Modelling of the unsaturated cover of liquefiable Lusatian inner overburden dumps

摘要

Due to gravitational mass movements, large areas of former Lusatian opencast pits are currently closed. A conceptual model was developed to describe the processes following liquefaction of the sandy inner overburden dumps in which the dump profile is represented as a saturated, liquefiable groundwater zone as well as an unsaturated, arable cover zone with a horizontal surface and a homogeneous granular structure. Interactions between the zones were analysed with a focus on geohydraulic state parameters and were characterised by three main processes. Due to the resolidification of the liquefied quicksand, a water lamella can form below the unsaturated cover zone. Based on HYDRUS-1D simulations, a numerical approach was developed for the subsequent transient saturation of the cover, which treats the saturation front as an advancing stable macroscopic interface. The temporary appearance of the liquefied quicksand and the water lamella reduces stability of the inner overburden dump. In the next step, the model needs to be experimentally validated, adapted and expanded.