Identification of ground subsidence due to collapse of solution cavities in marble rock

Abstract

Ground subsidence can occur due to reasons such as; oil/gas/water extraction, mining, and dissolution of carbonate rocks. Identification of potential subsidence locations are usually difficult due to limited information and complexities in the subsurface profile. This research focuses on the ground subsidence occurring due to the collapse of solution cavities in marble rocks. Accordingly, two locations in Matale and Badulla districts which had previously encountered subsidence in the marble rock band of the Highland Complex were surveyed using Ground Penetrating Radar (GPR) to generate cavity profiles of 2D trace analysis of the radargrams. The GPR interpretations were validated using the well-log data and the records on the previous ground subsidence reports. Several GPR surveys conducted in Matale region indicated the presence of solution cavities in marble rock. The increasing number of cavities towards the river in the region can be considered as the influence of the groundwater movements on cavity formation. The resultant cavity profiles of T01-T02 were compatible with available well-log data (MA 182) and indicated that the accuracy of subsurface details that can be gathered using GPR technology. Similar conditions were observed in the Badulla area and showed the evidence of groundwater induced solution cavities in marble rock. Hence, to minimize the ground subsidence hazards, it is recommended to conduct GPR surveys to obtain subsurface information, prior to future construction or development activities on the regions where marble bearing bedrock is present.