Engineers Australia

Liquefaction and settlement assessment for the Mortimer Road Bridge, Perth, Western Australia

Geoffrey Cocks, Michael Hillman and Keith Simpson


This paper presents the results of an assessment of liquefaction and settlement for a freeway interchange bridge founded on siliceous sand in an area of shallow water table at a site located south of Perth in Western Australia. The effect on liquefaction of factors such as the depth to groundwater, earthquake magnitude, ground acceleration; load applied to the soil and the depth and thickness of zones of loose sand is discussed. The study confirmed that the liquefaction potential was very low.

Predicted soil settlement was relatively large and was addressed by surcharge preloading of the site. Settlement of the preload embankment was monitored leading to an improved understanding of the non-linearity of settlement versus load response, and the development of a relationship between modulus and electric friction cone penetrometer resistance. The results from this site were compared to results from a calcareous sand in Perth, for which a relationship following a similar approach has previously been derived.