PERMEABILITY AND COMPRESSIBILITY OF MIXED SOIL COMPOSED OF VOLCANIC COHESIVE SOIL AND SHIRASU

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The purpose of this research is to find out suitable soil material as an impervious one. Kuroboku soil for a cohesive soil and Shirasu for a sandy soil were chosen in this subject. The results obtained are as follows.1. In case the mix ratio of Shirasu is below 50%, the mixed soil comes to show physical properties similar to Kuroboku soil ; while when it is above 70%, the mixed one comes to show those similar to Shirasu. The maximum dry density of it shows the high value as the ratio increases.2. The shearing characteristics are subjected to the initial density, confining pressure and crushing of grain. For these factors, the increment of deviator stress is reduced with increasing of strain. As a result of it, values of angle of shearing resistance at the high confining pressure are lower than those at low pressure.3. The mixed soil containing the sand fraction of 65% is the impervious material having the coefficient of permeability of 10^<-6>cm/sec, the cohesion of 0.4 kgf/cm^2 and the angle of internal friction of 25 degree.Judging from these results, the mixed material compacted at the mix ratio of about 60% is considered to be the most suitable impervious material below 0.2 of compression index.