Empirical, Analytical Methods for Surface Settlement Prediction Due to TBM-Tunnelling in Dutch Soft Soil

TBM-tunnelling in soft soil causes a 3D-ground deformation field, developing in longitudinal direction (parallel to the axis of the tunnel) and transverse direction (perpendicular to the axis of the tunnels). Empirical based methods are used for the prediction of the distribution of ground movements in both directions. Consequently the differential settlements are used to predict the damage risks of adjacent buildings due to TBM-tunnelling in the design stage. The Gaussian-curve is commonly applied for the prediction of green field ground movements transverse to the tunnel axis. Different authors derived methods for determining the characteristic inputparameter i, being the point of inflexion for the settlement trough on surface level for tunnelling projects all over the world. The i-value determines the steepness of the trough. This paper presents a comparison between the different approaches derived from data of projects outside the Netherlands and the field data from three recently bored Dutch tunnelling projects (i.e. the Second Heinenoord Tunnel, the Botlek Railway Tunnel and the Sophia Railway Tunnel). Recommendations are suggested for the use of the empirical methods for Dutch soil conditions representing soft soil and high groundwater level