Abstract

Sodium bentonite is the major type of bentonite used for soil–bentonite slurry trench cutoff wall construction. However, application of low swelling calcium bentonite (Ca-bentonite) is extremely meaningful for countries where high-quality sodium bentonite is scarce, while Ca-bentonite is plentiful. This study presented investigation of hydraulic conductivity of soil–bentonite backfill containing sodium hexametaphosphate (SHMP)-amended Ca-bentonite in lead nitrate solution with Pb concentration of 4.8 mM (1000 mg/L). Duplicate flexible-wall hydraulic conductivity tests were conducted using tap water first and followed by the lead nitrate solution. The volume, pH, and electrical conductivity of the inflow and outflow liquids were monitored, and Pb concentrations in the outflow liquid were measured. The variation in hydraulic conductivity with the pore volume of flow of permeant liquid was assessed. The results show that the hydraulic conductivity maintained a value lower than 10–9 m/s in either tap water or Pb solution. The Pb solution had insignificant adverse effects on hydraulic performance of the backfill containing amended bentonite during the tested period.

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