Support design and construction results for general parts and intersections of deep shafts

Nagata, Shohei*; Ichida, Toshiyuki*; Fujieda, Daigo; Aoyagi, Kazuhei  

We performed three-dimensional excavation analysis of three shafts and intersection of horizontal tunnel excavated to 500 m depth at Horonobe URL, and evaluated stress acting on concrete lining under various conditions such as differences in diameter of shafts, lining shape, lining thickness, concrete strength, and installation interval of the lining. The design of the support was determined based on the analysis results, and then the construction of the shafts and horizontal galleries were started. Considering the measured stress acting on the concrete lining of the shaft and sprayed mortar installed at the intersection of shaft and horizontal gallery, we could successfully excavate the shaft to 500 m depth and intersection of horizontal gallery at 420 m depth. We also concluded that appropriate support pattern can be selected based on the measured stress acting on the concrete lining and numerical analysis performed prior to the excavation. This can contribute to enhance the reliability of the appropriate observational construction technology targeting excavation of shaft.