Engineers Australia

Differentiating Fill and Natural Soft Clays – The Value of Desktop Studies in Building a Geological Model

Luke Johnstone

November 12, 2021Sydney Symposium 2021

This paper presents the methodology and rationale used when differentiating fill and natural soft clays in a site on waterfront reclaimed land. The area of reclaimed land has a history of settlement impacting existing developments, which has motivated careful consideration of the ground conditions for future works. As the reclaimed land was dredged locally then loaded by fill and warehouses, it closely resembles the underlying estuarine and marine sediment lithology and consistency.

Two historical ground investigations and one Arup ground investigation have been conducted, including clusters boreholes, cone penetrometer tests, seismic dilatometer tests and lab testing. The four types of subsurface information were compared to build and verify a ground model with an emphasis on the extent of reclaimed land. Peripheral desktop study information including historical maps, imagery, sea level records, and the historical settlements observed at site were considered to assist in differentiating the fill and natural soft clays. The importance of understanding this site’s history reinforces the value of a thorough desktop study when developing geological models.

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