Water conservation mining method for clay-covered area with water level variation

Abstract

The application discloses a water level change water conservation mining method in clay covering area, and relates to the technical field of coal mining. The method comprises the following steps: obtaining the water flowing fractured zone height and the downward fracture depth during coal mining; determining all clay sections above the set height of the water flowing fractured zone, taking all clay sections as water level change sections, and determining the water level change section thickness; calculating the maximum allowable consolidation degree of a target coal mining area; calculating the water level fluctuation half-period time according to the maximum allowable consolidation degree and the drainage mode; calculating the drilling spacing according to the water level fluctuation range of the water level change section and the permeability coefficient of the clay; arranging the drilling holes on the coal mining face of the target coal mining area according to the drilling spacing, arranging the water permeable flower pipe in the water level change section, and arranging the water isolation casing pipe in the remaining soil section; and fluctuating the water level according to the water pumping and water injection devices arranged in the drilling holes and the water level fluctuation half-period time. The application reduces the implementation difficulty and improves the coal mining safety.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coal mining, in particular to a water level change water conservation mining method in clay covering area. BACKGROUND

[0002] Some coal fields have thick clay above the coal seam. The clay will continuously release water under the additional stress of coal mining, which will enter the mining space and cause the mine water inflow to increase, the mine drainage burden to be heavy, the waste of water resources and the impact on the ecological environment. Some mines even reach 1000m 3 / h. Therefore, the part of the consolidated water needs to be prevented in advance. To prevent the clay consolidation water release in coal mining, off-layer grouting is generally used to reduce the additional stress, clay layer direct grouting is used to consolidate and reduce the consolidation, and forced water exploration is used for recycling, but there are the following problems:

[0003] Off-layer grouting needs large-scale off-layer development geological conditions. Some areas do not have such overburden structure, which has greater limitations, and the grouting engineering quantity is large and the cycle runs through the whole coal mining process.

[0004] Clay grouting is difficult, which is limited by the small clay pore and the limited grouting amount of a single borehole, which is difficult to grout in a large area and has great technical implementation difficulty.

[0005] Exploring water in clay is a technical problem. Since the clay releases water slowly, the water discharge amount is limited, and the blasting permeability technology may cause the water-bearing layer above the clay to enter the mining space, which has certain safety risk. SUMMARY

[0006] The purpose of the present application is to provide a water level change water conservation mining method in clay covering area, which reduces the implementation difficulty and improves the coal mining safety.

[0007] To achieve the above purpose, the present application provides the following solutions:

[0008] The present application provides a water level change water conservation mining method in clay covering area, comprising:

[0009] Obtaining the water diversion fractured zone height and the downward fracture depth of the target coal mining area for coal mining;

[0010] Determining all clay sections above the set height of the water diversion fractured zone, taking the clay sections as water level change sections, and determining the water level change section thickness;

[0011] According to whether the water level change section is within the downward fracture depth, determining the drainage mode of the water level change section; the drainage mode includes double-sided drainage and single-sided drainage;

[0012] calculating a maximum allowable consolidation degree of the target coal mining area;

[0013] calculating a water level fluctuation half-period time according to the maximum allowable consolidation degree and the drainage mode;

[0014] calculating a drilling interval according to a water level fluctuation range of the water level fluctuation section and a permeability coefficient of the clay;

[0015] arranging a drilling hole on a coal mining face of the target coal mining area according to the drilling interval, arranging a water permeable flower pipe at the water level fluctuation section, and arranging a water isolation casing at a soil section of the target coal mining area other than the water level fluctuation section;

[0016] arranging a water pumping and injecting device in the drilling hole, and performing water level fluctuation according to the water pumping and injecting device and the water level fluctuation half-period time.

[0017] Optionally, the drainage mode of the water level fluctuation section is determined according to whether the water level fluctuation section is within the downgoing fracture depth, and specifically includes:

[0018] if the water level fluctuation section is not within the downgoing fracture depth, the drainage mode of the water level fluctuation section is single-side drainage;

[0019] if the water level fluctuation section is within the downgoing fracture depth, the drainage mode of the water level fluctuation section is double-side drainage.

[0020] Optionally, the maximum allowable consolidation degree of the target coal mining area is calculated, and specifically includes:

[0021] a calculation formula of the maximum allowable consolidation degree is:

[0022] wherein, U t is the maximum allowable consolidation degree, a is a constant, Q0 is a preset normal water inflow of the coal mining face, t is a mining time of the coal mining face, S is a consolidation amount of the water level fluctuation section, and F is an area of the coal mining face.

[0023] Optionally, the water level fluctuation half-period time is calculated according to the maximum allowable consolidation degree and the drainage mode, and specifically includes:

[0024] a calculation formula of the water level fluctuation half-period time is:

[0025] wherein, t0 is the water level fluctuation half-period time, U t is the maximum allowable consolidation degree, H is a thickness of the water level fluctuation section, C is a consolidation coefficient, b represents the drainage mode, b=1 represents single-side drainage, and b=2 represents double-side drainage.

[0026] Optionally, the drilling hole spacing is calculated according to the water level fluctuation range of the water level fluctuation section and the permeability coefficient of the clay, and specifically includes:

[0027] The calculation formula of the drilling hole spacing is:

[0028] wherein, R is the drilling hole spacing, S W is the water level fluctuation range, and K is the permeability coefficient of the clay.

[0029] Optionally, the drilling holes are arranged on the coal mining face of the target coal mining area according to the drilling hole spacing, and specifically includes:

[0030] The drilling hole depth reaches within 10 meters of the water flowing fractured zone.

[0031] Optionally, the drilling hole is further provided with a water level monitoring device for detecting the water level in the drilling hole.

[0032] Optionally, the water pumping and water injection device and the water level monitoring device are powered by solar energy or wind energy.

[0033] Optionally, the water level fluctuation is performed according to the water pumping and water injection device according to the water level fluctuation half cycle time, and specifically includes:

[0034] The amplitude of the water level fluctuation is 1-10 meters.

[0035] Optionally, the set height is 20 meters.

[0036] According to the specific embodiments provided in the present application, the following technical effects are disclosed:

[0037] The present application provides a water level fluctuation water conservation mining method in clay covered area, drilling holes are arranged on the coal mining face of the target coal mining area according to the drilling hole spacing, water permeable flower pipes are arranged in the water level fluctuation section, water pumping and water injection devices are arranged in the drilling holes, and the water level fluctuation is performed according to the water pumping and water injection device according to the water level fluctuation half cycle time, only the water level needs to be artificially intervened, it is simple and easy to implement, the water release amount in the clay can be controlled according to the water level fluctuation half cycle time, the precious water resources are effectively protected, the ecological environmental protection is better, the soil itself does not need to be directly disturbed, the water body does not need to be intervened, the real-time difficulty is reduced, the water-bearing layer above the clay is avoided from entering the mining space, and the coal mining safety is improved. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings described below only illustrate some of the embodiments of the present application, and for those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0039] Figure 1 A flowchart of a water level change water conservation mining method in a clay covering area according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present application.

[0041] The above purposes, features and advantages of the present application will be more obvious, and the present application will be described in further detail below with reference to the drawings and specific embodiments.

[0042] In an exemplary embodiment, the present application provides a water level change water conservation mining method in a clay covering area, as shown in Figure 1 The water level change water conservation mining method in a clay covering area includes:

[0043] Step 101: obtaining a water diversion fractured zone height and a downward fracture depth for coal mining in a target mining area.

[0044] Step 102: determining all clay segments above a set height of the water diversion fractured zone, taking the clay segments as water level change segments, and determining a water level change segment thickness.

[0045] Step 103: determining a drainage mode of the water level change segment according to whether the water level change segment is within the downward fracture depth; the drainage mode includes double-sided drainage and single-sided drainage.

[0046] Step 104: calculating a maximum allowable consolidation degree of the target mining area.

[0047] Step 105: calculating a water level fluctuation half-period time according to the maximum allowable consolidation degree and the drainage mode.

[0048] Step 106: calculating a drilling spacing according to a water level fluctuation range of the water level change segment and a permeability coefficient of the clay.

[0049] Step 107: arranging drill holes on the mining face of the target mining area according to the drill hole spacing, arranging a water permeable flower pipe at the water level fluctuation section, and arranging a water isolation casing at the soil section of the target mining area except the water level fluctuation section.

[0050] The water permeable flower pipe and the water isolation casing are both arranged in the drill hole wall.

[0051] Step 108: arranging a water pumping and injecting device in the drill hole, and performing water level fluctuation according to the water pumping and injecting device and the water level fluctuation half cycle time.

[0052] In an exemplary embodiment, the set height in step 102 is 20 meters. All the cohesive soil sections above the 20-meter water conducting fracture zone are recorded as the water level fluctuation section, and the thickness of the water level fluctuation section is H.

[0053] Step 103 specifically includes: if the water level fluctuation section is not in the descending fracture depth, the drainage mode of the water level fluctuation section is single-side drainage; if the water level fluctuation section is in the descending fracture depth, the drainage mode of the water level fluctuation section is double-side drainage.

[0054] Calculating the maximum allowable consolidation degree of the target mining area specifically includes: the calculation formula of the maximum allowable consolidation degree is:

[0055] wherein, U t is the maximum allowable consolidation degree, a is a constant, a represents the allowable increase coefficient of the water inflow of the mining face, a is 0.1-0.5, Q0 is the preset normal water inflow of the mining face, which is obtained by analogy; t is the mining time of the mining face, which is obtained by mining design; S is the consolidation amount of the water level fluctuation section, which is obtained by experiment, the experiment is to obtain the mining additional stress of the soil layer by numerical simulation technology, and the final consolidation amount of the soil sample under the condition of obtaining the mining additional stress is obtained by consolidation test; F is the area of the mining face.

[0056] Calculating the water level fluctuation half cycle time according to the maximum allowable consolidation degree and the drainage mode specifically includes: the calculation formula of the water level fluctuation half cycle time is:

[0057] wherein, t0 is the water level fluctuation half cycle time, U t is the maximum allowable consolidation degree, H is the thickness of the water level fluctuation section; C is the consolidation coefficient, which is obtained by soil experiment; b represents the drainage mode, b=1 represents single-side drainage, and b=2 represents double-side drainage.

[0058] Calculating the drill hole spacing according to the water level fluctuation range of the water level fluctuation section and the permeability coefficient of the cohesive soil specifically includes: the calculation formula of the drill hole spacing is:

[0059] wherein R is the drilling spacing, S W is the water level fluctuation range, and K is the permeability coefficient of the clay.

[0060] The drilling spacing is used to arrange the drilling holes on the coal mining face of the target coal mining area, and specifically includes that the drilling depth reaches within 10 meters of the water flowing fractured zone.

[0061] The drilling hole is also provided with a water level monitoring device for detecting the water level in the drilling hole.

[0062] The water pumping and water injection device and the water level monitoring device are both powered by solar energy or wind energy.

[0063] The water pumping and water injection device is used to fluctuate the water level according to the water level fluctuation half-period time, and specifically includes that the water level fluctuation amplitude is 1-10 meters, i.e., the water level rises or falls by 1-10 meters within the water level t0 time of each water level fluctuation half-period.

[0064] The present application mainly uses the following principle: under the influence of high-frequency water level fluctuation, the clay experiences frequent water level rise (pore water pressure rise) and fall (effective stress increase) cycles. Because the drainage speed of the clay is slow, the water level begins to rise before the pore water is fully discharged, resulting in some of the discharged water being reabsorbed into the soil. In the repeated "drainage-water absorption" cycle, the amount of water discharged each time is offset by the subsequent water absorption, and the final net drainage amount is significantly reduced. The water level fluctuation half-period time is determined by the drainage time t0, so the present application applies the Terzaghi one-dimensional consolidation theory to calculate the drainage time t0, and the expected degree of consolidation U t determines t0, so the present application applies the principle that the increment of the consolidation release water to the mine water inflow, and constructs the relationship between the relevant factors of coal mining and the water level fluctuation half-period time.

[0065] Compared with the prior art, the present application has the following advantages: 1) no need for a large amount of grouting engineering, only need for artificial intervention of the water level, simple and easy to implement; 2) high-frequency water level fluctuation can control the water release amount in the clay, effectively protecting the precious water resources, and better ecological environmental protection; 3) the present technology does not require specific geological conditions, and has better applicability; 4) does not directly disturb the soil itself, and has less influence on the water body intervention, and has less technical implementation difficulty.

[0066] In one exemplary embodiment, when a certain coal mine is mining coal, there is a certain thickness of clay (loess) overlying the coal seam, which produces obvious loess layer consolidation and water release, resulting in a significant abnormal increase in water inflow at the working face during coal mining, and the mine water inflow continues to increase, wherein the loess layer consolidation and water release has exceeded 50% and continues to increase, and it is urgent to control the loess layer water release. Using the traditional grouting method, it is found that the loess layer has low permeability, low grouting efficiency, high cost and general effect, in order to eradicate this problem, a water level fluctuation water conservation mining method for clay covered area is adopted, and the specific implementation is as follows:

[0067] Step one: determine the height of the water flowing fractured zone: the flushing liquid consumption method is used to determine that the height of the water flowing fractured zone during coal mining reaches 124 meters.

[0068] Step two: determine the depth of the downward fracture zone: the physical similar simulation technology is used to determine that the downward fracture depth during coal mining reaches 8.5 meters.

[0069] Step three: select the water level fluctuation section: all the clay sections above 20 meters of the water flowing fractured zone determined in step one, and record the thickness of the water level fluctuation section as H=8 meters.

[0070] Step four: determine whether to drain on both sides, the water level fluctuation section determined in step three is not within the range of the downward fracture depth determined in step two, which is single side drainage.

[0071] Step five: calculate the maximum allowable consolidation degree U t , calculated by the following formula:

[0072] In the formula, a is the allowable increase coefficient of water inflow at the coal mining face, which is 0.3; Q0=1200m 3 / d is the normal water inflow at the coal mining face, which is obtained by using the known analogy method; t=244d is the mining time of the coal mining face, which is obtained by mining design; S=0.8 meters is the final consolidation amount of the water level fluctuation section determined in step three, which is obtained by experiment, and the experiment is to obtain the additional mining stress of 0.1 MPa of the soil layer in this section by using the known numerical simulation technology, and the final consolidation amount S of the soil sample is obtained by using the consolidation test under the condition of obtaining the additional mining stress; F=420000m 2 is the area of the coal mining face, which is obtained by mining design.

[0073] Step six: calculate the water level fluctuation half-period time t0, calculated by the following formula:

[0074]

[0075] In the formula, U t= 0.26 is the consolidation degree, obtained by step five; H = 8 meters is the fluctuation section thickness, obtained by step three; C = 0.22 m 2 / d is the consolidation coefficient, obtained by soil test; b = 1 is the double-side drainage coefficient, single-side is 1, determined by step four.

[0076] Step seven: determine the drilling spacing R, calculated by the following formula:

[0077]

[0078] In the formula, S w = 8 meters is the water level fluctuation range, 8 meters; K = 0.08 m / d is the permeability coefficient of clay, obtained by soil test.

[0079] Step eight: arrange the drilling holes on the coal mining face according to the spacing of step seven, the drilling depth reaches 10 meters above the water flowing fractured zone. The drilling hole is provided with a water permeable flower pipe in the water level fluctuation section determined by step three, and the rest is a water isolation casing.

[0080] Step nine: set up water pumping and water injection devices and water level monitoring devices in the drilling holes of step eight, the power is new energy such as solar energy or wind energy, the water level fluctuation is carried out according to the water level fluctuation half cycle t0=15 days (rounded down) determined by step six, the calculation method determines the constant flow Q = 6 m 3 / h of water pumping, and the water level fluctuation amplitude is 8 meters, that is, the water level rises or falls 8 meters in each water level fluctuation half cycle t0=15 days.

[0081] After adopting the technology of the project, the water inflow of a single working face is reduced by 24%, and the coal is effectively protected under a small amount of engineering application.

[0082] The technical features of the above embodiments can be combined arbitrarily, in order to make the description simple, not all possible combinations of the technical features in the above embodiments are described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the description.

[0083] In this paper, specific examples are used to describe the principles and implementation modes of the application, and the above embodiment is only used to help understand the method and its core idea of the application; at the same time, for those skilled in the art, according to the idea of the application, the specific implementation mode and application range will be changed. In view of the above, the content of the description should not be understood as a limitation of the application.

Claims

1. A water conservation coal mining method for water level variation in clay covering area, characterized in that, The water level variation water conservation mining method for the clay covering area comprises the following steps: obtaining the water flowing fractured zone height and the downward fracture depth for coal mining in a target mining area; determining all clay segments above a set height of the water flowing fractured zone, taking the clay segments as water level variation segments, and determining the thickness of the water level variation segments; determining the drainage mode of the water level variation segments according to whether the water level variation segments are within the downward fracture depth; the drainage mode comprises double-side drainage and single-side drainage; calculating the maximum allowable consolidation degree of the target mining area; calculating the water level fluctuation half-period time according to the maximum allowable consolidation degree and the drainage mode; calculating the drilling spacing according to the water level fluctuation range of the water level variation segments and the permeability coefficient of the clay; arranging drilling holes on the mining face of the target mining area according to the drilling spacing, arranging water permeable flower pipes in the water level variation segments, and arranging water-proof casings in the clay segments other than the water level variation segments in the target mining area; arranging water pumping and injection devices in the drilling holes, and fluctuating the water level according to the water pumping and injection devices and the water level fluctuation half-period time.

2. The water conservation coal mining method for water level fluctuation in clay covering area according to claim 1, characterized in that, The drainage mode of the water level variation segments is determined according to whether the water level variation segments are within the downward fracture depth, and specifically comprises the following steps: if the water level variation segments are not within the downward fracture depth, the drainage mode of the water level variation segments is single-side drainage; if the water level variation segments are within the downward fracture depth, the drainage mode of the water level variation segments is double-side drainage.

3. The water conservation coal mining method for water level fluctuation in clay covering area according to claim 1, characterized in that, The maximum allowable consolidation degree of the target mining area is calculated, and specifically comprises the following steps: The calculation formula of the maximum allowable consolidation degree is: wherein U t is the maximum allowable consolidation degree, a is a constant, Q0is the preset normal water inflow of the coal mining face; t is the mining time of the coal mining face, S is the consolidation amount of the water level variation section, and F is the area of the coal mining face.

4. The water conservation coal mining method for water level variation in clay covering area according to claim 1, characterized in that, The water level fluctuation half-period time is calculated according to the maximum allowable consolidation degree and the drainage mode, and specifically comprises the following steps: The formula for calculating the half-period time of water level fluctuation is: where t0 is the half-period time of water level fluctuation, U t is the maximum allowable consolidation degree, H is the thickness of the water level fluctuation section, C is the consolidation coefficient, b represents the drainage mode, b = 1 represents single-side drainage, and b = 2 represents double-side drainage.

5. The water conservation coal mining method for water level fluctuation in clay covering area according to claim 1, characterized in that, The drilling spacing is calculated according to the water level fluctuation range of the water level variation segments and the permeability coefficient of the clay, and specifically comprises the following steps: The formula for calculating the drilling spacing is: where R is the drill hole spacing, S W is the water level fluctuation range, and K is the permeability coefficient of the clayey soil.

6. The water conservation coal mining method for water level variation in clay covering area according to claim 1, characterized in that, The drilling holes are arranged on the mining face of the target mining area according to the drilling spacing, and specifically comprises the following steps: The drilling depth reaches within 10 meters above the water flowing fractured zone.

7. The water conservation coal mining method for water level fluctuation in clay covering area according to claim 1, characterized in that, The water level monitoring devices are arranged in the drilling holes, and the water level monitoring devices are used to detect the water level in the drilling holes.

8. The water conservation coal mining method for water level variation in clay covering area according to claim 7, characterized in that, The water pumping and injection devices and the water level monitoring devices are powered by solar energy or wind energy.

9. The water conservation coal mining method for water level fluctuation in clay covering area according to claim 1, characterized in that, The water level is fluctuated according to the water pumping and injection devices and the water level fluctuation half-period time, and specifically comprises the following steps: The amplitude of the water level fluctuation is 1 meter to 10 meters.

10. The water conservation coal mining method for water level variation in clay covering area according to claim 1, characterized in that, The set height is 20 meters.

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