Investigating the causes of the Bochum-Wattenscheid subsidence incident of 2~(nd) and 3~(rd) January 2000

摘要

On 2~(nd) January 2000, at about 9.00 a.m., a subsidence incident occurred in a housing estate in the Bochum district of Wattenscheid-Hontrop. The ensuing crater quickly increased in size and ultimately measured 12 to 15 m in width by 20 m in depth. At around 3.00 a.m. the following morning a second cavity, which measured 12 to 17 m in width and 15 m in depth, appeared a few metres east of the first. This complex case of surface subsidence was caused by a collapse in Shaft IV at the old Maria Anna/Steinbank mine at a shaft depth of between 35 and 52 m; the debris from the collapse had dropped to the bottom of the shaft and as a result a cavitation developed in the strata close to the shaft column which extended from the affected shaft section up to the surface. Other factors either not related to mining or not demonstrably proven as being associated with mining could have had an effect on the incident, but were ruled out as being the actual cause of the subsidence. The incident itself constituted an unusual situation from a geological, tectonic, hydrological and mining-related point of view, when compared with other abandoned mine sites, and was caused by an accumulation of factors which had produced a negative effect on ground stability in and around the shaft column.