A water disaster control method and construction method for coal seam mining in a water-rich graben structure

Abstract

The present invention discloses a water disaster control method and a construction method for coal seam mining in a water-rich graben structure, including: Step 1: Determine the type of water-rich graben according to the occurrence of the fault and the relative position relationship between the coal seam and the aquifer; Type I: Both sides of the coal seam are connected to the lateral aquifer; Type II: One side of the coal seam is connected to the lateral aquifer, and the other side is close to the lateral aquifer; Type III: Both sides of the coal seam are close to the lateral aquifer; Type IV: There is an aquifer in the coal seam floor and the thickness of the water-resisting layer is insufficient; Step 2: Determine the control range according to the type of water-rich graben; By grouting and transforming the lateral aquifer in the set range into a water-resisting layer, the transformed stratum is used as a water-resisting rock pillar. At the same time, the fault is grouted and transformed into a non-water-conducting fault. After the transformation, coal pillars are left according to the non-water-conducting fault, which greatly shortens the width of the coal pillars, enables the recovery of coal pillar resources, improves the utilization rate of coal resources, increases the economic benefits of the mine, and extends the mine life.

Description

Technical Field

[0001] The invention belongs to the technical field of prevention and control of water in coal mine floor, and relates to a water disaster control method and a construction method for coal seam mining in a water-rich graben structure. Background Art

[0002] A graben is a geological structure widely developed on the earth's crust, which is a trough-shaped fault block structure surrounded by high-angle faults on both sides and descending in the middle. In the North China type coal sedimentary basin, multiple limestone aquifers are developed in the coal seam floor. Especially, the Ordovician limestone aquifer as the basement has the characteristics of large thickness, high water pressure and strong water richness. Once the Ordovician limestone water bursts into the mine, it often causes serious and major water disaster accidents. In the graben structure formed by faults, the faults lift the Ordovician limestone aquifer in the hanging wall close to the coal seam or even connect with the coal seam. The Ordovician limestone aquifer fills water into the coal seam through fault water conduction or directly, seriously threatening the safe coal mining. At present, for coal seam mining in a graben structure with faults and aquifers on the side, the main water disaster prevention and control method is to leave water-resisting coal and rock pillars to prevent the aquifer water from bursting into the mine excavation space. The problems and disadvantages existing in this technology are: (1) The water-resisting coal and rock pillars cannot be reused, resulting in a large amount of coal pillar resources becoming stagnant resources that cannot be mined, reducing the utilization rate of coal resources; (2) There must be a continuous water-resisting layer with a certain width in the water-resisting coal and rock pillars. However, the deep and large faults forming the graben structure are often accompanied by a large number of secondary faults. The water-conducting secondary faults damage the continuity of the water-resisting layer, forming a channel for the aquifer water to burst into the mine, causing the water-resisting coal and rock pillars to lose their water-resisting function locally, and there is still a risk of water inrush in coal mining in this area.

[0003] Therefore, in view of the above problems and disadvantages, through painstaking research and design, and integrating the experience and achievements of many years in related professions, the invention researches and designs a water disaster control method for coal seam mining in a water-rich graben structure to overcome the defects existing in the prior art. Summary of the Invention

[0004] The purpose of the invention is to provide a water disaster control method and a construction method for coal seam mining in a water-rich graben structure, which solves the problems of low utilization rate of coal resources and local loss of water-resisting property of water-resisting coal and rock pillars caused by secondary water-conducting faults associated with deep and large faults in the prior art.

[0005] The technical solution adopted by the invention is as follows:

[0006] A water disaster control method for coal seam mining in a water-rich graben structure includes:

[0007] Step 1: Determine the type of water-rich graben according to the occurrence of the fault and the relative position relationship between the coal seam and the aquifer;

[0008] Type I: The coal seam is connected to the lateral aquifer on both sides;

[0009] Type II: One side of the coal seam is connected to the lateral aquifer, and the other side is close to the lateral aquifer;

[0010] Type III: Both sides of the coal seam are close to the lateral aquifer;

[0011] Type IV: There is an aquifer at the coal seam floor and the thickness of the water-resisting layer is insufficient;

[0012] The discrimination criterion for the coal seam being close to the lateral aquifer is:

[0013] H < (P 1 / T s +h p ) / cosβ;

[0014] The discrimination criterion for the insufficient thickness of the floor water-resisting layer is:

[0015] H di <(P 2 / T s +h p ) / cosβ;

[0016] In the formula: H - the vertical distance from the bottom interface of the coal seam to the intersection line of the top interface of the lateral aquifer and the fault plane, m; P 1 - the water pressure of the lateral aquifer, MPa; P 2 - the water pressure of the floor aquifer, MPa; T s - the critical water inrush coefficient, MPa / m; h p - the depth of floor failure, m; H di - the vertical distance from the bottom interface of the coal seam to the top interface of the floor aquifer, m; β - the dip angle of the coal seam, °;

[0017] Step 2: Determine the treatment scope according to the type of water-rich graben;

[0018] (1) The treatment height of the lateral aquifer connected to the coal seam: the depth of the distance H d from the top interface of the aquifer to the bottom of the coal seam;

[0019]

[0020] In the formula: H d - the vertical distance from the bottom interface of the treatment of the lateral aquifer connected to the coal seam to the bottom interface of the coal seam, m; K - safety factor, taking 2 - 5, M - coal mining height, m; K p - the tensile strength of coal, MPa; R - effective grouting radius, m; H t - the normal distance from the side drilling point of the fault treatment hole to the fault plane, taking 10 - 15 m; α - fault dip angle, °; h d - the ascending height of the lateral aquifer in the fault zone;

[0021] The width B for the treatment of the lateral aquifer connected to the coal seam is B = 2R + H t ;

[0022] (2) The treatment height of the lateral aquifer close to the coal seam: the distance H from the top interface of the aquifer to the bottom interface of the coal seam j depth;

[0023] H j =(P 1 / T s +h p ) / cosβ + h d ;

[0024] In the formula: H j - The vertical distance from the intersection line of the bottom interface of the treated lateral aquifer close to the coal seam and the fault to the bottom interface of the coal seam, m;

[0025] The treatment width is the same as that in (1);

[0026] (3) The treatment scope of the aquifer in the coal seam floor; all the aquifers in the coal seam floor with an outward expansion of 30 - 60 m outside the cutting hole and the stop line and between the two side faults;

[0027] For the thin limestone layer with a thickness of 5 - 20 m, the whole thickness is treated; for the thick limestone layer, the treatment height H z =P 2 / T s +h p -h g ;

[0028] In the formula: h g —The thickness of the water - resistant layer above the aquifer in the coal seam floor, m.

[0029] Optionally, the type I, type II and type III can be combined with type IV respectively to form type I - IV, type II - IV and / or type III - IV.

[0030] A construction method for water disaster treatment in coal seam mining within a water - rich graben structure, and the construction method is used to implement the water disaster treatment method for coal seam mining within the water - rich graben structure of the present invention.

[0031] Optionally, it includes:

[0032] Step 1: Construct short branch holes for fault treatment; for each hole group, construct 3 - 5 short branch holes for fault treatment, and the main axis of the fault treatment hole is parallel to the fault plane to identify the position of the fault;

[0033] Step 2: Construct grouting holes for the lateral aquifer; for each hole group, construct N grouting holes for the lateral aquifer. The grouting holes for the lateral aquifer and the main axis of the fault treatment hole are arranged in a three - flower pattern. First, construct the upper branch holes, and then construct the lower branch holes;

[0034] Step 3: Construct the grouting holes for the aquifer of the floor slab;

[0035] Construct from the footwall of the fault into the aquifer within the graben block segment, arranged in a comb shape. The grouting holes for the aquifer of the floor slab extend the short branch holes for fault treatment in the aquifer of the floor slab, and the two are set jointly.

[0036] Optionally, the plane where the lateral aquifer grouting holes are located is parallel to the fault plane, and the hole spacing is 2R;

[0037] The normal distance between the main axis of the fault treatment hole and the plane where the two lateral aquifer grouting holes are located is R;

[0038] The length of the lateral aquifer grouting holes is 400 - 500 m, and the grouting section length is 150 - 250 m.

[0039] Optionally, the normal distance between the main axis of the fault treatment hole and the fault plane is 10 - 15 m. Along the direction of the main axis of the fault treatment hole, a short branch hole for fault treatment is drilled laterally towards the fault plane every 150 - 200 m, passing through the fault plane by 30 - 50 m.

[0040] Optionally, the hole spacing of the grouting holes for the aquifer of the floor slab is 50 - 70 m;

[0041] Grout in two stages: grout once for 10 - 20 m through the fault, and grout once at the end of the hole.

[0042] Optionally, in Steps 1 - 3, the termination grouting pressure is that the orifice pressure reaches 3 - 4 times the water pressure of the aquifer to be treated. The grouting end standard is that the flow rate is less than 50 L / min, the termination grouting pressure is reached, and it is stable for 20 - 30 min.

[0043] Optionally, it further includes Step 4: Construct inspection holes; construct an inspection hole from the lateral aquifer grouting hole group, longitudinally penetrating the entire treatment height range from top to bottom, and transversely passing through the fault plane by 30 - 50 m;

[0044] Construct an inspection hole from the fault treatment hole group, longitudinally penetrating the entire treatment height range from top to bottom, and transversely passing through a distance of R - 1.5R from the plane where the lateral aquifer grouting holes are located.

[0045] Optionally, conduct a water pressure test for the inspection holes every 100 - 150 m. The water pressure test pressure reaches 1.0 - 1.2 times the termination grouting pressure. If the water absorption is less than 50 L / min, it is qualified; otherwise, supplementary grouting is carried out using the inspection holes.

[0046] The beneficial effects of the present invention are:

[0047] (1) By grouting and transforming the lateral aquifer within a set range into an impermeable layer, the transformed formation serves as a water-resisting rock pillar. Meanwhile, the fault is grouted and transformed into a non-water-conducting fault. After the transformation, a coal pillar is left according to the non-water-conducting fault, significantly shortening the width of the coal pillar, enabling the recovery of coal pillar resources, improving the utilization rate of coal resources, increasing the economic benefits of the mine, and extending the mine life.

[0048] (2) The present invention realizes the integration of exploration, treatment, and verification of "water source - passage", providing a safe geological guarantee for the mine from the perspective of water prevention and control. By grouting, an impermeable curtain is formed in the lateral and floor aquifers of the coal seam, sealing the water - filling source; borehole exploration is carried out on the main fault forming the graben structure, eliminating the fault error caused by geophysical exploration, accurately depicting and positioning the fault morphology and location, providing accurate data for coal pillar setting; by grouting the main fault and secondary faults, the water - conducting channels are comprehensively sealed, eliminating water hazards and ensuring the safe mining of the coal seam. Brief Description of the Drawings

[0049] Figure 1 It is a cross - sectional view of the calculation of the treatment range of the lateral aquifer connected to the coal seam and the layout of fault treatment holes and grouting holes;

[0050] Figure 2 It is a cross - sectional view of the calculation of the treatment range of the lateral aquifer close to the coal seam and the layout of fault treatment holes and grouting holes;

[0051] Figure 3 It is a cross - sectional view of the layout of fault treatment holes and grouting holes in the presence of a coal seam floor aquifer;

[0052] Figure 4 It is a cross - sectional view of the layout of boreholes for treating water hazards in type - I water - rich graben;

[0053] Figure 5 It is a cross - sectional view of the layout of boreholes for treating water hazards in type - II water - rich graben;

[0054] Figure 6 It is a cross - sectional view of the layout of boreholes for treating water hazards in type - III water - rich graben;

[0055] Figure 7 It is a cross - sectional view of the layout of boreholes for treating water hazards in type - I - IV water - rich graben;

[0056] Figure 8 It is a cross - sectional view of the layout of boreholes for treating water hazards in type - II - IV water - rich graben;

[0057] Figure 9 It is a cross - sectional view of the layout of boreholes for treating water hazards in type - III - IV water - rich graben;

[0058] Figure 10 It is a cross - sectional view of the layout of inspection holes;

[0059] Figure 11It is the projection of the borehole on the horizontal plane;

[0060] Figure 12 is a cross-sectional view of a borehole in Example 1;

[0061] The numbers in the figure are as follows: 1-coal seam, 2-lateral aquifer, 3-fault, 4-fault management hole, 5-lateral aquifer grouting hole, 6-bottom plate aquifer, 7-bottom plate aquifer grouting hole, 8-inspection hole, 9-fault management hole main axis, 10-side drilling point. DETAILED DESCRIPTION

[0062] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0063] The water-rich graben structure refers to a trough-shaped block structure formed by coal-bearing blocks surrounded by high-angle faults on both sides, and rock strata rich in groundwater are developed or connected by faults on both sides.

[0064] The method for controlling water damage in coal seam mining in a water-rich graben structure of the present invention comprises:

[0065] The complete steps of the method of the present invention are described

[0066] Step 1: Determine the type of water-rich graben based on the occurrence of faults and the relative position relationship between coal seams and aquifers identified by geophysical exploration and drilling;

[0067] Based on the above parameters, the method to determine the type of water-rich graben is:

[0068] Type I: Both sides of the coal seam are connected to the lateral aquifer;

[0069] Type II: One side of the coal seam butts against the lateral aquifer, and the other side is close to the lateral aquifer;

[0070] Type III: Both sides of the coal seam are close to lateral aquifers;

[0071] Type IV: There is a coal seam floor aquifer and the thickness of the aquiclude is insufficient;

[0072] The criteria for determining whether a coal seam is close to a lateral aquifer are:

[0073] H<(P 1 / T s +h p ) / cosβ;

[0074] The criteria for judging whether the thickness of the bottom waterproof layer is insufficient are:

[0075] H di (P 2 / T s +h p ) / cosβ;

[0076] Where: H is the vertical distance between the bottom interface of the coal seam and the top interface of the lateral aquifer and the intersection line of the fault plane, m; P 1 - Lateral aquifer water pressure, MPa; P 2 -Water pressure of bottom aquifer, MPa; T s -Critical water inrush coefficient, MPa / m; h p -Deepness of bottom plate damage, m; H 底 -Vertical distance between the bottom interface of coal seam and the top interface of floor aquifer, m; β-inclination angle of coal seam, °.

[0077] In addition, I, II, and III can be combined with type IV to form type I-IV, type II-IV, and type III-IV, respectively.

[0078] Step 2: Determine the scope of governance

[0079] (1) Figure 1 , the management height of the lateral aquifer connected to the coal seam: the distance H from the top interface of the aquifer to the bottom interface of the coal seam d Depth.

[0080]

[0081] Where: H d -The vertical distance between the bottom interface of the lateral aquifer treatment connecting with the coal seam and the bottom interface of the coal seam, m; K-safety factor, take 2 to 5, M-coal seam mining height, m; K p - tensile strength of coal, MPa; R- effective grouting radius, m; H t -The normal distance between the side drilling point of the fault control hole and the fault plane, which is 10-15m; α-fault dip, °; h d - The height of the lateral aquifer in the fault zone.

[0082] The width of the lateral aquifer management is B = 2R + H t ;

[0083] (2) Figure 2 , the treatment height of the lateral aquifer close to the coal seam: the distance H from the top interface of the aquifer to the bottom interface of the coal seam j Depth

[0084] H j =(P 1 / T s +h p ) / cosβ+h d ;

[0085] Where: H j -The vertical distance between the bottom interface of the lateral aquifer treatment close to the coal seam and the bottom interface of the coal seam, m.

[0086] The width of governance is the same as in (1).

[0087] (3) As Figure 3 , the treatment scope of the aquifer at the coal seam floor

[0088] covers all the floor aquifers between 30 - 60 m outside the cutting roadway and the end - stop line and the faults on both sides.

[0089] For the thin - bedded limestone (5 - 20 m), the whole thickness is treated; for the thick - bedded limestone, the treatment height H z = P 2 / T s + h p - h g ;

[0090] In the formula: h g — the thickness of the water - resisting layer above the floor aquifer, m.

[0091] The construction method specifically includes:

[0092] The boreholes are arranged within the treatment scope. The arrangement method is as follows. The diffusion range of borehole grouting should be able to control the above - mentioned treatment scope. For this purpose, the distances from the top and bottom boreholes of the lateral aquifer grouting holes to the top and bottom of the treatment scope should be less than R. A short branch for fault treatment should be set at the top of the lateral aquifer close to the coal seam. The floor aquifer grouting holes are set according to the description. Similar to the treatment of the floor area, single - layer grouting holes are arranged for the thin - bedded limestone, and multi - layer grouting holes are arranged for the thick - bedded limestone.

[0093] Step 1: Construct the short branch holes for fault treatment

[0094] As Figures 1 - 2 , the main axis of the fault treatment hole is parallel to the fault plane, and the normal distance from the fault plane is 10 - 15 m. Along the direction of the main axis of the fault treatment hole, a short branch hole for fault treatment is drilled laterally towards the fault plane every 150 - 200 m, passing through the fault plane by 30 - 50 m to identify the position of the fault.

[0095] Step 2: Construct the lateral aquifer grouting holes

[0096] As Figures 1 - 2 , N lateral aquifer grouting holes are constructed for each hole group. The lateral aquifer grouting holes and the main axis of the fault treatment hole are arranged in a three - flower pattern. The upper branch holes are constructed first, and then the lower branch holes are constructed.

[0097] The plane where the lateral aquifer grouting holes are located is parallel to the fault plane, and the hole spacing is 2R.

[0098] The normal distance from the main axis of the fault treatment hole to the plane where the two lateral aquifer grouting holes are located is R.

[0099] The length of the lateral aquifer grouting holes is 400 - 500 m, and the grouting section length is 150 - 250 m.

[0100] Step 3: Construct the grouting holes in the aquifer of the floor

[0101] Such as Figure 3 、 Figures 7 - 9 、 Figure 11 , construct from the footwall of the fault into the aquifer in the graben block, arrange in a comb shape, and the hole spacing is 50 - 70m. Grout in two stages: grout once for 10 - 20m through the fault and once at the end of the hole.

[0102] The grouting holes in the aquifer of the floor extend the short branch of the fault treatment in the aquifer of the floor, and the two are set jointly.

[0103] In the construction methods of Step 1 - Step 3, the termination grouting pressure is 3 - 4 times the water pressure of the aquifer to be treated at the orifice pressure, and the grouting end standard is that the flow rate is less than 50L / min, reaching the termination grouting pressure and stabilizing for 20 - 30min.

[0104] Such as Figures 4 - 9 is the layout section of the water hazard treatment boreholes for six types of water - rich grabens.

[0105] Step 4: Construct inspection holes

[0106] Such as Figure 10 , construct an inspection hole from the lateral aquifer grouting hole group, longitudinally penetrate the entire treatment height range from top to bottom, and transversely penetrate 30 - 50m through the fault plane. Construct an inspection hole from the fault treatment hole group, longitudinally penetrate the entire treatment height range from top to bottom, and transversely penetrate a distance of R - 1.5R through the plane where the lateral aquifer grouting holes are located.

[0107] Conduct a water pressure test on the inspection hole every 100 - 150m. The water pressure test pressure reaches 1.0 - 1.2 times the termination grouting pressure, and if the water absorption is less than 50L / min, it is qualified. Otherwise, use the inspection hole for supplementary grouting.

[0108] Example 1:

[0109] A coal mine in Shandong has developed a coal-bearing graben structure consisting of two faults, F3 and F6, and plans to arrange a coal mining face between the F3 and F6 faults. The F3 fault has a dip angle of 70°, a drop of 50-150m, cuts with multiple faults, and extends for about 1,850m in the area, running through the entire area; the F6 fault has a dip angle of 60°, a drop of 70-210m, strikes northwest, dips to the southwest, cuts with multiple faults, and extends for about 2,730m in the area. At the coal seam elevation, the distance between the two faults is 285m. The fault causes the lower plate Aohui aquifer to rise. On the F6 fault side, the Aohui aquifer and the 14th gray aquifer directly connect with the upper plate coal seam, forming a direct water-filled structure, which poses a threat to coal seam mining. On the F3 fault side, the Aohui aquifer is located at the bottom plate of the coal seam, which is relatively close. The bottom plate Sanhui aquifer is about 47m away from the coal seam, with a thickness of 5.6m and a maximum water pressure of 5MPa. During the excavation and mining process of the working face, it is mainly threatened by the lateral limestone water of the lower plate of the fault and the limestone water of the bottom plate. The main water-filled aquifers are Aohui, Sanhui and 14th gray. Among them, the static water pressure of the Aohui aquifer is 4.3MPa, the unit water inflow is 0.0598~1.580L / (s·m), the water-richness is weak to strong, and it poses the greatest threat to the safe mining of the coal seam.

[0110] If you want to achieve safe coal mining, you need to set up a waterproof coal pillar. According to calculations, you need to set up a 100m waterproof coal pillar, and the remaining working face width is only 13-102m. Not only is the working face difficult to design and recover, but it will also cause a lot of coal resources to be wasted. In order to eliminate the threat of floor and lateral water damage, and at the same time liberate the coal pillar resources of the working face and improve resource utilization, the present invention was used to implement water damage control, liberating 2.01 million tons of resource reserves.

[0111] Step 1: Determine the type of water-rich graben based on the occurrence of faults and the relative position of coal seams and aquifers identified by geophysical exploration and drilling.

[0112] The F6 fault has a dip angle of 60° and a drop of 70 to 210 m. The Ordovician aquifer is lifted to the point where it connects with the coal seam. The F3 fault has a dip angle of 70° and a drop of 50 to 150 m. The water pressure of the Ordovician aquifer is P 1 =4.3MPa, water pressure of the three-ash aquifer P 2 =4.3MPaThe critical water inrush coefficient is 0.06MPa / m, the floor failure depth is 21m, the coal seam inclination is 14°, H=61m<(P 1 / T s +h p ) / cosβ=95.5m, that is, the Ordovician gray aquifer is close to the coal seam. There is a three-gray aquifer on the bottom of the coal seam, and the thickness of the aquiclude is H di =47m<(P 2 / Ts+hp) / cosβ=107.5m, the thickness of the aquiclude is insufficient. Based on this, it is classified as type II-IV water-rich graben.

[0113] Step 2: Determine the treatment scope

[0114] (1) As Figure 12 , on one side of the F6 fault, the treatment height of the lateral Ordovician limestone aquifer connected to the coal seam: the distance H from the top interface of the aquifer to the bottom interface of the coal seam d is the depth of.

[0115]

[0116] In the formula: K - safety factor, taking 4, M - coal seam mining height, 6.5 m; K p - tensile strength of coal, 0.6 MPa; R - effective grouting radius, taking 15 m; H t - normal distance from the side drilling point of the fault treatment hole to the fault plane, taking 10 m; h d - ascending height of the lateral aquifer in the fault zone, taking 8 m.

[0117] The width B of the lateral aquifer treatment = 2R + H t = 40 m;

[0118] (2) As Figure 12 , on one side of the F3 fault, the treatment height of the lateral aquifer close to the coal seam: the distance H from the top interface of the aquifer to the bottom interface of the coal seam j is the depth of.

[0119] H j = (P 1 / T s + h p ) / cosβ + h d = 103.5 m;

[0120] In the formula: H j - vertical distance from the bottom interface of the lateral aquifer treatment close to the coal seam to the bottom interface of the coal seam, m.

[0121] The treatment width is the same as that in (1).

[0122] (3) As Figure 3 , the treatment scope of the coal seam floor aquifer;

[0123] All the floor aquifers between 30 - 60 m outside the cutting hole and the stop line and the two - side faults.

[0124] The thickness of the floor third - layer limestone aquifer is 5.6 m, belonging to thin - layer limestone. Use the floor aquifer grouting hole for bedding drilling and treat the whole thickness.

[0125] Step 3: Construct the short branch holes for fault treatment

[0126] As Figure 11, the main axis of the fault treatment hole is parallel to the fault plane, and the normal distance from the fault plane is 10 m. Along the main axis direction of the fault treatment hole, a short branch hole for fault treatment is drilled laterally towards the fault plane every 150 m, passing through the fault plane by 40 m to identify the position of the fault. Two short branch holes for fault treatment are set on one side of the F6 fault, and one short branch hole for fault treatment is set on one side of the F3 fault. The length of each short branch hole is 160 m.

[0127] Step 4: Construct lateral aquifer grouting holes

[0128] As Figure 11 , two lateral aquifer grouting holes are constructed on one side of the F6 fault, and one lateral aquifer grouting hole is constructed on one side of the F3 fault. The lateral aquifer grouting holes and the main axis of the fault treatment hole are arranged in a three-flower pattern. First, the upper branch holes are constructed, and then the lower branch holes are constructed.

[0129] The plane where the lateral aquifer grouting holes are located is parallel to the fault plane, and the hole spacing is 30 m.

[0130] The normal distance between the main axis of the fault treatment hole and the plane where the two lateral aquifer grouting holes are located is 15 m.

[0131] The length of the lateral aquifer grouting hole is 500 m, and the grouting section length is 200 m.

[0132] Step 5: Construct floor aquifer grouting holes

[0133] They are respectively constructed from the footwalls of the F6 fault and the F3 fault into the aquifer in the graben block section, arranged in a comb shape, and the hole spacing is 70 m. Grouting is carried out in two stages: grouting once every 15 m through the fault and grouting once at the end of the hole.

[0134] In Steps 3 to 5, the termination grouting pressure is that the hole mouth pressure reaches 3 times the water pressure of the aquifer to be treated, that is, 13 MPa. The grouting end standard is that the flow rate is less than 50 L / min, the termination grouting pressure is reached, and it is stable for 20 min.

[0135] Step 6: Construct inspection holes

[0136] As Figure 11 , an inspection hole is constructed from the lateral aquifer grouting hole group, longitudinally penetrating the entire treatment height range from top to bottom, and transversely passing through the fault plane by 50 m. An inspection hole is constructed from the fault treatment hole group, longitudinally penetrating the entire treatment height range from top to bottom, and transversely passing through the plane where the lateral aquifer grouting holes are located by a distance of 15 m.

[0137] A water pressure test is carried out for the inspection hole every 100 m. The water pressure test pressure reaches 15 MPa, and if the water absorption is less than 50 L / min, it is qualified. Otherwise, supplementary grouting is carried out using the inspection hole.

[0138] In this embodiment, 4 pairs of 8 hole groups are constructed in the direction of the F6 fault (i.e., one fault control hole group and one lateral aquifer grouting hole group for each pair), and 3 hole groups are constructed in the direction of the F3 fault. The length of the control area for each hole group is about 500 m. A total of 11 hole groups are constructed, including 16 short branch holes for fault control, 33 lateral aquifer grouting holes, 19 floor aquifer grouting holes, and 11 inspection holes.

[0139] According to the "Regulations on the Prevention and Control of Water in Coal Mines", the width of the waterproof and water-resisting coal and rock pillar for the F6 fault needs to be 71.8 - 87.5 m (increasing with the increase of coal seam burial depth), and the width of the waterproof and water-resisting coal and rock pillar for the F3 fault needs to be 46 - 56 m (increasing with the increase of coal seam burial depth). After treatment with the present invention, the coal and rock pillar of the F6 fault is shortened by 27 m, and the width of the remaining waterproof and water-resisting coal and rock pillar after treatment is 44.8 - 60.5 m; the coal pillar of the F3 fault is calculated according to the waterproof fault, with 20 m reserved, and it is shortened by 26 - 36 m. After shortening the width of the coal and rock pillar with the present invention, the working face width is increased by 46 - 56 m, and the recoverable coal pillar resource reserve is 2.01 million t, which can increase the mine revenue by about 2 billion yuan.

[0140] The above preferentially elaborates the best embodiments in detail in combination with the drawings, and is not used to limit the present invention. For the above-described various specific technical features, they can be combined in any suitable form without contradiction, and the present invention will not elaborate one by one. Any simple modifications or decorations such as arbitrary combinations or equivalent replacements of the technical solutions by any person skilled in the art without departing from the scope of the technical solutions do not affect the essence of the technical solutions, and still fall within the protection scope of the technical solutions represented by the embodiments of the present invention.

Claims

1. A method for controlling water hazards in coal seam mining in a water-rich graben structure. It is characterized in that include: Step 1: Determine the type of water-rich graben based on the occurrence of the fault and the relative position between the coal seam and the aquifer; Type I: Both sides of the coal seam are connected to the lateral aquifer; Type II: One side of the coal seam butts against the lateral aquifer, and the other side is close to the lateral aquifer; Type III: Both sides of the coal seam are close to lateral aquifers; Type IV: There is an aquifer in the coal seam floor and the thickness of the aquiclude is insufficient; The criteria for determining whether a coal seam is close to a lateral aquifer are: H < (P 1 / T s + h p ) / cosβ; The criteria for judging whether the thickness of the bottom waterproof layer is insufficient are: H di <(P 2 / T s +h p ) / cosβ; Where: H—the vertical distance between the bottom interface of the coal seam and the intersection line of the top interface of the lateral aquifer and the fault plane, m; P 1 —the water pressure of the lateral aquifer, MPa; P 2 —the water pressure of the floor aquifer, MPa; T s —the critical water inrush coefficient, MPa / m; h p —the floor failure depth, m; H di —the vertical distance between the bottom interface of the coal seam and the top interface of the floor aquifer, m; β—the dip angle of the coal seam, °; Step 2: Determine the scope of treatment according to the type of water-rich graben; 2.1 Governing height of the lateral aquifer connected to the coal seam: the depth of the distance from the top interface of the aquifer to the bottom interface of the coal seam H d ; ； In the formula: H d — The vertical distance between the bottom interface for treating the lateral aquifer connected to the coal seam and the bottom interface of the coal seam, m; K — Safety factor, taking 2 - 5, M — Mining height of the coal seam, m; K p — Tensile strength of coal, MPa; R — Effective grouting radius, m; H t — Normal distance from the side drilling point of the fault treatment hole to the fault plane, taking 10 - 15 m; α — Fault dip angle, °; h d — Ascending height of the lateral aquifer in the fault zone, m; P 1 — Water pressure of the lateral aquifer, MPa; Width of treatment for lateral aquifers connected to coal seams ; 2.2 Governing height of the lateral aquifer close to the coal seam: the depth of the distance from the top interface of the aquifer to the bottom interface of the coal seam H j ; ； In the formula: H j — The vertical distance from the intersection line of the bottom interface for controlling the lateral aquifer close to the coal seam and the fault to the bottom interface of the coal seam, m; P 1 — The water pressure of the lateral aquifer, MPa; T s — The critical water inrush coefficient, MPa / m; h p — The depth of floor failure, m; β — The dip angle of the coal seam, °; h d — The ascending height of the lateral aquifer in the fault zone, m; The width of governance is the same as in 2.1; 2.3 The scope of treatment of coal seam floor aquifers: 30 to 60 m outside the cut-off and stop-mining lines and all floor aquifers between the faults on both sides; The thin limestone layer with a thickness of 5 to 20 m is treated for the full thickness; the treatment height H of the thick limestone layer z =P 2 / T s +h p -h g , m; where: h g — the thickness of the water-resisting layer above the floor aquifer, m, P 2 — the water pressure of the floor aquifer, MPa; T s — Critical water inrush coefficient, MPa / m; h p — Failure depth of the floor, m; The construction process of the water hazard control method for coal seam mining in a water-rich graben structure includes: Step A: construct short branch holes for fault management; construct 3 to 5 short branch holes for fault management in each hole group, with the main axis of the fault management hole parallel to the fault plane, to find out the location of the fault; Step B: construct lateral aquifer grouting holes; construct N lateral aquifer grouting holes in each hole group, and the main axes of the lateral aquifer grouting holes and the fault management holes are arranged in a three-flower pattern, with the upper branch holes constructed first and the lower branch holes constructed later; Step C: construct grouting holes for the aquifer in the bottom plate; Construction is carried out from the footwall of the fault to the aquifer in the graben block section, with a comb-like arrangement. The grouting holes in the bottom plate aquifer extend the short branch holes for fault management in the bottom plate aquifer, and the two are set together.

2. The method for controlling water damage in coal seam mining in a water-rich graben structure according to claim 1, It is characterized in that The plane where the lateral aquifer grouting holes are located is parallel to the fault plane, and the hole spacing is 2R; The normal distance between the main axis of the fault control hole and the plane where the two lateral aquifer grouting holes are located is R; The length of the lateral aquifer grouting hole is 400 to 500 m, and the length of the grouting section is 150 to 250 m.

3. The method for controlling water damage in coal seam mining in a water-rich graben structure according to claim 1 or 2, It is characterized in that The normal distance between the main axis of the fault management hole and the fault plane is 10-15m, and a short branch hole for fault management is side-drilled every 150-200m along the main axis of the fault management hole toward the fault plane, passing through the fault plane for 30-50m.

4. The method for controlling water damage in coal seam mining in a water-rich graben structure according to claim 1 or 2, It is characterized in that The spacing between the grouting holes of the bottom plate aquifer is 50 to 70 m; The grouting is divided into two stages: one grouting when 10 to 20 meters through the fault, and one grouting at the end of the hole.

5. The method for controlling water damage in coal seam mining in a water-rich graben structure according to claim 1 or 2, It is characterized in that The termination grouting pressure in steps A to C is when the orifice pressure reaches 3 to 4 times the water pressure of the aquifer to be treated. The grouting termination standard is when the flow rate is less than 50L / min, the termination grouting pressure is reached, and it is stable for 20 to 30 minutes.

6. The method for controlling water damage in coal seam mining in a water-rich graben structure according to claim 1 or 2, It is characterized in that It also includes step D: construction inspection hole; construct an inspection hole from a lateral aquifer grouting hole group, longitudinally penetrating the entire treatment height range from top to bottom, and transversely passing through the fault plane by 30 - 50 m; Construct an inspection hole from a fault treatment hole group, longitudinally penetrating the entire treatment height range from top to bottom, and transversely passing through a distance of R - 1.5R from the plane where the lateral aquifer grouting holes are located.

7. The water disaster control method for coal seam mining in a water-rich graben structure according to claim 6, characterized in that, for the said inspection hole, a water pressure test is carried out every 100 - 150 m, the water pressure test pressure reaches 1.0 - 1.2 times the grouting termination pressure, and if the water absorption is less than 50 L / min, it is qualified; otherwise, supplementary grouting is carried out using the inspection hole.

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