土石混合料剪切特性及块石破碎特征

通过室内大型直剪试验和基于PFC2D的颗粒离散元数值模型，探讨考虑块石破碎的土石混合料的剪切特性及块石破碎特征。以土石混合料室内大型直剪试验和筛分试验为基础，提出了一种能真实描述块石形态特征并准确反映块石破碎效应的土石混合料颗粒离散元数值建模方法，模拟并分析了6种含石量土石混合料在4种不同法向应力作用下的剪切特性及块石破碎特征。结果表明：土石混合料抗剪强度随含石量的增大而增大，且基本符合摩尔-库仑（M-C）强度准则，随着含石量增大，内摩擦角呈现“慢-快-慢”增长趋势，黏聚力则呈现先增后减再增大的变化趋势。剪切后土石混合料块石破碎形式可归纳为表面研磨、局部破碎、完全破裂、完全破碎4种方式。提出了一种新的颗粒破碎指标，该指标能够准确描述粒径大于5 mm的块石的破碎程度，其随含石量和法向应力的增大而增大。通过对土石混合料颗粒离散元数值模型剪切面的分析发现，剪切面出现“剪斜”现象，其起伏程度随含石量增大愈加明显，且随着含石量增大剪切面附近剪裂隙数量增多，土石混合料在剪切过程中的破坏为拉-剪混合破坏。

Shear properties and rock block breakage characteristics of soil-rock mixtures

This study is to investigate shear properties and rock block breakage characteristics of soil-rock mixtures (SRMs) by lab large-scale direct shear tests and particle discrete element numerical simulation using PFC2D. A particle discrete element numerical method for SRM, accurately describing the shape characteristics and the breakage effect of rock block, is presented with comparisons of the results of large-scale direct shear tests and sieving analysis tests. The shear properties and rock block breakage characteristics of SRMs of six different rock block contents under four different normal stresses were studied. The result basically complies with Mohr-Coulomb strength criterion, showing the higher the rock block content, the higher the shear strength of SRMs. With the increase of rock block content, the internal friction angle of SRMs shows slow-fast-slow growth trend, but the cohesion presents a trend of first increase, then decrease and then increase. The breakage forms of rock block can be classified into 4 categories: surface grinding, partial breakage, complete rupture and complete breakage. A new particle breakage index is presented to accurately reflect the breakage degree of rock block with particle size greater than 5 mm. The index increases as the rock block content and normal stress increasing. The analysis of shear surface of particle discrete element numerical model shows that the shear surface appears ‘shear oblique’ phenomenon. The breakage degree is more obvious and the number of shear cracks near shear surface increase as rock block content increasing. The failure of S-RMs during shearing is tension-shear mixing failure.