Hydraulic Conductivity and Coefficient of Consolidation of Two Sulphide Clays in Sweden

The variation and anisotropy in hydraulic conductivity and the coefficient of consolidation was investigated for two Swedish sulphide clays. A series of constant rate of strain oedometer tests was performed on samples trimmed in the vertical and horizontal direction. A methodology to evaluate the horizontal coefficients of consolidation c(h) via the horizontal hydraulic conductivity k(h) and the vertical compression modulus M-v is proposed. Laboratory evaluations of ch are also compared with determinations of ch from in situ piezometer measurements in vertically drained sulphide clay. Furthermore, the validity of the empirical correlation between hydraulic conductivity change index C-k and initial void ratio e(0), Ck = 0.5e(0) (Tavenas et al. in Can Geotech J 20( 4): 645-660, 1983b), was investigated for the sulphide clays. The results from the investigation show large ranges in measured hydraulic conductivities and coefficients of consolidation. However, the results indicate that the correlation C-k = 0.5e(0) is valid. The anisotropy in hydraulic conductivity and the coefficient of consolidation of the sulphide clays tested seems to be small. For design purposes, multiple tests for assessment of hydraulic conductivity and the coefficient of consolidation should be made, and a partial factor of safety, depending on the requisite level of safety and the spatial variability of the parameters, should be introduced. For design purposes in this type of clay, k(h) = k(v) and c(h) = c(v) are suggested.