An integral concrete pouring support system and construction method for a tunnel

Abstract

The present invention discloses an integral casting support system for tunnel concrete and a construction method. The support system is constructed by prefabricated and shaped top arch shaped steel arch frames, bottom arch shaped steel arch frames, side wall shaped steel arch frames and middle supports for supporting each shaped steel arch frame, and concrete casting forms are fixed on the outer sides of each shaped steel arch frame; the construction method includes: fabricating the shaped steel arch frames, constructing the bottom arch anchor bars and tie bars; placing the circumferential concrete steel bars of the side and top arches in the bottom arch without installation for the time being; pasting permeable formwork cloth, installing the bottom arch formwork, installing the bottom arch shaped steel arch frame, erecting the middle supports, installing the side wall steel arch frame and the top arch shaped steel arch frame, etc., and casting the concrete in grades and batches. The present invention uses shaped steel arch frames to replace traditional supports, improves the forming quality of subsequent formwork installation, and improves the stress conditions of the support system; the lengths of the middle supports are unified and can be recycled multiple times, avoiding material waste; double-layer plywood formwork is used, which not only ensures the stiffness but also meets the requirements for the surface radian of the tunnel.

Description

Technical Field

[0001] The present invention belongs to the concrete construction technology of hydraulic engineering, highway or railway tunnels, and belongs to the concrete pouring construction technology of underground engineering. In particular, it relates to a support system for integral pouring of tunnel concrete and its construction method. Background Art

[0002] Generally, the concrete lining of tunnels adopts the steel formwork trolley method or the full hall scaffolding method. Among them, the steel formwork trolley method has been vigorously promoted and used due to its high construction efficiency and high quality assurance rate. However, for parts with short concrete lining length and many structural changes, only the full hall scaffolding method can be used for construction.

[0003] The full hall scaffolding method, also known as the support method, is usually divided into the construction of the bottom arch part and the side and top arch parts. Usually, the bottom arch is poured first, and after the bottom arch is poured, a steel pipe scaffold is erected to construct the side and top arches. This construction method inevitably produces longitudinal construction joints in the lining, posing a risk of water seepage and leakage, and cannot meet the requirements for chambers with high integrity requirements. In addition, the construction scaffold is continuously adjusted and cut according to the tunnel cross-section requirements, resulting in a large amount of cost waste. In addition, the formwork for the inverted arch part and the side and top arches generally uses combined steel formwork or steel formwork. After slight deformation of the formwork, phenomena such as loose joints and offset will occur, affecting the quality of the concrete entity and appearance. Summary of the Invention

[0004] The present invention discloses a support system for integral pouring of tunnel concrete and its construction method. The purpose of the present invention is to provide a support system and construction method that can not only meet the integral pouring of the tunnel at one time, but also effectively improve the entity quality and appearance quality, and solve the quality problems of the lining construction by the support method.

[0005] The present invention is realized through the following technical solutions:

[0006] A support system for integral pouring of tunnel concrete. The tunnel includes a top arch, two side walls and a bottom arch extending along the axial direction of the tunnel. The support system is characterized in that it is built by prefabricated and shaped top arch shaped steel arches, bottom arch shaped steel arches, side wall shaped steel arches and middle supports for supporting each shaped steel arch. Concrete pouring formwork is fixed on the outside of each shaped steel arch;

[0007] Each shaped steel arch is a shaped support steel truss beam prefabricated by steel beams. Each shaped steel arch extends along the circumferential wall of the tunnel axis. The outer surface formed by each shaped steel arch and the fixed concrete pouring formwork outside has the same surface shape as the inner contour of the concrete lining of the corresponding tunnel;

[0008] The middle support is arranged in the middle of the tunnel and extends along the axial direction of the tunnel for support and connection and fixation with each shaped steel arch around.

[0009] The concrete pouring formwork described in the present invention is a double - plywood structure formed by closely installing two layers of plywood. The double - plywood is formed by closely installing single - layer plywood. The single - layer plywood is easy to bend and form, and the stiffness of the double - layer meets the use requirements.

[0010] Inside each fixed - type steel arch frame, it is connected and supported by small vertical rods and inclined rods. The spacing between the small vertical rods in the middle of the top - arch fixed - type steel arch frame and the bottom - arch fixed - type steel arch frame is the same as the spacing of the vertical rods of the middle support. The spacing between the small vertical rods in the middle of the side - wall steel arch frame is the same as the spacing of the cross - bars of the middle support. The maximum height of each fixed - type steel arch frame is 1.4 - 1.5 m.

[0011] The present invention is provided with bottom - arch anchor bars at the bottom arch of the tunnel, and tie - rods are set at the top arch and side walls of the tunnel; the bottom - arch anchor bars extend into the rock not less than 1.0 m, with 30 - 50 cm exposed. The outer end of the bottom - arch anchor bar is connected and fixed to the bottom - arch fixed - type steel arch frame, and the connection part is fixed by tie - rods and fasteners; the outer end of the tie - rod is welded and fixed to the system anchor bar in the bedrock of the tunnel, and the inner end is welded and fixed to the tie - rod for connecting and supporting the formwork.

[0012] The surface of the concrete pouring formwork is covered and pasted with a permeable formwork cloth. The middle support is a support structure formed by the horizontal and vertical combination of steel members.

[0013] The present invention also discloses a construction method for the construction support system of the above - mentioned integral concrete pouring of the tunnel, including the following technological steps:

[0014] The first step: respectively manufacture fixed - type steel arch frames, including the manufacture of top - arch fixed - type steel arch frames, bottom - arch fixed - type steel arch frames and side - wall fixed - type steel arch frames;

[0015] The second step: construct bottom - arch anchor bars, construct tie - rods for side walls and top arches; after installing the bottom - arch anchor bars, place the circumferential concrete steel bars of the side and top arches in the bottom arch and do not install them temporarily;

[0016] The third step: paste permeable formwork cloth on the surface of each formwork, install the bottom - arch formwork, and install the waling;

[0017] The fourth step: successively install the bottom - arch fixed - type steel arch frame, set up the middle support, install the side - wall steel arch frame and the top - arch fixed - type steel arch frame. Among them, the outer end of the bottom - arch anchor bar is connected and fixed to the bottom - arch fixed - type steel arch frame, and the outer end of each tie - rod is welded and fixed to the system anchor bar;

[0018] The fifth step: successively install the square timbers and waling on the outside of the top - arch fixed - type steel arch frame and the side - wall fixed - type steel arch frame, then install the side - top arch formwork, and install the circumferential and longitudinal concrete steel bars of the top arch; install tie - rods and weld them to the inner end of the tie - rods;

[0019] The sixth step: install the plug formwork and pour the concrete.

[0020] In the above-mentioned second construction step, the bottom arch anchor bars are made of anchor bars with a diameter of 26 - 32 mm. The bottom arch anchor bars extend into the rock by no less than 1.0 m and are exposed by 30 - 50 cm. The layout of the spacing between rows is the same as that of the load-bearing scaffolding of the middle support; the tie bars for the side walls and the top arch are made of anchor bars with a diameter of 22 - 25 mm, and the spacing between rows is 1.0 - 1.5 m.

[0021] In the above-mentioned sixth step, first pour the first-class aggregate self-compacting concrete for the bottom arch part, then pour the second-class aggregate ordinary concrete for the side walls, and finally pour the first-class aggregate self-compacting concrete for the top arch part.

[0022] The support system and construction method of the present invention use standardized steel arch frames to replace traditional supports, improving the forming quality of subsequent formwork installation and the stress conditions of the support system. The lengths of the supports erected in the middle later are unified and can be recycled multiple times, avoiding material waste. The method of using double-layer plywood not only ensures the stiffness but also meets the requirements for the arc of the tunnel surface.

[0023] The present invention has the following differences and advantages compared with the existing concrete support system and construction method:

[0024] 1. Different support systems. The method of the present invention uses standardized steel arch frames to improve the stress conditions and increase the integrity of the formwork; making full use of tie rods, struts, and tie bars, with downward support and outward pull, effectively solves various problems such as concrete floating and lateral pressure.

[0025] 2. Different formwork systems. The present invention uses double-layer plywood as the formwork, which can well achieve the requirements of arc forming or various forming arcs while ensuring its stiffness function, and at the same time avoids quality defects such as misalignment and joint treatment faced by conventional combined steel formwork.

[0026] 3. Different concrete formulations. The present invention adjusts the concrete within the 120° range of the bottom arch to first-class aggregate self-compacting concrete, improving the entity quality. At the same time, a permeable formwork cloth is set to improve the exhaust effect and eliminate quality defects such as air bubbles and pockmarks.

[0027] 4. Different steel bar installation procedures and methods. First, install the circumferential and longitudinal steel bars of the bottom arch, and place the circumferential steel bars of the side and top arches in the bottom arch in advance to avoid the problem that the circumferential steel bars cannot be smoothly transported to the construction working surface due to size issues later. Description of the Drawings

[0028] Figure 1 It is the general drawing of the standardized steel arch frame, formwork, and support system of the present invention.

[0029] Figure 2 It is the structural design drawing of the standardized steel arch frame of the present invention.

[0030] Figure 3 It is the schematic diagram of the concrete structure of the present invention.

[0031] Figure 4 It is a schematic diagram for template magnification of the present invention.

[0032] In the figure, A is the outer contour line of the concrete lining, i.e., the excavation contour line, B is the inner contour line of the concrete lining, C is the shaped steel arch frame, D is the middle support, E is the bottom arch anchor bar, F is the concrete steel bar, C1 is the top arch shaped steel arch frame, C2 is the bottom arch shaped steel arch frame, C3 is the side wall shaped steel arch frame, 1 is the side frame of the steel arch frame, 2 is the small vertical rod, 3 is the first-class aggregate self-compacting concrete, 4 is the second-class aggregate ordinary concrete, 5 is the formwork, 6 is the waling, 7 is the tie bar, 8 is the pull rod, and 9 is the diagonal rod. Specific embodiments

[0033] The present invention will be further described below in conjunction with specific embodiments. The specific embodiments are further explanations of the principle of the present invention and do not limit the present invention in any way. The technologies identical or similar to the present invention do not exceed the protection scope of the present invention.

[0034] As shown in the figure, before the construction of the concrete lining of the tunnel of the present invention, the cleaning of the tunnel is first completed, including the cleaning of the rock surface, the cutting of the anchor bolt heads of the side and top arches of the chamber, and the removal of garbage.

[0035] The production of each shaped steel arch frame C is carried out in the processing factory. The shaped steel arch frame C can be made of Φ48×3.5mm steel pipes. The side frame 1 of the shaped steel arch frame includes an arc side close to the lining surface on the outside and a straight side on the inside. Inside the shaped steel arch frame 1, a steel truss beam structure is formed by the vertical or horizontal steel arch frame small vertical rods 2 and the steel arch frame diagonal rods 9 that obliquely connect the steel arch frame small vertical rods 2 or the side frame 1 of the steel arch frame; the shaped steel arch frame C includes the top arch shaped steel arch frame C1, the bottom arch shaped steel arch frame C2, and the side wall shaped steel arch frame C3. The radius of the arc side is the inner diameter of the concrete lining - formwork thickness - waling thickness - square timber thickness. In this example, it is the inner diameter of the concrete lining - formwork thickness 18mm - waling thickness 48mm - square timber thickness 50mm. The spacing between the steel arch frame small vertical rods 2 is the same as the spacing of the load-bearing scaffold of the middle support D, generally 60 - 80cm. The two steel arch frame small vertical rods 2 are connected by a diagonal rod 9, and the single-piece length is 1.5m; in the top arch shaped steel arch frame C1 and the bottom arch shaped steel arch frame C2, the small vertical rods 2 are arranged vertically; in the side wall shaped steel arch frame C3, the small vertical rods 2 are arranged horizontally; after completion, trial assembly is carried out.

[0036] The bottom arch anchor bar E is constructed. Anchor bars with a diameter of 26 - 32mm are used. The bottom arch anchor bar E extends into the rock not less than 1.0m and is exposed 30 - 50cm. The layout spacing is the same as the spacing of the load-bearing scaffold of the middle support D; after the construction of the bottom arch anchor bar E is completed, the tie bars 7 of the side wall and the top arch are constructed. Anchor bars with a diameter of 22 - 25mm are used and are connected to the support anchor bolts later, with a spacing of 1.0 - 1.5m.

[0037] After the construction of the bottom arch anchor bars E and the tie bars 7, install the longitudinal and circumferential concrete reinforcement bars for the bottom arch, and place all the circumferential concrete reinforcement bars for the side and top arches in the bottom arch according to the designed quantity, but do not install them temporarily. Since the bottom arch anchor bars E have been constructed at the bottom, it is necessary to place the designed quantity of circumferential concrete reinforcement bars between every two rows of the bottom arch anchor bars E in strict accordance with the spacing requirements. The longitudinal and circumferential concrete reinforcement bars are the consolidation reinforcement bars in the concrete lining.

[0038] Before installing each formwork 5, attach a permeable formwork cloth to the outer surface of the formwork 5.

[0039] Install the bottom arch formwork 5. Each formwork 5 uses two layers of 9-mm-thick plywood. As Figure 4 shown, install the waling 6 and the square timbers for the bottom arch part. The waling 6 uses 2 steel pipes with a diameter of Φ48×3.5 mm, the size of the square timbers is 5×10 cm, and use the tie rods 8 for fixation. The diameter of the tie rods 8 is 14 mm to 20 mm.

[0040] Install the bottom arch fixed steel arch frame C2, set up the middle support D, install the side wall fixed steel arch frame C3 and the top arch fixed steel arch frame C1 in sequence; then install the square timbers and the waling 6 outside the side wall fixed steel arch frame C3 and the top arch fixed steel arch frame C1; then install the side and top arch formworks 5; install the circumferential and longitudinal concrete reinforcement bars for the top arch; conduct systematic reinforcement on the middle support 4 and the formwork 5, and install the closure formwork; the middle support 4 is a support structure composed of a combination of steel members in the vertical and horizontal directions, such as a support scaffold structure composed of connecting members such as steel pipes.

[0041] As Figure 3 shown, adjust the concrete gradation in the 90° range of the top arch and the 120° range of the bottom arch to the first-class self-compacting concrete 3, and conduct concrete pouring in the way of uniform feeding on both sides.

[0042] As shown in the figure, the construction process method of the integral concrete pouring support system for the tunnel of the present invention will be further described below in conjunction with the accompanying drawings:

[0043] The first step: fabricate the fixed steel arch frame C. The spacing L1 between the middle small vertical rods 2 of the bottom arch fixed steel arch frame C2 and the top arch fixed steel arch frame C1 is the same as the spacing between the vertical rods of the middle support D, and the spacing L2 between the middle small vertical rods 2 of the side wall fixed steel arch frame C3 is the same as the spacing between the cross bars of the middle support D. The maximum height L3 of the steel arch frame is 1.4 to 1.5 m;

[0044] The second step: construct the bottom arch anchor bars E, and construct the tie bars 7 for the side wall and the top arch; after installing the bottom arch anchor bars E, place the circumferential concrete reinforcement bars for the side and top arches in the bottom arch and do not install them temporarily;

[0045] The third step: paste a permeable formwork cloth on the surface of each formwork 5, install the bottom arch formwork 5, and install the waling 6;

[0046] Step 4: Install the bottom arch fixed steel arch frame C2, set up the middle support D, install the side wall steel arch frame C3 and the top arch fixed steel arch frame C1 in sequence. Among them, the outer end of the bottom arch anchor bar is connected to the bottom arch fixed steel arch frame, and the connection part is fixed by tie rods and fasteners. The outer end of each tie bar 7 is welded and fixed to the system anchor bolt;

[0047] Step 5: Install the square timbers and the collar 6 outside the top arch fixed steel arch frame C1 and the side wall fixed steel arch frame C3 in sequence, then install the side and top arch formwork 5, and install the circumferential and longitudinal concrete reinforcement of the top arch; install the tie rod 8 and weld it to the inner end of the tie bar 7;

[0048] Step 6: Install the closure formwork and pour the concrete; first pour the self-compacting concrete 3 of the bottom arch part, then pour the side wall concrete 4, and finally pour the self-compacting concrete 3 of the top arch part.

[0049] The following takes the construction of a certain underground water diversion tunnel project as an example to illustrate the application of the method of the present invention.

[0050] The length of the upper bend section of the water diversion lower vertical shaft is 45.925 m, the length of the lower bend section is 45.625 m, the radius of both is 30 m, the straight section is 287.267 m, and the total length of the straight section and the bend section of the vertical shaft is 378.817 m. The excavation diameter of the lower vertical shaft and the bend section is 8.9 m, the initial support thickness is 10 cm, the lining thickness is 60 cm, and the diameter after lining is 7.5 m. The upper bend section is 44.13 m away from the No. 2 construction adit and 67.791 m away from the water diversion upper vertical shaft. The lower vertical shaft connects the middle horizontal tunnel and the water diversion lower horizontal tunnel. The concrete grade is C30W10F100 second-grade aggregate, all the steel bars adopt HRB400, the construction joints and structural joints are provided with copper water stops, and the steel bars pass through the joints. The present invention is successfully applied to the concrete construction of the bend section of the water diversion lower vertical shaft, the lining shape quality is excellent, the problems of air bubbles and water patterns in the inverted arch part are effectively solved, and the excellent rate of the concrete reaches 94.2%.

Claims

1. A construction method for integral pouring of tunnel concrete, characterized in that: The tunnel includes a crown arch, two side walls and an invert arch extending along the axial direction of the tunnel. The support system used for the integral concrete placement construction of the tunnel is composed of prefabricated and shaped crown arch steel arch frames, invert arch steel arch frames, side wall steel arch frames and middle supports for supporting each shaped steel arch frame. Concrete placement forms are fixed on the outer sides of each shaped steel arch frame. Each shaped steel arch frame is a shaped support steel truss beam prefabricated from steel beams. Each shaped steel arch frame extends and is arranged along the circumferential wall of the tunnel's axial direction. The outer surface formed by each shaped steel arch frame and the externally fixed concrete placement form has the same surface shape as the inner contour of the cast-in-place concrete lining of the corresponding tunnel. The middle supports are arranged along the axial direction of the tunnel in the middle of the tunnel for extending support and are fixedly connected and supported with each shaped steel arch frame around. The construction method includes the following steps: The first step: separately fabricate the shaped steel arch frames, including fabricating the crown arch shaped steel arch frame, the invert arch shaped steel arch frame and the side wall shaped steel arch frame. The second step: construct the invert arch anchor bars, and construct the tie bars for the side walls and the crown arch; after installing the invert arch anchor bars, place the circumferential concrete reinforcement bars for the side walls and the crown arch in the invert arch but do not install them temporarily. The third step: paste permeable formwork cloth on the surfaces of each form, install the invert arch form, and install the waling. The fourth step: successively install the invert arch shaped steel arch frame, erect the middle supports, install the side wall steel arch frame and the crown arch shaped steel arch frame. Among them, the outer ends of the invert arch anchor bars are connected and fixed to the invert arch shaped steel arch frame, and the outer ends of each tie bar are welded and fixed to the systematic anchor bolts. The fifth step: successively install the wooden square timbers and the waling on the outer sides of the crown arch shaped steel arch frame and the side wall shaped steel arch frame, then install the side wall and crown arch forms, and install the circumferential and longitudinal concrete reinforcement bars for the crown arch; install the tie rods and weld them to the inner ends of the tie bars. The sixth step: install the closure form and pour the concrete.

2. The construction method for integral pouring of tunnel concrete according to claim 1, wherein: The concrete placement form is a double-layer plywood structure composed of two layers of plywood closely installed.

3. The construction method for integral pouring of tunnel concrete according to claim 2, wherein: Inside each shaped steel arch frame, it is connected and supported by small vertical rods and diagonal rods. The spacing between the middle small vertical rods of the crown arch shaped steel arch frame and the invert arch shaped steel arch frame is the same as the spacing of the vertical rods of the middle supports. The spacing between the middle small vertical rods of the side wall steel arch frame is the same as the spacing of the cross bars of the middle supports. The maximum height of each shaped steel arch frame is 1.4 - 1.5 m.

4. The construction method for integral concrete pouring in a tunnel according to claim 2, characterized in that: The invert arch of the tunnel is provided with invert arch anchor bars, and the crown arch and side walls of the tunnel are provided with tie bars; the invert arch anchor bars extend into the rock not less than 1.0 m, are exposed 30 - 50 cm, and the outer ends of the invert arch anchor bars are connected and fixed to the invert arch shaped steel arch frame; the outer ends of the tie bars are welded and fixed to the systematic anchor bolts in the bedrock of the tunnel, and the inner ends are welded and fixed to the tie rods for connecting and supporting the formwork.

5. The construction method for integral pouring of tunnel concrete according to claim 2, wherein: The surface of the concrete placement form is covered and pasted with permeable formwork cloth.

6. The construction method for integral concrete pouring in a tunnel according to claim 2, wherein: The middle support is a support structure composed of a combination of horizontal and vertical steel members connected.

7. The construction method for integral concrete pouring in a tunnel according to any one of claims 1 to 6, characterized in that: In the second step, when constructing the invert arch anchor bars, anchor bars with a diameter of 26 - 32 mm are used. The invert arch anchor bars extend into the rock not less than 1.0 m, are exposed 30 - 50 cm, and the spacing of the layout is the same as the spacing of the load-bearing scaffolding of the middle supports; when constructing the tie bars for the side walls and the crown arch, anchor bars with a diameter of 22 - 25 mm are used, and the spacing is 1.0 - 1.5 m.

8. The construction method for integral concrete pouring in a tunnel according to claim 7, characterized in that: The sixth step is to first pour the first-class graded self-compacting concrete for the bottom arch part, then pour the second-class graded ordinary concrete for the side walls, and finally pour the first-class graded self-compacting concrete for the top arch part.

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