Future Of Australian Rail Tracks Capturing Higher Speeds With Heavier Freight

In Australia, quicker and more cost effective commuter and freight transports are essential to cater for the needs of travel demand and supply chains in the mining and agriculture sectors. Such development in coastal areas would necessitate the use of ground improvement techniques in response to environmental legislation and requirements for improved performance and sustainability. In coastal Australia the high cost of track maintenance is the main issue due to poor drainage of soft coastal soils, ballast degradation, fouling (e.g. coal and subgrade soil), differential settlement of track, pumping of subgrade soils and track misalignment due to excessive lateral movements. Hundreds of millions of dollars are spent each year on the construction and maintenance of rail tracks and the existing technical specifications, standards and design are often unable to address these problems. With increased train speeds, the capacity of the track is often inadequate unless more resilient tracks are designed to withstand the substantially increased vibration and cyclic and impact loads. The optimum use of maintenance funds is a challenging task due to the absence of comprehensive methods to predict track longevity even on terrain where the properties of the soils are well established. Until today, the vast majority of Australian track designs have considered ballast and structural fill as elastic granular media, and thus the designers have adopted predominantly empirical methods where true cyclic loading patterns and the onset of plasticity and degradation of track materials are ignored. In many European countries and some parts of Southeast Asia, especially among high speed rail networks, track vibrations are serious concerns. The mechanisms of ballast degradation and deformation, the need for effective track confinement, understanding the interface behaviour and the imperative need for flood protection, time dependent drainage and filtration properties of track materials requires further research to improve the existing design guidelines and Australian Standards for future high speed commuter and heavier freight trains. Field studies on instrumented tracks at Bulli (near Wollongong) and Singleton (near Newcastle) supported by RailCorp and ARTC, were carried out to measure the in situ stresses and deformation of ballast embankments. The application of prefabricated vertical drains (PVDs) to stabilise soft subgrade soils was introduced for the first time in Australia to improve the overall track stability in Sandgate (near Newcastle). The effectiveness of using PVDs was observed through field measurements and finite element analyses. In this keynote paper, the current state-ofthe-art knowledge of rail track geotechnology in Australia and around the world is discussed. The paper focuses on primary research and development of new design and construction concepts for enhanced track performance, highlighting examples of innovations from theory to practice. Through case studies, the paper also introduces predictive and design tools for practitioners via user-friendly approaches.