ANA HOTEL, SYDNEY, EXCAVATION ADJACENT TO A MAJOR RAILWAY TUNNEL. SEVENTH AUSTRALIAN TUNNELLING CONFERENCE; THE UNDERGROUND DOMAIN, SYDNEY, 11-13 SEPTEMBER 1990; PREPRINTS OF PAPERS

The excavation for building basements adjacent to existing tunnels in Sydney is becoming increasingly common. Although Sydney sandstone is an ideal medium in which to excavate for deep basements, their close proximity to existing railway tunnels requires additional design and construction supervision compared to other sites in similar material. This paper presents a case history of a recently completed excavation on the ANA Hotel site. The excavation required the removal of approximately 55,000 cum of rock. The lift core of the 38 level building is located within a few metres of an existing twin track railway tunnel. Major building loads were transferred past the tunnel via caissons and the rock above and adjacent to the tunnel was reinforced by a combination of grouted dowels and tensioned ground anchors. Finite element analyses were carried out to assist in the design of the protection measures adopted for the tunnel. The site was monitored by inclinometers, conventional surveying methods and by strain gauges placed over existing cracks in the tunnel lining. In-situ rock stress measurements were also carried out as part of the site investigations. (Author/TRRL)