水泥改良黄土路基动力稳定性评价参数试验研究

An experimental study of the evaluation parameters of dynamic stability of the cement-improved loess subgrade

为满足高速铁路对路基工后沉降及长期动力稳定性的要求,并为黄土地区路基填料的选择提供参考,本文分别通过短时及疲劳动三轴实验对水泥改良黄土的动力稳定性评价参数(短时及疲劳动剪应变门槛)随水泥掺量、围压及固结比的变化进行了研究,并探讨了两者之间的量值关系,以期通过方便快速的短时动三轴实验得到疲劳动剪应变门槛。研究结果表明:短时条件下,竖向塑性应变随动应力的增加逐渐增加,最终呈现出脆性破坏的特点,而随水泥掺量、围压及固结比的增大逐渐减小;动模量Ed随动应力σd的增加呈现出先增大后减小的趋势,而与水泥掺量、围压及固结比的增长呈现正相关规律;随着水泥掺量、围压及固结比的增大水泥改良黄土短时及疲劳动剪应变门槛、动应力门槛均呈近似线性增加;同一条件下,水泥改良黄土的疲劳动剪应变门槛与短时动剪应变门槛的比值在0.29～0.34之间,随围压及固结比的增大变化较小。

There is a higher requirement of post-construction settlement and long-term dynamic stability for the high-speed railway subgrade.In order to satisfy this requirement and provide reference for the selection of subgrade fillers in loess areas,this paper uses the short-term and fatigue dynamic triaxial tests to examine the change in the dynamic stability evaluation parameters(short-term and fatigue dynamic shear strain threshold)(SDSST and FDSST) of the cement-improved loess with cement content(η),confining pressure(σ3) and consolidation ratio(Kc).The relationship between SDSST and FDSST is discussed,and it is expected to obtain the fatigue dynamic shear strain threshold by the convenient and rapid short-time dynamic triaxial experiment.The results show that(1) under the short time conditions,the vertical plastic strain increases with the increasing dynamic stress,and finally presents the characteristics of brittle failure,while gradually decreases with the increase of η,σ3 and Kc.(2) The dynamic modulus Edincreases first and then decreases with the increasing dynamic stress σd,while Edshows a positive correlation with the increase of η,σ3 and Kc.(3) The SDSST and FDSST,and the dynamic stress threshold linearly increase with the increase of η,σ3 and Kc.(4) Under the same condition,the ratio of FDSST to SDSST of the cement-improved loess ranges between0.29 and 0.34,which changes little with the increase of η,σ3 and Kc.