Foamed concrete arc-shaped formwork support structure and method on railway open cut waterproof layer

Abstract

The application discloses a kind of railway open cut tunnel waterproof layer upper foam concrete arc-shaped formwork support structure and method, belong to railway tunnel field, solve the problem that traditional support structure induces tunnel leakage disease, large business line site occupation, formwork forming quality is poor.This application has mortar protection layer on the outer surface of waterproof layer of open cut tunnel lining, and steel framework is arranged in the periphery of mortar protection layer, and the steel framework is laid on the outer surface of mortar protection layer, and the outer side of the steel framework is attached with bamboo plywood formwork, and pouring cavity is formed between bamboo plywood formwork and protection layer;Multiple sets of tensioning components are arranged on the outer surface of bamboo plywood formwork, and multiple sets of tensioning components are arranged along the longitudinal direction of open cut tunnel.This application cancels arch back full hall steel pipe vertical rod, through wall counter-pulling bolt, and all support components are arranged above mortar protection layer, and no hard component directly contacts waterproof layer, so as to completely eliminate the puncture, tearing and leakage diseases of waterproof layer;Steel wire rope is uniformly tensioned along the circumferential joint of bamboo plywood formwork, and the forming quality is significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of railway tunnels, specifically relating to a foamed concrete arc-shaped formwork support structure and method for the waterproof layer of a railway tunnel. Background Technology

[0002] The slopes at the entrances of existing tunnels on mountain railways are susceptible to erosion from heavy rainfall and continuous downpours, making them prone to landslides and debris flows. Collapsed soil can directly encroach on the railway clearance, disrupting train operations and causing significant economic losses. The current remediation plan involves extending the tunnel's open section and backfilling a foamed concrete buffer layer behind the tunnel arch. The lightweight, impact-resistant, and easy-to-fill properties of foamed concrete will help prevent rockfalls and landslides. A waterproof layer will be installed between the tunnel arch and the foamed concrete to prevent groundwater and surface water from eroding the main structure of the tunnel.

[0003] Foamed concrete pouring requires the formation of an outer arc-shaped formwork. Traditional arched formwork uses a full-span steel pipe scaffolding + through-wall tie bolt internal and external bracing construction system, which has been found to have multiple technical defects through long-term engineering practice: 1. Permanent damage and leakage of the waterproof layer: The entire steel pipe upright directly presses on the waterproof layer, and the local stress concentration punctures the waterproof layer; the through-wall tie rod penetrates the waterproof layer structure, forming a permanent leakage channel, and the cost of subsequent tunnel leakage treatment is extremely high.

[0004] 2. High material and labor costs: Traditional curved formwork support requires a large amount of steel pipes, fasteners, and timber backing, with a material cost of 78 to 92 yuan per square meter. The steel pipe transportation, erection, and dismantling processes are numerous, resulting in a large labor input.

[0005] 3. Limited construction space on operating lines: The construction site on both sides of the operating line is small, the dense steel pipe supports occupy the train protection space, and the large steel pipe transfer machinery intrudes into the railway operating line, interfering with normal train operation and posing significant risks to train operation safety.

[0006] 4. Poor formwork forming quality: The steel pipe support points of the arched surface are sparse, and the formwork is prone to bulging and running under the lateral pressure of foamed concrete. The arched surface is not straight, and the amount of work required for subsequent appearance repair is large.

[0007] Currently, the industry lacks a complete set of processes for arched foam concrete formwork support that does not contact or puncture the waterproof layer, which cannot simultaneously solve the four core engineering pain points of waterproof layer protection, cost reduction and efficiency improvement, limited construction sites on operational lines, and poor formwork forming quality. Summary of the Invention

[0008] The purpose of this invention is to provide a foamed concrete arc-shaped formwork support structure for the waterproof layer of railway tunnels, so as to solve the problems of traditional support structures that induce tunnel leakage, high material costs, large site occupation on operating lines, and poor formwork forming quality.

[0009] Another objective of this invention is to provide a method for supporting a foamed concrete arc-shaped formwork on a waterproof layer of a railway tunnel.

[0010] The technical solution of the present invention is: a foamed concrete arc-shaped formwork support structure for the waterproof layer of a railway tunnel, wherein a mortar protective layer is poured on the outside of the waterproof layer of the tunnel lining, a steel reinforcement skeleton is provided on the outside of the mortar protective layer, the steel reinforcement skeleton is laid flat on the outer surface of the mortar protective layer, a bamboo plywood formwork is provided on the outside of the steel reinforcement skeleton, and a casting cavity is formed between the bamboo plywood formwork and the protective layer; multiple sets of tensioning components are provided on the outer surface of the bamboo plywood formwork, and the multiple sets of tensioning components are arranged longitudinally along the tunnel.

[0011] As a further improvement of the present invention, the bamboo plywood template is composed of multiple bamboo plywood panels spliced ​​together.

[0012] As a further improvement of the present invention, the tensioning assembly includes a steel wire rope and a tensioner. One end of the steel wire rope is fixed to the top surface of the longitudinal drainage ditch sidewall of the tunnel, and the other end of the steel wire rope is fixed to the facade of the retaining wall of the mountain outside the tunnel. The steel wire rope is tightened by the tensioner to generate an inward holding force.

[0013] As a further improvement of the present invention, the steel wire rope is arranged on the outer surface of the circumferential joint of the bamboo plywood template.

[0014] As a further improvement of the present invention, the steel reinforcement cage is supported by T-shaped inner struts and laid flat on the outer surface of the mortar protective layer.

[0015] A method for supporting a foamed concrete arc-shaped formwork on the waterproof layer of a railway tunnel, comprising the following steps: A. Base protection: A waterproof layer is laid on the base surface of the tunnel lining, a mortar protective layer is poured, and it is cured to the design strength; B. Construction of internal support frame: Tie the arc-shaped steel reinforcement frame and lay it flat on the surface of the mortar protective layer; C. Template assembly: Bamboo plywood is spliced ​​along the arch ring towards the outside of the steel reinforcement skeleton to form bamboo plywood template; D. Anchoring point construction: Anchoring components are installed on the top surface of the longitudinal drainage ditch sidewall of the tunnel and on the vertical surface of the retaining wall of the mountain outside the tunnel. E. Tensioning system layout: The steel wire rope spans the arch and fits the circumferential joint of the bamboo plywood template, with both ends locked to the anchoring and fixing components. The tensioner tensions the bamboo plywood template synchronously and evenly, controlling it to have no outward bulging and no gaps. F. Pouring and Formwork Removal: Foamed concrete is poured in layers into the pouring cavity formed between the bamboo plywood formwork and the protective layer. After the foamed concrete has initially set, the tensioning device is loosened to release the tension, and the steel wire rope and bamboo plywood formwork are removed in sequence.

[0016] This invention provides formwork shaping support through an inner steel reinforcement skeleton, and uses outer arch-crossing steel wire ropes and tensioners for segmented tensioning, forming uniform radial compressive stress on the joints of the bamboo plywood formwork. The formwork is constrained by the permanent structures on both sides of the tunnel, completely eliminating the need for full-span steel pipe support on the outer side of the arch back, and eliminating the contact between rigid members and the waterproof layer structure.

[0017] Compared with the prior art, the present invention has the following advantages: 1. Structural and Waterproofing Benefits: This invention eliminates the need for full-span steel pipe uprights and through-wall tie bolts in the arch back. All supporting components are placed above the mortar protective layer, with no rigid components directly contacting the waterproof layer. This eliminates the risk of punctures, tears, and leakage in the waterproof layer at the source, significantly reducing the cost of subsequent tunnel leakage repairs. The steel wire rope is evenly tensioned along the circumferential joints of the bamboo plywood formwork, resulting in uniform stress on the arch surface. This effectively counteracts the lateral pressure of the foamed concrete, preventing formwork bulging and slippage. The arch back of the open tunnel has a smooth arc shape, significantly improving the forming quality.

[0018] 2. Economic benefits: The invention has a simple structure, reduces the input of steel pipes and other consumables, eliminates the traditional process of erecting steel pipes and timber back ribs, and eliminates multiple processes of transporting, erecting and dismantling steel pipes and timber, reducing labor by 40%; the simplified process shortens the overall construction period by more than 30%; bamboo plywood, tensioners and wire ropes can all be reused, continuously reducing the cost of consumable procurement in long-term projects.

[0019] 3. Construction safety and site efficiency on operating lines: This invention eliminates the need for dense steel pipe supports that occupy the protective space around the track, significantly reducing the site required for construction on operating lines and minimizing interference with normal train operations; it also eliminates the need for large steel pipe transport machinery to operate near operating lines, reducing the safety risks of machinery encroachment and train collisions.

[0020] 4. Energy saving and social benefits: It saves a large amount of steel pipes, timber and other wood and steel turnover materials, reduces building material consumption, and is energy-saving and environmentally friendly; it can be promoted to various arched waterproof structure foam concrete backfilling projects, and has high industry promotion value. Attached Figure Description

[0021] Figure 1 This is a longitudinal section schematic diagram of a foamed concrete arc-shaped formwork support structure for a waterproof layer on a railway tunnel according to the present invention. Figure 2 This is a plan view of the steel reinforcement cage in this invention; Figure 3 This is a schematic longitudinal section of the steel reinforcement cage in this invention; Figure 4 This is a plan view of the bamboo plywood template in this invention; Figure 5 This is a schematic longitudinal section of the bamboo plywood template in this invention.

[0022] In the diagram: 1-Cave lining; 2-Waterproof layer; 3-Mortar protective layer; 4-Reinforcing steel frame; 5-Bamboo plywood formwork; 6-Steel wire rope; 7-Tightener; 8-Embedded U-shaped steel bar; 9-Longitudinal drainage ditch; 10-Expansion hook; 11-Mountain retaining wall; 12-Foamed concrete; 13-T-shaped internal strut; 14-Bamboo plywood strip. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] Example 1 This example illustrates the flood control emergency project for the extension of the open-cut tunnel at K1734+151 on the Longhai Railway. A composite waterproof layer 2 of geotextile and EVA waterproofing membrane is installed on the arch of the open-cut tunnel on the operating line. A 1.0m thick foamed concrete layer 12 is designed as a buffer backfill layer on the arch back. The arch surface has an arc structure. The construction site is adjacent to the existing railway track, and it is strictly forbidden to damage the waterproof layer or for large machinery to occupy the traffic clearance for extended periods.

[0025] The railway tunnel is built against the mountain, requiring only half of the formwork support structure to be constructed.

[0026] like Figure 1-5 As shown, a foamed concrete arc-shaped formwork support structure for a railway tunnel waterproof layer includes an M10 mortar protective layer 3 poured on the exterior of the waterproof layer 2 of the tunnel lining 1. The mortar protective layer 3 completely covers the waterproof layer 2 and serves as the load-bearing base for the upper support system. The support components are placed entirely above the mortar protective layer 2 without direct contact with it. A steel reinforcement skeleton 4 is provided around the mortar protective layer 3. The steel reinforcement skeleton 4 is laid flat on the outer surface of the mortar protective layer 3 and arranged longitudinally and circumferentially along the tunnel, forming an inner shaped support for the formwork. The steel reinforcement skeleton 4 only serves as an inner lining support, with no members penetrating the mortar protective layer 3 or the waterproof layer 2. A bamboo plywood formwork 5 is provided on the outside of the steel reinforcement skeleton 4, forming a casting cavity between the bamboo plywood formwork 5 and the protective layer 3. Multiple sets of tensioning components are provided on the outer surface of the bamboo plywood formwork 5, arranged longitudinally along the tunnel.

[0027] The bamboo plywood template 5 is composed of multiple bamboo plywood panels spliced ​​together. Standard 1.8m long × 0.9m wide bamboo plywood panels are selected and spliced ​​in sections along the circumferential direction of the tunnel arch. The splicing seams between adjacent circumferential bamboo plywood panels serve as the external pressure stress points for the steel wire ropes.

[0028] The tensioning assembly includes a galvanized steel wire rope 6 and a tensioner 7. One end of the steel wire rope 6 is fixed to the top surface of the side wall of the longitudinal drainage ditch 9 on the side of the tunnel by a pre-embedded U-shaped steel bar 8, and the other end of the steel wire rope 6 is fixed to the facade of the retaining wall 11 on the outside of the tunnel by an expansion hook 10. The steel wire rope 6 is tightened by the tensioner 7 to generate an inward bearing force to counteract the lateral pressure of the foamed concrete pouring.

[0029] The steel wire rope 6 is attached to the outer surface of the circumferential joint of the bamboo plywood template 5.

[0030] The steel reinforcement cage 4 is supported by T-shaped inner struts 13 and laid flat on the outer surface of the mortar protective layer 3. The T-shaped inner struts 13 are horizontal supports at the end in contact with the mortar protective layer 3, which avoids local stress concentration and thus effectively protects the mortar protective layer 3 and the waterproof layer 2.

[0031] Waterproof layer 2 is a composite waterproof structure consisting of geotextile and EVA waterproof board laid sequentially from the inside out.

[0032] A method for supporting a foamed concrete arc-shaped formwork on the waterproof layer of a railway tunnel, comprising the following steps: A. Base protection: 1. Lay a waterproof layer on the base surface of the tunnel lining 2. Pour a 3cm thick M10 mortar protective layer 3. Cure to the design strength. B. Construction of internal support frame: Φ14 HRB400 steel bars are used to tie an arc-shaped steel frame 4 with a circumferential and longitudinal spacing of 900mm, and the whole frame is laid flat on the surface of mortar protective layer 3. C. Template assembly: 1.8m×0.9m bamboo plywood is spliced ​​along the outer side of the arch circumference and attached to the steel reinforcement skeleton 4 to form bamboo plywood template 5. A 10cm wide bamboo plywood strip 14 is set at the joint, and a circumferential through joint is formed between the boards as a tension stress joint. D. Anchoring point construction: On the top surface of the side wall of the longitudinal drainage ditch 9 on the side of the tunnel and on the vertical surface of the retaining wall 11 on the outside of the tunnel, U-shaped steel bars 8 and expansion hooks 10 are respectively installed for anchoring and fixing components. E. Tensioning system layout: A set of tensioning components is set every 0.9m. The steel wire rope 6 spans the arch and fits the circumferential joint of the bamboo plywood template 5 (located above the plywood strip 14 at this location). Both ends are locked to the anchoring and fixing components. The tensioner 7 tensions the bamboo plywood template 5 synchronously and evenly, controlling the bamboo plywood template 5 to have no outward bulges or gaps. F. Pouring and Formwork Removal: Foamed concrete 12 is poured in layers into the pouring cavity formed between the bamboo plywood formwork 5 and the protective layer 3. After the foamed concrete 12 has initially set, the tensioning device 7 is loosened in sections to release the tension. The steel wire rope 6 and bamboo plywood formwork 5 are removed in sequence. The steel wire rope 6, tensioning device 7, and bamboo plywood formwork 5 are then transferred to the next construction section for reuse.

[0033] Implementation results: 1. Waterproof layer 2 is free from scratches, punctures, and damage, and has no risk of leakage.

[0034] 2. The 12 arches of foamed concrete have a smooth shape and no defects such as bulging or displacement of the formwork. 3. The comprehensive cost of the support system materials is 68 yuan / ㎡, while the cost of the traditional steel pipe external support system is 78-92 yuan / ㎡, saving 10-24 yuan per square meter. Compared with the traditional steel pipe support, the material cost is 12,000 yuan.

[0035] 4. The project required 400 sheets of 1.8m×0.9m bamboo plywood, 105 wire tensioners, 1800m of steel wire rope, 650 steel wire rope clips, and 200 anchoring and fixing components (8 pre-embedded U-shaped steel bars and 10 expansion hooks), with a total material cost of only 44,300 yuan.

[0036] 5. The construction site area was significantly reduced, and no issues of mechanical encroachment or damage to the waterproof layer occurred.

[0037] This invention is a reinforced steel frame internal bracing + wire rope tensioner external pressure arc-shaped formwork support system. It eliminates contact between any rigid members and the waterproof layer, achieving zero damage to the waterproof structure. This effectively solves the technical problems of traditional full-span steel pipe support and tie bolts piercing the waterproof layer of the open-cut arch, leading to tunnel leakage. This invention significantly reduces the amount of reusable materials such as steel pipes and timber, lowering the material cost per square meter, reducing labor costs, and shortening the construction period on operational railway lines. It effectively addresses the economic problems of traditional support systems, such as high material consumption, high rental costs, large labor inputs, large site occupancy on operational railway lines, and long construction periods. This invention relies on the uniform tensioning and constraint of wire ropes along the circumferential joints of the formwork to improve the forming accuracy of the arch surface, eliminating defects such as formwork bulging and displacement. It effectively solves the forming quality problems of formwork bulging and poor alignment control under the lateral pressure of poured foamed concrete in arched formwork. This invention is particularly suitable for emergency flood control projects extending open-cut tunnels on operational railway lines where narrow working areas and where damage to the waterproof layer is strictly prohibited.

Claims

1. A foamed concrete arc-shaped formwork support structure for the waterproof layer of a railway tunnel, characterized in that: A mortar protective layer (3) is poured on the outside of the waterproof layer (2) of the tunnel lining (1). A steel reinforcement frame (4) is provided on the outside of the mortar protective layer (3). The steel reinforcement frame (4) is laid flat on the outer surface of the mortar protective layer (3). A bamboo plywood template (5) is provided on the outside of the steel reinforcement frame (4). A casting cavity is formed between the bamboo plywood template (5) and the protective layer (3). Multiple sets of tensioning components are provided on the outer surface of the bamboo plywood template (5). The multiple sets of tensioning components are arranged longitudinally along the tunnel.

2. The foamed concrete arc-shaped formwork support structure for the waterproof layer of a railway tunnel according to claim 1, characterized in that: The bamboo plywood template (5) is composed of multiple bamboo plywood panels spliced ​​together.

3. The foamed concrete arc-shaped formwork support structure for the waterproof layer of a railway tunnel according to claim 2, characterized in that: The tensioning assembly includes a wire rope (6) and a tensioner (7). One end of the wire rope (6) is fixed to the top surface of the side wall of the longitudinal drainage ditch (9) on the side of the tunnel, and the other end of the wire rope (6) is fixed to the facade of the retaining wall (11) on the outside of the tunnel. The wire rope (6) is tightened by the tensioner (7) to generate an inward holding force.

4. The foamed concrete arc-shaped formwork support structure for the waterproof layer of a railway tunnel according to claim 3, characterized in that: The steel wire rope (6) is attached to the outer surface of the circumferential joint of the bamboo plywood template (5).

5. The foamed concrete arc-shaped formwork support structure for the waterproof layer of a railway tunnel according to any one of claims 1-4, characterized in that: The steel reinforcement cage (4) is supported by T-shaped inner struts (13) and laid flat on the outer surface of the mortar protective layer (3).

6. A method for supporting a foamed concrete arc-shaped formwork on a waterproof layer of a railway tunnel, characterized in that: Constructing the foamed concrete arc-shaped formwork support structure for the waterproof layer of the railway tunnel as described in claim 4 includes the following steps: A. Base protection: (1) Waterproof layer is laid on the base surface of the tunnel lining (2), mortar protective layer is poured (3), and cured to the design strength; B. Construction of the internal support frame: Tie the arc-shaped steel reinforcement frame (4) and lay it flat on the surface of the mortar protective layer (3); C. Template assembly: bamboo plywood is spliced ​​along the outer side of the steel reinforcement skeleton (4) to form bamboo plywood template (5). D. Anchoring point construction: Anchoring components are installed on the top surface of the side wall of the longitudinal drainage ditch (9) on the side of the tunnel and on the vertical surface of the retaining wall (11) on the outside of the tunnel. E. Tensioning system layout: The steel wire rope (6) spans the arch and fits the bamboo plywood template (5) circumferential joint, with both ends locked to the anchoring and fixing components. The tensioner (7) tensions the bamboo plywood template (5) synchronously and evenly, controlling the bamboo plywood template (5) to have no bulges or gaps. F. Pouring and demolding: Foamed concrete (12) is poured in layers in the pouring cavity formed between the bamboo plywood template (5) and the protective layer (3). After the foamed concrete (12) has initially set, the tensioner (7) is loosened to release the tension, and the steel wire rope (6) and bamboo plywood template (5) are removed in sequence.

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