Construction method of soft rock roadway

Abstract

The invention provides a soft rock roadway construction method which comprises the following steps that a hole is drilled in a preset position of a soft rock roadway, one end of a steel pipe is driven into the drilled hole, the other end of the steel pipe is fixed to a supporting anchor rod, and a pipe shed pre-supporting system is formed; a comprehensive heading machine starts to work at the bottom of the soft rock roadway, rock mass in the soft rock roadway is excavated from the bottom to the top of the soft rock roadway, and the contour of the soft rock roadway is formed; hollow grouting anchor rods are adopted, grout is injected into the anchor rods, and the soft rock roadway is reinforced; primary concrete spraying is conducted on the section of the soft rock roadway at the first preset distance of the lagging tunneling working face, secondary concrete spraying is conducted on the section of the soft rock roadway at the second preset distance of the lagging tunneling working face, a concrete terrace is poured, and construction of the soft rock roadway is completed. The problem that in the prior art, due to the fact that the strength of a supporting body in a soft rock roadway is limited, the roadway is in an unstable state is solved.

Description

Technical Field

[0001] The present application relates to the technical field of tunnel support, and in particular to a construction method for a soft rock tunnel. Background Art

[0002] At present, the support methods for soft rock tunnels can be summarized as passive rigid support, combined support, pressure relief support, etc. Although these support methods have achieved certain support effects in soft rock tunnels, the tunnels are always in an unstable state due to the limited strength of the support body, serious surrounding rock disturbance and damage, and high repair rate. Summary of the invention

[0003] The main purpose of the present application is to provide a construction method for a soft rock tunnel, so as to at least solve the problem in the prior art that the tunnel is in an unstable state due to the limited strength of the support body in the soft rock tunnel.

[0004] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a construction method for a soft rock tunnel is provided, comprising the following steps: drilling a hole at a preset position of the soft rock tunnel, and driving one end of a steel pipe into the drill hole, and fixing the other end of the steel pipe at a support anchor rod to form a pipe-roof pre-support system; using a comprehensive tunneling machine to start working at the bottom of the soft rock tunnel, and digging the rock mass in the soft rock tunnel from the bottom to the top of the soft rock tunnel to form the outline of the soft rock tunnel; using hollow grouting anchor rods to support the tunnel, and injecting slurry into the hollow grouting anchor rods to reinforce the soft rock tunnel; performing initial spraying of concrete on the section of the soft rock tunnel at a first preset distance from the lagging excavation working face, and performing re-spraying on the section of the soft rock tunnel at a second preset distance from the lagging excavation working face, and pouring a concrete floor to complete the construction of the soft rock tunnel.

[0005] Optionally, after forming the contour of the soft rock tunnel, the construction method further comprises: laying steel meshes on all sections of the soft rock tunnel.

[0006] Optionally, the maximum sinking amount and left-right offset of the borehole are 20 cm to 30 cm, and the borehole depth is less than or equal to 2 m.

[0007] Optionally, the slurry includes P.O42.5 grade ordinary Portland cement and grouting additives.

[0008] Optionally, the pipe rack is made of hot-rolled seamless steel pipes, the side wall thickness of the pipe rack is 3 to 6 mm, the length of each section of the pipe rack is 2 to 4 m, and the pipe ends of the pipe rack are processed into a cone shape.

[0009] Optionally, the concrete for the initial spraying and the re-spraying includes: an accelerating setting agent and a waterproofing agent.

[0010] Optionally, during the initial spraying and re-spraying of concrete, the wind pressure is controlled within a range greater than or equal to 0.4 MPa, and the water pressure is controlled within a range greater than or equal to 0.5 MPa.

[0011] Optionally, during the initial spraying and re-spraying of concrete, the angle between the spray head and the sprayed surface is controlled within a range greater than or equal to 70°, and the spraying distance is controlled within a range of 0.8 to 1.0 m.

[0012] Optionally, the thickness of the concrete floor is 300 mm to 500 mm, and the compressive strength is greater than or equal to 30 MPa.

[0013] Applying the technical solution of the present application, a hole is drilled at a preset position of the soft rock tunnel, and one end of the steel pipe is driven into the above-mentioned hole, and the other end of the above-mentioned steel pipe is fixed at the support anchor rod to form a pipe-roof pre-support system; a comprehensive tunneling machine is used to start working at the bottom of the above-mentioned soft rock tunnel, and the rock mass in the above-mentioned soft rock tunnel is excavated from the above-mentioned bottom to the top of the soft rock tunnel to form the outline of the above-mentioned soft rock tunnel; a hollow grouting anchor rod is used and slurry is injected into the above-mentioned anchor rod to reinforce the above-mentioned soft rock tunnel; the section of the above-mentioned soft rock tunnel at the first preset distance of the lagging excavation working face is sprayed with initial concrete, and the section of the above-mentioned soft rock tunnel at the second preset distance of the lagging excavation working face is sprayed again, and the concrete floor is poured to complete the construction of the above-mentioned soft rock tunnel. This method is simple to construct, and after grouting, the soft rock can be cemented into a whole, increasing the cohesion, internal friction angle and elastic modulus of the rock mass, etc., with good support effect, high surrounding rock stability, and one-time tunneling without renovation. The invention solves the problem in the prior art that the tunnel is in an unstable state due to the limited strength of the supporting body in the soft rock tunnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The drawings constituting part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0015] Figure 1 A flow chart of a soft rock tunnel construction method provided in an embodiment of the present application is shown;

[0016] Figure 2 A cross-sectional view of pipe-roof support in a construction method for a soft rock tunnel provided in an embodiment of the present application is shown;

[0017] Figure 3 A cross-sectional view of pipe-roof support in a construction method for a soft rock tunnel provided in an embodiment of the present application is shown;

[0018] Figure 4A diagram showing the processing of a lifting ring in a construction method for a soft rock tunnel provided in an embodiment of the present application is shown;

[0019] Figure 5 A schematic diagram of cutting by a multi-purpose excavator in a construction method for a soft rock tunnel provided in an embodiment of the present application is shown;

[0020] Figure 6 A structural diagram of a hollow grouting anchor rod in a construction method for a soft rock tunnel provided in an embodiment of the present application is shown;

[0021] Figure 7 A cross-sectional view of a tunnel support in a soft rock tunnel construction method provided in an embodiment of the present application is shown.

[0022] The above drawings include the following reference numerals:

[0023] 1. Hollow grouting anchor rod; 2. Pipe shed; 3. Shotcrete layer; 4. Concrete floor; 5. Lifting ring; 6. Small ring; 7. Large ring; 8. Digging machine; 11. Anchor nut; 12. W tray; 13. Steel mesh; 14. Grouting pad; 15. Sealing pad; 16. Grouting hole; 17. Grouting hole; 18. Resin medicine roll. DETAILED DESCRIPTION

[0024] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0025] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0026] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0027] As introduced in the background technology, the current support methods for soft rock tunnels can be summarized as passive rigid support, combined support, pressure relief support, etc. Although these support methods have achieved certain support effects in soft rock tunnels, the tunnels are always in an unstable state due to the limited strength of the support body, serious surrounding rock disturbance and damage, and high repair rate.

[0028] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0029] Figure 1 Flow chart of the construction method of soft rock tunnel according to the embodiment of the present application. Figure 1 As shown, the construction method includes:

[0030] Step S101, drilling a hole at a preset position of the soft rock tunnel, and driving one end of a steel pipe into the drilled hole, and fixing the other end of the steel pipe at a support anchor rod to form a pipe-roof pre-support system;

[0031] like Figure 2 and Figure 3 As shown, the first step is temporary support. The installation hole of pipe shed 2 is constructed by drilling method. The diameter of pipe shed 2 is 20-30mm larger than the diameter of steel pipe of pipe shed 2, and the circumferential center spacing of the drilling hole is 900mm. The drilling method is drilling in and out, and the maximum sinking amount and left and right offset of the drilling hole are controlled at 20cm-30cm. The drilling speed is not easy to be too fast when the drilling rig is drilling, and the normal drilling speed is switched after the drilling depth reaches 20cm. After the drilling depth reaches 2.0m, stop drilling, disassemble the drill rod as required, and return the drilling rig to its original position. The drilling sequence is from high hole position to low hole position, and the plane position of the drilling hole is strictly controlled. The pipe shed shall not invade the tunnel excavation line, and adjacent steel pipes shall not collide or interchange.

[0032] The pipe shed 2 constructed first uses the surrounding rock support in front of the working face and the support of the rear support body as the fulcrum to form a beam structure. After the surrounding rock is excavated, it can effectively prevent the surrounding rock from loosening and collapsing. The support rigidity of the pipe shed 2 is relatively large. If a roof leak occurs during construction, the collapsed debris will also fall on the upper part of the pipe shed 2, playing a buffering role.

[0033] like Figures 2 to 4 As shown, Figure 3 It is a cross-sectional view in the tunnel excavation direction X. One end of the hollow grouting anchor 1 is connected to the lifting ring 5 through the anchor nut, and the pipe rack 2 is sleeved in the lifting ring 5. Figure 4 As shown, the lifting ring includes a small ring 6 and a large ring 7. The pipe rack is sleeved in the large ring 7, and the small ring 6 is connected to the anchor nut 11.

[0034] Step S102, using a comprehensive tunneling machine to start working at the bottom of the soft rock tunnel, digging the rock mass in the soft rock tunnel from the bottom to the top of the soft rock tunnel, and forming the outline of the soft rock tunnel;

[0035] like Figure 5 As shown, the second step is excavation. Under the cover of the pipe shed, the rock mass is excavated using a multi-purpose excavator 8. The cutting head is used to first cut a groove in the lower left corner, and then the cutting head is swept across the entire tunnel section in an "S"-shaped upward cutting method. The excavation sequence is to first excavate the lower part, then the upper part, and finally brush out the tunnel outline. This method can avoid cutting from top to bottom, which can easily cause the machine body to vibrate and become unstable, causing damage to fasteners and some parts, and can also avoid cutting from top to bottom, especially when encountering hard rock, which will cause most of the weight of the machine body to be pressed on the cutting part, which will cause great damage to the cutting part and its bearings. It can also release the surrounding rock stress from the bottom of the tunnel to the upper part, and gradually reduce the stress during the stress release process, ensuring the integrity of the tunnel surface. In order to prevent the multi-purpose excavator cutting head from accidentally hitting the pipe shed, manual excavation is used at the surrounding rock 100mm close to the pipe shed.

[0036] Use the cutting head of the tunneling machine to cut a groove in the lower left corner first, and then cut upward in an S shape to brush out the outline of the tunnel. On the one hand, the surrounding rock stress can be gradually released from the bottom of the tunnel to the upper part, and the stress gradually decreases during the release process, ensuring the integrity of the tunnel surface; on the other hand, it can avoid that when cutting from top to bottom, most of the weight of the machine body is pressed on the cutting part, which will damage the cutting part and bearings.

[0037] Step S103, using hollow grouting anchor rods to support the tunnel, and injecting slurry into the hollow grouting anchor rods to reinforce the soft rock tunnel;

[0038] Step 3: Anchor net support. Figure 2 and Figure 3 As shown, after the excavation is completed, a steel mesh 13 is laid on the entire section under the cover of the pipe shed 2. The steel mesh 13 is welded with Φ6.5mm steel bars, and the mesh size is 100×100mm. Then the hollow grouting anchor rod 1 is used for support. The anchor rod specification is Φ22×2500mm hollow grouting anchor rod 1, the end is solid, the center hole diameter is Φ10mm, the length is 2000mm, and a grouting hole is left every 300mm. The spacing between the hollow grouting anchor rods 1 is 1000×900mm, and the W tray with a specification of 300×300×6mm is matched. Each hollow grouting anchor rod 1 is anchored with a section of MSK25 / 70 resin medicine roll. As shown Figure 6 As shown, the hollow grouting anchor includes an anchor nut 11, a W tray 12, a steel mesh 13, a grouting pad 14, a sealing pad 15, a grouting hole 16, a grouting hole 17 and a resin medicine roll 18.

[0039] like Figure 2As shown, at least two hollow grouting anchor rods 1 are reinforced below the pipe shed 2, and the angle between the hollow grouting anchor rods 1 and the horizontal plane is 10°, and the spacing between the setting positions of adjacent hollow grouting anchor rods 1 in the entire tunnel is 900mm. When the hollow grouting anchor rods 1 are subjected to high-pressure grouting, the slurry can fill the obvious cracks inside the rock mass, and at the same time, the closed cracks and voids are compressed under the action of high pressure, thereby compacting the rock mass as a whole, thereby increasing the elastic modulus of the rock mass and increasing the strength of the rock mass. After the hollow grouting anchor rods 1 are grouted, the slurry fills the cracks inside the rock mass, and the slurry and the rock mass crack surface produce a bonding effect, reducing the high stress at the end of the crack, thereby changing the failure mechanism of the rock mass. In addition, when the slurry fills the larger cracks in the rock mass, the stress of the rock mass is transformed from a two-dimensional stress state to a three-dimensional stress state, increasing the strength limit of the rock mass, thereby changing the failure mechanism of the rock mass.

[0040] Step S104: Initially spray concrete on the section of the soft rock tunnel at a first preset distance from the delayed excavation working face, and re-spray concrete on the section of the soft rock tunnel at a second preset distance from the delayed excavation working face, and pour concrete floor to complete the construction of the soft rock tunnel.

[0041] like Figure 7 As shown, the fourth step: spraying, pouring concrete floor 4. At about 20m behind the excavation working face, the tunnel is sprayed with an initial spray thickness of 50mm. After the initial sprayed concrete is initially solidified, the tunnel is sprayed for the second time at about 50m behind the excavation working face to form a spray layer 3 with a spray thickness of 50mm. The initial spray surface should be washed with high-pressure water before re-spraying. Figure 7 10° is the angle between the hollow grouting anchor rod 1 and the horizontal plane, and 900 is the spacing between the setting positions of adjacent hollow grouting anchor rods 1 in the entire tunnel, which is 900 mm.

[0042] A pipe-roof pre-support system is formed by drilling a hole at a preset position of the soft rock tunnel, and driving one end of the steel pipe into the drill hole, and fixing the other end of the steel pipe at the support anchor rod; a comprehensive tunneling machine is used to start working at the bottom of the soft rock tunnel, and the rock mass in the soft rock tunnel is excavated from the bottom to the top of the soft rock tunnel to form the outline of the soft rock tunnel; a hollow grouting anchor rod is used and slurry is injected into the anchor rod to reinforce the soft rock tunnel; the section of the soft rock tunnel at the first preset distance of the lagging excavation working face is sprayed with initial concrete, and the section of the soft rock tunnel at the second preset distance of the lagging excavation working face is sprayed again, and the concrete floor is poured to complete the construction of the soft rock tunnel. This method is simple to construct, and after grouting, the soft rock can be cemented into a whole, increasing the cohesion, internal friction angle and elastic modulus of the rock mass, etc. It has the characteristics of good support effect, high surrounding rock stability, and one-time tunneling without renovation. The invention solves the problem in the prior art that the tunnel is in an unstable state due to the limited strength of the supporting body in the soft rock tunnel.

[0043] In some optional embodiments, such as Figure 3 As shown, after forming the outline of the soft rock tunnel, the construction method further includes: laying steel mesh 13 on all sections of the soft rock tunnel to reinforce the sections. The maximum sinking amount and left and right offset of the drill hole are 20cm to 30cm, and the depth of the drill hole is less than or equal to 2m.

[0044] In some optional embodiments, the slurry comprises ordinary Portland cement of grade P.O42.5 and grouting additives.

[0045] In the above optional embodiment, the slurry is mainly composed of single-liquid cement slurry, which is composed of P.O42.5 grade fresh ordinary Portland cement and grouting additives. After the hollow grouting anchor is installed, each hollow grouting anchor is grouted. The main component of the grouting is ordinary Portland cement, model P.O42.5, and the additive is ACZ-2 type flow agent, which accounts for 10% of the cement dosage. The grouting amount of each hollow grouting anchor can be calculated by the formula: Q = πR 2 ILnb calculation, where R is the diffusion radius of cement slurry, I is the loss coefficient, b is the filling coefficient, L is the grouting depth, which is consistent with the grouting hole depth of the hollow grouting anchor, and n is the diffusion rate of cement slurry. After the anchor net support is completed, pull out the pipe shed backwards and remove the pipe shed lifting ring.

[0046] During the grouting process of the hollow grouting anchor, the slurry fills the cracks in the rock mass, and the water in the surrounding rock can maintain the cement slurry. When the slurry solidifies, it consolidates with the rock mass, and the filling material and the rock mass together form a new network skeleton structure. The filling material has good bonding strength. After the hollow grouting anchor is grouted, the slurry is firmly bonded to the crack surface and becomes a whole with the rock mass, effectively improving the cohesion and internal friction angle of the rock mass, thereby enhancing the strength of the rock mass.

[0047] In some optional embodiments, the pipe rack is made of hot-rolled seamless steel pipes, the side wall thickness of the pipe rack is 3 to 6 mm, the length of each section of the pipe rack is 2 to 4 m, and the pipe ends of the pipe rack are processed into cones.

[0048] In the above optional implementation, the pipe shed is made of hot-rolled seamless steel pipe φ50mm, with a wall thickness of 5mm and a length of 3m per section. The pipe end is processed into a cone shape to facilitate insertion. The number of pipe sheds in each group is 7 to 10, and the spacing between pipe sheds is 900mm. The pipe shed ring is made of φ16mm round steel, with a nut welded at one end, a small ring welded on the nut, and a large ring connected through the small ring. The diameter of the large ring is slightly larger than the diameter of the pipe shed, and the nut matches the exposed nut of the support anchor. After the drilling construction is completed, the two rings of each pipe shed are fixed from back to front on the exposed ends of the first two rows of anchors, and then the pipe shed is inserted into the installation hole through the ring. The insertion depth is greater than the length of each cycle of excavation, and it is ensured that the insertion end can bear the weight of the rock mass falling from the top before the support after the tunnel excavation. Since the surrounding rock of the soft rock tunnel is mostly aquifers, the pipe shed can not only be used as a temporary support structure, but also play the role of geological advance detection and advance diversion and water diversion. When the anchor net support is completed, the pipe shed will be dismantled and can be reused in the next cycle.

[0049] In some optional embodiments, the concrete of the initial spraying and the re-spraying comprises: an accelerating setting agent and a waterproofing agent.

[0050] In the above optional implementation, when there is an obvious water gushing point, a conduit is buried before the initial spraying to guide water. During the spraying process, the quick-setting agent and waterproofing agent are evenly added to the feed port of the spraying machine according to the specified addition amount. The addition amount of the quick-setting agent is 3-5% of the cement dosage, and the addition amount of the waterproofing agent is 5-8% of the cement dosage. During the spraying process, the wind pressure shall not be less than 0.4Mpa, the water pressure shall be 0.1MPa greater than the wind pressure, the nozzle shall be as vertical as possible to the sprayed surface, the angle shall not be less than 70°, and the nozzle shall generally be kept at 0.8-1.0m from the sprayed surface.

[0051] In some optional implementations, during the initial spraying and re-spraying of concrete, the wind pressure is controlled within a range greater than or equal to 0.4 MPa, and the water pressure is controlled within a range greater than or equal to 0.5 MPa.

[0052] In some optional implementations, during the initial spraying and re-spraying of concrete, the angle between the spray head and the sprayed surface is controlled within a range greater than or equal to 70°, and the spraying distance is controlled within a range of 0.8 to 1.0 m.

[0053] In the above optional implementation, when there is an obvious water gushing point, a conduit is buried before the initial spraying to guide water. During the spraying process, the quick-setting agent and waterproofing agent are evenly added to the feed port of the spraying machine according to the specified addition amount. The addition amount of the quick-setting agent is 3-5% of the cement dosage, and the addition amount of the waterproofing agent is 5-8% of the cement dosage. During the spraying process, the wind pressure shall not be less than 0.4Mpa, the water pressure shall be 0.1MPa greater than the wind pressure, the nozzle shall be as vertical as possible to the sprayed surface, the angle shall not be less than 70°, and the nozzle shall generally be kept at 0.8-1.0m from the sprayed surface.

[0054] In some optional embodiments, the thickness of the concrete floor is 300 mm to 500 mm, and the compressive strength is greater than or equal to 30 MPa.

[0055] In the above optional implementation mode, after the secondary grouting of the tunnel, concrete is used to cast the floor and ditch. The floor has a slope of -5‰ facing the ditch, the concrete strength is not less than C30, the concrete floor thickness is generally 300-500mm, and BR-3 waterproofing agent is added to the concrete, the amount of which is 8% of the cement amount.

[0056] Exemplarily, a hole is drilled at a preset position in a soft rock tunnel, and one end of a steel pipe is driven into the hole. The other end of the steel pipe is fixed at the support anchor to form a pipe-roof pre-support system. The maximum sinking amount and left-right offset of the hole are 20cm to 30cm. The depth of the hole is less than or equal to 2m. The pipe-roof is made of hot-rolled seamless steel pipe φ50mm, with a wall thickness of 5mm and a length of 3m per section. The pipe end is processed into a cone shape to facilitate insertion. The number of pipe-roofs in each group is 7 to 10, and the spacing between pipe-roofs is 900mm. The pipe-roof lifting ring is made of φ16mm round steel, with a nut welded at one end. The small lifting ring is welded on the nut, and the large lifting ring is connected through the small lifting ring. The diameter of the large lifting ring is slightly larger than the diameter of the pipe-roof, and the nut matches the exposed nut of the support anchor. After the drilling construction is completed, the two lifting rings of each pipe rack are fixed on the exposed ends of the first two rows of anchor rods from back to front, and then the pipe rack is inserted into the installation hole through the lifting ring. The insertion depth is greater than the excavation length of each cycle, and it is ensured that the insertion end can bear the weight of the rock mass that falls from the top before the tunnel is excavated for support; a comprehensive tunneling machine is used to start working at the bottom of the above-mentioned soft rock tunnel, and the rock mass in the above-mentioned soft rock tunnel is excavated from the above-mentioned bottom to the top of the soft rock tunnel to form the outline of the above-mentioned soft rock tunnel; hollow grouting anchor rods are used to support the tunnel, and slurry is injected into the above-mentioned hollow grouting anchor rods to reinforce the above-mentioned soft rock tunnel, and a steel mesh is laid on the full section under the cover of the pipe rack. The steel mesh is welded with Φ6.5mm steel bars and has a mesh size of 100×100mm. Then the hollow grouting anchor support is carried out. The anchor specification is Φ22×2500mm hollow grouting anchor, the end is solid, the middle hole diameter is Φ10mm, the length is 2000mm, and a grouting hole is left every 300mm. The spacing between the hollow grouting anchors is 1000×900mm, and the W tray with a specification of 300×300×6mm is matched. Each hollow grouting anchor is anchored by 1 section of MSK25 / 70 resin medicine roll. The main component of the grouting is ordinary Portland cement, model P.O42.5, the additive is ACZ-2 type flowing agent, accounting for 10% of the cement dosage; the section of the above-mentioned soft rock tunnel about 20m away from the delayed excavation working face is initially sprayed with concrete, with an initial spraying thickness of 50mm, and the section of the above-mentioned soft rock tunnel about 50m away from the delayed excavation working face is re-sprayed with a spraying thickness of 50mm, the amount of accelerator added is 3-5% of the cement dosage, and the amount of waterproofing agent added is 5-8% of the cement dosage.During the spraying process, the wind pressure shall not be less than 0.4Mpa, the water pressure shall be 0.1MPa greater than the wind pressure, the nozzle shall be as perpendicular to the sprayed surface as possible, the angle shall not be less than 70°, the nozzle shall be generally maintained at 0.8-1.0m from the sprayed surface, the wind pressure shall be controlled within the range of greater than or equal to 0.4Mpa, the water pressure shall be controlled within the range of greater than or equal to 0.5Mpa, the angle between the nozzle and the sprayed surface shall be controlled within the range of greater than or equal to 70°, the spraying distance shall be controlled within the range of 0.8-1.0m, and the concrete floor shall be poured. The thickness of the above-mentioned concrete floor is 300mm-500mm, the compressive strength is greater than or equal to 30MPa, the slope of the floor facing the ditch is -5‰, the concrete strength is not less than C30, the thickness of the concrete floor is generally 300-500mm, and BR-3 waterproofing agent is added to the concrete, the amount of which is 8% of the cement amount to complete the construction of the above-mentioned soft rock tunnel.

[0057] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0058] From the above description, it can be seen that the above embodiments of the present application achieve the following technical effects:

[0059] The construction method of the soft rock tunnel of the present application comprises the following steps: drilling a hole at a preset position of the soft rock tunnel, driving one end of a steel pipe into the drill hole, and fixing the other end of the steel pipe at a supporting anchor rod to form a pipe-roof pre-support system; using a comprehensive tunneling machine to start working at the bottom of the soft rock tunnel, and digging the rock mass in the soft rock tunnel from the bottom to the top of the soft rock tunnel to form the outline of the soft rock tunnel; using hollow grouting anchor rods to support the tunnel, and injecting slurry into the hollow grouting anchor rods to reinforce the soft rock tunnel; performing initial spraying of concrete on the section of the soft rock tunnel at a first preset distance from the lagging excavation working face, and performing re-spraying on the section of the soft rock tunnel at a second preset distance from the lagging excavation working face, and pouring a concrete floor to complete the construction of the soft rock tunnel. This method is simple to construct, and after grouting, it can cement the soft rock into a whole, increase the cohesion, internal friction angle and elastic modulus of the rock mass, etc., and has the characteristics of good support effect, high stability of surrounding rock, and one-time tunneling without renovation. It solves the problem in the prior art that the tunnel is in an unstable state due to the limited strength of the support body in the soft rock tunnel.

[0060] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A construction method for a soft rock tunnel, characterized in that: The following steps are involved: Drill a hole at a preset position in the soft rock tunnel, and drive one end of a steel pipe into the drill hole, and fix the other end of the steel pipe to the support anchor rod to form a pipe-roof pre-support system; Using a comprehensive tunneling machine to start working at the bottom of the soft rock tunnel, digging the rock mass in the soft rock tunnel from the bottom to the top of the soft rock tunnel to form the outline of the soft rock tunnel; The tunnel is supported by hollow grouting anchor rods, and grout is injected into the hollow grouting anchor rods to reinforce the soft rock tunnel; Initial concrete spraying is performed on the section of the soft rock tunnel at a first preset distance from the delayed excavation working face, and re-spraying is performed on the section of the soft rock tunnel at a second preset distance from the delayed excavation working face, and a concrete floor is poured to complete the construction of the soft rock tunnel.

2. The construction method according to claim 1, characterized in that: After forming the outline of the soft rock tunnel, the construction method further comprises: laying steel meshes on all sections of the soft rock tunnel.

3. The construction method according to claim 1, characterized in that: The maximum sinking amount and left-right offset of the borehole are 20 cm to 30 cm, and the depth of the borehole is less than or equal to 2 m.

4. The construction method according to claim 1, characterized in that: The slurry includes ordinary Portland cement of P.O42.5 grade and grouting additives.

5. The construction method according to claim 1, characterized in that: The pipe shed is made of hot-rolled seamless steel pipes, the side wall thickness of the pipe shed is 3-6 mm, the length of each section of the pipe shed is 2-4 m, and the pipe end of the pipe shed is processed into a cone shape.

6. The construction method according to claim 1, characterized in that: The concrete for the initial spraying and the re-spraying comprises: an accelerating setting agent and a waterproofing agent.

7. The construction method according to claim 6, characterized in that: The usage of the waterproofing agent accounts for 8% of the usage of cement.

8. The construction method according to claim 1, characterized in that: During the initial and re-spraying of concrete, the wind pressure is controlled within a range greater than or equal to 0.4 MPa, and the water pressure is controlled within a range greater than or equal to 0.5 MPa.

9. The construction method according to claim 1, characterized in that: During the initial and repeated spraying of concrete, the angle between the nozzle and the sprayed surface is controlled to be greater than or equal to 70°, and the spraying distance is controlled to be within the range of 0.8 to 1.0 m.

10. The construction method according to claim 7, characterized in that: The thickness of the concrete floor is 300 mm to 500 mm, and the compressive strength is greater than or equal to 30 MPa.

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