Swelling in Deep Residual Clays and Soft Rock

Deeply weathered residual clay and swelling soft rock is widespread in Southern Africa (see Fig. 1 for the distribution) and, like heaving clay, can have a major effect on the performance of engineering structures in the area of intluence. It would appear that the distress in surface structures founded on deep soft rock, which swells, is similar to that experienced on transported clays, or even on shallow residual clays, being caused by differential heave of the underlying material. However, deep swelling rock may also influence other engineering structures, such as tunnels or mining works, by causing heaving in underground floor levels, deterioration (slaking) of roofs and sidewalls of excavations, and crushing of concrete linings.