Probabilistic assessment of engineering rock properties in Singapore for cavern feasibility

Abstract

Singapore conducted various cavern studies since the 1990s, and has since constructed two caverns. The study done in this thesis concentrates on an area of interest within South-Western Singapore, using four logged boreholes that are each 200 meters in depth. Through the use of the empirical methods, the RQD and Q-system, rock support can be estimated for different ground classes for an assumed cavern size. The cost per cubic meter of cavern construction, which includes excavation support using bolts and shotcrete, and grouting, is then estimated. To account for the variability of the ground in the area of interest, probabilistic analyses and assessments of the rock mass parameters derived from the boreholes were carried out. Discrete probabilities were obtained from observed frequencies, and and depth and spatial variability are assessed. Depth Selector Maps (DSM) are created to give planners an indication of the ideal location of a cavern, both in depth and spatially, by providing them with an indication of the variability of the ground so that planners can take the associated uncertainty into consideration when making decisions.