Compaction Characteristics and Physical Properties of Compacted Soil Controlled by the Degree of Saturation

The conventional fill compaction procedure usually controls the dry density ρdand the water content w referring to the maximum dry density (ρd)maxand the optimum water content woptdetermined by laboratory compaction tests performed at a certain compaction energy level (CEL). However, (ρd)maxincreases and woptdecreases with CEL, while, since Proctor (1933), CEL practically available in the field has been increasing and the required ρdvalue has generally been becoming higher for more satisfactory performance of soil structures. Besides, the values of (ρd)maxand woptchange with soil type. In a single earthwork project, the actual CEL and soil type may vary and it is very difficult to accurately estimate the field CEL and identify the actual soil type at a given moment at a given place. Therefore, the actual values of (ρd)maxand woptare usually unknown. On the other hand, the optimum degree of saturation (Sr)optdefined as Srwhen (ρd)maxis obtained for a given CEL and the ρd/(ρd)maxvs. Sr−(Sr)optrelation are rather independent of CEL and soil type. The unsoaked and soaked strength and stiffness and the saturated hydraulic conductivity are a function of ρdand compacted Srnot including CEL as a variable. It is proposed to control Srof compacted soil to be close to (Sr)optand ρdto be large enough to achieve the physical properties required in design, together with pre-compaction control of water content.