Probability distributions of geotechnical properties for heterogeneous lignite mine spoils

<p><span>During surface coal mining, vast amounts of overburden waste materials, called spoils, are excavated and dumped, forming massive heaps. The sustainable exploitation of these vast areas is a top priority globally. However, the proper understanding and geotechnical characterization of spoils, being extremely heterogeneous soil masses, has not been achieved. Few works exist on the geotechnical characterization of spoils and none on the probability distributions of their properties. This work conducts advanced statistical characterization of lignite mine spoil materials from a massive heap in Greece. The geotechnical properties were analyzed to determine the appropriate probability distribution. Five distributions - normal, lognormal, Weibull with 2 and 3 parameters, and Gamma - were compared considering the considerable heterogeneity, uncertainty, and limited knowledge of spoils’ materials parameters. The lognormal and Weibull distributions best fit most geotechnical parameters except cohesion, which has an uncommon distribution, with several samples having very low or zero cohesion. For some parameters, the normal distribution can also be used instead of the Weibull for a simplified analysis. The conclusions can be implemented to analyze spoil materials as advanced numerical and stochastic tools seem the only way for a robust geotechnical design.</span></p>