堆石料三维强度特性

Three-dimensional Strength Characteristic of Rockfill

考虑颗粒尺寸效应、破碎、分形等细观特征,结合大尺寸三轴试验结果,建立了堆石料的各向异性破坏准则。借助砂土细观组构描述方法,用组构张量描述堆石料颗粒细观特性,提出了新的各向异性状态变量;同时将该变量作为堆石料细微观演化的内变量建立了线性形式的堆石料破坏准则,构建过程既简化了表达式,又保留了现有指数形式破坏准则的优点,能够描述复杂应力条件下堆石料的强度特性。通过状态变量的变化,提出的准则能较好地描述不同各向异性条件下应力状态、路径、罗德角、主应力轴旋转等变化对堆石料强度的影响。引入正交各向异性组构,推导了随罗德角、主应力旋转角变化的各向异性状态变量表达式,给出了不同参数变化下的堆石料三维强度破坏面。用大型三轴排水试验结果确定材料破坏准则的参数,基于分形维数理论研究了不同级配的堆石料在不同围压下的强度和变形特性关系。验证表明:提出的各向异性破坏准则可以较好地描述堆石料分形维数、孔隙比和围压对其三维强度特性的影响;随分形维数及强度参数变化,该准则能较好地反映堆石料强度在细观特性下的变化关系。

In this study,the anisotropic failure criterion of rockfill was established by using largescale triaxial test to consider the particle-size effect,particle breakage,particle fractal and other microscopic characteristics.With the help of the sand mesoscopic description achievements of fabric,a novel anisotropic state variable is proposed as internal variable in the mesoscopic and microscopic evolution of rockfill,the fabric tensor is used to describe the micromechanical properties of rockfill.The rockfill failure criteria were established in linear form by introducing state variables.The failure criteria not only had a simple expression but also inherited the advantages of the existing index form of failure criteria.It also described the strength characteristics of rockfill under complex stress conditions.Through the change in the characteristics of the novel state variables,the proposed failure criterion better describes the effect of changes in the stress state and path,the Lode angle,and the rotation of the principal-stress axis on the strength of rockfill under different anisotropic conditions.The results of the large-scale triaxial drainage tests were used to determine the parameters of the failure criterion of rockfill.The relationship between the strength and deformation characteristics of different gradations under different confining pressures conditions was studied based on the fractal dimension theory.The verification indicates that the failure criterion better describes the influence of the fractal dimension,void ratio and confining pressure on the three-dimensional strength characteristics.With the change in the fractal dimension and strength parameters,the failure criterion also better reflects the change relation of rockfill strength on the mesoscopic level.