Underground Infrastructure Rooms in Squeezing Rock & ndash; Geotechnical Conditions in the Konrad Mine during the Conversion to a Repository for Radioactive Waste

The Konrad mine is a former iron ore mine near Salzgitter in Lower Saxony, Germany. The mine will be modified to a repository for low and intermediate level radioactive waste in the next few years. The bedrock is characterized by complex geology. In particular, the "Fladentonsteinserie" (a specific type of mudstone) shows squeezing behavior. Since the necessary geomechanical parameters cannot be determined completely and reliably, the observation method should be applied for the proof of stability and usability. The underground support system consists of a slotted lining with sliding anchors in the areas where squeezing rock is present. This allows converging of the bedrock. During the convergence period a bearing ring is formed within the rock mass. Afterwards the final lining is created in reinforced shotcrete. Dimensioning of the liner is made possible only by using this concept of construction.