Integration of Direct and Indirect Techniques to Optimize Subsurface Exploration

Abstract

Subsurface exploration is one of the major activities conducted to extract information for Geotechnical applications. Borehole construction is the most common direct exploration technique which provides exact information on a particular location whereas, Electrical Resistivity Method is one of the commonly practiced indirect exploration techniques. Since the exploration costs are relatively high, minimizing the cost while obtaining adequate information is of everyone’s interest. For larger constructions with deep foundation requirements, determining the overburden thickness (bedrock level) and water table is a mandatory requirement. Hence, the use of a proper combination of direct and indirect subsurface exploration methods could result a considerable cost reduction and time saving. This study was conducted to find an optimum integration of resistivity method and borehole construction for selected subsurface exploration activities currently in progress. Accordingly, resistivity surveys were conducted at sites proposed for a twelve storied residential tower at Malabe and Matara – Kataragama Railway Extension Project, near piers for new railway track. Apparent resistivity data were gathered using ABEM – Terrameter SAS 1000 instrument, were interpretated using “IP 2 Win” software. The results were validated using the borehole information. The resistivity survey information revealed a close relationship with the borehole data and resides within the statistically acceptable range. Hence, an optimum combination of resistivity surveying and borehole construction can be proposed, for cost controlling at large-scale subsurface explorations.