A method for setting up large and small coal pillars in a return air crossheading of a gob-side entry driving working face

Abstract

This invention relates to a method for leaving large and small coal pillars in the return airway of a goaf-side excavation roadway following a replacement working face. It belongs to the field of goaf-side excavation technology and solves the technical problems of high loss rates when using large coal pillars for roadway protection in existing fully mechanized longwall mining, and significant susceptibility to mining-induced disturbances when using small coal pillars for roadway protection. The solution is as follows: A method for leaving large and small coal pillars in the return airway of a goaf-side excavation roadway following a replacement working face, comprising the following steps: 1) determining basic parameters; 2) calculating the width of the small coal pillar; 3) calculating the width of the large coal pillar; 4) calculating the safe distance of the coal pillar from which mining-induced disturbances do not affect it; 5) calculating the distance from the first working face; 6) calculating the time for the B tunneling machine to excavate from the second return airway to the small coal pillar; 7) calculating the length of the large coal pillar; 8) calculating the length of the small coal pillar. Compared with existing technologies, this invention has advantages such as improving the recovery rate of the working face, increasing profits, reducing the impact of mining-induced disturbances on roadway excavation, and facilitating subsequent production planning.

Description

Technical Field

[0001] This invention belongs to the field of goaf excavation technology, specifically relating to a method for leaving large and small coal pillars in the return airway of a goaf excavation project following a working face. Background Technology

[0002] In the process of coal mining, in order to ensure the continuity and efficiency of production, a new working area is usually opened up near the working face that is about to be mined out or the working face that cannot meet the production needs. This is called a "replacement working face".

[0003] Large coal pillar roadway protection was a commonly used method in my country in the past. The width of the coal pillar was generally 20-30 meters. With the increase in coal thickness and mining depth, the width of the coal pillar in some mines reached 40-60 meters, causing significant resource losses. Surveys show that the coal loss rate caused by wide coal pillar roadway protection reaches 10%-30%, ranking first among various sources of coal resource waste in Chinese mines. How to reduce coal pillar loss while ensuring safety and high production efficiency is an important task for green mining in my country's coal mines. Therefore, small coal pillar roadway protection has emerged. Small coal pillar roadway protection technology can effectively improve coal extraction rate and solve many problems in roadway maintenance. In the current context of increasingly scarce coal resources, it has extremely important theoretical and practical significance. However, the stress environment and the degree of impact from mining activities in fully mechanized longwall mining differ from those in conventional longwall mining. Compared to wide coal pillar mining, the small coal pillar roadway protection technology in fully mechanized longwall mining is more susceptible to mining activities, leading to more severe mine pressure manifestations. Summary of the Invention

[0004] In order to overcome the shortcomings of existing technologies and solve the technical problems such as the large loss rate of leaving large coal pillars for roadway protection in existing fully mechanized longwall mining and the large impact of mining on leaving small coal pillars for roadway protection, this invention provides a method for leaving large and small coal pillars in the return airway of the goaf excavation roadway in the replacement working face.

[0005] The present invention is achieved through the following technical solutions.

[0006] This invention provides a method for leaving large and small coal pillars in the return air roadway of a working face during goaf excavation. Parallel longwall working faces are sequentially arranged with adjacent first, second, and third working faces. A goaf area is located on the right side of the first working face. A first return air roadway and a first transport roadway are located on both sides of the first working face. A second return air roadway and a second transport roadway are located on both sides of the second working face. The second return air roadway and the second transport roadway are connected by a second cut-out. A third transport roadway is located on one side of the third working face. The third transport roadway is connected to the second transport roadway by a third cut-out. Large and small coal pillars are left between the first transport roadway and the second return air roadway. Simultaneously, tunneling machine A excavates the second transport roadway and the second cut-out, while tunneling machine B excavates the third transport roadway and the third cut-out. After the third transport roadway and the third cut-out are excavated, tunneling machine B is moved to the starting point of the second return air roadway for further excavation. The tunneling speeds of tunneling machines A and B are the same. The method includes the following steps:

[0007] 1) Determine the specific parameters of the working face, tunneling machine A and tunneling machine B, and the coal seam;

[0008] 2) Set the width of the small coal pillar to be... ,according to The width of the small coal pillar was calculated. ,in The width of the plastic zone of the coal pillar, in meters; The effective support length of the coal face rock bolts in the upper section of the roadway is given in meters. The safety factor is 0.15-0.35;

[0009] 3) Set the width of the large coal pillar to be... ,according to The width of the large coal pillar was calculated. ,in The width of the plastic zone on the side of the goaf, and also the width of the plastic zone of the coal pillar, in meters; The width of the plastic zone on the side of the tunnel, in meters; The width of the elastic core;

[0010] 4) According to Calculate the safe distance of the coal pillar unaffected by mining activities at the working face. ,in The basic top thickness is in meters (m). The ultimate tensile strength of the basic top rock is given in MPa. The average unit weight of the overlying rock strata is kN / m³. For mining depth, m;

[0011] 5) According to Calculate the tunneling speed of tunneling machine A or tunneling machine B. and Calculate the mining speed of the first working face. ;in The advance distance during the tunneling cycle is measured in meters (m). Effective working hours per day, in hours (h); The excavation time for each cycle is in hours (h). The support time for each cycle is in hours (h). Let h be the auxiliary time for each loop; The daily output of the mining face is expressed in tons (t). To improve the efficiency of regular mining operations; The tunnel height is in meters (m). The length of the working surface is in meters (m). Density of coal, g / cm³ 3 ; Let m be the depth of cut for each cut;

[0012] 6) According to Calculate the time it takes for tunneling machine B to advance from the second return air roadway to the small coal pillar. Where L is the length of the working face, in meters; s is the width difference between the large and small coal pillars, in meters; The time taken for the tunneling machine to move from the third cut-in to the second return air roadway, in days; The time required to install the mining equipment is in days;

[0013] 7) According to Calculate the length of the large coal pillar to be reserved;

[0014] 8) According to Calculate the length of the small coal pillar to be left.

[0015] Furthermore, during the process of the B tunneling machine moving to the starting point of the second return air roadway, the mining equipment and the A tunneling machine continue to operate.

[0016] Furthermore, the formula for calculating the width of the plastic zone of the coal pillar in step 2) is: ,in b is the width of the plastic zone of the coal pillar, in meters; b is the height of the roadway, in meters. The internal friction angle of the coal; The stress concentration factor is 2-3; Cohesion of coal body, MPa; The resistance of the roadway support is measured in MPa.

[0017] Furthermore, the formula for calculating the width of the plastic zone on the roadway side in step 3) is: Where R is the equivalent radius of the tunnel, in meters; in a rectangular tunnel , The width of the alleyway is in meters (m). The tunnel height is in meters (m). The lateral pressure coefficient, , The value is Poisson's ratio for the coal.

[0018] Furthermore, the formula for calculating the elastic core width in step 3) is: .

[0019] The beneficial effects achieved by this invention are as follows: This invention proposes a method for reserving large and small protective coal pillars in the return airway of the working face during goaf excavation. Compared with the traditional method of reserving large coal pillars for roadway protection, this invention reduces the amount of coal pillars required, thereby increasing the recovery rate of the working face and increasing profits. Compared with the traditional method of reserving small coal pillars for roadway protection, this invention significantly reduces the impact of mining on roadway excavation and improves the efficiency of roadway excavation. Compared with the traditional method of goaf excavation, when reserving large coal pillars, a reverse pillar retention method is adopted, avoiding the deformation problem caused by "exposing the coal pillar first and then supporting it," thus increasing the stability of the area while ensuring resource conservation. This invention clarifies the length and width of the large and small coal pillars, providing clear parameter basis for mining planning and facilitating subsequent production planning.

[0020] Compared with existing technologies, this invention has the advantages of improving the recovery rate of the working face, increasing revenue, reducing the impact of mining on roadway excavation, and facilitating subsequent production planning. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the tunnel excavation process of the present invention.

[0022] In the diagram: 1. First working face; 2. Second working face; 3. Third working face; 4. Goaf; 5. First return air roadway; 6. First transport roadway; 7. Second return air roadway; 8. Second transport roadway; 9. Second cut-off; 10. Third transport roadway; 11. Third cut-off; 12. Large coal pillar; 13. Small coal pillar; 14. Stop line; 15. Advance direction of the first working face; 16. Turning point of B tunneling machine; 17. Excavation direction of B tunneling machine; 18. Excavation direction of A tunneling machine; 19. Main roadway protection coal pillar. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0024] like Figure 1As shown, 14 is the stop line, 15 is the direction of advancement of the first working face, 16 is the turning point of the B tunneling machine, 17 is the direction of advancement of the B tunneling machine, 18 is the direction of advancement of the A tunneling machine, and 19 is the main roadway protection coal pillar. A method for leaving large and small coal pillars in the return air roadway of a replacement working face along the goaf, wherein adjacent first working face 1, second working face 2, and third working face 3 are arranged in sequence along parallel longwall working faces. A goaf area 4 is located on the right side of the first working face 1. A first return air roadway 5 and a first transport roadway 6 are located on both sides of the first working face 1. A second return air roadway 7 and a second transport roadway 8 are located on both sides of the second working face 2. The second return air roadway 7 and the second transport roadway 8 are connected by a second cut-out 9. A third transport roadway 10 is located on one side of the third working face 3. The third transport roadway 10 is connected to the second transport roadway 6. The roadways 8 are connected by a third cut-in 11. A large coal pillar 12 and a small coal pillar 13 are left between the first transport roadway 6 and the second return air roadway 7. Simultaneously, tunneling machine A excavates the second transport roadway 8 and the second cut-in 9, while tunneling machine B excavates the third transport roadway 10 and the third cut-in 11. After the third transport roadway 10 and the third cut-in 11 are excavated, tunneling machine B is moved to the starting point of the second return air roadway 7 for further excavation. The tunneling speeds of tunneling machines A and B are the same. During the process of tunneling machine B moving to the starting point of the second return air roadway 7, the mining equipment and tunneling machine A continue to operate, including the following steps:

[0025] 1) Determine the specific parameters of the working face, tunneling machine A and tunneling machine B, and the coal seam.

[0026] Specifically, in this embodiment, the dimensions of the tunneling roadway at the working face are 4.2*2.5m, the mining depth H is 600m, the strike length L of the working face is 1000m, the length D of the working face is 200m, the daily output W of the mining face is 1248t, and the time for installing the mining equipment is... For 1 day, the mining operation rate is a regular cycle. 80%, depth of cut per cut The effective working time T for both tunneling machines A and B is 18 hours per day, and the tunneling cycle advance is 0.6m. The depth is 2.5m, and the excavation time for each cycle is... The support time is 4 hours per cycle. The auxiliary time for each cycle is 3 hours. The time it takes for the tunneling machine to move from the third cut-in 11 to the second return airway 7 is 2 hours. For 2 days; coal density 1.3 g / cm 3 Cohesion of coal body The internal friction angle of the coal is 1.5 MPa. The angle is 37.3°, and the Poisson's ratio of the coal body is... The average unit weight of the overlying strata is 0.2. The basic top thickness is 25 kN / m³. The ultimate tensile strength of the basic top rock is 10m. The resistance of the roadway support is 2.5 MPa. The effective support length of the coal face rock bolts in the upper section of the roadway is 0.2 MPa. It is 1.8m.

[0027] 2) Set the width of the small coal pillar 13 as... ,according to The width of the small coal pillar 13 was calculated. ,in The width of the plastic zone of the coal pillar, in meters; The effective support length of the coal face rock bolts in the upper section of the roadway is given in meters. The safety factor is 0.15-0.35; the formula for calculating the width of the plastic zone of the coal pillar is: ,in b is the width of the plastic zone of the coal pillar, in meters; b is the height of the roadway, in meters. The internal friction angle of the coal; The stress concentration factor is 2-3; Cohesion of coal body, MPa; The resistance of the roadway support is measured in MPa.

[0028] Specifically, the safety factor in this embodiment Take 0.2 as the stress concentration factor. Take 2.5, width of the plastic zone of the coal pillar =5.08m, therefore the width reserved for small coal pillar 13 is... =8.26m.

[0029] 3) Set the width of the large coal pillar 12 as... ,according to The width of the large coal pillar 12 was calculated. ,in The width of the plastic zone on the side of the goaf, and also the width of the plastic zone of the coal pillar, in meters; The width of the plastic zone on the side of the tunnel, in meters; The width of the elastic core; where the formula for calculating the width of the plastic zone on the roadway side is: Where R is the equivalent radius of the tunnel, in meters; in a rectangular tunnel , The width of the alleyway is in meters (m). The tunnel height is in meters (m). The lateral pressure coefficient, , The formula for calculating the Poisson's ratio of the coal body is: .

[0030] Specifically, in this embodiment, the equivalent radius of the tunnel... =0.75m, lateral pressure coefficient =0.25, width of the plastic zone on the side of the roadway =4.07m, elastic core width =12.79m, therefore the width reserved for the large coal pillar 12 is 12.79m. =21.94m.

[0031] 4) According to Calculate the safe distance of the coal pillar unaffected by mining activities at the working face. ,in The basic top thickness is in meters (m). The ultimate tensile strength of the basic top rock is given in MPa. The average unit weight of the overlying rock strata is kN / m³. For mining depth, m.

[0032] Specifically, in this embodiment, the safe distance of the coal pillar unaffected by the working face mining activity =10.49m.

[0033] 5) According to Calculate the tunneling speed of tunneling machine A or tunneling machine B. and Calculate the mining speed of the first working face 1. ;in The advance distance during the tunneling cycle is measured in meters (m). Effective working hours per day, in hours (h); The excavation time for each cycle is in hours (h). The support time for each cycle is in hours (h). Let h be the auxiliary time for each loop; The daily output of the mining face is expressed in tons (t). To improve the efficiency of regular mining operations; The tunnel height is in meters (m). The length of the working surface is in meters (m). Density of coal, g / cm³ 3 ; Let m be the depth of cut for each cut.

[0034] Specifically, in this embodiment, the tunneling speed of tunneling machine A or tunneling machine B... =5m / day, mining speed of the first working face 1 =2.4m / day.

[0035] 6) According to Calculate the time it takes for tunneling machine B to advance from the second return airway 7 to the small coal pillar 13. Where L is the length of the working face, in meters; s is the width difference between the large coal pillar 12 and the small coal pillar 13, in meters; The time taken for the tunneling machine to move from the third cut-in 11 to the second return air roadway 7, in days; The time required to install the mining equipment is in days.

[0036] Specifically, the width difference between the large coal pillar 12 and the small coal pillar 13 The length is 13.68m, therefore the time it takes for tunneling machine B to tunnel from the second return airway 7 to the small coal pillar 13 is... ≈60.5 days.

[0037] 7) According to Calculate the length of the reserved large coal pillar 12.

[0038] Specifically, the length of the large coal pillar 12 is reserved. ≈288.9m.

[0039] 8) According to Calculate the length of the small coal pillar 13 to be reserved.

[0040] Specifically, the length of the small coal pillar 13 is... ≈711.1m.

[0041] Therefore, the width of the large coal pillar 12 is 21.94m, and the length is 288.9m; the width of the small coal pillar 13 is 8.26m, and the length is 711.1m. This clarifies the length and width of the large and small coal pillars 12 and 13, providing clear parameter basis for the mining plan and facilitating subsequent production planning. Compared with traditional methods of using large coal pillars for roadway protection, this invention reduces the amount of coal pillars used, increasing the recovery rate of the working face and increasing profits. Compared with traditional methods of using small coal pillars for roadway protection, this invention significantly reduces the impact of mining on roadway excavation, improving roadway excavation efficiency. Compared with traditional methods of roadway excavation along the goaf, the invention uses a reverse pillar method when using large coal pillars, avoiding the deformation problem caused by "exposing the coal pillar first and then supporting it," thus increasing the stability of the area while ensuring resource conservation.

[0042] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, modifications can still be made to the embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for setting up large and small coal pillars in a goaf return airway along a working face, wherein a first working face (1), a second working face (2) and a third working face (3) are arranged in sequence and adjacent to each other in a parallel longwall working face, a goaf (4) is arranged on the right side of the first working face (1), a first return airway (5) and a first transport roadway (6) are arranged on both sides of the first working face (1), a second return airway (7) and a second transport roadway (8) are arranged on both sides of the second working face (2), the second return airway (7) and the second transport roadway (8) are connected through a second cut (9), a third transport roadway (10) is arranged on one side of the third working face (3), the third transport roadway (10) and the second transport roadway (8) are connected through a third cut (11), a large coal pillar (12) and a small coal pillar (13) are arranged between the first transport roadway (6) and the second return airway (7), and an A heading machine is used to excavate the second transport roadway (8) and the second cut (9), and a B heading machine is used to excavate the third transport roadway (10) and the third cut (11), after the third transport roadway (10) and the third cut (11) are excavated, the B heading machine is moved to the starting point of the second return airway (7) for excavation, the excavation speed of the A heading machine and the B heading machine is the same, characterized in that: Comprising the following steps: 1) determining specific parameters of the working face, the A and B roadheaders and the coal body; 2) the width of the small coal pillar (13) is set as , the width of the small coal pillar (13) is calculated according to , wherein is the width of the plastic zone of the coal pillar, m; is the effective support length of the roof bolt of the upper section roadway, m; is the safety factor, and is 0.15-0.35;​ 3) the width of the large coal pillar (12) is set as , the width of the large coal pillar (12) is calculated according to , wherein is the width of the plastic zone on the goaf side, and is also the width of the plastic zone of the coal pillar, m; is the width of the plastic zone on the roadway side, m; is the width of the elastic core;​ 4) according to Calculating the safety distance of coal pillar not affected by working face mining wherein is the basic roof thickness, m; is the ultimate tensile strength of basic roof rock, MPa; is the average overburden density, kN / m³; is the mining depth, m; 5) according to calculating the driving speed of the A or B heading machine and calculating the mining speed of the first working face (1) ; wherein is the driving cycle footage, m; is the effective working time per day, h; is the driving time per cycle, h; is the support time per cycle, h; is the auxiliary time per cycle, h; is the daily production of the mining working face, t; is the normal cycle operation rate of mining; is the roadway height, m; is the working face length, m; is the coal body density, g / cm 3 ; is the cutting depth per pass, m; 6) according to the time for the B heading machine to advance from the second return air gate (7) to the small coal pillar (13) where L is the length of the strike of the working face, m; s is the width difference between the large coal pillar (12) and the small coal pillar (13), m; is the time for the heading machine to transfer from the third cut (11) to the second return air gate (7), days; is the time for installing the mining equipment, days; 7) according to calculating the length of the large coal pillar (12); 8) according to The length of the small coal pillar (13) is calculated.

2. The method for setting up large and small coal pillars in the return air gateway of the gob-side entry driving of the coal face according to claim 1, characterized in that: During the process of shifting the B roadheader to the starting point of the second return air gateway (7), the mining equipment and the A roadheader continue to operate.

3. The method according to claim 1, characterized in that: The calculation formula of the coal pillar plastic zone width in the step 2) is wherein is the coal pillar plastic zone width, m; b is the roadway height, m; is the internal friction angle of the coal body; is the stress concentration coefficient, is 2-3; is the cohesion of the coal body, MPa; is the roadway support resistance, MPa.

4. The method for setting up large and small coal pillars in the return air gateway of the gob-side entry driving of the coal face according to claim 3, characterized in that: The calculation formula of the plastic zone width of the roadway side in the step 3) is wherein R is the equivalent radius of the roadway, m; in the rectangular roadway , W is the roadway width, m; H is the roadway height, m; Kt is the lateral pressure coefficient, , μ is the Poisson's ratio of the coal body.

5. The method for setting up large and small coal pillars in the return air gateway of the gob-side entry driving of the coal face according to claim 4, characterized in that: The calculation formula of the elastic core width in the step 3) is .

Images