ABSTRACT
The North Strathfield Rail Underpass (NSRU) Project includes the construction of a 148 m rail underpass under live railway tracks at North Strathfield for freight trains. This paper presents design of the tunnel support structure concentrated on factors of geotechnical and structural aspects. The geotechnical aspect has been focused on opening stability, ground-support load share, tunnel deformation and surface settlement in consideration. Ground reaction curves are developed by applying material softening and load reduction methods to two dimensional models created using Phase2. These curves were then used to estimate the likely amount of load share between the shotcrete lining and the surrounding ground. Simple 2D and 3D structural modelling of the first six meters of support immediately after excavation was conducted to assess the imposed structural actions on the temporary and permanent tunnel support. The structural actions were compared with the calculated Ultimate Limit State (ULS) structural capacity of the support system during construction and in the permanent conditions.
