Interburden Collapse Evaluation
Understanding complex stress scenarios.
RESPEC evaluated an incident where a vehicle punched through an unexpectedly thin interburden sill that separates two mine levels. The interburden thickness, which is typically close to 20 feet, was only slightly greater than 10 feet in an isolated area of the mine, based on observations from drillholes that were scoped between the two levels. Roof failure had propagated above an abandoned entry to the point where the remaining sill thickness was only 1 to 2 feet thick, which resulted in a localized floor collapse. RESPEC reviewed the mine design plans and available geological information and determined that the increased risk of collapse was localized to one panel. Recommendations were made to avoid a limited area of one panel where additional interburden failure was considered most likely. Adjacent panels were not impacted. RESPEC’s recommendations for avoiding a small area of the reserves were implemented, and no additional interburden failures were encountered.