Construction method for shallow-buried large-section tunnel long-distance underpassing expressway

Abstract

The application discloses a construction method for shallow-buried large-section tunnel long-distance underpassing of an expressway, and particularly relates to the following steps: S1, vertical shafts are respectively constructed in a middle strip of the expressway and on both sides of an expressway roadbed; the vertical shaft in the middle strip of the expressway is a first vertical shaft, and the vertical shafts on both sides of the expressway roadbed are respectively a second vertical shaft and a third vertical shaft; S2, the tunnel underpassing the expressway is divided into an open-cut section and a tunneling section, and an advanced pipe shed and an advanced pipe roof are constructed to the tunneling section through the vertical shafts; S3, under the support of the advanced pipe shed and the advanced pipe roof, the tunneling section is constructed, the tunneling section adopts composite lining, and a step-by-step excavation support method is adopted; and S4, after the construction of the tunneling section is completed, the open-cut section is constructed in the first vertical shaft, and the first vertical shaft is backfilled; the method can effectively control the expressway road surface settlement, greatly reduces the tunnel construction risk, and has extremely important significance for guaranteeing the tunnel construction safety and the expressway driving safety.

Description

Technical Field

[0001] The present invention relates to the technical field of construction under expressways, and specifically to a construction method for a long-distance shallow-buried large-section tunnel passing under an expressway. Background Technique

[0002] With the continuous development of China's economy, the national transportation road network has become increasingly complete, and the number of road construction projects has increased day by day. Inevitably, there are situations where new roads pass under existing expressways in the form of tunnels. When passing under an expressway, the ground loss caused by tunnel excavation will lead to different degrees of settlement of the expressway pavement; when the construction method or the auxiliary measures taken are inappropriate, it may also lead to excessive settlement of the expressway pavement, and even hazards such as ground cracking and subsidence, which are likely to cause serious traffic and safety accidents and result in relatively large economic losses.

[0003] The traditional construction method for a tunnel passing under an expressway is to adopt a composite lining and the double-side drift method to penetrate from one side of the tunnel portal to the other side or from both sides of the tunnel portal to the middle under the support conditions of pipe sheds and advanced small pipe piles. This solution can solve the safety problem of tunnel construction to a certain extent, but there are the following problems in the application of projects with large tunnel sections, shallow burial depths, and wide median strips of expressways: 1) Due to the wide median strip of the expressway, the length of the shallow-buried and mined section of the tunnel in the traditional construction method is too long, the construction difficulty of the pipe shed is high, and the construction accuracy is low, making it difficult to exert the effect of advanced support, and serious subsidence is extremely likely to occur during the construction process.

[0004] 2) Due to the shallow burial depth of the tunnel, which is mainly located in the subgrade backfill or soil strata, the surrounding rock has poor lithology and low grade. The traditional tunnel construction method causes great disturbance to the strata. Coupled with the large tunnel section, the risk of excessive settlement or collapse of the pavement caused by the removal of temporary supports is extremely high. Summary of the Invention

[0005] The purpose of the present invention is to provide a construction method for a long-distance shallow-buried large-section tunnel passing under an expressway, which can effectively reduce construction risks, strictly control pavement settlement, minimize the construction period, and not interrupt traffic during the construction process of a long-distance tunnel passing under an expressway.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions: A construction method for a long-distance shallow-buried large-section tunnel passing under an expressway specifically includes the following steps: S1. Construct vertical shafts respectively in the median strip of the expressway and on both sides of the expressway subgrade. The vertical shaft in the median strip of the expressway is the first vertical shaft, and the vertical shafts on both sides of the expressway subgrade are the second vertical shaft and the third vertical shaft respectively; S2. The tunnel under the expressway is divided into an open-cut section and a cut-and-cover section. Advanced pipe roof and advanced pipe curtain are constructed into the cut-and-cover section of the tunnel through vertical shafts. The specific construction steps for step S2 are as follows: S21. Constructing a reinforced concrete arch within a vertical shaft; S22. Under the guidance of the arch, advance pipe jacking is constructed from the first vertical shaft to the second and third vertical shafts; S23. Under the guidance of the arch, the first and second vertical shafts, and the first and third vertical shafts are respectively constructed in opposite directions to advance the pipe roof; S3. Under the support of advanced pipe roof and advanced pipe curtain, the tunnel excavation section is constructed. The tunnel excavation section adopts composite lining and the excavation support method is the sectional step method. S4. After the tunnel excavation section is completed, the open-cut section of the tunnel will be constructed in the first shaft, and then the first shaft will be backfilled.

[0007] Preferably, the specific construction steps of step S1 are as follows: S11. Level the site and drive the first foundation pit cast-in-place pile and the first high-pressure jet grouting pile to form a water-stop curtain. S12. Excavate the soil, then set up the foundation pit capping beam, and set up the first foundation pit support horizontally at the position of the foundation pit capping beam; S13. After the first foundation pit support reaches the design strength, continue to excavate the soil, then set the foundation pit waist beam, and set the second foundation pit support horizontally at the position of the foundation pit waist beam. S14. After the second foundation pit support reaches the design strength, continue the excavation of soil for cyclic support and excavation steps until the bottom of the initial foundation pit is reached.

[0008] Preferably, the advanced pipe curtain in step S22 is a φ720×16mm steel pipe, distributed at 110cm intervals on the arch, constructed using a micro-jacking technique, and filled with fine stone concrete after the jacking is completed.

[0009] Preferably, the advanced pipe shed mentioned in step S23 is a φ180×8mm steel pipe shed, with the arch spacing distributed at 110cm and the side wall spacing distributed at 30cm.

[0010] Preferably, the composite lining in step S3 includes initial support and cast-in-place concrete lining. The initial support includes φ42 grouting system anchor pipes, double-layer φ8 steel mesh of @15cm×15cm, I25a I-beam arch frame and shotcrete. The cast-in-place concrete lining includes 50cm thick grid steel frame concrete lining and 70cm thick reinforced concrete lining. The sectional upper and lower step method divides the tunnel excavation section into the first pilot tunnel, the second pilot tunnel, the third pilot tunnel and the fourth pilot tunnel from left to right. Each of the first pilot tunnel, the second pilot tunnel, the third pilot tunnel and the fourth pilot tunnel is further divided into upper step and lower step.

[0011] Preferably, the specific construction steps of the sectional step method in step S3 are as follows: S31. Excavate the upper steps of the first and fourth pilot tunnels, then construct the initial support and temporary support for the upper steps, and seal the working face. S32. Excavate the lower bench of the first and fourth pilot tunnels, and then construct the initial support and temporary support of the lower bench and seal the working face; S33. Excavate the upper step of the second pilot tunnel, then construct the initial support and temporary support of the upper step, and seal the working face; S34. Excavate the lower bench of the second pilot tunnel, then construct the initial support and temporary support for the lower bench, and seal the working face; S35. Excavate the upper bench of the third pilot tunnel, then construct the initial support and temporary support for the upper bench, and seal the working face; S36. Excavate the lower bench of the third pilot tunnel, then construct the initial support and temporary support for the lower bench, and seal the working face; S37. Repeat steps S31 to S36 until the tunnel excavation section is completed. Then, remove the shotcrete that temporarily supports the cast-in-place concrete lining to expose the I-beams. S38. Erect the grid steel frame without removing the temporary supports, and pour the grid steel frame concrete lining. S39. After the construction of the grid steel frame concrete lining of the tunnel excavation section is completed and reaches the design strength, the temporary supports are removed section by section, waterproof membrane is laid, and the reinforced concrete lining is constructed using a trolley.

[0012] Preferably, in step S3, the soil in front of the tunnel face is reinforced by full-section curtain grouting before the tunnel is excavated. Preferably, in steps S31 and S33, a small guide pipe is driven into the soil ahead before the tunnel is excavated.

[0013] Preferably, the I-beam described in step S37 is exposed for rust removal and rust prevention treatment.

[0014] By adopting the above technical solution, the present invention has the following beneficial effects: The present invention divides the tunnel into cut-and-cover and open-cut sections by setting vertical shafts in the median strip of existing highways, greatly reducing the length of the cut-and-cover section. Simultaneously, it comprehensively applies advanced pipe jacking and pipe roofing to control the deformation of the soil at the tunnel top, uses advanced curtain grouting to reinforce the soil at the tunnel face, employs a stepped excavation method, and implements the first layer of grating steel frame concrete lining without removing temporary supports, followed by the complete removal of temporary supports for the second reinforced concrete lining. This construction method can effectively control highway pavement settlement, greatly reduce tunnel construction risks, and is of paramount importance for ensuring tunnel construction safety and highway traffic safety. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating the construction process of the present invention. Figure 2 This is a plan view of the present invention; Figure 3 This is a schematic elevation view of the present invention; Figure 4 This is a cross-sectional schematic diagram of the present invention; Figure 5 This is a schematic diagram of the excavation cross section of the present invention; Figure 6 This is a schematic diagram of the excavation elevation of the present invention.

[0016] The reference numerals in the figure are as follows: 1. First vertical shaft; 2. Second vertical shaft; 3. Third vertical shaft; 4. Reinforced concrete arch; 5. Advanced pipe jacking; 7. Advanced pipe roof; 8. System anchor pipe; 9. Advanced small guide pipe; 10. I-beam arch frame; 11. Shotcrete; 12. Locking anchor bolt; 13. Grating steel frame concrete lining; 14. Reinforced concrete lining; 31. First pilot tunnel; 32. Second pilot tunnel; 33. Third pilot tunnel; 34. Fourth pilot tunnel. Detailed Implementation

[0017] 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 accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0018] See Figures 1 to 6 A construction method for a shallow-buried, large-section tunnel that passes under a highway over a long distance includes the following steps: S1. Construct vertical shafts in the median strip and on both sides of the roadbed of the expressway. The vertical shaft in the median strip is designated as the first vertical shaft 1, and the vertical shafts on both sides of the roadbed are designated as the second vertical shaft 2 and the third vertical shaft 3, respectively. The specific construction steps for step S1 are as follows: S11. Level the site and drive the first foundation pit cast-in-place pile and the first high-pressure jet grouting pile to form a water-stop curtain. S12. Excavate the soil, then set up the foundation pit capping beam, and set up the first foundation pit support horizontally at the position of the foundation pit capping beam; S13. After the first foundation pit support reaches the design strength, continue to excavate the soil, then set the foundation pit waist beam, and set the second foundation pit support horizontally at the position of the foundation pit waist beam. S14. After the second foundation pit support reaches the design strength, continue the excavation of soil cyclic support and excavation steps until the bottom of the initial foundation pit is reached. S2. The tunnel under the expressway is divided into an open-cut section and a cut-and-cover section. The advanced pipe roof 7 and advanced pipe curtain 5 are constructed into the cut-and-cover section of the tunnel through a vertical shaft. The specific construction steps for step S2 are as follows: S21. Construct a reinforced concrete arch 4 in the vertical shaft; S22. Under the guidance of the arch 4, the advanced pipe curtain 5 is constructed from the first vertical shaft 1 to the second vertical shaft 2 and the third vertical shaft. The advanced pipe curtain 5 mentioned in step S22 is a φ720×16mm steel pipe, which is distributed at 110cm on the arch top and constructed using micro-jacking technology. After the jacking construction is in place, fine stone concrete is poured and filled. S23. Under the guidance of the arch 4, the first shaft 1 and the second shaft 2, and the first shaft 1 and the third shaft 3 respectively construct the advanced pipe roof 7 in opposite directions; The advanced pipe shed 7 mentioned in step S23 is a φ180×8mm steel pipe shed with a horizontal spacing of 110cm at the arch and a spacing of 30cm between the two side walls; S3. Under the support of the advanced pipe roof 7 and the advanced pipe curtain 5, the tunnel excavation section is constructed. The tunnel excavation section adopts composite lining, and the excavation support method is the sectional upper and lower bench method. The composite lining described in step S3 includes initial support and cast-in-place concrete lining. The initial support includes φ42 grouting system anchor pipes 8, double-layer φ8 steel mesh of @15cm×15cm, I25a I-beam arch frame 10, and shotcrete 11. The cast-in-place concrete lining includes 50cm thick grid steel frame concrete lining 13 and 70cm thick reinforced concrete lining 14. The stepped method divides the tunnel excavation section into the first pilot tunnel 31, the second pilot tunnel 32, the third pilot tunnel 33, and the fourth pilot tunnel 34 from left to right. Each of the first pilot tunnel 31, the second pilot tunnel 32, the third pilot tunnel 33, and the fourth pilot tunnel 34 is further divided into upper and lower steps. The specific construction steps of the sectional step method in step S3 are as follows: S31. Excavate the upper steps of the first pilot tunnel 31 and the fourth pilot tunnel 34, and then construct the initial support and temporary support of the upper steps and seal the working face. S32. Excavate the lower steps of the first pilot tunnel 31 and the fourth pilot tunnel 34, and then construct the initial support and temporary support of the lower steps and seal the working face. S33, excavate the upper step of the second pilot tunnel 32, then construct the initial support and temporary support of the upper step, and seal the working face; S34. Excavate the lower bench of the second pilot tunnel 32, and then construct the initial support and temporary support for the lower bench and seal the working face; S35. Excavate the upper step of the third pilot tunnel 33, and then construct the initial support and temporary support of the upper step and seal the working face. S36. Excavate the lower bench of the third pilot tunnel 33, and then construct the initial support and temporary support of the lower bench and seal the working face; S37. Repeat steps S31 to S36 until the tunnel excavation section is completed. Then, remove the shotcrete that temporarily supports the cast-in-place concrete lining to expose the I-beams. S38. Erect the grid steel frame without removing the temporary supports, and pour the grid steel frame concrete lining. S39. After the construction of the grid steel frame concrete lining of the tunnel excavation section is completed and reaches the design strength, the temporary supports are removed section by section, waterproof membrane is laid, and the reinforced concrete lining is constructed using a trolley. In step S3, the soil in front of the tunnel face is reinforced by full-section curtain grouting before the tunnel is excavated. In steps S31 and S33, before the pilot tunnel is excavated, advance small guide pipes 9 are driven into the soil ahead; In step S37, the I-beams are exposed for rust removal and rust prevention treatment. S4. After the tunnel excavation section is completed, the open-cut section of the tunnel will be constructed in the first shaft 1, and then the first shaft 1 will be backfilled.

[0019] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A construction method for a shallow-buried, large-section tunnel that passes under a highway over a long distance, characterized in that... Specifically, the following steps are included: S1. Construct vertical shafts in the median strip of the expressway and on both sides of the expressway subgrade. The vertical shaft in the median strip of the expressway is the first vertical shaft (1), and the vertical shafts on both sides of the expressway subgrade are the second vertical shaft (2) and the third vertical shaft (3), respectively. S2. Divide the tunnel under the expressway into open-cut section and cut-and-cover section, and construct the advanced pipe roof (7) and advanced pipe curtain (5) in the cut-and-cover section of the tunnel through the vertical shaft. The specific construction steps for step S2 are as follows: S21. Construct a reinforced concrete arch in the vertical shaft (4). S22. Under the guidance of the arch (4), the advanced pipe curtain (5) is constructed from the first vertical shaft (1) to the second vertical shaft (2) and the third vertical shaft. S23. Under the guidance of the arch (4), the first shaft (1) and the second shaft (2), the first shaft (1) and the third shaft (3) are respectively constructed in opposite directions to advance the pipe roof (7). S3. Under the support of the advanced pipe roof (7) and the advanced pipe curtain (5), the tunnel is excavated in a dark section. The tunnel is excavated in a dark section with composite lining and the excavation support method is the step-by-step method. S4. After the tunnel excavation section is completed, the open-cut section of the tunnel is constructed in the first shaft (1), and then the first shaft (1) is backfilled.

2. The construction method for a shallow-buried, large-section tunnel passing under a highway over a long distance, as described in claim 1, is characterized in that... The specific construction steps for step S1 are as follows: S11. Level the site and drive the first foundation pit cast-in-place pile and the first high-pressure jet grouting pile to form a water-stop curtain. S12. Excavate the soil, then set up the foundation pit capping beam, and set up the first foundation pit support horizontally at the position of the foundation pit capping beam; S13. After the first foundation pit support reaches the design strength, continue to excavate the soil, then set the foundation pit waist beam, and set the second foundation pit support horizontally at the position of the foundation pit waist beam. S14. After the second foundation pit support reaches the design strength, continue the excavation of soil for cyclic support and excavation steps until the bottom of the initial foundation pit is reached.

3. The construction method for a shallow-buried, large-section tunnel passing under a highway over a long distance, as described in claim 2, is characterized in that: The advanced pipe curtain (5) mentioned in step S22 is a φ720×16mm steel pipe, which is distributed at 110cm on the arch top and constructed using micro-jacking technology. After the jacking construction is in place, fine stone concrete is poured and filled.

4. The construction method for a shallow-buried, large-section tunnel passing under a highway over a long distance, as described in claim 2, is characterized in that: The advanced pipe shed (7) mentioned in step S23 is a φ180×8mm steel pipe shed with a horizontal spacing of 110cm at the arch and a spacing of 30cm between the two side walls.

5. The construction method for a shallow-buried, large-section tunnel passing under a highway over a long distance, as described in claim 1, is characterized in that... The composite lining in step S3 includes initial support and cast-in-place concrete lining. The initial support includes φ42 grouting system anchor pipe (8), double-layer φ8 steel mesh of @15cm×15cm, I25a I-beam arch frame (10), and shotcrete (11). The cast-in-place concrete lining includes 50cm thick grid steel frame concrete lining (13) and 70cm thick reinforced concrete lining (14). The sectional upper and lower step method divides the tunnel excavation section into the first pilot tunnel (31), the second pilot tunnel (32), the third pilot tunnel (33), and the fourth pilot tunnel (34) from left to right. Each of the first pilot tunnel (31), the second pilot tunnel (32), the third pilot tunnel (33), and the fourth pilot tunnel (34) is further divided into upper step and lower step.

6. The construction method for a shallow-buried, large-section tunnel passing under a highway over a long distance, as described in claim 5, is characterized in that... The specific construction steps of the sectional step method in step S3 are as follows: S31. Excavate the upper steps of the first pilot tunnel (31) and the fourth pilot tunnel (34), and then construct the initial support and temporary support of the upper steps and close the working face. S32. Excavate the lower steps of the first pilot tunnel (31) and the fourth pilot tunnel (34), and then construct the initial support and temporary support of the lower steps and close the working face. S33, excavate the upper step of the second guide tunnel (32), then construct the initial support and temporary support of the upper step, and seal the working face; S34. Excavate the lower step of the second guide tunnel (32), and then construct the initial support and temporary support of the lower step and close the working face; S35. Excavate the upper step of the third pilot tunnel (33), and then construct the initial support and temporary support of the upper step and close the working face; S36. Excavate the lower step of the third pilot tunnel (33), and then construct the initial support and temporary support of the lower step and close the working face; S37. Repeat steps S31 to S36 until the tunnel excavation section is completed. Then, remove the shotcrete that temporarily supports the cast-in-place concrete lining to expose the I-beams. S38. Erect the grid steel frame without removing the temporary supports, and pour the grid steel frame concrete lining. S39. After the construction of the grid steel frame concrete lining of the tunnel excavation section is completed and reaches the design strength, the temporary supports are removed section by section, waterproof membrane is laid, and the reinforced concrete lining is constructed using a trolley.

7. The construction method for a shallow-buried, large-section tunnel passing under a highway over a long distance, as described in claim 6, is characterized in that... In step S3, before the tunnel is excavated, the soil in front of the tunnel face is reinforced with full-section curtain grouting.

8. The construction method for a shallow-buried, large-section tunnel passing under a highway over a long distance, as described in claim 6, is characterized in that... Before the excavation of the pilot tunnel in steps S31 and S33, advance small guide pipes (9) are installed in the soil ahead.

9. A construction method for a shallow-buried, large-section tunnel passing under a highway over a long distance, as described in claim 6, characterized in that... The I-beams described in step S37 are exposed for rust removal and rust prevention treatment.

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