LAI KING ROCK TUNNEL COMPLEX - DESIGN AND CONSTRUCTION

The recently completed Lai King Tunnels form part of the new Lantau and Airport Railway (LAR) and comprise four new 0.4 to 0.6km long, rectangular and D shaped, single and double track running tunnels. Existing infrastructure and alignment constraints required the tunnels to be constructed in close proximity both to each other and the existing Operating Railway (Tsuen Wan Line). The resulting small tunnel separations, less than 3 metres vertically and horizontally between spans up to 13 metres were such that the intervening rock pillars required 'state of the art' analysis using discrete element code (UDEC) and the design of permanent rock reinforcement. Carefully controlled blasting practise with appropriate trials to develop site specific relationships between blast designs and induced vibrations allowed the excavations to progress without damage to adjacent structures. This paper discusses the rock reinforcement system design and tunnel construction. For the covering abstract see IRRD E102185.