Consolidation Properties and Hydraulic Conductivity for Bentonite with Various Exchangeable Sodium Percentage and Solution Concentrations

Abstract

Consolidation experiments were conducted for Ca-Na bentonites with various ESP (0, 24, 100) and solution concentrations (0.1, 0.05, 0 molc/l). The compression index C_c and the coefficient of volume compressibility my were significantly higher for ESP = 100, whereas C_c and m_v were almost identical for ESP=0 and 24. The coefficient of consolidation C_c decreased for higher ESP. The C_c for ESP=100 was one-order of magnitude smaller than that for ESP=24. The hydraulic conductivity k decreased exponentially as the porosity n decreased. The k for ESP=24 was slightly smaller than that for ESP=0, while k for ESP=100 was two to three orders of magnitude smaller than that for ESP=24. Observed consolidation behavior did not depend on solution concentrations. Although ESP>15 is conventionally used to define a sodic soil, the results for ESP=24 were close to those for ESP=0. The soil matrix of the betonite during the consolidation changed on a larger scale compared to a clay micro-structure which could be easily influenced by soil solution concentrations and ESP.