地铁振动荷载作用下饱和软粘土性状微观研究

位于或穿越饱和软粘土层中的地铁隧道在运营之后，沿轴线产生较大的沉降量，很大程度上与饱和软粘土在地铁振动荷载作用下土体微观结构的变形和破坏、发生残余变形有关．通过扫描电镜试验对饱和软粘土颗粒的微观性状进行了研究，从土的微结构基本单元的形状和大小、基本单元体的接触状态、基本单元体问的联结形式、孔隙的形状和大小以及土体变形3个阶段的力学特性等方面进行较深入的研究．另外，将原状土和循环三轴试验破坏后两种状态的土样作了对比，从微观的角度解释了土体的变形机理．研究成果对有效控制、避免或减轻隧道经过地区地面沉降灾害的发生，指导地铁工程的设计、施工以及地铁运行后沉降的预测评价和防治等提供了有价值的参考．

Microscopic Study of Saturated Soft Clay's Behavior under Cyclic Loading

After the subway tunnel that is in or across the stratum of saturated soft clay is put to use,the excessive settlement occurs along axes in a large degree because the microscopic structure of the saturated soft clay is deformed and destroyed and the residual strain is produced under the subway vibrational loading.In this paper,the microscopic behavior of saturated soft clay is studied using scanning electronic microscope.The shape,size and contact form of the basic elements of the soil microscopic structure,and the shape,size of the pore,and the mechanic characteristics of three stages of the soil deformation are deeply studied.Besides,the deformation mechanism of the soil is explained from the microscopic aspect based on the contrast of the undisturbed sample and the failure sample by cyclic triaxial test.For controlling,avoiding or releasing the occurrence of the settlement disaster that is induced by tunnel transit efficiently,guiding the design and construction of subway engineering,and forecasting,appraising,preventing and curing settlement after the subway is put to use,the study offers valuable references.