Method for treating collapse of weak surrounding rock in tunnel fracture zone in complex mountainous area

Abstract

The invention relates to the technical field of tunnel engineering, and discloses a complex mountainous area tunnel fracture zone weak surrounding rock collapse processing method, which comprises the following steps: carrying out geological forecast through a geophysical prospecting and drilling combined mode to identify the development conditions of geology and underground water in front of a tunnel construction direction; weep holes are formed in arch feet of the left side and the right side of the tunnel face in the construction direction, and gate valves are installed at hole openings of the weep holes; the soft water-rich rock mass in the front is consolidated through an advanced pre-reinforcement grouting technology; a three-step core soil reserving method is adopted for excavation, an upper pilot tunnel is excavated in the circumferential direction, concrete is initially sprayed immediately after excavation, a steel frame is arranged, and then anchors, sprayers and nets are constructed; repeating the pre-reinforcement grouting technology and the excavation step of the three-step core soil reserving method until passing through the collapse section; according to the treatment method, risks caused by collapse, initial support deformation arch replacement and the like and time consumed for treatment are prevented, risks caused by collapse and later initial support deformation limit invading arch replacement are prevented, the construction progress is accelerated, and the cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel engineering, and in particular to a method for processing soft surrounding rock collapse in a broken zone of a tunnel in a complex mountain area. Background Art

[0002] In recent years, soft rock tunnels (also called weak surrounding rock tunnels) account for a high proportion in some complex mountain tunnel construction projects, and the length and span of the tunnels are getting larger and larger, and a large number of tunnels are still in special geology.

[0003] For example, the faces of some tunnels are mainly composed of tuff, mixed with a small amount of strongly weathered basalt. The basalt is affected by the structure, the rock mass is extremely broken, and it has experienced multiple eruptions. The proportion of tuff is high, the differential weathering is large, and the micro-geological changes are frequent. In complex mountainous areas, the long-term infiltration of gully water has aggravated the erosion and weathering of the surrounding rock, resulting in the deterioration of the surrounding rock. The tuff is soft and softens significantly when it comes into contact with water. The groundwater is strongly developed, and water flows out in multiple strands and rain-like forms. The rock mass is extremely broken and has poor self-stabilization ability. In addition, the distribution of bedrock fissure pressure water and underground river influence zones in the tunnel construction area are prominent hydrogeological problems. The tunnel underground hydraulic connection is obvious and the groundwater is abundant. Therefore, during the entire construction process, there is a large risk of landslides and initial support deformation intrusion, resulting in slow construction progress and high construction safety risks. Summary of the invention

[0004] The present invention proposes a method for handling collapse of soft surrounding rock in a broken zone of a tunnel in a complex mountainous area to address the deficiencies in the above-mentioned prior art. The method for handling collapse of soft surrounding rock in a broken zone can prevent the risks of collapse and the subsequent initial support deformation and intrusion into the limited arch replacement, thereby accelerating the construction progress and ensuring construction safety.

[0005] The technical solution of the present invention is: a method for processing soft surrounding rock collapse in a broken zone of a tunnel in a complex mountainous area, comprising the following steps: S1: Geological prediction is carried out through geophysical exploration combined with drilling to identify the development of geology and groundwater ahead of the tunnel construction direction.

[0006] S2: Drain holes are drilled at the arch feet on the left and right sides of the face toward the construction direction, and gate valves are installed at the mouths of the drain holes for advance water and pressure relief.

[0007] S3: Combined with the geological forecast in S1 showing the weak geological range ahead, the soft and water-rich rock mass ahead of the tunnel face is consolidated in advance through the advanced pre-reinforcement grouting technology.

[0008] S4: Adopt the three-step reserved core soil method for excavation, excavate the upper pilot pit in a circular manner, spray concrete immediately after excavation, set up the steel frame after the initial spraying, and then apply the anchor spraying net system support.

[0009] S5: Repeat the above steps S3 and S4 until the landslide section is passed.

[0010] In at least one embodiment of the present invention, if a collapse has occurred before step S2 is executed, the tunnel muck is transported in reverse to backfill the face, the cavity is filled with sandbags or block stones, a steel mesh is arranged on the surface of the collapsed body, and shotcrete is used for sealing. Steel flower pipes are arranged in the collapsed body to drain seepage water.

[0011] In at least one embodiment of the present invention, after step S2 is completed, for the defects of large initial support deformation and existing cracks, the deformed section is temporarily reinforced with an arch.

[0012] In at least one embodiment of the present invention, in step S2, the drainage holes at the arch feet on the left and right sides of the face are inclined towards the outside of the tunnel. The included angle between the drainage holes and the tunnel length direction is 8° - 12°, and the length of the drainage holes is 30m - 40m.

[0013] In at least one embodiment of the present invention, during the construction of step S3, the geological conditions in the front of the construction direction are further detected. If a cavity is found, the cavity is backfilled with concrete.

[0014] In at least one embodiment of the present invention, when step S4 is implemented, locking anchor pipes are erected on both sides of the steel frame for local strengthening, I-beams are added above the arch feet of the middle bench, and longitudinal connection of the arch frames is carried out.

[0015] In at least one embodiment of the present invention, in step S3, the advanced pre-reinforcement grouting technology means that an advanced first pipe shed is constructed at the arch of the face and a second pipe shed is drilled. Subsequently, cement slurry is used for high-pressure grouting to consolidate the front of the face in advance.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The present invention aims at surrounding rocks that are soft, water-rich, and have a high risk of large collapses and initial support deformation exceeding the limit. Through the method of combining geophysical exploration with drilling, geological advanced comprehensive forecasting is carried out to provide a basis for subsequent systematic grouting reinforcement. Subsequently, through targeted local support strengthening for the weak areas shown by the geological forecast, as well as the method of advanced pre-reinforcement plus advanced comprehensive forecasting, the soft, broken, and water-rich rock mass is compacted, and the soft, water-rich rock mass in front of the face is pre-consolidated. The method for dealing with collapses in soft surrounding rocks in the fracture zone reduces the risks brought by collapses and initial support deformation, makes the entire tunnel excavation process stable, fully ensures construction safety, and at the same time saves the time consumed by operations such as arch replacement, and overall speeds up the construction progress.

[0017] 2. The present invention strengthens locally by erecting locking anchor pipes on both sides of the steel frame, adds I-beams above the arch feet of the middle bench, and conducts longitudinal connection of the arch frames. Through the above measures, the overall stiffness and stability of the steel frame connection are enhanced, and the risks of initial support deformation and cracking are reduced, fully ensuring construction safety.

[0018] 3. The present invention can effectively prevent the initial support from deforming excessively and encroaching on the limit before being closed into a ring by strengthening the temporary arch support for the sections with large initial support deformation and cracks. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a front view structural schematic diagram of the advanced drilling and water drainage construction of the present invention.

[0020] Figure 2 It is a longitudinal section structural schematic diagram of the advanced drilling and water drainage construction of the present invention.

[0021] Figure 3 It is a plan structural schematic diagram of the advanced drilling and water drainage construction of the present invention.

[0022] Figure 4 It is a front view structural schematic diagram of the advanced pre - reinforcement of the present invention.

[0023] Figure 5 It is a longitudinal section structural schematic diagram of the advanced pre - reinforcement of the present invention.

[0024] Figure 6 It is a sectional structural schematic diagram of the construction of the three - bench method with a reserved core soil of the present invention.

[0025] Figure 7 It is a longitudinal section structural schematic diagram of the construction of the three - bench method with a reserved core soil of the present invention.

[0026] Description of the reference numerals: 1. Tunnel center line; 2. Drainage hole; 3. First pipe shed; 4. Second pipe shed; 5. Steel frame; 6. Shotcrete; 7. Upper bench circular excavation; 8. Upper bench initial support; 9. Core soil. DETAILED DESCRIPTION OF THE INVENTION

[0027] The drawings in the present invention are not strictly drawn according to the actual ratio, and the specific dimensions and quantities of each structure can be determined according to actual needs. The drawings described in the present invention are only structural schematic diagrams.

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0029] Unless otherwise defined, the technical terms or scientific terms used herein shall have the ordinary meanings as understood by those of ordinary skill in the art to which the present invention pertains. The "first", "second" and similar terms used in the present invention do not denote any order, quantity or importance, but are only used to distinguish different components. Words such as "comprising" or "including" mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects. "Inside", "outside", "above", "below", "far", "near", "front", "back", etc. are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0030] Combined with Figures 1 to 7 As shown, a method for treating the collapse of soft surrounding rock in the broken zone of a tunnel in a complex mountainous area includes: S1: Advanced comprehensive prediction: Geological prediction is carried out by combining geophysical exploration and drilling to identify the geological and groundwater development conditions in front of the tunnel construction direction; Generally, only one method such as advanced horizontal drilling, seismic wave reflection or geological radar can be used for geological and groundwater exploration. In the present invention, due to the complex geology and water inrush, comprehensive prediction measures are taken for prediction; to provide a basis for subsequent systematic grouting reinforcement.

[0031] S2: As shown in the appendix Figures 1 to 3 As shown, advanced water drainage: Drainage holes 2 are drilled at the arch feet on the left and right sides of the heading face towards the construction direction, and a gate valve is installed at the orifice of the drainage holes 2 for advanced water drainage and pressure relief.

[0032] S3: As shown in the appendix Figures 4 to 5 As shown, advanced pre - reinforcement: Combining the geological weak range shown in the geological prediction in S1, through the advanced pre - reinforcement grouting (double - layer pipe shed) technology, parameters such as the length and angle of the pipe shed are adjusted, and 1:1 cement slurry (1:1 refers to the mass ratio of cement to water) is used. High - pressure grouting is carried out in advance to grout and consolidate the front of the heading face, and the soft, broken and water - rich rock mass is compacted to achieve the advanced consolidation of the soft, water - rich rock mass in front of the heading face. During subsequent excavation, both the excavation safety and the project implementation progress are ensured. The appendix Figure 5 is a schematic layout diagram of the shotcrete 6, the first pipe shed 3, the second pipe shed 4 and the steel frame 5.

[0033] S4: As shown in the appendix Figures 6 to 7 As shown, the three - bench reserved core - soil method is adopted for excavation. The upper - level pilot tunnel is excavated circumferentially. After excavation, shotcrete is immediately applied initially. After the initial spraying, a steel frame is erected, and then an anchor - shotcrete - mesh system support is constructed; Specifically, the appendix Figure 6 is a schematic layout diagram of the upper - bench circular excavation 7, the upper - bench initial support 8 and the core soil 9.

[0034] S5: Repeat the above steps S3 and S4 until passing through the landslide section.

[0035] As an alternative embodiment, if a landslide has occurred before step S2 is executed, the tunnel muck is transported in reverse to backfill the face, the cavity is filled with sandbags or rubble, a steel mesh is set on the surface of the landslide body, and shotcrete is used for sealing. At the same time, φ42mm steel pipe with holes (wall thickness 4mm) is arranged in the landslide body to drain seepage water.

[0036] As an alternative embodiment, after step S2 is implemented, for the defects of large deformation and cracks in the initial support, temporary arch reinforcement needs to be carried out on the deformed section to prevent the initial support from deforming too much before being closed into a ring and causing intrusion, that is, temporary supports are erected at the position where the initial support has been constructed. Specifically, the arch reinforcement uses I20 steel I-beams, the spacing of the steel frames is 100cm, the steel frames are connected by φ22mm connecting bars, and two groups of 2 φ108mm grouting steel pipes with holes for locking feet are set on each side of the middle bench arch wall of the arch reinforcement steel frame, with a length of 6m / root, and two groups of 4 φ42mm grouting steel pipes with holes for locking feet are set respectively, with a locking foot length of 4m / root, for temporary reinforcement.

[0037] As an alternative embodiment, in step S2, each of the drainage holes 2 at the arch feet on the left and right sides of the face has two; the drainage holes 2 at the arch feet on the left and right sides of the face are all inclined towards the outside of the tunnel, the included angle between the drainage holes 2 and the tunnel length direction is 8° - 12°, preferably, the included angle between the drainage holes 2 and the tunnel length direction is 10°, and the length of the drainage holes 2 is 30m - 40m; preferably, the length of the drainage holes 2 is 35m.

[0038] As an alternative embodiment, during the construction of step S3, the geological conditions in the front of the construction direction are further explored. If a cavity is found, the cavity information should be recorded in detail, and the cavity is backfilled with C20 concrete.

[0039] As an alternative embodiment, when step S4 is implemented, the locking foot anchor pipes are erected closely on both sides of the steel frame at 30cm from the arch feet of the steel frame. The locking foot anchor pipes are adjusted from the traditional 4m long φ42mm steel pipe with holes to 6m long φ108mm steel pipe for local strengthening. I18 steel I-beams are added at 50m above the arch feet of the middle bench for longitudinal connection of the arch frames. Through this measure, the overall stiffness and stability of the steel frame connection are enhanced, and the risk of initial support deformation and cracking is reduced.

[0040] As an alternative embodiment, in step S3, the advanced pre-reinforcement grouting technique refers to constructing the first advanced pipe shed 3 within a range of 150° of the arch of the heading face and drilling the second pipe shed 4. Specifically, the first pipe shed 3 is a large pipe shed with a diameter of φ108mm×8mm, and the second pipe shed 4 is a medium pipe shed with a diameter of φ76mm×5mm; subsequently, cement slurry is used for high-pressure grouting to consolidate the front of the heading face in advance. Specifically, the length of the first pipe shed 3 is 15m, the circumferential spacing is 0.3m, and the external inclination angle is not more than 6°; the second pipe shed 4 uses a φ76mm steel pipe with holes (wall thickness 5mm), the circumferential spacing is 0.3m, the longitudinal spacing is 3m, the length is 6m, and the external inclination angle is not more than 15°.

[0041] As an alternative embodiment, in step S4, the thickness of the initial shotcrete after excavation is: 3cm - 5cm. The purpose of the initial shotcrete is to temporarily seal the rock mass and reduce the shedding caused by the exposure of the rock mass due to weathering; the wire mesh on the surface of the collapse body is an 8# wire mesh with a size of 25mm×25mm, and necessary materials are embedded to prevent the shedding of the rock mass after excavation, and at the same time, it plays a buffering role when spraying concrete; the type of sprayed concrete is: C25 concrete. If the specification is too small, the stiffness is insufficient, and if the specification is too large, it is easy to cause material waste. The thickness of the C25 concrete is 10cm - 14cm; this thickness is the minimum thickness covering the steel frame and its protective layer.

[0042] Specific implementation cases of the present invention: The Wakemo Tunnel is a mountain-crossing tunnel. The regional structure in the tunnel site area is complex. It is located on the southwestern margin of the Yangtze paraplatform, a first-level tectonic unit in Sichuan Province, and belongs to the combined part of the Sichuan Basin depression zone (Ⅱ3) and the Kangdian uplift (Ⅱ2) tectonic units. The structure is mainly composed of 4 deep (major) fault zones, namely the Jinyang Fault, the Daliangshan Fault, the Heishui River Fault, and the Zemu River Fault, and the fault blocks surrounded by them. In each fault block, various faults and folds mainly developed in the north-south direction, followed by the northwest and northeast directions to varying degrees. The route crosses multiple folds and faults. The fold structure is mainly the Luoxi anticline fold structure, and the fault structure is mainly 7 faults such as the Longen Fault, the Tuoducun Fault, the Butuo (Luoxi) active fault and its secondary faults.

[0043] For the surrounding rock in the above tunnel that is soft, water-rich, and has a high risk of large collapses and initial support deformation exceeding the limit, a variety of methods such as advanced pre-reinforcement, advanced comprehensive prediction, and local support strengthening are adopted, reducing the risks and the time consumed for treatment brought about by collapses and arch replacement due to initial support deformation. The daily footage has increased from 0.6m to 1.8m, the excavation process is stable, and there is no large deformation after support. The comprehensive monthly footage has increased from 15m to 35m - 40m, and the implementation effect is remarkable. After statistics, the length of this section of soft and water-rich surrounding rock is 215m. The implementation of this construction method has shortened the construction period by nearly 100 days and indirectly saved 4.569 million yuan in costs, with remarkable economic benefits.

[0044] The above embodiments are only specific implementation manners of the present invention patent, which are used to illustrate the technical solutions of the present invention patent rather than limit them. The protection scope of the present invention patent is not limited thereto. Although the present invention patent has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that any person skilled in the art within the technical scope disclosed by the present invention can still modify the technical solutions recorded in the foregoing embodiments, or can easily think of changes, or make equivalent replacements for some of the technical features; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions implemented by the present invention patent, and should all be covered by the protection scope of the present invention.

Claims

1. A method for dealing with the collapse of soft surrounding rock in the broken zone of a tunnel in a complex mountainous area, characterized in that, It includes the following steps: S1: Conduct geological forecasting by combining geophysical prospecting with drilling to identify the geology and groundwater development in front of the tunnel construction direction; S2: Drill drainage holes towards the construction direction at the arch feet on the left and right sides of the heading face, and install gate valves at the orifice positions of the drainage holes for advanced drainage and pressure relief; S3: Combine the weak geological range shown in the geological forecasting in S1, and use the advanced pre-reinforcement grouting technology to conduct advanced consolidation on the soft and water-rich rock mass in front of the heading face; S4: Adopt the three-step method with a reserved core soil for excavation, circularly excavate the upper drift, immediately spray concrete initially after excavation, install steel frames after initial spraying, and then construct the bolt-shotcrete-mesh system for support; S5: Repeat the above steps S3 and S4 until passing through the collapse section.

2. The method for dealing with the collapse of soft surrounding rock in the broken zone of a complex mountain tunnel as described in claim 1, characterized in that, If a collapse has occurred before the execution of step S2, reverse the tunnel muck to backfill the heading face, fill the cavity with sandbags or boulders, set up a steel mesh on the surface of the collapsed body, spray concrete for sealing, and arrange steel pipe with holes in the collapsed body to drain seepage water.

3. The method for dealing with the collapse of soft surrounding rock in the broken zone of a complex mountain tunnel as described in claim 1, wherein, After the implementation of step S2, for the sections with large initial support deformation and cracks, conduct temporary arch reinforcement.

4. A method for dealing with the collapse of soft surrounding rock in the broken zone of a complex mountain tunnel as described in claim 1, characterized in that, In step S2, the drainage holes at the arch feet on the left and right sides of the heading face are inclined towards the outside of the tunnel, the included angle between the drainage holes and the tunnel length direction is 8° - 12°, and the length of the drainage holes is 30m - 40m.

5. The method for dealing with the collapse of soft surrounding rock in the broken zone of a complex mountain tunnel as described in claim 1, characterized in that, During the construction of step S3, further detect the geological conditions in front of the construction direction. If cavities are found, backfill the cavities with concrete.

6. A method for treating the collapse of soft surrounding rock in the broken zone of a complex mountain tunnel as described in claim 1, characterized in that, When implementing step S4, install locking foot anchor pipes on both sides of the steel frame for local strengthening, add I-beams above the arch feet of the middle step, and conduct longitudinal connection of the arch frames.

7. The method for treating collapse of soft surrounding rock in fractured zones of complex mountain tunnels as claimed in claim 1, wherein In step S3, the advanced pre-reinforcement grouting technology refers to constructing an advanced first pipe shed at the arch of the heading face and drilling a second pipe shed, and then using cement slurry for high-pressure grouting to conduct grouting consolidation in front of the heading face in advance.

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