Clay samples were collected in Tokushima prefecture at the three landslide areas, Morito landslide existing in pelitic schist of Kashidaira formation and Mikabu green rock, Zentoku and Handaira landslide in pelitic schist of Koboke formation. The experimental method was the same as that in the previous report. The results are as follows; 1) The graysh green clay from Morito landslide area was composed of chlorite and Montmorillonite, and illite was not contained. Illite was usually found out in Sambagawa zone landslide but the clay collected from Morito area did not contain the illite, because from the clay mineralogical point of view, Morito landslide can be considered Mikabu zone. Vermiculite was contained in the surface layer with humus. 2) There were vermiculite and illite in the surface soil of Zentoku landslide area, but kaolinite and montmorillonite were not found. Montmorillonite was contained in the fault clay, which was in border between green schist and silliceous schist. 3) Only illite existed in the clay from Handaira landslide. A weathered rock was composed of a large quantity of illite and a small quantity of 14 Å minerals.
A great number of drifting woods, which occur and run off at heavy rains, should be checked at the suitable place of the upper reaches of river, in connection with blockade problem caused by them at the lower reaches. There are some methods to check the drifting woods, in which the stockade for drifting woods is worth investigating. In this paper we introduce some methods and then describe the results of some measurements on the moving form the group of drifting wood which approach to the stockade, as the first stage of a series of study on the check of drifting woods.
In this paper, flow resistance of debris bed having wide size distribution is studied. Basic equation of flow resistance is deduced from assumption that shearing stress of bed is balanced with drag force of roughness elements, and numerical bed profiles are simulated assuming log-normal size-distribution of bed material and using random numbers generated by computer. To clearify the relation between flow resistance and size-distribution, numerical experiments are made by use of the basic equation and numerical bed profiles. It becomes obvious from the numerical experiments that diameter corresponding to 70% of distribution curve, d70, is appricable as a representative diameter of bed debris, and relative roughness height, ks, is equal to 3d70 independently with standard deviation of the bed material size. As a result, new practical roughness formula is offered, and it shows good agreement with flume data.