Chloride Migration through Clayey Silt Underlain by Fine Sand or Silt

Abstract

Chloride diffusion coefficients of 5.7 × 10 −10 m 2 /s, 9.0 × 10 −10 m 2 /s, and 9.8 × 10 −10 m 2 /s were obtained from diffusion tests conducted on a single isolated layer of clayey silt, silt, or sand, respectively. The advective-diffusive movement of chloride through a two-layer soil system consisting of a compacted clayey silt underlain by either a fine sand or silt was also examined. The agreement between the experimental results and model predictions suggests that existing solute-transport theory can adequately predict chloride migration through a compacted clay layer and underlying sand or silt layer at near-saturated conditions for Darcy velocities at least up to the maximum value examined (0.0183 m/yr or 500 L/ha/d). Chloride transport was dominated by diffusion in these tests.