Method of water-preserved coal mining in light-coloured clay area

Abstract

The present disclosure provides a method of water-preserved coal mining in a light-coloured clay area and relates to the technical field of water-preserved coal mining. The method of water-preserved c

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of water-preserved coal mining, and in particular, to a method of water-preserved coal mining in a light-coloured clay area. BACKGROUND

[0002] Light-coloured clay areas (also referred to as loess distribution areas) in western China are vulnerable in ecological environment but rich in coal resources. Coal mining in the light-coloured clay areas may cause leakage loss of water resources of the light-coloured clay areas, resulting in further ecological degradation of the light-coloured clay areas. To avoid the leakage loss of water resources, methods of water-preserved coal mining need to be used for mining coal in the light-coloured clay areas. Traditional methods of water-preserved coal mining mainly include: filling mining, strip-partial mining, light-coloured clay self-healing, reduction of a mining height, slicing mining, coordinated management of water resources based on an ecological water level, negative-pressure rebuilding of aquiclude, artificially grouting reinforcement, freezing of aquifer, and the like. However, the above traditional methods of water-preserved coal mining have the following defects:

[0003] (1) When the methods of water-preserved coal mining of strip-partial mining, reduction of a mining height, and slicing mining are used, coal recovery rates are low and coal resources may be wasted.

[0004] (2) When the methods of water-preserved coal mining of filling mining, artificially grouting reinforcement, and freezing of aquifer are used, a large engineering cost may be generated, leading to a high price.

[0005] (3) When the methods of water-preserved coal mining of light-coloured clay self-healing and negative-pressure rebuilding of aquiclude are used, long time periods may be needed and effects may not be stable.

[0006] (4) When the method of water-preserved coal mining of coordinated management of water resources based on an ecological water level is used, large-area water level monitoring and scheduling are required, and the method is not easy to implement.

[0007] On this basis, there is an urgent need for a method of water-preserved coal mining in a light-coloured clay area to solve the above problems. SUMMARY

[0008] An objective of the present disclosure is to provide a method of water-preserved coal mining in a light-coloured clay area that can achieve the purpose of water-preserved coal mining and can have the advantages of high coal resource recovery rate, low cost, short time period, stable effect, and simple and easy implementation.

[0009] To achieve the above objective, the present disclosure provides the following technical solutions.

[0010] A method of water-preserved coal mining in a light-coloured clay area includes:

[0011] within a vertical ground projection region of a coal mining working face, arranging a plurality of continuous sludge pools along a strike of the coal mining working face, where the sludge pools are communicated with the ground, but adjacent sludge pools are not communicated with each other; and the vertical ground projection region is a region obtained by projecting the coal mining working face onto the ground;

[0012] mining coal in the coal mining working face along the strike of the coal mining working face; and during advancing of the coal mining working face, filling the sludge pool next to a current advancing position of the coal mining working face, and continuously performing mechanical stirring on the filled sludge pool until coal mining is finished.

[0013] According to specific embodiments provided in the present disclosure, the present disclosure has the following technical effects:

[0014] The present disclosure provides a method of water-preserved coal mining in a light-coloured clay area, including: within a vertical ground projection region of a coal mining working face, arranging a plurality of continuous sludge pools along a strike of the coal mining working face, where the sludge pools are communicated with the ground, but adjacent sludge pools are not communicated with each other; mining coal in the coal mining working face along the strike of the coal mining working face; and during advancing of the coal mining working face, filling the sludge pool next to a current advancing position of the coal mining working face, and continuously performing mechanical stirring on the filled sludge pool until coal mining is finished. The present disclosure allows for full mining of all the coal resources within the coal mining working face, and the recovery rate of the coal resources is high. By taking advantage of the favorable opportunity of fractures opening under weighting during coal mining, the fractures are plugged effectively with eddies formed by gravity and stirring. The engineering cost can be saved and the cost is relatively low. With good plugging characteristic of sludge soil, coal mining and plugging can be carried out simultaneously, thereby reducing the time period and achieving a better effect. There is no need for large-region water level monitoring and scheduling, and simple and easy implementation can be realized. Therefore, the present disclosure can achieve the purpose of water-preserved coal mining and can have the advantages of high coal resource recovery rate, low cost, short time period, stable effect, and simple and easy implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] To describe the technical solutions in embodiments of the present disclosure or in the prior art more clearly, the accompanying drawings required for the embodiments are briefly described below. Apparently, the accompanying drawings in the following description show merely some embodiments of the present disclosure, and those of ordinary skill in the art may still derive other accompanying drawings from these accompanying drawings without creative efforts.

[0016] FIG. 1 is a flowchart of a method of water-preserved coal mining provided in Example 1 of the present disclosure; and

[0017] FIG. 2 is a detailed flowchart of the method of water-preserved coal mining provided in Example 1 of the present disclosure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] The technical solutions of the embodiments of the present disclosure are clearly and completely described below with reference to the drawings in the embodiments of the present disclosure. Apparently, the described embodiments are merely a part rather than all of the embodiments of the present disclosure. All other embodiments derived from the embodiments in the present disclosure by a person of ordinary skill in the art without creative efforts shall fall within the protection scope of the present disclosure.

[0019] An objective of the present disclosure is to provide a method of water-preserved coal mining in a light-coloured clay area that can achieve the purpose of water-preserved coal mining and can have the advantages of high coal resource recovery rate, low cost, short time period, stable effect, and simple and easy implementation.

[0020] In order to make the above objective, features, and advantages of the present disclosure clearer and more comprehensible, the present disclosure will be further described in detail below in combination with accompanying drawings and particular implementation modes.

[0021] Example 1:

[0022] As shown in FIG. 1 and FIG. 2, this example provides a method of water-preserved coal mining in a light-coloured clay area, including the following steps.

[0023] SI: within a vertical ground projection region of a coal mining working face, a plurality of continuous sludge pools are arranged along a strike of the coal mining working face, where the sludge pools are communicated with the ground, but adjacent sludge pools are not communicated with each other; and the vertical ground projection region is a region obtained by projecting the coal mining working face onto the ground.

[0024] In this example, the coal mining working face is a work site of coal mining, namely a three-dimensional working region to be mined for coal. The vertical ground projection region of the coal mining working face can be determined by projecting the coal mining working face onto the ground. A plurality of continuous sludge pools are then arranged within the vertical ground projection region of the coal mining working face. The plurality of continuous sludge pools are distributed along the strike of the coal mining working face. Each sludge pool is communicated with the ground; and adjacent sludge pools are not spaced apart, but are not communicated with each other.

[0025] In this example, each sludge pool has the same structure. The sludge pool is provided with a cover for preventing evaporation and enclosed. Each sludge pool has a width of 1.5-2.5 times D, a length of 1.1-1.3 times an oblique length of the coal mining working face away from a weighting point, and a height of 2-4 Mx(l-w). In this example, the sludge pool has the width of 1.5 D to 2.5 D, the length of 1.1 C to 1.3 C, and the height of 2 M (1-w) to 4 M (1-w), where D represents a weighting interval of the coal mining working face; C represents the oblique length of the coal mining working face, namely a width of the coal mining working face; M represents a coal mining thickness of the coal mining working face; and w represents a subsidence factor of the coal mining working face.

[0026] To determine a size of the sludge pool, before coal mining, two parameters (including subsidence factor w and weighting interval D) of the coal mining working face need to be determined first. Specifically, a physical scaled model may be established in accordance with a bore histogram, and the subsidence factor w and the weighting interval D are determined by physical simulation. Specifically, a process of determining the subsidence factor w and the weighting interval D is as follows: a physical scaled model of the coal mining working face is established based on a bore histogram of the coal mining working face. The bore histogram is a main data outcome of geological logging of drill holes, and is an original map compiled according to observation and identification of bore rock (ore) core (or rock debris, or rock powder), sampling analysis, and data obtained through various tests performed within the bore. The bore histogram is used to visually express a rock stratum and an ore body that the bore passes through and an interrelationship therebetween, and is main basis for compiling related integrated maps and calculating mineral reserves. The main content of the map includes a footage per round trip, a rock (ore) core recovery, a horizon and a thickness of the rock stratum or the ore body, and description of rock (ore) core characteristics (including a material composition of rock and ore, a structure construction, a contact relationship and a level dip angle of the rock stratum or an ore bed, and the like), and outcomes of sample testing, simple hydrogeological observation in the bore, and geophysical logging, etc. After the bore histogram of the coal mining working face is obtained, a physical simulation model of the coal mining working face is established by an existing method. The physical simulation model may be regarded as a coal mining working face reduced for several times. Physical simulation is then performed on the physical scaled model of the coal mining working face so that the weighting interval and the subsidence factor of the coal mining working face can be determined. The method of physical simulation is an existing mature method, which will not be described here redundantly.

[0027] In this example, a volume of fractures is calculated according to the subsidence factor, the weighting interval, and the like in combination with mine pressure and rock stratum movement theories to design the size of the sludge pool, and the sludge needed can be controlled quantificationally.

[0028] S2: coal is mined in the coal mining working face along the strike of the coal mining working face; and during advancing of the coal mining working face, the sludge pool next to a current advancing position of the coal mining working face is filled, and mechanical stirring is continuously performed on the filled sludge pool until coal mining is finished.

[0029] In this example, the coal mining process of the coal mining working face is the advancing process of the coal mining working face. This example requires sequential filling prior to the coal mining working face advances to the sludge pools. That is, during the advancing process of the coal mining working face, the plurality of sludge pools arranged are filled orderly. The timing of each sludge pool is to fill when a coal mining advancing position is before one sludge pool. That is, during the advancing of the coal mining working face, the sludge pool next to the current advancing position of the coal mining working face is filled. Then, as the coal mining working face advances, the sludge pools are sequentially filled. It needs to be noted that “prior to” and “next to” in this example are defined according to the direction of the strike of the coal mining working face, and the advancing direction of the coal mining working face may be regarded as “next to”.

[0030] In this example, materials that the sludge pool is filled with may include sludge, clean mine water, coal gangue, and live Bacillus megaterium and metabolite thereof. The sludge is sludge salvaged from water and filtered through a 100-200-mesh sieve. The clean mine water is mine water that is not mixed with coal, lubricating oil, and the like and directly drained from the bore. The coal gangue is coal gangue that contains more than 0.1% of P2O3 and more than 60% of clay minerals and is crushed and filtered through the 100-200-mesh sieve. Thus, filling the sludge pool next to the current advancing position of the coal mining working face may include: fill the sludge pool next to the current advancing position of the coal mining working face with sludge, clean mine water, coal gangue, and live Bacillus megaterium and metabolite thereof, where the clean mine water is mine water directly drained from the bore, and a mass ratio of the sludge to the clean mine water, the coal gangue, and the live Bacillus megaterium and the metabolite thereof is (1-2):(1-2):(0.3-0.5):(0.0001-0.0002).

[0031] In this example, the coal gangue and the Bacillus megaterium are added to the sludge pool, and the Bacillus megaterium is beneficial to decompose a phosphorus fertilizer in the coal gangue, which is beneficial for subsequent vegetation restoration.

[0032] After the completion of filling the sludge pool, mechanical stirring is continuously performed on the filled sludge pool, and the stirring is stopped until the coal mining is finished, where when the mechanical stirring is continuously performed on the filled sludge pool, a stirring rate is greater than 30 r / min.

[0033] In this example, before coal mining, a downhole sludge pumping system of the coal mining working face is set up. Specifically, before mining coal in the coal mining working face along the strike of the coal mining working face, the method of water-preserved coal mining in this example further includes: set a one-hour pumping capability of a downhole sludge pumping system of the coal mining working face, the one-hour pumping capability of the downhole sludge pumping system being greater than 1.2 B, where B represents a sum of an one-hour water inflow of a mine in aquifer and an one-hour water inflow of a maximum volume of the sludge pool. The one-hour water inflow of the mine in the aquifer may be calculated by a big well method or an analogue method established in the industry. The one-hour water inflow of the maximum volume of the sludge pool may be obtained by using a same height of water head and same fillers based on existing fractures in the ground. The height of water head refers to a difference between a bottom height of the sludge pool and a roof height of the coal mining working face.

[0034] Since working is based on weighting in this example, when coal mining is performed on the coal mining working face, during the advancing of the coal mining working face, when an advancing distance has reached 1.1 times the weighting interval D but there is no weighting, artificial forced caving is performed until the coal mining is finished. Specifically, during the advancing of the coal mining working face, the method of water-preserved coal mining in this example further includes: determine whether the advancing distance of the coal mining working face is greater than 1.1 D, where the advancing distance is 0 after weighting of the coal mining working face, and D represents the weighting interval; and if yes, perform artificial forced caving, and set the advancing distance to 0.

[0035] To further protect the ecological environment of the light-coloured clay area, the ground sludge pools and fillers are removed in 3 months to 12 months after the coal mining is finished, and vegetation is planted in the ground again. Specifically, after the coal mining is finished, the method of water-preserved coal mining in this example further includes: determine whether a time interval to the coal mining being finished is greater than a preset duration, where the preset duration may be 3 to 12 months; and if yes, remove the sludge pool and the fillers in the sludge pool, and plant vegetation in the ground.

[0036] The method of water-preserved coal mining in a light-coloured clay area provided in this example can not only achieve the purpose of water-preserved coal mining but also have the following advantages as compared with the prior art:

[0037] (1) High coal resource recovery rate

[0038] Since the methods of water-preserved coal mining of strip-partial mining, reduction of a mining height, and slicing mining may have the problem that the coal resources in partial region within the coal mining working face cannot be mined, the method of water-preserved coal mining in a light-coloured clay area used in this example can normally mine the coal resources within the coal mining working face and can fully mine the coal resources. Therefore, compared with the methods of water-preserved coal mining of strip-partial mining, reduction of a mining height, and slicing mining, this example can allow for an increased coal resource recovery rate and avoidance of wasting of coal resources.

[0039] (2) Relatively low cost

[0040] The methods of water-preserved coal mining of filling mining, artificially grouting reinforcement, and freezing of aquifer are downhole filling methods and require use of a downhole filling process and bore drilling, and such methods of water-preserved coal mining are all for the purpose of not producing fractures and have high requirements on properties of coagulating materials. Therefore, a lot of engineering costs may be produced, leading to a high price. Compared with traditional grouting, this example takes into account that water burst and sand inrush phenomena may not occur due to the presence of light-coloured clay. Moreover, the development of fractures is relatively limited after mining of light-coloured clay, and plugging may be carried out in combination with sludge soil. Therefore, by taking advantage of the favorable opportunity of fractures opening under weighting during coal mining, the method of water-preserved coal mining in this example can effectively plug the fractures with eddies formed by gravity and stirring. Since the sludge pools are arranged on the ground, the method is a ground filling method, and thus there is no need for bore drilling. Moreover, for the purpose of firstly fracturing and then plugging, low requirements are imposed on coagulating materials. Therefore, compared with the methods of water-preserved coal mining of filling mining, artificially grouting reinforcement, and freezing of aquifer, the method of water-preserved coal mining in this example can save the engineering cost and is relatively low in cost.

[0041] (3) Short period and better effect

[0042] The methods of water-preserved coal mining of light-coloured clay self-healing and negative-pressure rebuilding of aquiclude allow for separate coal mining and plugging, namely plugging after the completion of coal mining, and therefore, long time periods may be needed and effects may not be stable. The method of water-preserved coal mining in this example mainly takes advantage of the good plugging characteristic of the sludge soil. Compared with the permeability coefficient of the traditional soil layer, the permeability coefficient of the sludge soil is lower by more than one order of magnitude. Of course, this process is relatively slow. Therefore, during coal mining and stabilization, the fractures may be plugged with the sludge soil without taking extra time. That is, the method of water-preserved coal mining in this example allows for simultaneous coal mining and plugging. Compared with the methods of water-preserved coal mining of light-coloured clay self-healing and negative-pressure rebuilding of aquiclude, the time period can be shortened and a better effect can be achieved.

[0043] (4) Simple and easy implementation

[0044] Since the method of water-preserved coal mining of coordinated management of water resources based on an ecological water level requires large-region water level monitoring and scheduling and is not easy to implement, and the method of water-preserved coal mining in this example does not require large-region water level monitoring and scheduling. Therefore, compared with the method of water-preserved coal mining of coordinated management of water resources based on an ecological water level, the method of water-preserved coal mining in this example is simple and easy to implement.

[0045] The method of water-preserved coal mining in this example relates to the crossing field of mine hydrogeology and mining engineering. For the defects of the traditional methods of water-preserved coal mining, there is provided a novel method of water-preserved coal mining in a light-coloured clay area that can solve the problems of the traditional methods of water-preserved coal mining. Compared with the prior art, this example has the following beneficial effects: (1) simple and easy implementation; (2) relative low cost; (3) high coal resource recovery rate; and (4) short period and better effect.

[0046] Here, this example provides the following application example:

[0047] For an ecologically fragile light-coloured clay distribution mine area, during previous 2-2# coal mining, subsurface water is lost, and a large amount of ecological degradation is induced. To realize water-preserved coal mining, during mining within 2204 working face, the following operations are conducted:

[0048] Step 1, two parameters (including subsidence factor w and weighting interval D) of the coal mining working face are determined. Specifically, the physical scaled model is established in accordance with the bore histogram, and the subsidence factor w and the weighting interval D of the coal mining working face are determined by physical simulation as follows: w=0.65 and D=24 m.

[0049] Step 2, the sludge pools are arranged in the vertical ground projection region of the coal mining working face. The sludge pools are distributed along the strike of the coal mining working face. The width of each sludge pool is 1.5-2.5 times D, and therefore, the width is specifically 36-60 m. The length to the weighting point is 1.1-1.3 times the oblique length of the coal mining working face, and the length is specifically 132-156 m. The height is 2-4 times M*(l-w), Mx(l-w)=3.5x0.35=1.225, and therefore, the height is specifically 2.45-4.9 m. The sludge pools are communicated with the ground, and each sludge pool is provided with a cover for preventing evaporation and enclosed. The sludge pools are not communicated with one another.

[0050] Step 3, sequential filling is carried out before the coal mining working face advances to the sludge pools. Materials for filling include sludge, clean mine water, coal gangue, and live Bacillus megaterium and metabolite thereof, where a ratio of the sludge, the clean mine water, the coal gangue, and the live Bacillus megaterium and the metabolite thereof is 1.5:1.5:0.4:0.00015. The sludge is sludge salvaged from water and filtered through the 100-200-mesh sieve. The clean mine water is mine water that is not mixed with coal, lubricating oil, and the like and directly drained from the bore. The coal gangue is coal gangue that contains more than 0.1% of P2O3 and 72% of clay minerals and is crushed and filtered through the 100-200-mesh sieve. The timing of filling is to fill when the coal mining advancing position is before one sludge pool. Mechanical stirring is performed on the sludge pool after filling, and the stirring is stopped until the coal mining is finished. The stirring rate is 60 r / min.

[0051] Step 4, before the coal mining, the downhole sludge pumping system of the coal mining working face is set up. The one-hour pumping capacity of the downhole sludge pumping system is 600 m3 / h, which is equal to 1.3 times the one-hour water inflow of the mine in the aquifer + the one-hour water inflow of the maximum volume of the sludge pool.

[0052] Step 5, coal is mined in the coal mining working face. There is no weighting twice when the coal mining working face reaches 26.4 m. In this case, artificial forced caving is carried out until the coal mining is finished.

[0053] Step 6, the ground sludge pools and fillers are removed in 10 months after the coal mining is finished, and vegetation is planted in the ground again.

[0054] After coal mining in this working face, the sludge fills the aquiclude; the water level recovers one year later; the vegetation planted in the ground is lusher before the coal mining; and the coal resources are mined efficiently with a high recovery rate. The purpose of water-preserved coal mining is achieved.

[0055] Specific examples are used herein for illustration of the principles and embodiments of the present disclosure. The description of the foregoing embodiments is used to help understand the method of the present disclosure and the core principles thereof. In addition, those of ordinary skill in the art can make various modifications in terms of specific embodiments and scope of application in accordance with the teachings of the present disclosure. In conclusion, the content of the description shall not be construed as limitations to the present disclosure.

Claims

1. A method of water-preserved coal mining in a light-coloured clay area, comprising:within a vertical ground projection region of a coal mining working face, arranging a plurality of continuous sludge pools along a strike of the coal mining working face, wherein the sludge pools are communicated with the ground, but adjacent sludge pools are not communicated with each other; and the vertical ground projection region is a region obtained by projecting the coal mining working face onto the ground;mining coal in the coal mining working face along the strike of the coal mining working face; and during advancing of the coal mining working face, filling the sludge pool next to a current advancing position of the coal mining working face, and continuously performing mechanical stirring on the filled sludge pool until coal mining is finished.

2. The method of water-preserved coal mining according to claim 1, wherein the sludge pool has a width of 1.5 D to 2.5 D, a length of 1.1 C to 1.3 C, and a height of 2 M (1-w) to 4 M (1-w), wherein D represents a weighting interval of the coal mining working face; C represents an oblique length of the coal mining working face; M represents a coal mining thickness of the coal mining working face; and w represents a subsidence factor of the coal mining working face.

3. The method of water-preserved coal mining according to claim 1 or 2, wherein a process of determining the weighting interval and the subsidence factor comprises: establishing a physical scaled model of the coal mining working face based on a bore histogram of the coal mining working face; and performing physical simulation on the physical scaled model to determine the weighting interval and the subsidence factor of the coal mining working face.

4. The method of water-preserved coal mining according to any preceding claim, wherein the filling the sludge pool next to a current advancing position of the coal mining working face specifically comprises:filling the sludge pool next to the current advancing position of the coal mining working face with sludge, clean mine water, coal gangue, and live Bacillus megaterium and metabolite thereof, wherein a mass ratio of the sludge to the clean mine water, the coal gangue, and the live Bacillus megaterium and the metabolite thereof is (1-2):(1-2):(0.3-0.5):(0.0001-0.0002); and the clean mine water is mine water directly drained from a bore.

5. The method of water-preserved coal mining according to any preceding claim, wherein when mechanical stirring is continuously performed on the filled sludge pool, a stirring rate is greater than 30 r / min.

6. The method of water-preserved coal mining according to qany preceding claim, before the mining coal in the coal mining working face along the strike of the coal mining working face, further comprising: setting a one-hour pumping capability of a downhole sludge pumping system of the coal mining working face, the one-hour pumping capability being greater than 1.2 B, wherein B represents a sum of an one-hour water inflow of a mine in aquifer and an one-hour water inflow of a maximum volume of the sludge pool.

7. The method of water-preserved coal mining according to any preceding claim, during the advancing of the coal mining working face, further comprising:determining whether an advancing distance of the coal mining working face is greater than 1.1 D, wherein the advancing distance is 0 after weighting of the coal mining working face, and D represents the weighting interval; andif yes, performing artificial forced caving, and setting the advancing distance to 0.

8. The method of water-preserved coal mining according to any preceding claim, after the coal mining is finished, further comprising:determining whether a time interval to the coal mining being finished is greater than a preset duration; andif yes, removing the sludge pool and the fillers in the sludge pool, and planting vegetation in the ground.13

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