Survey regarding the transformation and design of Kamikami-horisawa improved wire net dam

Abstract

In the past, several wire rope net dams were developed and installed, however eventually these dams broke. Based on this technology, various important improvements have been made and finally the development of a new ring net dam could be achieved. In the month of August 2002, the first ring net dam was completed at Mt. Yake Kamikamihorisawa. On July 18 th 2004, a stony debris flow hit this ring net dam. The dam was able to capture this heavy debris flow impact without major damages. The event of impact and debris capture was recorded by video. The biggest boulder diameters and the dam's deflection and transformation were analyzed in the survey. The actual mechanical behavior and function of the dam were compared with design values and measured values, e.g. by means of load cell data. Based on these experiences, it was found additionally that sediment removal can be executed safely and promptly by adopting the lancer stick. There is considerable validity to this dam's design method from these results, but of course, this new technology shall only be applied carefully. This paper reports about the above mentioned project and describes the improvement concept for future installations.