Observational Approach in Construction of Large Caverns

The Observational Approach constitutes an important episode in the journey of underground geotechnical design and construction. Despite certain disadvantageous consideration of the approach, pointed by several workers, it induces flexibility in design and/or construction, of the project based on actual ground behaviour revealed through direct observation as well as monitoring of instrumentation data. This helps in optimisation of resources and at the same time reduce risk and increases safety and stability of underground structures. The present paper is focussed on adaptation of the approach in connection to design and construction of unlined mined crude oil storage cavern in India. The paper describes a case study on updating of geological model of an identified geological hotspot through observation during investigation and subsequent construction stages and design of rock support based on updated model resulting in a safe as well as optimum design.