Grouting re-mining method for soft broken residual coal in caving zone of coal goaf

Abstract

The invention discloses a grouting re-mining method for soft broken residual coal in a caving zone of a coal goaf, which comprises the following steps of: respectively digging a re-mining roadway in the direction of residual coal in the goaf from an original rail uphill and an air return uphill, punching, grouting and filling while digging, then digging an open-off cut in the direction from a transportation crossheading to an air return crossheading, drilling holes and grouting in advance in the residual coal to be re-mined and the top plate from the transportation gate road and the air return gate road to ensure that the soft and broken residual coal and the top plate are consolidated into a whole, and performing re-mining operation according to a conventional mining method; the problem of re-mining of the soft broken residual coal in the caving zone of the goaf is solved, and safe and convenient secondary mining of the scrapped mine is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of coal mining, in particular to a method for re-mining soft and broken residual coal in a caving zone of a coal goaf area. Background Art

[0002] Coal, as the primary energy source in my country, will remain a key domestic energy source for a long time to come. Inevitably, coal resources are becoming scarce with continued mining. Consequently, my country has issued the "Interim Regulations on the Management of Recovery Rates in Coal Mines," which set clear recovery rate requirements for mining areas and working faces. The recovery rate standards for underground coal mines are: 85% or greater for seams less than 1.3 meters thick; 80% or greater for seams between 1.3 and 3.5 meters thick; and 75% or greater for seams greater than 3.5 meters thick. However, prior to the issuance of the regulations, these recovery rates were rarely met in order to accelerate mining, leaving a significant amount of residual coal buried underground. Furthermore, in extremely thick seams (over 8 meters), even if 75% is mined, at least 2 meters of coal remains buried underground. This has led to the proposal to mine this buried residual coal, a problem known as remining. But the actual situation is that after one mining, the roof naturally collapses and becomes loose, and the residual coal in the caving zone is soft and broken, with poor stability. This makes it difficult to develop the tunnels of the mining system, especially the support. At the same time, it is also impossible to directly form a stable re-mining working face. Safety problems such as working face spalling and roof leakage may occur, making effective secondary mining impossible.

[0003] Therefore, there is an urgent need for a method for re-mining the soft and broken coal in the caving zone of the goaf to solve the problem of secondary mining of coal energy. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a grouting re-mining method for soft and broken residual coal in the caving zone of a coal goaf.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a grouting re-mining method for soft and broken residual coal in the caving zone of a coal goaf, comprising the following steps:

[0006] The first step is to determine the distribution of soft and broken coal in the caving zone of the goaf based on the information in the mining project plan during the first top coal caving. Based on this distribution, the layout of the secondary mining working face and the specific location of the secondary mining tunnel are planned, and the parameters of the secondary mining tunnel are designed; the secondary mining tunnel includes a transport chute, a return air chute and a cutting eye.

[0007] The second step is to excavate secondary mining tunnels from the original track uphill and return air uphill protection coal pillars in the direction of the goaf. When the excavation is 3 to 5 meters away from the original production stop line (i.e., the coal pillar boundary line), the residual coal area in front of the excavation is drilled and grouting is carried out. The filling depth is 10 to 15 meters, and the filling cross-sectional size is larger than the cross-sectional size of the secondary mining tunnel. After the slurry solidifies into a whole, the excavation is continued. When the excavation is 3 to 5 meters away from the boundary of the grouting consolidation area, the residual coal area in front is drilled and grouting is carried out again. This process is repeated until the transport chute and return air chute are excavated.

[0008] Then, the cutting eye is excavated from the transport chute toward the return air chute. The excavation is carried out according to the above-mentioned drilling and grouting filling method, that is, drilling and grouting are first performed, and then excavation is carried out until the transport chute and the return air chute are opened up to form the cutting eye.

[0009] The third step is to drill holes and inject grout into the coal and roof to be mined from the above-mentioned transport chute and return air chute. The spacing and depth of the holes are determined according to the specific conditions of the coal and roof to ensure that the soft and broken coal and roof are consolidated into a whole. If necessary, drill a core drill to check the grouting situation and add grouting to the areas that are not fully filled.

[0010] The fourth step is to arrange the mining equipment of the re-mining working face after the soft and broken residual coal and the roof are consolidated into a whole, and carry out re-mining operations according to conventional mining methods.

[0011] Furthermore, the excavation of the transport chute, return air chute and cutting eye in the above second step can also be carried out in the order of transport chute - cutting eye - return air chute; that is, first excavate the transport chute from the original track uphill toward the direction of the coal left in the goaf, then excavate the cutting eye from the transport chute toward the return air chute, and then excavate the return air chute from the cutting eye toward the return air uphill direction.

[0012] Furthermore, during the drilling and grouting in the second step, quick-setting agents such as water glass can be added to the cement grouting liquid to quickly solidify the excavation front into a whole, thereby ensuring close and continuous operation of drilling and grouting and tunnel excavation.

[0013] Furthermore, in order to place the re-mining tunnel in a stable surrounding rock, during the drilling and grouting filling in the above second step, the elevation angle of the upper hole is 15°~20°, the elevation angle of the lower hole is 0°~5°, and the outward angle is 15°~20°, to ensure that the top and both sides of the re-mining tunnel have a filling thickness of at least 2 meters.

[0014] Furthermore, in the third step mentioned above, when drilling and grouting are carried out in the residual coal and roof to be mined again, multiple work groups may work simultaneously to improve the work progress.

[0015] Furthermore, the drilling and grouting filling in the third step and the re-mining work in the fourth step can also be carried out simultaneously, starting from one end of the working face of the re-mining tunnel, and performing backward grouting operations. After the front grouting is solidified, re-mining can be started. Re-mining can be carried out after the front grouting, and the operation speed should be kept consistent until the re-mining is completed.

[0016] Furthermore, when drilling and grouting in the third step, the effective depth of the grouting hole shall not be less than half of the length of the working surface, ensuring that the grouting holes of the transport chute and the return air chute are connected to each other.

[0017] The method of the present invention has the following beneficial effects compared to the prior art:

[0018] 1. Before tunnel excavation, advance grouting is used to solidify the filling into a whole, ensuring that the tunnel is excavated in the solidified filling body, solving the problems of tunnel stability and surrounding rock control.

[0019] 2. Before mining the working face, grouting is pre-injected into the soft and broken coal seam and roof to solidify them into a whole, which solves the problem of spalling and roof leakage on the working face and ensures safe and efficient re-mining.

[0020] To sum up, the present invention solves the problem of re-mining of soft and broken coal in the caving zone of the goaf, realizes the safe and convenient secondary mining of abandoned mines, improves the resource recovery rate, and extends the service life of the mine, which can realize the sustainable development of the mining area and has broad promotion prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. The drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 This is a schematic diagram of the initial stage of excavation of the secondary mining tunnel in Example 1;

[0023] Figure 2 This is a mid-term schematic diagram of the secondary mining tunnel excavation in Example 1;

[0024] Figure 3 This is a schematic diagram of the eye opening excavation in Example 1;

[0025] Figure 4 Schematic diagram of advanced drilling and grouting from the secondary mining roadway to the residual coal in Example 1;

[0026] Figure 5 This is a schematic diagram of the grouting status and re-mining direction of the re-mining working face in Example 1;

[0027] Figure 6This is a schematic diagram of the arrangement of grouting holes during excavation of a secondary mining tunnel in Example 1;

[0028] Figure 7 for Figure 6 A top view of

[0029] Figure 8 Schematic diagram of the excavation sequence of the secondary mining tunnel in Example 2.

[0030] In the figure: 1. Track uphill, 2. Return air uphill, 3. Coal pillar protecting the tunnel, 4. Original shutdown line, 5. Remaining coal area, 6. Grouting consolidation area for protecting the tunnel, 7. Transport drift, 8. Return air drift, 9. Open cut, 10. Grouting hole, 11. Grouting consolidation area of ​​caving zone, 12. Re-mining tunnel, 13. Remaining coal, 14. Empty roof area of ​​caving zone. DETAILED DESCRIPTION

[0031] The embodiments of the present invention are described in detail below with reference to the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more precise definition of the protection scope of the present invention.

[0032] A coal seam in a certain mine, originally 9m thick, was mined for the first time using top coal caving, with a mining height of 3m and a caving height of 3.5m. The remaining 3m of coal within the caving zone fell into the goaf and remained unmined. The remaining coal was soft and broken, making it unminable using conventional methods. To safely mine the remaining coal, the following example was developed.

[0033] Example 1

[0034] A grouting and re-mining method for soft and broken residual coal in a caving zone of a coal goaf specifically comprises the following steps:

[0035] Step 1: Based on the information of the initial mining in the mining project plan and the distribution of soft and broken coal in the caving zone of the goaf, the layout of the secondary mining working face and secondary mining roadway are designed as follows:

[0036] 1. Design of the size and position of the secondary mining roadway: The designed secondary mining roadway 12 includes a transport chute 7 and a return air chute 8. The design is based on the thickness of the residual coal, the belt transport capacity in the transport chute and the ventilation volume of the return air chute. The designed transport chute 7 and return air chute 8 have a rectangular cross-section, a roadway cross-section width of 3 meters, a height of 2.5 meters, and a total length of 1,800 meters. All of them are developed in the residual coal. The transport chute 7 and return air chute 8 are developed from the original track uphill 1 and return air uphill 2 respectively towards the residual coal area 5; 2. According to the commonly used coal mining process, the designed cutting eye length is 200 meters, the width is 3 meters, and the height is 3 meters.

[0037] Step 2: If Figure 1According to the size and position of the secondary mining tunnel designed in step 1, secondary mining tunnels 12 are excavated from the coal pillars 3 of the track uphill 1 and the return air uphill 2 respectively toward the coal-residing area 5. The secondary mining tunnel 12 includes a transport chute 7 and a return air chute 8. When it is three to five meters away from the original shutdown line 4 (i.e., the coal pillar boundary line), grouting holes 10 are drilled in advance for grouting and filling.

[0038] like Figure 6 、 7 As shown, when drilling the grouting hole 10, the grouting filling depth H must be ensured to be 10-15 meters; the drilling angle must ensure that the elevation angle a of the upper grouting hole is 15-20°, the elevation angle b of the lower grouting hole is 0-5°, and the outward angle c is 15-20°, so that there is at least a filling thickness of H=2 meters around the secondary mining tunnel, forming a tunnel protection grouting consolidation area 6, and the secondary mining tunnel is in a stable surrounding rock.

[0039] like Figure 2 After the slurry solidifies into a whole, continue excavating forward. When the excavation is 3-5 meters away from the boundary of the grouting consolidation zone, drill holes and inject grout into the area ahead. Repeat this process until the transport chute 7 and the return air chute 8 are excavated. To ensure that the drilling and grouting and the roadway excavation are carried out closely and continuously, a quick-setting agent such as water glass can be added to the cement grouting liquid to quickly solidify the excavation front into a whole.

[0040] Step 3: If Figure 3 Then, a cutting eye 9 is excavated from the transport chute 7 toward the return air chute 8. The excavation is carried out according to the grouting filling method in the second step until the transport chute 7 and the return air chute 8 are opened up to form a cutting eye 9, and the mining equipment of the secondary mining working face is arranged.

[0041] Step 3: Step 4: As Figure 4 At the same time, grouting holes 10 are drilled in advance from the above-mentioned transport chute 7 and return air chute 8 into the residual coal 13 to be mined again and the empty top area 14 of the caving zone, and the grouting consolidation area 11 of the caving zone is formed after grouting; the spacing, number and depth of the drilling holes are determined by the actual residual coal situation and the diffusion of the grouting liquid to ensure that the soft and broken residual coal 13 and the empty top area 14 of the caving zone are consolidated into a whole. If necessary, drill a core drill to check the grouting situation and perform additional grouting on the unfilled areas.

[0042] Step 4: After the coal residue area 5 is consolidated into a whole, a Figure 5 The re-mining working face shown as available for mining can be used for re-mining work.

[0043] Example 2

[0044] like Figure 8As shown, Example 2 is the same as Steps 1, 3, and 4 of Example 1. In Step 2, when excavating the secondary mining roadway, excavation is carried out in the order of transport chute, cut hole, and return air chute. That is, first, a transport chute 7 is excavated from the original track uphill 1 toward the coal residue in the goaf. Then, a cut hole 9 is excavated from the transport chute 7 toward the return air chute 8. Finally, a return air chute is excavated from the cut hole 9 toward the return air uphill 2.

[0045] Example 3

[0046] The steps of Example 3 are basically the same as those of Examples 1 and 2, except that during the drilling and grouting in Step 3, multiple groups work simultaneously to improve the work progress.

[0047] Example 4

[0048] The steps of Example 4 are basically the same as those of Examples 1 and 2, except that the advance grouting of the caving zone in Step 3 and the re-mining in Step 4 are carried out simultaneously; backward grouting operation is first started from one side of the working face, and re-mining can be started after the front grouting is solidified. Re-mining is carried out after the front grouting, and the operation speed is kept consistent until the re-mining is completed.

[0049] Several embodiments have been described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. Various changes made by technicians in the relevant field without departing from the idea and scope of the present invention are all within the scope of protection of the claims of the present invention.

Claims

1. A grouting and re-mining method for soft and broken coal in the caving zone of coal goaf, characterized in that: The following steps are involved: The first step is to determine the distribution of soft and broken coal in the caving zone of the goaf, plan the layout of the secondary mining working face and the specific location of the secondary mining tunnel, and design the cross-sectional dimensions of the secondary mining tunnel; The second step is to excavate a transport chute and a return air chute from the original track uphill and return air uphill coal pillars towards the goaf coal residue, and then excavate a cut hole from the transport chute towards the return air chute. When excavating the transport chute, return air chute and cut hole, the broken coal residue area in front is first drilled and grouting is carried out. After the slurry solidifies into a whole, excavation continues. The third step is to advance drilling and grouting from the above-mentioned transport chute and return air chute into the residual coal and roof to be mined, so as to ensure that the soft and broken residual coal and roof are consolidated into a whole; The fourth step is to wait until the soft and broken residual coal and the roof are consolidated into a whole, and then carry out re-mining operations according to conventional mining methods.

2. The grouting re-mining method for soft and broken coal in the caving zone of a coal goaf according to claim 1, characterized in that: In the second step, the excavation sequence of the transport chute, return air chute and cutting eye is replaced by the following sequence: transport chute - cutting eye - return air chute in this order, that is: first excavate the transport chute from the original track uphill toward the direction of the coal residue in the goaf, then excavate the cutting eye from the transport chute toward the return air chute, and then excavate the return air chute from the cutting eye toward the direction of the return air uphill.

3. The grouting re-mining method for soft and broken coal in the caving zone of a coal goaf according to claim 1, characterized in that: In the third step, when drilling and grouting are carried out into the re-mined coal and roof, multiple work groups work simultaneously.

4. The grouting re-mining method for soft and broken coal in the caving zone of a coal goaf according to claim 1, characterized in that: The third step of drilling and grouting filling operation and the fourth step of re-mining operation are carried out synchronously: that is, the grouting operation is started from one end of the working face of the re-mining tunnel, and the re-mining operation can be started after the front grouting is solidified. The re-mining operation is carried out after the front grouting, and the operation speed is kept consistent until the re-mining is completed.

5. A grouting re-mining method for soft and broken coal in the caving zone of a coal goaf according to any one of claims 1 to 4, characterized in that: In the second step, drilling and grouting filling are carried out in the residual coal crushing area in front of the excavation, starting from 3 to 5 meters away from the residual coal crushing area. The depth of each grouting filling is 10 to 15 meters, and the cross-sectional size of the grouting filling is larger than the cross-sectional size of the re-mining tunnel.

6. A grouting re-mining method for soft and broken coal in the caving zone of a coal goaf according to any one of claims 1 to 4, characterized in that: During the drilling and grouting filling in the second step, an accelerator is added to the cement grouting liquid.

7. A grouting re-mining method for soft and broken coal in the caving zone of a coal goaf according to any one of claims 1 to 4, characterized in that: During the second step of drilling and grouting, the elevation angle of the upper hole is 15 to 20 degrees, the elevation angle of the lower hole is 0 to 5 degrees, and the outward angle is 15 to 20 degrees.

8. A grouting re-mining method for soft and broken coal in the caving zone of a coal goaf as described in claims 1-4, characterized in that: The effective depth of the grouting holes in the third step shall not be less than half the length of the working surface.

9. A grouting re-mining method for soft and broken coal in the caving zone of a coal goaf as claimed in claim 5, characterized in that: The cross-sectional size of the grouting filling is larger than the cross-sectional size of the secondary mining tunnel in order to ensure that the top and both sides of the secondary mining tunnel have a thickness of at least 2 meters.

10. A grouting re-mining method for soft and broken coal in the caving zone of a coal goaf according to claim 6, characterized in that: The quick-setting agent is water glass.

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