A MARRIAGE between botanical science and civil engineering would be a rare one, but it would be a union from which rail authorities might profit handsomely.
University of Wollongong civil engineering PhD student Behzad Fatahi has developed a computer model that shows that planting native trees close to railway lines can save rail authorities millions of dollars spent on stabilising the soil beneath tracks. It may also help homeowners choose the best trees for their gardens.
The NSW company RailCorp spent about $2 billion between 1995 and 2005 on track maintenance, Mr Fatahi said, but his model could drastically reduce that bill.
The rail industry commissioned the development of the model after workers saw that tracks near trees required less maintenance.
Mr Fatahi said it was clear from field observations at Miram in western Victoria that trees growing about 15m to 25m from rail lines, whose roots reached under the rails, kept the soil there compact and dry.
Where there was a large gap between trees at Miram, "we could see by eye that there is a dip in the railway".
"A tree can influence soil around to 30m then after that we have got a sort of settlement. When a train is passing and applying a dynamic load, the soil can settle easier," Mr Fatahi said.
His model, developed under the umbrella of the Rail Co-operative Research Centre and with partner the University of South Australia, uses the dimensions and absorption rates of roots, the transpiration rates of leaves and climate information to show that water take-up by trees increases the "stiffness" of soil near them, strengthening the soil beneath rail tracks.
"By having these values and using our model now we can predict in one single tree what is the distribution of moisture content. This is absolutely new," Mr Fatahi said.
"The model is an interaction between the atmosphere, the tree and the soil."
The best tree in the Miram area was the blackbox, a type of eucalypt.
The model also had an application for the insurance industry.
The next stage of the project was to try to develop a model that would tell homeowners what distance from a house to plant particular types of tree.
Mr Fatahi's work was a recent winner in Wollongong's Higher Degree Research Student Conference in the category of Frontier Technologies for Building and Transforming Australian Industries.
Source: The Australian