Geophysical characterization of variable limestone terrains

Abstract

Between November 2005 and October 2006, a series of geophysical surveys were conducted over newly released industrial lots in the Australian Marine Complex (AMC) in Henderson. The objective of the surveys was to characterise the subsurface geology as preliminary geotechnical investigations of the site showed this to be highly variable. Primarily through the use of GPR, with some additional ERI and MASW testing, we were able to successfully delineate the depth to limestone rock head, location of limestone pinnacles and thickness of gravelly fill layers where present over the site. This information was used in the geotechnical assessment of the sites and subsequent planning of earthworks to ensure the sites were developed to the required geotechnical standards. GPR using shielded 250MHz antennas was found to be the most effective method to characterise the subsurface (at 50MHz the GPR had insufficient resolution), MASW effectively imaged the depth to rockhead and variations within the limestone and ERI imaged hydrogeological variations.