湿度有限波动下非饱和黏土路基动态回弹模量

Dynamic resilient modulus for unsaturated clay soils considering effect of limited moisture content fluctuation

通过压实黏土的土-水特征曲线试验和重复动三轴试验,揭示了在不同湿度状态、干湿路径、有限湿度波动下回弹模量的变化规律,研究了回弹模量与基质吸力的相关性,构建了基于基质吸力的湿度波动折减系数η的预估方程。结果表明:回弹模量与基质吸力之间具有较强的非线性相关性;干化路径的动态回弹模量均大于相同含水率下湿化路径的动态回弹模量;动态回弹模量在波动初始衰减最明显,降幅可达23%~37%;基于基质吸力的η预估方程可求解不同湿度波动幅度和次数下的动态回弹模量,预估效果优于采用饱和度的预估方程。

The resilient modulus(MR) is an important parameter to characterize the elastic support performance of subgrade. MR is significantly affected by subgrade limited moisture content fluctuation after traffic opening. Soil-water characteristic curve(SWCC) tests were conducted to investigate the relationship between MR and degree of saturation of the compacted and unsaturated clay soils. Repeated load triaxial(RLT)tests were carried out to obtain MR under three moisture conditions:different moisture contents,drying or wetting path and different moisture fluctuations,to investigate the correlation between MR and matric suction. The prediction model of MR under moisture fluctuation was proposed based on the matric suction. Test results show that the MR has a good non-linear relationship with matric suction. The MR of the drying path is greater than that of wetting path under the same moisture content. With the number of moisture fluctuations increases,the dynamic MR can be firstly decreased by 23%~37% when the moisture fluctuation is 1~2 times,then MR gradually stabilizes. The influence of the frequency and amplitude of moisture fluctuation on the dynamic MR can be considered simultaneously in the proposed prediction model,and the model has higher predicting accuracy compared with the models depend on degree of saturation.