Engineers Australia

Geotechnical aspects of karst within the Swan Coastal Plain, Western Australia

Philip Mather

Abstract

The occurrence of karst limestone conditions within Western Australia is not well recognised within the general community but can be of major engineering significance for developments that are impacted by it. The presence and engineering significance of karstic limestone on the Swan Coastal Plain has been recorded by local Engineering Geologists with the first officially published recognition presented in the 1:50,000 scale Environmental and Engineering Geology Series Yanchep Sheet in 1986. The Geological Survey of Western Australia (GSWA) mapping highlighted a significant, well defined zone of karst phenomena within Tamala Limestone extending from Joondalup to Two Rocks. Increasing pressure from urban development along Perth’s northern corridor lead to several “near miss” incidents which precipitated the incorporation of a requirement for all development applications within the City of Wanneroo to include consideration of the potential for karst.

To date, the published literature relating to karst on the Swan Coastal Plain has been limited to geological descriptions of the phenomena. Although the potential karst hazard is now widely recognised within the geotechnical community there has been very little published information relating to geotechnical design considerations and strategies for urban development within areas affected by karstic limestone relating specifically to the Swan Coastal Plain. Considerable work has been completed over the past decade relating to the identification of karstic ground conditions and geotechnical design strategies to manage potential risks. In addition, the existence of additional areas of karstic limestone has been identified within the City of Cockburn and City of Mandurah.