Vacuum preloading, an alternative soft ground improvement technique for a sustainable development

Abstract

Preloading with soil surcharging in combination with prefabricated vertical drain is one of the common methods used in improving high compressibility and low shear strength of soft soils, particularly in improving very soft to soft clay. One of the main issues of this technique is it requires a high volume of backfill material to apply the surcharging, hence, whenever the availability of the backfill material is scarce or remote, it becomes expensive. In such a case, vacuum preloading becomes one of the best options to be applied in alleviating the high compressibility and low shear strength of the soft clay layers. This vacuum technique also helps to create a sustainable environment as it omits the needs of a high volume of backfill material. Therefore, no hills cutting or ground excavation is required. This paper presents the difference between surcharging and vacuum preloading methods, the working principle, and installation of vacuum preloading. Case histories in improving the soft soils of in low land areas, a large residential located on high ground about 700m from sea level, and a highway construction projects are presented. The case histories revealed that proper application of vacuum preloading could effectively improve soft clays, be in a low land area or high ground area. The depth improved can reach as deep as 25m.