Permeability Of Soil-Bentonite Cut-Off Wall Backfill Material

The effects of bentonite content on permeability, porosity and bound water of soil-bentonite mixtures were evaluated using the improved flexible wall test and the moisture centrifugal dewatering test with three different bentonites from China. The results showed that when backfills were formed by mixing bentonite and sand, there was a critical bentonite content of the lowest porosity. If the bentonite content was below this critical content level, permeability decreased rapidly, whereas if the bentonite content was above this critical level, permeability decreased slowly. Moreover, when the bentonite content increased, the bound water percentage of the mixtures constantly increased. Assuming that the bound water surrounded the bentonite particles, an approximate calculation method of the effective porosity was proposed.