THE PERMEABILITY AND SHEAR STRENGTH OF COMPACTED CLAYSTONE–BENTONITE MIXTURES

Abstract

A compacted claystone–bentonite mixture is proposed for use as a clay barrier. This research, in turn, focuses on the effects of bentonite mix on the permeability and shear strength of compacted claystone‒bentonite mixtures. The claystone used was obtained from the Banjarbakula landfill project, approximately 10 km from Banjarbaru, the South Kalimantan Government's Administrative Center, Indonesia. The bentonite used is commercially sold in Indonesia. The claystone was mixed with bentonite at a percentage of 5%, 10%, 15%, and 20% bentonite by dry-weight bases. The mixtures were compacted at a moisture content of 10%, 15%, and 20% to reach the dry unit weight of 16kN/m3‒19kN/m3. Permeability and unconfined compressive strength tests were performed in this study. The result showed that the permeability of mixtures decreases with increasing bentonite content. The addition of up to 20% bentonite to the mixture reduced the permeability by 4.5 times, as compared to the sample without bentonite. Moreover, the mixtures’ shear strength indicated by compressive strength and cohesion increased by increasing the bentonite content to 15%. The maximum shear strength obtained was three times higher than without bentonite. The mixtures’ permeability and shear strength were also significantly affected by the sample's density and moisture content. A percentage of 20% bentonite is recommended, considering the wide range of acceptability based on two criteria (i.e., permeability and shear strength).