Existence of unsuitable soil for supporting structures in construction sites, lack of space and economic motivations are primary main reasons for using soil improvement techniques with poor subgrade soil conditions rather than deep foundation. Soil at a construction site may not always be totally suitable for supporting structures in its natural state. In such a case, the soil needs to be improved to increase its bearing capacity and decrease the expected settlement. This topic gives an overview of techniques that are commonly used to improve the performance, reduce the post construction settlement, and enhance the shear strength of the soil system, increase the bearing capacity of the soil, and improve the stability of dams and embankments. Then, this study concluded that there is an urgent need to study the technique of removal and replacement for improving soil behavior taking into consideration geotechnical requirements (i.e. bearing capacity and settlement) and cost to achieve the optimum thickness of replacement layers and the most suitable material corresponding to minimum total cost of foundation works. Keywords:- Investigation, Various Techniques, Soil Improvement.