Non-linear Analysis of Soft Ground Consolidation at the Ballina By-pass

摘要

This study presents a numerical assessment of consolidation under vacuum preloading with arnsystem of vertical drains and membrane, considering the non-linear properties of the soil Thisrnmembrane system, already widely used in Australia, is where an airtight membrane is placed overrnthe drainage layer to allow a vacuum to be distributed within the sand platform, along the surfacernof the soil, and down the vertical drains. To date, there have only been a few fundamentalrninvestigations and field studies that have tried to assess the way in which the vacuum canrnpropagate in soft clay, both laterally and vertically. In this model, both vertical and horizontalrndrainage was considered to reflect more realistic in-situ conditions. Moreover, the change ofrncompressibility and permeability during consolidation was taken into consideration, including arnpossible loss of vacuum along the length of the drain. This model was initially verified for a singlerndrain using large scale laboratory testing, and subsequently applied to a fully instrumented casernstudy, namely the Ballina Bypass (along the Pacific Highway, NSW). The numerical solutionsrncapturing the lateral distribution of the vacuum provided accurate predictions of the pore waterrnpressure and associated settlement.