The reinforcement for a precipice of 'Nikko Kegon fall' by anchoring from the inside shaft without surface structure

摘要

In recent it is pointed out that a precipice of "Nikko Kegon fall" became dangerous due to the toppling failure of overhanging part for both the prefectural waterfall viewing platform and chargeable water fall viewing platform. As a countermeasure all works were performed inside the precipice for the sake of safety for tourists. That is why rock anchoring method was chosen without surface structures on the precipice. This construction, finished on April 2001, consists of a horizontal shaft and two vertical shafts in the jointed rock masses. Under these circumstances the severe observational method was needed to keep the safe construction considering long-term stability of the precipice. In this paper, the design concept and construction method of rock anchoring, the observational method and the behavior of precipice of "Nikko Kegon fall" during construction are discussed.