Investigation of the Effect of Different Saturation Methods on the Undrained Shear Strength of a Clayey Soil Compacted with Standard and Modified Proctor Energies

Abstract

In this study, unconsolidated-undrained (UU) shear strengths of a clayey soil that is subject to saturation separately by using vacuum saturation method and falling head method were investigated. In the study, a soil with CL class according to Unified Soil Classification System was used. The soil samples prepared by being compacted in a rigid-wall permeameter mechanism were subject to a saturation process for periods varying from 1 week to 4 weeks. In the saturation by using falling head method, maximum 4m hydraulic load was applied to the samples. In saturation by using vacuum method, minimum - 70 kPa vacuum was used. After the saturation process, the samples were subject to UU type triaxial tests. Depending on the saturation method and duration, a decrease of approximately 2 - 3 times was observed in UU shear strength parameters (c_u and ϕ_u) of the samples, which are subject to the saturation process, compared to the unsaturated samples. In the samples compacted with Standard Proctor Energy (SPE), strength parameters obtained under vacuum for one week were lower compared to samples saturated for 4 weeks by using the method of saturation by gravity. In the samples compacted with Modified Proctor Energy (MPE), vacuum method did not give a successful result.