ABSTRACT
Circular shafts are an integral component of infrastructure development schemes which exploit underground space. However, limited design guidance exists for such structures and the cautious approach often adopted by designers can have significant impact on the shaft construction costs and the protective measures implemented for adjacent buildings and services. In the UK, Crossrail is a major tunnel construction project underway to improve transportation links across London and the South East. Several deep circular shafts were constructed to facilitate access and egress of plant and personnel to and from the tunnel horizon and to provide ventilation and emergency access. This paper describes the findings from a comprehensive review of field observations associated with construction of four of the Crossrail shafts. The data is invaluable to understanding the behaviour of circular shafts and the adjacent ground. Different techniques for constructing shafts are evaluated and the important effect of dewatering is highlighted.
