Grouting method for water-resisting layer of coal seam floor based on kilometer directional drilling

Abstract

The invention discloses a coal seam floor water-resisting layer grouting method based on kilometer directional drilling, and belongs to the technical field of mine underground engineering water disaster prevention and control. A plurality of drill sites and a plurality of directional drill holes are arranged below the top surface of the Ordovician limestone system; the drill holes are arranged in a comb-shaped and branch-shaped combined mode, a plurality of drill holes drilled in each drill site form a comb-shaped structure, and two adjacent drill holes located in two drill sites close to the middle in a mining area roadway are connected with branch-shaped drill holes. The drill holes drilled in the drilling site in the working face gate road intersect with the drill holes drilled in the drilling site in the mining area roadway; a subsection descending type grouting method is adopted, an orifice grout stopping mode is adopted, and continuous grouting and intermittent grouting are combined; by means of the method, bottom plate water-bearing layer transformation and water-resisting layer grouting reinforcement are achieved, and the problem that a diffusion blind area exists in a rear section due to the conical diffusion form of long-distance grouting drill holes is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of water hazard prevention and control in underground projects such as mines, and specifically is a coal seam floor waterproof layer grouting method based on kilometer-long directional drilling. Background Art

[0002] As the depth of domestic coal mining continues to increase, the threat of high-pressure karst fissure water from the Ordovician system to the safe mining of the lower coal seams has increased. The high water pressure on the coal seam floor and the development of hidden water-conducting fault structures seriously threaten the safe production of mines. According to statistics, about 80% of floor water inrush accidents are related to faults, and the hidden faults of the floor have always been the main factor causing water inrush from the coal seam floor due to their hidden characteristics. Therefore, the implementation of water conservation mining measures such as in-situ protection is a necessary condition for ensuring the safe production of coal mines. The reconstruction technology of coal seam floor aquifer is the main technical means to solve the current water disaster problem. The shortcomings of existing technologies are: (1) the scope of floor grouting is limited, and the grouting process lacks a quantitative and accurate determination method; (2) the current grouting scheme mainly considers the reconstruction of the aquifer, and rarely considers grouting reinforcement of the floor aquifer, and combining the two to establish a more complete water-blocking system; (3) the drilling technology in the tunnel construction is in urgent need of optimization and upgrading with the innovation of drilling rig equipment, and a more reasonable drilling construction plan needs to be determined; (4) due to the "conical" diffusion shape of the slurry in long-distance grouting drilling, there will be a diffusion blind area in the rear section; (5) there is a grouting blind area vertically below the casing section and the deflection section of conventional long-distance drilling.

[0003] Since most of the coal seams mined in the mines are close to the roof of the Ordovician limestone, the thickness of the effective waterproof layer in the treatment area cannot meet the safety requirements due to the depth of the floor mining damage zone and the Ordovician limestone confined water lifting zone. The area required for a single treatment is often the entire mining area. Therefore, it is particularly important to invent and design a grouting process that can achieve large-area treatment of the coal seam floor at the current and future stages.

[0004] The existing patent CN113898411A discloses a technology for in-situ protection of high-pressure limestone water in the coal seam floor. The technical solution is as follows: (1) Determine the floor grouting target area, including vertical layer determination and horizontal target determination; (2) Multi-branch horizontal well grouting, including four steps: 1) determination, 2) selection, 3) drilling, and 4) injection; (3) In-situ water conservation effect evaluation, including floor rock grouting effect evaluation and water resource bearing capacity recovery evaluation. This technical system provides a complete set of in-situ protection technology solutions for high-pressure limestone water in the coal seam floor, which can make the determination of the floor grouting target area more accurate. While taking into account the modification of the aquifer and the repair of the aquiclude, it reduces the number of vertical well sections, improves drilling efficiency, and makes up for the lack of attention paid to the water resource protection effect in the in-situ water conservation effect evaluation. However, the grouting area of ​​this technology is limited, and it is impossible to achieve large-area (entire mining area) grouting reinforcement of the bottom plate waterproof layer and aquifer transformation; there are grouting blind areas vertically below the grouting drilling casing section and the deflection section, and appropriate refilling plans should be adopted.

[0005] Tong Dandan. Application of coal seam grouting reinforcement technology in floor fracture area[J]. Western Mining Engineering, 2023, 35(05):131-132+135; The technical scheme is disclosed: (1) The floor limestone aquifer is the main area for grouting reinforcement and transformation; (2) The boreholes should be arranged according to the slurry diffusion radius of no more than 30m, and the boreholes should be densely arranged in special areas such as fault fissure development areas and geophysical anomaly areas; (3) The boreholes are mainly arranged with oblique holes, and they should pass through the fissures as much as possible, and be drilled obliquely to the fault structure and fissure development direction; (4) The final hole position should be 45~50m into the Ordovician limestone; (5) The construction should maintain the characteristics of process safety, economical material selection, high efficiency and stability. Use high-pressure grouting to block the cracks in the floor water-proof rock layer, so that the slurry is dehydrated, consolidated or gelled in the gaps or channels originally occupied by water in the grouting target layer, and the original floor water-proof layer is combined to prevent water from entering the working face. This technology mainly performs grouting reinforcement on the crack area of ​​the bottom plate, which means that only the aquifer has been transformed, and grouting reinforcement of the bottom plate aquiclude has not been considered. The two should be combined to establish a more complete water-blocking system.

[0006] The existing patent CN102877884A discloses a mine common Ordovician limestone top transformation and construction method based on sub-meter directional drilling technology. The technical scheme is as follows: (1) Use a kilometer directional drilling rig to drill holes in the Ordovician limestone high-pressure aquifer, and use the holes to perform drilling and grouting transformation to transform the Ordovician limestone aquifer within a certain range into an impermeable layer; (2) The holes are arranged along the Ordovician limestone layer, and are nonlinear, that is, they are arranged along the layer nonlinearly; (3) The drilling construction sequence is from the outside to the inside of the transformation area, and after the drilling and grouting of each hole are completed, the next hole construction is started; (4) The overall arrangement of the holes adopts a two-sequence arrangement, and the subsequent supplementary holes are used as inspection holes and supplementary injection holes for the previous construction; (5) During the grouting process, forward grouting is adopted, that is, after water gushing occurs in the borehole, the drill is withdrawn to carry out grouting, and drilling continues after the grouting is completed. The disadvantages are: (1) the grouting method and grouting process parameters and procedures are not combined to form a systematic grouting process; (2) the problem of grouting blind spots below the deflection section is not considered; (3) the "conical" diffusion pattern of the grouting drilling slurry in long-distance grouting is not considered, which will lead to the existence of diffusion blind spots in the rear section.

[0007] The existing patent CN110566118A discloses a method for pre-grouting transformation of a combined directional hole in a deep-buried aquifer floor in a coal mine; the technical scheme is as follows: (1) constructing a combined directional hole in the floor, the combined directional hole in the floor comprising an inclined hole section that enters the aquifer from the aquiclude and a horizontal hole section that starts from the inclined hole section and extends inside the aquifer; (2) constructing a jet hole section extending through at least one aquifer on the side wall of the inclined hole section at a preset interval, the jet hole section not intersecting with the horizontal hole section in the aquifer and covering the blind area of ​​the horizontal hole section; (3) grouting the horizontal hole section and the jet hole section to transform the aquifer floor into an aquiclude floor. The disadvantages are: (1) the grouting method and grouting process parameters and procedures are not combined to form a systematic grouting process; (2) the "conical" diffusion pattern of the grouting drilling slurry in long-distance grouting is not considered, which will lead to the existence of a diffusion blind area in the rear section; (3) when the working surface is large, no reasonable drilling site layout and drilling distribution plan are proposed.

[0008] Existing patent CN108952776A: A method for transforming the double limestone of the top and bottom plates by equidistant horizontal directional drilling and grouting; Technical solution: (1) Select a suitable drilling site to drill holes and construct the vertical hole section, and use a non-magnetic drill collar to start the construction of the inclined section after the first-level casing, and then lower the second-level casing after entering the bedrock; (2) After drilling the inclined section, adjust the direction to construct the main hole of the bottom plate, and after entering the limestone at the bottom of the coal seam, construct forward along the middle of the limestone layer; (3) After the main hole of the bottom plate is constructed, the foundation of the main hole of the bottom plate is On the top, adjust the orientation of the appropriate position of the bedrock to construct the bottom plate branch hole, adopt the forward grouting method to inject single liquid cement slurry, and construct other bottom plate branch holes in a similar way to transform the limestone aquifer into an impermeable layer; (4) After the construction of the bottom plate main hole is completed, sweep out the inclined section of the secondary casing and adjust the orientation to construct the top plate main hole. After entering the top limestone of the coal seam, construct the top plate branch hole of the coal seam top limestone in a similar way, and inject loess cement slurry by forward high-pressure grouting technology to transform the top plate limestone into a weak aquifer. The disadvantages are (1) the grouting method and grouting process parameters and processes are not combined to form a systematic grouting process; (2) the problem of grouting blind area below the inclined section is not considered; (3) the "conical" diffusion form of the slurry in the long-distance grouting drilling is not considered, which will lead to the existence of diffusion blind area in the back section; (4) when the working face is large, no reasonable drilling site layout and drilling distribution plan are proposed.

[0009] Under normal circumstances, the danger of Ordovician limestone water inrush is relatively small. Under the influence of geological structure, it may enter the working face and cause impact. However, with the continuous increase in the depth of domestic coal mining, most mines mine coal seams close to the Ordovician limestone roof. Especially during the mining of the working face, due to the influence of the depth of the floor mining damage zone and the Ordovician limestone pressure water lifting zone, the thickness of the effective water-proof layer in the treatment area cannot meet the safety requirements, and the single treatment area is often manifested as the entire mining area. Summary of the invention

[0010] The present invention overcomes the shortcomings of the prior art and proposes a coal seam floor waterproof layer grouting method based on kilometer-long directional drilling; it can perform regional grouting transformation on karst aquifers within a certain range, increase the effective thickness of the floor waterproof layer, and realize water-saving mining in the mine. The technical solution of the present invention can mainly achieve the following purposes: (1) Realize the grouting transformation of the floor slab in a large area; (2) It not only realizes the transformation of the bottom plate aquifer but also realizes the grouting reinforcement of the aquiclude, and combines the two to establish a more complete water-blocking system; (3) Solve the problem of diffusion blind spots in the rear section caused by the "conical" diffusion shape of long-distance grouting drilling; (4) Solve the problem of grouting blind spots vertically below the casing section and the deflection section of long-distance grouting drilling; (5) Improve the grouting scheme and optimize the grouting process.

[0011] The present invention is achieved through the following technical solutions: A method for grouting a water-proof layer of a coal seam floor based on kilometer-long directional drilling, comprising the following steps: S1. Drilling arrangement: a plurality of drilling sites and a plurality of directional drilling holes are arranged below the top surface of the Ordovician limestone system; the plurality of drilling sites are arranged in sequence along the working face slot on one side, to the mining area roadway, and then to the working face slot on the other side, so that a part of the drilling sites are located in the working face slot, and the other part of the drilling sites are located in the mining area roadway; The plurality of directional boreholes are drilled into the mining area tunnel through a plurality of drilling sites; the boreholes are arranged in a combination of "comb-like" and "branch-like" manners, wherein the plurality of boreholes drilled by each drilling site form a comb-like structure, and two boreholes adjacent to each other in two drilling sites located in the mining area tunnel and close to the middle are connected with branch-like boreholes, and the branch-like boreholes on both sides are inclined toward the middle of the mining area tunnel; The boreholes drilled by the drilling site in the working face trench intersect with the boreholes drilled by the drilling site in the mining area tunnel; the length of all boreholes runs through the entire mining area floor; S2. Grouting construction: adopt the segmented downward grouting method, use the hole-stopping method, and combine continuous and intermittent grouting.

[0012] Furthermore, there is a grouting blind area between the adjacent drilling sites located in the working face drift and the drilling sites located in the mining area tunnel. In the later stage, grouting transformation is carried out by supplementary measures such as general drilling and drilling in the grouting blind area.

[0013] Furthermore, the thickness of the safe waterproof layer of the coal seam floor is: M 安 = P 煤 / T 临 Where: P 煤 The coal seam floor is subjected to the lime water pressure, MPa; T 临 is the water inrush coefficient, MPa / m; The calculation formula for the depth of the water-conducting damage zone caused by floor mining (multiple factors) is as follows: Where: H 煤 is the thickness of the coal seam, m; H 埋 is the depth of coal seam, m; is the formation dip, °; L is the inclined length of the working surface, m; f is the base plate solidity coefficient; The calculation formula for the thickness of the effective waterproof layer of the coal seam floor is: M - h 1+ h 注 = M 有效 > M 安 Where: M is the thickness of the impermeable layer from the coal seam floor to the top of the Ordovician ash, m; h 注 is the grouting thickness at the top of the Ordovician limestone system, m; Effective thickness of the waterproof layer of the coal seam floor after grouting transformation M 有效 Meet the thickness requirements of the safety waterproof layer.

[0014] Furthermore, the number of drilling site layouts and the density of drilling branching are adjusted according to the slurry diffusion radius; the slurry diffusion radius calculation formula is as follows: In the formula: R is the diffusion radius of the slurry, m; r1 is the radius of the grouting hole, m; η is the aquifer fracture rate, %; K is the aquifer permeability coefficient, m / d; C1 and C in C / C1 are the viscosities of the slurry and water respectively, cP; p is the grouting pressure, MPa; t is the slurry gel time, d.

[0015] Furthermore, the directional drilling is a single-row drilling, which consists of a casing hole section, a rotary drilling section, a directional inclination section and a directional inclination stabilization section; the directional drilling is a three-stage hole body structure, with two lower stages of casing, and the second-opening casing is lowered into a stable formation.

[0016] Furthermore, directional drilling adopts sequential construction, and subsequent drilling checks the previous holes, drilling on the one hand and grouting on the other; the latter holes check the former holes, and the grouting reinforcement of the former holes is verified through simple hydrological observations of the drilling holes.

[0017] Furthermore, the grouting pipeline is inspected and flushed before grouting, and a pressure test is carried out; before grouting each hole, the borehole water volume and water pressure are observed and the water is released, and then water is pressurized to clear the grouting pipeline and rock cracks in the hole; the water absorption rate of the unit receiving layer section is measured in order to adjust the grouting parameters, and the slurry type and its concentration are determined based on the results of the water pressure test; after the grouting pressure reaches the end standard, a water pressure test is carried out, and after reaching the double standards of the orifice pressure and grouting volume, it is maintained for 30~40 minutes to end the grouting of this section.

[0018] Furthermore, after each grouting, water must be pressed into the hole, and the amount of water pressed is twice the sum of the volume of the pipeline and the hole. After that, the valve must not be opened during the slurry gelling time.

[0019] Furthermore, the standard for the end of single-hole grouting is: 1) Total grouting pressure, determine the orifice pressure standard The total grouting pressure is composed of two parts: the deadweight pressure of the slurry column in the hole and the pressure generated by the grouting pump. The calculation formula is as follows: Where: P 0 is the total grouting pressure, MPa; P m is the orifice pressure, MPa; H It is the height from the well mouth to the 1 / 2 of the injection layer, m; r is the specific gravity of the slurry, g / cm 3 ; h It is the height of water column at 1 / 2 of the grouting section before grouting, m.

[0020] 2) Water absorption rate, calculation of grouting quantity standard Adjust the slurry concentration in time according to the water pressure test results. The water pressure test results are expressed as water absorption rate. q express: Where: q is the water absorption rate, L / min.mm; Q is the pressure flow rate, L / min; P is the total pressure acting in the test section, m; L is the length of the injection layer, m.

[0021] Furthermore, if it is found during the grouting process that the borehole is leaking grout, is blocked, or the amount of grouting in the borehole is significantly reduced, the hole must be re-swept or the inspection hole must be re-drilled for grouting. As long as the standard for the completion of full-hole grouting has not been reached, water must be pressed after each grouting. If water cannot be pressed in, the drill bit must be lowered to penetrate and sweep the hole to the bottom of the hole for the next grouting.

[0022] The beneficial effects of the present invention compared with the prior art are as follows: (1) Based on the kilometer-long directional drilling, large-scale grouting of the bottom plate waterproof layer and transformation of the aquifer can be achieved, which reduces the required drilling site development, effectively reduces the investment required for the initial hole drilling, and speeds up the grouting progress; (2) The grouting blind area control plan not only effectively solves the problem of grouting blind areas vertically below the drilling casing section and the deflection section, but also solves the problem of diffusion blind areas in the rear section caused by the "conical" diffusion shape of long-distance grouting drilling. The slurry diffusion range basically achieves full coverage of the coal seam bottom plate in the mining area, improving the overall grouting effect of the coal seam bottom plate; (3) The optimized grouting plan and grouting process system enhance the slurry diffusion effect and improve the grouting quality.

[0023] Through the coal seam floor waterproof layer grouting process and aquifer transformation technology, water-preserving mining of coal seams is achieved, which can guarantee the normal production and living needs of human society, the continuous normal operation of the mining face and the sustainable development of mines, and further improve the level of water-preserving mining technology in mines under complex and difficult geological conditions in my country. It can also achieve beneficial effects in safety and ecology, realize the ecological balance of mining areas and the benign and efficient circulation of ecosystems, play a leading and exemplary role in mines with similar conditions, and has broad prospects for promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the arrangement of the drilling site in the mining area tunnel in the embodiment; Figure 2 Schematic diagram of directional drilling of bottom plate grouting in an embodiment; Figure 3 A schematic diagram of a drilling structure in an embodiment; Figure 4 It is a flowchart of drilling construction in the embodiment; Figure 5 Schematic diagram of the principle of downhole directional drilling in the embodiment; Figure 6 for Figure 5 Side profile of downhole directional drilling at borehole A in the middle; Figure 7 It is a structural schematic diagram of the grouting hole orifice device in the embodiment; Figure 8 It is a schematic diagram of the downward staged grouting process of underground directional drilling in the embodiment. DETAILED DESCRIPTION

[0025] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention is further described in detail in conjunction with the embodiments and the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. The technical solutions of the present invention are described in detail below in conjunction with the embodiments and the accompanying drawings, but the scope of protection is not limited thereto.

[0026] See also Figures 1 to 8 ,This embodiment proposes a coal seam floor waterproof layer grouting method based on kilometer directional drilling; 1. Purpose: Taking into account the influence of the depth of the floor mining damage zone and the Ordovician ash lifting zone when mining the coal seam near the roof of the Ordovician ash system, the thickness of the effective aquifer in the floor of the coal seam to be treated cannot meet the safety requirements. In order to ensure the safe mining of the coal seam, it is necessary to grout the floor aquifer and transform the aquifer.

[0027] (1) Thickness of the safe waterproof layer of the coal seam floor: M安 = P 煤 / T 临 Where: P 煤 The coal seam floor is subjected to the lime water pressure, MPa; T 临 is the water inrush coefficient, MPa / m.

[0028] (2) The calculation formula for the depth of the water-conducting damage zone caused by floor mining (multiple factors) is as follows: Where: H 煤 is the thickness of the coal seam, m; H 埋 is the depth of coal seam, m; is the formation dip, °; L is the inclined length of the working surface, m; f is the base plate strength factor.

[0029] (3) The calculation formula for the thickness of the effective impermeable layer of the coal seam floor is: M - h 1+ h 注 = M 有效 > M 安 Where: M is the thickness of the impermeable layer from the coal seam floor to the top of the Ordovician ash, m; h 注 is the grouting thickness at the top of the Ordovician gray system, m.

[0030] In order to ensure the grouting effect and effectively block the channel of the lifting belt, it is designed to carry out regional grouting transformation of the karst aquifer in a certain range (calculated and determined according to specific geological conditions) at the top of the Ordovician limestone system to increase the effective thickness of the bottom plate aquifer. h 注 The calculation formula of the effective waterproof layer thickness of the coal seam floor is established. Then the effective thickness of the waterproof layer section of the coal seam floor after grouting transformation ( M 有效 ) can meet the thickness requirements of the safety waterproof layer.

[0031] 2. Technical solution Considering the current mining situation, strata and equipment capacity (mainly due to the large area of ​​the injection area), the design adopts underground directional holes to carry out grouting transformation on the top karst aquifer of the Ordovician system. The drilling holes are arranged in a combination of "comb-like" and "branch-like" ways. The 1#, 2#, 3#, 8# and 9# drilling sites are located in the working face drift, and the 4#, 5#, 6# and 7# drilling sites are arranged in the mining area tunnels. The construction sequence of the drilling sites is in the order of numbering (see Figure 1 ), to facilitate the next mining area to continue grouting construction and reduce the workload of moving the machine.

[0032] Several directional boreholes are drilled into the mining area tunnels through the 1#~9# drilling sites; the boreholes are arranged in a combination of "comb-like" and "branch-like" arrangements, where the multiple boreholes drilled in each drilling site form a comb-like structure. The two drilling sites located in the mining area tunnels and close to the middle, namely the 5# and 6# drilling sites, have two adjacent boreholes connected by branch-like boreholes (see Figure 1 The branch-shaped drill holes on both sides are inclined toward the middle of the mining area tunnel; The boreholes drilled by the drilling sites (1#, 2#, 3#, 8#, 9# drilling sites) in the working face drift intersect with the boreholes drilled by the drilling sites (4#, 5#, 6#, 7# drilling sites) in the mining area tunnels; the length of all boreholes runs through the entire mining area floor; Grouting blind area treatment plan: The boreholes in 4#, 5#, 6#, and 7# drilling sites are generally arranged in parallel with the mining area tunnel direction, mainly for the treatment of grouting blind areas formed by the casing section and beveling section of 1#, 2#, 3#, 8#, and 9# drilling sites (see Figure 5 and Figure 6 ); In addition, it can also solve the problem of diffusion blind area in the rear section caused by the "conical" diffusion shape of long-distance grouting drilling. The specific arrangement of drilling site and drilling hole can be seen in Figure 1 Since the area near the 3# and 4# drilling sites is mainly the intersection of the casing section and the deflection section, there is a certain grouting blind area below it, which can be transformed by grouting through the supplementary measures of general drilling and drilling.

[0033] The following directional drilling design and grouting engineering design are explained by taking the 5# drilling site as an example. The drilling design schemes of other drilling sites are the same and can be adjusted appropriately according to the specific geological conditions. The drilling rig adopts the ZYL-17000D crawler-type full hydraulic directional drilling rig.

[0034] 2.1 Directional drilling design (1) Drilling arrangement Directional drilling is designed as a single row of holes, and the target stratum is 15 to 20 meters below the top of the Ordovician System ( Figure 2 H in the figure is a specific value for ease of explanation), and the length of the borehole runs through the entire floor of the mining area.

[0035] (2) Drilling hole structure design When the drilling site layout and the borehole branch design are determined, the reasonable grouting hole radius range (i.e., the third-level hole body) can be inferred from the branch hole spacing (or slurry diffusion radius) and formula (4), and then the second-level slurry diffusion radius calculation formula and the first-level hole body size can be designed according to the actual geological conditions and grouting requirements. The hole body size can also be determined first based on actual engineering experience, but the number of drilling site layouts and the density of borehole branches need to be further adjusted according to the slurry diffusion radius.

[0036] The bottom plate grouting directional drilling consists of a casing hole section, a rotary drilling section, a directional deflection section and a directional deflection stabilization section (see Figure 2 The borehole is designed as a three-stage borehole structure, with two-stage casings, and the second-stage casing is lowered into the stable stratum. The specific lowering depth can be adjusted according to construction needs. The diagram is tentatively set at 60m, the final borehole diameter is Φ120mm, and the borehole structure is shown in Figure 3 and Table 1, the drilling construction process is shown in Figure 4 .

[0037] (3) Drilling construction sequence Directional drilling in the well adopts sequential construction. Subsequent drilling tests the previous holes. On the one hand, drilling is done, and on the other hand, grouting is done. The latter hole tests the former hole. The grouting reinforcement of the former hole is verified through simple hydrological observation of the borehole. Taking the 5# borehole as an example, the construction sequence is 5-1-2#→5-2-2#→5-1-1#→5-2-3#→5-2-1#→5-2-4# (see Figure 1 ). See the schematic diagram of the directional drilling principle of No. 5 borehole. Figure 5 and Figure 6 .

[0038] 2.2 Grouting process design (1) Grouting method and grouting section division A ground mixed grouting station is built in the wind shaft area. The grouting method is the segmented downward grouting method, which adopts the hole stop method and combines continuous and intermittent grouting. The bottom plate grouting is carried out every 150m of drilling construction. If the water inflow during the drilling process is greater than 50m 3 / h, the drilling can be stopped at any time and the drilling grouting can be started. If the drilling is unable to proceed due to large cavities or dissolution gaps during the construction process, the grouting section can be adjusted according to the actual situation.

[0039] (2) Branch hole spacing The spacing between branch holes is determined based on the slurry diffusion radius and grouting experience. The slurry diffusion radius calculation formula is as follows: In the formula: R is the diffusion radius of the slurry, m; r1 is the radius of the grouting hole, m; η is the aquifer fracture rate, %; K is the aquifer permeability coefficient, m / d; C1 and C in C / C1 are the viscosities of the slurry and water respectively, cP; p is the grouting pressure, MPa; t is the slurry gel time, d.

[0040] In the water-rich section, the trajectory is appropriately adjusted to reduce the hole spacing, and short branches can be constructed when necessary to ensure the grouting effect. The 5# drilling site is equipped with 2 directional main holes and 4 branch holes.

[0041] (3) Grouting hole orifice device The grouting orifice needs to be equipped with a pressure gauge and corresponding valves to monitor the grouting pressure in real time and facilitate the adjustment of grouting parameters. Figure 7 .

[0042] (4) Single hole grouting completion criteria 1) Total grouting pressure (determine the orifice pressure standard) The total grouting pressure is composed of the deadweight pressure of the grout column in the hole and the pressure generated by the grouting pump. It is generally twice the hydrostatic pressure. The grouting pressure can be adjusted according to the site conditions during construction. The calculation formula is as follows: Where: P 0 is the total grouting pressure, MPa; P m is the orifice pressure, MPa; H It is the height from the well mouth to the 1 / 2 of the injection layer, m; r is the specific gravity of the slurry, g / cm 3 ; h It is the height of water column at 1 / 2 of the grouting section before grouting, m.

[0043] 2) Water absorption rate (standard for calculating grouting volume) The slurry concentration can be adjusted in time according to the water pressure test results. The water pressure test results are expressed as water absorption rate. q express: Where: q is the water absorption rate, L / min.mm; Q is the pressure flow rate, L / min; P is the total pressure acting in the test section, m; L is the length of the injection layer, m.

[0044] (5) Grouting construction 1) Before grouting, the grouting pipeline should be inspected and flushed, and a pressure test should be carried out. The test pressure should not be less than 8MPa (based on the grouting pressure at the orifice). P mDetermine, take 1.5 times of the theoretical calculated value), the duration shall not be less than 20 minutes; 2) Before grouting each hole, the water volume and water pressure in the borehole must be observed and the water must be drained for at least 10 minutes, until there is no rock powder in the hole and the water becomes clear. After that, water pressure is applied to dredge the grouting pipeline and the rock cracks in the hole, and the water absorption rate of the unit receiving layer is measured to adjust the grouting parameters. According to the results of the water pressure test, the type of slurry and its concentration are determined. The amount of water pressed into the hole should be no less than 2 times the total volume of the pipeline, and grouting can be started after there is no abnormal change; 3) Downhole hole grouting pressure P m When the pressure reaches 7MPa (determined on the basis of being greater than the theoretical calculation result combined with the total grouting pressure and the actual grouting conditions during construction), the grouting hole section is considered to have reached the pressure end standard; 4) After the grouting pressure reaches the end standard, a water pressure test is carried out to measure the unit water absorption rate. q When it is less than 0.005L / min.mm (equivalent to the water permeability of the solid rock layer of the bottom plate, which is sandstone in this case), the section can be considered to have reached the grouting end standard. According to the unit water absorption rate and the borehole length, the grouting end standard can be obtained by reverse calculation. After reaching the double standards of orifice pressure and grouting volume, maintain for 30 minutes and end the grouting of this section; 5) After each grouting, water must be pressed into the hole. The amount of water pressed should be twice the sum of the volume of the pipeline and the hole. The valve must not be opened within the next 8 hours (determined by the gelling time of the slurry, here it is cement slurry).

[0045] The process of downhole directional drilling and segmented grouting is shown in Figure 8 .

[0046] (6) Evaluation of grouting effect After the grouting is finished and the setting time is reached, the hole is swept. After the hole is swept, a water pressure test is carried out. The pressure reaches the final grouting pressure within 30 minutes. The unit water absorption rate q When it is less than 0.005L / min.mm, the section can be considered to have reached the grouting end standard.

[0047] (7) Notes If during the grouting process, it is found that the borehole is leaking grout, is blocked, or the amount of grouting in the borehole is significantly reduced, the hole must be re-swept or the inspection hole must be re-drilled for grouting. As long as the standard for the completion of full-hole grouting has not been reached, water must be pressed after each grouting. If water cannot be pressed in, the drill bit must be lowered to penetrate and sweep the hole to the bottom of the hole for the next grouting.

[0048] The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be determined that the specific embodiments of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the present invention, which should be regarded as belonging to the present invention and the scope of patent protection determined by the submitted claims.

Claims

1. A method for grouting a waterproof layer of a coal seam floor based on kilometer-long directional drilling, characterized in that: The following steps are involved: S1. Drilling arrangement: a plurality of drilling sites and a plurality of directional drilling holes are arranged below the top surface of the Ordovician limestone system; the plurality of drilling sites are arranged in sequence along the working face slot on one side, to the mining area roadway, and then to the working face slot on the other side, so that a part of the drilling sites are located in the working face slot, and the other part of the drilling sites are located in the mining area roadway; The plurality of directional boreholes are drilled into the mining area tunnel through a plurality of drilling sites; the boreholes are arranged in a combination of "comb-like" and "branch-like" manners, wherein the plurality of boreholes drilled by each drilling site form a comb-like structure, and two boreholes adjacent to each other in two drilling sites located in the mining area tunnel and close to the middle are connected with branch-like boreholes, and the branch-like boreholes on both sides are inclined toward the middle of the mining area tunnel; The boreholes drilled by the drilling site in the working face trench intersect with the boreholes drilled by the drilling site in the mining area tunnel; the length of all boreholes runs through the entire mining area floor; S2. Grouting construction: adopt the segmented downward grouting method, use the hole-stopping method, and combine continuous and intermittent grouting.

2. The method for grouting a waterproof layer of a coal seam floor based on kilometer-long directional drilling according to claim 1 is characterized in that: There is a grouting blind area between the adjacent drilling sites in the working face drift and the drilling sites in the mining area tunnel. In the later stage, grouting transformation is carried out by supplementary measures such as general drilling and drilling in the grouting blind area.

3. The method for grouting a waterproof layer of a coal seam floor based on kilometer-long directional drilling according to claim 1 is characterized in that: Thickness of safe waterproof layer of coal seam floor: M 安 = P 煤 / T 临 Where: P 煤 The coal seam floor is subjected to the lime water pressure, MPa; T 临 is the water inrush coefficient, MPa / m; The calculation formula for the depth of the water-conducting damage zone caused by bottom mining is as follows: Where: H 煤 is the thickness of the coal seam, m; H 埋 is the depth of coal seam, m; is the formation dip, °; L is the inclined length of the working surface, m; f is the base plate solidity coefficient; The calculation formula for the thickness of the effective waterproof layer of the coal seam floor is: M - h 1+ h 注 = M 有效 ＞ M 安 Where: M is the thickness of the impermeable layer from the coal seam floor to the top of the Ordovician ash, m; h 注 is the grouting thickness at the top of the Ordovician limestone system, m; Effective thickness of the waterproof layer of the coal seam floor after grouting transformation M 有效 Meet the thickness requirements of the safety waterproof layer.

4. The method for grouting a water-proof layer of a coal seam floor based on kilometer-long directional drilling according to claim 1 is characterized in that: The number of drilling site layouts and the density of drilling branches are adjusted according to the slurry diffusion radius; the slurry diffusion radius calculation formula is as follows: In the formula: R is the diffusion radius of the slurry, m; r1 is the radius of the grouting hole, m; η is the aquifer fracture rate, %; K is the aquifer permeability coefficient, m / d; C1 and C in C / C1 are the viscosities of the slurry and water respectively, cP; p is the grouting pressure, MPa; t is the slurry gel time, d.

5. The method for grouting a waterproof layer of a coal seam floor based on kilometer-long directional drilling according to claim 1, characterized in that: The directional drilling is a single-row drilling, which consists of a casing hole section, a rotary drilling section, a directional deflection section and a directional deflection stabilization section; the directional drilling is a three-stage hole body structure, with two lower casings, and the second-opening casing is lowered into a stable formation.

6. The method for grouting a waterproof layer of a coal seam floor based on kilometer-long directional drilling according to claim 1, characterized in that: Directional drilling adopts sequential construction. Subsequent drilling tests the previous holes. On the one hand, drilling is carried out, and on the other hand, grouting is carried out. The latter hole tests the former hole. The grouting reinforcement of the former hole is verified through simple hydrological observation of the drilling.

7. The method for grouting a waterproof layer of a coal seam floor based on kilometer-long directional drilling according to claim 1, characterized in that: Before grouting, the grouting pipeline is inspected and flushed, and a pressure test is carried out. Before grouting each hole, the borehole water volume and water pressure are observed and the water is released, and then water is pressurized to clear the grouting pipeline and rock cracks in the hole. The water absorption rate of the unit receiving layer section is measured in order to adjust the grouting parameters, and the slurry type and its concentration are determined based on the results of the water pressure test. After the grouting pressure reaches the end standard, a water pressure test is carried out, and after reaching the double standards of the orifice pressure and grouting volume, it is maintained for 30 to 40 minutes to end the grouting of this section.

8. The method for grouting a waterproof layer of a coal seam floor based on kilometer-long directional drilling according to claim 7, characterized in that: After each grouting, water must be pressed into the hole. The amount of water pressed should be twice the sum of the volume of the pipeline and the hole. The valve must not be opened during the gelling time of the slurry.

9. The method for grouting a waterproof layer of a coal seam floor based on kilometer-long directional drilling according to claim 7, characterized in that: The standard for the end of single hole grouting is: 1) Total grouting pressure, determine the orifice pressure standard The total grouting pressure is composed of two parts: the deadweight pressure of the slurry column in the hole and the pressure generated by the grouting pump. The calculation formula is as follows: Where: P 0 is the total grouting pressure, MPa; P m is the orifice pressure, MPa; H It is the height from the well mouth to the 1 / 2 of the injection layer, m; r is the specific gravity of the slurry, g / cm 3 ; h is the height of the water column at 1 / 2 of the grouting section before grouting, m; 2) Water absorption rate, calculation of grouting quantity standard Adjust the slurry concentration in time according to the water pressure test results. The water pressure test results are expressed as water absorption rate. q express: Where: q is the water absorption rate, L / min.mm; Q is the pressure flow rate, L / min; P is the total pressure acting in the test section, m; L is the length of the injection layer, m.

10. The method for grouting a water-proof layer of a coal seam floor based on kilometer-long directional drilling according to claim 7, characterized in that: If during the grouting process, it is found that the borehole is leaking grout, is blocked, or the amount of grouting in the borehole is significantly reduced, the hole must be re-swept or the inspection hole must be re-drilled for grouting. As long as the standard for the completion of full-hole grouting has not been reached, water must be pressed after each grouting. If water cannot be pressed in, the drill bit must be lowered to penetrate and sweep the hole to the bottom of the hole for the next grouting.

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