Open-Face Tunnelling Effects on Non-Displacement Piles in Clay i) Centrifuge Modelling Techniques

A research programme conducted at the University of Cambridge geotechnical centrifuge provided high-quality data on the interaction effects of open-faced tunnelling beneath non-displacement piles in clay. This paper presents details of the novel centrifuge package, including the reinforced composite piles used to measure loads during the centrifuge tests. Attention is particularly drawn to the importance of temperature compensation and the corresponding effect on the model piles. Results from maintained pile load tests conducted in the centrifuge are presented; through photogrammetric techniques, these are compared with data from pile load cells. The results, also compared with analytical t–z power-law modelling of the soil stress–strain behaviour based on triaxial tests, illustrate the importance of modelling the full history of both soil and piles prior to any subsequent tunnelling-induced loading. The experimental results of the simulated tunnelling tests on piles are presented and compared with simple analytical solutions in a companion paper.The first author acknowledges the financial support provided by Arup Tunnelling and the Engineering and Physical Sciences Research Council for an Industrial Case Studentship