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, Australian Centre for Geomechanics, Perth, pp. 397-408, https://doi.org/10.36487/ACG_rep/1508_26_Shen
This paper describes how monitoring data was used during construction to refine the design of a large span cavern built in Ashfield Shale in Sydney. The cavern is part of a rail tunnel project comprising 15.5 km of twin tunnels. The cavern is 160 m in length, with a height of up to 17 m; it spans 23 m, with a cover of between 14 and 17 m. Instrumentation used during construction comprised surface settlement survey, in-tunnel convergence using both survey and tape extensometers, borehole inclinometers, ShapeAccelArray (SAA) inclinometers, multipoint rod extensometers, wire extensometers, endoscopes and vibrating wire piezometers (VWP).
Based on the observed ground conditions and monitoring during construction, it was possible to revise rock mass and in situ stress parameters to refine the design. Design changes included increases in advance distances, revised pile lengths and spacing, optimisation of the mesh reinforced arch and a revised excavation profile. These changes resulted in a significant reduction in construction time and a more economical overall project outcome.
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