Deep overburden strata separation grouting subsidence reduction method based on cluster directional drilling technology

Abstract

The application discloses a deep overburden off-bedding grouting subsidence reduction method based on cluster directional drilling technology, and the method comprises the following steps: S1, determining an overburden key layer; S2, selecting an off-bedding space above a water flowing fractured zone as a grouting target horizon; S3, selecting different drilling methods according to the number of layers of the fillable off-bedding, if the number of layers of the off-bedding is one layer, performing step S4, and if the number of layers of the off-bedding is multiple layers, performing step S5; S4, arranging a directional drilling field on the ground surface close to a working face stop mining line position, adopting a multi-branch directional drilling technology to construct a first grouting hole, and performing grouting on the first grouting hole; and S5, arranging a directional drilling field on the ground surface close to the working face stop mining line position, and adopting a large-inclination directional drilling technology to construct a second grouting hole. The deep overburden off-bedding grouting subsidence reduction method based on the cluster directional drilling technology has the advantages of simple steps, stability and reliability, low cost and the like.

Description

Technical Field

[0001] This invention relates to the field of coal mining under three layers of overburden, and is applicable to the field of grouting technology for reducing subsidence in overburden separation. Specifically, it relates to a deep grouting method for reducing subsidence in overburden separation based on cluster directional drilling technology. Background Technology

[0002] In coal mining with underburden, grouting technology is widely used to control surface deformation, ensuring the safety of surface structures while allowing for smooth mining of the underlying coal seam. In China, the common method for grouting to reduce settlement in underburden separation involves drilling vertical grouting boreholes before the coal face reaches the designed borehole position, installing retaining casing, selecting the grouting timing through water pressure tests, and initiating grouting only after determining the development of separation.

[0003] Among related technologies, the delamination grouting and settlement reduction technique has certain problems in its implementation. Due to the advanced nature of coal mining, grouting boreholes constructed ahead of schedule often experience bending, flattening, or even shearing of the borehole casing in the Quaternary loose strata before delamination occurs, rendering the borehole unusable and preventing normal grouting. Furthermore, on-site workers often cannot promptly detect damage to the underground borehole structure. If grouting is attempted on the damaged borehole at this point, it will not only fail to fill the delamination space but may also cause grout leakage to the surface. Even if technical means are used to identify the damage to the borehole structure, re-drilling the grouting borehole will miss the opportunity for delamination grouting. Summary of the Invention

[0004] This invention is based on the inventor's discoveries and understanding of the following facts and problems:

[0005] In related technologies, such as Figure 5 and Figure 6 As shown, the delamination grouting reduction technology involves drilling vertical grouting holes directly above the delamination space. Due to the impact of the mine face's advanced mining, accidents such as crushing and breakage of the grouting hole casing near the mining position occur, resulting in low grouting filling efficiency and frequent accidents. In addition, the number of vertical boreholes is large, and the total drilling depth is large, resulting in high cost of delamination reduction grouting and great difficulty in construction coordination.

[0006] The present invention aims to at least partially solve one of the technical problems in the related art.

[0007] Therefore, embodiments of the present invention propose a deep overburden separation grouting and settlement reduction method based on cluster directional drilling technology, which is simple in procedure, can avoid the grouting borehole casing being sheared in the upper Quaternary loose layer, and has high grouting efficiency.

[0008] The deep overburden separation grouting and subsidence reduction method based on cluster directional drilling technology according to an embodiment of the present invention includes: S1: determining the key overburden layer based on mining geological data and exploration results;

[0009] S2: Based on the grouting process and the height of the water-conducting fracture zone, select the delamination space above the water-conducting fracture zone as the target grouting layer; S3: Select different drilling methods according to the number of layers that can be filled. If the number of delamination layers is one, proceed to step S4; if the number of delamination layers is multiple, proceed to step S5; S4: Layout a directional drilling site on the ground near the stop line of the working face, construct the first grouting hole using multi-branch directional drilling technology, and grout the first grouting hole. The grouting hole comprises a first well section, a second well section, and a third branch well section connected in sequence. The first well section of the first grouting hole is formed on one side close to the stop line, extending downwards from the wellhead into the stable bedrock. The second well section of the first grouting hole is located within the stable bedrock and extends towards the working face cut direction. The lower end of the first well section of the first grouting hole communicates with the second well section. The third branch well section of the first grouting hole includes multiple branch wells, which extend along the... The multiple branch holes are spaced apart along the mining direction, and one end of each branch hole is connected to the second section of the first grouting hole. The other end of each branch hole is located within the separation space. S5: A directional drilling site is set up on the surface near the stop-mining line of the working face. A second grouting hole is constructed using steep-angle directional drilling technology, and grouting is performed on the second grouting hole. The second grouting hole includes a first section and a second section connected in sequence. The first section of the second grouting hole extends downwards from the wellhead into the stable bedrock and is formed on one side near the stop-mining line. The second section of the second grouting hole is located within the separation space and includes multiple ascending sections and multiple descending sections. The ascending sections and descending sections are alternately arranged along the mining direction and are connected in a corresponding manner. The ascending sections extend from bottom to top and are inclined away from the direction of the first section of the second grouting hole. The descending sections extend from top to bottom and are inclined away from the direction of the first section of the second grouting hole.

[0010] This invention proposes a deep overburden separation grouting method for reducing settlement based on cluster directional drilling technology. The method includes steps S1, S2, S3, S4, and S5. Directional grouting boreholes are drilled ahead of the working face mining position, and grouting operations are carried out at opportune times. This avoids the impact range of the mining ahead of schedule and prevents the casing of the grouting borehole from being sheared off in the upper Quaternary loose layer, thereby improving the efficiency of drilling and grouting.

[0011] In some embodiments, before the first grouting hole is constructed in the early stage of working face mining, the distance of advance mining influence is measured to ensure that the first well section of the directional drilling first grouting hole is still not affected by advance mining in the final grouting stage, or before the second grouting hole is constructed in the early stage of working face mining, the distance of advance mining influence is measured to ensure that the first well section of the second grouting hole is still not affected by advance mining in the final grouting stage.

[0012] In some embodiments, there are multiple first grouting holes, which are spaced apart along the width direction of the longwall face. In a projection plane orthogonal to the width direction of the longwall face, the three-branch holes of the first grouting holes are alternately arranged with the three-branch holes of their adjacent first grouting holes along the longwall direction.

[0013] In some embodiments, the three-branched hole of the first grouting hole extends from top to bottom and is inclined toward the center of the delamination space.

[0014] In some embodiments, the target point spacing between the three-branch holes of two adjacent first grouting holes is 100m-200m.

[0015] In some embodiments, the plurality of branch holes along the mining direction respectively include branch hole A, branch hole C and branch hole E. Branch hole A is located on one side of an open section away from the first grouting hole. In step S3, the plurality of branch holes are formed using a back-drilling process. First, branch hole A is drilled and grouted. After the separation grouting of branch hole A is completed, branch hole A is swept open and sealed with cement grout. After branch hole A is sealed for 48-72 hours, branch hole C is drilled and grouted. After the separation grouting of branch hole C is completed, branch hole C is swept open and sealed with cement grout. After branch hole C is sealed for 48-72 hours, branch hole E is drilled and grouted.

[0016] In some embodiments, the second grouting hole is a long-distance, large-angle directional borehole, and there are multiple second grouting holes, which are spaced apart along the width direction of the mining face.

[0017] In some embodiments, the two ends of the rising section are connected to two adjacent descending sections, the upper end of the rising section forms a valley peak with one of the two adjacent descending sections, and the lower end of the rising section forms a valley bottom with one of the two adjacent descending sections. When viewed along the width direction of the mining face, the valley peak of the second grouting hole and the valley bottom of its adjacent second grouting hole are spaced apart and opposite to each other in the vertical direction.

[0018] In some embodiments, after the second grouting hole is drilled, as the mining face advances, the overburden separation layer gradually extends forward along the strike, and the second grouting hole is grouted in sections along the mining direction.

[0019] In some embodiments, the peak of the second grouting hole is formed at the top of the delamination space, and the bottom of the second grouting hole is formed at the bottom of the delamination space. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the grouting borehole in step S4 of the deep overburden separation grouting and subsidence reduction method based on cluster directional drilling technology in an embodiment of the present invention.

[0021] Figure 2 yes Figure 1 A top view diagram.

[0022] Figure 3 This is a schematic diagram of the grouting borehole in step S5 of the deep overburden separation grouting and settlement reduction method based on cluster directional drilling technology according to an embodiment of the present invention.

[0023] Figure 4 yes Figure 3 A top view diagram.

[0024] Figure 5 This is a schematic diagram of the grouting borehole for the overburden filling delamination grouting and settlement reduction process in related technologies.

[0025] Figure 6 yes Figure 5 A top view diagram.

[0026] Reference numerals: First grouting hole 1; First opening section of the first grouting hole 11; Second opening section of the first grouting hole 12; Third branch hole of the first grouting hole 13;

[0027] Second grouting hole 2; First opening section 21 of the second grouting hole; Second opening section 22 of the second grouting hole; Ascending section 221; Descending section 222; Valley peak 23; Valley bottom 24. Detailed Implementation

[0028] 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.

[0029] The following describes a deep overburden separation grouting method for reducing subsidence based on cluster directional drilling technology according to an embodiment of the present invention, with reference to the accompanying drawings.

[0030] like Figure 1-2As shown, the deep overburden delamination grouting and settlement reduction method based on cluster directional drilling technology according to an embodiment of the present invention includes steps S1, S2, S3, S4 and S5.

[0031] S1: Based on mining geological data and exploration results, determine the key overburden strata. Specifically, conduct exploration boreholes above the longwall face to ascertain the engineering geological conditions and the lithology of the overburden strata on the working face, and determine the height of the water-conducting fracture zone and the location of the key strata.

[0032] S2: Based on the grouting process and the height of the water-conducting fracture zone, a certain distance above the water-conducting fracture zone is selected as the target grouting layer. Specifically, the location of the delamination development is predicted, and a safe grouting distance is reserved before selecting the target grouting layer.

[0033] S3: Select different drilling methods based on the number of layers that can be filled. If there is only one layer of delamination, proceed to step S4; if there are multiple layers of delamination, proceed to step S5. Specifically, select different drilling and grouting methods based on the number of identified delamination layers. For example, when only one layer of grouting target layer is identified, use step S4 to drill and grout the single-layer delamination; when multiple layers of grouting target layer exist, use step S5 to drill and grout the multiple-layer delamination.

[0034] S4: A directional drilling site is set up on the ground near the stop line of the working face. The first grouting hole 1 is constructed using multi-branch directional drilling technology, and grouting is performed on the first grouting hole 1. The first grouting hole 1 includes a first well section 11, a second well section 12, and a third branch hole 13 connected in sequence. The first well section 11 of the first grouting hole is formed on the side near the stop line. The first well section 11 of the first grouting hole extends downward from the wellhead into the stable bedrock. The second well section 12 of the first grouting hole is located in the stable bedrock and extends towards the working face cut. The lower end of the first well section 11 of the first grouting hole is connected to the second well section 12 of the first grouting hole. The third branch hole 13 of the first grouting hole includes multiple branch holes. The multiple branch holes are spaced apart towards the working face cut, and one end of each of the multiple branch holes is connected to the second well section 12 of the first grouting hole. The other end of the multiple branch holes is located in the separation space.

[0035] Specifically, such as Figure 1-2As shown, a vertical shaft section is constructed downwards from the surface above the working face's extraction location. The first section 11 of the first grouting hole extends vertically downwards, with its inlet on the ground. The outlet of the first section 11 is located near stable bedrock and connects to the inlet of the second section 12 of the first grouting hole. The second section 12 is located within a critical stratum and extends horizontally in a generally left-right direction. The third branch hole 13 of the first grouting hole includes multiple branch holes, which are spaced apart in a left-right direction and generally extend vertically. Extending outwards, the upper end of the branch hole connects to the second section 12 of the first grouting hole, and the lower end of the branch hole extends into the separation space. Thus, coal-based solid waste slurry is injected into the separation space through the first section 11 of the first grouting hole, the second section 12 of the first grouting hole, and the third branch hole 13 of the first grouting hole to reinforce and fill the separation space. In addition, the first section 11 is formed on the side close to the stop line, which can effectively avoid the influence of the coal mining advance on the borehole casing, prevent the borehole casing from bending in the Quaternary loose layer, or even cause accidents such as flattening or shearing, and ensure the grouting effect of the first grouting hole 1.

[0036] S5: A directional drilling site is set up on the ground near the stop line of the working face. The second grouting hole 2 is constructed using steep angle directional drilling technology, and grouting is performed on the second grouting hole 2. The second grouting hole 2 includes a first well section 21 and a second well section 22 connected in sequence. The first well section 21 of the second grouting hole extends downward from the wellhead into the stable bedrock and is formed on the side near the stop line. The second well section 22 of the second grouting hole is located in multiple separation spaces and includes multiple rising sections 221 and multiple descending sections 222. The multiple rising sections 221 and multiple descending sections 222 are alternately arranged facing the cutting direction of the working face and are connected one-to-one. The rising sections 221 extend from bottom to top and are inclined away from the direction of the first well section 21 of the second grouting hole. The descending sections 222 extend from top to bottom and are inclined away from the direction of the first well section 22 of the second grouting hole.

[0037] Specifically, such as Figure 3-4As shown, drilling begins downwards on the surface ahead of the working face's extraction position. The first section 21 of the second grouting hole extends vertically downwards, with its inlet located on the ground surface. The outlet of this section is located near the separation space and connects to the inlet of the second section 22. The second section 22 comprises multiple ascending sections 221 and multiple descending sections 222, alternating sequentially in a left-right direction. The ascending sections 221 extend from bottom to top and slope to the right, while the descending sections 222 extend from bottom to top and slope to the right. Extending downwards and tilting to the left, each ascending segment 221 can have a descending segment 222 on both its left and right sides. The lower left end of the ascending segment 221 connects to the lower right end of the descending segment 222 on its left, and the upper right end of the ascending segment 221 connects to the upper left end of the descending segment 222 on its right. This makes the second grouting hole's second opening segment 22 generally wavy from left to right within the delamination space. Coal-based solid waste slurry is injected into the delamination space through the second grouting hole 2. Multi-layer delamination grouting and filling are achieved with very few boreholes. Compared with conventional vertical drilling methods, this saves drilling footage, reduces engineering costs, and shortens the drilling cycle. In addition, the first opening segment 21 of the second grouting hole is formed on the side close to the stop line, which can effectively avoid the influence of the coal mining advance influence zone on the borehole casing and prevent the borehole casing from bending or even flattening or shearing in the Quaternary loose layer, thus ensuring the grouting effect of the second grouting hole 2.

[0038] This invention proposes a deep overburden delamination grouting and subsidence reduction method based on cluster directional drilling technology, comprising steps S1, S2, S3, S4, and S5. Due to the complexity and heterogeneity of coalfield geological conditions, the development location of overburden delamination space is not clearly defined. Directional drilling allows for precise control of the trajectory, and the borehole trajectory can be flexibly adjusted. The horizontal section strata, the directional section strata, and the directional angle of the first grouting hole 1 and the second grouting hole 2 can be dynamically adjusted according to the stratum conditions, mining method, and delamination development to accurately hit the delamination space and improve grouting efficiency. The first grouting hole 1 and the second grouting hole 2 are constructed primarily within thick, hard rock strata and ahead of the coal face. At this time, the key strata have not yet fractured, resulting in high drilling efficiency and ease of drilling. This avoids damage to the borehole structure caused by advance mining, significantly improving grouting and filling efficiency.

[0039] In some embodiments, there are multiple first grouting holes 1, and the multiple first grouting holes 1 are located along the width direction of the mining face (e.g., ...). Figure 2 The spacing is set in the front-to-back direction (as shown). Specifically, as... Figure 1-2As shown, the number of first grouting holes 1 can be set according to the width of the longwall face. For example, when the size of the separation space in the front-to-back direction is small, one first grouting hole 1 can be set, and the first grouting hole 1 is formed in the middle of the separation space. When the size of the separation space in the front-to-back direction is large, multiple first grouting holes 1 can be set. The multiple first grouting holes 1 are set at equal intervals along the width direction of the longwall face, so that the separation space can be reinforced by grouting through multiple first grouting holes 1.

[0040] In some embodiments, within a projection plane orthogonal to the width direction of the longwall face, the three-branched holes 13 of the first grouting hole 1 and their adjacent three-branched holes 13 of the first grouting hole 1 face towards the cutting direction of the working face (e.g., Figure 2 The left and right directions are alternately set as shown. This allows for more uniform grouting of the delamination space, effectively improving the grouting filling rate and ensuring the grouting effect.

[0041] Since the delamination space is similar to a concave lens, meaning the cavity volume in the middle of the delamination space is larger than the cavity volume at the edge, the three-branched holes 13 of the first grouting hole 1 extend from top to bottom and are inclined towards the middle of the delamination space. This allows the coal-based solid waste slurry to be injected into the middle of the delamination space, making it more conducive to filling the delamination space fully and ensuring the grouting effect.

[0042] In some embodiments, the target point spacing between two adjacent three-branch holes 13 is 100m-200m. Specifically, the spacing between two adjacent three-branch holes 13 in the left-right direction can be any one of 100m, 120m, 140m, 160m, 180m, or 200m. When the spacing is less than 100m, the spacing between two adjacent three-branch holes 13 is too small, resulting in a large number of three-branch holes 13, which increases the drilling and grouting costs of the first grouting hole 1. When the spacing is greater than 200m, the spacing between two adjacent three-branch holes 13 is too large, resulting in poor grouting filling effect. Therefore, a spacing of 100m-200m ensures both the construction cost of the first grouting hole 1 and the grouting filling effect.

[0043] In some embodiments, the multiple branch holes facing the working face cutting direction respectively include branch hole A, branch hole C, and branch hole E. Branch hole A is located on one side of an opening section 11 away from the first grouting hole. In step S3, the multiple branch holes are formed using a retractable drilling process. First, branch hole A is drilled and grouted. After the separation grouting of branch hole A is completed, branch hole A is swept open and sealed with cement grout. After branch hole A is sealed for 48-72 hours, branch hole C is drilled and grouted. After the separation grouting of branch hole C is completed, branch hole C is swept open and sealed with cement grout. After branch hole C is sealed for 48-72 hours, branch hole E is drilled and grouted. Specifically, as shown... Figure 1-2 As shown, after the vertical section 11 of the first grouting hole 1 is drilled, the second section 12 of the first grouting hole 1 is drilled, and a large-angle directional drilling is implemented to change the borehole trajectory to near horizontal. For ease of description, the multiple branch holes are referred to as branch hole A, branch hole C, and branch hole E from right to left. First, branch hole A is drilled and grouted. After the grouting of the delamination where branch hole A is located is completed, the borehole is cleaned again after filling. After the borehole is cleaned, cement slurry is injected to seal the hole. After branch hole A is sealed for 48-72 hours, branch hole C is drilled and grouted. After the grouting of the delamination where branch hole C is located is completed, the borehole is cleaned again after filling. After the borehole is cleaned, cement slurry is injected to seal the hole. After branch hole C is sealed for 48-72 hours, branch hole E is drilled and grouted.

[0044] In some embodiments, there are multiple second grouting holes 2, and the multiple second grouting holes 2 are spaced apart along the width direction of the mining face. Specifically, as shown in... Figure 3-4 As shown, the number of second grouting holes 2 can be set according to the width of the longwall face. For example, when the separation space is along the dip direction or along the width direction (such as...), the number of second grouting holes 2 can be set according to the width of the longwall face. Figure 4 When the size of the delamination space (in the front-back direction) is small, one second grouting hole 2 can be set, and the second grouting hole 2 is formed in the middle of the delamination space. When the size of the delamination space in the dip direction or in the width direction is large, multiple second grouting holes 2 can be set. The multiple second grouting holes 2 are set at equal intervals in the dip direction or in the width direction, so that the delamination space can be filled by grouting through multiple second grouting holes 2.

[0045] In some embodiments, the two ends of the rising section 221 are connected to two adjacent descending sections 222. The upper end of the rising section 221 forms a valley peak 23 with one of the two adjacent descending sections 222, and the lower end of the rising section 221 forms a valley bottom 24 with one of the two adjacent descending sections 222. (See along the width direction of the longwall face, e.g.) Figure 3-4 As shown in the front-to-back view), the valley peak 23 of the second grouting hole 2 and the valley bottom 24 of the adjacent second grouting hole 2 are along the height direction of the working face (e.g., Figure 3 The vertical (as shown) spacing is relatively set. Specifically, as... Figure 3 As shown, the second well section 22 of the second grouting hole has a valley peak 23 and a valley bottom 24. The upper right end of the rising section 221 and the upper left end of the descending section 222 on its right side form a valley peak 23, and the lower left end of the rising section 221 and the lower right end of the descending section 222 on its left side form a valley bottom 24. The valley peak 23 and the valley bottom 24 are alternately arranged in the left and right directions. The valley peak 23 of the second grouting hole 2 and the valley bottom 24 of the adjacent second grouting hole 2 are arranged at intervals relative to each other in the working face direction, thereby effectively improving the filling rate and fully ensuring the filling effect of the grouting area.

[0046] In some embodiments, in step S5, after the second grouting hole 2 is drilled, as the mining face advances, the overlying strata gradually extend forward along the strike, and segmented grouting is performed on the second grouting hole 2 towards the cutting direction of the working face. Specifically, as... Figure 3-4 As shown, the second grouting hole 2, in its second well section 22, can be divided into multiple sub-segments from right to left. The second grouting hole 2 differs from the first grouting hole 1, which is formed and grouted in segments. The second grouting hole 2, however, is formed in one go and grouted continuously. Furthermore, the sub-segments gradually expand backward as the mining face advances. Therefore, based on the advancement of the mining face, multiple sub-segments can be reinforced by segmented grouting from right to left (spatially, grouting is segmented along the borehole from right to left; temporally, grouting is continuous), ensuring the grouting effect.

[0047] In some embodiments, the valley peak 23 of the second grouting hole 2 is formed at the top of the delamination space, and the valley bottom 24 of the second grouting hole 2 is formed at the bottom of the delamination space. Specifically, as shown in... Figure 3 As shown, peak 23 is located at the upper boundary of the top layer delamination space, and valley bottom 24 is located at the lower boundary of the bottom layer delamination space. This allows the second section of the second grouting hole to be filled with multiple delamination spaces, achieving multi-layer delamination grouting and filling.

[0048] It is worth noting that the first grouting hole 1 and the second grouting hole 2 can be used alternately in the separation space according to the number of layers that can be grouted. For example, in the separation space, the first grouting hole 1 and the second grouting hole 2 can be arranged alternately in the left-right or front-back direction.

[0049] In some embodiments, before the construction of the first grouting hole 1 in the early stage of working face mining, the distance of the impact of advanced mining is measured to ensure that the first section 11 of the directional drilling first grouting hole is not affected by advanced mining in the final grouting stage. Alternatively, before the construction of the second grouting hole 2 in the early stage of working face mining, the distance of the impact of advanced mining is measured to ensure that the first section 21 of the second grouting hole is not affected by advanced mining in the final grouting stage. This effectively avoids the impact of the advanced mining influence zone on the borehole casing, preventing the borehole casing from bending in the Quaternary loose layer, or even from flattening or shearing accidents, thus ensuring the grouting effect of the first grouting hole 1 and the second grouting hole 2.

[0050] The following is based on the appendix Figure 1-4 As shown, this invention specifically illustrates a deep overburden separation grouting method for reducing settlement based on cluster directional drilling technology.

[0051] When there is only a single groutable space in the overlying strata of the longwall face, taking the first grouting hole 1 as an example.

[0052] Two multi-branch directional boreholes were drilled in parallel near the stop line of the longwall mining face. After the first vertical section was completed (the first section 11 was completed), the second directional drilling section was started (the second section 12 was drilled). The borehole trajectory was changed to near horizontal by implementing a large-angle directional drilling. The third horizontal section was started above the key layer corresponding to the grouting target layer (the third branch hole 13 was drilled). First, the main holes A and B were drilled, followed by the branch holes C and D. The branch holes E, G, F and H were drilled in sequence using a retreating process.

[0053] Construction sequence: Two directional boreholes are drilled simultaneously to drill the first grouting hole 1 at the same time. After grouting of a branch hole is completed, the borehole should be cleaned again after natural pressure relief at the borehole opening, and then cement grout should be injected to solidify the hole. After 48-72 hours, the first and second opening sections of the well are cleaned, and side-drilling operations begin to drill the next branch hole. After the branch hole is completed, grouting begins. The construction is carried out alternately in this manner.

[0054] When there are multiple groutable separation spaces within the overlying crevass bend, taking the second grouting hole 2 as an example, multi-layer separation grouting and filling is carried out.

[0055] Two directional boreholes are arranged near the stop line of the longwall face. In the multi-level grouting area, the borehole trajectory is “wave-shaped” along the direction of the working face. In other words, the trajectories of the two directional boreholes conform to the sine curve and the cosine curve, respectively.

[0056] Both directional boreholes are parallel to the working face, and the peaks 23 and valleys 24 of their trajectory curves correspond one-to-one. Peak 23 corresponds to the upper boundary of the grouting area, and valley 24 corresponds to the lower boundary of the grouting area, which can effectively improve the filling rate and fully guarantee the filling effect of the grouting area.

[0057] Construction sequence:

[0058] Directional boreholes A and B are drilled simultaneously ahead of the coal face using a one-time drilling technique. Drilling is conducted ahead of the working face where the rock strata are relatively intact, reducing the drilling difficulty. After drilling, once the abscission space is created, grouting is performed simultaneously on both boreholes to ensure that the abscission space between the upper and lower strata is filled at the same time. As the working face advances, the overlying strata abscission gradually extends forward along the strike, and the directional boreholes are then grouted in a retreating, segmented manner.

[0059] In summary, the deep overburden separation grouting and settlement reduction method based on cluster directional drilling technology in this invention has the following advantages:

[0060] 1. Reduce the number of boreholes, save land acquisition area, reduce the difficulty of local coordination, and make the borehole layout more flexible. It can avoid obstacles such as ground buildings and structures when laying boreholes, and the technology is more widely applicable.

[0061] 2. Solve the problem of vertical boreholes being damaged by advance mining; vertical boreholes are easily damaged in Quaternary loose strata due to advance mining. Directional boreholes offer greater flexibility in selecting the opening location, construction timing, and borehole trajectory, and can effectively avoid the areas affected by advance mining.

[0062] 3. I and II directional boreholes can be arranged in parallel or staggered. The branch holes A→G and B→H in step S4 are arranged in a staggered manner along the direction. The peaks 23 and valleys 24 of the two borehole trajectory curves in step S5 correspond to each other, which improves the grouting and filling efficiency, effectively reduces the number of branches and the drilling depth, and reduces the project cost.

[0063] 4. The three-stage directional drilling is carried out in thick and hard rock strata, and the drilling is carried out ahead of the working face. At this time, the key layer has not yet fractured, the rock mass is intact, the drilling efficiency is high, and the drilling is easy.

[0064] 5. As the working face is mined, the ground subsidence can easily form water accumulation areas. Vertical boreholes are located in the middle of the working face and are often submerged by water accumulation. However, the boreholes of this technology are located near the stop line of the working face and will not be submerged by surface water accumulation, making subsequent grouting construction more convenient.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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 method for reducing settlement by grouting deep overburden separation based on cluster directional drilling technology, characterized in that, include: S1: Based on mining geological data and exploration results, determine the key overburden strata; S2: Based on the grouting process and the height of the water-conducting fracture zone, select the delamination space above the water-conducting fracture zone as the grouting target layer; S3: Select different drilling methods according to the number of layers that can be filled, where the number of layers is multiple, and proceed to step S4; S4: A directional drilling site is set up on the surface near the stop-mining line of the working face. A second grouting hole is constructed using steep-angle directional drilling technology, and grouting is performed on the second grouting hole. The second grouting hole includes a first well section and a second well section connected in sequence. The first well section of the second grouting hole extends downward from the wellhead into the stable bedrock and is formed on the side near the stop-mining line. The second well section of the second grouting hole is located in the separation space and includes multiple ascending sections and multiple descending sections. The multiple ascending sections and multiple descending sections are alternately arranged along the mining direction and are connected in a corresponding manner. The ascending sections extend from bottom to top and are inclined away from the direction of the first well section of the second grouting hole. The descending sections extend from top to bottom and are inclined away from the direction of the first well section of the second grouting hole. In the early stage of working face mining, before the construction of the second grouting hole, the influence distance of advance mining is measured. The first well section of the second grouting hole is still not affected by advance mining in the final grouting stage. The second grouting hole is a long-distance, large-angle directional borehole, and there are multiple second grouting holes. The multiple second grouting holes are spaced apart along the width direction of the mining face. The two ends of the rising section are connected to two adjacent descending sections. The upper end of the rising section forms a valley peak with one of the two adjacent descending sections, and the lower end of the rising section forms a valley bottom with one of the two adjacent descending sections. When viewed along the width direction of the mining face, the valley peak of the second grouting hole and the valley bottom of its adjacent second grouting hole are spaced apart and opposite to each other in the vertical direction.

2. The deep overburden separation grouting and settlement reduction method based on cluster directional drilling technology according to claim 1, characterized in that, After the second grouting hole is drilled, as the mining face advances, the overlying strata gradually extend forward along the strike, and the second grouting hole is grouted in sections along the mining direction.

3. The deep overburden separation grouting and settlement reduction method based on cluster directional drilling technology according to claim 2, characterized in that, The peak of the second grouting hole is formed at the top of the delamination space, and the bottom of the second grouting hole is formed at the bottom of the delamination space.

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