Die Ingenieursgeologie van sandsteen in die Natal groep

Abstract

Sandstone of the Natal Group occurs in the form of a narrow strip along the south-eastern coast of South Africa. The maximum east-west width is approximately 70 kilometres and the length from north to south approximately 380 kilometres. The Natal sandstone is disconformably underlain by gneiss and granulite of the Mmapumulo Complex and disconformably overlain by tillite of the Karoo Sequence. The Natal Group can, from botton to top, be subdivided into the Eshowe, Mkunya, Mlazi, Inanda and Hibberdene Formations. Rock material properties including strength, deformability, durability and physical properties were investigated. In the unweathered condition the sandstone classifies high to very high-quality material as for all the above-mentioned properties and with the exception of approximately five percent of the material which classifies as a shale, it can be termed a quartzite or feldpathical quartzite. The sandstone was also investigated for all aggregate and a number of road building properties and it was found that the unweathered rock is suitable for concrete aggregate and road building materials. Discontinuities in the rock mass are mainly sub horizontal bedding planes and sub vertical joints giving rise to a blocky appearance of the rock mass. Rock mass properties such as deformability, stability, permeability and rippability as well as properties of the residual materials were also investigated. This study concludes that Natal sandstone in both the weathered to completely weathered {residual) condition is a very useful, strong and stable engineering material with which and in which structures can be built without problem