Sinkhole formation above underground limestone quarries: A case study in South Limburg (Belgium)

Historical records were used for the compilation of a database of sinkholes resulted from collapses of abandoned shallow underground limestone quarries (mines) in two villages in Belgian South Limburg. During the last 350 years the formation of such sinkholes caused at least 38 casualties, but more often it caused a change in topography and damage to public and private property. The objective of this study is to better understand the spatial and temporal patterns of quarry collapse-related sinkholes in the study area. Apart from sinkhole locations and ages, the compiled database provides information on the dimensions of the area affected and the damage caused by sinkhole formation, as well as the causal factors of sinkholes. One hundred seventy-three sinkholes have been reported since 1665, but most (80%) reported sinkholes postdate 1965. Sinkhole dimensions provided information on the type of collapse. Seven large sinkholes, displacing a total sediment volume of 480,000 m3, resulted from large-scale roof breakdown after pillar failure. The smaller sinkholes were the result of fall of the overburden into galleries after local roof collapse or suffosion of a solution pipe. In total, these small sinkholes displaced 12,300 m3 of sediment. At present almost all large underground quarries in the study area have been affected by sinkholes. These features were caused by natural and anthropogenic factors, and occur in zones with thin roofs, where pillars were affected by pillar robbing, or on locations with inappropriate sewerage systems above quarries. The formation of sinkholes was often reported in spring during years with high moisture contents in the overburden, caused by high groundwater recharge or above average precipitation. With increasing time since quarry abandonment, quarries become more susceptible to pillar creep and bending of the roof. Hence, if no appropriate mitigation measures are taken to reduce such deterioration processes, the number of sinkholes is expected to increase. © 2007 Elsevier B.V. All rights reserved.status: publishe