Construction method of city gate opening-shaped tunnel bottom plate and short side wall

Abstract

The invention discloses a construction method for a bottom plate and a short side wall of a city gate opening-shaped tunnel, which adopts suspended formwork construction and can realize integrated pouring of the bottom plate and the short side wall without mounting a bottom plate formwork. The short side wall formwork is mounted in a suspended mode, the first pouring cavity is defined by the bottom of the short side wall formwork and the tunnel preliminary supporting structure, bottom plate concrete can be poured, the bottom plate formwork is not needed at all, construction is easy and convenient, the technical problem that bubbles are not prone to being discharged when existing bottom plate concrete is vibrated is solved, and the construction quality is improved; short side wall concrete is poured before initial setting of bottom plate concrete, integrated pouring of the bottom plate concrete and the short side wall concrete is achieved, and integrity is ensured; the connecting ribs and the fixing ribs are used for carrying out lower supporting and upper lifting on the low side wall formwork, the stability of the formwork is effectively guaranteed, the fixing ribs and the low side wall formwork can be repeatedly used, the turnover material investment is small, the apportionment cost is low, the steel consumption is remarkably reduced, and the construction cost is reduced.

Description

Technical Field

[0001] The invention relates to a tunnel construction technology in the field of hydraulic engineering, in particular to a construction method for a city gate-shaped tunnel bottom plate and a low side wall. Background Art

[0002] The concrete lining of traditional city gate tunnels (especially hydraulic tunnels) is generally poured in three steps, that is, pouring the tunnel bottom slab concrete first, then pouring the low side wall concrete, and finally pouring the remaining wall and vault concrete. Although this construction method is fast, there are too many construction joints and poor integrity. In particular, the construction joints where the bottom slab contacts the low side wall are weak stress positions, which are prone to leakage during operation and difficult to ensure the quality of the project.

[0003] To overcome the above problems, the "Specifications for the Design of Hydraulic Tunnels" (SL279-2016) stipulates that longitudinal construction joints should be set at locations where the tensile stress and shear stress of the lining structure are relatively small. According to the regulations, the longitudinal construction joints of the city gate tunnel are located 30 to 150 cm above the bottom plate, which requires that the bottom plate and the low side wall of the tunnel must be cast as one. There are two main existing one-piece casting construction methods, one is to use a full-section trolley for integral lining, and the other is to use anchor bars and tie bars to fix the bottom formwork and the low side wall formwork. The construction procedures of these two construction methods are relatively complicated, the formwork is complex (especially the trolley for integral lining), the number of tie bars and anchor bars is large, and the construction is time-consuming; there are a large number of exposed tie bars and anchor bar heads on the water-facing surface. If they are not handled properly, it will directly affect the overall quality of the concrete, and there will be waste of tie bars and anchor bars, which will increase the construction cost. Summary of the invention

[0004] In view of this, the present invention proposes a construction method for a city gate-shaped tunnel bottom plate and a low side wall.

[0005] To achieve the above object, the present invention adopts the following technical solutions: The construction method of the city gate tunnel bottom plate and the low side wall of the present invention adopts the suspended formwork construction, and can realize the integral casting of the bottom plate and the low side wall without installing the bottom plate formwork, and includes the following contents: The first step is to cut steel bars of equal length to make connecting bars, and weld connecting bolts at one end of each connecting bar to complete the production of the connecting bars; cut steel bars of equal length, and bend the steel bars to obtain fixed bars having a first horizontal section and a second horizontal section, and the first horizontal section and the second horizontal section are staggered up and down; Install the connecting ribs at the bottom of the short side wall formwork. During installation, cover the connecting bolts of the connecting ribs with a nylon column to protect the connecting bolts. Weld the fixing ribs at intervals on the top of the short side wall formwork. The second step is to weld the fixing bars one by one to the steel arch frame of the tunnel preliminary support structure at the support position of the short side wall formwork, weld the connecting bars one by one to the steel arch frame, and use the connecting bars and fixing bars to connect the short side wall formwork and the steel arch frame so that the short side wall formwork is suspended in the tunnel; The bottom edge of the short side wall formwork and the preliminary tunnel support structure enclose a first casting cavity whose height is consistent with the designed thickness of the tunnel bottom plate, and the supporting surface of the short side wall formwork and the preliminary tunnel support structure enclose a second casting cavity whose thickness is consistent with the designed thickness of the short side wall and whose top elevation is consistent with the designed height of the short side wall. The third step is to pour the bottom slab concrete into the first pouring cavity gradually until the designed height after the installation of the low side wall formwork is completed, and the bottom slab concrete is vibrated during the pouring process; 20 to 40 minutes after the bottom slab concrete is poured and before the initial setting, pour the low side wall concrete in the second pouring cavity in batches and vibrate it. The pouring height each time is ≤30cm. The fourth step is to smooth the bottom slab concrete and the bottom side wall concrete respectively after the pouring of the bottom side wall is completed; when the strength of the bottom side wall reaches the requirements for demolding, cut off the welding points of the fixing bars and the steel arch frame, unscrew the nuts on the connecting bolts, and remove the bottom side wall formwork; finally, remove the connecting bolts that extend beyond the bottom slab concrete to complete the integrated masonry of the bottom slab and the bottom side wall of the city gate-shaped tunnel.

[0006] The beneficial effects are as follows: the present invention suspends the installation of the short side wall formwork, and the bottom of the short side wall formwork and the preliminary support structure of the tunnel form a first pouring cavity, which can be used to pour the bottom plate concrete. The bottom plate formwork is completely unnecessary, and the construction is simple and convenient. The technical problem that bubbles are not easy to be discharged during the vibration of the existing bottom plate concrete is solved, and the construction quality is improved. The short side wall concrete is poured before the bottom plate concrete begins to set, thereby realizing the integrated pouring of the two and ensuring the integrity.

[0007] During construction, the present invention utilizes connecting bars and fixing bars to support and hang up the short side wall formwork, thereby effectively ensuring the stability of the formwork; the fixing bars and the short side wall formwork can be reused, and only the fixing bars are cast in the concrete, which greatly reduces the usage of steel plates, cross braces, and anchor bars, significantly reduces the usage of steel materials, and thus reduces construction costs.

[0008] The connecting bar of the present invention is completely located in the concrete, and the connecting bolts at the ends thereof are protected by nylon columns, thereby completely isolating the connecting bar from the water-facing surface of the tunnel, avoiding exposure of the steel bar heads, and further ensuring the construction quality.

[0009] Preferably, the short side wall formwork adopts a forming formwork, and its length is consistent with the length of the tunnel compartment section; the fixed ribs are arranged at equal intervals, and the connecting ribs are arranged at equal intervals. During actual installation, the longitudinal spacing of the fixed ribs and the connecting ribs is consistent with the vertical rib spacing of the steel arch frame, so that corresponding welding can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a connection diagram (cross section) of the low side wall formwork and the preliminary tunnel support structure of the present invention.

[0011] Figure 2 It is a connection relationship diagram (longitudinal section) between the short side wall formwork and the fixed reinforcement and the connecting reinforcement of the present invention.

[0012] Figure 3 yes Figure 1 Enlarged view of part A in the middle. DETAILED DESCRIPTION

[0013] The technical solution of the present invention is described in more detail below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following embodiments.

[0014] The present invention proposes a construction method for a city gate tunnel bottom plate and a low side wall, which adopts a suspended formwork construction. In actual construction, the bottom plate and the low side wall can be cast in one piece without the need for a bottom plate formwork, thereby simplifying the construction steps, significantly reducing the amount of steel used, and reducing the construction cost. The method specifically comprises the following steps: The first step is to cut steel bars of equal length to make connecting bars 1. The connecting bars 1 are straight bars, one end of which is used to be welded to the steel arch frame of the preliminary supporting structure of the tunnel, and the other end is welded with a connecting bolt perpendicular to the steel arch frame; Cut steel bars of equal length and bend them to make fixed bars 6. The fixed bars 6 have a first horizontal section, a second horizontal section and a vertical section. The first horizontal section and the second horizontal section are connected by the vertical section. Figure 1-2 ; Install the connecting reinforcement 1 at the bottom of the short side wall formwork 5. During installation, a nylon column 3 is installed on each connecting bolt. The connecting bolt passes through the short side wall formwork 5 upward and screws the nut 4 (see Figure 3 ), and then fixed together, repeating this process to fix multiple connecting bars 1 at equal intervals on the short side wall formwork 5; The welding connecting ribs 1 are welded at equal intervals on the top of the short side wall formwork 5. During welding, the first horizontal section of the fixing ribs 6 is welded to the top of the short side wall formwork 5, so that the height of the second horizontal section is higher than the top of the short side wall formwork 5. In the pouring construction described later, the fixing ribs 6 are located above the short side wall concrete, which is convenient for demoulding; During installation, the low side wall formwork 5 uses a fixed formwork, the length of which is consistent with the tunnel construction section, and the height of which is consistent with the design height of the low side wall; during actual construction, the low side walls on both sides are cast at the same time, so during production, it is necessary to respectively connect the fixing ribs 6 and the connecting ribs 1 to each low side wall formwork 5; In the second step, after the construction of the preliminary support structure of the tunnel is completed, the short side wall formwork 5 is symmetrically installed in the tunnel, and the fixed installation of any short side wall formwork 5 is taken as an example: the short side wall formwork 5 is supported at the designed position, and then the connecting ribs 1 are welded to the steel arch frame one by one, and the second horizontal sections of the fixing ribs 6 are welded to the steel arch frame one by one, and the short side wall formwork 5 and the steel arch frame are fixedly connected together through the connecting ribs 1 and the fixing ribs 6, so that the short side wall formwork 5 is suspended and arranged; repeat the above operation to suspend another short side wall formwork 5 on the steel arch frame; Among them, the bottom edge of the short side wall formwork 5 and the preliminary support structure of the tunnel enclose a first casting cavity I whose height is consistent with the designed thickness of the tunnel bottom plate, and the short side wall formwork 5 and the support surface III of the preliminary support structure of the tunnel enclose a second casting cavity II, the thickness of the second casting cavity II is consistent with the designed thickness of the short side wall, and its top elevation is consistent with the designed height of the short side wall; during construction, only the short side wall formwork 5 needs to be suspended and installed, and there is no need to install the bottom plate formwork, the construction is simple and fast, and there is no need to support the short side wall formwork 5, which significantly reduces the number of anchor bars, thereby reducing the amount of steel used; The third step is to lay the bottom slab concrete in the first pouring cavity I until the designed height after the installation of the short side wall formwork 5 is completed. During the pouring process, the bottom slab concrete is vibrated, and the bubbles generated by the vibration can be discharged smoothly to avoid the occurrence of honeycombs and pockmarks on the bottom slab concrete. 20 to 40 minutes after the bottom slab concrete is poured and before the initial setting, the low side wall concrete is poured and vibrated in batches into the second pouring cavity II, with each pouring height ≤30cm; when the bottom slab concrete does not bulge, adjust the height of the warehouse; if the bottom slab concrete has partial initial setting when pouring the low side wall concrete, spread cement mortar at the initial setting position, and then pour again to ensure the integrity of the low side wall concrete and the bottom slab concrete; Step 4: After the low side wall is poured, the bottom slab concrete and the low side wall concrete are smoothed respectively; the bottom slab concrete is smoothed by a smoothing machine, and the low side wall concrete is smoothed manually; Step 5: When the strength of the short side wall reaches the requirement for demoulding, cut off the welding points of the fixing ribs 6 and the steel arch frame, unscrew the nuts 4 on the connecting bolts 2, and then the short side wall formwork 5 can be removed; Among them, after removal, the fixed reinforcement 6 and the short side wall formwork 5 can be recycled again, which greatly reduces the amount of steel plates, cross braces, and anchor bars, and significantly reduces the cost of steel materials; After the low side wall formwork 5 is removed, the upper part of the connecting bolt 2 (with the nylon column 3) is located above the bottom plate, and the redundant part is cut off, completing the integrated masonry of the bottom plate and the low side wall of the city gate tunnel.

[0015] In the present invention, the connecting bar 1 is completely located in the concrete, and the connecting bolt 2 is protected by a nylon column 3, thereby completely isolating the connecting bar 1 from the water-facing surface of the tunnel, avoiding exposure of the steel bar head, and further ensuring the construction quality.

[0016] Taking a large irrigation project with a total length of 200km and a total length of about 36km of hydraulic tunnels as an example, the length of a single hydraulic tunnel in the project is 80m to 4700m, the size of the water-passing section is 1.5m×2m to 3m×3.5m, the initial support thickness is 10 to 15cm, and the secondary lining concrete thickness is 20 to 40cm. If the hydraulic tunnel in the project is constructed using a full-section trolley, the cross-sections of the hydraulic tunnels are of different sizes and lengths, so multiple full-section trolleys are required, which results in a high one-time investment. Compared with the full-section trolley construction scheme, the technical scheme of the present invention can significantly reduce the consumption of tie bars and anchor bars, which is only 10% of that of the full-section trolley. During construction, only the low side wall formwork 5 needs to be supported, and the low side wall formwork 5 and the fixed bars 6 can be circulated, the cost of circulating materials is low, and the labor input for formwork installation and disassembly can be reduced by more than 60%. The formwork of the present invention is easy to install and disassemble, and has a small size, and is particularly suitable for the construction of small-section hydraulic tunnels with a cross-sectional width of less than 3m.

[0017] Finally, it is emphasized that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions recorded in the aforementioned embodiments without creative work, or replace some of the technical features therein with equivalents. Therefore, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A construction method for a city gate-shaped tunnel floor and low side walls, characterized in that: The one-piece lining construction method adopts suspended formwork construction, including the following contents: The first step is to cut steel bars of equal length to make connecting bars, and weld connecting bolts at one end of each connecting bar to complete the production of the connecting bars; cut steel bars of equal length, and bend the steel bars to obtain fixed bars having a first horizontal section and a second horizontal section, and the first horizontal section and the second horizontal section are staggered up and down; Install the connecting ribs at the bottom of the short side wall formwork. During installation, cover the connecting bolts of the connecting ribs with a nylon column to protect the connecting bolts. Weld the fixing ribs at intervals on the top of the short side wall formwork. The second step is to weld the fixing bars one by one to the steel arch frame of the tunnel preliminary support structure at the support position of the short side wall formwork, weld the connecting bars one by one to the steel arch frame, and use the connecting bars and fixing bars to connect the short side wall formwork and the steel arch frame so that the short side wall formwork is suspended in the tunnel; The bottom edge of the short side wall formwork and the preliminary tunnel support structure enclose a first casting cavity whose height is consistent with the designed thickness of the tunnel bottom plate, and the supporting surface of the short side wall formwork and the preliminary tunnel support structure enclose a second casting cavity whose thickness is consistent with the designed thickness of the short side wall and whose top elevation is consistent with the designed height of the short side wall. The third step is to pour the bottom slab concrete into the first pouring cavity gradually until the designed height after the installation of the low side wall formwork is completed, and the bottom slab concrete is vibrated during the pouring process; 20 to 40 minutes after the bottom slab concrete is poured and before the initial setting, pour the low side wall concrete in the second pouring cavity in batches and vibrate it. The pouring height each time is ≤30cm. The fourth step is to smooth the bottom slab concrete and the bottom side wall concrete respectively after the pouring of the bottom side wall is completed; when the strength of the bottom side wall reaches the requirements for demolding, cut off the welding points of the fixing bars and the steel arch frame, unscrew the nuts on the connecting bolts, and remove the bottom side wall formwork; finally, remove the connecting bolts that extend beyond the bottom slab concrete to complete the integrated masonry of the bottom slab and the bottom side wall of the city gate-shaped tunnel.

2. The construction method of the city gate tunnel bottom plate and low side wall according to claim 1 is characterized in that: The short side wall formwork adopts a formed formwork, and its length is consistent with the length of the tunnel chamber section; the fixed reinforcements are arranged at equal intervals, and the connecting reinforcements are arranged at equal intervals.

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