Headrace tunnel Lünersee injection into core ring
Underground Mining Special projects
Due to significant water losses, the almost 60-year-old core ring stretch of the Lünersee headrace tunnel (diameter of 3.05 m) needed in some places to be reinforced by means of injection. To this end, star-shaped holes were sunk in a 1.5-m grid over a section of about 100 m. In order to penetrate the approx. 50-cm-thick, heavily reinforced wall ring level, core holes were drilled first to allow the injection star to be sunk to a depth of approx. 2 m by means of hammer drilling.
This special project was particularly characterised by the extremely short preparation time of just a few days, the tight time window during the closure of the Lünersee pumped-storage plant and the difficulty of access via cable cars and on foot.