Railway reinforcement structure and method for shallow-buried three-hole large-section tunnel underpassing

Abstract

The present application relates to the technical field of long and large tunnel construction, in particular to a railway reinforcing structure and method for shallow-buried excavation of a three-hole large-section tunnel, comprising a three-hole tunnel and a railway embankment arranged above the three-hole tunnel, first grouting pipes arranged on the soil on both sides of the railway embankment, pipe-shed support beams arranged below both sides of the railway embankment, a plurality of root piles arranged at the bottom of the pipe-shed support beams, and a plurality of second grouting pipes arranged in the middle of the pipe-shed support beams. The present application fills and blocks fissures by grouting into the root piles and the second grouting pipes, and further grouts and reinforces the broken surrounding rock at the bottom of the inverted arch after the initial support construction of the inverted arch of the three-hole tunnel is completed, thereby preventing further settlement.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of long and large tunnel construction, in particular to a railway reinforcement structure and method for shallow-buried excavation of a three-hole large-section tunnel. BACKGROUND

[0002] The number of newly-built highway tunnels is increasing, and due to the restriction of terrain conditions, the newly-built tunnel often needs to pass under the existing railway engineering. The tunnel excavation not only has adverse effects on the safety production of the newly-built tunnel construction, but also endangers the driving safety of the existing railway, especially the large-section tunnel portal passing under the existing railway in high-altitude cold regions, which has high construction difficulty, high risk and high technical requirements. If the reinforcement measures and excavation methods are improper during the process, the surrounding rock and the ground surface will produce large plastic deformation, and even cracks and collapse, which will affect the tunnel construction and the safety of the railway.

[0003] Combined with a 22.13km long highway tunnel, a separated design is adopted, and the total length of the tunnel is 22.130km, which is a control engineering along the whole line. The tunnel adopts a “3-hole + 4-vertical well” design scheme. The tunnel exit end is located at a high-cold and high-altitude position, the upper part of the lithology composition is ice-water accumulated gravel soil, which is medium dense, and the thickness is small, the underlying bedrock is granite, the surrounding rock is V-level, the stability is poor, and it is in the freezing-thawing zone, the maximum freezing depth in the tunnel site area is 2.0-5.0m. The three-hole tunnel exit end YK97+727-783.1 passes under the railway (railway pile number K243+423-544), the distance from the existing railway steel rail top to the top of the second lining of the left hole, the right hole and the middle pilot hole of the tunnel is 10.25m, 9.18m and 11.12m respectively, and the prevention and treatment of the railway embankment settlement caused by the excavation of the “double main hole + middle pilot hole” three-hole large-section tunnel becomes a major technical problem. SUMMARY

[0004] The present application aims to provide a railway reinforcement structure and method for shallow-buried excavation of a three-hole large-section tunnel, which solves the above problems.

[0005] The present application is implemented by the following technical scheme:

[0006] The present application comprises a three-hole tunnel and a railway embankment arranged above the three-hole tunnel, a first grouting guide pipe is arranged on the soil on both sides of the railway embankment, a pipe shed support beam is arranged below both sides of the railway embankment respectively, a plurality of root piles are arranged at the bottom of both ends of the pipe shed support beam respectively, and a plurality of second grouting guide pipes are arranged in the middle of the pipe shed support beam. The present application fills the fissures and blocks the fissure water by grouting into the root piles and the second grouting guide pipes, and further grouting and reinforcing the broken surrounding rock at the bottom of the inverted arch after the initial support construction of the inverted arch is completed, so as to prevent further settlement.

[0007] In view of the technical problems existing in the above background, the combination of "two side slopes batch grouting + root pile + pipe shed support beam + inverted arch bottom grouting" is adopted for the 22.13 km long tunnel under the existing railway, forming an effective reinforcement structure, and solving the technical problem of controlling the settlement of the "double main hole + middle pilot hole" three-hole large cross-section tunnel under the existing railway embankment.

[0008] Further, the plurality of first grouting pipes are arranged in a plum blossom shape with a size of 100 cm*100 cm.

[0009] Further, a plurality of layers of steel mesh are laid on the side slopes of the railway embankment, and a B cm thick sprayed concrete is laid to close the slope surface, wherein B≥10 cm.

[0010] Further, the plurality of root piles are arranged in a plum blossom shape, the depth of the bottom of the root pile embedded in the bottom of the three-hole tunnel inverted arch is A, and A≥500 cm is satisfied, and the depth of the top of the root pile embedded in the bottom of the pipe shed support beam is C, and C≥30 cm is satisfied.

[0011] Further, the plurality of second grouting pipes are arranged in a plum blossom shape, and the depth of the top of the second grouting pipe embedded in the pipe shed support beam is G, and G≥10 cm is satisfied.

[0012] Further, a plurality of guide pipes with an outer diameter of D are arranged at intervals on the pipe shed support beam, and the end of the guide pipe of one pipe shed support beam penetrates into a large pipe shed with an outer diameter of D1 and communicates with the guide pipe of another pipe shed support beam, and D>D1 is satisfied.

[0013] Further, the root pile and the large pipe shed are both seamless steel pipes, and a plurality of overflow holes are arranged around the root pile and the large pipe shed in a plum blossom shape.

[0014] Further, the first grouting pipe and the second grouting pipe are both seamless steel pipes, the end of the first grouting pipe and the second grouting pipe is conical, and a plurality of overflow holes are arranged around the first grouting pipe and the second grouting pipe in a plum blossom shape.

[0015] Further, the railway reinforcement method for the shallow-buried three-hole large cross-section tunnel under the railway:

[0016] S1: Use the rock-soil numerical software to perform finite element simulation analysis on the ground surface and track deformation when the three-hole tunnel is constructed to the railway embankment and passes through the railway embankment, and obtain key construction parameters to guide the construction;

[0017] S2: After drilling a hole using a YT-28 pneumatic drill, clean the hole with high-pressure air, insert the first grouting guide pipe into the hole, and seal the tail end of the first grouting guide pipe. Initial shotcrete is applied to seal the slope within the embankment reinforcement area. Several layers of steel mesh are laid on the initial shotcrete surface on both sides of the railway embankment. Several layers of steel mesh are then sealed with shotcrete on the steel mesh. The first grouting guide pipe is connected to the grouting pipeline for grouting through the hole.

[0018] S3: Grouting is carried out sequentially on the tree root piles, the second grouting pipe between the tree root piles, and the pipe roof support beam;

[0019] S4: Excavate and clean the bottom of the invert arch, spray initial concrete, install the steel arch frame, drill holes with YT-28 pneumatic drill, clean the holes with high-pressure air, insert the first grouting pipe, spray concrete again to the design thickness, connect the grouting pipeline to the first grouting pipe for grouting construction.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] 1. This invention employs a combination of "slope grouting in batches + root piles + pipe roof support beams + grouting at the bottom of the inverted arch" to reinforce the undisturbed soil and reduce its permeability coefficient, thereby achieving the purpose of reinforcing the undisturbed soil and blocking water. At the same time, "slope grouting in batches, root piles, pipe roof support beams, and grouting at the bottom of the inverted arch" can play a role in bearing and stopping water, and are safe and reliable.

[0022] 2. The combined technical measures of "slope grouting in batches, root pile grouting, pipe roof support beams, and grouting at the bottom of the invert arch" reduced the impact of cross-operations between the underpass tunnel construction and the existing railway, improved construction efficiency, shortened construction time, and reduced construction costs. Simultaneously, it successfully solved the problem of safely, quickly, and with high quality constructing a shallow-buried, three-tunnel, large-section tunnel under an existing railway without relocation. This eliminated the need to negotiate railway relocation with railway authorities and to halt construction while waiting for the railway relocation, saving significant railway relocation costs and minimizing the impact of railway relocation on the tunnel's construction progress. This ensured the continuity of the three-tunnel, large-section tunnel construction and accelerated the tunnel's progress. It not only saved construction costs for the construction unit but also reduced the project investment costs for the construction company and the associated costs for railway relocation and rerouting, indirectly saving substantial expenses and lowering the overall project cost.

[0023] 3. By grouting and reinforcing the railway embankment, the physical and mechanical properties of the embankment soil were improved, the self-stability of the railway embankment soil was enhanced, the permeability coefficient of the soil was reduced, the railway embankment was kept stable when the tunnel passed under it, and the surface settlement after the tunnel excavation was controllable, which effectively ensured the safety and quality of the tunnel under the railway section during rapid construction.

[0024] 4. The combined technical measures of "slope grouting in batches, root piles, pipe roof support beams, and grouting at the bottom of the invert arch" are highly implementable and innovative, ensuring construction quality, accelerating construction progress, significantly shortening the construction period and reducing safety risks of the underpass railway tunnel, and solving the technical problems of difficult excavation of a three-section large-section tunnel under a railway and the difficulty of controlling roadbed settlement. It greatly reduces environmental pollution, generates significant environmental benefits, saves on manpower, machinery, and materials, and reduces material consumption. Attached Figure Description

[0025] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0026] Figure 1 This is a schematic diagram of the longitudinal section of the three tunnels passing under the railway in an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the cross-section of the support beam for the three tunnels passing under the railway in an embodiment of the present invention.

[0028] The attached diagram shows the markings and corresponding component names:

[0029] 1-Steel rail; 2-Railway embankment; 3-Shotcrete; 4-First grouting pipe; 5-Pipe roof support beam; 6-Large pipe roof; 7-Tree root pile; 10-Second grouting pipe. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this invention are only for explaining this invention and are not intended to limit this invention.

[0031] Example:

[0032] This invention includes a three-tunnel structure and a railway embankment 2 located above the tunnel. First grouting pipes 4 are installed on the soil on both sides of the railway embankment 2. Pipe roof support beams 5 are installed below both sides of the railway embankment 2. Several root piles 7 are installed at both ends of the bottom of each pipe roof support beam 5, and several second grouting pipes 10 are installed in the middle of each pipe roof support beam 5. Grouting the first grouting pipes 4 consolidates the loose soil of the railway embankment 2. Simultaneously, the pipe roof support beams 5 are positioned on both sides of the railway embankment 2 at a distance Hm below the top surface elevation of the rails 1, preferably H is 5m.

[0033] Through the grouting reinforcement of the railway embankment 2, the physical and mechanical properties of the embankment soil are improved, the self-stability of the embankment soil is improved, and the permeability coefficient of the soil is reduced, so that the railway embankment 2 is stable when the tunnel passes underneath. After the tunnel is excavated, the ground settlement is controllable, effectively ensuring the safety and quality of the tunnel under the railway section during rapid construction.

[0034] It should be noted that the first grouting pipes 4 are arranged in a plum blossom shape with a size of 100cm x 100cm. When each small pipe is grouted, the grout is diffused into the stratum from the overflow hole to form a separate water-stopping curtain. The plum blossom arrangement of the small pipes allows the grouting curtains of the small pipes to intersect with each other, forming a better sealing curtain, solving the shortcomings of conventional arrangements that cannot form a closed grouting curtain, and achieving a significant sealing effect.

[0035] It should be noted that before grouting the first grouting pipes 4, concrete needs to be initially sprayed on the slope surfaces of the railway embankment 2 on both sides, several layers of steel mesh need to be laid, and Bcm thick sprayed concrete needs to be re-sprayed to seal the several layers of steel mesh, where B≥10cm. This plays the role of a grout-stopping pad. The steel mesh needs to be completely wrapped by the concrete, so after the initial spraying of concrete, several layers of steel mesh are laid, and then the concrete is re-sprayed to ensure that the sprayed concrete is wrapped, and the steel mesh plays its role. At the same time, after the initial spraying of concrete, the steel mesh is hung, which is beneficial to construction safety. At the same time, a thick grout-stopping pad is formed to prevent the grout from breaking through the stratum and shooting out of the slope surface when the small pipes are grouted at high pressure, thereby losing grouting pressure and reducing grouting quality.

[0036] It should be noted that the outer wall of the innermost pile of the several root piles 7 at both ends of the pipe roof support beam 5 is at least 3m away from the maximum excavation line of any one of the three-hole tunnels. After grouting the several root piles on both sides, a good "columnar" reinforced body is formed around the soil. If the distance is too close, blasting excavation or non-blasting excavation will disturb and damage the "columnar" reinforced body, reduce the bearing capacity, and make the support beam at the top of the root pile lose stability. The several root piles 7 are arranged in a plum blossom shape and vertically punched into the rock. The depth of the bottom of the root pile 7 embedded in the invert of the three-hole tunnel is A, and A≥500cm, so that the bottom of the root pile is better embedded in the stable bedrock, plays the effect of end-bearing pile, is beneficial to the stability of the top pipe roof support beam, and the depth of the top of the root pile 7 embedded in the bottom of the pipe roof support beam 5 is C, and C≥30cm, which plays the effect of "pile-connected column" of the bridge and avoids lateral sliding of the pipe roof support beam on the top of the root pile.

[0037] It should be noted that the second grouting pipes 10 are arranged in a plum blossom shape, and the depth of the top of the second grouting pipes 10 embedded in the pipe roof support beam 5 is G, and G≥10cm, which plays the effect of "pile-connected column" of the bridge and avoids lateral sliding of the pipe roof support beam on the top of the root pile.

[0038] It should be noted that the top of the several tree root piles 7, the second grouting pipe 10 is provided with a pipe shed support beam 5 with geometric size Lx Bx H (lengthx widthx height), and any 1 hole top has at least 2 pipe shed support beams 5, the pipe shed support beam is a reinforced concrete structure, and the pipe shed support beam is equivalent to the cap beam at the top of the bridge pier column, which better supports the large pipe shed and the surrounding soil after grouting to make it play the effect of "simply supported beam". The length L of the pipe shed support beam is the maximum excavation hole diameter + 600 cm, the width is 200 cm, and the height is 150 cm.

[0039] It should be noted that the top of the pipe shed support beam 5 is provided with several guide pipes with an outer diameter D at intervals of L cm, wherein the end of the guide pipe of one pipe shed support beam 5 penetrates into the large pipe shed 6 with an outer diameter D1 and is communicated with the guide pipe of another pipe shed support beam 5, and D>D1. The guide pipe with an outer diameter D is pre-buried in the support beam before pouring concrete, and plays a positioning and guiding role during the implementation of the pipe shed with an outer diameter D1. The interval L is 30 cm, the outer diameter D of the guide pipe is 194 mm, and the outer diameter D1 of the large pipe shed is 146 mm.

[0040] It should be noted that the tree root pile 7 and the large pipe shed 6 are both seamless steel pipes, and several overflow holes are arranged around the tree root pile 7 and the large pipe shed 6 in a plum blossom shape. The purpose of setting the overflow hole is that the grout is filled into the large pipe shed or the small guide pipe under high pressure, and under the strong grouting pressure, the soil around the pipe wall is injected through the overflow hole, so as to achieve the effect of consolidating and consolidating the loose soil.

[0041] It should be noted that the first grouting pipe 4 and the second grouting pipe 10 are both seamless steel pipes, the end of the first grouting pipe 4 and the second grouting pipe 10 is conical, and several overflow holes are arranged around the first grouting pipe 4 and the second grouting pipe 10 in a plum blossom shape.

[0042] It should be noted that the several tree root piles 7, the large pipe shed 6, the first grouting pipe 4 and the second grouting pipe 10 are all injected with cement grout and cement water glass grout to improve the railway embankment 2 and the broken surrounding rock to form a rod-shaped reinforced structure to restrict the relative displacement and settlement of the railway embankment 2, improve the integrity of the embankment, and enhance the shear failure resistance of the overburden soil. The combined reinforcement structure of "slope batch grouting, tree root pile 7, pipe shed support beam 5, and inverted arch bottom grouting" forms a good "simply supported beam" support structure, plays the effect of "simply supported beam", and supports the railway embankment 2 to prevent it from sinking.

[0043] It should be noted that the railway reinforcement method for the shallow-buried and excavated three-hole large-section tunnel underpass is:

[0044] S1: using geotechnical numerical software to simulate and analyze the ground surface and track deformation when the three-hole tunnel construction passes through the railway embankment 2 and is below the railway embankment 2, and to obtain key construction parameters to guide the construction;

[0045] S2: After the YT-28 air drill is used to form holes in the two side slopes of the railway embankment 2 in batches, high-pressure air is used to clean the holes, the first grouting pipe 4 is inserted into the hole, and the tail end of the first grouting pipe 4 is blocked, the initial spraying of concrete is used to close the slope surface in the embankment reinforcement area,

[0046] A number of layers of steel mesh are laid on the initial spraying of concrete slope surface on both sides of the railway embankment 2, and a number of layers of steel mesh are closed by re-spraying concrete 3, the first grouting pipe 4 is connected with the grouting pipe to carry out hole separation grouting;

[0047] S3: Grouting construction is sequentially carried out on the tree root pile 7, between the tree root piles 7, the second grouting pipe 10, and the pipe shed support beam 5;

[0048] S4: Inverted arch excavation and bottom cleaning are carried out, initial spraying of concrete is carried out, steel arch installation is carried out, YT-28 air drill drilling is carried out, high-pressure air hole cleaning is carried out, the first grouting pipe 4 is inserted, re-spraying of concrete is carried out to the designed thickness, and the first grouting pipe 4 is connected with the grouting pipe for grouting construction.

[0049] The technical measures of "batch grouting of side slopes, grouting of tree root piles 7, grouting of pipe shed support beams 5, and grouting of inverted arch bottoms" are combined with each other, which reduces the influence of the underpass tunnel construction on the existing railway crossing operation, improves the construction efficiency, shortens the construction time, and reduces the construction cost. At the same time, the successful solution of the shallow-buried three-hole large-section tunnel underpassing the existing railway without relocation enables safe, fast, and quality and quantity guaranteed normal construction, i.e. without the need to negotiate with the railway-related units for railway relocation, and without the need to suspend construction during the construction process to wait for the relocation time of the underpass railway, which saves a large amount of railway relocation cost, reduces the influence of railway relocation on the construction progress of the three-hole tunnel, ensures the continuity of the construction of the three-hole large-section tunnel, and speeds up the construction progress of the tunnel. Not only does it save the construction cost of the construction unit, but also saves the engineering investment cost of the construction unit, and saves a series of fees for relocation and line change of the railway-related units, indirectly saves huge expenditures, and reduces the engineering cost.

[0050] The above specific embodiments further illustrate the purpose, technical solutions, and beneficial effects of the present application, and it should be understood that the above description is only a specific embodiment of the present application and is not used to limit the protection scope of the present application, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for reinforcing a railway underpass by a shallow-buried three-hole large-section tunnel, characterized in that, S1: using a geotechnical numerical software to perform finite element simulation analysis on the surface and track deformation when the three-hole tunnel construction passes under and through the railway embankment (2), and obtaining key construction parameters to guide the construction; S2: drilling holes in the slopes on both sides of the railway embankment (2), cleaning the holes with high-pressure air, inserting the first grouting guide pipe (4) into the holes, plugging the tail end of the first grouting guide pipe (4), spraying concrete to close the slope surface in the embankment reinforcement area, laying a plurality of layers of steel mesh on the sprayed concrete surface on both sides of the railway embankment (2), and spraying concrete (3) to close the plurality of layers of steel mesh, and connecting the first grouting guide pipe (4) with the grouting pipeline for hole-separation grouting; S3: sequentially grouting the root pile (7), the second grouting guide pipe (10) between the root piles (7), and the pipe shed support beam (5); S4: excavating the inverted arch and clearing the bottom, installing the primary sprayed concrete and the profiled steel arch, drilling holes and then cleaning the holes with high-pressure air, inserting the first grouting guide pipe (4), spraying concrete to the designed thickness, connecting the grouting pipeline to the first grouting guide pipe (4) for hole-separation grouting construction; The above method is implemented by the following structure, The method comprises a three-hole tunnel and a railway embankment (2) arranged above the three-hole tunnel, a first grouting guide pipe (4) arranged on the soil on both sides of the railway embankment (2), a pipe shed support beam (5) arranged below each side of the railway embankment (2), a plurality of root piles (7) arranged at the bottom of both ends of the pipe shed support beam (5), a plurality of second grouting guide pipes (10) arranged in the middle of the pipe shed support beam (5), a plurality of first grouting guide pipes (4) arranged in a plum blossom shape with a size of 100 cm x 100 cm, a plurality of layers of steel mesh laid on the slope surface on both sides of the railway embankment (2), and B cm thick sprayed concrete (3) laid to close the slope surface, wherein B≥10 cm.

2. The railway reinforcement method for the shallow-buried three-hole large-section tunnel underpass according to claim 1, characterized in that, The plurality of root piles (7) are arranged in a plum blossom shape, the depth of the bottom of the root pile (7) embedded in the inverted arch bottom of the three-hole tunnel is A, and A≥500 cm is satisfied, and the depth of the top of the root pile (7) embedded in the bottom of the pipe shed support beam (5) is C, and C≥30 cm is satisfied.

3. The railway reinforcement method for the shallow-buried three-hole large-section tunnel underpass according to claim 1, characterized in that, The plurality of second grouting guide pipes (10) are arranged in a plum blossom shape, and the depth of the top of the second grouting guide pipe (10) embedded in the pipe shed support beam (5) is G, and G≥10 cm is satisfied.

4. The railway reinforcement method for the shallow-buried three-hole large-section tunnel underpass according to claim 1, characterized in that, A plurality of guide pipes with an outer diameter of D are arranged at intervals on the pipe shed support beam (5), one end of the guide pipe of one pipe shed support beam (5) penetrates into a large pipe shed (6) with an outer diameter of D1 and communicates with the guide pipe of another pipe shed support beam (5), and D>D1 is satisfied, and the length of the guide pipe is equal to the width of the support beam.

5. The railway reinforcement method for the shallow-buried three-hole large-section tunnel underpass according to claim 1, characterized in that, The root pile (7) and the large pipe shed (6) are both seamless steel pipes, and a plurality of overflow holes are arranged around the root pile (7) and the large pipe shed (6) in a plum blossom shape.

6. The railway reinforcement method for the shallow-buried three-hole large-section tunnel underpass according to claim 1, characterized in that, The first grouting pipe (4) and the second grouting pipe (10) are seamless steel pipes, the end of the first grouting pipe (4) and the end of the second grouting pipe (10) are conical, and a plurality of overflow holes are arranged in a plum blossom shape around the first grouting pipe (4) and the second grouting pipe (10).

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