基于不规则颗粒离散元的土石混合体大三轴数值模拟

在基于CT扫描的不规则颗粒三维离散元精细建模技术的基础上,提出了一种不规则块石三维离散元模型随机生成技术,并建立了符合宏观统计规律的土石混合体三维离散元模型。进行了含石量为0,10%,30%,50%,70%,90%的土石混合体大三轴试验数值模拟研究,对各种含石量下土石混合体的力学特性和变形破坏机理进行了深入地分析探讨。结果表明:随着含石量的增加,试样峰值强度、残余强度、弹性模量和破坏应变逐渐增大,剪缩性减小,剪胀性增强;加载初期,微裂纹主要在块石颗粒与土颗粒之间形成,发展速度很快,而后则主要在土颗粒间形成和扩展,含石量越大,块石周围微裂纹比例越高,局部剪切带越不规则,分布也越分散;高含石量(70%,90%)的土石混合体在加载初期即有比较明显的相互摩擦,随后块石相互接触、咬合与相对摩擦、滑移交替出现。

Numerical simulation of large-scale triaxial tests on soil-rock mixture based on DEM of irregularly shaped particles

Based on the refined method for constructing DEM model based on the computed tomography scanning of irregularly shaped (IRS) particles, a random technique for constructing DEM model for IRS rock block is proposed, and 3D DEM models for soil-rock mixture (SRM) which conforms to the macroscopic statistical rule are established. In order to study the mechanical properties and deformation mechanism of SRM with various rock block proportions (RBP), DEM numerical simulations of large scale triaxial tests are conducted. It is noteworthy that with the increase of RBP, the peak strength, residual strength, elastic modulus and axial strain at peak strength all increase. The increase of RBP leads to the increase of shear dilatancy deformation and the decrease of shear contraction deformation. During the initial period of axial loading, the microcracks originate mainly from the contacts between rock particles and soil particles very quickly and then develop in the soil matrix. With the increase of RBP, the proportion of microcracks around the rock particles increases, and local shear bands become more and more irregular and scattered. The rock particles of SRM with high RBP exhibit obvious inter-friction just in the early period, and then their inter-locking and relative sliding appear alternately.