Large Caverns in Difficult Ground Conditions

Large unlined underground rock caverns is one of the alternative available for large buffer storages of crude oil all around the world. However extreme geological conditions combined with stringent project schedules always pose challenges to engineers for construction of such large underground caverns. Uncertainties associated with construction of such large underground structures can always introduce a component of surprise for any expert designer working in this field. Thus stability of these geotechnical structures is critical both during the construction as well as operational stage. Although the design of these underground structures follow a systematic approach based on the rock mass-classification system, this design needs to be continuously updated based on the information gathered as the excavation work progresses and follows an observational approach of engineering and design. This paper discusses case studies of construction of large underground rock caverns at three different sites which encountered unexpected/changed geology during construction stage. The way these geological uncertainties were dealt with are discussed in detail in this paper.