A gas control system for soft rock of coal seam floor

Abstract

The utility model discloses a kind of gas control system for coal seam floor soft rock, it is related to coal mine gas control technical field.Aiming at the problem of gas storage and lower coal seam gas abnormal emission caused by soft rock layer floor, a system management scheme is presented.The system comprises: in auxiliary air entry crossheading or return air crossheading arrangement bottom drilling field, through small angle inclination pouring and setting drainage groove, optimization downward drilling construction condition;Adopt fan-shaped opening, parallel terminal hole's directional long drilling hole process, in combination with screen pipe hole protection and branch hole design, improve hole rate and extraction efficiency;Through the arrangement of extraction pipeline realizes during tunneling pre-extraction and during stoping pressure relief gas interception extraction.The utility model effectively solves the technical problems, such as soft rock layer drilling construction difficulty, water accumulation in hole and poor residue discharge, significantly improves gas extraction effect and working face safety, ensures tunneling and stoping period safety production, has important engineering application value and popularization prospect.

Description

Technical Field

[0001] This utility model relates to the field of underground gas control technology in coal mines, and in particular to a gas control system for soft rock at the bottom of coal seams. Background Technology

[0002] In recent years, with the continuous optimization of mining techniques and methods, and the increase in mining depth and intensity, gas outbursts from adjacent coal seams have become a core issue restricting safe and efficient coal mine production. To keep pace with production demands, roadway spans have gradually increased, and mining depths have shifted towards deeper layers, leading to more prominent geological structures and increasingly complex geological conditions. Due to the continuous increase in ground stress, the mud content of rock strata has increased, cementing performance has decreased, and significant rheological characteristics have emerged, especially in the soft rock floor. Because the floor of the upper coal seam is composed of dense soft rock, and the lower coal seam is relatively close to the upper one, the soft rock floor has a strong ability to contain gas, forming a barrier layer that makes it difficult for gas to pass through, creating gas pockets on the coal seam floor. Affected by mining activities, coupled with the expansion of soft rock upon contact with water, fissures appear in the floor, increasing the permeability of the lower coal seam. Gas from the lower coal seam continuously escapes into the upper coal seam, causing abnormal gas outbursts during the upper coal seam mining phase, bringing numerous inconveniences to safe mine production.

[0003] Currently, in China, for mines primarily experiencing gas outbursts from adjacent coal seams, high-level drainage methods such as high-level drainage roadways and high-level boreholes are commonly used. These methods are effective for mines with gas outbursts primarily from adjacent coal seams. For mines with gas outbursts primarily from lower adjacent coal seams, the main approach is to construct upward-facing cross-seam boreholes within bottom drainage roadways to pre-drain gas from the lower adjacent seams. However, this method involves a large amount of construction work and a long construction period. Some scholars have also proposed using directional boreholes in the upper floor to intercept and drain gas from the lower coal seam, but this method involves a large downward drilling angle, which can cause problems such as water accumulation and difficulty in removing slag. This is especially problematic when encountering adjacent coal seams with soft rock floor layers, where the difficulty of construction increases exponentially and effective drainage cannot be maintained during mining. Therefore, a new, targeted treatment method is urgently needed to effectively manage abnormal gas outbursts caused by adjacent coal seams with soft rock floor layers. Utility Model Content

[0004] To address the aforementioned issues, this invention proposes a gas control system for soft rock at the bottom of coal seams. This system significantly improves the construction efficiency and borehole formation rate of downward drilling in adjacent coal seams with soft rock bottoms, ensuring that abnormal gas outbursts from the lower coal seam to the upper coal seam are controllable during the excavation and mining of the fully mechanized longwall face, thereby enhancing mine safety.

[0005] To achieve the above objectives, the technical solution adopted by this utility model is as follows: A gas control system for soft rock in coal seam floor. Auxiliary intake airway or auxiliary return airway is excavated on both sides of the fully mechanized mining face of the upper coal seam. Underground drilling sites that can cover the entire fully mechanized mining face are evenly arranged on the side of the auxiliary intake airway or auxiliary return airway closest to the fully mechanized mining face. Directional extraction boreholes covering the entire longwall mining face are drilled evenly in the direction of the cut-in point of the longwall mining face from the underground drilling site. The return airway is equipped with a main roadway drainage pipe, and the auxiliary intake or return airway on the side of the fully mechanized longwall face of the upper coal seam is equipped with a working face drainage pipe. Each directional drainage borehole is connected to the working face drainage pipe and then to the main roadway drainage pipe for drainage. The drainage boreholes, working face drainage pipes, and main roadway drainage pipes are used for negative pressure pre-drainage of gas from the lower coal seam. Preferably, the extraction borehole is a fan-shaped opening with a parallel end.

[0006] Preferably, a submerged drilling site is arranged at most every 300m on the side of the auxiliary intake airway or auxiliary return airway near the fully mechanized mining face.

[0007] Preferably, there are multiple underground drilling sites, and the underground drilling sites are arranged evenly in sequence along the direction from the stop line to the auxiliary cut.

[0008] Preferably, the bottom drilling site has a height of 2.5-3m, a width of 8-12m, a depth of 4-7m, and a bottom depth of 1.3-1.8m.

[0009] Preferably, the underground drilling site has a drainage ditch with an inclination angle of -1-2°, a depth of 3cm, and a width of 5cm, and the underground drilling site also has a water pumping ditch with a width of 50cm and a length of 50cm.

[0010] Preferably, the extraction borehole includes a main borehole and branch boreholes formed by the branches of the main borehole. Each main borehole is designed with 1-2 branch boreholes, and the extraction long drill has a screen pipe inside to prevent the borehole from collapsing.

[0011] Preferably, each of the aforementioned underground drilling sites is designed and constructed with 10-15 extraction boreholes, the length of which is 250-300m, and the final hole spacing between adjacent extraction boreholes is 10-12m.

[0012] Preferably, the thickness of the upper coal seam is 2.5-3.5m, the thickness of the lower coal seam is 0.4-0.6m, and the distance between the upper and lower coal seams is 4.5-5.5m.

[0013] The beneficial effects of using this utility model are: This gas control system for soft rock floor coal seams effectively controls the abnormal phenomenon of gas inrushes from lower coal seams into upper coal seams by combining the deployment of underground drilling sites, the layout and construction of extraction boreholes, the installation of extraction pipelines, and pre- and mid-term extraction during mining. This ensures safe production during tunneling and mining. This system improves the practicality and versatility of gas control in nearby coal seams, generating significant economic and social benefits. Especially for mines with soft rock floor layers, unminable conditions, high gas content, and adjacent coal seams primarily affected by gas inrushes from lower, nearby layers, this invention provides a novel and more targeted solution. Attached Figure Description

[0014] Figure 1 This is a top view of the gas control system for soft rock at the bottom of a coal seam provided by this utility model.

[0015] Figure 2 This is a cross-sectional view of the gas control system for soft rock at the bottom of a coal seam provided by this utility model.

[0016] The reference numerals in the figures include: 100 - Fully mechanized longwall face; 101 - Return airway; 102 - Belt conveyor roadway; 103 - Track roadway; 200 - Longwall face extraction pipe; 201 - Main roadway extraction pipe; 202 - Cut-in; 203 - Auxiliary cut-in; 204 - Extraction borehole; 300 - Auxiliary intake airway; 301 - Belt conveyor intake airway; 302 - Track return airway; 303 - Auxiliary return airway; 400 - Underground drilling site; 500 - Upper mining coal seam; 501 - Shallow soft rock; 502 - Lower coal seam. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this technical solution clearer, the following detailed description, in conjunction with specific embodiments, further illustrates this technical solution. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of this technical solution.

[0018] like Figure 1 and Figure 2As shown, this embodiment takes a coal yard as an example. From a top-down view and with the perspective facing the tunneling direction of the fully mechanized mining face 100, the basic structure of the mining layer of this coal yard is as follows: A return airway 101, a conveyor belt roadway 102, and a track roadway 103 are arranged perpendicular to the extension direction of the predetermined fully mechanized mining face 100. A main roadway extraction steel pipe 201 is arranged in the return airway 101. A conveyor belt intake airway 301 and an auxiliary intake airway 300 are arranged on the left side of the fully mechanized mining face 100, and a track return airway 302 and an auxiliary return airway 303 are arranged on the right side of the fully mechanized mining face 100. At the end of the fully mechanized mining face 100, a cut-in 202 and an auxiliary cut-in 203 are provided, generally perpendicular to the main extension direction of the fully mechanized mining face 100. The auxiliary intake airway 300 is connected to the auxiliary return airway 303 through the auxiliary cut-in 203. Cut-eye 202 connects the conveyor belt inlet airway 301 to the track return airway 302. Channels are provided for connection between the auxiliary inlet airway 300 and the conveyor belt inlet airway 301, between the track return airway 302 and the auxiliary return airway 303, and between cut-eye 202 and the auxiliary cut-eye 203. Additionally, the return airway 101, the conveyor belt main roadway 102, and the track main roadway 103 are connected by roadways.

[0019] The gas control system for soft rock at the bottom of coal seams proposed in this embodiment is characterized in detail according to the characteristics of the coal seam.

[0020] Set up underground drilling sites 400: During the tunneling process before the fully mechanized longwall face 100 of the upper coal seam 500 is formed, underground drilling sites 400 are evenly arranged every 300m along the direction from the stop line to the auxiliary cut-off point 203 on the side of the auxiliary air intake roadway 300 or auxiliary return air roadway 303 near the fully mechanized longwall face 100. These sites are 2.9m high, 9m wide, 5m deep, and have a 1.5m base. The bottom of the underground drilling site 400 is poured at a small angle of 1-2° and a drainage ditch with a depth of 3cm and a width of 5cm and a pumping ditch with a depth of 50cm, a width of 50cm, and a length of 50cm are provided. Each underground drilling site 400 is designed to have 13 drainage boreholes 204 with a diameter of Φ99mm. The final spacing between adjacent drainage boreholes 204 is 10-12m.

[0021] Arrangement and construction of extraction borehole 204: Using a fan-shaped opening and parallel final hole downward directional drilling method, a long directional borehole, namely extraction borehole 204, is uniformly constructed from the bottom drilling site 400 towards the cut-in 202 of the fully mechanized mining face 100, covering the entire fully mechanized mining face 100. Extraction borehole 204 penetrates the shallow soft rock 501. Extraction borehole 204 includes a main borehole and branch boreholes formed by branches of the main borehole. Each main borehole is designed with 1-2 branch boreholes. Screen pipes are placed during the construction of extraction borehole 204 to prevent borehole collapse.

[0022] Drainage pipeline layout: For the 500m longwall face in the upper mining section, 100m of the auxiliary intake roadway or 300m of the auxiliary return air roadway, a 200mm drainage pipe is installed. Each directional long borehole is connected to the Φ377mm drainage pipe 200mm, and then connected to the Φ711mm main roadway drainage pipe for drainage. The negative pressure at the borehole opening of the pre-drainage borehole must not be lower than 13kPa.

[0023] Pre- and mid-term gas extraction: During the tunneling process before mining, the advanced downward directional long borehole is used to pre-extract the gas from the lower coal seam 502 through the working face extraction steel pipe 200 with a negative pressure of not less than 13 kPa; during mining, the floor plate is cracked due to mining, and the permeability of the lower coal seam 502 increases. The working face extraction steel pipe 200 is used to intercept and extract the depressurized gas with negative pressure.

[0024] Specifically, when setting up the underground drilling site 400, at most one underground drilling site 400 is set up every 300m on the side of the auxiliary intake airway 300 or auxiliary return airway 303302 near the fully mechanized mining face 100, and is evenly arranged in sequence along the direction from the stop line to the auxiliary cut-out 203 according to the tunneling progress.

[0025] When setting up the underground drilling site 400, the underground drilling site 400 with a height of 2.9m, a width of 9m, a depth of 5m, and a bottom depth of 1.5m is evenly arranged on the side of the auxiliary intake airway 300 or auxiliary return airway 303 near the fully mechanized mining face 100.

[0026] The 400-meter-deep drilling site is constructed with a 1-2° inclined pour, and drainage channels with a depth of 3cm and a width of 5cm and a water pumping channel with a depth of 50cm, a width of 50cm and a length of 50cm are provided. The inclined pouring at a small angle facilitates drainage and slag removal by minimizing the downward angle of the borehole. The water channels help keep the drilling area dry, effectively reducing the swelling and stickiness of mudstone when exposed to water, thus ensuring efficient construction.

[0027] When arranging and constructing extraction borehole 204, extraction borehole 204 includes a main borehole and branch boreholes formed by branches of the main borehole. Each main borehole is designed with 1-2 branch boreholes. Screen pipes are placed during the construction of long extraction boreholes to prevent borehole collapse.

[0028] When arranging and constructing extraction boreholes 204, each underground drilling site 400 is designed to construct 13 extraction boreholes 204 with a diameter of Φ99mm. The length of extraction boreholes 204 should be around 300m, and the final hole spacing between adjacent extraction boreholes 204 should be 10-12m.

[0029] When arranging the extraction pipeline, each directional long borehole should be connected to the Φ377mm working face extraction steel pipe for 200mm, and then connected to the Φ711mm main roadway extraction steel pipe for extraction. The negative pressure at the borehole opening of the pre-extraction borehole should not be lower than 13kPa.

[0030] The upper coal seam 500 has a thickness of 3m, the lower coal seam 502 has a thickness of 0.5m, and the distance between the two is 5m.

[0031] The features of this system are as follows: 1. This system, by deploying a 400mm underboring drill field, can reduce the downward drilling angle, minimizing water accumulation and difficulties in slag removal within the borehole. The 400mm underboring drill field construction can traverse shallow mudstone, reducing the drilling distance within the mudstone and simplifying construction. Inclined pouring and water channels effectively reduce mudstone expansion and viscosity upon contact with water, resulting in efficient construction.

[0032] 2. During the construction of extraction borehole 204, the placement of screen pipes effectively prevents borehole collapse. Extraction borehole 204 includes a main borehole and branch boreholes formed by branches of the main borehole, with 1-2 branch boreholes designed for each main borehole. Extraction borehole 204, precisely designed according to the coal mine's extraction conditions, can accurately control negative pressure and extraction volume, avoiding resource waste caused by large-scale projects and long construction periods.

[0033] 3. During the pre-mining stage, the advanced downward directional long boreholes effectively pre-extract gas from adjacent coal seams, suppressing the influx of gas from the lower coal seam 502 into the upper mining coal seam 500, ensuring safe tunneling. During mining, the floor cracks caused by mining activities increase the permeability of the lower coal seam 502. At this time, the directional extraction borehole 204 changes from pre-extracting gas from adjacent coal seams to intercepting and extracting depressurized gas, effectively controlling the abnormal phenomenon of gas influx into the upper mining coal seam 500 caused by coal seam depressurization, ensuring safe mining.

[0034] It should be noted that, in the description of this utility model, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this utility model. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. At the same time, in the description of this utility model, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in this utility model can be understood according to the specific circumstances.

[0035] The above content is only a preferred embodiment of this utility model. For those skilled in the art, many changes can be made in the specific implementation and application scope based on the ideas of this technical content. As long as these changes do not depart from the concept of this utility model, they all fall within the protection scope of this patent.

Claims

1. A gas control system for soft rock in coal seam floor, characterized in that: Auxiliary intake airway or auxiliary return airway is excavated on both sides of the fully mechanized mining face of the upper coal seam. Underground drilling sites that can cover the entire fully mechanized mining face are evenly arranged on the side of the auxiliary intake airway or auxiliary return airway closest to the fully mechanized mining face. Directional extraction boreholes covering the entire longwall mining face are drilled evenly in the direction of the cut-in point of the longwall mining face from the underground drilling site. The return airway is equipped with a main roadway extraction steel pipe. The auxiliary intake or return airway on the side of the fully mechanized mining face of the upper coal seam is equipped with a working face extraction steel pipe. Each directional extraction borehole is connected to the working face extraction steel pipe and then to the main roadway extraction steel pipe for extraction. The extraction boreholes, working face extraction steel pipes, and main roadway extraction steel pipes are used for negative pressure pre-extraction of gas from the lower coal seam.

2. The gas control system for soft rock in coal seam floor according to claim 1, characterized in that: The extraction borehole has a fan-shaped opening and a parallel end point.

3. The gas control system for soft rock in coal seam floor according to claim 1, characterized in that: The auxiliary intake or return air roadway is provided with a maximum of one underground drilling site every 300m on the side closest to the fully mechanized mining face.

4. The gas control system for soft rock in coal seam floor according to claim 3, characterized in that: There are multiple underground drilling sites, and they are evenly arranged sequentially along the direction from the stop line to the auxiliary cut.

5. The gas control system for soft rock in coal seam floor according to claim 1, characterized in that: The bottom drilling site has a height of 2.5-3m, a width of 8-12m, a depth of 4-7m, and a bottom depth of 1.3-1.8m.

6. The gas control system for soft rock in coal seam floor according to claim 1, characterized in that: The underground drilling site has a drainage ditch with an inclination angle of -1-2°, a depth of 3cm, and a width of 5cm. The underground drilling site also has a water pumping ditch with a width of 50cm and a length of 50cm.

7. The gas control system for soft rock in coal seam floor according to claim 1, characterized in that: The extraction borehole includes a main borehole and branch boreholes formed by the main borehole branches. Each main borehole is designed with 1-2 branch boreholes. The extraction long drill has a screen pipe inside to prevent the borehole from collapsing.

8. The gas control system for soft rock in coal seam floor according to claim 1, characterized in that: Each of the aforementioned underground drilling sites is designed and constructed with 10-15 extraction boreholes, with a length of 250-300m and a final hole spacing of 10-12m between adjacent extraction boreholes.

9. The gas control system for soft rock in coal seam floor according to claim 1, characterized in that: The thickness of the upper coal seam is 2.5-3.5m, the thickness of the lower coal seam is 0.4-0.6m, and the distance between the upper and lower coal seams is 4.5-5.5m.

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