Water-preserved coal mining method for water level variation in cohesive soil coverage area

Abstract

The invention discloses a cohesive soil coverage area water level change water-preserved coal mining method, and relates to the technical field of coal mining, and the method comprises the following steps: obtaining the height of a water flowing fissure zone and the depth of a downward fissure for coal mining; all cohesive soil sections which are away from the water flowing fractured zone by the set height upwards are determined, soil body sections occupied by all the cohesive soil sections serve as water level change sections, and the thickness of the water level change sections is determined; calculating the maximum allowable consolidation degree of the target coal mining area; calculating water level fluctuation half-cycle time according to the maximum allowable consolidation degree and the drainage mode; according to the water level fluctuation range of the water level change section and the permeability coefficient of the cohesive soil, the drill hole spacing is calculated; drill holes are formed in the coal mining working face of the target coal mining area according to the drill hole interval, a water-permeable floral tube is arranged on a water level change section, and drill conductors are arranged on other soil body sections; and water level fluctuation is carried out according to the water pumping and injecting device arranged in the drill hole and the water level fluctuation half-cycle time. The coal mining safety is improved while the implementation difficulty is reduced.

Description

Technical Field

[0001] The present application relates to the field of coal mining technology, and in particular to a method for water-preserving coal mining in a clay-covered area with fluctuating water levels. Background Art

[0002] There is thick clay soil above the coal seams in some coal fields. The clay soil will continue to release water under the additional stress of coal mining. These will enter the mining space, causing an increase in the amount of water inflow in the mine, a heavy burden on mine drainage, a waste of water resources and an impact on the ecological environment. Some mines even reach 1000m 3 / h, therefore, it is necessary to prevent and control the water released by this part of consolidation in advance. In order to prevent and control the water released by the consolidation of clay soil in coal mining, separation grouting is generally used to reduce additional stress, direct grouting reinforcement of the clay layer to reduce consolidation, and forced exploration and release of water for recycling. However, there are the following problems:

[0003] Delamination grouting requires geological conditions with large-scale delamination development. Some areas do not have such overburden structure, which has great limitations. In addition, the grouting project volume is large and the cycle runs through the entire coal mining process.

[0004] Grouting in clay soil is quite difficult, as the pores in clay soil are relatively small. The amount of grouting in a single borehole is very limited, making large-scale grouting difficult and technical implementation difficult.

[0005] Draining water from clay soil is a technical challenge. Clay soil releases water slowly, which results in limited water release. However, techniques such as blasting to increase permeability may cause the aquifer above the clay soil to enter the mining space, posing certain safety risks. Summary of the Invention

[0006] The purpose of this application is to provide a method for water-preserving coal mining in areas covered by clay soil with fluctuating water levels, which reduces the difficulty of implementation and improves coal mining safety.

[0007] To achieve the above objectives, this application provides the following solutions:

[0008] The present application provides a method for coal mining in a clay soil covered area with water level fluctuations, comprising:

[0009] Obtaining the height of the water-conducting fracture zone and the depth of the descending fracture for coal mining in the target mining area;

[0010] Determine all clay segments above the set height of the water-conducting fracture zone, use the soil segment occupied by all the clay segments as the water level fluctuation segment, and determine the thickness of the water level fluctuation segment;

[0011] Determining a drainage method for the water level fluctuation section according to whether the water level fluctuation section is within the depth of the downward fissure; the drainage method includes double-sided drainage and single-sided drainage;

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

[0013] Calculating a water level fluctuation half-cycle time according to the maximum allowable consolidation degree and the drainage method;

[0014] Calculating the drilling spacing based on the water level fluctuation range of the water level fluctuation section and the permeability coefficient of the clay soil;

[0015] Arranging drill holes on the coal mining working face of the target coal mining area according to the drill hole spacing, installing water-permeable flower pipes in the water level fluctuation section, and installing waterproof casings in the soil section of the target coal mining area except the water level fluctuation section;

[0016] A water pumping and water injection device is provided in the borehole, and the water level is fluctuated according to the water level fluctuation half cycle time according to the water pumping and water injection device.

[0017] Optionally, determining the drainage method of the water level fluctuation section according to whether the water level fluctuation section is within the downward fissure depth specifically includes:

[0018] If the water level fluctuation section is not within the depth of the downward fissure, the drainage method of the water level fluctuation section is single-side drainage;

[0019] If the water level change section is within the depth of the downward fissure, the drainage method of the water level change section is double-sided drainage.

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

[0021] The calculation formula for the maximum allowable consolidation degree is:

[0022] Among them, U t is the maximum allowable consolidation degree, a is a constant, Q0 is 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 change section, and F is the area of ​​the coal mining face.

[0023] Optionally, calculating the water level fluctuation half-cycle time according to the maximum allowable consolidation degree and the drainage method specifically includes:

[0024] The calculation formula for the half-cycle time of water level fluctuation is:

[0025] Among them, t0 is the half-cycle 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, and b represents the drainage method, b=1 represents single-sided drainage, and b=2 represents double-sided drainage.

[0026] Optionally, the borehole spacing is calculated based on the water level fluctuation range of the water level fluctuation section and the permeability coefficient of the clay soil, specifically including:

[0027] The calculation formula for drilling spacing is:

[0028] Among them, R is the drilling distance, S W is the water level fluctuation range, and K is the permeability coefficient of clay soil.

[0029] Optionally, arranging drill holes on the coal mining working face of the target coal mining area according to the drill hole spacing specifically includes:

[0030] The drilling depth reaches within 10 meters above the water-conducting fracture zone.

[0031] Optionally, a water level monitoring device is further provided in the borehole, and the water level monitoring device is used to detect the water level in the borehole.

[0032] Optionally, the water pumping and injection devices, 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 level fluctuation half-cycle time according to the water pumping and water injection device, specifically including:

[0034] The water level fluctuation ranges from 1 meter to 10 meters.

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

[0036] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0037] The present application provides a water-preserving coal mining method in a clay-covered area with fluctuating water levels. Drill holes are arranged on the coal mining working face of the target coal mining area according to the drilling hole spacing, permeable flower pipes are set in the water level fluctuation section, and pumping and injection devices are set in the drill holes. The water level is fluctuated according to the pumping and injection devices according to the half-cycle time of the water level fluctuation. Only human intervention is required for the water level, which is simple and easy to implement. High-frequency water level fluctuations according to the half-cycle time of the water level fluctuation can control the amount of water released from the clay, effectively protecting precious water resources, and having better ecological and environmental protection. There is no need to directly disturb the soil itself, which affects the water body, reduces the real-time difficulty, and at the same time avoids the aquifer above the clay from entering the mining space, thereby improving coal mining safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0039] Figure 1 A flow chart of a method for water-preserving coal mining in a clay-covered area with fluctuating water levels is provided in one embodiment of the present application. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0041] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0042] In an exemplary embodiment, the present application provides a method for coal mining in a clay soil covered area with water level fluctuation, such as Figure 1 As shown, the method for water-preserving coal mining in the clay soil covered area with water level fluctuation includes:

[0043] Step 101: Obtain the height of the water-conducting fracture zone and the depth of the downward fracture for coal mining in the target coal mining area.

[0044] Step 102: Determine all clay segments above a set height from the water-conducting fracture zone, use the soil segment occupied by all clay segments as a water level fluctuation segment, and determine the thickness of the water level fluctuation segment.

[0045] Step 103: Determine the drainage method of the water level fluctuation section according to whether the water level fluctuation section is within the downward fissure depth; the drainage method includes double-side drainage and single-side drainage.

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

[0047] Step 105: Calculate the water level fluctuation half-cycle time according to the maximum allowable consolidation degree and the drainage method.

[0048] Step 106: Calculate the drilling spacing based on the water level fluctuation range of the water level fluctuation section and the permeability coefficient of the clay soil.

[0049] Step 107: Arrange drill holes on the coal mining working face in the target coal mining area according to the drill hole spacing, set permeable flower pipes in the water level fluctuation section, and set waterproof casings in the soil section of the target coal mining area except the water level fluctuation section.

[0050] The permeable flower pipe and the waterproof casing are both sleeved in the borehole wall.

[0051] Step 108: a water pumping and water injection device is set in the borehole, and the water level is fluctuated according to the water level fluctuation half cycle time according to the water pumping and water injection device.

[0052] In an exemplary embodiment, the height set in step 102 is 20 meters. All clay segments above 20 meters in the water-conducting fracture zone are recorded, and the thickness of the water level change segment is recorded as H.

[0053] Step 103 specifically includes: if the water level change section is not within the downward crack depth, the drainage method of the water level change section is single-side drainage; if the water level change section is within the downward crack depth, the drainage method of the water level change section is double-side drainage.

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

[0055] Among them, U t is the maximum allowable consolidation degree, a is a constant, a represents the allowable increase coefficient of water inflow of coal mining face, a is 0.1-0.5, Q0 is the preset normal water inflow of coal mining face, obtained by analogy method; t is the mining time of coal mining face, obtained by mining design; S is the consolidation amount of water level change section, obtained by test, the test is to obtain the mining additional stress of this section of soil layer by numerical simulation technology, obtain soil layer samples under the condition of mining additional stress, and use consolidation test to determine the final consolidation amount; F is the area of ​​coal mining face.

[0056] The water level fluctuation half-cycle time is calculated according to the maximum allowable consolidation degree and the drainage method, specifically including: the calculation formula of the water level fluctuation half-cycle time is:

[0057] Among them, t0 is the half-cycle 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, obtained through geotechnical experiments; b represents the drainage method, b = 1 represents single-sided drainage, and b = 2 represents double-sided drainage.

[0058] The borehole spacing is calculated based on the water level fluctuation range of the water level fluctuation section and the permeability coefficient of the clay soil, specifically including: the calculation formula of the borehole spacing is:

[0059] Among them, R is the drilling distance, S W is the water level fluctuation range, and K is the permeability coefficient of clay soil.

[0060] Arranging drill holes on the coal mining working face of the target coal mining area according to the drill hole spacing specifically includes: the drilling depth reaches within 10 meters above the water-conducting fracture zone.

[0061] A water level monitoring device is also provided in the borehole, and the water level monitoring device is used to detect the water level in the borehole.

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

[0063] The water level is fluctuated according to the water level fluctuation half-cycle time using the pumping and injection devices, specifically including: the amplitude of the water level fluctuation is 1 meter to 10 meters, that is, the water level rises or falls by 1 to 10 meters within the water level time t0 of each water level fluctuation half-cycle.

[0064] This application mainly adopts the following principles: under the influence of high-frequency water level fluctuations, clay soil undergoes frequent cycles of water level rise (increase in pore water pressure) and fall (increase in effective stress). Since clay soil drains slowly, the water level begins to rise again before the pore water is fully discharged after the water level drops, causing some of the discharged water to be reabsorbed into the soil. In the repeated "drainage-water absorption" cycle, the amount of water discharged each time is partially offset by the subsequent water absorption, and the net drainage volume is significantly reduced. The determination of the half-cycle time of water level fluctuation is determined by the drainage time t0, so this application applies Terzaghi's one-dimensional consolidation theory, calculates the drainage time t0, and the expected consolidation degree U t Determines t0, so this application applies the principle of the increment of mine water inflow by consolidation-released water, and constructs the relationship between the relevant factors of coal mining and the half-cycle time of water level fluctuation.

[0065] Compared with the existing technology, the beneficial effects of this application are: 1) it does not require a large number of grouting projects, only manual intervention of the water level is required, which is simple and easy to implement; 2) high-frequency water level changes can control the amount of water released in clay soil, effectively protecting precious water resources and improving ecological and environmental protection; 3) this technology does not require specific geological conditions and has better applicability; 4) it does not directly disturb the soil itself and has no impact on the water body, so the technical implementation is relatively easy.

[0066] In an exemplary embodiment, when a coal mine is mining coal, a certain thickness of clay (loess) is overlying the coal seam. This produces a significant consolidation and water release of the loess layer, resulting in a significant abnormal increase in the amount of water inflow from the working face during coal mining. The amount of water inflow from the mine continues to increase, of which the consolidation and water release of the loess layer has exceeded 50% and continues to increase. It is urgent to control the water release of the loess layer. Using the traditional grouting method, it is found that the permeability of the loess layer is low, the grouting efficiency is low, the cost is high, and the effect is average. In order to eradicate this problem, a water-saving coal mining method for water level change in the clay-covered area of ​​the present application is adopted, and the specific implementation is as follows:

[0067] Step 1: Determine the height of the water-conducting fracture zone: The height of the water-conducting fracture zone in coal mining was determined to be 124 meters using the flushing fluid consumption method.

[0068] Step 2: Determine the depth of the downward fracture zone: Using physical similarity simulation technology, it was determined that the depth of the downward fracture zone in coal mining reached 8.5 meters.

[0069] Step 3: Select the water level fluctuation section: all clay sections above 20 meters from the water-conducting fracture zone determined in step 1, and record the thickness of the water level fluctuation section as H = 8 meters.

[0070] Step 4: Determine whether double-sided drainage is used. If the water level change section determined in step 3 is not within the range of the crack depth determined in step 2, it is single-sided drainage.

[0071] Step 5: Calculate the maximum allowable consolidation degree U t , calculated using the following formula:

[0072] In the formula, a is the coefficient of increase in water inflow allowed at the coal mining face, which is 0.3; Q0 = 1200m 3 / d is the normal water inflow of the coal mining face, obtained by the known analogy method; t = 244d is the mining time of the coal mining face, obtained through mining design; S = 0.8m is the final consolidation amount of the water level fluctuation section determined in step 3, obtained through experiments. The experiments are to obtain the additional mining stress of 0.1MPa in this section of soil layer through known numerical simulation technology, and to obtain soil layer samples under the obtained mining additional stress conditions and use consolidation tests to determine the final consolidation amount S; F = 420000m 2 It is the area of ​​the coal mining face, obtained through mining design.

[0073] Step 6: Calculate the water level fluctuation half-cycle time t0 using the following formula:

[0074]

[0075] U in the formula t=0.26 is the degree of consolidation, obtained through step 5; H = 8 meters is the thickness of the fluctuation section, obtained through step 3; C = 0.22m 2 / d is the consolidation coefficient, obtained through geotechnical experiments; b=1 is the double-sided drainage coefficient, which is 1 for one side and is determined through step 4.

[0076] Step 7: Determine the drilling spacing R and use the following formula to calculate:

[0077]

[0078] In the formula, S w =8 meters is the water level fluctuation range, which is taken as 8 meters; K = 0.08m / d is the permeability coefficient of clay soil, which is obtained through geotechnical experiments.

[0079] Step 8: Arrange boreholes on the coal face at the same spacing as in Step 7, reaching a depth of 10 meters above the water-conducting fracture zone. A permeable spherical pipe is placed in the section of the borehole where the water level fluctuates, as determined in Step 3. The remaining sections are waterproof casings.

[0080] Step 9: Set up pumping and injection equipment and water level monitoring equipment in the borehole of step 8. The power supply is new energy such as solar energy or wind energy. The water level fluctuation is carried out according to the water level fluctuation half period t0 = 15 days (rounded off) determined in step 6. The calculation method determines the fixed flow rate Q = 6m 3 / h, the water level fluctuation amplitude is 8 meters, that is, the water level rises or falls by 8 meters in each half cycle of fluctuation t0=15 days.

[0081] After adopting the technology of this project, the water inflow of a single working face decreased by 24%. With a small amount of engineering application, coal mining was effectively protected while protecting water resources.

[0082] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0083] This document uses specific examples to illustrate the principles and implementation methods of this application. The description of the above examples is only intended to help understand the method and core concept of this application. At the same time, for those skilled in the art, based on the concept of this application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A method for water-retaining coal mining in a clay soil covered area with water level fluctuation, characterized in that: The method for water-preserving coal mining in a clay soil covered area with water level fluctuations comprises: Obtaining the height of the water-conducting fracture zone and the depth of the descending fracture for coal mining in the target mining area; Determine all clay segments above the set height of the water-conducting fracture zone, use the soil segment occupied by all the clay segments as the water level fluctuation segment, and determine the thickness of the water level fluctuation segment; Determining a drainage method for the water level fluctuation section according to whether the water level fluctuation section is within the depth of the downward fissure; the drainage method includes double-sided drainage and single-sided drainage; Calculating a maximum allowable degree of consolidation in the target coal mining area; Calculating a water level fluctuation half-cycle time according to the maximum allowable consolidation degree and the drainage method; Calculating the drilling spacing based on the water level fluctuation range of the water level fluctuation section and the permeability coefficient of the clay soil; Arranging drill holes on the coal mining working face of the target coal mining area according to the drill hole spacing, installing water-permeable flower pipes in the water level fluctuation section, and installing waterproof casings in the soil section of the target coal mining area except the water level fluctuation section; A water pumping and water injection device is provided in the borehole, and the water level is fluctuated according to the water level fluctuation half cycle time according to the water pumping and water injection device.

2. The method for water-retaining coal mining in clay soil covered areas according to claim 1, characterized in that: Determining the drainage method of the water level fluctuation section according to whether the water level fluctuation section is within the downward fissure depth includes: If the water level fluctuation section is not within the depth of the downward fissure, the drainage method of the water level fluctuation section is single-side drainage; If the water level change section is within the depth of the downward fissure, the drainage method of the water level change section is double-sided drainage.

3. The method for coal mining in clay soil covered areas with water level fluctuation according to claim 1, characterized in that: Calculating the maximum allowable degree of consolidation in the target mining area, specifically including: The calculation formula for the maximum allowable consolidation degree is: Among them, U t is the maximum allowable consolidation degree, a is a constant, Q0 is 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 change section, and F is the area of ​​the coal mining face.

4. The method for water-retaining coal mining in clay soil covered areas according to claim 1, characterized in that: Calculating the water level fluctuation half-cycle time according to the maximum allowable consolidation degree and the drainage method specifically includes: The calculation formula for the half-cycle time of water level fluctuation is: Among them, t0 is the half-cycle 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, and b represents the drainage method, b=1 represents single-sided drainage, and b=2 represents double-sided drainage.

5. The method for water-retaining coal mining in clay soil covered areas according to claim 1, characterized in that: The borehole spacing is calculated based on the water level fluctuation range of the water level fluctuation section and the permeability coefficient of the clay soil, specifically including: The calculation formula for drilling spacing is: Among them, R is the drilling distance, S W is the water level fluctuation range, and K is the permeability coefficient of clay soil.

6. The method for coal mining in clay soil covered areas with water level fluctuation according to claim 1, characterized in that: Arranging drill holes on the coal mining face in the target coal mining area according to the drill hole spacing specifically includes: The drilling depth reaches within 10 meters above the water-conducting fracture zone.

7. The method for coal mining in clay soil covered areas with water level fluctuation according to claim 1, characterized in that: A water level monitoring device is also provided in the borehole, and the water level monitoring device is used to detect the water level in the borehole.

8. The method for water-retaining coal mining in clay soil covered areas according to claim 7, characterized in that: The water pumping and injection devices, as well as the water level monitoring device, are powered by solar energy or wind energy.

9. The method for water-retaining coal mining in clay soil covered areas according to claim 1, characterized in that: The water level fluctuation is performed according to the water level fluctuation half-cycle time according to the pumping and injection devices, specifically including: The water level fluctuation ranges from 1 meter to 10 meters.

10. The method for water-retaining coal mining in clay soil covered areas according to claim 1, characterized in that: The set height is 20 meters.

Images