Load–Settlement Behaviour of Prestressed Reinforced Soft Soil Foundations of Embankments

Abstract

The stability of embankments supported on soft clay foundation is a complex problem. To improve the stability of embankment and its foundation, the most feasible option is to reinforce the locally available soil with suitable geosynthetics since granular soil is now very scarce and costly. The effectiveness of geosynthetic reinforcement embedded in cohesive soil is very less due to build-up of pore water pressure, creep and less interaction with soil. Moreover geosynthetics demonstrate their beneficial effects only after considerable settlements, since the strains occurring during initial settlements are not sufficient to generate significant tensile stress in the reinforcement. Prestressing the geosynthetic and encapsulating it in a thin granular soil layer is a promising technique to reduce the requirement of granular soil and to increase the load bearing capacity without the occurrence of large settlements. This paper investigates the beneficial effects of prestressing the geosynthetic and encapsulating it in a thin layer of granular soil when used to reinforce a soft soil foundation of an embankment. A series of finite element analyses are carried out using the FE software PLAXIS 2D, and its results are validated by comparing them with those obtained from laboratory scale load tests. It is observed that the load–settlement behaviour can be considerably improved by reinforcing the soft clay foundation with prestressed geosynthetic encapsulated in a thin layer of granular soil. The improvement is significantly influenced by the magnitude of prestress in the geosynthetic reinforcement.