Design and Construction of the Access Tunnels for the New Top Ryde City Shopping Centre, Northern Sydney

摘要

This paper describes the design and construction of three 7.2 m span access ramp-tunnels to the threelevelrnunderground car park of the newly redeveloped Top Ryde City Shopping Centre in northernrnSydney. The tunnels were to be excavated without signifi cant impact on the overlying Devlin Street,rnone of the busiest arterial roads in the Sydney metropolitan area and a major link in the Sydney roadrnnetwork. The interpretation of the geological conditions indicated that the tunnels would be drivenrnin a formation of heavily jointed, extremely weathered to fresh Triassic Ashfi eld shale with somernstructural features such as dyke, fault and shear zones identifi ed in the available boreholes logs.rnBoth empirical and numerical methods were used to design the tunnels and to predict the groundrnsurface settlements. The design solution, which was infl uenced by the relatively small scale nature ofrnthe work and the current demands on the tunnel construction market, included presupport, initialrnsupport and permanent steel fi bre reinforced shotcrete (SFRS) lining. The interactions of the drivenrnportals with cut and cover sections and the proposed deep excavation of the new shopping centrernwere considered at the design development stage and in the construction phase to ensure the safetyrnof the live road. The tunnels have been successfully constructed and are now operational.