高填方压实土时效变形特征与长期沉降分析

Analysis on Time-dependent Deformation Behavior and Long-term Settlement of Compacted Clay of High-filled Embankment

为更有效地分析和预测高填方路堤的施工与工后沉降,重点考虑了路基压实土的超固结、剪胀等力学特性以及率敏性、蠕变等时间相依变形特征,结合室内土工试验分析了其力学特性的影响因素。以Hashiguchi提出的下负荷屈服面为参考屈服面,按相对过应力理论,建立了能反映超固结土剪胀、应变软化、应力历史以及时间相依变形特征的弹黏塑性本构模型;结合三轴剪切试验的结果确定模型参数,并通过固结蠕变和等应变速率三轴压缩两类典型的率敏性试验对模型进行了验证。将提出的超固结土弹黏塑性本构模型的应力积分算法通过UMAT子程序嵌入ABAQUS软件,使其成功用于某高速公路坝式路堤沉降问题分析。结合高填方路堤现场沉降监测结果研究表明:高填方压实土的超固结应力历史以及时间相依的流变性质对其变形有着显著影响,提出的超固结土弹黏塑性本构模型能模拟压实土的剪胀、应变软化以及时效变形特征,能应用于三维复杂条件下高填方路堤的施工及工后沉降计算,且沉降预测结果与现场观测数据吻合良好,具有较好的理论研究和应用价值。

In order to analyze and predict the construction and post-construction settlement of high-filled embankment more effectively, considering the mechanical property of subgrade compacted clay（ overconsolidation and dilatancy） and its time-dependent deformation features（ rate-sensitivity and creep）and combining with the indoor geotechnical test,the influencing factors of the mechanical properties are analysed. Regarding the subloading yield plane proposed by Hashiguchi as the reference yield plane,an elastic-viscoplastic constitutive model,which can reflect the dilatancy,strain-softening,stress history and time-dependent deformation characteristics of over-consolidated clay,is established according to relative overstress theory. The model parameters are determined based on the data of triaxial shear experiment,and the model is verified by 2 kinds of typical rate-sensitivity test including consolidation creep test and constant strain rate triaxial compaction test. The stress integration algorithm of the proposed elastic viscoplastic constitutive model is embedded into ABAQUS through subprogram UMAT,which made the model applied successfully in the settlement analysis of the dam-embankment of an expressway. Combining the sitesettlement monitoring data of high-filled embankment,the research shows that（ 1） the over-consolidated stress history and time-dependent rheological property of compacted clay of high-filled embankment has a significant effect on the deformation;（ 2） the proposed elastic-viscoplastic constitutive model can simulate the dilatancy,strain-softening and time-dependent deformation of compacted clay,it can be applied to analyze the construction and post-construction settlement of 3 D complex high-filled embankment,and the settlement prediction result is in good agreement with the monitoring data,which means that the proposed model is valuable in theoretical research and application.