Compressibility and shear strength of remoulded Dhaka clay

Abstract

This study is aimed at evaluation of the intrinsic properties of Dhaka clay, their interactions and to develop a model for predicting undrained shear strength. In this study, the undrained shear strength (Su) behaviour was investigated for reconstituted Dhaka clay subjected to Ko, isotropic consolidation followed by a number of loading and unloading stress history. The intrinsic parameters of the clay thus obtained were used to predict the strength of natural Dhaka clay for various stress history and stress conditions. For the laboratory investigation, samples of Dhaka clay were mixed with water (1.5 times the liquid limit) to form a slurry. From slurry, normally consolidated and overconsolidated samples of various overconsolidation ratios (OCR) were prepared under different stress conditions. The slurry was consolidated in a Rowe Cell. A 210 mm diameter Rowe consolidation Cell and test set up was developed for this purpose. Four categories of samples were prepared. For each category, cylindrical samples were prepared by trimming into size of 38.1 mm diameter and 76.2 mm height from the soil cake extruded from the Rowe Cell after consolidation of slurry. The first category of samples (KoNC) were Ko consolidated and sheared in triaxial compression in undrained state. The second category of samples (KoOC) were Ko consolidated and unloaded to a specified OCR value and then sheared in undrained triaxial compression. The third category of samples (KoINC) were Ko consolidated, extruded from Rowe cell and reconsolidated isotropically to a higher pressure and then tested to undrained compression failure. The fourth category of samples (KoIOC) were subjected to same conditions as that for third category but was unloaded to a preferred OCR before undrained compression failure in triaxial apparatus. Stress-strain behaviour for each category of samples were recorded --------------------