Design and Construction of Shaft in Jurong Formation Sedimentary Rocks of Singapore
It is commonly accepted the development and use of underground space in rock caverns is one of the major solutions to meet the increasing demand for space in Singapore. Due to the relatively flat terrain here, vertical shaft shall be one important alternative for accessing deep underground. Experiences have demonstrated that the main shafts are often the critical structure for cost-effective construction of the rock caverns and safe operation of the underground facilities. For the Jurong formation the shaft penetrates through reclamation materials, residual soil, and weathered rock before reaching the solid bedrock. Structural design in the overburden (diaphragm walls or piling) and rock support in the bedrock section are crucial in ensuring stability and integrity of the shaft. Another key aspect is on how to prevent or reduce the water inflow into the shaft to provide a safe, comfortable and cost-effective construction and operation environment. Finally, the paper proposes three alternatives for accessing underground caverns and discussed issues relevant to the shaft design optimization.