Experimental and numerical studies on the mechanical behaviour of Australian Strathbogie granite at high temperatures: An application to geothermal energy. (March 2015)

• Record Type: Journal Article
• Authors: Shao, Shishi; Ranjith, P.G.; Wasantha, P.L.P.; Chen, B.K.
• Is Part Of: Geothermics. Volume 54(2015:Mar.)
• Page Start: 96
• Page End: 108
• Publication Date: 2015-03
• Subjects: Geothermal -- Granite -- Brittle–plastic -- High temperature; Hydrogeology -- Periodicals; Geothermal resources -- Periodicals; Énergie géothermique -- Périodiques; GEOTHERMAL ENGINEERING; GEOTHERMAL ENERGY; GEOTHERMAL EXPLORATION; Geothermal resources; Hydrogeology; Periodicals; Electronic journals; 621.44
• DOI: 10.1016/j.geothermics.2014.11.005
• Languages: English
• ISSNs: 0375-6505

Abstract

Highlights: We explore the effect of temperature on mechanical behaviour of fine grained Strathbogie granite. Brittle–plastic transition is observed between 600 and 800 °C. XRD test results illustrate the phase of granite changes during heat treatment. AE responses show how temperature affects stress thresholds and stable crack propagation. Finite element (FE) model is incorporated to predict both elastic and plastic behaviour of granite at high temperatures. Abstract: The effect of temperature on the mechanical behaviour of Strathbogie granite (fine-grained) was studied under unconfined stress conditions. Fracturing behaviour of test specimens was studied using an acoustic emission (AE) detection system and some crack propagation was also performed using electron microscopy scanning (SEM). The stress–strain curves showed plastic and post-peak behaviour for temperatures above 800 °C and the brittle–plastic transition was observed to occur between 600 and 800 °C for the uniaxially tested Strathbogie granite at a strain rate of 0.1 mm/min and room humidity. Specimens were heated at a rate of 5 °C/min with a 1 h holding period before testing. The AE results showed that the increasing temperature reduces the stress thresholds for crack initiation and crack damage and extends the duration of stable crack propagation. Prevalence of ductile properties with increasing temperature was also observed from AE results. The stress–strain and AE results reveal that the failure modes of Strathbogie granite specimens changed from brittle fracturing to quasi-brittle shear fracturing and eventually to ductile failure with increasing temperature. Temperature was observed to influence the colour of granite, and the initial white/grey colour changed to an oxidated reddish colour with increasing temperature. The stress–strain data of tested specimens were incorporated into a finite element model (ABAQUS 6.7.1), so that both plastic and ductile behaviour of the Strathbogie granite could be predicted over a wide range of temperatures.