Samenvatting
Measurements of ground settlement caused by the construction of a one-metre diameter tunnel are described, together with tests on soil samples taken from the tunnel face and in situ shear strength measurements made with a pocket vane tester. The tunnel was driven to a depth of about 7 m through a soft to very soft silty clay having an average vane shear strength of about 50 km/m2. The maximum ground surface settlement recorded was 56 mm and the cross-sectional area of the settlement trough at the same point represented more than 42 per cent of the area of the tunnel face. (Author/publisher)