Tunnelling in soft soil: on the correlations between the kinematics of a Tunnel Boring Machine and the observed soil displacements

Abstract

Constructing tunnels in soft soil with the use of a Tunnel Boring Machine (TBM) may induce settlements. These include soil movements ahead of the face, soil relaxation into the tail void, possible heave due to grouting, long lasting consolidation processes, and potentially several other mechanisms (Mair et al. 1996). A considerable amount of the total soil displacements seems correlated with the passage of the TBM-shield. Even so, the TBM-induced soil displacements have so far only been coarsely correlated to the total settlements. This paper attempts to relate the shield geometry and its operation through the soil with the observed soil displacements. The snake-like motion of the shield within the excavated soil profile is one of the key aspects (Sugimoto and Sramoon 2002). In particular, the erratic advance of the shield appears to induce unevenly distributed ground displacements at the interface with the soil. These displacements spread through the soil with a similar pattern. A numerical investigation on the TBM kinematics and its associated observed soil response has been performed in order to quantify these aspects. The analysis has been based on the monitoring data from the construction of a road tunnel in The Hague, The Netherlands. Results confirmed that the geometry and the operation of the TBM-shield through the ground strongly influence the amount and distribution of the induced soil displacements.