2024 – Use of Geophysical Investigations to Optimise Remediation Work for a Concrete Reservoir

Sujatha Manoj, Scott Emmett

This paper presents a case study of a failure that happened at a large concrete reservoir site in an area with a history of ground risk due to presence of cavities, typically formed due to dissolution of limestone and gypsum. An optimised geotechnical and geophysical investigation program was implemented at this site to detect with reasonable level of accuracy the weak anomalous zones and cavities within foundation material, that caused the failure. The optimal use of geophysical investigation techniques Multi-Channel Analysis of Surface Waves (MASW) and ground penetrating radar (GPR) along with intrusive geotechnical investigations and observational methods, to assess ground risk and to arrive at efficient and economic foundation design and foundation remediation methods, are presented. Delineating the high-risk low shear wave velocity zones after calibrating the MASW data with borehole information and previous investigation data available from a desk study, it was possible to design and execute a grouting program to remediate the risk due to the underground anomaly within the foundation zone of the concrete reservoir. The case study presents a learning curve on how the combined use of sophisticated ground investigation techniques can help reduce uncertainty and increase data reliability. As a result of the study presented in this paper, a robust and sustainable remediation plan could be devised and executed to mitigate the problem that caused failure of a concrete reservoir. A second case study is also included in this paper, demonstrating how geophysical investigations complemented the geotechnical boreholes to remediate ground risk and uncertainty at a landfill site. The paper presents recommendations for optimum use of sophisticated ground investigation methods that allows us to design and engineer with confidence as it helps increase data reliability and arrive at safe and sustainable designs.