About the simplification of the triaxial compression test apparatus for unsaturated soils and the shear strength of unsaturated soil measured by the apparatus

摘要

In this study, a practical test apparatus was developed, which can be used for triaxial compression tests of unsaturated soils, by using 2 common triaxial cells for saturated soils and improving their top cap and pedestal. It was shown that shear properties can be discussed with this device by running a variety of accuracy examinations on the developed test apparatus, which is only a slightly improved common triaxial test apparatus. Furthermore, by using compacted weathered granite soil at low lateral pressure conditions, a drained shear test at constant suction was executed with this apparatus. Thereafter, measured shear strengths were compared to shear strengths obtained from the estimation approach proposed by ?berg and S?llfors. From the results of the comparison under these conditions, the following knowledge could be obtained.1)Shear strength estimations obtained from the approach proposed by ?berg and S?llfors result in lower shear strength than the values obtained from the test apparatus. The difference is attributed two factors. One of them is the difference of contributions to shear strengh by dilatancy, which depends on suction changes. The other is the difference of cohesions between unsaturated condition at suction “0” in wetting process and saturated condition.2)The effect of the difference between estimated shear strengths of the conventional method and the measured shear strengths of the test apparatus on slope stability analyses of embankments in wetting process may not be neglected.