1 Jul 2017
1 Dec 2017 (Extended to 10 Jan 2018)
15 Jan 2018
16 Apr 2018 (Extended to 15 Jun 2018)
From 16 July 2018
By 17 September 2018
Professor in Resources Engineering
Department of Civil Engineering at Monash University
Thu-02 Nov 2018 | 09:15 – 09:45 | Summit 2
"Rock Fracturing by Low Power Microwave Treatments – Observation, Mechanism and Application"
Low power microwave treatments are applied to induce micro-cracks in hard rocks, with the aim to apply microwave to assist mechanical fragmentation and fracturing of hard rocks. Systematic laboratory tests have been conducted on the common rock forming minerals and selected hard rocks. Dielectric properties (the ability in absorbing microwave energy, and reflected by heating rate) of the common minerals are measured and grouped (e.g., biotite and hornblende as the good microwave absorbers, orthoclase feldspar as the intermediate and quartz, plagioclase feldspar, olivine and muscovite as the poor microwave absorbers) and can be used to predict dielectric properties of natural rocks. Tests are conducted on selected hard rocks with observations and measurements on heating rate, spatial temperature distribution, ultrasonic velocities, strength, crack pattern and crack density. The results indicate that the single-model microwave system can significantly weaken some of the hard rocks treated at 2 kW for 120 seconds. Systematic tests on rocks with different mineral composition and different saturation conditions reveal there are possibly three mechanisms leading to rock fracturing by microwave heating. They are differential thermal expansion of the minerals, mineral phase change, and pore-water vaporisation. Overall test results indicate the potential of using microwave to enhance the fragmentation and fracturing of hard rocks that are often difficult for mechanical breaking alone. Applications of microwave technology in TBM, roadheader and rockbreaker to assist mechanised excavations of hard rocks are examined.
Jian Zhao teaches and researches rock mechanics and underground technology at universities and practises rock engineering through consulting. He is currently a professor in the Department of Civil Engineering at Monash University in Australia, the Vice President of the Monash University – Southeast University Joint Research Institute. He is also an adjunct professor at Southeast University in China. He is an Editor-in-Chief of Tunnelling and Underground Space Technology journal, a casual Technical Principal of SMEC consulting in Melbourne. He obtained PhD on rock mechanics at Imperial College London in 1987, was a faculty at Nanyang Technological University of Singapore in 1990-2005, and a professor of rock mechanics and tunnelling at Ecole Polytechnique Fédérale de Lausanne of Switzerland in 2005-2015. He was a Vice President of the International Society for Rock Mechanics (ISRM) in 2003-2007, inducted to ISRM Fellow in 2015, an Executive Board Member of the International Tunnelling and Underground Space Association (ITA) in 2001-2004, and an Independent Director of Singapore Exchange listed Terretech Group in 2013-2017. He has supervised about 50 PhDs and authored/co-authored over 400 publications and has a Scopus H-index over 40.