Partial Collapse of a Subterranean Building


The Missouri River Valley is home to a number of limestone mines that have been repurposed as subterranean buildings after the useful rock has been removed. These former room and pillar mines present ready-made spaces with low humidity and comfortable temperatures that are ideal for industrial and commercial purposes. Although these structures are often quite stable, issues and deterioration can arise much like in any building.

CTLGroup was called upon in the aftermath of a partial collapse of a portion of a repurposed room-and-pillar mine that served as a library at a university campus in Missouri. Fortunately, the collapse took place when school was not in session. The incident involved a “dome out” where the rock strata forming the roof or dome over a room in the former mine fractured and collapsed. The event occurred after a period of significant heavy rainfall in the region, which was believed to be a contributing factor.

CTLGroup was engaged by the university through their insurance recovery counsel and worked with the university’s insurance consultant preparing and certifying the property loss claim. Our role was to evaluate the nature and extent of damage, investigate the cause of the dome out collapse, and assess the university’s maintenance policy and practices for the repurposed mine.

Our work included field inspection of the collapse area. To avoid exposing the inspecting engineers to the risk of a secondary collapse, we deployed a small unmanned aerial vehicle, or drone, which was flown inside the collapse area to video- and photo-document the surrounding rock strata. We also obtained rock from the margins of the collapse region for laboratory analysis. The purpose of our analysis was to evaluate mechanical and material properties of the limestone that composed the roof that failed, as well as the shale formation above it. Samples were also tested to assess their durability and the effect of moisture exposure. Our investigation included interviews with the facilities engineering staff and review of historical inspection and maintenance activities to assess whether the incident could have been avoided. Throughout the investigation process, CTLGroup served as technical sounding board and advisors to the university and their counsel in their insurance recovery efforts.

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