Statistical analysis of pond ash–bentonite mixtures: implications for liner and cover material design

This study investigates the potential use of pond ash (PA) mixed with varying proportions of bentonite (Bt) (10, 20 or 30%) as a landfill liner and cover material. The laboratory test study covers Atterberg limits, compaction, hydraulic conductivity ( k ) and unconfined compressive strength ( q u ) tests. The test results were analysed using the probabilistic approach to account for uncertainty. While evaluating the PA–Bt mixtures under liner and cover placement conditions, significant variability was observed in the hydraulic conductivity ( k ) and unconfined compressive strength ( q u ), with sample coefficients of variation of 197 and 94%, respectively. To better understand and quantify the variability, the probability density function for k and q u was identified as a log-normal distribution. The inferential statistical analysis limits k and q u standard deviations to 0.66 and 0.17 (key parameters for informed decision-making), respectively. Hypothesis testing was then conducted to assess the suitability of compacted PA–Bt mixtures based on the desired and characteristic values of liner and cover materials. This probabilistic approach allows a more flexible evaluation of placement conditions than deterministic methods, ensuring more reliable performance. Addressing material variability of PA–Bt mixtures allows cost-effective design by exploiting the most probable outcomes.