【作者】 刘飞禹；

【导师】 蔡袁强；

【作者基本信息】 浙江大学 ， 岩土工程， 2007， 博士

【摘要】 本文针对交通荷载作用下软土地基的动力特点，通过室内动三轴试验详细研究了循环荷载作用下软土的动力特性，并采用有限元和半解析的方法研究了循环荷载和移动荷载作用下加筋道路的动力响应。 首先采用英国GDS公司研制生产的高精度动静三轴试验设备，对杭州地区饱和软粘土进行了应力控制的循环三轴试验，详细研究了饱和软粘土在循环荷载作用下的应变、孔压等特性，分析了各种因素对软土动力特性的影响，重点研究了偏移应力的大小、荷载频率、超固结比、循环应力比等因素对软土动弹性模量衰减的影响，并经过回归分析得到了反映动弹性模量衰减规律的经验公式。 然后编制了用户子程序将该公式导入有限元分析软件ABAQUS中，采用ABAQUS对软基加筋与不加筋道路在交通荷载作用下的动力响应进行了对比分析，研究了动荷载作用下软基加筋道路的作用机理。结果表明，软土的软化特性对软基加筋和不加筋道路的动力响应有明显影响，同时，加筋可以使土体应力均化，约束土体的水平变形，减小道路的整体沉降，并减少道路的不均匀沉降。之后又详细研究了荷载形式、荷载频率、筋材模量、加筋位置、加筋层数、软土层厚度等对加筋效果的影响。 最后将多层筋材加筋的路堤看成宏观上的横观各向同性体，用半解析法分别对移动条形荷载作用下未铺面层的饱和加筋路堤和铺设面层的饱和软基加筋道路系统的动力响应问题进行了研究。对于未铺面层的饱和加筋路堤，由忽略土粒压缩和土体自重的Biot波动方程出发，对荷载进行Fourier级数展开，假设了响应函数的级数形式，结合边界条件，由待定系数法求解了考虑固液耦合作用的饱和加筋复合土体在移动荷载作用下的土体位移及孔压表达式。对于铺设面层的饱和软基加筋道路系统，将加筋道路的面层简化为弹性梁，加筋路堤作为横观各向同性体，同时考虑了下卧土层孔隙水的影响，由忽略土粒压缩和土体自重的Blot波动方程出发，结合边界条件，由待定系数法求解了考虑固液耦合作用的软基加筋道路系统在移动荷载作用下的土体位移及孔压表达式。最后，结合算例分析了加筋率、筋材模量、荷载移动速度等对加筋道路竖向位移和孔压的影响。更多还原

【Abstract】 A series of undrained cyclic triaxial tests were conducted on typical Hangzhou soft clay to study the performance of soft clay under traffic loading.The FEA and semi-analytical methods were used to investigate dynamic responses of reinforced pavements under cyclic loads and moving loads.Firstly, in order to study the performance of soft clay under cyclic loading, a series of undrained cyclic triaxial tests were performed on typical Hangzhou soft clay by GDS dynamic triaxial system. The effects of initial deviator stress, loading frequency, overconsolidation ratio, and cyclic stress ratio on dynamic elastic modulus were investigated. The effects of initial deviator stress and overconsolidation ratio on degradation is significant. However, the changes of the frequencies and cyclic stress ratio have little effect on the degradation. The empirical equation for the relationship between degradation of dynamic modulus and strain was proposed by regression analysis method.Then the empirical equation was imported into FEM program ABAQUS through compiled subroutine. Dynamic response of unreinforced and geogrid reinforced pavements was studied by ABAQUS in order to investigate mechanisms of reinforcement. FEA results indicated that softening behavior of clay had visible effect on the performance of unreinforced and reinforced pavements. Geogrid reinforcement can provide lateral confinement at the bottom of the base layer by improving interface shear resistance and improve stress distribution on subgrade layer. The effect of geogrid reinforcement was also shown to reduce surface deformation and nonuniform settlement. A series of finite element simulation were carried to investigate the beneficial effects of geogrid reinforcement to the vertical displacement, and how such effects were influenced by the loading forms, loading frequency, geogrid modulus, geogrid location, geogrid layers and subgrade thickness etc..Finally, by using the homogenized transversely isotropic concept, the dynamic responses of unpaved reinforced embankment overlaying bedrock and paved reinforced pavements system subjected to moving loads were studied analytically/numerically under conditions of plane strain.For unpaved reinforced embankment, The full dynamic poroelastic theory of Biot was employed, under the assumption of an incompressible solid grain and neglecting the apparent mass density. The loading function was presented by a Fourier series expansion.By using the boundary condition, the governing equations of motion were then solved. The更多还原