Assessing hydraulic conductivities of a compacted dam core using geostatistical analysis of construction control data

The surveillance of a 94.5 m high embankment dam in northern Quebec, Canada, revealed the possibility of the existence of a zone of higher hydraulic conductivity in its till core. The spatial continuity of the measured fines content in the dam during construction was computed by geostatistical means to predict values at unsampled locations for the entire core volume. The hydraulic conductivities were inferred using the predicted fines content and in situ compaction conditions. The inferred hydraulic conductivities and their spatial representations were supported by thermal and seepage field monitoring data. This provided the necessary background information to interpret the surveillance data and determine the cause of the presence of a more pervious zone in the core, which was related to spatial variability of the fines content of the till, placement water content, and compaction procedures. The geostatistical approach complemented with laboratory and construction control data is an efficient tool to characterize dam heterogeneities permitting location of zones of more intensive seepage.