Engineering Geology and Hydrogeology Aspects of Sedimentary Jurong Formation in Singapore: Implication on Safe Excavation of Underground Storage Caverns

The first commercial underground rock caverns for hydrocarbon storage in South East Asia, the Jurong Rock Caverns (JRC) Project, has recently been completed in Singapore. Extensive in situ permeability tests in boreholes and intact strength testing on rock cores were carried out to determine required design parameters in feasilibity study stage and during construction period. In-situ horizontal stresses of rock mass were measured in construction stage. After correlation between hydrogeological test results and geological characteristics of the tested interval, the geological and hydrogeological model is established. Geology face mapping were performed at every location after blasting of rock faces for the records of discontinuities parameters, Geological Strength Index (GSI), Tunnel Quality Index (Q) and Rock Mass Rating (RMR). The general correlation equation between Q and RMR in JRC is established. From the intact strength properties, equivalent rock mass parameters were successively determined after applying relevant GSI and D (Excavation Damage Factor) of rock masses. The main aim of this study is to document the new discoveries of the project including observation after broad analyses on the engineering properties for stability of the project.