Certain factors made the Mhlahlane viaduct project a success. These factors are identified and discussed in general. The presence of these particular factors on above-mentioned project are lIIustrated with examples. In particular, the unique method used for stripping and erecting the arch centring is discussed in detail.
The construction of this multi-mlilion rand project, funded by the National Transport Commission, was completed in May 1987 after three years duringwhich exceptional technical and practice skills and flair were required to cope with the unforeseen geotechnical, ecological and landscaping problems that arose during the course of the construction period. The combined effort of the project management team and the special advisers in the structural, geotechnical, ecological and landscape architectural fields resulted in the successful completion of this prestigious and controversial project. For their joint efforts, the resident engineer and the project manager were awarded the Basil Read Award (Bronze) for 1986.
During the construction of a section of National Route N13 (Johannesburg Southern Bypass) two large cuttings ware excavated. The first, in andesite lava, was adjacent to a Rand Water Board pipeline and the second, In quartzites, adjoined private dwellings. The cuttings were restrained with stressed anchors and unstressed dowels and the exposed faces were protected by concrete panels. The geotechnical design of the lateral support In the andesite was problematic, owing to the unpredictable variations In rock weathering. By contrast, the quartzite cutting was uniformly weathered, with consistent patterns of jointing, and design problems were concerned mainly with the overlying transported soil.
Vibratory equipment and material factors play an important role in effective compaction. After a discussion of the basic factors affecting vibratory compaction, a practical guide to facilitate the selection and use of such equipment is given.