Sustainability of Combined Vacuum and Surcharge Preloading

This paper presents a review of combined vacuum consolidation and surcharge preloading which is arguably more sustainable approach to soft-soil ground improvement than other strategies in reducing post-construction settlements. Vacuum consolidation has become more prevalent with technological developments in vertical drains, pumps and geosynthetics. Satisfactory vacuum pressures can be sustained at greater depths and for longer periods than in the recent past. Soft soil deposits may experience different issues depending on whether vacuum or surcharge preloading is employed. Surcharging alone may lead to outward lateral deformations and shear failure whereas vacuum alone induces inward lateral deformations, producing crack formation along the boundaries of the treatment area. By balancing these two approaches, respective outward and inward ground movements can be minimised.