Geohazard investigation in karst areas with electrical resistivity imaging methods

摘要

Sinkholes, voids and active faults are often a major geohazard in a karst area. This paper demonstrated the effectiveness, of electrical resistivity imaging methods in locating these geohazards. We presented three case histories in karst areas on sinkhole investigation, cave detection and active fault study. As electrical resistivity data collection with a multi-electrode and multi-channel resistivity system is getting increasingly faster and commercial resistivity inversion programs are readily accessible, more and more people have been conducting 2D and 3D resistivity surveys. Electrical resistivity imaging methods are extensively used in resolving environmental and geotechnical problems. In this study, we used AGI SuperSting R8, an 8-channel 28-electrode resistivity imaging system, for rapid data collection. Our resistivity data were processed with AGI Earthlmager 2D resistivity data inversion software. The Dr. Death Sinkhole showed a near-surface conductive anomaly on top of a massive resistive anomaly that may be produced by either an air-filled void or unweathered limestone. The sinkhole caused about one meter ground subsidence that provided rooms for moisture accumulation which reduced the resistivity of this sinkhole. The air-filled Trench Cave produced a resistive anomaly as normally expected. Accurate location of sinkholes and caves prevented an energy company from installing utility poles or burying utility pipes on top of a sinkhole or a cave. The active Hockley Fault was characterized by a sharp lateral resistivity contrast on the 2D resistivity cross section. The downthrown side of the fault is more conductive than the other side of the fault due to increased clay and moisture contents at the downthrown side. Our studies demonstrated that resistivity imaging methods are an effective tool for geohazard investigation in karst areas.