Forecast effect of specimen size on unconfined compression test for soft clay

Abstract

In Vietnam, soft clay soils commonly distributing in large plains are used as the different construction foundation such as road, dike etc. Then there often occurs high settlement deformation, affecting the stability of structure. The main reason is that the input soil mechanics still have limitations especially the settlement deformation properties. Particularly, the specimen size of unconfined compression test is not much paid attention. This paper presents the research results on the influence of specimen size on unconfined compression test for soft clay. The soft clay (semi-clay ambQ23tb in liquid state) distributed in the coastal area of Nam Dinh give general comments: In vertical consolidation tests: In both diameter classes (D), when The height (H) increases, the settlement index (Cc) decreases but the decrease is not significant only from 0.037 to 0.011). In both heights, when  increases, Cc increases, the increase is small, only from 0.007 to 0.033. When the sample size increases, the consolidation coefficient of soil Cv increases, the increase of Cv with the increase of H is very significant. Specifically: In both sizes , when H increases, Cv increases similarly, ranging from 84 to 311%. In both sizes H, when the diameter increased from 61.8 to 79.8mm, the Cv at all pressure levels (') increased, the increase was in the range of 12 to 89%. In the radial consolidation test: when  increased from 61,8 to 79,8mm, at all values of ', Cv increased but the increase was not large, only a few %; Ch value increased more than Cv, the increase ranged from 17 to 76%, the ratio Ch/Cv ranged from 2.28 to 2.83.