ABSTRACT
Thermal effects play a key role in rock engineering and they strongly affect the quality and engineering stability of rock mass. Increasing or decreasing the temperature of rocks will cause the development and extension of inner cracks. Intact rocks are usually constituted by different minerals whose thermal expansion coefficients differ. Under varying thermal conditions the cracks will be initiated and extend, intersect and merge between the minerals due to the inconsistent deformation and finally the rock mass will lose its strength. The the effect of temperature or heat-treatment on the mechanical properties of rocks is believed to be related to the evolution of microstructures and to depend on factors such as size, number and orientation of microcracks and bedding planes in the material. In modern rock engineering disciplines, including rock weathering, rock drilling, ore crushing, deep petroleum boring, geothermal energy extraction and deep burial of nuclear waste the influence of temperature has to be taken into account (Heuze, 1983). In ancient times there are several examples where the effect of temperature was used for the excavation of rock mass. When the Dujiangyan
2 GEOLOGICAL SETTING AND INVESTIGATION OF THE OLD MINING PIT
The Suichang gold mine is located in the ChencaiSuichang orogenic belt between the ShaoxingJiangshan fault zone and the Yuyao-Lishui fault zone and belongs to the Wuyi metallogenic belt of Cathaysia (Wang et al., 2000). In this area the exposed stratum is a kind of dual structure stratum.
