2022 – Extension Strains in Embankment Dams and the Potential for Development of Transverse Cracks

Cameron Purss – GHD, Melbourne and Gavan Hunter – Hunter Geotechnical, Melbourne

There are many factors that can influence the development of transverse cracks in embankment dams. The focus of this research was to further understand the influence valley shape has on crack development, this being identified as a significant contributor.

This research investigated the potential correlation between average extension strains measured from surface survey markers and strain localisation by reviewing data from dams with closely spaced survey markers and with extensometer instruments. The results of the research indicate a potential correlation between extension strains averaged over a length of 50 m to peak extension strains in the upper portions of embankments.

Linkages were investigated between post-construction settlement, valley shape and extension strains with the relationships developed exhibiting reasonable consistency with numerical analyses of the case study dams. Comparisons were also made with case studies of cracked dams to estimate the strains at which transverse cracks may develop. Predicted extension strains to induce cracking were found to be generally higher than the capacities of soils tested in the laboratory.

The research indicates that common industry practices for assessing the development of extension strains on abutments of dams typically underestimates peak strains due to the averaging effect of surface survey markers. In the absence of detailed finite element studies, the outcomes of the research are considered applicable in assessing the performance of embankment dams and for use in predicting the potential for development of cracks in dams as part of dam safety risk assessments.

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