Abstract: Direct(quick) shear tests were conducted on plain soil, line-treated expansive soil, and remoulded lime-treated expansive soil for comparison under 0, 12.5, 25, 50, 75, 100, and 150 kPa to examine the shear strength of remoulded lime-treated expansive soil. Results demonstrated that the values of shear strength of remoulded lime-treated expansive soil under all loading levels were lower than those of lime-treated expansive soil while higher than those of plain soil. Fitted with the method in Test Methods of Soils for Highway Engineering (JTG E40-2007), the shear strength of plain soil saw the largest deviation under low stress, and lime-treated expansive soil the smallest. Fitted with the bilinear method, the shear strength showed the smallest deviation under all stress levels. Moreover, the coefficient of deterioration of shear strength of remoulded lime-treated expansive soil declined with the rising of overlying pressure, displaying two obvious stages. When overlying pressure is smaller than 25 kPa, the deterioration coefficient is largely affected by overlying pressure; when larger than 25 kPa, the recession of deterioration coefficient attenuated with the rising of overlying load. The cohesive force of remoulded lime-treated soil is larger than that of plain soil while smaller than that lime-treated expansive soil, and the internal friction angle is larger than that of plain soil and lime-treated expansive soil. When the strength of plain soil meets the requirements for embankment filling, the remoulded lime-treated weak expansive soil can be used directly in core filling, but needs to be improved for surface filling.

Key words: lime-treated expansive soil, plain soil, remoulded soil, shear strength, deterioration coefficient