Planning, Investigation and Design of the Junk Bay Road Tunnel, Hong Kong

The 900m long Junk Bay Road Tunnel will be driven through a saddle with bedrock consisting of hard, strong but fractured rhyolitic volcanic. The easternmost 200m will be cut and cover tunnel beneath a platform to be developed for public housing. Areas of concern for the driven tunnel are the groundwater flows and pressures, including artesian flows, and the effect of drawdown on agricultural plots and village housing. The concurrent construction of an overlying reservoir, and the presence of the village, have raised the need to assess blast vibrations. The cut and cover tunnel, with across-section similar to the driven tunnel, is of reinforced concrete, designed to accommodate the loads from a 6-storey building. The driven tunnel will have rock bolt and shotcrete support and an unreinforced concrete lining.