Cast in-situ Cross Passages: Thermal Stress Assessment

Summary

The C310 Thames Tunnel comprises twin 2.72km long bored tunnels between North Woolwich and Plumstead Portal. Four cast in-situ cross passages link the tunnel drives and the junction between the running tunnels and cross passage linings are made by RC collars cast in-situ on the primary sprayed concrete lining (SCL). Since the collars are regarded as thick concrete elements there was a risk of early-age cracking due to high hydration temperature and thermal calculations based on CIRIA C660 and 2D numerical modelling were carried out to provide predictions on the collar performance. Additionally, a series of thermocouples were installed on site to register the actual temperature developed in the collars during first 28 days after casting.

Thus, this paper seeks to compare the design of the early-age concrete approach with on-site assessment results from the installation of the thermocouples in the cross passage collars, and to make recommendations on the design assumptions and on-site operations to be undertaken in the future.