Ngoepe, Thapelo Wilfred2023-01-182023-01-182021https://hdl.handle.net/10539/34119A research report was submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering, 2021Coal spontaneous combustion (CSC) is a major concern in the exploitation and utilisation processes of coal. Various methods for prohibiting the spontaneous combustion of coal have been developed. This study aimed to determine the causes of spontaneous combustion of coal and assess the effectiveness of calcium sulphate dihydrate (gypsum) on spontaneous combustion at Khwezela Colliery in Mpumalanga, South Africa. In order to exploit coal at favourable costs at Khwezela Colliery, gypsum was applied to two drill holes and one coal stockpile affected by spontaneous combustion. Temperature changes of the three drill holes and coal stockpiles were measured daily for 21 days from 06h00 to 16h00. Data from the holes and stockpiles were represented graphically and analysed using one of the statistical techniques called t-test. Furthermore, a t-test of two samples assuming unequal variances was used, and the significance level of 0.05 was chosen. The test statistic critical value was 2.1 for the stockpiles and 2.0 for the holes. The absolute value of test statistics obtained from comparing the hot holes ranged from 0.0 to 1.7. At the same time, the absolute value of test statistics for comparisons of the same sides of the stockpiles ranged from 3.6 to 4.3. The treated stockpile produced an absolute value of test statistic of 2.0. The analysis has revealed that gypsum is effective in managing the spontaneous combustion of stockpiles. An increase in the concentration of gypsum resulted in a decrease in the spontaneous combustion of the treated stockpile. Similarly, an increase in the concentration of gypsum resulted in a decrease in the in-hole temperature fluctuation. The use of gypsum in managing spontaneous combustion results in a decrease in the operation costs, safety and productivity of mining operations affected by spontaneous combustion.enThesis