Review of Soil-Bentonite (SB) Cutoff Walls to Control Seepage Through Earth Dams

Abstract

According to the records of the Irrigation department, there is a considerable amount of water loss from the reservoirs due to seepage through the earth dams. Even though numerous methods have been adopted to control seepage, this is still a burning problem in the irrigation sector. As such, the possibility to use Soil-Bentonite cutoff walls to control seepage through the earth dams is reviewed in this research study. Soil-Bentonite (SB) slurry walls are frequently the best and most economical cutoff wall to control the horizontal groundwater flow and contaminant transport. Permeability is the main engineering parameter when designing and constructing SB cutoff walls. Generally, SB walls have a permeability of less than 1x〖10〗^(-9) m/s. The performance of permeability of SB backfill is dependent on the performance of bentonite and backfill mix. Typically, most literature indicates that fine fractions can influence the performance of SB walls in terms of hydraulic conductivity other than bentonite content. According to the literature, 15% fine content is recommended for a well-graded backfill matrix. In fine contents, clay fines perform better than silt fines, as clay fines naturally perform effective swelling approaches when pore water appears. Plastic fines show 1x〖10〗^(-7)- 1x〖 10〗^(-8) m/s hydraulic conductivity for 10-70% fines fractions, while non-plastic fines show 1x〖10〗^(-5)- 1x〖 10〗^(-6) m/s for the same fine fraction. The compressive strength of soil-bentonite backfill was found to be very low as 15 kPa. It remains constant for design life. Considering the failure of SB cutoff walls, literature shows that a few incidents have occurred due to the static load conditions. However, the most important factor in the failure of soil-bentonite cutoff walls is the available water head (hydraulic fraction) difference.