Centrifuge model testing of tunnelling-induced ground and pile deformations

Three centrifuge model tests have been performed to assess tunnelling-induc ed ground deformations in clays and their effects on adjacent pile foundati ons. The tunnel excavation procedure was modelled by 'equivalent ground los s values' and the specified ground loss values were achieved by reducing th e diameter of the model tunnel, and was designed to simulate the two-dimens ional tunnelling-induced ground movements. Model piles (a single pile and a 2x2 pile group) were pushed into the preconsolidated kaolin clay sample. T he performance of the pile group and the single pile were compared at the s ame time in the same package. Tunnel depths were varied in each test in ord er to assess the influence of tunnel depth on ground movements, axial pile forces, pile settlements, and lateral pile deformations. The models were in strumented substantially to measure tunnelling-induced vertical and lateral ground movements and the tunnelling-induced behaviour of the piles. A mode l 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) measur ed ground deformations and comparisons with empirical and analytical method s of estimation; and (c) tunnelling-induced performance of a single pile an d a pile group.