CN117307168A - Roof cutting and pressure relief method for long-distance coal seam reserved roadway - Google Patents

Abstract

The invention discloses a roof cutting and pressure relief method for a long-distance coal seam reserved roadway, and relates to the fields of mining engineering and blasting engineering. The roof suspension of the goaf formed at early stage can be blasted and relieved in advance in the coal seam mining process, so that roof collapse in the coal seam mining process is facilitated, and various potential safety hazards caused by overlarge length of the roof suspension of the coal seam mining are avoided. The roof cutting and pressure relief method comprises the following steps: in the back stoping process of the upper coal seam, a blasting special lane parallel to the upper coal seam cutting hole is dug in front of the upper coal seam cutting hole, a plurality of blasting drilling holes pointing to the lower coal seam cutting hole are formed in the blasting special lane, after the upper coal seam is mined backwards, and the lower coal seam is stoped backwards for a certain distance to form a goaf, explosive is filled in the blasting drilling holes and detonated, and roof cutting pressure relief of the goaf of the lower coal seam is achieved. The technical purpose of roof cutting and pressure relief of partial goaf in advance during stoping of the lower coal seam is achieved.

Description

A method of roof cutting and pressure relief for reserved tunnels in long-distance coal seams

Technical field

The invention relates to the fields of mining engineering and blasting engineering, and specifically designs a method for performing long-distance coal seam roof cutting and pressure relief using reserved tunnels.

Background technique

With the continuous depletion of shallow and easy-to-mine coal resources in our country, the mining of some difficult-to-mine coal resources has gradually been paid attention to. Coal companies need to try their best to mine all coal resources underground. Due to the different coal-forming ages of the coal seams, the spatial location between the upper and lower coal seams is more complex. In some cases, the distance between the upper and lower coal seams is far away and the lithology of the middle rock layer is relatively hard. The length of the suspended roof for mining of the lower coal seams is too long. It is large and threatens the safe mining of the working face.

The traditional top-cut pressure relief blasting or hydraulic fracturing method has complex charging methods, long construction period, and it is difficult to guarantee the blasting effect and safety. After the roof is broken, it will also have a great impact on the safe production of the working surface. At present, the methods to solve the problem of large-area suspended roofs in lower coal seams in remote coal seam mining are relatively complex and require a long construction period. Therefore, there is an urgent need to propose a method that can quickly and effectively solve the problem of large-area suspended roofs of hard roofs in remote coal seams.

Contents of the invention

In view of the above problems, the present invention proposes a roof cutting and pressure relief method for long-distance coal seam reserved tunnels. During the mining process of the lower coal seam, the suspended roof forming the early goaf area can be blasted and pressure relieved in advance to facilitate the mining process of the lower coal seam. The roof in the coal seam will collapse to avoid various safety hazards caused by the excessive length of the suspended roof in the lower coal seam mining.

The technical solution of the present invention is: the top cutting and pressure relief method is:

During the backward mining process of the upper coal seam, a special blasting alley parallel to the upper coal seam cutout is excavated in front of the upper coal seam cutout, and a number of blasting boreholes pointing to the lower coal seam cutout are opened in the special blasting alley, waiting for After the upper coal seam is mined backwards and the lower coal seam is also mined back a certain distance to form a goaf, explosives are loaded into the blasting borehole and detonated to achieve roof cutting and pressure relief in the goaf of the lower coal seam.

Based on the top cutting and pressure relief method, the mining of the upper coal seam and lower coal seam is carried out according to the following steps:

Step 1. Cut holes in the upper coal seam and mine the upper coal seam backward;

Step 2. While waiting for the upper coal seam to be mined backwards, excavate a special tunnel for blasting in front of the upper coal seam cutout position, so that a protective coal pillar is formed between the upper coal seam cutout and the special blasting tunnel;

Step 3. In the special tunnel for excavation and blasting, open a number of blasting boreholes that point downward to cut holes in the coal seam, and fill the blasting boreholes with explosives;

Step 4: After all the upper coal seams have been mined, open a cut hole in the lower coal seam and mine part of the lower coal seam backward; the lower coal seam cut hole is in front of the upper coal seam cut hole, and there is a horizontal offset distance between the two;

Step 5. Arrange a dust-proof net above the goaf formed after the mining of part of the lower coal seam, and arrange temporary support in front of the lower coal seam to be mined, and then detonate explosives to make the upper part of the goaf formed after the mining of the lower coal seam The roof collapses to achieve roof cutting and pressure relief;

Step 6: Continue from the temporary support position backward to complete the mining of the remaining part of the lower coal seam.

Further, the horizontal offset distance between the upper coal seam cutting hole and the lower coal seam cutting hole, and the width of the protective coal pillar between the upper coal seam cutting hole and the blasting tunnel are predetermined according to the following method:

Arrange boreholes evenly in the overlying rock of the required roof cutting working face, use the drill core sampling method to obtain overlying rock samples and rock formation depth information, and use numerical simulation software to build a mining fracture model for the overlying rock in the working face, and design the upper coal seam , Mining simulation of cutting holes in lower coal seams at different staggered distances;

After the mining simulation, FLAC3D software was used to establish a numerical simulation model, design the width dimensions and roof cutting parameters of the protected coal pillars, and analyze the stability of protected coal pillars of different widths and the pressure relief effect of roof cutting.

Further, several blasting boreholes are evenly distributed in the special blasting lane, the distance between the end point of the blasting boreholes and the opening of the lower coal seam is less than 10m, and the radius of the blasting boreholes is 60-100mm;

The distance A between adjacent blasting holes is:

Among them, A is the blasting borehole spacing; t is the uniaxial tensile strength of the rock; P2 is the initial peak pressure of the blasting borehole wall; ρ is the explosive density, D is the explosive detonation velocity; σ is the tensile strength of the roof rock layer; μ is Poisson's ratio; α is the attenuation index of the stress wave peak value in the rock body; r ₁ is the diameter of the charge roll, and r ₂ is the diameter of the blast hole.

During the mining process of the upper coal seam, the invention first excavates a special tunnel for blasting and a plurality of blasting boreholes. In this way, after waiting for the lower coal seam to be mined backward for a certain distance to form a goaf, explosives can be loaded into the blasting boreholes and detonated. Realize roof cutting and pressure relief in the goaf area of lower coal seam. In view of the fact that the distance between the upper and lower coal seams is relatively long and the lithology of the middle rock layer is relatively hard, the technical purpose of first cutting the roof and depressurizing part of the goaf area during the mining of the lower coal seam is achieved to avoid the overhang of the coal seam. The top length is too large, which threatens the safe mining of the lower coal seam.

Description of drawings

Figure 1 is a schematic diagram of the mining process in this case.

Figure 2 is a schematic diagram of the mining process in this case.

Figure 3 is a schematic diagram of the mining process in this case.

Figure 4 is a schematic diagram of the mining process in this case.

Figure 5 is a schematic diagram of the mining process in this case.

Figure 6 is a schematic diagram of the mining process in this case.

Detailed ways

In order to clearly explain the technical features of this patent, this patent will be elaborated in detail below through specific implementation modes and in conjunction with the accompanying drawings.

Taking a coal mine as an example, the vertical distance between the upper and lower coal seams is 100m, and there are rock layers of sandstone and mudstone in the middle. After the mining of the upper coal seam is completed, a huge thick roof will be formed between the two layers of coal. The initial mining of the lower coal seam Moving roadway support poses a danger, so a roof cutting and pressure relief method for long-distance coal seam reserved roadways according to the present invention is adopted, and is explained with reference to the accompanying drawings.

The horizontal distance between the upper coal seam cutting hole and the lower coal seam cutting hole, that is, the horizontal staggered distance is simulated as 0m, 5m, 10m, 15m, 20m, 30m, and the distance between the special blasting tunnel and the upper coal seam cutting hole is The coal pillar widths are simulated as 2.5m, 5m, 7.5m, 10m, 12.5m, and 15m.

Arrange boreholes evenly in the overlying rock of the required roof cutting working face, use the drill core sampling method to obtain overlying rock samples and rock formation depth information, and use numerical simulation software to build a mining fracture model for the overlying rock in the working face, and design the upper coal seam , Mining simulation of cutting holes in lower coal seams at different staggered distances;

After the mining simulation, FLAC3D software was used to establish a numerical simulation model, design the width dimensions and roof cutting parameters of the protected coal pillars, and analyze the stability of protected coal pillars of different widths and the pressure relief effect of roof cutting.

The results show that the horizontal staggered distance of the upper and lower coal seam cutting holes is 20m, and the protective coal pillar width between the blasting tunnel and the upper coal seam cutting hole is 10m, which has the best roof cutting effect and coal pillar stability.

After that, the upper coal seam and the lower coal seam are mined:

Step 1. As shown in Figure 1, cut a hole in the upper coal seam and mine the upper coal seam backward;

Step 2. As shown in Figure 1, while waiting for the upper coal seam to be mined backwards, excavate a special tunnel for blasting in front of the upper coal seam cutting position, so that a protective coal pillar is formed between the upper coal seam cutting hole and the special blasting tunnel;

Step 3. As shown in Figures 2 and 3, open a number of blasting boreholes pointing downward into the coal seam in the special tunnel for excavation and blasting, and fill the blasting boreholes with explosives;

Step 4. As shown in Figure 4, after all the upper coal seams have been mined, a cut hole in the lower coal seam is opened to mine part of the lower coal seam backward; the cut hole in the lower coal seam is in front of the cut hole in the upper coal seam, and there is a gap between the two. Horizontal offset distance;

Step 5. As shown in Figure 5, arrange a dustproof net above the goaf formed after the mining of part of the lower coal seam, and arrange temporary support in front of the lower coal seam to be mined, and then detonate explosives to make the lower coal seam The roof above the formed goaf collapses, as shown in Figure 6, achieving roof cutting and pressure relief;

Step 6: Continue from the temporary support position backward to complete the mining of the remaining part of the lower coal seam.

There are many ways to implement the present invention, and the above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, several improvements can be made without departing from the principles of the present invention. These improvements Improvements should also be considered as the protection scope of the present invention.

Claims (4)

1. A method of roof cutting and pressure relief for reserved tunnels in long-distance coal seams, characterized in that the roof cutting and pressure relief method is: During the backward mining process of the upper coal seam, a special blasting alley parallel to the upper coal seam cutout is excavated in front of the upper coal seam cutout, and a number of blasting boreholes pointing to the lower coal seam cutout are opened in the special blasting alley, waiting for After the upper coal seam is mined backwards and the lower coal seam is also mined back a certain distance to form a goaf, explosives are loaded into the blasting borehole and detonated to achieve roof cutting and pressure relief in the goaf of the lower coal seam. 2. A method of roof cutting and pressure relief for long-distance coal seam reserved tunnels according to claim 1, characterized in that, based on the roof cutting and pressure relief method, the mining of the upper coal seam and the lower coal seam is carried out according to the following steps: Step 1. Cut holes in the upper coal seam and mine the upper coal seam backward; Step 2. While waiting for the upper coal seam to be mined backwards, excavate a special tunnel for blasting in front of the upper coal seam cutout position, so that a protective coal pillar is formed between the upper coal seam cutout and the special blasting tunnel; Step 3. In the special tunnel for excavation and blasting, open a number of blasting boreholes that point downward to cut holes in the coal seam, and fill the blasting boreholes with explosives; Step 4: After all the upper coal seams have been mined, open a cut hole in the lower coal seam and mine part of the lower coal seam backward; the lower coal seam cut hole is in front of the upper coal seam cut hole, and there is a horizontal offset distance between the two; Step 5. Arrange a dust-proof net above the goaf formed after the mining of part of the lower coal seam, and arrange temporary support in front of the lower coal seam to be mined, and then detonate explosives to make the upper part of the goaf formed after the mining of the lower coal seam The roof collapses to achieve roof cutting and pressure relief; Step 6: Continue from the temporary support position backward to complete the mining of the remaining part of the lower coal seam. 3. A method for roof cutting and pressure relief of reserved long-distance coal seam tunnels according to claim 1, characterized in that the horizontal offset distance between the upper coal seam cutting eye and the lower coal seam cutting eye, and The width of the protective coal pillar between the upper coal seam opening and the blasting tunnel is predetermined according to the following method: Arrange boreholes evenly in the overlying rock of the required roof cutting working face, use the drill core sampling method to obtain overlying rock samples and rock formation depth information, and use numerical simulation software to build a mining fracture model for the overlying rock in the working face, and design the upper coal seam , Mining simulation of cutting holes in lower coal seams at different staggered distances; After the mining simulation, FLAC3D software was used to establish a numerical simulation model, design the width dimensions and roof cutting parameters of the protected coal pillars, and analyze the stability of protected coal pillars of different widths and the pressure relief effect of roof cutting. 4. A method for roof cutting and pressure relief of reserved tunnels in long-distance coal seams according to claim 1, characterized in that a number of blasting boreholes are evenly distributed in the dedicated blasting lanes, and the end points of the blasting boreholes are connected to the bottom of the blasting tunnel. The distance between coal seam openings is less than 10m, and the radius of blasting drilling is 60-100mm; The distance A between adjacent blasting holes is: Among them, A is the blasting borehole spacing; t is the uniaxial tensile strength of the rock; P2 is the initial peak pressure of the blasting borehole wall; ρ is the explosive density, D is the explosive detonation velocity; σ is the tensile strength of the roof rock layer; μ is Poisson's ratio; α is the attenuation index of the stress wave peak value in the rock body; r ₁ is the diameter of the charge roll, and r ₂ is the diameter of the blast hole.