A method for staged construction of an underground structure crossing a river

Abstract

The present invention relates to the technical field of underground engineering construction, and discloses a method for staged construction of an underground structure crossing a river. First, a first-stage cofferdam is constructed along the revetment on one side of the river channel, the accumulated water in the first-stage cofferdam is drained and filled with soil, and then a foundation pit retaining structure is constructed and a first-stage underground main structure is constructed. After the construction of the first-stage underground main structure is completed, the first-stage cofferdam is demolished and a second-stage cofferdam is continuously constructed along the extension direction of the first-stage underground main structure. The accumulated water in the second-stage cofferdam is drained and filled with soil, and the second-stage underground main structure is continuously constructed. The above steps are repeated until the underground main structures of each stage are connected as a whole. The retaining structure between two adjacent stages of underground main structures is chiseled and concrete is poured to connect the entire underground main structure as a whole. The present invention ensures the water passing area during the construction of the underground project through staged construction, and ensures the construction safety of the water-passing underground structure and the safety of the main structure after completion.

Description

Technical Field

[0001] The invention relates to the technical field of underground engineering construction, in particular to a phased construction method of a river crossing underground structure. Background Art

[0002] When the underground structure involves crossing a river, it is necessary to set up a river-filling cofferdam to protect the underground structure from being affected by the water flow. If the cofferdam is used to directly cut off the water flow, the river channels on both sides of the cofferdam must be temporarily pumped out to ensure the communication of the water system, which requires a lot of electricity and manpower costs, resulting in increased engineering costs. At the same time, if the river channel is cut off during the flood season, flood disasters are likely to occur, causing the water flow elevation to exceed the cofferdam top elevation and then pour into the subway foundation pit construction area, causing casualties and engineering accidents; the use of phased cofferdam construction can solve the above-mentioned water flow cut-off problem, but the open-cut structure is located in the river and the cofferdam is constructed in stages. If the interface treatment of different construction periods is not in place, water gushing accidents are likely to occur, causing casualties. How to ensure the safe construction of the underground structure crossing the river using phased cofferdams and the structural safety during the operation after completion is an engineering problem that needs to be solved urgently. Summary of the invention

[0003] In order to solve the above technical problems, the purpose of the present invention is to provide a phased construction method for an underground river crossing structure, which can not only ensure the smooth flow of the river and the safety of the foundation pit during the phased cofferdam construction, but also reduce the risk of water leakage during the later operation of the underground structure.

[0004] Based on this, the present invention provides a phased construction method for a river crossing underground structure, which comprises the following steps:

[0005] S1. Build a first-stage cofferdam along the revetment bank on one side of the river;

[0006] S2. Fill the first-phase cofferdam with soil and construct the foundation pit retaining structure, and construct the first-phase underground main structure inside the foundation pit retaining structure;

[0007] S3, constructing a downward-turned beam at the end point of the first-phase underground main structure, wherein the downward-turned beam is located at the bottom of the floor plate of the first-phase underground main structure;

[0008] S4. Construct a temporary blocking wall at the end of the first-phase underground main structure;

[0009] S5. construct a temporary retaining wall at the end of the first-phase underground main structure, wherein the temporary retaining wall is located on the top of the roof of the first-phase underground main structure;

[0010] S6, dismantling the first-phase cofferdam and the foundation pit retaining structure within the first-phase cofferdam, and constructing a second-phase cofferdam in the river channel, wherein the second-phase cofferdam surrounds the end point of the first-phase underground main structure;

[0011] S7. Fill the inside of the second-phase cofferdam, construct the foundation pit retaining structure again, and construct the second-phase underground main structure connected to the first-phase underground main structure within the foundation pit retaining structure;

[0012] S8. Construct a personnel escape hole on the top slab of the second-phase underground main structure, and set a steel ladder pointing to the personnel escape hole on the side wall of the second-phase underground structure;

[0013] S9. Chisel the connection structure between the first-phase underground main structure and the second-phase underground main structure to form a pouring area to be poured. Apply a steel plate waterstop to the pouring area to be poured, process the pouring area to be poured to form a groove, set an expansion waterstop strip at the edge of the groove, and apply a steel plate waterstop to the pouring area to be poured;

[0014] S10. Pour concrete into the pouring area to be poured to form a post-cast strip;

[0015] S11. Seal the personnel escape hole of the second-phase underground main structure, chisel the temporary water retaining wall and the temporary plugging wall, and complete the construction of the water-passing underground structure.

[0016] In some embodiments of the present application, step S3 further includes:

[0017] Construct a protective layer on the top slab of the first-phase underground main structure.

[0018] In some embodiments of the present application, step S8 further includes:

[0019] Construct a protective layer on the top slab of the second-phase underground main structure.

[0020] In some embodiments of the present application, the thickness of the protective layer is 200 mm, and a steel bar mesh with a specification of HPB300, a diameter of 8 mm, and a mesh size of 150 mm is configured in the protective layer.

[0021] In some embodiments of the present application, step S7 further includes:

[0022] Construct MJS waterstop at the joint between the second-phase cofferdam and the foundation pit retaining structure. The diameter of the MJS waterstop is 2 m, and the cement content of the MJS waterstop is 40%.

[0023] In some embodiments of the present application, the construction steps of the first-phase cofferdam and the second-phase cofferdam are as follows:

[0024] Set two rows of steel sheet piles or steel pipe piles, backfill clay between the piles and fix them by tensioning with M20 bolts. The insertion ratio of the steel sheet piles or steel pipe piles is 1:1.

[0025] In some embodiments of the present application, the thickness of the temporary water retaining wall is 400 mm.

[0026] In some embodiments of the present application, the thickness of the temporary plugging wall is 200 mm.

[0027] In some embodiments of the present application, the specifications of the downward-turning beam are 800 mm * 1000 mm.

[0028] In some embodiments of the present application, the size of the personnel escape hole is 1000 mm * 1000 mm.

[0029] A staged construction method for an underground structure crossing a river provided by an embodiment of the present invention, compared with the prior art, has the beneficial effects that:

[0030] In the present application, the underground structure crossing the river is divided into multiple stages and cofferdam construction is carried out for different stages respectively (two stages in this embodiment), effectively ensuring the smoothness of the river channel and avoiding problems such as flood control drainage and water quality deterioration caused by river channel cutoff; further, when the construction of the first-stage underground main structure is completed, a temporary plugging wall is constructed to temporarily plug the access channel of the first-stage underground structure, avoiding water from entering the station main body through the already constructed first-stage access channel when water gushes out at the interface between the first-stage underground structure and the second-stage cofferdam, causing large personnel and property losses. The temporary plugging wall can be chiseled in the later stage without affecting the normal use of the whole structure; furthermore, a downward-turning beam is constructed at the end of the first-stage underground main structure. The downward-turning beam is located at the bottom of the floor slab and can plug the connection between the two when the second-stage underground main structure is connected, reducing the risk of water and sand gushing at the connection; furthermore, a temporary water retaining wall is constructed on the top of the first-stage structure roof, which can effectively avoid the impact of later river channel dredging and the like on the waterproof layer of the station roof and the main structure, protecting the safety of the access channel structure; furthermore, a personnel escape hole is arranged on the roof before the second-stage underground main structure is capped, and a steel climbing ladder is correspondingly configured on the side wall to ensure that the construction personnel of the second-stage underground main structure can quickly transfer and escape in case of a sudden water gushing accident. In this way, the present invention can not only ensure the water passing area when the underground project crossing the river is implemented in stages, but also ensure the construction safety of the water passing underground structure and the safety of the main structure after completion, and has a positive and significant effect on reducing the impact on the surrounding environment, engineering risks, personnel casualties and the risk of later structure leakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a top view of the first-stage cofferdam of some embodiments of the present invention;

[0032] Figure 2 It is a top view of the second-stage cofferdam of some embodiments of the present invention;

[0033] Figure 3 It is Figure 1 The schematic cross-sectional view taken along line A-A in

[0034] Figure 4is Figure 2 the schematic view of the B-B section in

[0035] Figure 5 the schematic connection diagram of the first-phase underground main structure and the second-phase underground main structure;

[0036] Figure 6 is Figure 5 the detail drawing at C in

[0037] Figure 7 the large-scale connection drawing of the foundation pit retaining structure and the temporary water retaining wall of the second-phase cofferdam.

[0038] In the figure, 1. the first-phase cofferdam; 2. the second-phase cofferdam; 3. the foundation pit retaining structure; 4. the first-phase underground main structure; 5. the temporary water retaining wall; 6. the river revetment; 7. MJS water stop; 8. the post-cast strip; 9. the personnel escape hole; 10. the steel climbing ladder; 11. the temporary plugging wall; 12. the down-turned beam; 13. the second-phase underground main structure; 14. the protective layer; 15. the steel plate water stop belt; 16. the swelling water stop strip; 17. the implanted bar. Specific embodiments

[0039] The following combines the drawings and embodiments to further describe the specific embodiments of the present invention in detail. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0040] It should be understood that in the present invention, terms such as "front" and "rear" are used to describe various information, but these information should not be limited to these terms, and these terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present invention, "front" information can also be called "rear" information, and "rear" information can also be called "front" information.

[0041] As Figures 1 to 7 shown, the present invention provides a method for staged construction of an underground structure across a river, and the specific steps are as follows:

[0042] First, construct the first-phase cofferdam 1 along the river revetment 6. The first-phase cofferdam 1 can be constructed with two rows of steel sheet piles or steel pipe piles. The inside of the two rows of piles is backfilled with clay and fixed by tensioning with M20 bolts. The insertion ratio of the steel sheet piles or steel pipe piles is 1:1, that is, the length of the pile inserted into the soil is equal to the exposed length. At the same time, it should be noted that the top of the pile should exceed the flood control water level by more than 1m.

[0043] After the construction of the first-phase cofferdam 1 is completed, fill the soil inside the first-phase cofferdam 1 and construct the foundation pit retaining structure 3. The foundation pit retaining structure 3 is preferably an overlapping pile or a diaphragm wall, etc., which can give consideration to both water stop and soil retaining.

[0044] Excavate the foundation pit within the foundation pit retaining structure 3 to construct the first-phase underground main structure 4. At the same time, roughen the surface of the foundation pit retaining structure 3 and implant steel bars 17 to ensure its effective connection with the first-phase underground main structure 4.

[0045] Furthermore, as Figure 3 and Figure 4 shown, construct a temporary water retaining wall 5 with a thickness of 400 mm on the top slab of the first-phase underground main structure 4. At the same time, the first-phase cofferdam 1 and the second-phase one are also connected to the temporary water retaining wall 5 as a whole to strengthen the water retaining effect.

[0046] Furthermore, the operator can construct a temporary plugging wall 11 with a thickness of 200 mm inside the first-phase underground main structure 4. The temporary plugging wall 11 is a reinforced concrete structure with a concrete grade of C35. At the same time, a down-turned beam 12 is constructed at the construction end of the first-phase underground main structure 4. The down-turned beam 12 is located at the bottom of the bottom slab of the first-phase underground main structure 4, and its size is 800 mm * 1000 mm. For the top slab of the first-phase underground main structure 4, a 200-mm-thick protective layer 14 is constructed on its top to prevent damage to the top slab during river dredging. The protective layer 14 is made of C35 concrete and is internally provided with a steel mesh of HPB300, with a diameter of 8 mm and a mesh size of 150 mm. When the anti-floating of the first-phase underground main structure 4 does not meet the requirements, the retaining structure can also be anchored to the 200-mm-thick protective layer 14 above the top slab to play an anti-floating role.

[0047] After the construction within the first-phase cofferdam 1 is completed, the first-phase cofferdam 1 can be demolished and the second-phase cofferdam 2 can be continuously constructed in the river. Obviously, for the part of the first-phase cofferdam 1 that coincides with the second-phase cofferdam 2, the original first-phase cofferdam 1 can be retained and used as the second-phase cofferdam 2. After the second-phase cofferdam 2 is closed, continue to pump water and backfill the soil inside the second-phase cofferdam 2, and construct the foundation pit retaining structure 3 to complete the foundation pit excavation and the construction of the second-phase underground main structure 13.

[0048] Furthermore, in order to prevent leakage at the interface between the first-phase and second-phase retaining structures, an MJS water stop 7 with a diameter of 2 m can be constructed at the joint on both sides for water stop. The MJS cement content is 40%, and the construction is completed by 120° swing jet grouting.

[0049] Furthermore, when the second-phase underground main structure 13 is constructed up to the side wall and roof positions, a personnel escape hole 9 can be preset on the roof. The size of this hole is preferably 1000mm * 1000mm, and a steel climbing ladder 10 is embedded in the side wall accordingly. The steel climbing ladder 10 can be made of Q23B round steel with a diameter of 28mm and embedded in the side wall. In case of a sudden water inrush accident, the operators in the second-phase underground main structure 13 can evacuate through this steel climbing ladder 10 and across the personnel escape hole 9, preventing the operators from being trapped inside the second-phase underground main structure 13 by water. Corresponding to the first-phase underground main structure 4, a 200mm-thick concrete protective layer 14 is also constructed on the roof of the second-phase underground main structure 13, thus preventing damage to the roof during river dredging.

[0050] After the construction of both the first-phase underground main structure 4 and the second-phase underground main structure 13 is completed, the retaining structure at the joint between the two needs to be chiseled until the bottom slab is exposed. At this time, since the down-turned beam 12 has been constructed at the end of the first-phase underground main structure 4, the probability of water leakage from below the first-phase base is greatly reduced; after the retaining structure is chiseled, a pouring area is formed. Construction workers can pour concrete here to form a post-cast strip 8. Specifically, steel waterstop belts 15 are buried in the structures such as the roof, bottom slab, and side wall of the pouring area, as Figure 7 shown.

[0051] Furthermore, a groove is also provided at the post-cast strip 8. The size of the groove is 100mm, and the height is about 1 / 3 of the bottom slab thickness, so as to increase the seepage path. At the same time, an expanding waterstop strip 16 is arranged inside the groove. The expanding waterstop strip 16 expands when encountering water and can further prevent the seepage water at the joint from seeping into the post-cast strip 8.

[0052] Finally, after the first-phase underground main structure 4 and the second-phase underground main structure 13 are completely enclosed, the personnel escape hole 9 reserved on the roof of the second-phase underground main structure 13 is closed, and a 200mm-thick concrete protection board is applied to the closed position. Subsequently, the temporary water retaining wall 5 and the temporary plugging wall 11 of the first-phase underground main structure 4 are chiseled, and the construction of the entire water-passing underground structure is completed.

[0053] It should be noted that the purpose of this application is to provide a phased construction method. On this basis, the operator can adjust the number of construction phases to more than two according to the river width and the construction length of the underground main structure, that is, there are also cases of multi-phase cofferdam construction in this application. At this time, the first-phase cofferdam 1 and the last-phase cofferdam 1 are located at both ends of the river respectively, and the other-phase cofferdams are all located in the river. Obviously, in order to ensure the waterproof effect, a down-turned beam 12, a temporary water retaining wall 5, and a temporary plugging wall 11 need to be set at the connection of any two adjacent-phase underground main structures. The specific setting form will not be elaborated here.

[0054] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and substitutions can be made, and these improvements and substitutions should also be regarded as the protection scope of the present invention.

Claims

1. A method for staged construction of an underground structure crossing a river, characterized in that, It includes the following steps: S1. Construct the first-stage cofferdam along the revetment on one side of the river course , the height of the first-phase cofferdam exceeds the flood control water level by more than 1m ; S2. Fill the inside of the first-phase cofferdam and construct the foundation pit retaining structure, and construct the first-phase underground main structure inside the foundation pit retaining structure; S3. Construct a down-turned beam at the end of the first-phase underground main structure. The down-turned beam is located at the bottom of the floor slab of the first-phase underground main structure. Construct a protective layer on the top slab of the first-phase underground main structure and anchor the protective layer to the foundation pit retaining structure; S4. Construct a temporary plugging wall at the end of the first-phase underground main structure; S5. Construct a temporary water retaining wall at the end of the first-phase underground main structure. The temporary water retaining wall is located at the top of the top slab of the first-phase underground main structure; S6. Demolish the first-phase cofferdam and the foundation pit retaining structure within the first-phase cofferdam, and construct a second-phase cofferdam in the river channel. the height of the second-phase cofferdam exceeds the flood control water level by more than 1m, The second-phase cofferdam surrounds the end point of the first-phase underground main structure. S7. Fill the inside of the second-phase cofferdam, construct the foundation pit retaining structure again, construct the second-phase underground main structure connected to the first-phase underground main structure inside the foundation pit retaining structure, and construct MJS water stop at the joint between the second-phase cofferdam and the foundation pit retaining structure. The diameter of the MJS water stop is 2m, and the cement content of the MJS water stop is 40%; S8. Construct a personnel escape hole on the top slab of the second-phase underground main structure, and set a steel ladder pointing to the personnel escape hole on the side wall of the second-phase underground structure. Construct a protective layer on the top slab of the second-phase underground main structure and anchor the protective layer to the foundation pit retaining structure; S9. Chisel the connection structure between the first-phase underground main structure and the second-phase underground main structure to form a pouring area to be poured. Apply a steel plate water stop to the pouring area to be poured, process the pouring area to be poured to form a groove, set an expansion water stop strip at the edge of the groove, and apply a steel plate water stop to the pouring area to be poured; S10. Pour concrete into the pouring area to be poured to form a post-cast strip; S11. Plug the personnel escape hole of the second-phase underground main structure, chisel the temporary water retaining wall and the temporary plugging wall, and complete the construction of the water-passing underground structure.

2. The method for staged construction of an underground structure crossing a river according to claim 1, characterized in that, The thickness of the protective layer is 200mm, and a steel bar mesh with a specification of HPB300, a diameter of 8mm, and a mesh size of 150mm is arranged in the protective layer.

3. The method for staged construction of an underground structure crossing a river according to claim 1, characterized in that, The construction steps of the first-phase cofferdam and the second-phase cofferdam are as follows: Set two rows of steel sheet piles or steel pipe piles, backfill clay between the piles and fix them with M20 bolts in tension. The insertion ratio of the steel sheet piles or steel pipe piles is 1:

1.

4. The method for staged construction of an underground structure crossing a river according to claim 1, characterized in that, The thickness of the temporary water retaining wall is 400mm.

5. The method for staged construction of an underground structure crossing a river according to claim 1, characterized in that, The thickness of the temporary plugging wall is 200mm.

6. The method for staged construction of an underground structure crossing a river according to claim 1, characterized in that, The specification of the down-turned beam is 800mm*1000mm.

7. The method for staged construction of an underground structure crossing a river according to claim 1, characterized in that, The size of the personnel escape hole is 1000mm*1000mm.

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