山くずれの実験的研究 (第1報)

Abstract

This is the report on the model experimcnt of landelide, which was carried out by the action of artificial ground water pressure. The experimental flume had 300cm length, 30cm width and 60 cm height, and it was fixed at 30°gradient to the horizon. The model slope in this flume consisted of two layers, the upper one was clay loam layer of about 30cm thickness and the lower one was sand layer of about 5cm thickness. Since the lower layer was contracted on the halfway, the supplied water in this layer posesed high hydraulic pressure in the adjacent region of contracting point. Then the neutral stress in the soil layer arose for this high pressure coused the reduce of shearing resistance, and the typieal model landslide occured. We measured the slope surface displacement, the hydraulic pressure variation and the general movement of soil in the course of landslide. The following conclusions were gained for the consideration of experimental data. 1 Model landslides ocurred for some arranged conditions, which were the uniform and medium density of soil layes, and suitably high hydranlic pressure. 2 In the course of ladslide ocurrance, the rupture of soil layer emerged ahead of the ground water abrupt efflux. It was certained of the belated pore pressure decreace after the abrupt movement of soil by means of the landslide ocurranee. (Fig. 6) 3 The emergence of landslide was judged most distinctly by the change of the distribution of surface deformation. Althogh the longitudinal defomation of any points on the slope surface for the stable state distributed symmetrically with the midst of the sliding mass, when the landslide started, the movement of lower portion increaced suddenly, and the distribution diagram changedto the type of simply inereacing as the distance from the upmost point. (Fig. 7, 8, 9) 4 This emergence was detected similarly with the change of moving velocity of any point. Still the phenomena had not so much evidence than the former, but the observation of it may served for the practieal method for the forecasting means of the landslide ocurrance. (Fig. 10) 5 The rupture of stable state started at the same time in almost whole portion of the boundary surface of sliding mass. The emergence of tension crack at the upper region of soil layer was not ahead of the wholly regional disintegration.