Improvement of dispersive soils by mixing with Bangkok clay or bentonite

Abstract

Several dispersive soil dams in Northeast Thailand have failed through surface and piping erosion. These dispersive soils are inorganic sandy, silty clay or clayey silt of low plasticity with a high content of dissolved sodium in the pore water. The addition of bentonite has no effect on the dispersivity. On the other hand, the addition of from 20% to 30% Bangkok clay transforms the soil into non-dispersive. The crumb test initially indicates the dispersivity of the soil. However, pinhole test and chemical tests are necessary to confirm the dispersivity. The liquid and plastic limits increase linearly with increasing percentage of Bangkok clay. The maximum dry density decreases and the optimum moisture content increases with increasing percentage of Bangkok clay.