Abstract

Large deposits of coal over vast expanse of lands attract mining companies, power stations and petrochemical companies and thus the development of coal towns with rail and road networks. High traffic volume of large quantities of coal across coal cities often result in the gradual accumulation of fine coal dust particles on road pavements, rail ballast and sleepers.  The effect of coal dust on the Direct Shear Friction Angles (DSFA), Direct Shear Interface Friction Angles (DSIFA) and Direct Shear Modulus (DSM) of uniformly graded gravel aggregate were investigated. The results show that at increased coal content, the DSFA of the gravel tends to the DSFA of the coal. The rate of decrease of DSFA was dependent on the moisture content of the coal fouled gravel. The DSIFA was higher than the DSFA at any degree of coal fouling. The DSM at small displacement was more sensitive to changes in moisture content of the fouled gravel than friction angles and is thus a better indicator of coal fouling effect.

Key words: Angle of friction, gravels, direct shear strength, interface shear strength.