Journal of the Japan Society of Erosion Control Engineering

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There are many studies of the mechanics of suspended load laden flow, and many theoretical formula to estimate the concentration of suspended load have been proposed so far. But all has common problems;
(1) The relation between the characteristics of the turbulence of flow and the behaviour of suspended load is not so much reflected on the formula.
(2) It's necessary to know a reference concentration at a reference level to evaluate the formula. The reference level has not been set up theoretically.
And there are few studies of the suspended load on the torrential bed condition, in comparison with that on the alluvial bed condition.
This study was made by using a steep channel with large roughness on its bed. The results were analyzed using the diffusion model in order to check the suitability. The results are;
(1) The similarity between the dispersion of suspended load and the momentum transfer of flow was not always shown.
(2) The concentration distribution below roughness height decrease with decreasing height in some cases.
(3) It's more reasonable that the reference level is set up at the point with the roughness height from the theoretical bed.
In order to figure out mechanics of suspended load laden flow, especially on the torrential bed condition, the structure of the turbulence of the flow, the behaviour of suspended load near the bed and the behaviour of suspended load there should be studied.

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Analysis of slope stability requires to assess a distribution of shear strength in the subsurface layer. In general, the depth of shallow landslide is range in 1 to 2 m from the surface, therefore it is important to make clear the property of shear strength at low confining stress. A series of direct shear test has been performed in order to examine the relationship between normal stress and shear strength at normal stress below 0.2 kgf/cm².
The experimental evidence clearly shows that the failure envelope is curved for six types of soils, and the extrapolation by empirical Coulomb straight line is not suitable under this stress range. That is, the shear strength sharply decreases at normal stress below 0.1 kfg/cm². Based on these results, we employ the nonlinear equation which the shear strength of soil is proportion to the powered normal stress in this paper.

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Procedures for predicting areas prone to mudflow and pyroclastic flows are studied for developing countries. Fundamental information for hazard map making is obtained through satellite image data. Pyroclastic flow is simulated by two directional calculation and flooding sections of mudflow are predicted by one dimensional method. These methods are applied to Mount Marapi in Indonesia. Caluculated results show a good correlation with the actual situations.

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