Recently, landslides to form the landslide dam and to show the long runout distance more than double of landslide length are observed by a large scale of earthquake. The long runout distance landslides to move bring the damage of the large scale for human life and social activity because of their widely spread flow down and the accumulated soil. The analysis of the landslide phenomena to make long runout distance movement must analyze the advection equation showing high moving velocity of landslide mass, however the landslide at early stage is in block and then landslide become the crushed flow according to travel to flow down afterwards. Therefore, we examine analytical method to predict the runout distance area of the landslide earth mass in consideration of a condition of the crushed fluidity by the Mohr-Coulomb theory criteria. We show the analytical precision and high utility of the presented method in comparison with model analysis and long runout distance of actual landslide.

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  The diffusion laser beam (DBL) displacement meter is a non-contact extensometer that is mainly used to measure ground deformation in the field. It employs laser beam of larger diameter and larger cone angle than usual to improve measurement performance under rainy or foggy condition without increasing laser power and to avoid harmful effects on the eyes, skin, etc. Refining the internal structure of the conventional twin-lens DBL sensor that was previously developed by the authors, this study has developed a new single-lens model. The single-lens model has fewer number of parts and wider range of available laser reflection intensity than the conventional twin-lens models. This paper conducted measurement performance test using the indoor rainfall simulator. The test result showed that a single-lens model has as good performance as a conventional twin-lens model. It was able to measure distance without data missing under the rainfall intensity of less than 200mm/hr and 120mm/hr at the baseline length of 30m and 62.5m, respectively.

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