ABSTRACT
Mass movements on slopes can range in magnitude from soil creep on the one hand to instantaneous and colossal landslides on the other. Sharpe (1938) defined creep as the slow downslope movement of superficial rock or soil debris, which is usually imperceptible except by observations of long duration. Walker et al. (1987) suggested that creep could be regarded as mass movement that occurs at less than 0.06 m per year. Creep is a more or less continuous process and a distinctly surface phenomenon. It occurs on slopes with gradients somewhat in excess of the angle of repose of the material involved. Like landslip, its principal cause is gravity, although it may be influenced by seasonal changes in temperature, and by swelling and shrinkage in surface rocks. Other factors that contribute towards creep include interstitial rain washing, ice crystals heaving stones and particles during frost, and the wedging action of rootlets. The liberation of stored strain energy in the weathered zone, particularly of overconsolidated clays with strong diagenetic bonds, is another contributory cause of creep (Bjerrum, 1967). Although creep movement is exceedingly slow, there are occasions on record when it has carried structures with it.
