Construction Method for Widening Existing Cross-River Tunnel

Abstract

The present invention provides a construction method for widening an existing river-crossing tunnel, which constructs high and low-position bored piles underwater, utilizes groove-shaped prefabricated panels and high-position bored piles and long and short mortise and tenon cofferdams to seal and connect, and pumps out water and drains mud in the cofferdam to form a construction environment for tunnel widening. In addition, utilizing the main function of the groove-shaped prefabricated panels in construction, a concave-shaped ship channel is presented in the river, which is convenient for the passage of ships and vehicles. This scheme utilizes the construction method of the concave groove-shaped prefabricated panels and the cofferdam, which neither affects the tunnel widening construction in the cofferdam nor the normal passage of ships on the river surface, which not only improves the construction efficiency, but also reduces the construction cost due to the unnecessary construction across the entire river surface; on the other hand, the groove-shaped prefabricated panels can be disassembled and reused, and can be used many times, which conforms to the concept of economical and green construction.

Description

Technical Field

[0001] The invention relates to pile foundation engineering and water conservancy engineering, and in particular to a construction method for widening an existing river-crossing tunnel. Background Art

[0002] With the improvement of people's living standards and the development of my country's modernization drive, transportation roads are to a certain extent related to local economic conditions. A series of examples, from the construction of the Qinghai-Tibet Railway to the opening of the Hong Kong-Zhuhai-Macao Bridge in recent years, all show that transportation projects play an important role in social construction.

[0003] Today, cities are moving towards green optimization and are faced with more and more vehicles on the roads and frequent traffic problems. Road widening is also included in the plan. However, the maturity of cross-river tunnel technology in recent years can shorten the driving distance like land, but it faces a problem like land road widening. In addition, the construction of cross-river tunnels often requires the entire cross-river surface to be closed for construction, which makes it impossible for ships on the river to pass.

[0004] In response to the above problems, we are currently seeking a method that can take comprehensive factors into consideration, so that we can carry out the construction of existing cross-river tunnels without affecting the passage of ships on the river, and conform to the economic and green concept while improving construction efficiency. Summary of the invention

[0005] The purpose of the present invention is to provide a construction method for widening an existing river-crossing tunnel. The scheme can ensure the widening construction of the existing tunnel without affecting the passage of ships on the river through the construction of groove-shaped prefabricated panels and cofferdams.

[0006] The present application provides a construction method for widening an existing river-crossing tunnel, comprising the following steps:

[0007] Step 1: Underwater pile foundation construction on both sides of the existing cross-river tunnel: Multiple rows of low-position bored piles are evenly, continuously and symmetrically constructed on both sides of the existing cross-river tunnel. The pile top elevation of the low-position bored piles is consistent with the bottom of the existing cross-river tunnel. High-position bored piles are constructed between the low-position bored piles and the short cofferdam to be constructed later.

[0008] Step 2: Cofferdam construction: The specific steps are as follows:

[0009] S1: Short cofferdam construction: short mortise and tenon steel sheet piles are hoisted and lowered, and the bottom of the short mortise and tenon steel sheet piles are slowly pressed vertically to 1 / 2 of the depth of the low-position bored piles. After the short mortise and tenon steel sheet piles are spliced, a short cofferdam is formed. The short cofferdam is located outside the high-position bored piles, and a water stop pad is placed above the short cofferdam.

[0010] S2: The prepared trough-shaped prefabricated panels are hoisted to the upper end of the high-position bored piles, and the reserved holes on the bottom plate of the trough-shaped prefabricated panels are overlapped with the first embedded reinforcement exposed at the top of the high-position bored piles, and the reserved holes are sealed; the water stop pad at the upper end of the short cofferdam is in sealing contact with the bottom of the trough-shaped prefabricated panels; the sealing connectors are installed in the reserved sealing grooves at both ends of the axial direction of the side plates of the trough-shaped prefabricated panels, and the top of the sealing connector is consistent in height with the top of the side plates of the trough-shaped prefabricated panels, and the bottom of the sealing connector is consistent in depth with the bottom of the short cofferdam;

[0011] S3: Long cofferdam construction: Long mortise and tenon steel sheet piles are overlapped on the outside of the sealing joints to form a long cofferdam. The depth of the lower end of the long cofferdam is consistent with the depth of the short cofferdam, and the upper end of the long cofferdam is higher than the river surface;

[0012] S4: Set up horizontal supports between the long cofferdams on both sides and pump water out of the cofferdams;

[0013] S5: The silt at the bottom of the riverbed is excavated to below the bottom of the existing cross-river tunnel, and the upper end of the low-position bored pile is raised above the silt at the bottom of the riverbed;

[0014] S6: Roughen the top pile heads of the low-position bored piles on both sides of the existing cross-river tunnel, and cast bottom concrete between the existing cross-river tunnel and the cofferdam to form a bottom concrete structure. The upper surface of the bottom concrete structure is consistent with the bottom elevation of the existing cross-river tunnel;

[0015] Step 3: Planting reinforcement in the existing bottom plate and widening the bottom plate: Plant the first horizontal reinforcement at the bottom of the outer wall of the existing cross-river tunnel. The length of the first reinforcement is the width of the widened tunnel. After the first reinforcement is planted, extend the first longitudinal reinforcement pre-buried at the top of the low-position bored pile to the first reinforcement and weld it to the first reinforcement. Finally, pour concrete on the bottom cover concrete structure to form the widened bottom plate.

[0016] Step 4: Cast-in-place widening side wall construction: on the side of the widening floor away from the existing cross-river tunnel, perform steel bar binding and formwork operations for the widening side wall, and pour concrete to complete the construction of the cast-in-place widening side wall. A second longitudinal reinforcement is reserved at the top of the external widening side wall.

[0017] Step 5: First, implant the third longitudinal reinforcement on the top of the middle partition wall of the existing cross-river tunnel, and then close the existing cross-river tunnel on one side to ensure the temporary two-way normal traffic of the existing cross-river tunnel on the other side;

[0018] Step 6: For one side of the closed existing cross-river tunnel, the existing top plate and the existing side wall on one side of the middle partition wall of the existing cross-river tunnel are dismantled in sequence;

[0019] Step 7: Build a widened top plate template. The widened top plate template is supported by supporting columns. The upper part of one side of the widened top plate template is flush with the elevation of the existing middle partition wall. The lower part of the other side of the widened top plate template is consistent with the elevation of the widened side wall. The second longitudinal reinforcement at the top of the widened side wall extends to the top of the widened top plate template.

[0020] Step 8: Carry out road surface construction on the widened bottom plate of the closed section;

[0021] Step 9: Open the tunnel on the side where the widened top plate template has been set up for traffic, and then close the existing cross-river tunnel on the other side;

[0022] Step 10: Repeat steps 6 to 8 to complete the installation of widened top plate templates on both sides of the existing cross-river tunnel, and open the existing cross-river tunnels on both sides to traffic;

[0023] Step 11: Complete the construction of the widened top plate with prestress through the post-tensioning construction process;

[0024] Step 12: Remove and widen the top plate formwork;

[0025] Step 13: Backfill the fat trough between the widened side wall and the cofferdam, inject water into the cofferdam and remove the horizontal support, trough-shaped prefabricated panels, long cofferdam and short cofferdam in turn to complete the widening construction of the existing cross-river tunnel.

[0026] Preferably, in step one, the horizontal spacing between the outermost rows of low-position bored piles and high-position bored piles on both sides of the existing cross-river tunnel is not less than 3m, the horizontal spacing between the high-position bored piles and the short cofferdam to be constructed subsequently is not less than 3m, the tops of the high-position bored piles are located at 1 / 2 of the river water depth, and the pile ends of the low-position bored piles and the high-position bored piles are deep into the bearing layer.

[0027] Preferably, in step 2, the width between the cofferdams on both sides of the existing cross-river tunnel is not less than 6 times the width of a single lane of the existing cross-river tunnel, and the horizontal distance between the cofferdam and the widened side wall to be constructed subsequently is not less than 6m.

[0028] Preferably, in step 2, the trough-shaped precast panel is a steel structure with a "U"-shaped cross-section; the trough-shaped precast panel includes a bottom plate and side plates on both sides of the bottom plate, and steel cable inclined supports are installed between the side plates and the bottom plate. The distance between the reserved sealing grooves at both ends of the side plates of the trough-shaped precast panel is the distance between the long cofferdams on both sides of the existing cross-river tunnel, and the height of the trough-shaped precast panel is the difference between the heights of the long cofferdam and the short cofferdam.

[0029] Preferably, in step 2, the short mortise and tenon steel sheet piles are spliced ​​together by means of a mortise and tenon structure; and the long mortise and tenon steel sheet piles are spliced ​​together by means of a mortise and tenon structure.

[0030] Preferably, in step seven, the widened top plate template is supported by three supporting columns, among which the supporting column in the middle is the main column and the supporting columns on both sides are secondary columns; a lighting lamp is provided under the widened top plate template.

[0031] Preferably, in step 12, when removing the widened top plate formwork, the widened top plate formwork and supporting columns on both sides of the existing middle partition wall are removed in turn according to the principle of one side being open and the other side being closed, and then the tunnels on both sides are restored to traffic.

[0032] The beneficial effects of the present invention are:

[0033] (1) The present invention organically combines technologies such as pile foundation, cofferdam, cast-in-place reinforced concrete, and prestressing to provide a technically feasible construction plan for widening existing cross-river tunnels.

[0034] (2) By setting up pile foundations in the widening section, the ability of the existing cross-river tunnel to resist uneven settlement at the junction of the new and old cross sections after widening is improved.

[0035] (3) In the present invention, the long cofferdams and short cofferdams on both sides and the "U"-shaped trough-shaped prefabricated panels together form a concave cofferdam structure. During the construction process, the trough-shaped prefabricated panels can be used as a channel for ships to pass through, thereby ensuring the normal passage of ships.

[0036] (4) In the present invention, during the widening process of the cross-river tunnel, at least half of the tunnel can always be open to traffic, and the full section of the widened tunnel can be opened to traffic during the pouring construction of the widened top plate, which has significant technical advantages.

[0037] (5) In the present invention, the widened top plate with prestress is cast by the post-tensioning construction process, which can effectively resist the deformation caused by the upper load and has significant technical advantages.

[0038] (6) The trough-shaped prefabricated panels can be disassembled and reused, and can be used multiple times, which conforms to the economical and green construction concept. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of low-position bored piles in section AA

[0040] Figure 2 Schematic diagram of BB section high-position bored pile

[0041] Figure 3 Schematic diagram of the distribution of high and low bored piles

[0042] Figure 4 Schematic diagram of the location of low-level bored piles and long cofferdams in section AA

[0043] Figure 5Schematic diagram of the high and low bored piles and short cofferdam locations in the BB section

[0044] Figure 6 A schematic diagram of the high-position bored piles and cofferdam distribution

[0045] Figure 7 Schematic diagram of the short mortise and tenon steel sheet pile provided for this scheme

[0046] Figure 8 Schematic diagram of the long mortise and tenon steel sheet pile provided for this solution

[0047] Fig. 9 Schematic diagram of the trough prefabricated panel provided for this scheme

[0048] Fig.10 Schematic diagram of the distribution of the grooved prefabricated panels and high-position bored piles provided for this scheme

[0049] Fig.11 A three-dimensional schematic diagram of the overlap between the grooved prefabricated slab and the high-position bored piles provided for this scheme

[0050] Fig.12 A three-dimensional schematic diagram of the sealing connector provided for this solution

[0051] Fig.13 Schematic diagram of the sealed overlap between the trough prefabricated panel and the short cofferdam provided for this scheme

[0052] Fig.14 Top view of the grooved prefabricated panels and their overlapping structures provided for this scheme

[0053] Fig.15 A three-dimensional schematic diagram of the existing concave structure of the cross-river tunnel

[0054] Fig.16 This is a schematic diagram of the front elevation of the existing concave structure of the cross-river tunnel

[0055] Fig.17 Schematic diagram of pumping and dredging in the cofferdam of section AA

[0056] Fig.18 Schematic diagram of the AA section corbel and horizontal support after installation

[0057] Fig.19 Schematic diagram of the bottom sealing after pouring concrete in the cofferdam of section AA

[0058] Fig. 20 Schematic diagram of horizontal reinforcement at the bottom of the wall on both sides of the existing tunnel in the BB section cofferdam and welding with the longitudinal reinforcement at the end of the low-position bored pile

[0059] Fig.21Schematic diagram of the BB section cofferdam after the concrete pouring and widening of the bottom plate

[0060] Fig. 22 Schematic diagram of the cast-in-place widened side wall at the end of the widened bottom plate in the BB section cofferdam

[0061] Fig.23 Schematic diagram of vertical reinforcement of the existing tunnel partition wall in the BB section cofferdam

[0062] Fig.24 Schematic diagram of removing the roof and side wall of one side of the existing tunnel in the BB section cofferdam and leaving only one side of the tunnel open Fig.25 Schematic diagram of the top formwork and support columns and lighting installation for the BB section cofferdam tunnel widening Fig.26 Schematic diagram of the temporary opening and widening of the road surface below the top formwork in the BB section cofferdam

[0063] Fig. 27 Schematic diagram of the temporary opening of a tunnel with a top plate formwork in the BB section cofferdam

[0064] Fig.28 Schematic diagram of the tunnel roof constructed using post-tensioning method within the BB section cofferdam

[0065] Fig.29 Schematic diagram of the removal of the top plate formwork and lighting for the widening of the tunnel inside the BB section cofferdam

[0066] Fig.30 Schematic diagram of backfilling the fertilizer tank in section AA and injecting water into the cofferdam to remove the horizontal support

[0067] Fig.31 The final schematic diagram of the existing cross-river tunnel after widening

[0068] Fig.32 The overall process flow chart of the widening construction and method of the existing cross-river tunnel in this scheme is marked with the following: 1- low-position bored cast-in-place piles; 2- high-position bored cast-in-place piles; 3- short cofferdam; 4- long cofferdam; 5- short-type mortise and tenon steel sheet piles; 6- long-type mortise and tenon steel sheet piles; 7- grooved prefabricated panels; 8- reserved sealing grooves; 9- cable inclined support; 10- reserved holes; 11- first embedded reinforcement; 12- rubber plug; 13- water-stop pad; 14- sealing connector; 15- horizontal support; 16- corbel; 17- bottom sealing concrete; 18- second embedded reinforcement; 19- first longitudinal reinforcement; 20- widened bottom plate; 21- widened side wall; 22- second longitudinal reinforcement; 23- middle partition wall; 24- third longitudinal reinforcement; 25- main column; 26- secondary column; 27- lighting; 28- widened top plate formwork; 29- widened top plate; 30- graded crushed stone. DETAILED DESCRIPTION

[0069] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention. The overall flow chart of the scheme is shown in Fig.32 As shown, the specific implementation steps include the following:

[0070] Step 1: Underwater pile foundation construction on both sides of the existing cross-river tunnel: With the help of temporary pile-driving boats, combined with Figure 1 , 3 As shown, multiple rows of low-position bored piles 1 are evenly, continuously and symmetrically constructed on both sides of the existing cross-river tunnel, and the pile top elevation of the low-position bored piles 1 is consistent with the bottom of the existing cross-river tunnel. Figure 2 , 5 As shown in Figure 6, at the concave construction site of the existing cross-river tunnel, a single row of high-position bored piles 2 is constructed evenly and symmetrically between the low-position bored piles 1 and the short cofferdam 3 to be constructed later. The horizontal spacing between the outermost rows of low-position bored piles 1 and high-position bored piles 2 on both sides of the existing cross-river tunnel is not less than 3m, the horizontal spacing between the high-position bored piles 2 and the short cofferdam 3 to be constructed later is not less than 3m, and the horizontal distance between the low-position bored piles 1 and the cofferdam is not less than 6m. The top of the high-position bored pile 2 is located at 1 / 2 of the river water depth, and the pile ends of the low-position bored piles 1 and the high-position bored piles 2 penetrate into the bearing layer.

[0071] Step 2: Construction of the concave cofferdam on the river surface: The cofferdam consists of a short cofferdam and a long cofferdam. The width of the cofferdams on both sides of the existing cross-river tunnel is not less than 6 times the width of the single channel of the existing cross-river tunnel, and the horizontal distance between the cofferdam and the widened side wall 21 to be constructed later is not less than 6m. The cofferdam is constructed in the middle first and then on both sides, including the construction of the short cofferdam 3, the production and hanging of the trough-shaped prefabricated board 7, the construction of the long cofferdam 4, the pumping and sealing of the cofferdam, the dredging of the riverbed, and the rapid bottom sealing construction. The specific steps are as follows:

[0072] 2.1 Construction of short cofferdam 3: The construction vessel hoists and places short mortise and tenon steel sheet piles 5. The short mortise and tenon steel sheet piles 5 are as follows: Figure 7 The bottom end of the short mortise and tenon steel sheet pile 5 is slowly pressed vertically to 1 / 2 of the depth of the low-position bored pile 1. Figure 5 The short mortise and tenon steel sheet piles 5 are connected by the mortise and tenon structure. After the short mortise and tenon steel sheet piles 5 are connected by the mortise and tenon structure, a short cofferdam 3 is formed. The short cofferdam 3 is located outside the high-position bored pile 2. A water stop pad 13 is placed above the short cofferdam 3. Fig.13As shown. The short mortise and tenon steel sheet pile 5 includes a male structure and a female structure. The male structure is provided with convex strips protruding outward on both sides, and the female structure is provided with grooves matching the convex strips on both sides. When the short mortise and tenon steel sheet pile 5 is spliced, the male structure and the female structure are alternately arranged in sequence, and the splicing between the short mortise and tenon steel sheet piles 5 is achieved by the cooperation between the convex strips on the male structure and the grooves on the female structure.

[0073] 2.2 The production and hanging of the trough-shaped prefabricated plate 7 are as follows:

[0074] 2.2.1 As Fig. 9 As shown, the overall processing of the trough-type precast panel 7 is completed in the factory. The trough-type precast panel 7 is a steel structure with a "U"-shaped cross section. The trough-type precast panel 7 includes a bottom plate and side plates located on both sides of the bottom plate. The bottom plate of the trough-type precast panel 7 is provided with reserved holes 10, and steel cable inclined supports 9 are installed between the side plates and the bottom plate to resist deformation caused by water pressure. Reserved sealing grooves 8 are provided at both axial ends of the side plates of the trough-type precast panel 7. The reserved sealing grooves 8 are perpendicular to the bottom plate to facilitate the installation of sealing connectors 14. The distance between the reserved sealing grooves 8 at both ends of the side plates of the trough-type precast panel 7 is the distance between the long cofferdams 4 on both sides of the existing cross-river tunnel. The height of the trough-type precast panel 7 is the difference between the heights of the long cofferdam 4 and the short cofferdam 3, and the height is not less than 5m. The top of the trough-type precast panel 7 is flush with the top of the long cofferdam 7, and the bottom plate width of the trough-type precast panel 7 is twice the height of the side plate.

[0075] 2.2.2 The grooved prefabricated panel 7 is transported to the site by a construction ship for hanging and lowering. The grooved prefabricated panel 7 is hung and lowered to the upper end of the high-position bored pile 2. The reserved hole 10 is overlapped with the first embedded reinforcement 11 exposed at the top of the high-position bored pile 2. After the overlap is completed, the reserved hole 10 is sealed with a rubber plug 12. Fig.10 , 11 As shown; the water stop pad 13 at the upper end of the short cofferdam 3 is in sealing contact with the bottom of the grooved prefabricated plate 7, and the water stop pad 13 plays a role in sealing and water stopping;

[0076] 2.2.3 The structure of the sealing connector 14 is as follows Fig.12 As shown; the sealing connector 14 is installed in the reserved sealing groove 8 at both ends of the axial direction of the groove-shaped prefabricated plate 7 side plate, the top of the sealing connector 14 is consistent with the top height of the groove-shaped prefabricated plate 7 side plate, and the bottom of the sealing connector 14 is consistent with the bottom end 3 of the short cofferdam, as shown Fig.13 shown.

[0077] 2.3 Construction of long cofferdam 4: The construction ship hoists and places long mortise and tenon steel sheet piles 6. The structure of the long mortise and tenon steel sheet piles 6 is as follows: Figure 8 The long mortise and tenon steel sheet piles 6 are overlapped in sequence on the outside of the sealing joint 14 to form a long cofferdam 4. The depth of the lower end of the long cofferdam 4 is consistent with the depth of the short cofferdam 3. The upper end of the long cofferdam 4 is higher than the river surface. Fig.15 , 16 As shown. Among them, the long mortise and tenon steel sheet piles 6 are also spliced ​​by the mortise and tenon structure. The structure of the long mortise and tenon steel sheet piles 6 is consistent with that of the short mortise and tenon steel sheet piles 5. The long mortise and tenon steel sheet piles 6 also include a male structure and a female structure. The splicing method of the long mortise and tenon steel sheet piles 6 is the same as that of the short mortise and tenon steel sheet piles 5; the length of the long mortise and tenon steel sheet piles 6 is greater than that of the short mortise and tenon steel sheet piles 5. Among them, the long cofferdams and short cofferdams on both sides and the "U"-shaped trough-shaped prefabricated panels 7 together form a concave cofferdam structure. During the construction process, the trough-shaped prefabricated panels 7 can be used as a passage for ships to pass through, thereby ensuring the normal passage of ships.

[0078] 2.4 Pumping out water from the cofferdam, sealing it, and setting up horizontal supports 15: Combined with what is shown in 17 and 18, the axial ends of the cofferdam are sealed, and horizontal supports 15 are set between the long cofferdams 4 on both sides. Specifically, referring to the conventional practice of horizontal support for cofferdams, water is pumped out from the cofferdam by a construction vessel, and at least two horizontal supports 15 are set up by installing corbels 16 on the long cofferdams 4 while pumping water.

[0079] 2.5 Riverbed dredging: Use river construction boats to dredge the riverbed, dig the mud at the bottom of the riverbed to below the bottom of the existing cross-river tunnel, and make the upper end of the low-position bored pile 1 higher than the mud at the bottom of the riverbed. During the construction process, check the seepage problem at all times. The final structure is as follows: Fig.18 shown.

[0080] 2.6 Rapid bottom sealing construction: Set up a river surface concrete mixing station and pumping device, roughen the top pile heads of the low-position bored piles 1 on both sides of the existing cross-river tunnel, and pour the bottom sealing concrete 17 between the existing cross-river tunnel and the concave cofferdam to form a bottom sealing concrete structure. The upper surface of the bottom sealing concrete structure is consistent with the bottom elevation of the existing cross-river tunnel. The bottom sealing concrete structure can also be used as a cushion layer for widening the bottom plate, such as Fig.19 shown.

[0081] Step 3: Plant reinforcement on the existing base plate and widen the base plate 20: Fig. 20 As shown, a second horizontal embedded reinforcement 18 is implanted at the bottom of the outer side wall of the existing cross-river tunnel. The length of the second embedded reinforcement 18 is the width of the widened tunnel. After the second embedded reinforcement 18 is implanted, the first longitudinal reinforcement 19 pre-buried at the top of the low-position bored pile 1 is extended to the second embedded reinforcement 18 and welded to the second embedded reinforcement 18. Finally, concrete is poured and cured above the bottom cover concrete structure to form a widened bottom plate 20. Fig.21 shown.

[0082] Step 4: Construction of cast-in-place widened side wall 21: The widened side wall 21 is reinforced and molded on the side of the widened bottom plate 20 away from the existing cross-river tunnel. The widened side wall 21 is reinforced with a second longitudinal reinforcement 22, and then poured with concrete and maintained to complete the construction of the cast-in-place widened side wall 21. After the widened side wall 21 is poured, the second longitudinal reinforcement is exposed from the top of the outer widened side wall 21. Fig. 22 shown.

[0083] Step 5: Seal and open the existing cross-river tunnel: First, implant the third longitudinal reinforcement 24 on the top of the middle partition wall 23 of the existing cross-river tunnel, and extend the upper end of the third longitudinal reinforcement 24 to the height where the widened top plate 29 is located. Then, seal the existing cross-river tunnel on one side to ensure the temporary two-way normal traffic of the existing cross-river tunnel on the other side. Fig.23 shown.

[0084] Step 6: Dismantling the existing roof and side walls of the closed tunnel: For one side of the closed existing cross-river tunnel, dismantle the existing roof and side walls of the middle partition wall 23 of the existing cross-river tunnel in the order of first the roof and then the side walls. Fig.24 shown.

[0085] Step 7, erecting the widened top plate formwork 28 of the closed tunnel: erect the widened top plate formwork 28 and the corresponding three supporting columns, and the widened top plate formwork 28 is supported by the supporting columns. The upper part of one side of the widened top plate formwork 28 is flush with the elevation of the existing middle partition wall 23, and the lower part of the other side of the widened top plate formwork 28 is consistent with the elevation of the widened side wall 21. Among the three supporting columns, the supporting column in the middle is the main column 25, and the supporting columns on both sides are secondary columns 26. A lighting lamp 27 is provided below the widened top plate formwork 28, and the second longitudinal reinforcement 22 at the top of the widened side wall 28 extends to the top of the widened top plate formwork 28, as shown in FIG. Fig.25 shown.

[0086] Step 8: Construction of the driving road surface of the widened bottom plate 20: Referring to the construction process of the driving road surface in the tunnel, the driving road surface construction is carried out on the widened bottom plate 20 of the closed section.

[0087] Step 9: Open the tunnel with the widened roof template 28: Open the tunnel on one side where the widened roof template 28 has been set up, and then close the existing cross-river tunnel on the other side. Fig.26 shown.

[0088] Step 10, repeating steps 6 to 8: Repeating steps 6 to 8, completing the erection of widened top plate templates 28 on both sides of the existing cross-river tunnel, and opening the existing cross-river tunnels on both sides to traffic, such as Fig. 27 shown.

[0089] Step 11: Construction of widened top plate 29: Through post-tensioning construction technology, the widened top plate 29 is poured with concrete and post-tensioned, and then cured and formed to complete the construction of the widened top plate 29 with prestress. Fig.28 shown.

[0090] Step 12: Dismantling the widened roof template 28: According to the principle of one side being open and the other side being closed, the widened roof template 28 and supporting columns on both sides of the existing middle partition wall 23 are dismantled in sequence, and then the tunnels on both sides are restored to traffic. Fig.29 shown.

[0091] Step 13: Backfilling the fertilizer trough and removing the cofferdam: Fig.30 As shown in FIG. 1 , firstly, graded crushed stone 30 is used to backfill the widened trough between the side wall 21 and the concave cofferdam, and then, referring to the conventional method of cofferdam removal, water is injected into the concave cofferdam and the horizontal support 15, the trough prefabricated plate 7, the long cofferdam 4 and the short cofferdam 3 are removed in sequence to complete the widening construction of the existing cross-river tunnel. Fig.31 shown.

[0092] Those skilled in the art should understand that, in the disclosure of the present invention, the orientation or position relationship indicated by the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the orientation or position relationship shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0093] It is to be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the element may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0094] Although more professional terms are used in this article, the possibility of using other terms is not excluded. These terms are used only to more conveniently describe and explain the essence of the present invention; interpreting them as any additional restrictions is contrary to the spirit of the present invention.

[0095] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that are the same or similar to those of the present application fall within the protection scope of the present invention.

Claims

1. A construction method for widening an existing river-crossing tunnel, characterized in that: The specific steps include: Step 1: Underwater pile foundation construction on both sides of the existing cross-river tunnel: Multiple rows of low-position bored piles (1) are uniformly, continuously and symmetrically constructed on both sides of the existing cross-river tunnel, the pile top elevation of the low-position bored piles (1) is consistent with the bottom of the existing cross-river tunnel, and high-position bored piles (2) are constructed between the low-position bored piles (1) and the short cofferdam (3) to be constructed later; Step 2: Concave cofferdam construction: The specific steps are as follows: S1: Construction of short cofferdam (3): short mortise and tenon steel sheet piles (5) are hoisted and lowered, and the bottom end of the short mortise and tenon steel sheet piles (5) is slowly pressed vertically to 1 / 2 of the depth of the low-position bored piles (1). After the short mortise and tenon steel sheet piles (5) are spliced, a short cofferdam (3) is formed. The short cofferdam (3) is located outside the high-position bored piles (2), and a water stop pad (13) is placed above the short cofferdam (3); S2: The prepared trough-shaped prefabricated panel (7) is hoisted to the upper end of the high-position bored pile (2), the reserved hole (10) on the bottom plate of the trough-shaped prefabricated panel (7) is overlapped with the first embedded reinforcement (11) exposed at the top of the high-position bored pile (2), and the reserved hole (10) is sealed; the water stop pad (13) at the upper end of the short cofferdam (3) is in sealing contact with the bottom of the trough-shaped prefabricated panel (7); the sealing connector (14) is installed in the reserved sealing grooves (8) at the axial ends of the side plate of the trough-shaped prefabricated panel (7), the top of the sealing connector (14) is consistent in height with the top of the side plate of the trough-shaped prefabricated panel (7), and the bottom of the sealing connector (14) is consistent in depth with the bottom of the short cofferdam (3); S3: Construction of the long cofferdam (4): Long mortise and tenon steel sheet piles (6) are overlapped in sequence on the outside of the sealing joint (14) to form the long cofferdam (4). The depth of the lower end of the long cofferdam (4) is consistent with the depth of the short cofferdam (3), and the upper end of the long cofferdam (4) is higher than the river surface; S4: Horizontal supports (15) are arranged between the long cofferdams (4) on both sides, and water is pumped out from the cofferdams; S5: excavating the silt at the bottom of the riverbed to below the bottom of the existing river-crossing tunnel, and making the upper end of the low-position bored pile (1) higher than the silt at the bottom of the riverbed; S6: roughening the top pile heads of the low-position bored piles (1) on both sides of the existing cross-river tunnel, and pouring the bottom seal concrete (17) between the existing cross-river tunnel and the cofferdam to form a bottom seal concrete structure, wherein the upper surface of the bottom seal concrete structure is consistent with the bottom elevation of the existing cross-river tunnel; Step 3, planting reinforcement in the existing bottom plate and constructing a widened bottom plate (20): planting a second horizontal reinforcement (18) at the bottom of the outer wall of the existing cross-river tunnel, the length of the second reinforcement (18) being the width of the widened tunnel, after the second reinforcement (18) is planted, extending the first longitudinal reinforcement (19) pre-buried at the top of the low-position bored pile (1) to the second reinforcement (18) and welding it to the second reinforcement (18), and finally pouring concrete on the bottom cover concrete structure to form the widened bottom plate (20); Step 4: Construction of cast-in-place widened side wall (21): on the side of the widened bottom plate (20) away from the existing cross-river tunnel, the steel bars of the widened side wall (21) are tied and the formwork is erected, and concrete is poured to complete the construction of the cast-in-place widened side wall (21). A second longitudinal reinforcement (22) is reserved at the top of the outer widened side wall (21); Step 5: implant the third longitudinal reinforcement (24) on the top of the middle partition wall (23) of the existing cross-river tunnel, and then close the existing cross-river tunnel on one side to ensure the temporary bidirectional normal traffic of the existing cross-river tunnel on the other side; Step 6: For one side of the closed existing cross-river tunnel, the existing top plate and the existing side wall on one side of the middle partition wall (23) of the existing cross-river tunnel are sequentially dismantled; Step 7, erecting a widened top plate template (28), the widened top plate template (28) is supported by supporting columns, the upper part of one side of the widened top plate template (28) is flush with the elevation of the existing middle partition wall (23), the lower part of the other side of the widened top plate template (28) is consistent with the elevation of the widened side wall (21), and the second longitudinal reinforcement (22) at the top of the widened side wall (21) extends to the top of the widened top plate template (28); Step 8: Carry out road surface construction on the widened bottom plate (20) of the closed section; Step 9, opening the tunnel on the side where the widened top plate template (28) has been set up for traffic, and then closing the existing river-crossing tunnel on the other side; Step 10, repeating steps 6 to 8 to complete the installation of widened top plate templates (28) on both sides of the existing cross-river tunnel, and opening the existing cross-river tunnels on both sides to traffic; Step 11: Complete the construction of the widened top plate (29) with prestress by post-tensioning construction technology; Step 12: removing and widening the top plate template (28); Step 13: backfill the fat trough between the widened side wall (21) and the cofferdam, inject water into the cofferdam, and remove the horizontal support (15), the trough prefabricated plate (7), the long cofferdam (4) and the short cofferdam (3) in sequence to complete the widening construction of the existing cross-river tunnel.

2. The existing cross-river tunnel widening construction method according to claim 1 is characterized in that: In step 1, the horizontal spacing between the outermost rows of low-position bored piles (1) and high-position bored piles (2) on both sides of the existing cross-river tunnel is not less than 3 m, the horizontal spacing between the high-position bored piles (2) and the short cofferdam (3) to be constructed later is not less than 3 m, the pile tops of the high-position bored piles (2) are located at 1 / 2 of the river water depth, and the pile ends of the low-position bored piles (1) and the high-position bored piles (2) are deeply embedded in the bearing layer.

3. The existing cross-river tunnel widening construction method according to claim 1 is characterized in that: In step 2, the width between the cofferdams on both sides of the existing cross-river tunnel is not less than 6 times the width of the single track of the existing cross-river tunnel, and the horizontal distance between the cofferdam and the widened side wall (21) to be constructed later is not less than 6m.

4. The existing cross-river tunnel widening construction method according to claim 1 is characterized in that: In step 2, the trough-shaped prefabricated plate (7) is a steel structure with a "U"-shaped cross section; the trough-shaped prefabricated plate (7) includes a bottom plate and side plates located on both sides of the bottom plate, and a steel cable inclined support (9) is installed between the side plates and the bottom plate. The distance between the reserved sealing grooves (8) at both ends of the side plates of the trough-shaped prefabricated plate (7) is the distance between the long cofferdams (4) on both sides of the existing cross-river tunnel, and the height of the trough-shaped prefabricated plate (7) is the difference between the heights of the long cofferdam (4) and the short cofferdam (3).

5. The existing cross-river tunnel widening construction method according to claim 1 is characterized in that: In step 2, the short mortise and tenon steel sheet piles (5) are spliced ​​together through the mortise and tenon structure; and the long mortise and tenon steel sheet piles (6) are spliced ​​together through the mortise and tenon structure.

6. The existing cross-river tunnel widening construction method according to claim 1 is characterized in that: In step seven, the widened top plate template (28) is supported by three supporting columns, among which the supporting column in the middle is the main column (25) and the supporting columns on both sides are secondary columns (26); an illumination lamp (27) is provided below the widened top plate template (28).

7. The existing cross-river tunnel widening construction method according to claim 1 is characterized in that: In step 12, when removing the widened top plate template (28), according to the principle of one side being open and the other side being closed, the widened top plate template (28) and the supporting columns on both sides of the existing middle partition wall (23) are removed in sequence, and then the tunnels on both sides are restored to traffic.

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