Compacted states and physical properties of soil controlled by the degree of saturation during compaction

¹ Tokyo University of Science, Civil Engineering Department, Chiba, Japan
² NTC Consultants Co., Ltd., Japan

^* Corresponding author: tatsuoka@rs.noda.tus.ac.jp

Abstract

For satisfactory performance of soil structures, it is necessary to properly control soil compaction ensuring the physical properties of compacted soil required in design. Usually the dry density ρd and the water content w are controlled in relation to the maximum dry density (ρd)_max and the optimum water content wopt determined by laboratory compaction tests on a chosen representative sample at a certain compaction energy level CEL. Although CEL and soil type affect significantly (ρd)_max, wopt and physical properties, they change inevitably, sometimes largely, in a given project while field CEL may not match the value used in the laboratory compaction tests. In comparison, the optimum degree of saturation (S_r)_opt (i.e., S_r when (ρd)_max is obtained) and the normalized compaction curve (i.e., ρd/(ρd)_max vs. S_r - (S_r)_opt relation) for given CEL and soil type are insensitive to variations in CEL and soil type and they are essentially fixed in a given project. Besides, the stress-strain and hydraulic properties of compacted soil are controlled by ρd and “S_r at the end of compaction relative to (S_r)_opt”. It is proposed to control w and CEL so that S_r= (S_r)_opt while ρd becomes large enough to ensure the physical properties required in design fully taking advantage of available field CEL on site. A case history of earth-fill dam construction in Japan following this soil compaction control method is reported.