Introduction

Various soil/ground improvement methods are presented that have been tested to provide soil strength improvement, mitigation of total and differential settlements, shorten construction time, reduce construction costs, and other characteristics which may impact on their utilization to specific projects. Considering such factors as the significance of the structure, applied loading, site conditions, period of construction, etc., it becomes important to select the appropriate method suitable for specific soil types as tabulated in Table 1.1 . For soft and cohesive soils in subsiding environments, soil/ground improvement by reinforcement (i.e. sand compaction piles), by admixtures (i.e. deep mixing method) and by dewatering (i.e. vertical drains) are applicable. A chart showing the procedures for modelling and selecting the soil/ground improvement techniques has been presented by Kamon & Bergado (1991) and is given in Figure 1.1 . For infrastructures on embankment fill, soil/ground improvement is not limited to portions below ground but also includes improvement of fill soils above ground. In this regard, considerations will be made regarding the improvement of fill soils by reinforcing with grids and/or geotextiles as well as by the use of lightweight materials such as expanded polystyrene and other related products.