Water-preserved coal mining method near unconsolidated aquifer

Abstract

The invention discloses a near-loose aquifer water-preserved coal mining method. The method comprises the steps that S1, the position of a working face and coordinates of a ground area are determined; s2, determining overlying strata structure characteristics of the mining working face and the positions of all aquifers through hydrogeological exploration; s3, the height H1 of the working face mining water flowing fractured zone is calculated; s4, the thickness delta H needing water pumping and draining treatment is determined; s5, ground drainage drill holes are arranged, and water is pumped out of a bottom water-bearing stratum of the S6, ground recharge well arrangement and middle aquifer recharge are conducted, and the double functions of protecting water resources of the loose aquifer and liberating coal resources near the loose aquifer are achieved; underground water resources are prevented from being damaged, and water resources are effectively protected and reasonably utilized.

Description

Technical Field

[0001] The invention relates to the technical field of water-preserving coal mining, and in particular to a water-preserving coal mining method near a loose aquifer. Background Art

[0002] Energy is the primary bottleneck problem that needs to be solved for my country's sustainable development. Coal occupies a dominant position in my country's primary energy structure, currently accounting for 68.8% of total energy consumption, and is expected to still account for about 60% in 2020. This pattern will not change substantially in the first half of the 21st century. The hydrogeological conditions of most coalfields in my country are relatively complex, and the mining process of their coal seams will be threatened by a variety of water bodies. The problem of mine water prevention and control is a technical problem in coal mine safety production and scientific research. With the development of coal mining in my country, the problem of "three under" (under buildings, under roads, and under water bodies) coal compression has become increasingly prominent, among which coal compression under water bodies accounts for about 25% of the total "three under" coal compression. According to preliminary statistics, the mines threatened by water hazards account for 48% of the key coal mines in the country, and the recoverable reserves threatened by water hazards are as high as 250×108t. Judging from the production and mining situation in recent years, the annual output of coal threatened by water hazards accounts for 10% of the total reserves. In order to prevent water damage to the aquifer above the coal seam, a large number of water-retaining coal pillars need to be left in traditional coal mining to protect the aquiclude from being destroyed, thereby ensuring safe production of the working face. In this way, a large amount of coal resources are left underground and cannot be recovered, especially high-quality coal resources, resulting in a huge waste of coal resources. In my country, there are as many as 5 billion tons of loose layer waterproof coal rock pillars left in East China and North China alone. The relief of energy tension and the maximum increase in the recovery rate of coal resources have become urgent tasks for the current coal industry. Therefore, raising the upper limit of coal mining and mining coal under the water body, under the building and under the railway at the upper mining level of the mine are of great significance to promoting coal production efficiency, improving the recovery rate of coal resources and alleviating energy tension.

[0003] At present, water-saving coal mining practices are mostly carried out through the construction of reservoirs in goaf areas, adjustment of coal mining methods, and grouting of the top of water-conducting fracture zones. The first method is a passive treatment method after the destruction of the overburden aquifer and the loss of groundwater, and it is impossible to achieve in-situ protection of the aquifer; adjusting the coal mining method often sacrifices a large amount of coal resources and does not meet the needs of my country's efficient development of coal resources; grouting of water-conducting fracture zones can easily cause a large amount of slurry to flow into the goaf, which is also a passive treatment method that causes damage and disturbance to the aquifer. In order to liberate the coal body near the loose aquifer, my country has recovered some water-saving coal pillars in many mining areas, but the scope of increasing the upper limit of water-saving coal pillar mining is limited, the recovery efficiency is low, and the risk of water damage is still high; on the other hand, a large amount of water resources are still lost in the water level of the loose aquifer in some mining areas.

[0004] Therefore, how to liberate the coal resources near the loose aquifers and at the same time prevent the destruction of groundwater resources to the greatest extent possible during coal mining, and effectively protect and rationally utilize water resources, is a major technical issue faced in my country's coal development process, and it is also a key scientific issue that needs to be solved to conserve water and liberate the coal resources near the loose aquifers. Summary of the invention

[0005] In order to solve the technical problems existing in the background technology, the present invention proposes a water-preserving coal mining method near a loose aquifer.

[0006] The present invention proposes a method for water-preserving coal mining in a near-loose aquifer, wherein the near-loose aquifer is directly located on the top surface of the bedrock of the coal-bearing stratum, the loose aquifer is the bottom aquifer of the loose layer, and there is no aquiclude between the near-loose aquifer and the bedrock of the coal-bearing stratum, and specifically comprises the following steps for water-preserving coal mining:

[0007] S1: Determine the working face position and ground area coordinates, including the working face strike length a and dip length b.

[0008] S2: Determine the structural characteristics of the overburden rock and the location of each aquifer at the mining face through hydrogeological exploration; among them, the protection distance between the bottom of the loose aquifer and the top of the coal seam is H.

[0009] S3: Calculate the height H1 of the water-conducting fracture zone in the working face;

[0010] According to the "Regulations on the Installation of Coal Pillars and Compressed Coal Mining in Buildings, Water Bodies, Railways and Main Shafts and Tunnels", the stratigraphic structure of the mining area, the physical and mechanical parameters of the stratigraphic layers and the thickness of the mined coal seam, the height H1 of the water-conducting fracture zone of the working face is calculated.

[0011] S4: Determine the thickness ΔH that needs to be drained by comparing the height H1 of the water-conducting fracture zone with the protection distance H.

[0012] S5: Arrangement of ground drainage drilling holes and pumping of water from the bottom aquifer of the loose layer. Horizontal directional drainage drilling holes are arranged outside the working surface with the ground area of ​​the working surface as the contour line to pump water from the loose aquifer (bottom aquifer).

[0013] S6: Arrangement of surface recharge wells and recharge of the middle aquifer. Recharge wells for the middle aquifer are arranged outside the working surface area to recharge the middle aquifer with water pumped from the loose aquifer (bottom aquifer).

[0014] Preferably, the calculation formula of ΔH in S4 is: ΔH=k×(H1-H), where k is a safety factor and has a value of 1.5-2.

[0015] Preferably, in step S5: taking the ground area of ​​the working face as the contour line, horizontal directional drainage boreholes are arranged at intervals of 50m and 10m outside the working face to pump water from the loose aquifer (bottom aquifer).

[0016] Preferably, in step S6: middle aquifer recharge wells are arranged at the axes of the four directions of the working face area, 100 m away from the surface boundary of the working face, to recharge the middle aquifer with pumped water from the loose aquifer (bottom aquifer).

[0017] In the present invention, a method for water-preserving coal mining near a loose aquifer is proposed. Through the method for water-preserving coal mining near a loose aquifer of the present invention, the aquifer at the bottom of the loose layer is pumped out for the working face where a waterproof safety coal pillar is required to be set up, and its water level is lowered to the water type corresponding to the water body mining level of the Class II water body. At the same time, the pumped water is replenished to the aquifer in the middle of the loose layer, which can achieve the dual effects of protecting the water resources of the loose aquifer and liberating the coal resources near the loose aquifer.

[0018] The use of this technical method can increase the upper limit of coal mine mining and mine coal in the "three under" areas such as under water bodies, under buildings and under railways at the upper mining level of the mine. It is of great significance to promote coal production efficiency, increase coal resource recovery rate and alleviate energy tension.

[0019] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a step diagram of the present invention;

[0021] Figure 2 It is the layout diagram of the drainage borehole and the recharging well of the present invention;

[0022] Explanation of the numbers in the figure: 1. Working face; 2. Drainage borehole; 3. Recharge well. DETAILED DESCRIPTION

[0023] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar symbols throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0024] like Figure 1-Figure 2A method for water-preserving coal mining in a near-loose aquifer is shown, wherein the near-loose aquifer is directly located on the top surface of the bedrock of the coal-bearing stratum, the loose aquifer is the bottom aquifer of the loose layer, and there is no aquiclude between the near-loose aquifer and the bedrock of the coal-bearing stratum, specifically comprising the following steps for water-preserving coal mining:

[0025] S1: Determine the position of working face 1 and the ground area coordinates, including the strike length a and dip length b of working face 1;

[0026] S2: Determine the structural characteristics of the overburden and the location of each aquifer at the mining face 1 through hydrogeological exploration; among them, the protection distance between the bottom of the loose aquifer and the top of the coal seam is H.

[0027] S3: Calculate the height H1 of the water-conducting fracture zone mined at working face 1;

[0028] According to the "Regulations on the Installation of Coal Pillars and Compressed Coal Mining in Buildings, Water Bodies, Railways and Main Shafts and Tunnels", the stratum structure of the mining area, the physical and mechanical parameters of the stratum and the thickness of the mined coal seam, the height H1 of the water-conducting fracture zone of working face 1 is calculated.

[0029] S4: Determine the thickness ΔH that needs to be drained by comparing the height H1 of the water-conducting fracture zone with the protection distance H.

[0030] In the formula ΔH=k×(H1-H), k is the safety factor, which ranges from 1.5 to 2.

[0031] S5: Arrangement of ground drainage boreholes 2 and pumping of water from the bottom aquifer of the loose layer. Take the ground area of ​​the working face 1 as the contour line and arrange ground horizontal directional drainage boreholes 2 at intervals of 50m 10m outside the working face 1 to pump water from the loose aquifer (bottom aquifer);

[0032] S6: Arrangement of ground recharge well 3 and recharge of middle aquifer. Recharge well 3 for middle aquifer is arranged at the axis of four directions of the working face 1 area, 100m away from the surface boundary of the working face 1, and the water of the loose aquifer (bottom aquifer) is pumped back into the middle aquifer.

[0033] Through the water-preserving coal mining method near the loose aquifer of the present invention, the loose layer bottom aquifer is pumped and drained for the working face 1 where a waterproof safety coal pillar is required, and its water level is drained to the water body type corresponding to the II-level water body mining level, and the pumped water is replenished to the aquifer in the middle of the loose layer, so as to achieve the dual effects of protecting the water resources of the loose aquifer and liberating the coal resources near the loose aquifer;

[0034] The use of this technical method can increase the upper limit of coal mine mining and mine coal in the "three under" areas such as under water bodies, under buildings and under railways at the upper mining level of the mine. It is of great significance to promote coal production efficiency, increase coal resource recovery rate and alleviate energy tension.

[0035] It should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0036] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0037] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0039] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for water-retaining coal mining near a loose aquifer, characterized in that: The near loose aquifer is directly located on the top surface of the bedrock of the coal-bearing stratum, the loose aquifer is the bottom aquifer of the loose layer, and there is no aquiclude between the near loose aquifer and the bedrock of the coal-bearing stratum. The water-saving coal mining steps are specifically as follows: S1: Determine the position of the working face (1) and the ground area coordinates, including the strike length a and the dip length b of the working face (1); S2: Determine the structural characteristics of the overburden and the location of each aquifer at the mining face (1) through hydrogeological exploration; the protection distance between the bottom of the loose aquifer and the top of the coal seam is H; S3: Calculate the height H1 of the water-conducting fracture zone mined at the working face (1); According to the "Regulations on the Retention and Compressed Coal Mining of Coal Pillars in Buildings, Water Bodies, Railways and Main Shafts and Lanes", the stratum structure of the mining area, the physical and mechanical parameters of the stratum and the thickness of the mined coal seam, calculate the height H1 of the water-conducting fracture zone of the working face (1); S4: Determine the thickness ΔH that needs to be drained by comparing the height H1 of the water-conducting fracture zone with the protection distance H; S5: Arrangement of ground drainage boreholes (2) and extraction of water from the bottom aquifer of the loose layer, with the ground area of ​​the working surface (1) as the contour line, arrange ground horizontal directional drainage boreholes (2) outside the working surface (1) to extract water from the loose aquifer (bottom aquifer); S6: Arrangement of surface recharge wells (3) and recharge of the middle aquifer. Recharge wells (3) for the middle aquifer are arranged outside the working surface (1) area to recharge the middle aquifer with water pumped from the loose aquifer (bottom aquifer).

2. A method for coal mining near loose aquifers according to claim 1, characterized in that: The calculation formula for ΔH in S4 is: ΔH=k×(H1-H), where k is the safety factor and takes a value of 1.5 to 2.

3. A method for water-retaining coal mining near a loose aquifer according to claim 1, characterized in that: In step S5: using the ground area of ​​the working face (1) as the contour line, horizontal directional drainage boreholes (2) are arranged at intervals of 50m and 10m outside the working face to pump water from the loose aquifer (bottom aquifer).

4. A method for water-retaining coal mining near a loose aquifer according to claim 1, characterized in that: In step S6: a middle aquifer recharge well (3) is arranged at the axes of the four directions of the working face (1) area, 100m away from the surface boundary of the working face (1), to recharge the middle aquifer with water pumped from the loose aquifer (bottom aquifer).

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