How Wide Can A Rock Cavern Be Opened?

The largest known cave, Sarawak Chamber, which is in the Gunung Mulu National Park, Malaysia, is a remarkable natural wonder and measures 700m by 400m and over 70m in height. A cave of this size can fit the entire city streets and skyscrapers. Theoretically, empirical rock and structural mechanics principles could be used to interpret these physical phenomena of large span rock-opening structures. On this basis, hypothesizing a jointed-rock cavern could be supported by reinforced rock arch using rock reinforcement techniques formed by application of confining pressure via the bolts or cables, utilising the inherent strength of the rock to support the rock load above the opening. This reinforced arch is considered as a continuous arched-structural beam all along the cavern. Generally, rock caverns and tunnels are designed mostly to be arch shaped, either circular or parabolic. However, the function of arch shape, geometry, span and ratio of the rise of arch for rock excavations have seldom been discussed, together with rock reinforcement applied on the opening periphery. An investigation initiative is proposed to examine the maximum span of the opening with respect to the critical load of the arch for the opening; properties of rock mass; and other variable coefficients related to geometry of the arch. This is done by using the rock reinforcement method together with the Dinnik’s equation, which is a simplified rule with variable coefficients for the analysis of the elastic arch when the loss of stability occurs. A numerical model is conducted in this paper to get a preliminary concept and agreement on this combination applications between rock mechanics and structural design. A desktop investigation initiative is outlined at the next stage for further verification of the concept on how wide a rock cavern could be opened.