Consolidation Behavior of Soft Soil with Different Sample Sizes—A Case Study of Preloading Without PVD in Ho Chi Minh City

Abstract

In the soil investigations, the consolidation test results play an important role in the foundation design, especially in the soft soil improvement by preloading method. Nowadays, there are many kind of consolidation test apparatus with many samples size, needed to assess experimental results from various sample size. In this paper, in order to analyse the effect of sample size on soil’s deformation characteristic, several tests on soil samples have been conducted in which the sample size varied within the range of 20, 30, 50 (cm²) in the cross-sectional area; and 2, 3, 4 (cm) in the thickness. Based on the experimental results, when increasing of sample’s area then the coefficient of volumetric compressibility (m_v) tended to increase, the coefficient of vertical consolidation (C_v) tended to decrease and the coefficient of secondary compression (C_α) vary without tended. And when increasing of sample’s thickness, the opposite results is obtained but the coefficient of secondary compression tended to increase. Moreover, these consolidation test results of each sample size were used as input parameters for calculated the consolidation settlement of soft ground due to surcharges preloading by Terzaghi’s theory and PLAXIS 2D software. On the other hand, the field monitoring data from five observation points in district 7, Ho Chi Minh city are used to confirm the accuracy of settlement which are estimated by the mentioned above test results. Based on these comparison, the smallest sample size 20 cm² * 2 cm (cross-sectional area * thickness) is suggested because the small sample area will give the soil is homogeneous and less disturbed, and small sample thickness will give the soil is fully consolidated in 24 h.