The Runway End Safety Area (RESA) is part of the upgrade plan of the Sydney International Airport and adds an extension to the end of the runway. As this area passes through a number of existing facilities it will have to be bridged over a heritage listed sewer, an airport perimeter road and the existing highway road.
The area of RESA was previously low lying farming land with major alterations in the ground contours due to previous construction works. The site is on man-made filling up to 4 m thick from earlier dredging works and predominantly marine originated alluvium. Soft mud deposits are extensively spread over the area and groundwater level is quite shallow.
The loads introduced by bridging RESA over existing structures and lowering the road level at the intersection with RESA required specific geotechnical measures.
Jet Grouting has been used successfully in RESA with multiple purposes such as increasing the ground’s bearing, retaining the ground and creating impermeable barriers to cut off the flow of water during construction. Multiple requirements and variations in ground conditions required a detailed design with a number of Jet Grout column diameters, lengths and combinations. Design included finite element analyses using Plaxis and later verified by sampling of grout and installing inclinometers to measure ground deformations.