ABSTRACT
To meet the demand for high quality, sustainable and cost-effective tunnels, innovation in tunnelling methodologies is essential. Slipform Tunnelling is an innovative construction process which utilises a novel lining material formulation injected into an articulated slipform under high pressure, enabling continuous and efficient tunnelling. This method has the potential to halve the cost of tunnel construction and deliver substantial improvements in safety, sustainability, programme as well as durable, resilient, maintenance-free assets.
Constructability issues with the equipment and with lining materials have resulted in similar tunnelling concepts (extruded tunnel linings) being unsuccessful. This paper presents the research and development of the Slipform Tunnelling process and a uniquely formulated Slipform Tunnel Lining Material (STLM) to enable efficient delivery of new tunnels or the relining of existing tunnels.
The development process used a systematic approach, initially considering performance requirements before undertaking iterative design and verification through testing and analysis. With Slipform Tunnelling employing high-pressure injection to form the lining, the design approach was to harness this feature to improve the lining properties in-situ. Bespoke equipment was developed to enable high-pressure forming and testing of trial mixes in the laboratory, with the ability to simulate the injection process. Extensive trials were undertaken to optimise all components of the novel formulation.
Triaxial testing at very early-age (one hour after forming compression) found that the developed STLM possessed appreciable strength and stiffness. Numerical analysis showed that Slipform Tunnelling with the developed STLM ensured stability and limited deformation, with high advance rates found to be achievable. Durability tests demonstrated that the developed STLM was low shrinkage and met the requirements for resistance to abrasion and sulfate attack. Most notably, whole-life embodied carbon and cost analysis has shown that Slipform Tunnelling can halve the cost and carbon of tunnelling, opening up new possibilities.
