Reliability-based assessment of compacted lateritic soil liners

The first-order reliability method is employed to assess the suitability of lateritic soils as landfill liner materials based on existing models developed from laboratory and field data. The statistical characteristics of lateritic soil properties were first compared with those from which the regression models were developed. Using regression models for hydraulic conductivity, k, and established distributions for the relevant soil parameters, reliability indices are computed considering hydraulic conductivity to have a normal/log-normal distribution. The results indicate that, for the laboratory-based model, reliability index is sensitive to variability in compactive effort and initial degree of saturation. The choice of distribution of initial degree of saturation affects reliability indices significantly and the energy of the British Standard heavy compaction has the highest reliability indices. On the basis of the reliability indices estimated from the field-based model, three variables, namely: compactor weight, initial saturation and plasticity index are identified as significantly affecting the field geometric mean hydraulic conductivity of lateritic soils. However, the hydraulic conductivity of lateritic soils can be better predicted if the compactor weight, as the most significant parameter, can be modelled as Gumbel-type distribution.