CN112963156A - Composite reinforcing method and composite reinforcing structure for shallow tunnel in soil-rock composite stratum - Google Patents
Composite reinforcing method and composite reinforcing structure for shallow tunnel in soil-rock composite stratum Download PDFInfo
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- CN112963156A CN112963156A CN202110297747.8A CN202110297747A CN112963156A CN 112963156 A CN112963156 A CN 112963156A CN 202110297747 A CN202110297747 A CN 202110297747A CN 112963156 A CN112963156 A CN 112963156A
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D9/00—Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
- E21D9/001—Improving soil or rock, e.g. by freezing; Injections
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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
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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
- E21D11/14—Lining predominantly with metal
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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
- E21D11/14—Lining predominantly with metal
- E21D11/18—Arch members ; Network made of arch members ; Ring elements; Polygon elements; Polygon elements inside arches
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D20/00—Setting anchoring-bolts
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Abstract
The invention provides a composite reinforcement method of a shallow tunnel in a soil-rock composite stratum, which sequentially comprises the steps of earth surface grouting, pipe shed support, advanced small pipe support and the like, and also provides a composite reinforcement structure of the shallow tunnel in the soil-rock composite stratum, which comprises a surface soil layer, a rock stratum and a tunnel excavation area; the tunnel excavation device is characterized in that a grouting hole group is formed in the earth surface, a surrounding rock arch part is formed above the tunnel excavation region, a plurality of large-caliber steel pipes which are obliquely arranged relative to a horizontal plane are inserted in the surrounding rock arch part, the tunnel excavation region is provided with a tunnel face, a steel arch is arranged in the tunnel excavation region, a grout stopping disc is arranged on the tunnel face, and small-caliber steel pipes which are inserted in the tunnel face are inserted in the grout stopping disc at the same time. According to the invention, the soil body strength can be improved through surface grouting, the anti-seepage performance is relatively high, and the stability and the safety before and after tunnel excavation are ensured by utilizing the combined action of reinforcement measures such as surface grouting, pipe shed support, advanced small pipe support and the like.
Description
Technical Field
The invention relates to a tunnel reinforcing method and a tunnel reinforcing structure, in particular to a composite reinforcing method and a composite reinforcing structure for a shallow tunnel in a soil-rock composite stratum.
Background
With the high-speed development of urban underground rail transit, urban tunnels show a trend of increasing year by year. For a shallow small-clear-distance tunnel buried in a city under complex geology, the earth covering buried depth is shallow, the earth covering stratum is a weak stratum and a gravel layer, the actual engineering construction problems of large ground dynamic load, strong water permeability of vault surrounding rock and the like exist, and reinforcement and support are needed.
The Chinese utility model patent with publication number CN203961998U discloses a combined primary support structure for a shallow tunnel, which comprises a cover arch section and a tunnel body support section, wherein the cover arch section is formed by a section steel frame and comprises a plurality of sections of steel arch units, the steel arch units are connected with each other through connecting steel plates and connecting bolts, and a pipe shed guide pipe is arranged at the arch back of the section steel frame; the hole body supporting section is formed by steel bar grids, the steel bar grids are connected into a whole through longitudinal connecting ribs, a layer of long pipe shed is arranged at the arch back position of each steel bar grid, the long pipe shed is shaped through finish rolling deformed steel bars, anchoring and reinforcing are carried out through anchor rods, a layer of concrete layer is formed on the inner side of each steel bar grid, and reinforcing is carried out between the concrete layer and each steel bar grid through a steel bar net. Although the supporting structure can reinforce the stratum to a certain extent, the strength of the soil body is not increased, and the seepage-proofing performance is relatively poor.
In view of the above, the applicant has conducted intensive research on a composite reinforcing method and a composite reinforcing structure for a shallow tunnel in a soil-rock composite stratum, and has generated the present application.
Disclosure of Invention
The invention aims to provide a composite reinforcing method and a composite reinforcing structure of a shallow tunnel, which can improve the strength of a complex stratum and have relatively high seepage-proofing performance.
In order to achieve the purpose, the invention adopts the following technical scheme:
a composite reinforcing method for a shallow tunnel in a soil-rock composite stratum sequentially comprises the following steps:
s1, performing surface grouting, vertically arranging a plurality of grouting holes on a surface soil layer above a shallow tunnel to be excavated to form a grouting hole group, wherein in the grouting hole group, the hole bottoms of the grouting holes positioned right above the shallow tunnel are positioned on the contour line of the shallow tunnel, then injecting mixed double grout of cement paste and water glass into the grouting holes, and filling and tamping the mouth parts of the grouting holes by adopting concrete;
s2, supporting a pipe shed, inserting a large-diameter steel pipe into a surrounding rock arch of the shallow tunnel from high to low, forming a first hole in the side wall of the large-diameter steel pipe, pressing cement slurry into the large-diameter steel pipe, and enabling part of the cement slurry to flow out of the first hole and be fixedly connected to the surrounding rock arch;
s3, advancing the support of the small guide pipe, spraying concrete to seal the tunnel face of the shallow tunnel and form a grout stopping disc on the tunnel face, then forming a plurality of support holes in the grout disc from high to low, penetrating small-caliber steel pipes into the support holes, supporting the small-caliber steel pipes on a steel arch frame, forming second holes in the side walls of the small-caliber steel pipes, pressing grout into the small-caliber steel pipes, and enabling part of the grout to flow out of the second holes and be solidified.
As an improvement of the present invention, in step S1, before injecting the mixed grout of cement paste and water glass into each grouting hole, a grouting pipe is inserted into each grouting hole, the lower end of the grouting pipe is sealed, a grout stop plug is sleeved outside the grouting pipe, a plurality of grout overflow holes are formed in the side wall of the grouting pipe at a position below the grout stop plug, and when injecting the mixed grout of cement paste and water glass into each grouting hole, the grouting pipe is grouted by performing low-pressure slow-permeation and then high-pressure grouting.
In step 1, when injecting the mixed double grout of cement paste and water glass into each grouting hole, alternate grouting is adopted.
As an improvement of the invention, the following steps are carried out after the tunnel excavation:
and S4, primary support, namely performing spray anchor support on the surrounding rock of the shallow tunnel, wherein anchor rods adopted by the spray anchor support are hollow grouting anchor rods and mortar anchor rods.
In step S4, a wet shotcrete is used to perform a primary shotcrete on the surrounding rock, and the mesh reinforcement is laid after the thickness of the primary shotcrete reaches 3-5cm, so that the mesh reinforcement and the shotcrete are integrated.
A composite reinforced structure of a soil-rock composite stratum shallow tunnel comprises a surface soil layer, a rock stratum located below the surface soil layer and a tunnel excavation area located on the surface soil layer and the rock stratum simultaneously;
the ground surface is provided with a grouting hole group, the grouting hole group comprises a plurality of grouting holes which are vertically arranged respectively, the hole bottoms of the grouting holes positioned right above the tunnel excavation area are positioned on the contour line of the tunnel excavation area, the hole bottoms of other grouting holes are positioned on the boundary line between the ground surface layer and the rock stratum, and each grouting hole is filled with double grout mixed by cement paste and water glass;
a surrounding rock arch part is formed above the tunnel excavation area, a plurality of large-diameter steel pipes which are obliquely arranged relative to the horizontal plane are inserted into the surrounding rock arch part, a first hole is formed in the side wall of each large-diameter steel pipe, and cement slurry is filled in each large-diameter steel pipe;
the tunnel excavation region has a face, just the tunnel excavation region is provided with the steel bow member, the steel bow member is fixed through locking the foot stock, be provided with on the face and end the thick liquid dish, it has the simultaneous interlude to end to alternate on the thick liquid dish small-bore steel pipe in the face, small-bore steel pipe supports on the steel bow member simultaneously, the second punchhole has been seted up on the lateral wall of small-bore steel pipe, just the small-bore steel intraductal packing has grout.
As an improvement of the invention, a grouting pipe is inserted into each grouting hole, the lower end of the grouting pipe is sealed, a grout stop plug is sleeved outside the grouting pipe, a plurality of grout overflow holes are formed in the position, below the grout stop plug, of the side wall of the grouting pipe, and the position, below the grout stop plug, between the grouting pipe and the grouting hole and inside the grouting pipe, of the grout and water glass mixed double grout is filled.
As an improvement of the invention, the grout stopping plug is a grout stopping film bag.
As an improvement of the present invention, on the cross section of the tunnel excavation region, two rays are made which are symmetrical with respect to the center line of the contour of the tunnel excavation region, taking the intersection point between the center line of the contour of the tunnel excavation region and the tunnel lower contour line of the tunnel excavation region as an origin, when the included angle between the two rays is 60 °, the region corresponding to the region formed between the surrounding rock arch and the two rays is the layout range of the large-caliber steel pipe, and when the included angle between the two rays is 120 °, the region corresponding to the region formed between the grout stopping disk and the two rays is the layout range of the small-caliber steel pipe.
By adopting the technical scheme, the invention has the following beneficial effects:
1. according to the invention, on the basis of the pipe shed support, the soil body strength can be improved through surface grouting, the seepage-proofing performance is relatively high, and the stability and the safety before and after tunnel excavation are ensured by utilizing the combined action of reinforcement measures such as surface grouting, pipe shed support, advanced small conduit support and the like.
2. Aiming at the problems of shallow buried depth of the covering soil and the like, double-liquid high-pressure grouting is adopted for the ground surface, the strength and the seepage-proofing level of the soil body around the vault are improved, and meanwhile, the influence of the upper load of the tunnel on the tunnel structure is reduced.
3. The forepoling and the preliminary bracing form a whole by mutually welding and spraying concrete, the settlement of the surrounding rock in the surrounding rock excavation process is strictly controlled, the preliminary self-supporting capability of the tunnel surrounding rock is fully exerted, and collapse caused by excavation disturbance is avoided.
4. The whole composite grouting reinforcement measure effectively controls the influence of the upper load of the tunnel on the surrounding rock and the structure of the tunnel, and improves the stability of the tunnel structure.
Drawings
FIG. 1 is a schematic cross-sectional view of an exemplary composite reinforcing structure;
FIG. 2 is a schematic cross-sectional view of surface grouting in an example;
FIG. 3 is a schematic diagram of a fitting structure between a grouting hole and a grouting pipe in the embodiment;
FIG. 4 is a schematic diagram of a layout structure of a large-diameter steel pipe in the embodiment;
FIG. 5 is a schematic view of a connection structure of a large-diameter steel pipe in the embodiment;
FIG. 6 is a schematic view of the layout structure of small-caliber steel pipes in the example;
FIG. 7 is a schematic view of a connection structure of small-caliber steel pipes in an embodiment;
the designations in the figures correspond to the following:
10-a surface soil layer; 11-grouting holes;
12-grouting pipes; 13-stop plug;
14-slurry overflow hole; 15-large diameter steel pipe;
16-small-caliber steel pipes; 20-a rock formation;
30-tunnel excavation area; 31-tunnel upper contour line;
32-tunnel lower contour line; 50-locking the anchor rod.
Detailed Description
The invention is further described with reference to the following figures and specific embodiments.
As shown in fig. 1 and with reference to fig. 2-7, the present embodiment provides a composite reinforced structure of a shallow tunnel in an earth-rock composite stratum, comprising a surface soil layer 10, a rock layer 20 located below the surface soil layer 10, and a tunnel excavation region 30 located on both the surface soil layer 10 and the rock layer 20, wherein the tunnel excavation region 30 is excavated to form a shallow tunnel, the side wall of the shallow tunnel is located to form the contour of the tunnel excavation region 30, the contour line of the tunnel excavation region 30 includes an arched tunnel upper contour line 31 and a U-shaped tunnel lower contour line 32, the tunnel upper contour line 31 is located above the tunnel lower contour line 32, and both ends of the tunnel upper contour line 31 are connected with both ends of the tunnel lower contour line 32 one-to-one to-form a closed loop line, of course, the specific shapes of the tunnel upper contour line 31 and the tunnel lower contour line 32 can be adjusted according to actual needs. A surrounding rock arch is formed above the tunnel excavation region 30, the definition of the surrounding rock arch is the same as that in conventional tunnel construction, and the surrounding rock arch is located above the tunnel upper contour line 31 and at a position directly contacting the tunnel upper contour line 31 as viewed from the cross section of the tunnel excavation region 30, and belongs to a part of the surface soil layer 10. In addition, the tunnel excavation region 30 has a tunnel face, which is also called tunnel face, and the specific definition of the tunnel face is the same as that in tunnel construction, and is a vertical working face for excavating tunnels and continuously pushing forwards; the tunnel excavation region 30 is further provided with a plurality of steel arches (not shown in the drawings) sequentially arranged in the depth direction of the excavated region in the tunnel excavation region 30, the steel arches are fixed by the foot-locking anchor rods 50, and the structures and relative positional relationships of the excavation region 30, the surrounding rock arches, the tunnel face, and the steel arches are the same as those in the conventional tunnel construction, and are not the focus of the embodiment, and will not be described in detail here.
The method comprises the following steps that a grouting hole group is formed in a surface soil layer 10 and comprises a plurality of grouting holes 11 which are arranged in a quincunx hole arrangement mode and are vertically arranged respectively, namely the grouting holes 11 are arranged in multiple rows, the grouting holes 11 in two adjacent rows are arranged in a staggered mode to form the quincunx mode, the hole distance between every two adjacent grouting holes 11 in the same row is 1.5m, the projection of a tunnel excavation region 30 on the upper end face of the surface soil layer 10 is located in the arrangement range of the grouting hole group, the distance between the two sides of the grouting hole group and the side face corresponding to the tunnel excavation region 30 is larger than 2.0m, and particularly, the arrangement range of the grouting hole group is 2.0m outside a tunnel branch contour line; the bottom of the grouting holes 11 located right above the tunnel-excavated area 30 are located at a position 0.5m below the tunnel upper-portion contour line 31 of the tunnel-excavated area 30, and the bottom of the other grouting holes 11 are located at the boundary between the surface soil layer 10 and the rock layer 20.
The grouting holes 11 are filled with mixed double grout of cement paste and water glass; specifically, as shown in fig. 1 to 3, a grouting pipe 12 is inserted into each grouting hole 11, the lower end of the grouting pipe 12 is sealed (i.e., plugged with a plug), a grout stop plug 13 is sleeved outside the grouting pipe 12, the grout stop plug 13 is a grout stop film bag in this embodiment, a plurality of grout overflow holes 14 are formed in the side wall of the grouting pipe 12 at a position below the grout stop plug 13, a mixture of cement grout and water glass is filled between the grouting pipe 12 and the grouting hole 11 at a position below the grouting plug 13 and in the grouting pipe 12, and concrete, preferably rapid-setting concrete, is filled between the grouting pipe 12 and the grouting hole 11 at a position above the grouting plug 13.
As shown in fig. 1 to 7, a plurality of large-diameter steel pipes 15 are inserted into the surrounding rock arch, and the specific inclination angle and the arrangement position of the large-diameter steel pipes 15 need to be determined according to actual geological conditions. It should be noted that the large caliber corresponds to the small caliber mentioned below, and is only for distinguishing the relative caliber size between the two steel pipes, that is, the caliber of the steel pipe 15 is larger than the caliber of the steel pipe 16 mentioned below, and does not refer to the actual caliber of the steel pipe, and the specific caliber can be determined according to actual needs, in this embodiment, the caliber of the large caliber steel pipe 15 is phi 108mm, and the inclination angle of the large caliber steel pipe 15 with respect to the horizontal plane is 1-2 °. In addition, a first hole is formed in the side wall of the large-diameter steel pipe 15, and cement paste is filled in the large-diameter steel pipe.
The tunnel face is provided with a grout stopping disc, the grout stopping disc is provided with small-caliber steel pipes 16 which are inserted into the tunnel face simultaneously in an inserting mode, the small-caliber steel pipes are supported on the steel arch frames simultaneously, similarly, the side walls of the small-caliber steel pipes 16 are provided with second holes, and the small-caliber steel pipes 16 are filled with cement grout.
Preferably, on the cross section of the tunnel excavation region 30, two rays (which are virtual lines and do not exist actually) are made to be symmetrical about the center line of the contour of the tunnel excavation region 30 with the intersection point between the center line of the contour of the tunnel excavation region 30 and the tunnel lower contour line of the tunnel excavation region 30 as the origin, when the included angle between the two rays is 60 °, the region corresponding to the region formed between the surrounding rock arch and the two rays is the layout range of the large-diameter steel pipe 15, and when the included angle between the two rays is 120 °, the region corresponding to the region formed between the grout stopping disk and the two rays is the layout range of the small-diameter steel pipe 16.
The embodiment also provides a composite reinforcing method for the shallow tunnel capable of realizing the composite reinforcing structure, the construction object of the method is the urban small-clear-distance shallow tunnel, the vault is the distribution of fourth-system cohesive soil and gravel soil, the surrounding rock of the tunnel is classified into V grade, the single-hole span of the tunnel is large, the soil covering along the tunnel is shallow, the soil layer has poor self-stability, and the excavation is easy to collapse; the section of the tunnel is positioned in a soft loess layer and a gravel layer, and the tunnel has high water permeability; underground pipelines (such as drainage pipes, cable pipes and the like) above the tunnel are more; the ground traffic has large frequency dynamic load and large load, and is easy to collapse due to repeated disturbance excavation of the soil body.
Referring to fig. 1 to 7, the method provided in this embodiment includes the following steps performed in sequence:
and S1, performing earth surface grouting, vertically arranging a plurality of grouting holes 11 on the earth surface above the shallow tunnel to be excavated in a quincunx hole arrangement mode according to the sequence of alternately arranging and jumping holes to form a grouting hole group, wherein in the grouting hole group, the hole bottoms of the grouting holes 11 positioned right above the shallow tunnel are positioned below the tunnel upper contour line 31 of the shallow tunnel, the hole bottoms of other grouting holes 11 are positioned at earth-rock boundary lines, wherein the earth-rock boundary lines are the boundary lines between the surface soil layer 10 and the rock layer 20, and the positions of the earth-rock boundary lines need to be pre-explored before earth surface grouting. Specifically, firstly, a Luoyang shovel is adopted to dig holes, the digging depth is deeper than 1m below the bottom of the underground pipeline so as to avoid damaging the underground pipeline, then a down-the-hole drill is adopted to drill holes, the clear distance between the drilling position and the underground pipeline is not less than 1m, the drilling depth is 0.5m below the contour line of the upper part of the tunnel from the ground, and the drilling range is 2.0m outside the contour line of the primary support and is from the upper surface of the ground to the boundary line of the earth rock. The diameter of the grouting holes 11 is 90mm, and the distance between two adjacent grouting holes 11 in the same row of grouting holes is 400 mm.
Then injecting mixed double grout of cement paste and water glass into each grouting hole 11, and filling the mouth part of each grouting hole 11 with concrete for tamping; preferably, before injecting the cement slurry and the water glass mixed double slurry into each grouting hole 11, a grouting pipe 12 is inserted into each grouting hole 11, the grouting pipe 12 is a steel pipe, the outer diameter of the grouting pipe is phi 42mm, the outer diameter of the grouting pipe is smaller than the inner diameter of the grouting hole 11, the lower end of the grouting pipe 12 is sealed, a grout stop plug 13 (in the embodiment, a grout stop film bag is used as the grout stop plug 13) is sleeved outside the grouting pipe 12, the grout stop plug 13 is fixed on the corresponding grouting pipe 12, the axial length of the grout stop plug 13 is not less than 1m, and the distance between the bottom end surface of the grout stop plug 13 and the bottom of an underground pipeline is not less than 2 m. The side wall of the grouting pipe 12 is provided with a plurality of grout overflow holes 14 at the position below the grout stop plug 13, when grout and water glass mixed double grout are injected into each grouting hole 11, the grouting is performed on the grouting pipe 11 in a mode of low-pressure slow seepage and high-pressure grouting (the low pressure and the high pressure refer to the relative pressure of the grout and the water glass, but not specific pressure), so that the grout and the water glass mixed double grout can permeate into the surface soil layer 10 through the grout overflow holes 14 to reinforce the surface soil layer 10, meanwhile, the concrete at the opening part of the grouting hole 11 has enough setting time, the grout and the water glass mixed double grout are prevented from being sprayed out from the grouting holes 11 under the action of high pressure, and the specific grouting pressure can be selected according to actual needs and is usually selected within the range of 0.3-0.8 MpA. When injecting the mixed double grout of cement paste and water glass into each grouting hole 11, alternate grouting is adopted, namely the grouting holes 11 which are continuously grouted for two times are not adjacent.
The reliability of the reinforcing effect is ensured through the steps; the grouting range and pressure are controllable, and the principle of low-pressure slow seepage and high-pressure grouting is adopted for grouting to achieve good pre-reinforcing and seepage-proofing effects on the soft surrounding rock and gravel stratum of the arch crown.
And S2, supporting the pipe shed, inserting a large-diameter steel pipe 15 (namely a pipe shed steel pipe) into the surrounding rock arch part of the shallow tunnel from high to low, forming a first hole on the side wall of the large-diameter steel pipe 15, pressing cement paste into the large-diameter steel pipe 15, and enabling part of the cement paste to flow out of the first hole and be fixedly connected to the surrounding rock arch part. Specifically, the pipe shed steel pipes are jacked by adopting a principle that phi 108mm pipe shed steel pipes replace drill pipes, a pipe shed drilling machine is selected to drill large-diameter steel pipes 15 serving as the pipe shed steel pipes into the surrounding rock arch part according to a certain inclination angle from a high hole position to a low hole position, the drilling external insertion angle is preferably 1-2 degrees, the arrangement range of the large-diameter steel pipes 15 is determined according to specific geological conditions, and the large-diameter steel pipes can be distributed in the range of 60 degrees in the surrounding rock arch part in the embodiment. The large-diameter steel pipe 15 can be formed by splicing a plurality of pipe sections, and the drilled hole should be drilled with a perforated pipe section (i.e. a pipe section with a first hole) first, and then the drilled hole should be drilled with a non-perforated pipe section after grouting. The pipe head is welded into a cone shape to facilitate the hole entering, the steel pipe joint is connected by screw threads, and one end of the large-caliber steel pipe 15 which firstly penetrates into the arch part of the surrounding rock needs to be sealed. After the large-diameter steel pipe 15 is inserted, the opening peripheral wall of a hole formed at the position of the opening end of the steel pipe corresponding to the surrounding rock arch part is sealed by cement. During grouting, cement slurry is pressed into the large-diameter steel pipe by high pressure, and the slurry is injected into the gap of the hole wall through the first intraocular pressure to consolidate the adjacent rock stratum. The large-diameter steel pipes 15 are sequentially numbered according to the arrangement sequence of quincunx holes, wherein odd-numbered holes are single-numbered holes, even-numbered holes are double-numbered holes, the single-numbered holes are firstly poured for grouting, and the double-numbered holes are poured after solidification for 1 to 2 days.
S3, advancing the small duct support, wherein advancing means that the small duct support step is performed before the preliminary support step, and wherein small in the small duct means that the outer diameter of the duct used in this step is smaller than the outer diameter of the pipe shed steel pipe. The concrete step is that concrete is sprayed to seal the tunnel face of the shallow tunnel, a grout stopping disc with the thickness of 5-10 cm is formed on the tunnel face, then a drilling machine is adopted to form a plurality of supporting holes on the grout disc in a quincunx hole distribution mode from high to low, and the hole distribution range is distributed in a fan shape of 120 degrees by taking the center of the section as an axis. Then, a small-caliber steel pipe 16 (namely a conduit) penetrates into the supporting hole, the small-caliber steel pipe 16 is simultaneously supported on the steel arch frame, a plurality of second holes are formed in the side wall of the small-caliber steel pipe 16, and then cement paste is pressed into the small-caliber steel pipe 16, so that part of the cement paste flows out of the second holes and is solidified. Specifically, the small-caliber steel pipe 16 is a hot-rolled seamless steel perforated pipe with the outer diameter of phi 50mm, the wall thickness is 3.5mm, the aperture of the second perforation is 6mm, the distance between the second perforation and the small-caliber steel pipe is 15cm, the small-caliber steel pipe is arranged in a quincunx shape, the front section of the small-caliber steel pipe 16 is made into a garlic clove-shaped cone, and the second perforation is not drilled in a certain range of the tail end (the specific range can be determined according to actual urgent needs) so as to serve as a pulp stopping. The small-caliber steel pipes 16 are arranged in a double-layer mode, the longitudinal distance is 240cm, the circumferential distance is 35cm, the inclination angles are 10 degrees and 30 degrees respectively, and the small-caliber steel pipes are distributed in the range of 120 degrees of the surrounding rock arch portion. During construction, the small-caliber steel pipe 16 is directly driven into the steel arch from the upper part and/or the middle part of the steel arch by a rock drill, is exposed by 20cm and supported on the steel arch behind an excavation surface, and is firmly welded with a steel frame to form a pre-supporting system; and then, adopting a grouting pump to press and inject cement paste, wherein the protective hole is tightly blocked after grouting.
And S4, primary support, excavating by adopting a two-stage step method, immediately carrying out spray anchor support on the surrounding rock of the shallow tunnel after the tunnel is excavated, wherein anchor rods adopted by the spray anchor support are hollow grouting anchor rods and mortar anchor rods. And primarily spraying the surrounding rock by adopting wet-type sprayed concrete, and paving and hanging the reinforcing mesh after the thickness of the primarily sprayed concrete reaches 3-5cm so as to enable the reinforcing mesh and the sprayed concrete to form a whole. Specifically, after a tunnel is excavated, spray anchor supporting is immediately carried out on surrounding rocks, the anchor rods are hollow grouting anchor rods with the diameter of 25mm and mortar anchor rods with the diameter of 22mm, after grouting is finished, backing plates and fastening nuts are installed after the strength of cement paste meets the requirement, wet-type sprayed concrete construction is adopted, reinforcing steel bar nets are laid and hung after primary sprayed concrete reaches 3-5cm, the reinforcing steel bar nets and the sprayed concrete are integrated, the reinforcing steel bar nets are bound and fixed on the anchor rods in the early construction, then reinforcing steel bar pieces are welded into nets, and the lap joint length of the net pieces is 1-2 grids. After the excavation of the tunnel bottom is finished, the primary support of the bottom is timely followed up, steel frames are completely enclosed in a hole and are connected into a whole by bolts, then the arch springing and the foot-locking anchor pipe 50 are welded into a whole to form a reinforced support, or the arch springing is reinforced and supported by adopting a longitudinal joist and foot-locking anchor pipe 50 with the diameter of phi 108mm through grouting; the lock pin anchor pipe 50 is grouted through the rock and soil interface of the upper and lower steps. When a large gap exists between the steel frame and the primary sprayed concrete in the installation process, the steel frame and the primary sprayed concrete are wedged tightly by concrete precast blocks at intervals of 2m, and the back of the steel frame is densely filled with the sprayed concrete. In order to enhance the overall stability of the steel frame, the steel frame and the anchor rod are welded together, the steel frame is longitudinally connected by steel pipes, and the circumferential distance is 1 m.
Preferably, after the above steps are completed, the following steps can be further performed:
s5, grouting and reinforcing the middle rock pillar: and before excavating the backward hole, drilling holes layer by layer in the forward hole from top to bottom by using a down-the-hole drill, wherein the drilling holes are uniformly distributed in two rows of quincunx shapes along the middle rock pillar, the drilling angle is 10-15 degrees, and the distance is 40 cm. A grout stopping film bag is used as a grout stopping plug, a grouting pipe is a seamless steel flower pipe with the diameter of 42mm and the thickness of 5mm, holes are drilled at intervals of 20cm, the diameter of each hole is 6mm, and the top end of each hole is closed. Grouting is carried out in a mode of mixed double-liquid grouting at the separation hole, and gaps between the steel pipes above the grout stopping film bags and the drilled holes are filled with double-liquid grouting. And the risk during the construction of the small clear distance tunnel is greatly reduced while the bearing capacity of the medium rock pillar is fully exerted by grouting the medium rock wall.
According to the composite reinforcing method provided by the embodiment, the surrounding rock settlement amount in the surrounding rock excavation process is strictly controlled; the initial self-supporting capacity of the tunnel surrounding rock is fully exerted; on the basis, the influence of the vehicle load of the main road on the tunnel structure is reduced, the integrity of the surface pipelines before and after tunnel excavation is ensured, and the surface pipelines before and after tunnel excavation are not damaged. The primary support of the tunnel surrounding rock is carried out in time by adopting the spray anchor and the steel arch frame, the integrity of the support structure is enhanced by welding and spraying concrete between the spray anchor and the steel arch frame, and the primary self-supporting capability of the tunnel surrounding rock is fully exerted; in order to fully play the supporting role of the steel arch on the surrounding rock, the arch feet of the steel arch are reinforced by grouting through the foot locking anchor pipes 50, and the foot locking anchor pipes 50 penetrate through rock strata and soil layers of the upper step and the lower step, so that the integrity and the stability of the upper stratum and the lower stratum are enhanced, and the deformation of the surrounding rock is effectively reduced. The whole composite grouting reinforcement method obtains excellent social and economic benefits.
The present invention is described in detail with reference to the attached drawings, but the embodiments of the present invention are not limited to the above embodiments, and those skilled in the art can make various modifications to the present invention based on the prior art, which fall within the scope of the present invention.
Claims (9)
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| CN114278310A (en) * | 2021-12-06 | 2022-04-05 | 中交一公局集团有限公司 | Construction method for micro steel pipe pile lattice beam at shallow buried section of tunnel |
| CN114718602A (en) * | 2022-03-31 | 2022-07-08 | 广西北投交通养护科技集团有限公司 | Reinforcement treatment method for tunnel to pass through loose gravel waste soil pile |
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