Managing Sinkholes at Project Site, A Saudi Arabian Case History

The sub-surface geology of the Project Site, in at least six out of a total of eight Zones, are characterized by presence of highly to moderately weathered and fractured Limestone formation. This is generally encountered at a depth ranging from surface to 1.50 meter. However, there is yet another dimension to this geology. A typical characteristic of this bedrock is the presence and occurrence of numerous small to large Cavities, Sinkholes and/or Limestone Solution Channels, which are often found to be filled with clay/silt/sand. A serious program was undertaken to map all these Karstic features. An extensive “Cavity Search Probing” was conducted under footprints of each building to ensure the competence of the strata below. The probing was done using “Pneumatic Driving” of a Rock Probe into the bedrock using a Wagon Drill, with compressed air to clean the hole as it advanced. Semi-Rigid Raft Foundation was used to circumvent the Cavities & Sinkhole problems at the Site. This paper focuses on the experiences vis-à-vis the above and brings to light the Case History leading to managing and circumventing the Sinkholes & Bedrock Cavities at the Project Site per se