Impact of Temperature Variation on the Coefficient of Thermal Expansion of Selected Rocks from South African Platinum Mines in an Unconfined Conditions

Abstract

This paper presents the results of the study on the impact of temperature variation on the coefficient of thermal expansion of selected rocks from the South African platinum mines. These mines are witnessing increasing temperatures with higher depth due to high-temperature gradient. The experiment on the rock samples was done using a special set up comprising a variac, oven, digital thermometer, digital video extensometer, etc. under varying temperatures (20 to 140°C). The results of the laboratory tests. It is observed that the coefficient of linear thermal expansion increases with increasing temperature for all the samples. However, in comparison with other samples, chromitite has the lowest expansion coefficient. This was attributed to its lower strength and weak bond within the grain boundaries. The tests also show that temperature has an influence on the failure of crack generation and extension, which caused expansion of rocks. It is an indication that as mining depth increases in platinum mines, there is a possibility of an increase in tensile failure, which is not only a product of increased in-situ stresses but temperature. The future design of deeper and hotter mines would also hugely benefit from the knowledge of rock’s response to thermal stresses derived from laboratory tests.

Keywords: Temperature testing, thermal expansion, platinum mines

DOI: 10.7176/ISDE/10-4-02

Publication date:May 31^st 2019