Franklin To - Hong Kong

Franklin is a Chartered Engineer with over 5 years of experience in civil and geotechnical engineering. He is a professional member of the Institute of Materials, Minerals & Mining (IOM3) and the Institution of Civil Engineers (ICE). He received his Bachelor's degree in Civil Engineering from the Hong Kong Polytechnic University in 2014. Following his graduation, he joined AECOM as a graduate engineer to undertake the design of civil and geotechnical works. In 2016, he was promoted to Assistant Resident Engineer to carry out site supervision and contract administration works on a large-scale highway tunnel project with contract sum of £900 million. He also completed his part-time Master’s degree in Geotechnical Engineering from the University of Hong Kong in 2018.

Franklin is now a Geotechnical Engineer of the Tunnel & Cavern team at AECOM in Hong Kong. His areas of specialisation are predominantly design, construction, site supervision and project management of tunnels, rock caverns, explosives blasting, slope stabilisation, deep foundations, deep excavations and ground investigation works.

A comparison of empirical and numerical approaches for estimating rock support pressure on tunnel lining

In Hong Kong, the rock support pressure acting on the permanent tunnel lining is usually estimated using the empirical equations by Terzaghi's arching theory (1946) and the Barton's Q-system (1974). However, with the advanced methods, the assumptions made in these studies become too conservative. This presentation investigates the differences in estimated support pressure using empirical approaches and Finite Element Modelling (FEM) to develop a cost-effective solution. The influence of missing parameters in empirical equations and the rock mass behaviour surrounding the tunnel excavation are also studied.

It is found that the in-situ stress ratio k and rock mass quality are very significant to the support pressure. However, the influence from varying Young's Modulus Ei, Poisson's ratio v and Uniaxial Compressive Strength (UCS) are negligible. Also, the empirical approaches are not conservative to design spaced tunnels, unless further verified by FEM.

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