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Session 2: Ground Movements Due to Tunnelling |
School of Engineering and Applied Science, University of Durham, South Road, Durham DH1 3LE, UK
Empirical equations suitably defining surface movements caused by tunnelling in uniform soils are now well-established. Settlements transverse to the tunnel line are usually and conveniently described by a normal probability equation in terms of ground loss, V(m3/m) and of distance to the point of inflection, i (m). Vis dominantly a function of tunnelling method, and i has been expressed explicitly as a function of depth, but dependent upon whether the soil type is granular or cohesive.
Little attention, however, has been given to the estimation of ground movements caused by tunnelling through a granular soil overlain by a cohesive stratum, and vice versa. The problem is addressed both by a simple extension to the expressions leading to the normal distribution settlement profile and the consequent transverse inward movements, and also by a linear elastic finite element model.
Two well-documented case histories are assessed by the two methods of analysis and both give acceptable estimates of ground movement.
