Abstract
There are more than 100 shotcrete slopes at a alternation strata of sandstone and mudstone along with about a 32km section of National Route 220 from Miyazaki to Nitinan city. Because most of them were built in 1966 to 1974 and are beyond 20 years old, some of them have been deteriorated these years. Several slope disasters, therefore, occur every year in the case of heavy rainfall. So under the abnormal weather, the section of the road is to be closed to traffic. And it is the longest section of traffic regulation in Kyushu. In order to keep the shotcrete slopes in the traffic regulation section under perfect control, the causes of shotcrete slope collapse, the decision of priority order for the restoration of deteriorated shotcrete slopes, the manual for restoration methods and the trial construction for the restoration of deteriorated slopes have been carried out since 1992. This paper shows the slope maintenance system and the guide manual for design of restoring shotcrete slopes under consideration.
