The earth slope, natural or artificial, very frequently loses its stability in the course of time, resulting in failure or slippage. In this case, every deterioration of the slope is induced by nothing other than natural alternation of the soil forming the slope. The authors have paid close attention to the exchangeable ions contained in the soil and to the effect of groundwater on the soil at the site. Chemical analysis shows that the soil forming unstable slope is partly saturated with

more »

... ions or magnesium ions in natural state, and that the artificial soil which is supplied with divalent ions to saturation exceeds the original soil in natural state in shearing strength. We have thus reached a conclusion that the stability of the slope was upset through loss of divalent ions out of the slope soil by seepage water.