Effects of high temperature on strength, deformation, thermal properties and creep of rocks

The authors have proposed and discussed temporary storage of heated water in openings excavated in rock moun-tain from the viewpoints of multiple-utilization of land, environmental safeguards, energy conservation, etc. When used for heated-water storage, the rock mass around the openings will receive the effects of the heated water. In this study, for obtaining physical properties used for analysis of thermal behavior of rock mass around openings, the effect of the difference between Wet (the water-retaining condition) and Dry and physical properties on strength, deformation characteristics and thermal properties at high temperatures were examined using 5 kinds of rock (granite, andesite, sandstone, tuff and mudstone). In addition, a uniaxial compression creep test at high temperatures of the rock was also carried out, then compared with the creep property at room temperature. The calculation of various constants on the creep was tried using Burgers model. In outline, the results show the strength of Wet rock is smaller than that of Dry, and strength lowers with the rise in the temperature, the lowering proportion being larger in Wet. The elastic modulus of tuff and mudstone are smaller than those of granite, andesite and sandstone. In particular, the lowering proportion at high temperatures is also large in Wet. Thermal property can be considered almost constant for practical use, and the effect of the temperature is small. As the difference of Dry and Wet is large, it seems that the effect of pore water is large. Especially, the tendency is remarkable in tuff and mudstone in which porosity is large. Temperature influences the uniaxial compression creep property of rock.