ABSTRACT
It is well known that in Middle East airborne contaminant levels are particularly high. During severe storm conditions dust concentrations of the order of 100 to 500 times higher may be encountered. The effects of sand particles on the friction at the footwear floor interface are much more complicated than liquid contaminated conditions. Liquids on the floor tend to decrease the surface friction, but the sand particles on the floor may decrease or increase the friction on the floor, depending on factors such as particle size, tread design and hardness of the footwear pad, hardness and roughness of the floor.
 
In the present work, the effect of sand particles on the friction coefficient displayed by rubber sliding against ceramic tiles at different sliding conditions was investigated. Experiments were carried out under dry, water, detergent, oil, water oil emulsion.  Experiments were carried out with and without sand particles contaminating the sliding surfaces. Rubber test specimens of cylindrical and square protrusions were introduced in the surface of square rubber sheets of 100 ´ 100 mm and 10.0 mm thickness. A test rig was designed and manufactured to measure the friction coefficient between the rubber and ceramic flooring materials through measuring the friction and normal forces.
 
It was found that, at dry sliding, sand particles caused drastic decrease in friction coefficient. In this condition, it is recommended to use circular protrusion in the rubber surface. In the presence of water, sand particles embedded in rubber surface increased friction coefficient. Based on the experimental results, wet square protrusions are recommended to have relatively higher friction values. For surfaces lubricated by detergent, flat rubber embedded by sand particles gave higher friction than surfaces of protrusions, while sand particles embedded in rubber lubricated  by oil showed higher friction values. Circular protrusions gave higher friction than flat and square protrusions. Flat rubber surfaces, lubricated by water oil emulsion and contaminated by sand particles, displayed the highest friction coefficient.