Design of Anchors in Weathered Greywacke – A Case Study in Wellington

The variability in weathering conditions of Wellington greywacke whether among different sites or within the same site makes anchor design challenging for geotechnical engineers. Sacrificial ground anchors tests were analysed from 16 different projects located within the Wellington region. A correlation between the rock weathering grades and the bond capacities inferred from the anchors tests, and comparison with relative published data/research are presented in this paper. This correlation could be used as preliminary presumptive value to design the anchors. Quality logging of the target founding strata at the appropriate depth and understanding of the geological model is required to be able to utilise the correlation. Sacrificial anchor testing is recommended as the design progresses. A case study is also included to demonstrate a possible approach in designing anchors in such variable conditions.