A water-saving coal mining method in sandstone strong runoff area

Abstract

A water-conserving coal mining method for sandstone high-runoff areas includes the following steps: drawing a natural gamma logging contour map using an interpolation method, selecting the location of a large-diameter drainage borehole within the minimum interval of the natural gamma logging contour map; then determining the amount of water to be discharged from the sandstone high-runoff area, the permeability coefficient of the area where the large-diameter drainage borehole is located, the maximum discharge capacity of a single large-diameter drainage borehole, the number of large-diameter drainage boreholes, and the final borehole diameter for pumping water; then, implementing large-diameter drainage drilling, and implementing small-diameter interconnecting boreholes around the large-diameter drainage borehole locations; finally, continuously pumping water at the maximum pumping capacity using the large-diameter drainage borehole, leaving a coal pillar in the large-diameter drainage borehole, and conducting exploration and drainage of water in the sandstone aquifer before coal mining. This method can effectively reduce the impact of heterogeneity, achieve good drilling and drainage effects, is not easily affected by geological conditions, has a wide range of applications, can prevent the discharged water resources from being contaminated, and is simple and easy to implement.

Description

Technical Field

[0001] The invention relates to a water-retaining coal mining method in a sandstone strong runoff area, belonging to the technical field of coal mine safety mining. Background Art

[0002] As coal mining strategies shift westward, the ecological environment in western China is fragile and water resources are scarce, leading to an increasing conflict between coal mining and water resource protection. Water-conserving coal mining is the primary means of resolving this conflict. Among the protected areas, the roof sandstone aquifer is currently the largest source of water. Locally, the roof sandstone aquifer is highly water-rich, forming a sandstone high-runoff zone. For this type of water body, mines often use drainage, underground forced drainage, and grouting curtains to protect and utilize water resources. However, these traditional methods have the following problems:

[0003] (1) Due to the heterogeneity of sandstone aquifers, small-diameter drainage often leads to poor drilling and drainage effects when implemented in water-free areas, and it is impossible to protect the main sandstone aquifers in advance;

[0004] (2) Grouting curtain can solve the problem to a large extent, but plugging requires a large amount of grouting work. The strong runoff of sandstone drives the water grouting plugging construction to be difficult, and after plugging, water may flow into the mining space from other hidden channels, so the construction effect cannot be guaranteed;

[0005] (3) The freezing method can be implemented on groundwater with poor hydrodynamics, but freezing is difficult to complete under strong runoff conditions;

[0006] (4) Underground forced drainage will cause water resources to be polluted after entering the mine, which is not environmentally friendly. In addition, underground forced drainage requires a strong drainage system, which puts too much burden on the system and poses a safety hazard. Summary of the Invention

[0007] The object of the present invention is to provide a water-preserving coal mining method in a sandstone strong runoff area, which can effectively reduce the influence of heterogeneity and has a good drilling and drainage effect; is not easily affected by geological conditions and has a wide range of applications; can avoid the pollution of the discharged water resources; and is simple and easy to implement.

[0008] In order to achieve the above object, the present invention provides a water-retaining coal mining method in a sandstone high runoff area, comprising the following steps:

[0009] S1. Select the location of large-diameter drainage boreholes: Draw the natural gamma logging contour map by interpolation method, and select the location of large-diameter drainage boreholes within the minimum interval of the natural gamma logging contour map;

[0010] S2. Determine the amount of water Qz that should be discharged in the sandstone strong runoff area;

[0011] S3. Determine the permeability coefficient K of the area where the large-diameter drainage borehole is located;

[0012] S4. Determine the maximum drainage capacity Q1 of a single large-diameter drainage borehole;

[0013] S5. Determine the number of large-diameter drainage boreholes and the final borehole diameter for pumping water;

[0014] S6. Based on the location, number, and final diameter of the large-diameter drainage boreholes determined in S1 to S5, drill large-diameter drainage holes to 2 to 5 meters below the sandstone stratum floor. Leave permeable flower pipes in the sandstone stratum area and waterproof casings in other areas.

[0015] S7, conducting small-diameter connecting drilling around the location of the large-diameter drainage drill hole, wherein the location around the large-diameter drainage drill hole is less than a set value R;

[0016] S8. Use large-aperture drainage boreholes to continuously pump water at the maximum pumping capacity, leave a coal pillar L in the large-aperture drainage boreholes, and conduct coal mining after exploring and draining water from the sandstone aquifer.

[0017] Furthermore, the minimum interval of the natural gamma ray logging curve contour map in S1 refers to the 20% area with the smallest natural gamma ray logging values ​​in all exploration boreholes in the coal mining area.

[0018] Furthermore, in S2, the amount of water Qz to be discharged from the sandstone strong runoff area is calculated according to the following formula:

[0019]

[0020] Among them, Q0 is the water inflow that has been mined in the sandstone strong runoff area, obtained through underground observation; F0 is the area that has been mined in the sandstone strong runoff area, obtained through the coal mining design map; Fz is the total area of ​​sandstone strong runoff areas to be mined in the future, obtained through the coal mining design map; A is the average value of the natural gamma logging results in the mined area, obtained by drawing the natural gamma logging contour map; B is the average value of the natural gamma logging results in the future mining area, obtained by drawing the natural gamma logging contour map.

[0021] Furthermore, the method for determining the permeability coefficient K of the area where the large-diameter drainage borehole is located in S3 is as follows: rock samples of the sandstone strong runoff area in the area where the large-diameter drainage borehole is located are collected, and rock sample thin sections are prepared. The average particle size d of the sand particles is measured using IPP software, and the permeability coefficient K is calculated using the following formula:

[0022]

[0023] Among them, γ Sis the average specific gravity of sand particles in sandstone, obtained through testing; n is the reduction coefficient, which is taken as 0.0001~0.001; γ is the specific gravity of water, which is taken as 1000 kg / m3; d is the average particle size of sand particles, obtained through thin section testing; h is the depth of ancient river water, generally taken as 0.1~5 meters, obtained through natural gamma logging contour map; I is the natural gradient of the sandstone formation bottom, which is calculated through drilling histogram.

[0024] Furthermore, the maximum drainage capacity Q1 of a single large-diameter drainage borehole in S4 is calculated by the following formula:

[0025]

[0026] Where K is the permeability coefficient; M is the thickness of the sandstone aquifer, which is obtained through the borehole histogram; S is the height of the sandstone aquifer head from the sandstone formation bottom, which is obtained through hydrological observation.

[0027] Furthermore, the method for determining the number of large-diameter drainage boreholes and the final hole diameter for pumping water in S5 is as follows: when f≤1, the number of large-diameter drainage boreholes is 1, and the final hole diameter is ≥1000mm; when f>1, the number of large-diameter drainage boreholes is the integer of f value rounded up to one, and the final hole diameter is ≥1000mm; f is calculated according to the following formula:

[0028]

[0029] Among them, Qz is the water volume that should be discharged in the sandstone strong runoff area; Q1 is the maximum discharge volume of a single large-diameter drainage borehole.

[0030] Furthermore, the periphery of the position in S7 is a distance from the large-diameter drainage borehole less than a set value R, and R is calculated according to the following formula:

[0031]

[0032] Where S is the height of the water head of the sandstone aquifer from the bottom of the sandstone formation, obtained through hydrological observation; K is the permeability coefficient;

[0033] The small-diameter interconnected boreholes are deep enough to connect all strata within the height H of the coal mining water-conducting fracture zone, and all of them are equipped with permeable flower pipes. The height H of the coal mining water-conducting fracture zone is calculated using the following formula:

[0034]

[0035] In the formula, m is the coal mining thickness, which is obtained from the mining design drawing.

[0036] Furthermore, the calculation of the coal pillar L left by the large-diameter drainage drilling hole in S8 is based on the following formula:

[0037]

[0038] Where C is the safety factor, which is 3 to 5; m is the mining thickness, which is obtained from the mining design drawing; p is the hydrostatic pressure, p = ρgS, ρ is the water density, S is the height of the water head of the sandstone aquifer from the bottom of the sandstone formation, which is obtained through hydrological observation; v is the groundwater flow velocity, v = K × I, K is the permeability coefficient; I is the natural gradient of the sandstone formation bottom, which is obtained by calculating the borehole histogram; K p It is the tensile strength of the coal body, obtained through sampling test.

[0039] The present invention draws a natural gamma logging contour map through an interpolation method, and the location of a large-diameter drainage borehole is selected in the minimum interval of the natural gamma logging result contour map; then, after determining the amount of water to be discharged in a sandstone strong runoff area, the permeability coefficient of the area where the large-diameter drainage borehole is located, the maximum drainage capacity of a single large-diameter drainage borehole, the number of large-diameter drainage boreholes and the final hole diameter for pumping, the large-diameter drainage drilling is carried out, and small-diameter connecting drilling is carried out around the large-diameter drainage borehole location. Finally, the large-diameter drainage borehole is used to continuously pump water at the maximum pumping volume, a coal pillar is left in the large-diameter drainage borehole, and coal mining is carried out after the sandstone aquifer is explored and drained. The present invention does not require large-scale curtain grouting projects, but only requires the implementation of drainage drilling and the estimation of groundwater flow rate through sedimentology and hydraulic principles. It does not require many exploration holes and is simple and easy to implement. Compared with small-diameter boreholes, large-diameter boreholes can effectively reduce the influence of heterogeneity, avoid local impermeable layers, and have a better water drainage effect. The drained water resources do not pass through the mining system, avoid pollutants such as oil, and are more environmentally friendly. Fundamentally, drainage reduces the water source for flooding and has better safety. It is not affected by various complex geological conditions, such as the richness of the aquifer, water flow rate, etc., and has a wider range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0041] The present invention will be further described below with reference to the accompanying drawings.

[0042] like Figure 1 As shown, a water-preserving coal mining method in a sandstone strong runoff area includes the following steps:

[0043] S1. Select the location of large-diameter drainage boreholes: Draw the natural gamma logging contour map by interpolation method, and select the location of large-diameter drainage boreholes within the minimum interval of the natural gamma logging contour map;

[0044] S2. Determine the amount of water Qz that should be discharged in the sandstone strong runoff area;

[0045] S3. Determine the permeability coefficient K of the area where the large-diameter drainage borehole is located;

[0046] S4. Determine the maximum drainage capacity Q1 of a single large-diameter drainage borehole;

[0047] S5. Determine the number of large-diameter drainage boreholes and the final borehole diameter for pumping water;

[0048] S6. Based on the location, number, and final diameter of the large-diameter drainage boreholes determined in S1 to S5, drill large-diameter drainage holes to 2 to 5 meters below the sandstone stratum floor. Leave permeable flower pipes in the sandstone stratum area and waterproof casings in other areas.

[0049] S7, conducting small-diameter connecting drilling around the location of the large-diameter drainage drill hole, wherein the location around the large-diameter drainage drill hole is less than a set value R;

[0050] S8. Use large-aperture drainage boreholes to continuously pump water at the maximum pumping capacity, leave a coal pillar L in the large-aperture drainage boreholes, and conduct coal mining after exploring and draining water from the sandstone aquifer.

[0051] Example: The Yushenfu mining area is a major coal mining base in my country. A large amount of coal resources have been mined here, but there have been many water inrush accidents in the strong runoff zone of the roof sandstone. Existing exploration has shown the existence of an ancient river here. In the past, grouting curtains were used to block the river and force drainage underground, resulting in huge underground drainage costs and difficulties in grouting curtain engineering. The method of the present invention is applied to water-saving coal mining, and the specific steps are as follows:

[0052] Step 1: Select the location of the large-diameter drainage borehole: The location is selected in the minimum interval of the natural gamma logging result contour map (12-16 API). The minimum interval of the natural gamma logging curve contour map refers to the 20% area with the smallest natural gamma logging values ​​among all exploration boreholes in the coal mining area (total 12-80 API). The natural gamma logging contour map is drawn by interpolation method;

[0053] Step 2: Determine the amount of water Q to be discharged in the sandstone strong runoff area z , calculated according to the following formula:

[0054]

[0055] In the formula, Q0 is the water inflow that has been mined in the sandstone strong runoff area, which is 222m3 obtained through underground observation. 3 / h; F0 is the area that has been mined in the sandstone strong runoff area, obtained through coal mining design, which is 0.3km 2 Fz is the total area of ​​future sandstone strong runoff mining, obtained through coal mining design, which is 11.2km 2A is the average value of the natural gamma logging results of the mined area, obtained through step 1, which is 30 API; B is the average value of the natural gamma logging results of the future mined area, obtained through step 1, which is 14 API;

[0056] Step 3: Determine the permeability coefficient K of the area in step 1. Obtain rock samples from the sandstone strong runoff area in step 1, make rock sample thin sections, and use IPP software to measure the average sand particle size d = 0.0003 meters;

[0057]

[0058] In the formula, γ S is the average specific gravity of sand particles in sandstone, obtained through testing; γ is the specific gravity of water, taken as 1000 kg / m3; d is the average particle size of sand particles, obtained through thin section testing, taken as 17000 kg / m3; h is the depth of ancient river water, taken as 0.1 m; I is the natural gradient of the sandstone stratum floor, obtained through drilling histogram calculation, and is 0.1;

[0059] Step 4: Determine the maximum drainage capacity Q1 of a single large-diameter drainage borehole. The calculation formula is as follows:

[0060]

[0061] In the formula, K is the permeability coefficient, obtained in step 4, which is 21.4 m / d; M is the thickness of the sandstone aquifer, obtained from the borehole histogram, which is 10 meters; S is the height of the sandstone aquifer head from the sandstone formation floor, obtained through hydrological observation, which is 32 meters;

[0062] Step 5: Determine the number of large-diameter drainage boreholes and the final diameter of the pumping hole. Since f≤1, the number of large-diameter drainage boreholes is 1, and the final diameter is 1000mm or larger.

[0063]

[0064] Step 6: Carry out large-diameter drainage drilling according to the number, final hole diameter and location determined in the above steps. Drill the holes to 5 meters below the bottom of the sandstone formation. Leave permeable flower pipes in the sandstone formation area and waterproof casings in other areas.

[0065] Step 7: Implement small-diameter connecting drilling around the large-diameter drainage drilling location. The location is smaller than the distance to the large-diameter drainage drilling location. Meters, set a circle at 500 meters. The depth of the small-diameter connected drill hole connects all strata within the range of the height H of the coal mining water-conducting fracture zone, and all of them are equipped with permeable flower pipes. The height H of the coal mining water-conducting fracture zone is calculated using the following formula:

[0066] rice;

[0067] In the formula, m is the coal mining thickness, which is obtained through mining design.

[0068] Step 8: Use large-diameter drainage boreholes to continuously pump water at maximum capacity, and leave a coal pillar L = 20 meters in the large-diameter drainage boreholes. Then, conduct exploration and drainage of the sandstone aquifer before coal mining;

[0069] So take 20 meters

[0070] Finally, the water inflow from coal mining was within the controllable range of the mine drainage system and was maintained at 2000m 3 / d, achieving safe mining of coal resources.

Claims

1. A water-retaining coal mining method in a sandstone strong runoff area, characterized in that: The steps include: S1. Select the location of large-diameter drainage boreholes: Draw the natural gamma logging contour map by interpolation method, and select the location of large-diameter drainage boreholes within the minimum interval of the natural gamma logging contour map; S2. Determine the amount of water to be discharged in the sandstone strong runoff area ; S3. Determine the permeability coefficient of the area where the large-diameter drainage borehole is located. ; S4. Determine the maximum drainage capacity of a single large-diameter drainage borehole ; S5. Determine the number of large-diameter drainage boreholes and the final borehole diameter for pumping water; S6. Based on the location, number, and final diameter of the large-diameter drainage boreholes determined in S1 to S5, drill large-diameter drainage holes to 2 to 5 meters below the sandstone stratum floor. Leave permeable flower pipes in the sandstone stratum area and waterproof casings in other areas. S7, conducting small-diameter connecting drilling around the location of the large-diameter drainage drill hole, wherein the location around the large-diameter drainage drill hole is less than a set value R; S8. Use large-diameter drainage boreholes to continuously pump water at the maximum pumping capacity, and leave coal pillars in the large-diameter drainage boreholes. L , and conduct coal mining after exploring and draining the sandstone aquifer; The maximum drainage capacity of a single large-diameter drainage borehole in S4 Calculated using the following formula: ； in, is the permeability coefficient; is the thickness of the sandstone aquifer, obtained from the drill hole histogram; is the height of the hydraulic head of the sandstone aquifer from the bottom of the sandstone formation, obtained through hydrological observation; The method for determining the number of large-diameter drainage boreholes and the final hole diameter for pumping water in S5 is as follows: when f≤1, the number of large-diameter drainage boreholes is 1, and the final hole diameter is ≥1000mm; when f>1, the number of large-diameter drainage boreholes is the integer of f value rounded up to one, and the final hole diameter is ≥1000mm; f is calculated according to the following formula: ； in, The amount of water that should be discharged for the sandstone strong runoff area; The maximum drainage capacity of a single large-diameter drainage borehole.

2. The water-retaining coal mining method in sandstone strong runoff area according to claim 1 is characterized in that: The minimum interval of the natural gamma ray logging curve contour map in S1 refers to the 20% area with the smallest natural gamma ray logging values ​​in all exploration boreholes in the coal mining area.

3. The water-retaining coal mining method in sandstone strong runoff area according to claim 1 is characterized in that: In S2, the water volume to be discharged from the sandstone strong runoff area is Calculated according to the following formula: ； in, It is the water inflow that has been mined in the sandstone strong runoff area, obtained through downhole observation; It is the area that has been mined in the sandstone strong runoff area, obtained from the coal mining design map; is the total area to be mined in the future sandstone strong runoff zone, obtained from the coal mining design map; is the average value of the natural gamma logging results in the mined area, obtained by drawing the natural gamma logging contour map; It is the average value of the natural gamma logging results in the future mining area, obtained by drawing the natural gamma logging contour map.

4. The water-retaining coal mining method in sandstone strong runoff area according to claim 1, characterized in that: The permeability coefficient of the area where the large-diameter drainage borehole in S3 is located The determination method is as follows: by collecting rock samples from the sandstone strong runoff area where the large-diameter drainage borehole is located, and making rock sample thin sections, the average particle size d of the sand is measured using IPP software, and the permeability coefficient is calculated using the following formula : ； in, is the average specific gravity of sand particles in sandstone, obtained through testing; is the reduction coefficient, ranging from 0.0001 to 0.001; is the specific gravity of water, taken as 1000 kg / m3; d is the average particle size of sand, obtained by thin section test; is the depth of the paleo-river water, generally ranging from 0.1 to 5 meters, obtained from the natural gamma ray logging contour map; is the natural gradient of the sandstone floor, which is calculated from the drill hole histogram.

5. The water-retaining coal mining method in sandstone strong runoff area according to claim 1 is characterized in that: The position around S7 is less than the set value R from the large-diameter drainage borehole. R is calculated according to the following formula: ； in, is the height of the hydraulic head of the sandstone aquifer from the bottom of the sandstone formation, obtained through hydrological observation; is the permeability coefficient; The depth of small-diameter connected drilling holes is connected to the height of the water-conducting fracture zone in coal mining. H All strata within the scope of the mining area are equipped with water-permeable flower pipes. The water-conducting fracture zone of the mining area is high. H Calculated using the following formula: ； in the formula is the mining thickness, obtained from the mining plan.

6. The water-retaining coal mining method in sandstone strong runoff area according to claim 1, characterized in that: The large-diameter drainage borehole in S8 is used to leave a coal pillar L The calculation is as follows: ； Where C is the safety factor, which ranges from 3 to 5; is the coal mining thickness, obtained from the mining design drawing; is the hydrostatic pressure, , is the water density, is the height of the water head of the sandstone aquifer from the bottom of the sandstone formation, obtained through hydrological observation; v is the groundwater flow velocity, , is the permeability coefficient; is the natural gradient of the sandstone floor, which is calculated from the drill hole histogram; It is the tensile strength of the coal body, obtained through sampling test.

Images