Method for preventing and treating rock burst of hard rock roadway through coupling of sound field and liquid CO2

Abstract

According to the sound field and liquid CO2 coupled hard rock roadway rockburst prevention and control method, in the operation process, based on the cavitation effect, the mechanical vibration effect and the heat effect of high-frequency ultrasound, fatigue damage occurs in rock, the heat damage effect caused by the heat effect enables mineral particles to be subjected to phase change, the physical and mechanical properties of the rock are degraded, and the rock burst prevention and control effect is achieved. And micro-cracks in the rock mass are penetrated to finally form macro-cracks. After liquid CO2 enters the operation hole, the action mechanism can be divided into two parts, one part can generate phase change expansion, and the rock mass is further fractured on the basis of cracks generated by ultrasonic excitation; secondly, acidic substances formed by CO2 and water react with some matrixes of the rock mass, the integrity of the rock mass is destroyed, and the time-lag rock burst risk is eliminated. Meanwhile, due to the wedging effect of water and the pressure relief effect of the operation holes, release of high stress in the rock mass can be promoted, multi-dimensional rock burst prevention and control are achieved, mechanical disturbance is small, and the advantages of being clean, environmentally friendly and capable of efficiently preventing and controlling rock burst are achieved.

Description

Technical Field

[0001] The invention belongs to the field of rock burst control in underground hard rock mine tunnels, and in particular relates to a hard rock tunnel rock burst prevention method by coupling an acoustic field with liquid CO2. Background Art

[0002] As underground rock mass projects deepen, geological conditions become more complex, and frequent rock bursts have become the primary problem that needs to be solved in deep hard rock construction. After deep tunnel excavation, the equilibrium state of the initial stress of the surrounding rock is destroyed, and the elastic strain energy stored in the hard and brittle rock mass is violently released to trigger rock bursts, resulting in dynamic instability disasters such as rock bursting, ejection, and throwing. Due to its wide impact range, great power, and strong destructive power, it poses a serious threat to the safety of personnel, equipment, underground structures, and passages.

[0003] At present, there are two ideas for rock burst prevention and control: pressure relief and reinforcement. The former includes advance pressure relief holes, hydraulic fracturing, blasting and other methods, while the latter uses components such as energy-absorbing anchor rods to achieve rock burst prevention and control. However, conventional blasting methods may cause secondary damage to the surrounding rock of the tunnel, and the advance pressure relief holes cannot completely release the strain energy accumulated in the rock burst incubation zone. Although components such as energy-absorbing anchor rods can absorb energy through plastic deformation of the rod body or by utilizing the friction between the rod body and the structure, the cost is relatively high. For example, a microwave-gained CO2 phase change pressure relief method for rock burst prevention and control with application number CN202110545558.8 mainly utilizes the heat of microwave irradiation combined with the thermal expansion and cold contraction of the rock matrix caused by the heterogeneity of the rock mass to create uneven gaps, and uses supercritical CO2 in prefabricated fractures. Phase change expansion based on the ripples can achieve the purpose of rapid pressure relief, but microwave penetration is limited and microwave radiation is harmful to the human body. The storage and transportation of CO2 supercritical state need to maintain a certain pressure and temperature, and its construction safety still needs to be further verified; such as the construction method of rock burst prevention and control in high-temperature tunnels with application number CN202011628358.0, which improves the stress state of the surrounding rock by blasting and softening the tunnel surface with high-pressure water, but if the charge is not well controlled, it may even cause secondary damage, thereby increasing the support and maintenance cost of the tunnel and even threatening the safety of personnel and equipment. The acoustic field excitation combined with liquid CO2 fracturing has the advantages of small mechanical disturbance, clean and environmentally friendly, and efficient stress release.

[0004] Therefore, it is of great significance to propose a method for preventing and controlling rock bursts in hard rock tunnels by coupling sound field with liquid CO2. Summary of the invention

[0005] The main technical problem to be solved by the present invention is to provide a method for preventing and controlling rock bursts in hard rock tunnels by opening and promoting the development of microcracks in the rock mass according to the high-frequency ultrasonic cavitation effect, mechanical vibration effect, and thermal effect, utilizing the phase change expansion and cracking of liquid CO2 and the softening effect of water. At the same time, the water and CO2 in the rock mass will react with certain mineral components. The working hole can also be used as a pressure relief hole to diffuse the stress to the deep, improve the surrounding rock conditions in the energy accumulation zone in multiple dimensions, effectively reduce the strength and brittleness of the rock mass, soften the rock mass and release energy, and control the acoustic field of rock bursts and the coupling of liquid CO2.

[0006] In order to solve the above technical problems, the present invention provides a method for preventing and controlling rock burst in hard rock tunnels by coupling an acoustic field with liquid CO2, comprising the following steps:

[0007] S1. Establish a numerical model for the tunnel to be studied to analyze the rockburst tendency, and determine the section location and rockburst grade where rockburst or potential rockburst exists, based on the characteristics of rockburst events on site;

[0008] S2. Drill holes on the arch and side of the tunnel. The holes of different sections are arranged in parallel with a certain spacing to form working holes. The drilling depth depends on the size of the tunnel section and the depth of the rock burst incubation zone.

[0009] S3. Use a bag self-expanding sealer to seal the hole, inject water into the hole, and turn on the ultrasonic transmitter to perform single-hole segmented operations. The single-stage operation lasts 30 to 45 minutes. The number of operation segments and time depend on the cross-sectional size of the tunnel and the rock burst grade.

[0010] S4. After the single-stage operation is completed, the ultrasonic transducer is dragged outward for a certain distance, and this step is repeated until it is about 3 to 5 meters away from the tunnel wall. At this time, the microcracks inside the rock mass will open and continue to develop; the cavitation nucleus of the ultrasonic wave explodes, generating an airflow with a pressure exceeding 1000atm and a temperature exceeding 5000K, and the mechanical vibration further reopens the microcracks inside the rock mass and continues to expand;

[0011] S5. After the single-hole full-section operation is completed, the ultrasonic transducer is taken out, and liquid CO2 is injected through the high-pressure pipe in the above-mentioned operation hole. This step requires the use of an air bag to seal the hole in advance;

[0012] S6. Liquid CO2 will undergo a phase change in the pores and expand rapidly, further breaking the rock mass based on the microcracks formed in steps S3 and S4.

[0013] In a preferred embodiment, the drill holes in the tunnel vault are at an angle of 30-50° to the horizontal line, and the drill holes in the side parts are inclined upward by 5-15°.

[0014] In a preferred embodiment: the boreholes of different cross sections are arranged at a spacing of 4-8m.

[0015] In a preferred embodiment: the spacing between the sealing holes is 0.5m.

[0016] In a preferred embodiment: the outside of the transducer is a protective sleeve, the wire passes through the empty hole on the surface of the protective sleeve, and is wrapped around the connecting rod to the outside of the hole. The bottom of the protective sleeve is a threaded sleeve, and one end of the connecting rod is a thread matching the threaded sleeve at the bottom of the transducer, and the other end is a threaded sleeve consistent with the threaded sleeve at the bottom of the transducer. The length of a single connecting rod is 1m.

[0017] In a preferred embodiment, the ultrasonic transducer is dragged outward, and its dragging position is the tail end of the last connecting rod.

[0018] In a preferred embodiment: the length of the airbag sealing hole is 1m.

[0019] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0020] The present invention adopts ultrasonic excitation and liquid CO2 coupling to prevent and control rock burst in hard rock tunnels. During the operation process, fatigue damage occurs inside the rock based on the cavitation effect, mechanical vibration effect and thermal effect of high-frequency ultrasound, and the thermal damage caused by the thermal effect causes phase change of mineral particles, deterioration of the physical and mechanical properties of the rock, and microcracks inside the rock body penetrate to eventually form macro cracks. The action mechanism of liquid CO2 after entering the working hole can be divided into two parts. One is that phase change expansion will occur, and the rock mass will be further broken on the basis of the cracks generated by ultrasonic excitation; secondly, the acidic substances formed by CO2 and water will react with certain matrices of the rock mass, destroying the integrity of the rock mass and eliminating the risk of time-delay rock burst. At the same time, due to the wedging effect of water and the pressure relief effect of the working hole, the release of high stress inside the rock mass will be promoted, realizing multi-dimensional prevention and control of rock burst, and the mechanical disturbance is small, with the advantages of clean, environmentally friendly and efficient prevention and control of rock burst. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a cross-sectional layout diagram of the ultrasonic working holes in the tunnel of the present invention;

[0022] Figure 2 This is a schematic diagram of the arrangement of ultrasonic working holes along the axis of the tunnel;

[0023] Figure 3 It is a schematic diagram of the inside of the hole during ultrasonic operation; DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments, and all other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making creative work are within the scope of protection of the present invention.

[0025] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "top / bottom" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0026] In the description of the present invention, it should be noted that, unless otherwise clearly stipulated and limited, the terms "installed", "provided with", "mounted / connected", "connected", etc. should be understood in a broad sense. For example, "connection" can be a wall-mounted connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be a direct connection or an indirect connection through an intermediate medium. It can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] This embodiment provides a method for preventing and controlling rock burst in hard rock tunnels by coupling an acoustic field with liquid CO2, comprising the following steps:

[0028] S1. Establish a numerical model for the tunnel to be studied to analyze the rockburst tendency, and determine the section location and rockburst grade where rockburst or potential rockburst exists, based on the characteristics of rockburst events on site;

[0029] S2, drilling hole 1 in the arch of the tunnel and drilling hole 2 in the side. The drilling holes of different sections are arranged in parallel with an interval of 5m to form working holes. The drilling depth depends on the size of the tunnel section and the depth of the rock burst incubation zone, such as Figure 1 , Figure 2 As shown;

[0030] S3, use the bag self-expanding sealer 4 to seal the hole, inject water into the hole through the high-pressure water pipe, and turn on the ultrasonic transmitter to start the single-hole segmented operation. The single-stage operation lasts 30 to 45 minutes. The number of operation sections and time depend on the cross-sectional size of the tunnel and the rock burst grade, such as Figure 3 As shown;

[0031] S4. After the single-stage operation is completed, the tail 9 of the ultrasonic transducer connecting rod is dragged outward for a certain distance, and this step is repeated until it is about 3 to 5 meters away from the tunnel wall. At this time, the microcracks inside the rock body will open and continue to develop. Specifically, the cavitation nucleus of the ultrasonic wave explodes, generating an airflow with a pressure exceeding 1000atm and a temperature exceeding 5000K, and the mechanical vibration further reopens the microcracks inside the rock body and continues to expand;

[0032] S5. After the single-hole full-section operation is completed, the ultrasonic transducer 5 is taken out, and liquid CO2 is injected through the high-pressure pipe in the above-mentioned operation hole. This step requires the use of an air bag to seal the hole in advance;

[0033] S6. Liquid CO2 will undergo phase change in the pores and expand rapidly, further breaking the rock mass based on the microcracks formed in steps S3 and S4.

[0034] S7. In addition to the fact that water itself can destroy the cohesive force of clay minerals and cause wedging, CO2 reacts with water to form H2CO3, which can react with certain mineral components in the rock mass, further destroying the integrity of the rock mass and effectively eliminating the risk of time-lag rock bursts. At the same time, under the action of high stress, the acoustic field and liquid CO2 operating holes can also be used as pressure relief holes, releasing energy through deformation of the pressure relief holes, ultimately achieving the purpose of pressure relief.

[0035] The arch hole 1 in step S2 is at an angle of 30-50° to the horizontal line, and the side hole 2 is inclined upward by 5-15° to facilitate the withdrawal of the ultrasonic transducer. The holes of different cross sections in step S2 are arranged at a certain spacing of 4-8m, which depends on the influence range of the single-hole ultrasound and liquid CO2 operation.

[0036] In addition, the sealing hole 4 described in step S3 has a sealing hole spacing of 0.5m, and water is injected into the hole through a high-pressure water pipe 8; the initial section of the operation section number generally starts from the bottom of the hole, and the specific number of sections depends on the scale of the rock burst, and the operation range should avoid the shallow surrounding rock of the tunnel;

[0037] In addition, the outside of the transducer 5 described in step S4 is a protective sleeve 3, the wire passes through the empty hole on the surface of the protective sleeve, and is wound around the connecting rod to the outside of the hole. The bottom of the protective sleeve 3 is a threaded sleeve 6, and one end of the connecting rod 9 is a thread matching the threaded sleeve at the bottom of the transducer, and the other end is a threaded sleeve consistent with the threaded sleeve at the bottom of the transducer. The length of a single connecting rod is 1m; the dragging position is the tail end of the last connecting rod 9, such as Figure 3 shown.

[0038] Finally, the airbag sealing section 7 described in step S5 is 1 meter long.

[0039] The above description is only a preferred specific implementation mode of the present invention, and does not limit the patent scope of the present invention. Any technical equivalent changes made using the contents of the present invention specification shall fall within the protection scope of the present invention.

Claims

1. A method for preventing and controlling rock burst in hard rock tunnels by coupling an acoustic field with liquid CO2, characterized in that The steps include: S1. Establish a numerical model for the tunnel to be studied to analyze the rockburst tendency, and determine the section location and rockburst grade where rockburst or potential rockburst exists, based on the characteristics of rockburst events on site; S2. Drill holes on the arch and side of the tunnel. The holes of different sections are arranged in parallel with a certain spacing to form working holes. The drilling depth depends on the size of the tunnel section and the depth of the rock burst incubation zone. S3. Use a bag self-expanding sealer to seal the hole, inject water into the hole, and turn on the ultrasonic transmitter to perform single-hole segmented operations. The single-stage operation lasts 30 to 45 minutes. The number of operation segments and time depend on the cross-sectional size of the tunnel and the rock burst grade. S4. After the single-stage operation is completed, the ultrasonic transducer is dragged outward for a certain distance, and this step is repeated until it is about 3 to 5 meters away from the tunnel wall. At this time, the microcracks inside the rock mass will open and continue to develop; the cavitation nucleus of the ultrasonic wave explodes, generating an airflow with a pressure exceeding 1000atm and a temperature exceeding 5000K, and the mechanical vibration further reopens the microcracks inside the rock mass and continues to expand; S5. After the single-hole full-section operation is completed, the ultrasonic transducer is taken out, and liquid CO2 is injected through the high-pressure pipe in the above-mentioned operation hole. This step requires the use of an air bag to seal the hole in advance; S6. Liquid CO2 will undergo a phase change in the pores and expand rapidly, further breaking the rock mass based on the microcracks formed in steps S3 and S4.

2. The method for preventing and controlling rock burst in hard rock tunnels by coupling an acoustic field with liquid CO2 according to claim 1, characterized in that: The drill holes on the tunnel vault are at an angle of 30-50° to the horizontal line, and the drill holes on the side are inclined upward by 5-15°.

3. The method for preventing and controlling rock burst in hard rock tunnels by coupling an acoustic field with liquid CO2 according to claim 1, characterized in that: The boreholes of different sections are arranged at intervals of 4-8m.

4. The method for preventing and controlling rock burst in hard rock tunnels by coupling an acoustic field with liquid CO2 according to claim 1, characterized in that: The spacing between the sealing holes is 0.5m.

5. The method for preventing and controlling rock burst in hard rock tunnels by coupling an acoustic field with liquid CO2 according to claim 1, characterized in that: The outside of the transducer is a protective sleeve, and the wire passes through the empty hole on the surface of the protective sleeve and is wrapped around the connecting rod to the outside of the hole. The bottom of the protective sleeve is a threaded sleeve, and one end of the connecting rod is a thread that matches the threaded sleeve at the bottom of the transducer, and the other end is a threaded sleeve that is consistent with the threaded sleeve at the bottom of the transducer. The length of a single connecting rod is 1m.

6. The method for preventing and controlling rock burst in hard rock tunnels by coupling an acoustic field with liquid CO2 according to claim 1, characterized in that: The ultrasonic transducer is dragged outward, and its dragging position is the tail end of the last connecting rod.

7. The method for preventing and controlling rock burst in hard rock tunnels by coupling an acoustic field with liquid CO2 according to claim 1, characterized in that: The length of the airbag sealing hole is 1m.

Images