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Tzaneen dam raising – Geotechnical investigation by Coert van Dyk

A field investigation was conducted for the proposed raising of Tzaneen Dam, a composite earth fill embankment dam. This paper describes the part of the investigation that focused on the inclined clay core of the dam. The sensitive nature of the clay core did not permit conventional rotary core drilling to be employed as this could potentially cause hydraulic fracturing of the core resulting in leaking, internal erosion and ultimately failure of the dam. The geometry of the embankment and inclined configuration of the clay core also added to the difficulty in obtaining info relating to the impervious material. A methodology comprising continuous SPTs and shelby sampling was developed. The majority of the shelby samples had to be hammered in, which raised concerns on the quality of samples obtained. However, good material recovery was achieved and the strength parameters obtained from 10 triaxial tests correlated well with typical strength parameters from literature