The shear strength characteristics of compacted soil one of the fundamental problems in airport consturction.
　The purpose of this study is to evaluate mechanical properties of compacted soils. Compaction test, unconfined compression test and triaxialcompression test on volcanic cohesive soils are carried out.
　The results are summarized as follows;
　1)The Strength characteristics of compacted soils depend on thedegree of saturation.
　2)When the water content is larger than the optimum moisture content, the strength of compacted soils decrease drastically.
　3)The strength of natural deposit ground is greater than the strength of bank under submergence condition.
　4) Even if the specimens are compacted to the same dry density, the stength characteristics are clearly defferent depending on the moisture content; the strength of dry side of optimum moisture content is greater than that of wet side.