Soil management using lignite to improve soil cracking properties and performance

Incorporating Victorian brown coal (VBC) into the soil as a reliable amendment can markedly alter the hydraulic properties of the soil. A pivotal phenomenon influencing soil hydraulic parameters, particularly the soil permeability coefficient, is the extent of cracking and shrinkage observed during the drying process and consequent moisture loss. This study investigates the impact of incorporating VBC into clay and its influence on the two-dimensional cracking and shrinkage characteristics of the mixture. Various mixtures of brown coal from Latrobe valley in Victoria, Australia and clay, ranging from 2% to 20% brown coal content, were prepared and subjected to liquid limit and plastic limit tests. The samples were then readied for cracking and shrinkage assessments under liquid limit moisture conditions as an initial moisture content, featuring a sample diameter of 150 mm and a thickness of 10 mm. Results from the liquid limit tests demonstrated a decreasing trend in the liquid limit of the mixture with increasing brown coal content, registering values of 38.3%, 37.4%, 36.5%, 34.9%, and 32.9% for 0%, 2%, 5%, 10%, and 20% brown coal mixtures, respectively. Plastic limit tests indicated a 1.7% reduction, decreasing from 20.6% to 18%.9, with the addition of 20% brown coal. Furthermore, cracking and shrinkage tests revealed a substantial reduction in the cracking index (cracking intensity factor, CIF) of the mixture upon the addition of brown coal, reaching zero for mixtures containing 5%, 10%, and 20% brown coal after exposure to a 45℃ temperature for 30 hours. Additionally, the shrinkage index (shrinkage intensity factor, SIF) decreased from 15.4% for the clay soil sample to 14.9%, 14.6%, 13.9%, and 13.1% for the 2%, 5%, 10%, and 20% brown coal mixtures, respectively. This underscores the positive influence of brown coal on mitigating soil cracking and shrinkage, emphasizing its significance in soil science research.