Strength and Deformation Characteristics of Bandung Lacustrine Clay Under Consolidated-Undrained True Triaxial Testing

Abstract

The effect of intermediate and principal stress rotation is commonly ignored in the determination of soil stress deformation behavior under two-dimensionally or plane strain conditions. In actual field conditions, soil receives the load three-dimensionally and undergoes stress rotation to reach a stable condition. Therefore, a stress deformation test considering the effect of the intermediate and principal stress rotation to obtain real soil behavior was conducted. Bandung lacustrine soft clay is formed by the deposition of clay soils in the giant ancient lake which is estimated to have about 200 m depth from the ground surface. Undisturbed soil samples from this soft clay were taken and investigated in the laboratory by using Consolidated-Undrained True Triaxial Test. The experiment shows that effective shear strength (ϕ') increases with increasing stress variation (b) up to 10% in the increment of intermediate principal stress 0.5 times to the major principal stress. Giving load with principal stress rotation changed from 0 (zero) degrees to 90 (ninety) degrees produces a decrease in undrained shear strength (S_u/σ_c) up to 15%. The stiffness modulus and the Skempton A_f parameter also increase with increase in stress variation. The results obtained from this study is considered important to evaluate the suitable soil constitutive model for finite element load-deformation analysis.