In geotechnical engineering, compaction refers to the process of statically or dynamically compressing the soil particles tightly together by expelling air from void spaces between the particles. The term


should not be confused with


(see Chapter 5). The aim of compaction is to increase the density of the soils and improve mechanical (i.e., increase in the shear strength and decrease in the settlements of built structures; Lambe and Whitman 1969) and hydraulic (i.e., decrease the permeability; Daniel and Benson 1990) properties of engineered soils. These improvements in soil properties are beneficial in many geoengineering structures, including highway embankments, earth dams, culvert construction, clay liners, and other foundation structures.