Assessment of risk of liquefaction in granular materials and it's mitigation

Liquefaction of sandy soils during earthquakes is an important issue requiring careful study even though significant advances have been made in recent years in its numerical modelling. The numerical simulations are of great importance in providing an insight into the mechanics of liquefaction. However, in real life situations, what is more important is the advancement of suitable measures and methodologies to reduce the risk of liquefaction. In this paper, a framework of modelling the mechanical behaviour of partially saturated soils proposed by Pietruszczak & Pande (1996) is revisited. The approach is based on treating partially saturated soil as a composite material and applying established procedures of volume averaging. According to this formulation, the liquefaction potential of sandy deposits could be significantly lowered by reduction in the degree of saturation, even by a small amount. De-saturation can, in principle, be achieved by a variety of techniques including electrical and/or chemical treatment. In order to verify and validate this assertion, a preliminary experimental programme, in which zeolite was used to induce partial saturation in soil samples, was carried out. Development of excess pore pressure in triaxial tests as well as in an 'oscillating box' containing layers of soil in partially saturated states have been monitored. It is concluded that it may be fruitful to investigate the possibility of using de-saturation as a practical anti-liquefaction measure.