Liberated drainage depressurization mining method under soft sandstone aquifer

Abstract

The invention relates to the technical field of coal mining, and provides a liberated drainage depressurization mining method under a soft sandstone aquifer, which comprises the following steps: determining the risk level of the aquifer based on the basic information of the aquifer; based on the overlying strata structure type and the predicted overlying strata damage height, the size of each type of coal pillar is determined, and according to the distance between each coal seam and each water-bearing stratum, the type of the coal pillar between each coal seam and each water-bearing stratum is determined; determining a target coal seam and a first mining working face based on the aquifer risk level and the coal pillar type; and the coal seam mining thickness is controlled, so that mining cracks gradually affect the upper aquifer to drain and reduce the water content until target coal seam resources are liberated. Through the arrangement, coal resource mining and water disaster prevention and control can be considered, target coal seam determination of multiple short-distance coal seams and first mining working face determination in the target coal seam are researched from the angle of water disaster prevention and control, the technical problem of water disaster prevention and control of first mining of a mine is solved, and high economic benefits and safety benefits are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of coal mining, and particularly relates to a liberation type hydrophobic pressure relief mining method under a soft sandstone aquifer. Background Art

[0003] At present, for the close-distance multi-seam mining under water bodies, the coal seam thickness and mining economic benefits are still considered limitedly, and the overall coal resource mining plan is not clear, resulting in the inevitable damage or waste of coal resources during the close-distance multi-seam mining. There are also some designs starting from the perspective of coal resource recovery, with the first mining face designed in the shallow part and the area close to the overlying aquifer, resulting in a significant increase in the risk of roof water filling and sand bursting during the mining of the working face, and even the occurrence of accidents such as flooding of the face and shaft. Summary of the Invention

[0004] The present invention provides a liberation type hydrophobic pressure relief mining method under a soft sandstone aquifer to solve the problems of resource waste and potential safety hazards existing in the close-distance multi-seam mining under water bodies in the prior art, which can take into account both coal resource mining and water disaster prevention and control, and has strong economic and safety benefits.

[0005] The present invention provides a liberation type hydrophobic pressure relief mining method under a soft sandstone aquifer, including the following steps: Based on the basic information of the aquifer, determine the risk level of the aquifer; Based on the overlying rock structure type and the predicted overlying rock failure height, determine the sizes of various types of coal pillars, and according to the spacing between each coal seam and each aquifer, determine the coal pillar types between each coal seam and each aquifer; Based on the aquifer risk level and coal pillar type, determine the target coal seam and the first mining face; Control the coal seam mining thickness to make the mining-induced fractures gradually affect the upper aquifer to drain and reduce the water content until the resources of the target coal seam are liberated.

[0006] According to the liberation type hydrophobic pressure relief mining method under a soft sandstone aquifer provided by the present invention, the basic information of the aquifer includes the specific yield and permeability coefficient of the aquifer.

[0007] According to the liberation type hydrophobic pressure relief mining method under a soft sandstone aquifer provided by the present invention, the determination of the risk level of the aquifer includes: Based on the specific yield, determine the water richness of each aquifer; Based on the permeability coefficient, determine the recharge water richness of each aquifer; Based on the water richness and recharge water richness, divide the risk levels of each aquifer into low risk, medium risk and high risk.

[0008] A method for liberating hydrophobic pressure relief mining under a soft sandstone aquifer provided by the present invention, the prediction method for the height of overburden failure includes empirical formula analysis method, analogy method and numerical simulation method.

[0009] A method for liberating hydrophobic pressure relief mining under a soft sandstone aquifer provided by the present invention, the types of coal pillars include anti-collapse safety coal pillars, anti-sand safety coal pillars and waterproof safety coal pillars.

[0010] A method for liberating hydrophobic pressure relief mining under a soft sandstone aquifer provided by the present invention, based on the risk level of the aquifer and the type of coal pillar, determining the target coal seam and the first mining face, includes: Determining that when the risk level of the aquifer is weak risk and / or the type of coal pillar is waterproof safety coal pillar, it meets the mining conditions; Determining the coal seam that partially or fully meets the mining conditions as the target coal seam; Determining the area in the target coal seam that meets the mining conditions and is far from the aquifer as the first mining face.

[0011] A method for liberating hydrophobic pressure relief mining under a soft sandstone aquifer provided by the present invention, based on the risk level of the aquifer and the type of coal pillar, determining the target coal seam and the first mining face, further includes: When it is determined that the reserved size of the waterproof safety coal pillar cannot be met in all areas of the target coal seam, analyzing the water-richness of the aquifer in each area of the target coal seam; If the water-richness of a certain area is medium or above, pre-drainage is required to pre-drain the aquifer until the aquifer is unconfined.

[0012] A method for liberating hydrophobic pressure relief mining under a soft sandstone aquifer provided by the present invention, controlling the mining thickness of the coal seam to gradually make the mining-induced cracks reach the upper aquifer to reduce the water content until the resources of the target coal seam are liberated, includes: Based on the waterproof safety coal pillar, determining the lower limit of the restricted mining thickness , based on the anti-sand safety coal pillar, determining the upper limit of the restricted mining thickness ; After the working face advances a preset distance, gradually increase the mining thickness of the coal seam according to the layer spacing, so that the water-conducting fracture zone gradually reaches the upper aquifer, but the coal seam thickness is not greater than ; When the upper aquifer changes from weakly water-rich to basically water-free, coal resources can be mined according to the normal situation without water hazard threat; Gradually increase the mining face of the target coal seam until the resources of the target coal seam are liberated.

[0013] According to a method for liberating and dewatering and pressure-reducing mining under a soft sandstone aquifer provided by the present invention, the preset distance is 1 to 2 times the inclined length of the working face.

[0014] According to a method for liberating and dewatering and pressure-reducing mining under a soft sandstone aquifer provided by the present invention, the method further includes the following steps: Redetermine the target coal seam and the first mining working face, and carry out mining based on the redetermined target coal seam and the first mining working face.

[0015] According to a method for liberating and dewatering and pressure-reducing mining under a soft sandstone aquifer provided by the present invention, the redetermining the target coal seam and the first mining working face includes: Based on the influence range of the water-conducting fracture zone in coal seam mining, combined with the change of the water level of the aquifer, analyze the influence of coal seam mining on the overlying aquifer; Carry out ground hydrogeological supplementary exploration boreholes to test the water-richness of the overlying aquifer; Redetermine the risk level of the aquifer, and based on the aquifer risk level and the type of coal pillar, redetermine the target coal seam and the first mining working face.

[0016] The method for liberating and dewatering and pressure-reducing mining under a soft sandstone aquifer provided by the present invention can take into account both coal resource mining and water disaster prevention. From the perspective of water disaster prevention, it studies the determination of the target coal seam in close-distance multi-coal seams and the determination of the first mining working face in the target coal seam, solves the technical problem of water disaster prevention in the first mining of the mine, and compared with the traditional method that does not consider the distribution space of coal seams and aquifers, this method more systematically explains the idea of safe coal resource extraction, proposes a dewatering and pressure-reducing mining method that gradually liberates the coal resources of the same coal seam after the first mining working face is liberated, and then gradually liberates the coal resources of other coal seams, reduces resource waste and potential safety hazards, and has strong economic and safety benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0018] Figure 1 It is a flow chart of the method for liberating and dewatering and pressure-reducing mining under a soft sandstone aquifer provided by an embodiment of the present invention.

[0019] Figure 2 It is a schematic diagram of the spatial position relationship of multi-coal seam mining under multiple aquifers provided by an embodiment of the present invention.

[0020] Figure 3It is the schematic diagram of safety evaluation under the condition of matching coal pillar size and risk in the embodiments of the present invention.

[0021] Figure 4 It is the schematic diagram of the face layout provided by the embodiments of the present invention. Specific embodiments

[0022] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] To better understand the liberation-type hydrophobic pressure relief mining method under a soft sandstone aquifer provided by the embodiments of the present invention, its application background will be introduced first. During coal mining, it is necessary to pre-drain water from the sandstone aquifer with poor rock consolidation. However, there are differences in multiple coal seams and the distance from the overlying aquifer. How to effectively and reasonably select the first mining coal seam, pre-drain the aquifer and its water drainage requirements all require further research work.

[0024] Currently, for the close-distance multi-seam mining under water bodies, the coal seam thickness and mining economic benefits are still mainly considered, and the overall coal resource mining plan is not clear, resulting in the inevitable damage or waste of coal resources during the close-distance multi-seam mining process. There are also some designs starting from the perspective of coal resource recovery. The face layout mainly considers aspects such as mine pressure manifestation and mining and excavation connection management, without fully considering the influence of the overlying aquifer, nor considering the spatial position relationship between the coal seam and the overlying aquifer. The first mining face is designed in the shallow part and close to the overlying aquifer, resulting in a significant increase in the risk of roof water inrush and sand bursting during the face mining, and even the occurrence of face flooding and shaft flooding accidents.

[0025] In view of the above technical problems, the embodiments of the present invention provide a liberation-type hydrophobic pressure relief mining method under a soft sandstone aquifer, which can take into account both coal resource mining and water disaster prevention and control, reduce resource waste and potential safety hazards, and has strong economic and safety benefits.

[0026] The following combines Figures 1 - 4 to describe the liberation-type hydrophobic pressure relief mining method under a soft sandstone aquifer of the present invention.

[0027] Figure 1 It is the flow schematic diagram of the liberation-type hydrophobic pressure relief mining method under a soft sandstone aquifer provided by the embodiments of the present invention. As Figure 1 shown, the method includes the following steps: Step 10. Determine the risk level of the aquifer based on the basic information of the aquifer.

[0028] Specifically, the basic information of the aquifer includes the specific yield q and the permeability coefficient k of the aquifer. Among them, the specific yield q refers to the water yield when the water level in the well hole (caliber 91mm) drops by one meter during the pumping test, and it is an index used to measure the water production capacity of the aquifer. The unit of the specific yield is . The permeability coefficient k refers to the unit flow rate under the unit hydraulic gradient in an isotropic medium, which is used to measure the ease of fluid passing through the pore skeleton and is only related to the properties of the solid skeleton. The unit of the permeability coefficient is usually meters per second ( ), centimeters per second ( ), or meters per day and night ( ).

[0029] Specifically, Step 10 includes: Step 100. Determine the water richness of each aquifer based on the specific yield.

[0030] Taking the specific yield q as the evaluation criterion, the water richness of each aquifer is divided into three types: weak water richness (q ≤ 0.1 ), medium water richness (0.1 < q ≤ 1 ), and strong water richness (q > 1 ).

[0031] Step 101. Determine the recharge water richness of each aquifer based on the permeability coefficient k.

[0032] Taking the permeability coefficient k as the evaluation criterion, the recharge water richness of each aquifer is divided into three types: weak recharge water richness (1 < k ≤ 5 ), medium recharge water richness (5 < k ≤ 10 ), and strong recharge water richness (10 < k).

[0033] Step 102. Based on the water richness and recharge water richness, divide the risk levels of each aquifer into low risk, medium risk, and high risk. The specific division criteria are shown in Table 1.

[0034] Table 1 Division of water richness and recharge-discharge characteristics of different aquifers In Table 1, the risk levels of the aquifers for coal mine water hazard prevention and control are divided according to the increasing trend of three levels A, B, and C. Among them, A represents low risk, B represents medium risk, and C represents high risk.

[0035] Step 11: Determine the dimensions of each type of coal pillar based on the overburden structure type and the predicted overburden failure height, and determine the type of coal pillar between each coal seam and each aquifer according to the spacing between each coal seam and each aquifer.

[0036] Specifically, the methods for predicting the overburden failure height include empirical formula analysis method, analogy method, numerical simulation method, etc.

[0037] Among them, the empirical formula analysis method obtains the overburden type of the overlying strata by collecting historical data or conducting borehole coring, and combines with the empirical formula method in the "Guide for Coal Pillar Retention and Coal Mining under Buildings, Water Bodies, Railways and Main Roadways", and predicts the development height of the water-conducting fissure zone according to different calculation formulas for different overburden types.

[0038] The analogy method is to combine the measured data of the water-conducting fissure zone already carried out in this area and predict the development height of the water-conducting fissure zone according to similar conditions.

[0039] The numerical simulation method is a method that uses computer technology to simulate and predict physical phenomena. Using professional numerical simulation software (such as FLAC3D, ANSYS, ABAQUS, etc.), a specific geomechanical model is established to simulate the deformation and failure process of the overlying strata, so as to predict the development height of the water-conducting fissure zone.

[0040] It should be noted that the more specific content and specific steps of the above various prediction methods can refer to the prior art, and will not be elaborated in the embodiments of the present invention.

[0041] It can be understood that each of the above prediction methods has its own advantages and limitations, and can be flexibly selected according to the actual engineering background. In addition, in order to reduce the limitations of a single prediction method, multiple methods can be used in combination to improve the prediction accuracy, which is not specifically limited in the embodiments of the present invention.

[0042] Through the above prediction methods, the suitable predicted range of the overburden failure height can be determined, and then combined with the "Guide for Coal Pillar Retention and Coal Mining under Buildings, Water Bodies, Railways and Main Roadways", the dimensions of each type of coal pillar are predicted for different overburden structure types and overburden failure heights. Specifically, the types of coal pillars include anti-collapse safety coal pillars, anti-sand safety coal pillars, and anti-water safety coal pillars. Then, by comparing the spacing between each coal seam and each aquifer with the dimensions of each type of coal pillar, the type of coal pillar between each coal seam and each aquifer is determined.

[0043] For the convenience of understanding, in a specific example, referring to Figure 2 , it is assumed that there are two coal seams, namely coal seam 1 and coal seam 2 from bottom to top, and there are two overlying aquifers of the coal seam, namely aquifer 1 and aquifer 2 from bottom to top; then the spacing between coal seam 1 and aquifer 1 is , the distance between coal seam 1 and aquifer 2 is , the distance between coal seam 2 and aquifer 1 is , the distance between coal seam 2 and aquifer 2 is . Based on the type of overlying rock structure and the height of overlying rock failure, the predicted size of the anti-collapse safety coal pillar is , the size of the anti-sand safety coal pillar is , the size of the waterproof safety coal pillar is , and then , , and are respectively compared and analyzed with , and to determine whether the distance between the coal seam and the aquifer meets the reserved size of the waterproof safety coal pillar. If it meets, then water inrush threat is not likely to occur during the coal seam mining process, and the coal resources under the corresponding aquifer can be mined in full thickness, and this coal seam can be trial-mined in full thickness.

[0044] Step 12: Determine the target coal seam and the first mining face based on the aquifer risk level and the coal pillar type.

[0045] Specifically, step 12 includes: Step 120: Determine that the mining condition is met when the risk level of the aquifer is weak risk and / or the coal pillar type is the waterproof safety coal pillar. Specifically, as shown in Table 2 and Figure 3 shown, where Table 2 shows the water filling hazards of different aquifers, Figure 3 shows the safety evaluation under the condition of matching the coal pillar size and the risk.

[0046] Table 2 Water filling hazards of different aquifers In Table 2, Y indicates that the mining condition is met, and N indicates that the mining condition is not met. Step 121: Determine the coal seam that partially or fully meets the mining condition as the target coal seam.

[0047] For a certain coal seam, if the current coal seam partially or fully meets Y, then this coal seam can be used as the target coal seam for the first mining. If the current coal seam does not fully meet Y, then repeat the above steps 11 and 12 to judge whether other coal seams meet the judgment conditions of the target coal seam until the target coal seam that meets the conditions is determined.

[0048] Step 121: Determine the area that meets the mining condition and is far from the aquifer in the target coal seam as the first mining face.

[0049] Specifically, after determining the target coal seam, analyze the areas in the target coal seam that meet the mining conditions, and select the area in the target coal seam that meets the mining conditions and has a relatively large distance from the aquifer as the area where the first mining coal seam is located (as Figure 4 shown). When mining in this area, it is not easy to have the risk of water inrush and sand bursting, and the risk is the lowest.

[0050] In one embodiment of the present invention, step 12 further includes: Step 122: When it is determined that all areas of the target coal seam do not meet the reserved size of the waterproof safety coal pillar, analyze the water-richness of the aquifers in each area of the target coal seam.

[0051] Step 123: If it is determined that the water-richness of a certain area is medium or above, pre-drainage is required to pre-lower the aquifer until the aquifer is not under pressure.

[0052] Specifically, if all areas in the target coal seam do not meet the reserved size of the waterproof safety coal pillar, still select the area that meets the mining conditions and has a relatively large distance from the aquifer as the first mining area, and analyze the water-richness of the aquifers in the areas where the full thickness mining of the coal seam does not meet the reserved size of the waterproof safety coal pillar. If it is medium or above, underground water drainage measures need to be taken for the areas near the open-off cut to pre-lower the aquifer until the aquifer is not under pressure.

[0053] Step 13: Control the mining thickness of the coal seam so that the mining-induced fissures gradually affect the upper aquifer to lower the water content until the resources of the target coal seam are liberated.

[0054] Specifically, step 13 includes: Step 130: Based on the waterproof safety coal pillar, determine the lower limit of the restricted mining thickness , and based on the sand control safety coal pillar, determine the upper limit of the restricted mining thickness .

[0055] Step 131: After the working face advances a preset distance, gradually increase the mining thickness of the coal seam according to the layer spacing so that the water-conducting fissure zone gradually affects the upper aquifer, but the coal seam thickness is not greater than .

[0056] Step 132: When the overlying aquifer changes from weakly water-rich to basically water-free, coal resources can be mined according to the situation without water hazard threat.

[0057] Step 133: Gradually increase the mining face of the target coal seam until the resources of the target coal seam are liberated.

[0058] After the target coal seam and the first mining area are determined, mining work is carried out. By controlling the mining thickness of the coal seam, the mining fissures gradually spread to the upper aquifer to dewater the aquifer. As the mining range gradually increases, the water-richness of the overlying aquifer gradually weakens. The mining thickness of the coal seam is gradually increased, so that the dewatering funnel formed inside the goaf during coal seam mining gradually increases, thereby liberating more coal resources of the target coal seam. When the overlying aquifer changes from weakly water-rich to basically waterless, coal resources can be mined according to the normal situation without water hazard threat until the resources of the target coal seam are liberated.

[0059] Specifically, the above preset distance is 1 to 2 times the inclined length of the working face.

[0060] In an embodiment of the present invention, the method for liberating dewatering and pressure reduction mining under a soft sandstone aquifer further includes the following steps: Step 14. Re-determine the target coal seam and the first mining face, and carry out mining based on the re-determined target coal seam and the first mining face.

[0061] Specifically, step 14 includes: Step 140. Based on the influence range of the water-conducting fissure zone in coal seam mining, combined with the change of the aquifer water level, analyze the influence of coal seam mining on the overlying aquifer; Step 141. Re-determine the risk level of the aquifer, and based on the aquifer risk level and the type of coal pillar, re-determine the target coal seam and the first mining face.

[0062] During the current coal seam mining process, the roof water-conducting fissure zone will develop upward and affect the overlying aquifers. Based on the influence range of the water-conducting fissure zone in coal seam mining, combined with the change of the aquifer water level, analyze the influence of coal seam mining on the overlying aquifer, and carry out surface hydrogeological supplementary exploration boreholes to test the water-richness of the overlying aquifer. Then, through the above steps 10 to 12 for demonstration, analyze the feasibility of mining the liberated coal seam that is not significantly affected by mining, and determine the positions of the new target coal seam and the first mining face, and gradually mine the area outside the first mining face of the liberated coal seam until the remaining liberated coal resources are mined, and finally realize the safe mining of coal resources.

[0063] Through the method for liberating hydrophobic pressure relief mining under a soft sandstone aquifer provided by the embodiments of the present invention, it is possible to take into account both coal resource mining and water disaster prevention. From the perspective of water disaster prevention, the determination of target coal seams in closely spaced multi-seam coal beds and the determination of the first mining face in the target coal seams are studied, solving the technical problems of water disaster prevention in the initial mining of the mine. Compared with the traditional method that does not consider the distribution space of coal seams and aquifers, this method more systematically explains the idea of safe coal resource extraction, and proposes a hydrophobic pressure relief mining method in which, after the liberation of the first mining face, the coal resources in the same coal seam are gradually liberated, and then the coal resources in other coal seams are gradually liberated, reducing resource waste and potential safety hazards, and having strong economic and safety benefits.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for dewatering and reducing pressure in a soft sandstone aquifer, characterized in that: The following steps are involved: Determine the risk level of aquifers based on basic information of aquifers; Based on the overburden structure type and the expected overburden failure height, determine the size of each type of coal pillar, and determine the type of coal pillar between each coal seam and each aquifer according to the distance between each coal seam and each aquifer; Determine the target coal seam and first mining face based on the risk level of the aquifer and the type of coal pillar; Control the mining thickness of the coal seam so that the mining cracks gradually spread to the upper aquifer to reduce the water content until the target coal seam resources are released.

2. The method for dewatering and reducing pressure in a soft sandstone aquifer according to claim 1, characterized in that: The basic information of the aquifer includes the unit water yield and permeability coefficient of the aquifer.

3. The method for dewatering and reducing pressure in a soft sandstone aquifer according to claim 2, characterized in that: The determination of the risk level of an aquifer includes: Determine the water richness of each aquifer based on the specific water yield; Determine the recharge water abundance of each aquifer based on the permeability coefficient; The risk level of each aquifer is divided into weak risk, medium risk and high risk based on water richness and recharge richness.

4. The method for dewatering and reducing pressure in a soft sandstone aquifer according to claim 1, characterized in that: The methods for estimating the overburden failure height include empirical formula analysis, analogy and numerical simulation.

5. The method for dewatering and reducing pressure in a soft sandstone aquifer according to claim 3, characterized in that: The types of coal pillars include anti-collapse safety coal pillars, anti-sand safety coal pillars and waterproof safety coal pillars.

6. The method for dewatering and reducing pressure in a soft sandstone aquifer according to claim 5, characterized in that: Determining the target coal seam and the first mining working face based on the risk level of the aquifer and the type of coal pillar includes: The mining conditions are met when the risk level of the aquifer is determined to be weak risk and / or the type of the coal pillar is a waterproof safety coal pillar; Determine the coal seam that partially or completely meets the mining conditions as the target coal seam; Determine the area in the target coal seam that meets the mining conditions and is far away from the aquifer as the first mining working face.

7. The method for dewatering and reducing pressure in a soft sandstone aquifer according to claim 6, characterized in that: Determining the target coal seam and the first mining working face based on the risk level of the aquifer and the type of coal pillars also includes: When it is determined that all areas of the target coal seam do not meet the size of the waterproof safety coal pillar, the water-richness of the aquifers in each area of ​​the target coal seam is analyzed; If it is determined that the water-richness of a certain area is medium or above, it is necessary to conduct pre-drainage to lower the aquifer to a level where it is not under pressure.

8. The method for dewatering and reducing pressure in a soft sandstone aquifer according to claim 7, characterized in that: The control of coal seam mining thickness so that mining cracks gradually spread to the upper aquifer to reduce the water content until the target coal seam resources are released includes: Based on the waterproof safety coal pillar, determine the lower limit of mining thickness , based on the sand prevention safety coal pillar, determine the upper limit of the mining thickness ; After the working face advances a preset distance, the coal seam mining thickness is gradually increased according to the interlayer spacing, so that the water-conducting fracture zone gradually spreads to the upper aquifer, but the coal seam thickness is not greater than ; When the overlying aquifer changes from weakly water-rich to basically water-free, coal resources can be mined in accordance with normal conditions without the threat of water damage; Gradually increase the mining surface of the target coal seam until the target coal seam resources are liberated.

9. The method for dewatering and reducing pressure in a soft sandstone aquifer according to any one of claims 1 to 8, characterized in that: The following steps are also included: Redefine the target coal seam and first mining working face, and carry out mining based on the redetermined target coal seam and first mining working face.

10. The method for dewatering and reducing pressure in a soft sandstone aquifer according to claim 9, characterized in that: The re-determination of the target coal seam and the first mining working face includes: Based on the influence range of water-conducting fracture zones in coal seam mining and combined with the water level changes in the aquifer, the impact of coal seam mining on the overlying aquifer is analyzed; Conduct additional surface hydrological exploration drilling to test the water content of the overlying aquifer; Redefine the risk level of the aquifer, and based on the risk level of the aquifer and the type of coal pillar, redefine the target coal seam and the first mining working face.

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