ABSTRACT
The assessment of tunnelling induced ground responses in the urban environment often focuses only on the final displacement profiles without considering their progressive development. Transient movements, especially in the longitudinal sense, can have relevance when assessing structural response and potential damage. Comprehensive field monitoring data from three instrumented research sites in London have been analysed (Hyde Park relating to the Elizabeth Line and St James’s Park and Southwark Park to the Jubilee Line Extension Project), although the focus of this paper is on the responses observed at the Hyde Park site. Valuable insights into short-term transient surface ground responses to tunnelling have been gained. They are classified into three phases, based on the relative TBM position. Often there is uncertainty about where to define the end of short-term and start of long-term tunnelling-induced ground responses. The data analysed strongly suggest that the ‘end of short term’ be taken to be as the end of Phase 2, when x f ~ 30 m (the distance of the TBM face from the monitoring line. Various normalisation approaches have been applied to the monitoring data to help unify them and provide overall generic ground responses to be developed and compared. For example, it was established that the shape of the developing transverse trough remains constant at all stages for both symmetric and asymmetric troughs.
