堆石料强度及变形特性缩尺效应试验

Experimental study of scale effect on strength and deformation characteristics of rock-fill materials

对某原型级配堆石料,采用混合法根据规范要求缩尺,获得3条模拟级配曲线,相应的最大颗粒粒径分别为20 mm、40 mm和60 mm。对缩尺后的堆石料,采用同一相对密度作为制样标准,利用大型和中型三轴剪切仪分别进行不同围压下各向等压固结排水剪切试验,探讨堆石料强度和变形特性的缩尺效应。结果表明:堆石料的非线性强度指标φ0和Δφ均随试样最大粒径dmax的增加呈对数函数增大;通过研究粒径和围压对粗粒土变形性质的影响,发现初始弹性模量Ei和体积切线模量Bt均随dmax的增加而线性增大,初始泊松比νi随dmax的增大逐渐减小(两者之间存在良好的幂函数关系);此外,总结出Ei、νi和Bt与dmax及围压σ3之间的关系式,据此可初步估计dmax对Ei、νi和Bt的影响。

The hybrid method was adopted to model the original gradation of a rock-fill material according to the code, and three simulated gradations of rock-fill material have been obtained. By the same token, their equivalent particle diameters are 20 mm, 40 mm, and 60 mm, respectively. With samples prepared under the criterion of a same relative density, the scale effect on strength and deformation characteristics of the rock-fill material were studied by large/medium-scale and consolidated-drained triaxial compression tests. The results show that the nonlinear strength indexes, φ0 and Δφ, have an increasing trend of a logarithm function with the maximum grain diameter dmax of rock-fill material. Through analyzing the influences of particle size and confining pressure on the axial strains and volumetric strains, some useful conclusion can be drawn as: both the initial elastic modulus Ei and the tangent volumetric modulus Bt increase with the maximum grain size dmax, and there is a good linear relationships between the initial elastic modulus and the maximum grain size as well as that between the tangent volume modulus and the maximum grain size;the initial Poisson’s ratio νi decreases with the maximum grain size dmax, and there is a good exponential relationship between the initial Poisson’s ratio and the maximum grain size. Meanwhile, formulas considering the initial elastic modulus, the initial Poisson’s ratio, the tangent volume modulus, the maximum grain size and the confining pressure were obtained, which can roughly estimate the effect of maximum grain size on the initial elastic modulus, the tangent volumetric modulus and the initial Poisson’s ratio.