Geomechanical analysis of subsidence-induced sinkholes and drempels from longwall coal mining using the material point method: A case study from South-Limburg, the Netherlands

Abstract

Subsidence-induced surface instabilities, such as vertical sharp steps in the topography (known as ‘drempels’ in Dutch), subsidence, and sinkholes, can severely impact infrastructure and public safety. These surface displacements features have been observed during and immediately after coal mining in the South Limburg province of the Netherlands. In this study, a numerical framework for modelling large deformation processes, namely the material point method (MPM), is applied to investigate the underlying mechanisms driving the formation of these complex surface features during coal seam excavation. The modelling of this study focuses on a case study from Heerlen, South Limburg, where a shopping centre in the ’t Loon area partially collapsed due to the development of a sinkhole. Different seam configurations and excavation procedures are tested to assess their influence on the magnitude and spatial distribution of ground deformation. The MPM simulations demonstrate a clear connection between the observed deformation patterns and the early longwall mining processes. Modelled stress and strain concentrations coincide with the observed locations of both drempels and the sinkhole at the ground surface. Furthermore, additional insights were obtained. For example, the direction of seam excavation was found to contribute significantly to the overall distribution of deformations, with larger deformations occurring near the starting position and decreasing towards the end excavation. In contrast, reducing the seam dip angle further amplified the deformations, regardless of the excavation direction, with horizontal seams producing more pronounced effects. These behaviours arise in the absence of geological heterogeneities, indicating that operational configuration alone can predispose sites to the development of surface anomalies. This set of results demonstrates that specific mining and excavation configurations can trigger distinct surface deformation features at predictable locations. The study highlights the potential of MPM to capture the complex mechanisms driving mine collapse and ground subsidence, offering both improved understanding and a means to identify vulnerable areas for post-mining geohazard assessment based on subsurface configurations.