UQ PhD students Sasan Moravej and Mutaz Mahmoud have been recently awarded the Runner-up Best Paper Award at EUROCK 2022, the prestigious ISRM conference, which is one of the most significant rock mechanics symposia worldwide. Their research entitled: “Coupled Thermo-Mechanical Study of Crack Initiation Stress Threshold in Porous Sandstone” aims to investigate the effect of temperature increase on the failure of underground mines and tunnels using the state-of-the-art true triaxial testing facility at the Geotechnical Engineering Centre of the School of Civil Engineering.
The increasing depth of tunnels and underground mining operations worldwide has resulted in the rise of deep mines at temperatures well above 50°C. Such unwanted thermal gradients not only adversely impact the physical and mechanical behaviours of the rock mass but could also affect the safety of underground mines leading to temporarily and permanently shutting down the operation. The combination of high temperature and high-stress conditions further culminates in explosion-like fractures like rockburst and spalling, which are the main problems in deep mining and tunnel constructions. Spalling is identified as an abrupt explosion-like rock failure that occurs spontaneously and can endanger tunnelling and mining operations, causing injuries and fatalities and necessitating investigation of the effect of temperature on rock behaviour. A state-of-the-art multifunctional true triaxial testing system equipped with an elevated temperature facility (up to 100o C), with humidity control in which a thermo-mechanical model can be developed was recently set up at the Geotechnical Engineering Center of the School Civil Engineering at the University of Queensland. Sasan and Mutaz, under the supervision of Dr. Mehdi Serati and Prof. David Williams, conducted intensive experimental testing to investigate the influence of coupled thermo-mechanical conditions on the spalling failure of sandstone samples through stress-strain-based models. The results suggest that temperature can significantly impact the in-situ spalling failure of underground rock, particularly at low confinement. This study suggests that the thermal variation shall be considered in the design of underground mining tunnels.
