Zijun Feng

Effect of Temperature on Deformation of Triaxially Stressed Anthracite

Coal is a particular organic rock that is sensitive to temperature and pressure. The physical–mechanical behaviors of coal bed as influenced by the coupling of temperature and pressure are different from those under conventional testing conditions in engineering applications such as underground coal gasification (UCG) and coal-bed methane heat-injection extraction (CMHE). Coal-bed deformation is related to channel formation, distribution and propagation in UCG, and affects the formation of hightemperature vapor channels in CMHE significantly. Therefore, the investigation of thermal deformation coupling with temperature and pressure is of great significance in the analysis of the channel and roof stability and surface subsidence in UCG, and the formation of heat flow channels in CMHE. In the last decades, extensive laboratory research has been performed on rock samples exposed to high temperatures to investigate temperature influence on physical, thermal and mechanical properties. Wong and Brace (1979) measured thermal expansion of six rocks involving granite, diabase, marble, limestone, dunite and quartzite and found that thermal expansion of six rock samples was typically irreversible after heating above room temperature and the coefficient of thermal expansion of a rock is usually much higher than the average coefficients for the minerals in the rock at temperature of 2–38 C and confining pressure up to 600 MPa. Heard (1980), Heard and Page (1982) studied the coefficient of linear thermal expansion of Climax Stock quartz monzonite, Westerly and Stripa granites and concluded that the coefficient of linear thermal expansion for these rocks was neither constant with nor a simple function of temperature or pressure at effective pressures of 0, 13.8 and 27.6 MPa and temperature up to 300 C. Heuze (1983) reviewed linear thermal expansion coefficient variation with temperature for numerous granites and concluded that a sharp increase in expansion before the as bs transition and great decrease occurred beyond the transition temperature. Lin (2002) measured the permanent strain of thermal expansion on Inada granite which increased almost exponentially. Dwivedi et al. (2008) studied coefficient of linear thermal expansion of India granite at temperature up to 200 C and room pressure. The conclusion is clear that thermal expansion of rock is nonlinear. In addition, thermal deformation of some sedimentary rocks such as sandstone and claystone was also measured and had the similar evolution characteristics & Zijun Feng fzj3893811@126.com