A method for reducing ground pressure in a deep brittle rock roadway

Abstract

The application discloses a kind of deep brittle rock stratum roadway ground pressure reduction method, S1: every interval 10-15m is laid in roadway A group of monitoring points;S2: using monitoring point to surrounding rock surface displacement and mine pressure are monitored, record the monitoring point of surrounding rock surface displacement and mine pressure exceed safe value A;S3: 5-7.5m interval is extended as to-be-drilled hole section before and after, along the central position of left and right sides of roadway Horizontal drilling is drilled two rows of straight line main pressure relief hole;S4: the monitoring point of setting is re-set safe value B, again record the monitoring point of surrounding rock surface displacement and mine pressure exceed safe value B in monitoring period;If there is monitoring point exceeding safe value B, along the central position of up and down of left and right sides of roadway Horizontal drilling is drilled a row of straight line auxiliary pressure relief hole;S5: using grouting or spraying method carries out hole repair or plugging, can effectively reduce high ground pressure in actual engineering, weaken stress concentration, effectively reduce the rock burst intensity of deep brittle rock stratum, to achieve the purpose of preventing rock burst.

Description

Technical Field

[0001] This invention belongs to the field of rock mechanics and geotechnical engineering technology, and mainly relates to a method for reducing high ground pressure in deep brittle rock tunnels. Background Technology

[0002] With the continuous development of my country's economy, engineering construction has gradually shifted from the surface and shallow ground to deep underground. As deep engineering projects increase, the probability of rockbursts also rises significantly. The conditions for a rockburst are high in-situ stress in the rock mass exceeding the rock's inherent strength, coupled with the rock's high brittleness and elasticity. The release of accumulated energy within the rock mass leads to rock fracturing and the ejection of fragmented rock. Rockburst disasters are characterized by their suddenness, instantaneity, and intensity.

[0003] In particular, deep brittle rock masses are in a complex mechanical environment with high ground stress, high karst water pressure, high ground temperature and engineering disturbances. They are prone to stress concentration, deformation and storage of strain energy, which can lead to rock bursts and seriously threaten the normal operation of existing underground projects. Summary of the Invention

[0004] The present invention aims to provide a ground pressure reduction method specifically for deep brittle rock tunnels, which can effectively reduce the high ground stress accumulated in deep brittle rock layers without affecting the normal use of the tunnel or damaging the structural stability of the tunnel.

[0005] To achieve the above objectives, this invention proposes a method for reducing ground pressure in deep brittle rock tunnels, comprising the following steps:

[0006] S1: During the construction of deep brittle rock tunnels, a set of monitoring points is set up every 10-15m in the tunnel. Each set of monitoring points includes one monitoring point on each of the left and right sides of the tunnel inner wall.

[0007] S2: After the tunnel construction is completed, the displacement of the surrounding rock surface and the mining pressure are monitored using monitoring points. The monitoring period is 3-5 days, and the monitoring points where the displacement of the surrounding rock surface and the mining pressure exceed the safety value A are recorded during the monitoring period.

[0008] S3: Extend the section by 5-7.5m before and after the monitoring point that exceeds the safety value as the section to be drilled. Use a pneumatic column-mounted drilling rig to drill two rows of straight main pressure relief holes horizontally at the upper and lower center positions on both sides of the roadway. The drilling parameters are set as follows: hole diameter 40-50mm, hole depth 15-25m, hole spacing and row spacing 800-1000mm respectively to reduce ground pressure.

[0009] S4: Reset the safety value B for the monitoring points set up in step S2, and continue monitoring. The monitoring period is 20-30 days. Record the monitoring points where the displacement of the surrounding rock surface and the mine pressure exceed the safety value B within the monitoring period. The safety value B is less than or equal to the safety value A.

[0010] If there are monitoring points exceeding the safety value B, extend the section before and after each monitoring point exceeding the safety value B by 7.5-10m as the drilling section. Use a pneumatic column-mounted drilling rig to horizontally drill a row of straight auxiliary pressure-reducing holes at the top and bottom center positions on both sides of the roadway to further reduce ground pressure. The drilling parameters are set as follows: hole diameter 20-25mm, hole depth 15-25m, and hole spacing 800-1000mm. For drilling sections where auxiliary pressure-reducing holes coincide with main pressure-reducing holes, ensure that the auxiliary pressure-reducing holes are staggered from the main pressure-reducing holes and centered between the two main pressure-reducing holes. If there are no monitoring points exceeding the safety value B, it indicates that the roadway ground pressure has been reduced.

[0011] S5: Use grouting or spraying methods to fill or seal the main and auxiliary pressure relief holes;

[0012] S6: The deep brittle rock strata tunnel has been put into normal use.

[0013] As a preferred option of the above scheme, in steps S3 and S4, wet drilling or drilling with dust suppression at the borehole opening is used to drill from the low-stress area to the high-stress area, ensuring the air quality at the construction site and guaranteeing construction safety.

[0014] More preferably, in step S2, the safety value A is a rock surface displacement of 0.25m to 0.4m and a mine pressure of 25MPa to 30MPa; the safety value B is a rock surface displacement of 0.1m to 0.25m and a mine pressure of 20MPa to 25MPa.

[0015] More preferably, in step S1, a set of monitoring points is set up every 10m in the tunnel, and in step S2, the monitoring cycle is 3 days.

[0016] Further preferably, in step S3, the intervals extending 5m before and after the monitoring point exceeding the safety value are designated as the drilling section, and the drilling parameters of the main pressure relief hole are set as follows: hole diameter 50mm, hole depth 20m, hole spacing 800mm, and row spacing 1000mm.

[0017] More preferably, in step S4, the monitoring cycle is 30 days, and the drilling parameters of the auxiliary pressure relief hole are set as follows: hole diameter 25mm, hole depth 20m, and hole spacing 800mm.

[0018] The beneficial effects of this invention are as follows: By pre-setting monitoring points during the construction of tunnels in deep brittle rock formations, and using these monitoring points to monitor the surface displacement and mine pressure of the surrounding rock after construction, and by drilling to depressurize sections where the surface displacement and mine pressure exceed safe values, high ground pressure in actual engineering can be effectively reduced, stress concentration can be weakened, and the intensity of rockbursts in deep brittle rock formations can be effectively reduced, thereby preventing rockbursts. After the ground pressure is reduced to a safe level, the tunnel can be put into normal use, ensuring the safety of construction personnel and equipment within the tunnel. This method is simple, easy to implement, and highly intuitive. Using drilling to depressurize deep brittle rock masses can effectively reduce the high elastic energy accumulated in deep brittle rock formations, thereby reducing stress concentration and ground pressure. Attached Figure Description

[0019] Figure 1 This is a comparison image before and after pressure relief during drilling.

[0020] Figure 2 This is an enlarged cross-sectional diagram of the borehole pressure relief process.

[0021] Figure 3 Plan view for borehole layout.

[0022] Figure 4 A schematic diagram of the main pressure relief hole construction. Detailed Implementation

[0023] To describe the present invention, the following detailed description is provided in conjunction with the accompanying drawings and embodiments.

[0024] A method for reducing ground pressure in deep brittle rock tunnels, combined with Figure 2 — Figure 4 As shown, it includes the following steps:

[0025] S1: During the construction of deep brittle rock tunnels, a set of monitoring points is set up every 10-15m within the tunnel. Each set of monitoring points includes one monitoring point on each of the left and right sides of the tunnel inner wall. Preferably, a set of monitoring points is set up every 10m within the tunnel. Stress monitoring is conducted on the test section before drilling begins to determine the range, condition, and degree of danger of the pressure zone.

[0026] S2: After the tunnel construction is completed, monitoring points are used to monitor the surface displacement of the surrounding rock and the mine pressure. The monitoring period is 3-5 days, and the monitoring points where the surface displacement of the surrounding rock and the mine pressure exceed the safety value A are recorded during the monitoring period. Preferably, the monitoring period is 3 days.

[0027] S3: Extend the section by 5-7.5m before and after the monitoring point that exceeds the safety value as the section to be drilled. Use a pneumatic column-mounted drilling rig to drill two rows of straight main pressure relief holes horizontally at the upper and lower center positions on both sides of the roadway. The drilling parameters are set as follows: hole diameter 40-50mm, hole depth 15-25m, hole spacing and row spacing 800-1000mm respectively to reduce ground pressure.

[0028] Preferably, wet drilling or wellhead dust collection methods are used to drill the main pressure relief holes from the low-stress zone to the high-stress zone. Furthermore, the safety value A is defined as a surrounding rock surface displacement of 0.25m to 0.4m and a mine pressure of 25MPa to 30MPa. A 5m extension before and after the monitoring point exceeding the safety value is designated as the drilling section. The drilling parameters for the main pressure relief holes are set as follows: hole diameter 50mm, hole depth 20m, hole spacing 800mm, and row spacing 1000mm.

[0029] S4: Reset the safety value B for the monitoring points set up in step S2, and continue monitoring. The monitoring period is 20-30 days. Record the monitoring points where the displacement of the surrounding rock surface and the mine pressure exceed the safety value B within the monitoring period. The safety value B is less than or equal to the safety value A.

[0030] If monitoring points exceeding the safety value B exist, extend the section before and after each monitoring point exceeding the safety value B by 7.5-10m as the drilling section. Use a pneumatic column-mounted drilling rig to horizontally drill a row of straight auxiliary pressure-reducing holes at the top and bottom center positions on both sides of the roadway to further reduce ground pressure. Drilling parameters are set as follows: hole diameter 20-25mm, hole depth 15-25m, hole spacing 800-1000mm. For drilling sections where auxiliary pressure-reducing holes coincide with main pressure-reducing holes, ensure that the auxiliary pressure-reducing holes are staggered from the main pressure-reducing holes and centered between the two main pressure-reducing holes. If no monitoring points exceeding the safety value B exist, it indicates that the roadway ground pressure has been reduced.

[0031] Figure 1 The image shows a comparison before and after borehole depressurization. As can be seen, before depressurization, the stress reaches its peak value quickly and at a high level, close to the free surface, making rockbursts more likely. After depressurization, the stress reaches its peak value slowly and at a slightly lower level, farther from the free surface, thus preventing rockbursts. By setting up depressurization boreholes, high ground pressure in practical engineering can be effectively reduced, stress concentration can be weakened, and the intensity of rockbursts in deep brittle rock layers can be significantly reduced, thereby preventing rockbursts. Figure 2As shown, drilling in high-stress rock masses causes cracks to propagate around the borehole, creating a fractured zone. The interconnected fractured zones of multiple boreholes create relatively weakened zones within the rock mass, reducing peak stress and increasing its deformation capacity. This increased deformation consumes energy stored within the rock by external forces, improving energy dissipation and premature energy release, effectively reducing the rock strata's ability to store elastic energy. Using appropriate parameters for main and auxiliary pressure-relief holes ensures that the structural strength of the tunnel is not damaged while simultaneously reducing ground stress and preventing rockbursts. Drilling should be carried out evenly, avoiding excessive force, and proceeding smoothly and naturally.

[0032] Preferably, wet drilling or borehole dust collection methods are used to construct auxiliary pressure relief holes from the low-stress zone to the high-stress zone. Furthermore, the safety value B is 0.1m–0.25m of surrounding rock surface displacement and 20MPa–25MPa of mine pressure; the monitoring period is 30 days; and the drilling parameters for the auxiliary pressure relief holes are set as follows: hole diameter 25mm, hole depth 20m, and hole spacing 800mm.

[0033] S5: Use grouting or spraying methods to fill or seal the main and auxiliary pressure relief holes.

[0034] S6: The deep brittle rock strata tunnel has been put into normal use.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for reducing ground pressure in deep brittle rock tunnels, characterized in that, Includes the following steps: S1: During the construction of deep brittle rock tunnels, a set of monitoring points is set up every 10-15m in the tunnel. Each set of monitoring points includes one monitoring point on each of the left and right sides of the tunnel inner wall. S2: After the tunnel construction is completed, the displacement of the surrounding rock surface and the mining pressure are monitored using monitoring points. The monitoring period is 3-5 days, and the monitoring points where the displacement of the surrounding rock surface and the mining pressure exceed the safety value A are recorded during the monitoring period. S3: Extend the section by 5-7.5m before and after the monitoring point that exceeds the safety value as the section to be drilled. Use a pneumatic column-mounted drilling rig to drill two rows of straight main pressure relief holes horizontally at the upper and lower center positions on both sides of the roadway. The drilling parameters are set as follows: hole diameter 40-50mm, hole depth 15-25m, hole spacing and row spacing 800-1000mm respectively to reduce ground pressure. S4: Reset the safety value B for the monitoring points set up in step S2, and continue monitoring. The monitoring period is 20-30 days. Record the monitoring points where the displacement of the surrounding rock surface and the mine pressure exceed the safety value B within the monitoring period. The safety value B is less than or equal to the safety value A. If there are monitoring points exceeding the safety value B, extend the section before and after each monitoring point exceeding the safety value B by 7.5-10m as the drilling section. Use a pneumatic column-mounted drilling rig to horizontally drill a row of straight auxiliary pressure-reducing holes at the top and bottom center positions on both sides of the roadway to further reduce ground pressure. The drilling parameters are set as follows: hole diameter 20-25mm, hole depth 15-25m, and hole spacing 800-1000mm. For drilling sections where auxiliary pressure-reducing holes coincide with main pressure-reducing holes, ensure that the auxiliary pressure-reducing holes are staggered from the main pressure-reducing holes and centered between the two main pressure-reducing holes. If there are no monitoring points exceeding the safety value B, it indicates that the roadway ground pressure has been reduced. S5: Use grouting or spraying methods to fill or seal the main and auxiliary pressure relief holes; S6: The deep brittle rock strata tunnel has been put into normal use.

2. The method for reducing ground pressure in deep brittle rock tunnels according to claim 1, characterized in that: In steps S3 and S4, wet drilling or borehole dust collection methods are used to drill from the low-stress zone to the high-stress zone.

3. The method for reducing ground pressure in deep brittle rock tunnels according to claim 1, characterized in that: In step S2, the safety value A is the displacement of the surrounding rock surface of 0.25m to 0.4m and the mine pressure of 25MPa to 30MPa; the safety value B is the displacement of the surrounding rock surface of 0.1m to 0.25m and the mine pressure of 20MPa to 25MPa.

4. The method for reducing ground pressure in deep brittle rock tunnels according to claim 1, characterized in that: In step S1, a set of monitoring points is set up every 10m in the tunnel, and the monitoring cycle in step S2 is 3 days.

5. The method for reducing ground pressure in deep brittle rock tunnels according to claim 1, characterized in that: In step S3, the section extending 5m before and after the monitoring point that exceeds the safety value is designated as the drilling section. The drilling parameters of the main pressure relief hole are set as follows: hole diameter 50mm, hole depth 20m, hole spacing 800mm, and row spacing 1000mm.

6. The method for reducing ground pressure in deep brittle rock tunnels according to claim 1, characterized in that: In step S4, the monitoring cycle is 30 days, and the drilling parameters of the auxiliary pressure relief hole are set as follows: hole diameter 25mm, hole depth 20m, and hole spacing 800mm.

Images