Abstract
Tumuli, ancient tombs made of compacted earth mounds, were constructed more than 1300 years ago and they have been conserved as historical cultural heritages. However, many of them are severely damaged due to natural exernal forces and human activities. Rainfall induced slope failure is one of important and difficult problems that geotechnical engineering should take care of. In this paper, the failure mechanism of tumulus mounds is evaluated by exemplifying the rainfall induced failure of the Kengoshizuka Tumulus in Japan. The surface of the mound is severely embrittled and has lower density and strength than those of the sub-layer, making the boundary of the layers vulnerable to failure. Rainfall infiltration into the layered mound is estimated by seepage flow analysis and the induced instability is evaluated. The strength parameters of the sliding surface are assessed by in-situ and laboratory tests. The result of the evaluation explains the rainfall induced slope failure in 2012.
