为研究石灰改良膨胀土重塑后的抗剪强度性能,进行了素土、石灰改良膨胀土及重塑石灰改良膨胀土3种土体在0,12.5,25,50,75,100,150 kPa下的直剪(快剪)试验。试验结果显示,重塑石灰改良膨胀土各上覆压力下的抗剪强度均低于石灰改良膨胀土而大于素土。采用《公路土工试验规程》(JTG E40—2007)拟合土体的抗剪强度时,素土在低应力下的偏差最大,而石灰改良膨胀土最小,采用双直线法拟合时各应力段的抗剪强度值偏差最小。重塑石灰改良膨胀土的抗剪强度劣化系数随着上覆压力的增大而减小,且呈明显的2段。当上覆压力<25 kPa时,上覆压力对于土体性能劣化系数影响较大;当上覆压力>25 kPa时,抗剪强度性能劣化系数随着上覆荷载的增大而减小的幅度逐渐减小。重塑后石灰改良膨胀土土体的黏聚力大于素土而小于石灰改良膨胀土,内摩擦角大于素土及石灰改良膨胀土。从试验结论来看,在素土强度满足路堤填芯的情况下,重塑后的石灰改良弱膨胀土可以直接用于路堤填芯;但用于路堤表面填筑时,需要再改良。

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.