Centrifuge Study on the Influence of Tunnel Excavation on Piles in Sand.

Tunneling-induced ground movements can affect the equilibrium state of an existing pile, causing uneven settlement among pile groups and damage to connected structures. This paper presents results from five centrifuge tests aimed at evaluating the load redistribution mechanisms that occur within piles located close to tunnel excavation. Two main mechanisms are studied: first, those related to ground displacements and stress relief related to tunneling and, second, those related to pile head load changes caused by connected superstructures (accomplished using a hybrid centrifuge-numerical modeling method). A novel fiber Bragg grating sensor system was used to measure shaft shear stresses along model piles. Results are used to quantify the relative impact that these two mechanisms have on pile load redistribution during tunnel volume loss. In addition, posttunneling pile loading tests were performed, with results indicating that tunneling-induced ground volumetric strains could influence the posttunneling loading response of piles. [ABSTRACT FROM AUTHOR]