experimental study of applying colloidal nano silica in improving sand-silt mixtures

Passive method is a new procedure in stabilizing loose soils. this methodology is a type of interlocking soil particles structures. in order to optimum improve in this method, it is necessary to achieve proper penetration length and increase the shear strength of parameters. researches have shown an increased resistance to liquefaction and decreased permeability due to colloidal nano silica injection in soil. in this research, sandy soil was mixed with silt in 5%, 10%, and 15% percent. then, specimens in dry and saturated conditions were placed under the influence of nano silica colloid. for determining geotechnical properties of improved specimens, direct shear test was performed in three situations (dry, saturated, and injected). moreover, for studying drainage condition after stabilizing specimens, constant head, permeability test was carried out. the results showed that geotechnical properties in the injected state increased compared to the noninjected state. generally, these increase in cohesion and integral friction respectively on average in specimen’s equal 2%, 1.18% and in saturate state equal 1.21%, 1.13%.  besides, with the injection of nano silica colloid, the amount of vertical settlement in the samples on average 22% decreased. furthermore, the amount of permeability of the stabilized materials showed on average 58% went down.