A tunnel lining trolley, also known as a tunnel formwork system, is a specialized piece of equipment essential for the secondary concrete lining of a tunnel. The selection of the correct trolley is a critical decision that directly impacts the safety, efficiency, and quality of a tunnel project. The main factors to consider when choosing a tunnel lining trolley are the tunnel’s geometry, the construction method, the required production rate, and the level of automation.
Tunnel Lining Trolley Selection Guide
Introduction: What is a Tunnel Lining Trolley?
A Tunnel Lining Trolley, also known as a formwork gantry or shuttering carriage, is the backbone of the cast-in-situ concrete lining process in tunnels. It is a large, mobile steel structure designed to:
Support the Formwork: It holds the steel molds (forms) in the precise shape of the tunnel’s final concrete lining.
Facilitate Concrete Placement: It provides access and infrastructure for pouring concrete into the cavity between the formwork and the excavated rock/soil surface.
Strip and Advance: After the concrete has cured, the trolley hydraulically retracts the formwork (strips it) and moves itself forward to the next section to repeat the process.
Selecting the right trolley is not just a procurement decision; it is a critical engineering choice that directly impacts project speed, quality, safety, and budget. A poorly chosen trolley can lead to construction delays, poor concrete finish, and significant safety hazards.
Types of Tunnel Lining Trolleys
Tunnel lining trolleys can be broadly classified based on their function, design, and the type of lining they install.
Cast-in-Place (CIP) Trolleys: These trolleys support formwork into which concrete is poured to create a seamless, monolithic tunnel lining.
Telescopic Formwork Trolley: The most common type for long tunnels, the formwork sections retract or “telescope” inwards after the concrete has cured, allowing the entire trolley to pass through the newly cast section and move to the next work area without being dismantled.
Full-Round Formwork Trolley: This type carries formwork for the entire tunnel cross-section (invert, walls, and arch) and allows for a single concrete pour, making it ideal for circular or near-circular tunnels.
Arch Formwork Trolley: This trolley is used when the tunnel invert (floor) is cast separately. It carries the formwork for the upper arch and sidewall sections and is commonly used for horseshoe-shaped tunnels.
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