Abstract:

This article are represented the results of determination for the undrained shear strength of soft clayey soil amQ22-3 distributing in coastal provinces of Mekong delta by difference experimental designs and equipments. The undrained shear strength of soft clay by unconsolidated undrained triaxial compression test (UU), Unconfined compression test and Vane shear test, respectively: 10,3 to 15,1 kPa; 9,6 to 19,3 kPa and from 12,7 to 21 kPa; As the same for soft sandy clay soil, respectively : 10,2 to 20 kPa; 15,6 to 20,5 kPa and from 23,4 to 25,3 kPa. The effective shear strength of soft clay soil determining by consolidated undrained triaxial compression test with measurement pore pressure showed that effective friction angle (’) is range from 19026’ to 24000’ and effective cohesion (C’) is range from 9,1 to 15,6 kPa. As the same for soft sandy clay soil, ’ is range from 24027’ to 31048’ and C’ is range from 5,6 to 14,5kPa. As the clay content increases, the plasticity index increases, the effective cohesion increased, effectively reducing the effective friction angle.