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 kn/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.(a)

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