Abstract

Underground infrastructure has been a widespread alternative in redeveloping urban spaces to ease congestion pressure arising from land scarcity. It has often served as vital lifelines for transport, utility and storage purposes. They include subway train and highway tunnels, gas, electrical, water and sewage pipelines. However, in the event of an earthquake, the functionality of these lifelines could be put into jeopardy especially in soils susceptible to liquefaction.

Historically and recent earthquake events have proven the floatation susceptibility of underground structures. Such structures passing through liquefiable soil deposits are susceptible to floatation due to their lower unit weight as compared to the surrounding saturated soil. Centrifuge test results will be presented to describe the soil-structure interaction involved in floating tunnels and pipes in liquefied soil deposits.

The influence of the 1)mass, 2)buried depth, and 3)diameter of the structure, as well as the 4)type, 5)relative density, 6)permeability of the sand will be covered in the presentation. The soil deformation around the soil would also be illustrated with the use of PIV analysis. A simplified mechanism of the floatation will be shown and applied to predict uplift displacement of buoyant structures.