红层泥岩填料水敏性高,路基状态受含水率影响显著.为研究含水率对红层泥岩填料动力特性的影响,开展了 41组动三轴试验,5组压汞(mercury intrusion porosimetry,MIP)试验和3组扫描电镜(scanning electron microscope,SEM)试验,结果表明:填料等效模量和阻尼比具有应变振幅相关性,可用 Hardin-Drnevich 双曲线模型表述.随动应力增大,填料累积变形由稳定型向破坏型过渡.含水率影响填料累积变形响应和临界动应力,相同应力水平下干侧填料累积变形明显低于湿侧填料,达到变形限值的振次高于湿侧填料.干侧填料临界动应力大于湿侧,临界动应力随初始吸力增加而增加,可用VG模型表述.从微观结构看,含水率增加将导致填料微观孔隙结构由单峰形态向双峰形态转变,填料组构由密实稳定逐渐向无序松散转变,最终在宏观上表现为干侧填料动力特性优于湿侧填料.填料临界动应力与静强度比值为65%～75%,采用静强度作设计指标将高估路基承载力.推荐采用5.0%～7.0%含水率填料填筑红层泥岩路基.
Effect of water content on dynamic properties of red mudstone fill material
Red mudstone fill material(RMF)exhibits high water sensitivity which indicates that the performance of the subgrade is dependent on the water content.A series of mechanical and microstructure tests including 41 cyclic triaxial tests,5 mercury intrusion porosimetry(MIP)tests and 3 scanning electron microscope(SEM)tests were carried out to investigate the dynamic properties of RMF,with particular concentration on water content effects.Results show that the equivalent Young's modulus and damping ratio are correlated to the strain amplitude,which can be modeled by Hardin-Drnevich's hyperbolic equation.As the cyclic stress amplitude increases,a transition from stable to unstable permanent deformation is observed.The permanent deformation and critical cyclic stress vary with water content.Specifically,under the same cyclic stress amplitude,the permanent deformation of RMF on the dry side is less than that on the wet side.The number of loading cycles needed to achieve the target permanent deformation is higher for RMF on the dry side compared to the wet side.The critical cyclic stress is greater on the dry side and increases with initial suction,as characterized by the VG model.From the microstructural perspective,the pore size distribution changes from single peak mode to bi-modal structure as water content increases.The denser and more stable soil fabric is observed on the dry side,which results in the better performance of RMF on the dry side compared to that on the wet side.The ratio of critical cyclic stress to static shear strength ranges from 65%to 75%,indicating the overestimation of subgrade strength by the static strength design method.It is recommended to use RMF with a water content of 5.0%to 7.0%in the construction of red mudstone subgrades.
red mudstone fill materialwater contentpermanent deformationcritical cyclic stressmicrostructure
万方数据
维普
