Grouting of dispersive dam foundations

Abstract

Dispersive soils, their occurrence, identification and their judicious utilization for embankment dams and other applications have become part of the geotechnical “toolbox” of contractors and consulting engineers alike. Southern Africa has its fair share of dispersive soils and much research has been done during recent decades to improve the identification process and to develop adequate preventive and remedial techniques. Early identification and the introduction of appropriate elements at design stage have gone a long way to solve or prevent potential problems with dispersive soils. South African geotechnical engineers and contractors are sensitized to potential problems associated with these soils. Most research has focused on potential embankment problems resulting from the use of dispersive materials. Practically no publications are available in the field of grouting of foundations, which are dispersive. The authors endeavour to present the most important aspects of dispersivity as they relate to foundation engineering with special reference to dam foundations. Little or no experience is available where dams have been founded on dispersive soils; the precautions and controls with respect to dispersive foundations during construction and during operation is the subject of this paper. An important and interesting case study is used to illustrate the typical problems with dispersive residual granites used as foundation for a dam.