2019 Volume 19 Issue 6 Pages 6_1-6_15
Residential ground located at the inclined area had severe damage during the 2016 Kumamoto earthquake. This paper reports test results obtained from the undrained cyclic shear test using volcanic clayey soils sampled from Mashiki Town damaged sites for clarifying the deformation mechanism of the residential ground. In the tests, specimens were consolidated by confining pressure at the sampling depth, after applying the initial shear stress corresponding to inclination, the random seismic shear stress, which was estimated from actual seismic records obtained at the Mashiki Town, was applied to the specimen. As a result, it was shown that even unsaturated volcanic clayey soil, excess pore water pressure ratio was generated up to 0.9 and deformed over 15% shear strain. Furthermore, a large shear strain was developed to the inclined direction in case of initial shear stress applied test. Therefore, it is considered that, during the 2016 Kumamoto earthquake, residential ground damage was caused by large shear deformation of volcanic clayey soil subjected to large shear stress.
