Impregilo Salini Joint Venture
NWRL Skytrain between Kellyville and Rouse Hill, NSW

Formerly known as North West Rail Link, NWRL

Our involvement

JK Geotechnics completed an extensive and detailed geotechnical investigation, laboratory testing, monitoring and support during the construction phase for the NWRL Skytrain (surface viaduct) which takes Sydney Metro Northwest passenger trains above ground for four kilometres between Kellyville and Rouse Hill.  Our investigation included more than 150 cored boreholes (one at every viaduct support, plus other critical locations) to depths ranging from 16m to 35m, installation of multiple piezometers, test pit investigations for haul roads, and facilitation of acoustic and optical downhole imaging, falling weight deflectometer testing and Benkelman beam testing for pavements.  JKG also monitored inclinometers installed in several bridge abutments and temporary shoring piles.  JKG also completed numerous slope stability assessments and analyses for proposed excavations within the zone of influence of RMS roadways supplemented by 2D and 3D Plaxis modelling and analysis to assist the client demonstrate safe trafficability of large segment straddle carriers next to deep excavations.

Project challenges

The construction of the project required movement of very large plant and equipment (including 180 tonne straddle carriers and up to 500 tonne mobile cranes) around the site, and in close proximity to existing infrastructure (roads, optical fibre cables etc) and temporary works areas (including deep excavations).

Our solutions

The results of our numerical analyses enable the planned construction sequence to proceed in an effective manner whilst maintaining acceptable factors of safety.   Working platforms were required for large piling rigs, mobile cranes, straddle carriers and precast viaduct segment storage.  Where the surface soils were of insufficient strength, a mechanistic design approach was used to calculate the required thickness of select fill to distribute load to suitable pressures for the soft soil.  Based on stability analyses using SLOPE/W, we provided customised designs for safe working platforms adjacent to deep excavations. We also designed various bridging layers based on our client’s preferred materials (locally sourced) thus saving time and money.