Ground improvement for transportation infrastructure in Australia
In coastal regions of Australia, high population density and increased traffic volumes has led to the expansion of transportation infrastructure. Such developments have necessitated the use of ground improvement techniques in response to environmental legislation and requirements for improved performance and sustainability. In this paper, a brief overview of innovative ground improvement techniques in the major areas such as railway embankments, port reclamation and uncontrolled fills is provided. Ballasted rail tracks are often placed on freshly quarried ballast, which offers the desirable resiliency to cyclic and impact loads. However, ballasted beds often need periodic maintenance due to deformation and degradation associated with breakage. Recycled ballast is a cheaper and environmentally viable option but its strength characteristics need to be investigated beforehand. The assessment of different types of geosynthetics for improving the stability and drainage of railway tracks under high cyclic loading is also necessary. Field tests were carried out to measure the in-situ stresses and deformations of ballast on sections of instrumented track at Bulli and Singleton, New South Wales (NSW), Australia funded and built by RailCorp and ARTC, Australia respectively. Stabilization of soft subgrade soils using prefabricated vertical drains (PVDs) is also essential for improving the overall stability of track and reducing differential settlement during the operation of trains. The effectiveness of using PVDs has been observed through field measurements and finite element analyses. Due to an increase in trade activities at the Port of Brisbane, Queensland (Qld) new facilities on Fisherman Islands at the mouth of the Brisbane River will be constructed on the new outer area (235ha) adjacent to the existing port facilities via land reclamation. A vacuum assisted surcharge load and conventional surcharge scheme in conjunction with PVDs was selected to reduce the required consolidation time through the deeper subsoil layers. The design of the combined vacuum and surcharge fill system and the construction of the embankment are described in this paper. The 45 ha reclamation project involving the Outer Harbor extension of Port Kembla in Wollongong, NSW provided the opportunity of examining the potential use of coal wash (CW) and steel furnace slag (SFS) as the predominant reclamation fill. Detailed laboratory investigations indicated that there are optimum CW-SFS mixtures that may meet most of the geotechnical specifications to be used as an effective structural fill. A field application at Penrith Lakes, NSW of a new methodology employing the field evaluation of shear wave velocity (Vs) (i.e. Multichannel Analysis of Surface Waves MASW) combined with matric suction (ua − uw) or moisture content was
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