Skip to main navigationSkip to main content
The University of Southampton

Research project: Interface characteristics in composite sprayed concrete lined tunnels

Currently Active: 

Over the last twenty years, sprayed concrete lined (SCL) tunnels have seen rapid development in their use, particularly for forming large underground spaces such as station concourses for urban metro lines. A waterproofing membrane is normally required around the tunnel, and a convenient way to achieve this is by a sprayed membrane applied to the inside of the primary SCL layer, before the secondary SCL is added. There is an uncertainty however in the extent of composite action that can be relied upon between the primary and secondary linings in these circumstances when the membrane is sandwiched between the two. This project is aimed at addressing this uncertainty. If it can be shown that composite action is present, an efficient utilisation of both primary and secondary linings in the complete structure should be possible, leading to significant savings in overall lining thickness and cost.

SCL tunnel under construction
SCL tunnel under construction

A testing programme of short and long-term compression, tension and direct shear tests has been carried out on samples cut from SCL panels built up with a primary layer, sprayed waterproofing membrane and sprayed secondary layer. These tests have demonstrated the mechanical properties of the concrete-membrane-concrete interface for different surface roughness and membrane thickness.

Tension test on SCL tunnel sample with waterproofing membrane
Tension test

The degree of composite action available between the primary and secondary linings through the membrane interface has been validated through further laboratory tests on beam samples, the results of which have been used to calibrate a numerical model of the composite shell lining. This modelling approach has in turn been applied to typical full-scale tunnel geometry to examine the influence of the composite action between the lining layers on the behaviour of the tunnel as a whole. Parametric studies have been carried out with variation of interface parameters and secondary lining thickness, and preliminary results show it should be possible to achieve savings in overall lining thickness.

The research is supported by Mott MacDonald, international consulting engineers, and by Normet (UK), construction (mining and tunnelling) products manufacturer.


Associated research themes

Structures and Solid Mechanics

Geomechanics and Environmental Geotechnics

Related research groups

Infrastructure Group

Key Publication

Share this research project Share this on Facebook Share this on Twitter Share this on Weibo
Privacy Settings