Complete Guide: Tunnel Lining Formwork for Circular, Horseshoe & Rectangular Sections

Tunnel lining formwork is a critical component in underground construction, directly influencing structural integrity, construction speed, and cost efficiency. Whether you are working on railway tunnels, metro systems, or hydraulic projects, the cross-sectional shape of the tunnel—circular, horseshoe, or rectangular—dictates the specific formwork system required. This comprehensive guide explores the unique characteristics, design considerations, and application scenarios for each shape, providing you with the knowledge to make an informed procurement decision.

Circular Tunnel Lining Formwork: Precision in Radial Geometry

Circular cross-sections remain the most common in tunneling due to their exceptional load distribution and hydraulic performance. The formwork system for circular tunnels must achieve high geometric accuracy to ensure uniform concrete thickness and watertightness.

Key Design Features

• Full-round telescopic formwork: Typically segmented into two or more telescopic panels that retract radially for striking and advance for pouring.
• Adjustable diameter range: Quality systems allow for ±5% diameter adjustment to compensate for over/under excavation.
• Hydraulic operation: Powered by synchronized hydraulic cylinders for uniform movement and reduced cycle time.
• End sealing system: Effective grout seals at both ends to prevent leakage during high-pressure concreting.

Circular formwork excels in projects with high internal water pressure or variable ground conditions. The continuous curved surface eliminates stress concentrations, making it ideal for deep tunnels and subaqueous crossings.

Horseshoe Tunnel Lining Formwork: Optimizing Space for Utilities

The horseshoe shape—essentially a circular arch with vertical sidewalls and an invert—offers a compromise between structural efficiency and usable floor area. It is widely adopted in railway and highway tunnels where space for ventilation, walkways, and equipment is essential.

Formwork Configurations

Horseshoe lining formwork typically comprises three main components: the arch crown form, sidewall forms, and invert form. Advanced systems integrate these elements into a single traveling gantry that moves on rails, enabling rapid sequential pouring. Key considerations include:

• Arch-to-sidewall transition: The geometry requires careful planning to avoid cold joints. Gangda Intelligent's continuous pour system eliminates intermediary construction joints.
• Variable width adaptability: Many projects use multiple horseshoe widths within the same alignment. A modular formwork system with interchangeable arch segments provides cost-effective flexibility.
• Invert integration: The curved invert section demands robust formwork that can withstand concrete pressure while maintaining profile accuracy.

Compared to circular sections, horseshoe tunnels provide approximately 15–25% more usable cross-sectional area for the same excavation volume, making them a favorite for transportation tunnels.

Rectangular Tunnel Lining Formwork: Maximizing Clear Span for Infrastructure

Rectangular sections are prevalent in cut-and-cover tunnels, underground metro stations, and pedestrian underpasses. Their flat surfaces simplify alignment of equipment and optimize space utilization. However, the sharp corners introduce stress concentrations that require robust formwork design.

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