Shear strength behavior of unsaturated compacted sandy soils

Embankments which carry high-way or rail-way need firm foundations, for that reason they are generally constructed with compacted sandy soils. Generally the saturation conditions of soils of embankment during raining season are more than 70%. However, during heavy rains, the soils become more saturated thereby reducing shear strength and consequently failure occurs. The purpose of this study is to observe the shear strength variation of unsaturated sandy soils with degree of saturation of more than 70%. A series of triaxial shear strength tests conducted on 2 types of sandy soils (taken from Okayama and Hiroshima areas of Japan). In both, 9 specimens of each type of soils were considered for undrained triaxial tests with pore-water pressure measurement. The specimens were prepared by static compaction with different initial degree of saturation ranging from 70% to 100% but with the same void ratio for each soil type (0.61 and 0.65). The chosen void ratio gives around 90% proctor compaction. Experimental results show that, the shear strength decreases linearly with increase in degree of saturation.