A stress control and tunnel protection method for pre-grouting reinforcement of tunnels on a stopped mining line

Abstract

The present invention belongs to the field of surrounding rock stability control technology, and specifically relates to a stress control and tunnel protection method for pre-grouting reinforcement of a stop-mining line tunnel, comprising: excavating a new tunnel between the stop-mining line of the working face and the protected main tunnel; constructing multiple groups of grouting holes on both sides of the new tunnel; injecting ultrafine cement slurry into the surrounding rocks on both sides through the grouting holes to form a corresponding surrounding rock grouting reinforcement range; after the working face advances to the stop-mining line, a support withdrawal channel is formed, and the top and side surrounding rocks of the support withdrawal channel are all within the grouting reinforcement range. The present invention simultaneously reinforces the stop-mining line support withdrawal channel and the main tunnel protective coal pillar, and the bearing capacity of the coal pillar is enhanced, which can effectively support the overlying rock layer and avoid the transfer of mining stress caused by the crushing of the coal pillar; on the other hand, the newly excavated tunnel absorbs a considerable amount of energy through its own deformation, which plays a pressure relief role. By combining pressure control and pressure relief, stress regulation is achieved, thereby playing a protective role for the main tunnel.

Description

Technical Field

[0001] The invention belongs to the technical field of surrounding rock stability control, and in particular relates to a stress control and tunnel protection method for pre-grouting reinforcement of a tunnel driven by a stopped mining line. Background Art

[0002] Long-arm mining is currently the primary method of coal mining in my country. Under this mining model, large tunnels in the panel area must serve multiple working faces. Mining stresses, particularly advanced support stresses, significantly impact the stability of these tunnels. Under these advanced support stresses, the surrounding rock undergoes multiple stress redistributions, leading to a continuous deterioration in the stress environment and bearing capacity, and an increasing risk of instability.

[0003] While the adverse effects on the main tunnel can be mitigated by leaving wider protective coal pillars, this can easily lead to a waste of coal resources. Furthermore, the coal pillars suffer compressive failure under the action of advanced support stress, significantly reducing their bearing capacity. This in turn causes the peak point of advanced support stress to shift toward the main tunnel, seriously threatening the safety and stability of the surrounding rock. With the increasing depletion of coal resources, effectively addressing the problem of mining-induced stress transfer and ensuring the basic stability of the tunnel surrounding rock without increasing the size of the coal pillars remains a pressing technical challenge. Summary of the Invention

[0004] In response to the problems existing in the above-mentioned prior art, the present invention discloses a stress control and tunnel protection method for pre-grouting reinforcement of a roadway on a stop-mining line. Through the roadway pre-grouting reinforcement process, stress control of the surrounding rock of the large roadway is achieved, and the following technical solutions are specifically disclosed:

[0005] A method for protecting a tunnel by stress regulation and pre-grouting reinforcement of a tunnel driven by a stopped mining line, comprising the following steps:

[0006] S01. Excavate a new tunnel between the working face stop line and the protected main tunnel;

[0007] S02. Construct three groups of grouting holes on both sides of the newly excavated roadway. On the mining side, construct Group I, Group II, and Group III holes, respectively, from top to bottom. On the main roadway side, construct Group I, Group II, and Group III holes, respectively, from top to bottom.

[0008] S03. Install the borehole pipe and spray concrete across the entire section of the newly excavated roadway to seal the surrounding rock and prevent grouting from leaking out during grouting.

[0009] S04. Inject ultrafine cement slurry into the surrounding rocks on both sides through the orifice pipe to form a corresponding surrounding rock grouting reinforcement area;

[0010] S05. After the working face advances to the stop-mining line, a support withdrawal channel is formed, and the top and side surrounding rocks of the support withdrawal channel are within the grouting reinforcement range.

[0011] Furthermore, the three groups of grouting holes in S02 are distributed radially along the two sides of the newly excavated tunnel.

[0012] Furthermore, the final hole positions of the group I holes and the group II holes on the mining side in S02 are located 1500mm to 3000mm above the coal seam roof, ensuring effective reinforcement of the coal seam roof and the coal-rock contact surface. At the same time, the final hole positions of the group II holes and the group III holes on the mining side exceed the stop-mining line and are located at the tail of the coal mining hydraulic support, so as to achieve pre-reinforcement of the surrounding rock of the support withdrawal channel after mining is stopped.

[0013] Furthermore, the final hole position of Group I holes on the side of the S02 middle tunnel is located 1500mm to 3000mm above the coal seam roof, ensuring effective reinforcement of the coal seam roof and the coal-rock contact surface.

[0014] Furthermore, the water-cement ratio of the ultrafine cement slurry used in grouting in S04 is controlled at 0.8 ～ 1.2, add 1% of the cement dosage of dispersant, and prepare the slurry through a high-speed mixer to ensure that the slurry can fully penetrate into the cracks of the surrounding rock.

[0015] Furthermore, the grouting pressure at the bottom of the grouting holes on the side of the main tunnel in S04 is controlled at 3MPa~5MPa to prevent slurry from invading the main tunnel; the grouting pressure at the bottom of the group I holes on the mining side is controlled at 5MPa~8MPa, and the grouting pressure at the bottom of the group II holes and the group III holes on the mining side is controlled at 8MPa~10MPa.

[0016] Compared with the prior art, the present invention has the following beneficial effects: the present invention adopts a tunneling pre-grouting reinforcement process, a new tunnel is excavated in the stop-mining line protection coal pillar, grouting is carried out on the coal seams and roof on both sides, and construction is carried out in the mining influence area to effectively reduce the safety risk. After the tunneling pre-grouting is completed, on the one hand, the stop-mining line support withdrawal channel and the main tunnel protection coal pillar are reinforced at the same time, the bearing capacity of the coal pillar is enhanced, and it can effectively support the overlying rock strata, avoid the mining stress transfer caused by the crushing of the coal pillar, and reduce the stress disturbance to the main tunnel; on the other hand, since the newly excavated tunnel is closer to the stress peak point than the protected main tunnel, it absorbs a considerable part of the energy through its own deformation, reduces the stress concentration of the surrounding rock of the main tunnel, and plays a pressure relief role. By combining pressure control and pressure relief, the stress state of the surrounding rock of the protected tunnel is improved. Therefore, the tunneling pre-grouting process of the present invention realizes the stress regulation of the surrounding rock of the main tunnel, thereby improving the stress environment of the surrounding rock of the main tunnel and playing a role in protecting the main tunnel. The present invention is simple to operate, economical and reasonable, and has certain promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a cross-sectional view of the drilling arrangement for pre-grouting in the tunnel;

[0018] Figure 2 This is a schematic diagram of the working face after mining is stopped;

[0019] Figure 3 This is a schematic diagram of the stress transfer process of the advance support when the present invention is not implemented;

[0020] Figure 4 It is a schematic diagram of the stress distribution of the advance support after the implementation of the present invention.

[0021] Among them, 1-protected main tunnel; 2-stop mining line; 3-newly excavated tunnel; 4-Group I holes on the mining side; 5-Group II holes on the mining side; 6-Group III holes on the mining side; 7-Group I holes on the tunnel side; 8-Group II holes on the tunnel side; 9-Group III holes on the tunnel side; 10-concrete; 11-grouting reinforcement range; 12-support removal channel; 13-hydraulic support; 14-initial advance support stress; 15-support stress after transfer; 16-support stress after pre-grouting. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] Example 1

[0024] Reference Figure 1-2 This embodiment discloses a stress control and tunnel protection method for pre-grouting reinforcement of a tunnel on a stop-mining line, comprising the following steps:

[0025] S01. Excavate a new tunnel 3 between the working face stop line 2 and the protected main tunnel 1;

[0026] S02. Construct three groups of grouting holes on both sides of the newly excavated roadway 3. The three groups of grouting holes are radially distributed along both sides of the newly excavated roadway 3. On the mining side, from top to bottom, the three groups of holes are arranged in order: Group I holes 4, Group II holes 5, and Group III holes 6. On the main roadway side, the three groups of holes are arranged in order, from top to bottom: Group I holes 7, Group II holes 8, and Group III holes 9.

[0027] S03 installation of the orifice pipe, and the new tunnel 3 construction full section shotcrete 10, closed surrounding rock to prevent grouting slurry exposure;

[0028] S04. Inject ultrafine cement slurry into the surrounding rocks on both sides through the orifice pipe to form the corresponding surrounding rock grouting reinforcement range 11. The water-cement ratio of the ultrafine cement slurry is controlled at 0.8 ～1.2, add a dispersant with a cement dosage of 1%, and prepare the slurry by a high-speed mixer at the same time to ensure that the slurry can fully penetrate into the surrounding rock cracks. The grouting pressure should be determined according to the reinforcement depth, surrounding rock characteristics, ground stress, etc. The grouting pressure on the main tunnel side should not be too high. In this embodiment, the grouting pressure at the bottom of the grouting hole is controlled at 3MPa~5MPa to prevent the slurry from invading the main tunnel; the grouting pressure on the mining side should be appropriately increased to ensure that the slurry is fully split and penetrated. In this embodiment, the grouting pressure of the mining side group I hole 4 is controlled at 5MPa~8MPa, and the grouting pressure at the bottom of the mining side group II hole 5 and the mining side group III hole 6 is controlled at 8MPa~10MPa;

[0029] S05. After the working face advances to the stop-mining line 2, a support withdrawal channel 12 is formed, and the top and side surrounding rocks of the support withdrawal channel 12 are both within the grouting reinforcement range 11.

[0030] As a preferred embodiment of the present invention, the final hole positions of the mining side group I hole 4 and the mining side group II hole 5 in S02 are located 1500mm to 3000mm above the coal seam roof, ensuring effective reinforcement of the coal seam roof and the coal-rock contact surface. At the same time, the final hole positions of the mining side group II hole 5 and the mining side group III hole 6 exceed the stop-mining line and are located at the tail end of the coal mining hydraulic support 13, so as to achieve pre-reinforcement of the surrounding rock of the support withdrawal channel 12 after stopping mining.

[0031] The final hole position of group 7 holes on the side of the S02 medium and large tunnel is located 1500mm to 3000mm above the coal seam roof, ensuring effective reinforcement of the coal seam roof and the coal-rock contact surface.

[0032] like Figure 3 As shown, before the implementation of the present invention, after the working face stops mining, an initial advance support stress 14 is formed in front of the coal mining face, and as the coal wall is compressed and damaged, the advance support pressure 14 is transferred to the deep to form a transferred support stress 15. The peak point of the transferred support stress 15 is closer to the main tunnel 1, which can easily induce the surrounding rock crushing and large deformation of the main tunnel. By implementing the tunnel protection construction method of the present invention, the pre-grouting reinforcement of the withdrawal channel 12 of the stop mining line and the protective coal pillar is first realized, and the mining stress transfer process caused by the compression and damage of the coal pillar is blocked, and the higher concentrated stress, that is, the pre-grouting support stress 16 is controlled between the stop mining line 2 and the new tunnel 3. At the same time, the deformation of the new tunnel 3 itself has a pressure relief effect, and the purpose of stress control and tunnel protection combining pressure control and pressure relief is achieved.

[0033] The above description is merely a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any minor modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for stress control and tunnel protection by pre-grouting reinforcement of a tunnel on a stopped mining line, characterized in that: The following steps are involved: S01. Excavate a new tunnel (3) between the working face stop line (2) and the protected main tunnel (1); S02. Construct three groups of grouting holes on both sides of the newly excavated roadway (3). From top to bottom, the mining side is provided with the following sequence: mining side group I holes (4), mining side group II holes (5), and mining side group III holes (6). From top to bottom, the main roadway side is provided with the following sequence: main roadway side group I holes (7), main roadway side group II holes (8), and main roadway side group III holes (9); S03 installation of the orifice pipe, and the new tunnel (3) construction of the full section of shotcrete (10), closed surrounding rock to prevent grouting slurry exposed; S04. Injecting ultrafine cement slurry into the surrounding rocks on both sides through the orifice pipe to form a corresponding surrounding rock grouting reinforcement range (11); S05. After the working face advances to the stop mining line (2), a support withdrawal channel (12) is formed, and the top and side surrounding rocks of the support withdrawal channel (12) are both within the grouting reinforcement range (11).

2. The stress control and tunnel protection method for pre-grouting reinforcement of a tunnel on a stop-mining line according to claim 1 is characterized in that: In S02, three groups of grouting holes are distributed radially along the two sides of the newly excavated tunnel (3).

3. The stress control and tunnel protection method for pre-grouting reinforcement of a tunnel on a stop-mining line according to claim 1 is characterized in that: In S02, the final hole positions of the mining side group I holes (4) and the mining side group II holes (5) are located 1500mm to 3000mm above the coal seam roof to ensure effective reinforcement of the coal seam roof and the coal-rock contact surface. At the same time, the final hole positions of the mining side group II holes (5) and the mining side group III holes (6) exceed the stop-mining line and are located at the tail end of the coal mining hydraulic support (13) to achieve pre-reinforcement of the surrounding rock of the support withdrawal channel (12) after stopping mining.

4. The method for stress control and tunnel protection by pre-grouting reinforcement of a tunnel driven by a stop-mining line according to claim 1 is characterized in that: The final hole position of group I holes (7) on the side of the S02 middle and large tunnel is located 1500mm to 3000mm above the coal seam roof to ensure effective reinforcement of the coal seam roof and the coal-rock contact surface.

5. The method for stress control and tunnel protection by pre-grouting reinforcement of a tunnel driven by a stop-mining line according to claim 1, characterized in that: The water-cement ratio of ultrafine cement slurry used in S04 grouting is controlled at 0.8 ～ 1.2, add 1% of the cement dosage of dispersant, and prepare the slurry through a high-speed mixer to ensure that the slurry can fully penetrate into the cracks of the surrounding rock.

6. The method for stress control and tunnel protection by pre-grouting reinforcement of a tunnel driven by a stop-mining line according to claim 1, characterized in that: The grouting pressure at the bottom of the grouting holes on the side of the main tunnel in S04 is controlled at 3MPa~5MPa to prevent the slurry from invading the main tunnel; the grouting pressure at the bottom of the group I holes (4) on the mining side is controlled at 5MPa~8MPa, and the grouting pressure at the bottom of the group II holes (5) and group III holes (6) on the mining side is controlled at 8MPa~10MPa.

Images