The variation of uniaxial strain and cohesion of the Three Gorges Project (TGP) granite with temperature and time has been studied by means of uniaxial and triaxial compressive creep tests at high temperature. The influenceof temperature and time on deformation and strength of the TGP granite has been revealed. The mechanical model for fitting uniaxial stress-strain relation and deformation characteristics has been proposed, and the empirical formulas of variation of cohesion with temperature and time has been put forward as well.
The purpose of studying mechanical properties of rock is to predict their mechanical responses under the given load. The research on time-dependent mechanical properties of rock by labaratory tests is of great importance to calculating and analyzing long-term stability of underground structures, and to predicting the long-term safety of slope and mine projects. Starting from 1958, Prof. Tan Tjon-kie, as the pioneer in this field,performed a great deal of theoretical and experimental research. In 1985, he systematically summarized the relevant research achievements (Tam. 1982). Internationally the understanding to time effect of rock experienced a considerably long process. Until 1979, when the 4th International Congress of Rock Mechanics was held in Switzerland by ISRM, the rock rheology was put forward specially, and listed as the first special topic. From then on rock rheology has been studied as animportant subject in many countries. The main researches are focused on: time effect of deformation; time effect of strength, and the constitutive relations concerning time considered. The most celebrated are Cristescu et al, whose representative works mainly is Rock rheology(Crstescu, 1988). In addition, Rogers and Tanner, by their deep-going research and summarization in this field, have accomplished a complete works of rock theology. In many engineering fields, the variation of mechanical properties of rock with temperature should also be taken into account. therefore, the research on the influence of temperature on mechanical properties of rock is necessary. From the 1960's a great deal of research have been performed on the variation of basic mechanical properties, such as compressive strength, modulus of deformation, Poisson's ratio, viscosity, thermal expansion coefficient and so on, with temperature. Heuze (1983) madea summarization on the research works before 1980. In addition, Johnson and others (1978) studied the thermal cracking of rock by means of AE technology. Aver et al (1981) performed research on the steady-state creep of fine-grained granite in melting condition. Simpson (1985) analyzed the brittle-ductile transformation behavior of granite at high temperature. Wang Jintao (1987) studied the high temperature effect on fracture toughness of granite.
All the specimens in the tests are taken from the same piece of rock so that the homogeneity and the comparability of test data can be guaranteed. This piece of rock is a fresh granular granite mined in the Three Gorges Project, Yangtze River. It is grey and black and mainly composed of quartz, feldspar, amphibole, biotite and a small quantity of cementing substance.Specimens undergo coring, cutting. and polishing.
