Estimation of the swelling strain and swelling pressure of compacted bentonite using electrical conductivity

Abstract

Estimation of the swelling strain or swelling pressure is important for predicting the behavior of compacted bentonite barriers. In this study, the electrical conductivity of compacted bentonite was measured under free-swell and confined conditions to investigate the predictability of swelling strain or swelling pressure from the measured electrical conductivity. The evolution of electrical conductivity by water penetration was qualitatively consistent with that of swelling strain or swelling pressure, implying that monitoring electrical conductivity could be used to detect the initiation and termination of swelling process or any internal changes in compacted bentonite. The relationships between normalized swelling strain and normalized electrical conductivity, and between normalized swelling pressure and normalized electrical conductivity were developed based on the results of Ca-bentonite hydrated with NaCl solution, and those were verified using the results of Ca-bentonite hydrated with KCl and CaCl2 solutions, and Na-bentonite hydrated with NaCl solution. Finally, the limitations and possibilities of using electrical conductivity in estimating swelling parameters and monitoring swelling process were discussed in this study.