Many types of earth construction,happens around us such as dams, retaining walls, highways & airport.Most buildings are built right on the soil rather than having footings going all the way down to bedrock, as with skyscrapers. If the soil is not compacted enough, the house will not last as long and can encounter many problems. The soil must be dense enough to support the weight of the structure. If the soil is not compacted enough it can collapse. The foundations for buildings are often built only after the less compacted surface layer of soil has been removed and the soil mechanically compressed. To compact a soil, means to change the loose soil to dense state. The dense state is achieved The dense state is achieved through the reduction of the air voids in the soil, with little or no reduction in the water content. This process must not be confused with consolidation of soil,in which water is squeezed out under the action of a continuous static load.