Centrifuge model testing of tunnelling-induced ground and pile deformations

Three centrifuge model tests have been performed to assess tunnelling-induced ground deformations in clays and their effects on adjacent pile foundations. The tunnel excavation procedure was modelled by ‘equivalent ground loss values’ and the specified ground loss values were achieved by reducing the diameter of the model tunnel, and was designed to simulate the two-dimensional tunnelling-induced ground movements. Model piles (a single pile and a 2 × 2 pile group) were pushed into the preconsolidated kaolin clay sample. The performance of the pile group and the single pile were compared at the same time in the same package. Tunnel depths were varied in each test in order to assess the influence of tunnel depth on ground movements, axial pile forces, pile settlements, and lateral pile deformations. The models were instrumented substantially to measure tunnel ling-induced vertical and lateral ground movements and the tunnelling-induced behaviour of the piles. A model scale of 1/100 was used, with a nominal centrifuge acceleration of 100 g. This paper presents: (a) details of the centrifuge model setup; (b) measured ground deformations and comparisons with empirical and analytical methods of estimation; and (c) tunnelling-induced performance of a single pile and a pile group.