The nature and occurrence of known deposits of dispersive clays in Southern Africa are descriptionbed. The main testing procedures for the identification of these clays are given and it is stressed that all clays considered for construction should be tested for potential dispersiveness. Methods of constructing safe and economic structures with dispersive clays are also given with references to some case histories.
This paper reviews the background and extent of the expansive soils problem in South Africa. The origin of expansive soils is discussed and indicators of heaving conditions which should be recorded during the site investigation are identified. An appraisal is given of the traditional and more recent methods of heave prediction and the selection of suitable foundation types is reviewed. Recommendations are provided for the design of stiffened raft foundations.
The paper reviews the state of the art of current engineering practice in South Africa with regard to soils which have a collapsible fabric. This includes a discussion on the collapse phenomenon and the distribution of soils with a collapsible fabric in South Africa. The development of procedures to identify collapsible soils and to quantify collapse is presented. Consideration is also given to engineering solutions to the collapse problem.
Damage to structures and loss of life have been far more severe on dolomite than on any other geological formation in South Africa. The subsidence which occurs on dolomitic terrain following development or during dewatering has given dolomite a notorious reputation and many developers have become reluctant to build on it. The problems experienced in this country have led to the pioneering of investigation and founding methods for dolomite sites. In this paper methods of site investigation best suited to the different types of dolomite site are presented. A method of classifying the site in terms of overburden thickness is given, followed by a review of the evaluation methods in use. The paper also discusses various methods of construction.