Influence of allophane content on engineering properties of volcanic soils

Volcanic soils show many abnormal characteristics in engineering properties. High natural water content, change in consistency limit with initial water content, different behaviors for the disturbed and undisturbed states, and irreversibility in compaction curve are some of them. Young volcanic soils contain many amorphous clay minerals. The abnormal behaviors are supposed to originate from the allophane behavior. Therefore, all the engineering properties were investigated as function of allophane content in this study. The main results obtained are summarized as follows. (1) The natural water content, liquid limit and permeability increased linearly with increasing allophane content, while the residual strength decreased. (2) The degree of deviation in compaction curve for the sample by drying process from that by wetting process depended on the allophane content. (3) The dispersive effect by acid became more effective than that by alkali when the allophane content increased.