of 20 to 30 meters in loose strata, this standard for the termination of grouting pressure is given.

[0118] This embodiment describes a method for exploring and treating areas lacking the waterproof soil layer in the roof of coal seams using surface directional drilling and grouting modification technology. By constructing only one directional main borehole and several branch boreholes, it achieves precise "line-to-surface" localization of these areas. This overcomes numerous problems associated with traditional methods that use vertical drilling to locate the specific extent of soil layer deficiencies through "point-to-point" core sampling, resulting in highly indiscriminate borehole placement, large drilling and core sampling volumes, numerous ineffective advances, and low efficiency. Simultaneously, by using the constructed directional main borehole and several branch boreholes to perform grouting modification on the designated soil layer deficiencies, it achieves advanced grouting treatment of concentrated permeable windows during coal seam mining and source control of water inrush and sand erosion in loose surface aquifers, as well as groundwater resource leakage.

Claims

1. A method for surface exploration and remediation of localized water-permeable skylights in the roof of a coal seam, characterized in that, Includes the following steps: Step 1: Collect geological and hydrogeological borehole data of the area to be treated, and preliminarily delineate the area with missing soil layers as the study area; Step 2: Draw a contour map of the top elevation of the soil layer in the study area to identify a set of long axes of potential soil layer missing areas; Step 3: Draw contour maps of the thickness of the roof soil layer of the coal seam in the study area, and then identify a set of long axes of potential soil layer missing areas; Step 4: Based on the long axes of the two sets of potential soil layer missing areas obtained in Step 2 and Step 3, draw the equidistant lines between the long axes of these two sets of potential soil layer missing areas, and determine the actual long axis of the potential soil layer missing area based on the equidistant lines; Step 5: Design a ground directional drilling master hole upstream of the top boundary elevation of the soil layer in the soil-covered area of ​​the study area, along the actual long axis direction of the potential soil layer missing area determined in Step 4. Step 6: Perform directional drilling according to the designed ground directional drilling main hole. During the directional drilling process, continuously retrieve rock cuttings. Determine the source type of the rock cuttings each time they are retrieved. If the source type of the rock cuttings changed from soil to loose rock, the stratum of the main directional drilling hole was adjusted and drilling continued while continuously retrieval rock cuttings. The source type of the rock cuttings was determined each time they were retrieved. Until the main directional drilling borehole is formed on the ground; If the source of the rock cuttings retrieved during directional drilling changes from loose rock layers to soil layers, drilling should be stopped and the borehole already formed should be designated as the main borehole for surface directional drilling. Step 7: Design and construct directional branch holes sequentially from the center of the main directional drilling hole on the ground outwards. The closed area formed by all the sequentially constructed directional branch holes is the actual soil layer missing area. Step 8: Drill the directional branch holes according to the design sequence. During the drilling process, grouting modification is carried out simultaneously to achieve the treatment of the concentrated permeable skylights in the coal seam roof and the control of the source of roof water inflow.

2. The method for investigating and treating localized water-permeable skylights in the coal seam roof as described in claim 1, characterized in that, Step 2: When drawing the top elevation contour map of the soil layer in the study area, the top elevation contour map of the soil layer is drawn by interpolation with a spacing of 1 to 10 m. A set of potential soil layer missing area long axes are identified by connecting the points of maximum curvature of each contour line.

3. The method for investigating and treating localized water-permeable skylights in the coal seam roof as described in claim 1, characterized in that, Step 3: When drawing the contour map of the thickness of the soil layer on the roof of the coal seam in the study area, the contour map of the thickness of the soil layer on the roof of the coal seam is drawn by interpolation with a thickness contour line spacing of 1 to 10 m. The contour line with the smallest value in the contour map of the soil layer thickness of the coal seam roof is identified as the long axis of the potential soil layer missing area.

4. The method for investigating and treating localized water-permeable skylights in the coal seam roof as described in claim 1, characterized in that, Step 6: During the directional drilling process of the main directional borehole based on the design, the advance of each directional drilling step is 1m.

5. The method for investigating and treating localized water-permeable skylights in the coal seam roof as described in claim 4, characterized in that, Step 6 includes the following sub-steps: Step 61: Perform one directional drilling advance along the designed ground directional drilling main hole and perform one rock retrieval cut to determine whether the ground directional drilling main hole has been formed; If it has already formed, stop drilling; If it does not form, proceed to step 62; Step 62: Determine the source type of the rock fragments retrieved this time; If the rock fragments retrieved this time are from loose rock strata, then proceed to step 63; If the rock fragments retrieved this time are from soil layers, then proceed to step 64; Step 63: Pause directional drilling, design a vertical coring borehole at the corresponding ground location, and perform vertical drilling to obtain a core to the bedrock layer; determine whether there is a soil layer based on the coring results; If there is a soil layer, proceed to step 65; If there is no soil layer, the ground position corresponding to the position when directional drilling was paused will be taken as the upstream boundary of the soil layer missing area, and the process will return to step 61. Step 64: Stop drilling, designate the existing borehole as the main borehole for surface directional drilling, and take the ground position corresponding to the rock cut where the soil source was retrieved as the downstream boundary of the soil missing area. Step 65: After redesigning the near-horizontal section of the ground directional drilling main hole according to the thickness of the soil layer, return to step 61.

6. The method for investigating and treating localized water-permeable skylights in the coal seam roof as described in claim 5, characterized in that, In step 65, when redesigning the near-horizontal section of the ground directional drilling main hole, the near-horizontal section of the directional drilling is readjusted based on the soil layer thickness confirmed by the core sampling of the vertical borehole, with the middle position of the soil layer as the reference.

7. The method for investigating and treating localized water-permeable skylights in the coal seam roof as described in claim 6, characterized in that, In step 7, directional branch holes are designed and constructed sequentially from the center of the main directional drilling hole outwards with a hole spacing of 40-60m in the near-horizontal section, and drilling is carried out using the methods in steps 5 and 6. By sequentially connecting the starting points of the unretrieved soil layer and the starting points of the retrieved soil layer within the range of each directional branch hole, the enclosed area formed is the actual soil layer missing area.

8. The method for investigating and treating localized water-permeable skylights in the coal seam roof as described in claim 7, characterized in that, In step 8, if the rock cutting starting point is not found in a directional branch hole, during the continued directional drilling process, cement single-liquid grout or mixed grout is used to carry out segmented grouting at intervals of 20-50m until the grouting end standard is reached. After the previous grouting is completed, multiple grouting sections will continue to be carried out in 20-50m increments. Each grouting section will be completed after the grouting completion standard is met, and drilling and grouting will stop when the directional branch hole reaches the soil layer rock cut. By using the above method to traverse each directional branch hole, grouting modification is completed, thereby achieving the treatment of concentrated permeable skylights in the coal seam roof and the control of the source of roof water inflow.

9. The method for investigating and treating localized water-permeable skylights in the coal seam roof as described in claim 8, characterized in that, The mixing slurry in step 8 is either a cement-fly ash mixture or a cement-clay mixture. The water-to-solid ratio is 0.8-1.

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10. The method for investigating and treating localized water-permeable skylights in the coal seam roof as described in claim 9, characterized in that, The grouting completion standard in step 8 is: after reaching the maximum grouting pressure standard, reduce the pump flow rate to 60L / min and maintain it for 30min; The maximum grouting pressure P is determined using the following formula: P = (1.5 - 2) * H / 100 Where H represents the burial depth of the grouting section, in meters.

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