Effect of overburden stress and surcharge pressure on the liquefaction response of sands

The physics and mechanism of soil liquefaction is understood sufficiently well by researchers now. However, the effect of various external factors such as the weight of the structure and overburden pressure on the liquefaction behavior of cohesionless soils is still under investigation. This paper presents a comprehensive study consisting of shaking table experiments on saturated sand beds to understand the effect of overburden pressure for free field conditions and the effect of surcharge weight for under the structure conditions on the liquefaction response of the sand beds. Pore water pressure was monitored continuously and the loss of effective stress with dynamic time was calculated for all the tests. Liquefaction occurred for shaking under specific ground motion conditions, which was visibly seen in the shaking table tests when the sand bed started to shake like a liquid and sand boils were formed on the bed. The number of cycles of dynamic shaking required for liquefaction and the pore water pressure were compared for different models. It was observed that increase in overburden pressure increases the liquefaction resistance of the soil. For sand beds under building pressure, the liquefaction response was observed to depend a great deal on the dynamic loading parameters. In the case of sand beds under surcharge loads, the response was complicated because of the complex soil–structure interaction under dynamic loading conditions.