Abstract: Moisture content of subgrade gradually changes from the initial compaction moisture to equilibrium moisture content during in-service period, which leads to the evolution of the subgrade soil road performance. By summarizing the measured results of shear modulus with compacted soil moisture content in literatures and complement experimental data, this paper investigates the effect of moisture content and the degree of compaction on the shear modulus of compacted soil. The results show that, when the degree of compaction is a constant, the shear modulus of subgrade soil decreases with increasing of moisture content. The shear modulus of subgrade soil decreases larger as degree of compaction increases. Shear modulus increases with increasing degree of compaction in low moisture contents. However, shear modulus increases first and then decreases with increasing of the degree of compaction in higher moisture contents. The degree of compaction corresponding to the peak modulus decreases with increasing moisture content. Moisture content corresponding to peak shear modulus is slightly less than the optimum moisture content corresponding to maximum dry density. Shear modulus of compacted soil increases first and then decreases with the increasing of liquidity index. But liquidity index corresponding peak shear modulus of different soils shows a good function with the clay content of soils.

Key words: compacted soil, shear modulus, moisture content, degree of compaction, liquidity index, clay content