CN113494299B - Tunnel rockburst grading prevention and control method using NPR material - Google Patents
Tunnel rockburst grading prevention and control method using NPR material Download PDFInfo
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
- E21D11/04—Lining with building materials
- E21D11/10—Lining with building materials with concrete cast in situ; Shuttering also lost shutterings, e.g. made of blocks, of metal plates or other equipment adapted therefor
- E21D11/105—Transport or application of concrete specially adapted for the lining of tunnels or galleries ; Backfilling the space between main building element and the surrounding rock, e.g. with concrete
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
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Abstract
The invention discloses a tunnel rock burst grading prevention and control method by utilizing an NPR material. Aiming at the weak rockburst area, a prevention and control scheme of spraying concrete, drilling small-aperture pressure relief holes and installing NPR anchor rods and reinforcing mesh is adopted; aiming at the medium rockburst area, a prevention and control scheme of spraying steel fiber concrete, drilling large and small-aperture pressure relief holes, installing NPR anchor rods/cables and reinforcing mesh, injecting water into anchor cable drill holes and drilling tunnel face pressure relief holes is adopted; aiming at a strong rock burst area, a prevention and control scheme of spraying NPR steel fiber concrete, drilling large and small-aperture pressure relief holes, laying a flexible buffer layer and a reinforcing mesh, installing NPR anchor rods/cables, erecting NPR steel arch frames, injecting water into anchor cable drill holes, drilling tunnel face pressure relief holes and tunnel face blast holes is adopted; due to the existence of the large-aperture pressure relief holes and the small-aperture pressure relief holes, the surrounding rock has a free surface along the tangential direction of the tunnel, so that tangential deformation can be generated under the action of pressure, and elastic strain energy is released. And water is injected into the anchor cable drill hole to weaken the strength of the rock mass inside the tunnel surrounding rock, so that the rock burst occurrence probability is reduced.
Description
Technical Field
The invention belongs to the technical field of tunnel construction, and particularly relates to a tunnel rockburst grading prevention and control method by utilizing an NPR material.
Background
With the increasing demand of people for resources, energy and infrastructure, underground engineering in the fields of hydraulic engineering, mines, highways, railways and the like develops towards deep parts. For example, the maximum burial depth of a diversion tunnel of a brocade secondary hydropower station reaches 2525m, the mining depth of Witwatersrand gold mine in south Africa is close to 5000m, and a planned Sichuan railway comprises a tunnel with 35 high burial depths, and the maximum burial depth reaches 2600 m. With the increasing depth of underground engineering, the number of engineering disasters is increasing, and the most important problem is the rock burst disaster induced by high ground stress. Rock burst is a special phenomenon in underground engineering, has the characteristics that surrounding rocks are suddenly and violently ejected, thrown and sprayed into an excavation space, can cause serious personal casualties, equipment damage and huge economic loss, and becomes one of key problems for restricting the construction safety of deep engineering.
In recent decades, researchers at home and abroad have conducted a great deal of research work on rockburst control, and various rockburst control technologies have been proposed. The method mainly comprises two categories: the first type is a surrounding rock modification method. Namely, rock burst is prevented and controlled by a method for improving the mechanical property of surrounding rock, such as drilling pressure relief, water injection, loosening blasting and the like; the second type is a surrounding rock reinforcement method. The rock burst is prevented by a method for reinforcing surrounding rocks of the roadway, such as sprayed concrete, anchor net support, grouting reinforcement, steel arch frame erection and the like. The surrounding rock modification method can reduce elastic strain energy stored in tunnel surrounding rock to a certain extent so as to reduce the possibility of rock burst, but cannot effectively control the occurrence of rock burst disasters, and cannot protect personnel and equipment when rock burst occurs; the conventional supporting materials are mostly adopted for surrounding rock reinforcement by the surrounding rock reinforcement method, the surrounding rock reinforcement method does not have large deformation characteristics, and the roadway surrounding rock reinforced by the materials is easy to gather elastic strain energy and is not beneficial to preventing rock burst; and the material is easy to break suddenly under the action of impact load, so that the support fails, and the rock burst control effect is not ideal.
For example, the chinese patent CN108518232A discloses a single-track railway tunnel rock burst prevention support method corresponding to different rock burst intensity levels, which adopts different support methods for single-track railway tunnels under slight rock burst, medium rock burst and strong rock burst respectively; the slight rockburst section adopts rock surface spraying high-pressure water, primary spraying concrete, setting a mortar anchor rod and a reinforcing mesh for supporting; in the medium rock burst section, high-pressure water is sprayed on the rock surface, steel fiber concrete is sprayed initially, and a shell-expanding type prestressed hollow anchor rod and a reinforcing mesh are arranged for supporting; the strong rock burst section adopts the steps of arranging an advanced prestress release hole and an advanced anchor rod, spraying and injecting high-pressure water on the rock surface, primarily spraying steel fiber concrete, arranging an expansion shell type prestressed hollow anchor rod and a reinforcing mesh and erecting a steel arch frame for supporting; the patent provides a supporting method aiming at the single-track railway tunnel rock burst prevention according to different rock burst intensity levels. However, the used supporting materials are conventional anchor rods and anchor cables, and have no large deformation characteristic, and when rock burst occurs, the conventional supporting materials are easy to break under the action of impact load; in addition, after the tunnel is excavated, the concrete is sprayed for early support, and the concrete covers the surface of the surrounding rock of the tunnel, so that the high-pressure water spraying softening effect is not obvious, and the rock burst control effect is not ideal.
The existing tunnel rock burst prevention and control method mainly adopts anchor rods, anchor cables, reinforcing mesh and the like based on conventional materials for combined support. Besides, some anchor rods with energy absorption function are gradually applied to tunnel rock burst prevention and control. For example, chinese patent CN112983470A discloses a support system and a support method for a soft rock tunnel TBM, in which a through hole is provided in the middle of a segment, and NPR anchors are provided in the through holes, which anchor and constrain surrounding rocks, to form a strong temporary support system with the combination of the NPR anchors and the segment as the core. The supporting method comprises the following specific steps: the first step is as follows: paving a reinforcing mesh on the wall surface of the tunnel after tunnel face tunneling; the second step is that: assembling the pipe pieces into an annular pipeline on the reinforcing steel bar net; the third step: installing an NPR anchoring part in the through hole of the segment; and fourthly, removing the duct piece after the surrounding rock is stabilized, and performing secondary lining construction. When the surrounding rock is deformed greatly to release the deformation energy of the surrounding rock, the NPR anchor rod and/or the NPR anchor cable are deformed greatly, a certain surrounding rock deformation space is provided, high constant resistance is still kept, and a large amount of surrounding rock deformation energy is absorbed in the process. However, the support system lacks effective pressure relief measures for the tunnel surrounding rock, the energy absorbed by the anchor rods and/or the anchor cables is limited, the slow release of the energy cannot be realized, and the energy of the tunnel surrounding rock is easily gathered to cause rock burst. Therefore, an integrated tunnel rockburst prevention and control method giving consideration to pressure relief, support and softening is urgently needed, so that the problem that the prevention and control effect in the prior art is not ideal is solved, and effective prevention and control of tunnel rockburst is realized.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a tunnel rock burst grading prevention and control method by utilizing NPR materials, which forms a 'pressure relief-support-softening' coupled prevention and control scheme by adopting prevention and control measures of spraying steel fiber concrete, drilling anchor rod drill holes and small-aperture pressure relief holes, laying flexible buffer layers and reinforcing mesh, installing NPR anchor rods, drilling anchor rod drill holes and large-aperture pressure relief holes, installing NPR anchor cables and W-shaped steel strips, injecting water into the anchor rod drill holes to soften rock mass, erecting NPR steel arches, drilling tunnel face pressure relief holes and blast holes and the like. Setting different prevention and control methods according to different rock burst intensity levels; thereby realizing the effective prevention and control of the tunnel rock burst.
In order to achieve the purpose of the invention, the method is specifically realized by the following technologies:
a tunnel rockburst grading prevention and control method using an NPR material comprises the following specific steps:
aiming at the weak rockburst area, a control scheme of primary concrete spraying, anchor rod drilling and small-aperture pressure relief holes drilling, NPR anchor rod and reinforcing mesh installation and concrete re-spraying is adopted;
aiming at a medium rockburst area, adopting a control scheme of primary spraying of steel fiber concrete, drilling of an anchor rod drilling hole and a small-aperture pressure relief hole, installation of an NPR anchor rod and a reinforcing mesh, drilling of an anchor rope drilling hole and a large-aperture pressure relief hole, installation of an NPR anchor rope and a W-shaped steel band, secondary spraying of steel fiber concrete, injection of water into the anchor rope drilling hole to soften a rock mass, and drilling of a tunnel face pressure relief hole;
aiming at a strong rockburst area, the control scheme of primary spraying of NPR steel fiber concrete, drilling of anchor rod drill holes and small-aperture pressure relief holes, laying of flexible buffer layers and reinforcing mesh, installation of NPR anchor rods, drilling of anchor rope drill holes and large-aperture pressure relief holes, installation of NPR anchor ropes and W-shaped steel bands, erection of NPR steel arches, secondary spraying of NPR steel fiber concrete, water injection of softened rock mass into the anchor rope drill holes, and drilling of tunnel face pressure relief holes and tunnel face blast holes is adopted.
The invention carries out grading prevention and control aiming at different rock burst grades, and gives play to the material performance to the maximum extent; the flexible buffer layer can absorb the energy of the surrounding rock; the NPR anchor rod and the NPR anchor cable have good constant-resistance yielding characteristics, and can absorb surrounding rock energy through self deformation, so that the energy in a rock body is slowly released. Meanwhile, due to the existence of the small aperture and the large aperture, the surrounding rock has a free surface along the tangential direction of the tunnel, so that the tangential deformation can be generated under the action of pressure, the elastic strain energy is released, the deformation energy of the surrounding rock is released, and the occurrence probability of rock burst is reduced.
Further, the NPR anchor rod comprises a first constant resistance device, the first constant resistance device is installed in the small-aperture pressure relief hole, the first constant resistance device and the small-aperture pressure relief hole are coaxial, and the diameter of the small-aperture pressure relief hole is larger than that of the first constant resistance device; the depth of the small-bore pressure relief hole is larger than the length of the first constant resistance device.
Further, the difference value between the diameters of the small-aperture pressure relief hole and the first constant resistance device is 40-43 mm, and the difference value between the depth of the small-aperture pressure relief hole and the length of the first constant resistance device is 100-200 mm.
Further, the NPR anchor cable includes a second constant resistance device, the second constant resistance device is mounted in the large-aperture pressure relief hole, the second constant resistance device is coaxial with the large-aperture pressure relief hole, and the diameter of the large-aperture pressure relief hole is larger than that of the second constant resistance device; the depth of the large-aperture pressure relief hole is greater than the length of the second constant resistance device.
Furthermore, the difference between the diameters of the large-aperture pressure relief hole and the second constant resistance device is 50-55 mm, and the difference between the depth of the large-aperture pressure relief hole and the length of the second constant resistance device is 100-400 mm.
Furthermore, the NPR anchor rope is a hollow anchor rope, a water injection pipe is arranged in the middle of the anchor rope, and water outlet holes are formed in the positions, corresponding to the NPR anchor rope and the water injection pipe, of the NPR anchor rope. Through water injection hole to anchor rope drilling hole water injection, moist tunnel country rock mass inside, the rock mass is by the moist back of water, and the cohesive force reduces between the rock mass granule, and contact surface frictional force reduces, leads to its intensity and fragility to reduce the rockburst probability of taking place.
Furthermore, the face pressure relief holes are distributed in the middle point of the connecting line between the center of the bottom plate and the inner wall of the roadway, and the face pressure relief holes are distributed on the face in a fan shape.
Furthermore, the face surface blasting holes are distributed at 5/8 positions of the connecting line length between the center of the bottom plate and the inner wall of the roadway, and the face surface blasting holes are distributed on the face surface in a fan shape.
Elastic energy stored in rock mass in front of the face is released in advance by drilling the face and blasting holes to relieve pressure, so that the disturbance effect of face tunneling on tunnel surrounding rock is weakened, and the tunneling construction is prevented from inducing rock burst.
Compared with the prior art, the invention has the advantages that:
(1) the yielding deformation capability of the surrounding rock along the radial direction of the tunnel is improved, so that the gathering of elastic strain energy is reduced, and the occurrence probability of rock burst is reduced. The NPR anchor rod/cable has good constant-resistance yielding characteristic, and when the stress of surrounding rocks of a roadway is concentrated to a certain degree and reaches the constant-resistance value, the NPR anchor rod/cable absorbs the energy of the surrounding rocks through tensile deformation to slowly release the energy in a rock body, so that the rock burst occurrence probability is reduced.
(2) The yielding deformation capability of the surrounding rock along the tangential direction of the tunnel is improved, so that the gathering of elastic strain energy is reduced, and the occurrence probability of rock burst is reduced. The existence of small-aperture pressure relief holes and large-aperture pressure relief holes, and the pressure yielding space exists between the large-aperture pressure relief holes and the small-aperture pressure relief holes and the constant resistance device, so that the surrounding rock has a free surface along the tangential direction of the tunnel, thereby generating tangential deformation under the action of pressure and releasing elastic strain energy.
(3) The strength of the rock mass in the tunnel surrounding rock is weakened, and the rock burst occurrence probability is reduced. Through injecting water into anchor rope drilling to moist the inside rock mass of country rock, the rock mass is by the water moist back, and the cohesive force reduces between the rock mass granule, and contact surface frictional force reduces, leads to its intensity and fragility to reduce the rock burst probability of taking place.
(4) The induction effect of tunnel face tunneling on tunnel rockburst can be weakened. The elastic energy stored in the rock body in front of the face is released in advance by drilling the pressure relief holes and the blast holes on the face, so that the disturbance effect of face tunneling on tunnel surrounding rock is weakened, and the tunneling construction is prevented from inducing rock burst.
(5) When rock burst occurs, firstly, the flexible buffer layer can absorb surrounding rock energy and transmit the absorbed residual energy to the supporting structure; and then, the NPR anchor rods, the NPR anchor cables, the reinforcing mesh, the steel arch frame and other supporting materials are under the action of load, and can be instantly stretched and deformed to passively absorb the energy of surrounding rocks, so that the destructiveness of rock burst is reduced, and the construction safety is guaranteed.
(6) Lay flexible buffer layer between reinforcing bar net and tunnel rock-wall, the buffer layer can absorb the impact energy that rock burst emergence in-process produced to slow down the impact action in the twinkling of an eye of rock burst jettison thing to the reinforcing bar net, avoid reinforcing bar net breaking occur under strong impact, can show improvement supporting construction's rock burst protective effect.
Drawings
FIG. 1 is a schematic structural diagram of a weak rockburst zone control scheme;
FIG. 2 is an expanded view of FIG. 1;
FIG. 3 is a schematic illustration of the construction of an NPR bolt and a small bore pressure relief hole;
FIG. 4 is a schematic diagram of a medium rock burst zone control scheme;
FIG. 5 is an expanded view of FIG. 4;
FIG. 6 is a schematic illustration of the construction of a small bore pressure relief vent and a large bore pressure relief vent;
FIG. 7 is a schematic structural view of an NPR anchor cable and a large-hole pressure relief hole;
FIG. 8 is a schematic view of the structure of the water injection pipe;
FIG. 9 is a schematic structural diagram of a control scheme for a strong rockburst area;
FIG. 10 is an expanded view of FIG. 9;
fig. 11 is a schematic structural view of a face pressure relief hole and a face blast hole.
Wherein: 1. a small-bore pressure relief vent; 2. c25 concrete; 3. an NPR anchor rod; 4. a reinforcing mesh; 5. a steel bar ladder; 6. an NPR anchor rod body; 7. a first constant resistance device; 8. an anchor rod tray; 9. CF25 steel fiber concrete; 10. a large-aperture pressure relief hole; 11. an NPR anchor cable; 12. an NPR anchor cable body; 13. an anchor cable tray; 14. a second constant resistance device; 15. steel strand wires; 16. a water injection pipe; 17. a water outlet hole; 18. sealing the cover; 19. a W-shaped steel belt; 20. a palm surface pressure relief hole; 21. CF25 NPR steel fiber concrete; 22. NPR steel arches; 23. a flexible buffer layer; 24. and (5) blasting holes on the tunnel face.
Detailed Description
The technical solutions of the present invention will be described clearly and completely below, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "middle", "upper", "lower", "left", "right", "inner", "outer", etc. indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplification of description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The technical solution of the present invention will be described in detail with reference to the accompanying drawings in conjunction with embodiments.
Example 1
(1) Determining the intensity grade of the rock burst;
the method comprises the following steps: measuring the ground stress state of the proposed tunnel by adopting a hydraulic fracturing method, wherein the ground stress state mainly comprises the maximum horizontal stress (S) H ) Minimum horizontal stress (S) h ) And vertical stress (S) v ) And the direction of the maximum principal stress and the direction of dominance. Step two: and determining an included angle between the maximum horizontal main stress direction near the drilled hole and the axial direction of the tunnel, and calculating an included angle alpha between the maximum horizontal main stress direction and the normal stress direction on the side wall of the tunnel in the cross section of the tunnel. Step three: according to an elastic mechanics formula, the stress acting on the tunnel side wall is calculated, and the concrete formula is as follows:
σ θ ＝3σ h -σ H
in the formula: sigma H Is the tunnel axial stress, Mpa; sigma θ The maximum tangential stress of the tunnel is Mpa.
Step four: and determining the rock burst grade according to the rock burst Russense criterion, and partitioning. Russense criterion utilizes the maximum tangential stress (sigma) of the tunnel chamber θ ) Uniaxial compressive strength (sigma) of surrounding rock c ) Is determined by the ratio of (a). As follows:
the tunnel rockburst level can be judged and partitioned according to the criterion.
(2) Different prevention and control schemes are adopted for different rock burst grade areas;
as shown in fig. 1-2, the specific control scheme for weak rockburst areas is as follows: the method comprises the following steps: and immediately spraying C25 concrete 2 to perform primary reinforcement on the tunnel surrounding rock after the tunnel face is tunneled, wherein the thickness of the sprayed concrete is 20 cm. Step two: drilling an anchor rod drilling hole, wherein the diameter of the anchor rod drilling hole is 25mm, and the depth of the anchor rod drilling hole is 5000 mm; and then reaming the anchor rod drill hole within 1100-1200 mm of the tunnel wall, wherein the reaming diameter is 72-75 mm, the reaming depth is 1100-1200 m, and the expanded hole is the small-aperture pressure relief hole 1. Step three: hanging a reinforcing mesh 4 with the diameter of phi 6mm, wherein the mesh spacing is 20x20 cm; then installing an NPR anchor rod 3 in the anchor rod drilling hole, and connecting a row of anchor rods vertical to the tunneling direction by a steel bar ladder 5; during installation, the anchor rod tray 8 needs to press the reinforcing mesh 4 and the reinforcing ladder 5. The diameter of the NPR anchor rod body 6 is 22mm, and the length of the anchor rod is 5000 mm; as shown in fig. 3, the first constant-resistance device 7 of the NPR anchor rod 3 is installed in the small-aperture pressure relief hole 1, and the diameter of the first constant-resistance device 7 is 32mm, so that a pressure yielding space of 20-21.5 mm is reserved between the first constant-resistance device 7 and the small-aperture pressure relief hole 1 in the tangential direction of the tunnel; the constant resistance of the first constant resistance device 7 is 140-180 kN, and the maximum extension is 1000mm, so that under the condition of the maximum extension, the first constant resistance device 7 and the small-aperture pressure relief hole 1 have a yielding space of 100-200 mm in the radial direction of the tunnel. Step four: and after the reinforcing mesh 4, the NPR anchor rods 3 and the reinforcing steel bar ladder 5 are installed, C25 concrete 1 is adopted to carry out re-spraying on the surrounding rock, and the thickness of the re-sprayed concrete is 40 cm.
As shown in fig. 4-5, the medium rock burst area adopts a coupled control scheme of 'pressure relief-support-softening' with 'large and small aperture combined pressure relief + NPR anchor rods + NPR anchor cables + face pressure relief holes + water injection in anchor cable drill holes' as a main body. The specific control scheme is as follows: the method comprises the following steps: immediately after the tunnel face is tunneled, CF25 steel fiber concrete 9 is sprayed to primarily reinforce the tunnel surrounding rock, and the thickness of the sprayed concrete is 20 cm. Step two and step three are the same as step two and step three in the weak rockburst area prevention scheme, and are not repeated here; step four: and drilling an anchor cable drill hole, wherein the diameter of the anchor cable drill hole is 35mm, the depth of the anchor cable drill hole is 10000mm, then reaming is carried out on the anchor cable drill hole within 1500-1800 mm of the tunnel hole wall, the reaming diameter is 125-130 mm, the reaming depth is 1500-1800 mm, and the expanded hole is the large-aperture pressure relief hole 10. A schematic of the structure of the small pore size pressure relief vent 1 and the large pore size pressure relief vent 10 is shown in fig. 6. Step five: installing NPR anchor cables 11 in anchor cable drill holes, connecting a row of anchor cables vertical to the tunneling direction by using W-shaped steel belts 19, and pressing a reinforcing mesh 4 and the W-shaped steel belts 19 by using anchor cable trays 13 during installation, wherein the NPR anchor cables 11 are arranged between two rows of NPR anchor rods 3 as shown in figure 5; as shown in fig. 8, the NPR anchor cable 11 is a hollow anchor cable with a diameter of 29mm, the length of the NPR anchor cable body 12 is 10000mm, a water injection pipe 16 is wrapped in a steel strand 15 of the NPR anchor cable 11, the outer diameter of the pipe body is 10mm, the inner diameter of the pipe body is 7.5mm, water outlet holes 17 are formed in positions corresponding to the water injection pipe 16 and the steel strand 15, and 4 water outlet holes are formed at intervals of 1 m; as shown in fig. 7, the second constant-resistance device 14 of the NPR anchor cable 11 is installed in the large-aperture pressure relief hole 10, and the diameter of the second constant-resistance device 14 is 75mm, so that a yielding space of 25-27.5 mm is left between the second constant-resistance device 14 and the large-aperture pressure relief hole 10 in the tangential direction of the tunnel; the constant resistance of the second constant resistance device 14 is 320kN, and the maximum extension is 1400mm, so that under the condition of the maximum extension, the second constant resistance device 14 and the large-aperture pressure relief hole 10 have a yielding space of 100-400 mm in the radial direction of the tunnel. Step six: after the reinforcing mesh 4, the NPR anchor rods 3 and the NPR anchor cables 11 are installed, carrying out re-spraying on the surrounding rock by using CF25 steel fiber concrete 9, wherein the thickness of the re-sprayed concrete is 40 cm. Step seven: injecting water into the anchor cable drill hole, injecting water into the anchor cable drill hole through a water outlet hole 17 of a water injection pipe 16, wherein a wetting agent needs to be added into the injected water to enhance the rock mass wetting effect, and the water is injected for 2-3 h/time, and 10-15L of water is injected each time; so that the anchor cable drill hole is wetted by water, thereby softening the rock mass, and after the water injection is finished, a sealing cover 18 is covered. Step eight: when the tunnel face is tunneled to a position 30m in front of a medium rock burst area, drilling tunnel face pressure relief holes 20 in the tunnel face along the tunneling direction, wherein the tunnel face pressure relief holes 20 are parallel to the tunneling direction, the diameter of each tunnel face pressure relief hole is 130mm, and the depth of each tunnel face pressure relief hole is 20-30 m; as shown in fig. 11, the tunnel face pressure relief holes 20 are arranged at the midpoint of a connecting line between the center of the bottom plate and the inner wall of the roadway, 7 tunnel face pressure relief holes 20 are arranged, the tunnel face pressure relief holes 20 are arranged on the tunnel face in a fan shape, and an included angle between the circle center of each two adjacent tunnel face pressure relief holes 20 and the connecting line between the centers of the bottom plates is 22.5 °.
As shown in fig. 9-10, the strong rockburst region adopts a coupled control scheme of 'pressure relief-support-softening' with 'large and small aperture combined pressure relief + NPR anchor rods + NPR anchor cables + flexible buffer layers + NPR steel arches + tunnel face pressure relief holes and blast holes + anchor cable drill holes injected with water' as a main body. The specific control scheme is as follows: the method comprises the following steps: immediately after tunnel face tunneling, CF25 NPR steel fiber concrete 21 is sprayed to primarily reinforce the tunnel surrounding rock, and the thickness of the sprayed concrete is 20 cm. Step two is the same as step two in the weak rockburst area prevention and control scheme, and the description is omitted here; the third step is basically the same as the third step in the weak rockburst area prevention and control scheme, and the only difference is that a flexible buffer layer 23 is paved before the reinforcing mesh 4 is paved, wherein the flexible buffer layer is a glass wool felt with the thickness of 200 mm; step four: drilling anchor cable drill holes, wherein the diameter of each anchor cable drill hole is 35mm, the depth of each anchor cable drill hole is 10000mm, then reaming is carried out on the anchor cable drill holes within 2000-2300 mm of the tunnel wall, the reaming diameter is 125-130 mm, the reaming depth is 2000-2300 mm, and the expanded holes are large-aperture pressure relief holes 10. Step five is the same as the step five of the control scheme of the medium rock burst area, and is not described again here, and the only difference is that the maximum extension of the constant resistance device is 1900 mm. Step six: and erecting NPR steel arches 22, wherein the distance between the NPR steel arches 22 is 0.5-1 m, and the adjacent NPR steel arches 22 are connected by adopting welded U-shaped deformed steel bars. Step seven: after the reinforcing mesh 4, the NPR anchor rods 3, the NPR anchor cables 11 and the NPR steel arch frame 22 are installed, the CF25 NPR steel fiber concrete 21 is adopted to carry out re-spraying on the surrounding rock, and the thickness of the re-sprayed concrete is 40 cm. Step eight: injecting water into the anchor cable drill hole for 2-3 h/time, wherein 20-30L of water is injected each time; step nine: when the tunnel face is tunneled to the position 30m in front of the strong rock burst area, drilling a tunnel face pressure relief hole 20 and a tunnel face blast hole 24 on the tunnel face along the tunneling direction; the face pressure relief holes 20 and the face blast holes 24 are parallel to the tunneling direction, the diameter of the face pressure relief holes 20 is 130mm, and the depth of the face pressure relief holes is 20-30 m; the diameter of the tunnel face blast hole 24 is 94mm, and the depth is 20-30 m; as shown in fig. 11, the arrangement of the face pressure relief holes 20 is the same as the arrangement of the face pressure relief holes 20 in the medium rock burst area prevention and treatment scheme; the face surface blasting holes 24 are distributed at 5/8 positions of the connecting line length of the center of the bottom plate and the inner wall of the roadway, 8 blasting holes are distributed in total, the face surface blasting holes 24 are distributed on the face surface in a fan shape, and the connecting line included angle between the circle centers of two adjacent blasting holes and the center of the bottom plate is 22.5 degrees; the explosive loading in the blast hole is not lower than 15 kg/hole, the length of the blast hole sealing is not less than 5m, and the blasting is initiated at one time.
The method has important practical significance and social benefit in the aspects of ensuring safe construction of high-stress tunnel engineering, saving production cost, improving economic benefit and the like, and has wide application prospect.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (7)
1. A tunnel rock burst grading prevention and control method by utilizing NPR material is characterized in that,
aiming at weak rockburst areas, the prevention and control method comprises the following steps: firstly, spraying concrete for the first time; drilling an anchor rod drill hole, and then reaming the anchor rod drill hole to form a small-aperture pressure relief hole; thirdly, hanging a reinforcing mesh, then installing NPR anchor rods in the anchor rod drill holes, and connecting a row of NPR anchor rods vertical to the tunneling direction by using a reinforcing steel bar ladder; fourthly, re-spraying concrete;
aiming at the medium rockburst area, the control method comprises the following steps: firstly, primarily spraying steel fiber concrete; drilling an anchor rod drill hole, and then reaming the anchor rod drill hole to form a small-aperture pressure relief hole; thirdly, hanging a reinforcing mesh, then installing NPR anchor rods in the anchor rod drill holes, and connecting a row of NPR anchor rods vertical to the tunneling direction by using a reinforcing steel bar ladder; drilling anchor cable drill holes, and then reaming the anchor cable drill holes to form large-aperture pressure relief holes; installing NPR anchor cables in the anchor cable drill holes, and connecting a row of anchor cables vertical to the tunneling direction by adopting W-shaped steel belts; step six, re-spraying steel fiber concrete, injecting water into the anchor cable drill hole through the NPR anchor cable to soften the rock mass, and finally drilling a tunnel face pressure relief hole;
aiming at a strong rockburst area, the prevention and control method comprises the following steps: firstly, NPR steel fiber concrete is sprayed primarily; drilling an anchor rod drill hole, and then reaming the anchor rod drill hole to form a small-aperture pressure relief hole; thirdly, laying a flexible buffer layer and a reinforcing mesh, then installing NPR anchor rods in the anchor rod drill holes, and connecting a row of NPR anchor rods vertical to the tunneling direction by using a reinforcing steel bar ladder; drilling anchor cable drill holes, and then reaming the anchor cable drill holes to form large-aperture pressure relief holes; installing NPR anchor cables in the anchor cable drill holes, and connecting a row of anchor cables vertical to the tunneling direction by adopting W-shaped steel belts; step six, erecting an NPR steel arch frame; step seven, repeatedly spraying NPR steel fiber concrete, injecting water into the anchor cable drill hole through the NPR anchor cable to soften the rock mass, and finally drilling a face pressure relief hole and a face blast hole;
the NPR anchor rope is a hollow anchor rope, a water injection pipe is arranged in the middle of the anchor rope, and water outlet holes are formed in the positions, corresponding to the NPR anchor rope and the water injection pipe, of the NPR anchor rope.
2. The method of claim 1, wherein the NPR anchor rod comprises a first constant resistance device, the first constant resistance device is installed in the small-bore pressure relief hole, the first constant resistance device and the small-bore pressure relief hole are coaxial, and the diameter of the small-bore pressure relief hole is larger than that of the first constant resistance device; the depth of the small-bore pressure relief hole is greater than the length of the first constant resistance device.
3. The method of claim 1, wherein the NPR anchor rope comprises a second constant resistance device, the second constant resistance device is mounted in the large-aperture pressure relief hole, the second constant resistance device and the large-aperture pressure relief hole are coaxial, and the diameter of the large-aperture pressure relief hole is larger than that of the second constant resistance device; the depth of the large-aperture pressure relief hole is greater than the length of the second constant resistance device.
4. The method for the graded control of the rock burst of the tunnel by using the NPR material as claimed in claim 2, wherein the difference between the diameters of the small-bore pressure relief hole and the first constant resistance device is 40-43 mm.
5. The method for the graded control of the rock burst of the tunnel by using the NPR material as claimed in claim 3, wherein the difference between the diameters of the large-aperture pressure relief hole and the second constant-resistance device is 50-55 mm.
6. The method as claimed in claim 1, wherein the pressure relief holes are arranged at the midpoint of the connecting line between the center of the bottom plate and the inner wall of the roadway, and the pressure relief holes are arranged on the tunnel face in a fan shape.
7. The method as claimed in claim 1, wherein the face blast holes are arranged at 5/8 of the length of the connecting line between the center of the bottom plate and the inner wall of the tunnel, and the face blast holes are arranged on the face in a fan shape.
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