An improved version of a method proposed by the writer a few years ago for estimating the initial settlements of structures founded on sands is presented. The California Bearing Ratio (CBR) test is considered to be a model of a prototype of which the settlement is desired. CBR values are determined from Standard Penetration Test or dynamic cone CBR Penetrometer Test data. In the past the application of this approach was hampered by the lack of knowledge about the stress history of the particular soil profile. A procedure for determining this state is now advanced. From this results are derived which give an insight into the geological history of the soil profile. The effect of the presence of a water table, lowering the water table or altering the overburden pressures before a load is applied is taken into account. Several case studies reported in the literature since this approach was originally proposed have been analysed to verify the method and to illustrate its application.
Connected to the sea by a narrow estuary, St Lucia lake is a shallow, generally saline water body situated on the sub-tropical east coast of northern Natal. The lake constitutes an internationally renowned nature reserve, rich in freshwater and marine flora and fauna. A popular tourist resort, it has great appeal to naturalists and scientists. With the advent of man, development of the catchments of the rivers feeding the lake has disturbed the delicate balance between the freshwater supply and evaporation losses. To an ever-increasing degree the system has now to rely on salt water from the sea to replace the water lost by evaporation. Consequently, during drought, salinities may rise to several times that of sea water, with dire consequences to the flora and fauna. The work reported in the paper was aimed primarily at establishing the effect of man's activities on the water level and the salinity regimes in the lake and, secondly, at selecting and testing feasible engineering measures aimed at preserving or enhancing the nature reserve environment. No attempt was made, however, to perform a benefit cost analysis of the lake system as a whole.