Coefficient of Lateral Earth Pressure at Rest of Remolded Soft Bangkok Clay under Increasing Effective Vertical Stress

This research mainly focused on how to determine the coefficient of lateral earth pressure at rest (Ko) for normally consolidated soft Bangkok clay. Traditionally, such a coefficient is determined using a triaxial test equipment. However, the procedures to perform Ko-consolidation via the triaxial test is highly complicated as it is necessary to maintain the vertical strain to be equal to the volumetric strain. The measured value of Ko would be erroneous if such a criterion could not be met. Therefore, a new methodology and artificial
equipment are proposed in this research. The experiments were performed by using high precision sensors in combination with an automatic feedback control system that was able to measure stresses in three axes; the set up could reproduce significant boundary conditions in the field. The specimens were consolidated by differential pre-consolidation pressures. The values of Ko were measured at the end of the primary consolidation. The proposed automatic controlling system worked very well to constrain the lateral movement while consolidation was performed. The Ko value did not depend on both pre-consolidation pressures and undrained shear strength.