Construction method of city gate hole-shaped tunnel floor and low side wall

Abstract

The application discloses a construction method of a city gate hole-shaped tunnel bottom plate and low side wall, which adopts suspended formwork construction and can realize integrated pouring of the bottom plate and the low side wall without installing a bottom plate formwork. The low side wall formwork is suspended and installed, the bottom of the low side wall formwork and a preliminary supporting structure of the tunnel enclose a first pouring cavity, and the bottom plate concrete can be poured, so that the bottom plate formwork is completely unnecessary, the construction is simple and convenient, the technical problem that bubbles are not easy to discharge when the bottom plate concrete is vibrated and compacted is solved, and the construction quality is improved; the low side wall concrete is poured before the bottom plate concrete is initially solidified, integrated pouring of the two is realized, and the integrity is ensured; the low side wall formwork is pulled down and lifted up by using the connecting rib and the fixing rib, the stability of the formwork is effectively ensured, the fixing rib and the low side wall formwork can be repeatedly used, the turnover material investment is small, the cost is low, the steel material consumption is obviously reduced, and the construction cost is reduced.

Description

TECHNICAL FIELD

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

[0002] The traditional concrete lining of the city gate-shaped tunnel (especially the hydraulic tunnel) generally adopts three-step pouring, that is, pouring the tunnel bottom plate concrete first, pouring the low side wall concrete second, and pouring the remaining wall and the vault concrete last. Although this construction method is fast, it has too many construction joints and poor integrity, especially the construction joint between the bottom plate and the low side wall is a weak stress position, which is prone to leakage during operation and difficult to ensure the engineering quality.

[0003] To overcome the above problems, the "Hydraulic Tunnel Design Specification" (SL279-2016) provides that the longitudinal construction joint should be arranged at a position where the lining structure has small tensile stress and shear stress. According to the provision, the longitudinal construction joint of the city gate-shaped tunnel is located at a position 30-150 cm above the bottom plate, which requires that the bottom plate and the low side wall of the tunnel must be integrally poured. The existing integral pouring construction method mainly has two kinds, one is to use full-face trolley integral lining, and the other is to use anchor bars and tension bars to fix the bottom formwork and the low side wall formwork. The construction procedures of these two construction methods are relatively complex, the formwork is complex (especially the trolley integral lining), the number of tension bars and anchor bars is large, and the construction is time-consuming; there are a large number of exposed tension bar heads and anchor bar heads on the water-facing surface, which directly affect the overall quality of the concrete if not properly treated, and the tension bars and anchor bars are wasted, increasing the construction cost. SUMMARY

[0004] Therefore, the present application provides a construction method of a city gate-shaped tunnel bottom plate and a low side wall.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] The construction method of the city gate-shaped tunnel bottom plate and the low side wall according to the present application adopts the suspended form construction, which does not need to install the bottom plate formwork to realize the integral pouring of the bottom plate and the low side wall, and includes the following contents:

[0007] Firstly, cut equal-length steel bars to make connecting bars, weld connecting bolts at one end of each connecting bar to complete the production of the connecting bars; cut equal-length steel bars, bend the steel bars to obtain fixed bars with a first horizontal section and a second horizontal section, and the first horizontal section and the second horizontal section are staggered up and down;

[0008] Install the connecting bars at the bottom of the low side wall formwork, and when installing, sleeve a nylon column on the connecting bolt of the connecting bar to protect the connecting bolt; and weld the fixed bars at the top of the low side wall formwork at intervals;

[0009] Second step, at the position of the low side wall formwork support setting, weld the fixing rib on the steel arch of the tunnel preliminary support structure one by one, weld the connecting rib on the steel arch one by one, connect the low side wall formwork and the steel arch by the connecting rib and the fixing rib to make the low side wall formwork suspend in the tunnel;

[0010] The bottom edge of the low side wall formwork and the tunnel preliminary support structure enclose a first pouring cavity with the height consistent with the design thickness of the tunnel bottom plate, and the low side wall formwork and the support surface of the tunnel preliminary support structure enclose a second pouring cavity with the thickness consistent with the design thickness of the low side wall and the top elevation consistent with the design height of the low side wall.

[0011] Third step, after the low side wall formwork is installed, the bottom plate concrete is poured in the first pouring cavity one by one until the design height, and the bottom plate concrete is vibrated during the pouring process.

[0012] After the bottom plate concrete is poured, the low side wall concrete is poured in the second pouring cavity in batches within 20-40 minutes after pouring and before initial setting, and the pouring height is less than or equal to 30 cm each time.

[0013] Fourth step, after the low side wall is poured, the bottom plate concrete and the low side wall concrete are respectively smoothed, the welding points of the fixing rib and the steel arch are cut off, the nuts on the connecting bolts are unscrewed, the low side wall formwork is removed, the connecting bolts exceeding the bottom plate concrete are cut off, and the integrated construction of the bottom plate and the low side wall of the city gate-shaped tunnel is completed.

[0014] The beneficial effects are that the low side wall formwork is suspended and installed, the bottom of the low side wall formwork and the tunnel preliminary support structure enclose a first pouring cavity, the bottom plate concrete can be poured, the bottom plate formwork is completely unnecessary, the construction is simple and convenient, the technical problem that bubbles are not easy to discharge during the vibration of the bottom plate concrete is solved, the construction quality is improved, the low side wall concrete is poured before the initial setting of the bottom plate concrete, the integrated pouring of the two is realized, and the integrity is ensured.

[0015] The low side wall formwork is supported downward and lifted upward by the connecting rib and the fixing rib during construction, the stability of the formwork is effectively ensured, the fixing rib and the low side wall formwork can be reused, only the fixing rib is poured in the concrete, the amount of steel plate, cross brace and anchor rib is greatly reduced, the amount of steel material is significantly reduced, and the construction cost is further reduced.

[0016] The connecting rib is completely located in the concrete, the connecting bolt at the end of the connecting rib is protected by a nylon column, the connecting rib and the water-facing surface of the tunnel are completely isolated, the steel head is avoided from being exposed, and the construction quality is further ensured.

[0017] Preferably, the low parapet formwork adopts a forming formwork, the length of which is consistent with the length of the tunnel bin section; the fixing ribs are arranged at equal intervals, and the connecting ribs are arranged at equal intervals. In actual installation, the longitudinal interval of the fixing ribs and the connecting ribs is consistent with the vertical rib interval of the steel arch, and then corresponding welding can be realized. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is the connection diagram (cross section) of the low parapet formwork and the tunnel preliminary support structure of the present application.

[0019] Figure 2 is the connection relationship diagram (longitudinal section) between the low parapet formwork and the fixing rib and the connecting rib of the present application.

[0020] Figure 3 is Figure 1 the enlarged view of part A in FIG. 1. DETAILED DESCRIPTION

[0021] The technical solutions of the present application will be described in more detail below with reference to the drawings, but the protection scope of the present application is not limited to the following embodiments.

[0022] The present application proposes a construction method for a city gate-shaped tunnel floor and low parapet, which adopts a suspended formwork construction. In actual construction, the floor and the low parapet can be integrally poured without the floor formwork, thereby simplifying the construction steps, significantly reducing the amount of steel, and reducing the construction cost. The specific steps include the following steps:

[0023] First, an equal-length steel bar is cut to make a connecting rib 1. The connecting rib 1 is a straight rib, one end of which is used for welding with the steel arch of the tunnel preliminary support structure, and the other end is welded with a connecting bolt perpendicular thereto;

[0024] An equal-length steel bar is cut and bent to make a fixing rib 6. The fixing rib 6 has a first horizontal section, a second horizontal section, and a vertical section. The first horizontal section and the second horizontal section are connected through the vertical section, as shown in Figures 1-2 ;

[0025] The connecting rib 1 is installed at the bottom of the low parapet formwork 5. When installing, a nylon column 3 is sleeved on each connecting bolt. The connecting bolt passes out of the low parapet formwork 5 upwards and is screwed with a nut 4 (see Figure 3 ), and then is fixed together. A plurality of connecting ribs 1 are repeatedly fixed and connected at equal intervals on the low parapet formwork 5.

[0026] The connecting rib 1 is welded at equal intervals at the top of the low parapet formwork 5. When welding, the first horizontal section of the fixing rib 6 is welded at the top of the low parapet formwork 5, so that the height of the second horizontal section is higher than the top of the low parapet formwork 5. In the pouring construction described later, the fixing rib 6 is located above the low parapet concrete, which facilitates demolding.

[0027] In the installation, the dwarf side wall template 5 selects the shaped template, the length is consistent with the tunnel construction bin section, and the height is consistent with the design height of the dwarf side wall; in the actual construction, the two sides of the dwarf side wall are poured at the same time, so the fixed rib 6 and the connecting rib 1 need to be respectively fixed on each dwarf side wall template 5 during the production;

[0028] Secondly, after the preliminary support structure of the tunnel is constructed, the dwarf side wall template 5 is symmetrically installed in the tunnel, and the fixed installation of any one of the dwarf side wall templates 5 is taken as an example: the dwarf side wall template 5 is supported at the designed position, then the connecting rib 1 is welded on the steel arch one by one, the second horizontal section of the fixed rib 6 is welded on the steel arch one by one, the dwarf side wall template 5 and the steel arch are fixed together through the connecting rib 1 and the fixed rib 6, and the dwarf side wall template 5 is suspended and arranged; the above operation is repeated, and the other dwarf side wall template 5 is suspended and installed on the steel arch;

[0029] Among them, the bottom edge of the dwarf side wall template 5 and the preliminary support structure of the tunnel form a first pouring cavity I with a height consistent with the design thickness of the tunnel bottom plate, and the dwarf side wall template 5 and the support surface III of the preliminary support structure of the tunnel form a second pouring cavity II, the thickness of the second pouring cavity II is consistent with the design thickness of the dwarf side wall, and the top elevation is consistent with the design height of the dwarf side wall; during construction, only the dwarf side wall template 5 needs to be suspended and installed, without the need to install the bottom plate template, the construction is simple and fast, and without the need to support the dwarf side wall template 5, the number of anchor ribs is significantly reduced, and the amount of steel is further reduced;

[0030] Thirdly, after the installation of the dwarf side wall template 5 is completed, the bottom plate concrete is sequentially laid and poured into the first pouring cavity I until the designed height, and the bottom plate concrete is vibrated during pouring, so that the bubbles generated by vibration can be smoothly discharged, avoiding the appearance of honeycomb, pitted surface and other conditions of the bottom plate concrete;

[0031] After the bottom plate concrete is poured, 20-40min and before initial setting, the dwarf side wall concrete is poured and vibrated into the second pouring cavity II in batches, and the pouring height is ≤30cm each time; the entry height is adjusted when the bottom plate concrete does not bulge; if the bottom plate concrete appears local initial setting when pouring the dwarf side wall concrete, cement mortar is spread at the initial setting position, and then pouring is carried out, to ensure the integrity of the dwarf side wall concrete and the bottom plate concrete;

[0032] Fourthly, after the pouring of the dwarf side wall is completed, the bottom plate concrete and the dwarf side wall concrete are respectively smoothed; among them, the bottom plate concrete is smoothed by a smoothing machine, and the dwarf side wall concrete is smoothed by manual smoothing;

[0033] Fifthly, when the strength of the dwarf side wall reaches the requirement of removing the template, the welding points of the fixed rib 6 and the steel arch are cut off, the nuts 4 on the connecting bolts 2 are unscrewed, and the dwarf side wall template 5 can be removed;

[0034] Wherein, the fixed rib 6 and the low side wall form 5 can be recycled after being removed, the amount of steel plate, cross brace and anchor rib is greatly reduced, and the cost of steel material is significantly reduced;

[0035] After the low side wall form 5 is removed, the upper part of the connecting bolt 2 (with the nylon column 3) is above the bottom plate, the excess part is cut off, and the integrated masonry of the bottom plate and the low side wall of the gate-shaped tunnel is completed.

[0036] In the application, the connecting rib 1 is completely located in the concrete, the connecting bolt 2 is protected by the nylon column 3, and then the connecting rib 1 and the water surface of the tunnel are completely isolated, the steel bar head is avoided from being exposed, and the construction quality is further ensured.

[0037] Taking a large irrigation area project with a total length of 200 km and a total length of hydraulic tunnel of about 36 km as an example, the length of a single hydraulic tunnel in the project is 80 m to 4700 m, the size of the water passing section is 1.5 m x 2 m to 3 m x 3.5 m, the thickness of the primary support is 10 to 15 cm, and the thickness of the secondary lining concrete is 20 to 40 cm. If the hydraulic tunnel in the project is constructed by using the full-face trolley, the size of the section of the hydraulic tunnel is different, the length is different, a plurality of full-face trolleys are required, and the one-time investment is high; compared with the full-face trolley construction scheme, the consumption amount of the reinforcing rib and the anchor rib can be significantly reduced by using the technical scheme of the application, and the consumption amount is only 10% of that of the full-face trolley; only the low side wall form 5 needs to be supported during construction, and the low side wall form 5 and the fixed rib 6 can be recycled, the cost of the recycled materials is low, the labor input for the installation and removal of the form can be reduced by more than 60%, the form is convenient to install and remove, the volume is small, and the application is particularly suitable for the construction of small-section hydraulic tunnels with a section width of less than 3 m.

[0038] Finally, it should be emphasized that the above description is only the preferred embodiments of the application and is not used to limit the application, although the application has been described in detail with reference to the foregoing embodiments, and for those skilled in the art, the technical solutions recorded in the foregoing embodiments can be modified without creative labor, or some technical features can be replaced equivalently. Thus, any modification, equivalent replacement, improvement, etc. within the spirit and principle of the application should be included in the protection scope of the application.

Claims

1. A construction method of a city gate-shaped tunnel floor and low side wall, characterized by: The construction method adopts a suspended form construction, and comprises the following contents. In a first step, equal-length reinforcing steel bars are cut to make connecting bars, which are straight bars, and a connecting bolt perpendicular to each connecting bar is welded at one end of each connecting bar to complete the connecting bar; equal-length reinforcing steel bars are cut and bent to obtain a fixing bar having a first horizontal section and a second horizontal section, which are vertically offset; Connecting bars are installed at equal intervals at the bottom of the low parapet formwork, and a nylon column is sleeved on the connecting bolt of each connecting bar to protect the connecting bolt during installation; fixing bars are welded at equal intervals at the top of the low parapet formwork, and the first horizontal section of each fixing bar is welded at the top of the low parapet formwork so that the height of the second horizontal section is higher than the top of the low parapet formwork; In a second step, the fixing bars are welded one by one on the steel arch of the preliminary support structure of the tunnel at the position where the low parapet formwork is to be arranged, and the connecting bars are welded one by one on the steel arch, and the low parapet formwork and the steel arch are connected by the connecting bars and the fixing bars to make the low parapet formwork suspended in the tunnel; In a third step, after the low parapet formwork is installed, the bottom plate concrete is sequentially and evenly poured into the first pouring cavity until the designed height, and the bottom plate concrete is vibrated during pouring; 20-40 minutes after the bottom plate concrete is poured and before initial setting, the low parapet concrete is sequentially and evenly poured into the second pouring cavity and vibrated, and the pouring height is less than or equal to 30 cm each time; In a fourth step, after the low parapet concrete is poured, the bottom plate concrete and the low parapet concrete are respectively smoothed; when the strength of the low parapet reaches the requirement for form removal, the welding points of the fixing bars and the steel arch are cut, the nuts on the connecting bolts are unscrewed, and the low parapet formwork is removed; finally, the connecting bolts that protrude from the bottom plate concrete are cut off, and the integrated construction of the bottom plate and the low parapet of the city gate-shaped tunnel is completed. The low parapet formwork adopts a shaped formwork, and the length of the shaped formwork is consistent with the length of the tunnel bay.

2. The construction method of the portal-shaped tunnel floor and low sidewall according to claim 1, characterized in that: ​

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