基于Voronoi块体模型的砂岩力学特性研究

PFC软件中球形颗粒和平行黏结接触模型(PBM)被广泛应用于岩石力学特性模拟研究.然而，球形颗粒和PBM存在两个明显缺陷:球形颗粒与岩石材料的晶粒形状相差较大;无侧限抗压强度与抗拉强度之比(压拉比)偏低.基于此，以山西吕梁地区典型砂岩为例，通过Voronoi剖分建立刚性块体数值试样，并使用软化黏结接触模型(SBM)对砂岩试样进行模拟分析.研究结果表明，基于刚性块体和SBM的数值模拟相较于传统基于球形颗粒和PBM的数值模拟而言，主要具有3个优点:与球形颗粒试样相比，刚性块体间自锁效应增大，刚性块体模型间的配位数明显提高，更能模拟真实砂岩的晶粒形状和晶粒间力学行为;软化黏结模型能模拟出砂岩更大的压拉比，更能真实表征砂岩在多应力路径下的力学特性;采用基于刚性块体和SBM的数值模型能够真实反映砂岩典型的剪切破坏模式.

Study on Mechanical Properties of Sandstone Based on Voronoi Block Model

The spherical particle and parallel bond model(PBM)in PFC(particle flow code) software is widely used to simulate the mechanical properties of rock. However， spherical particles and PBM have two intrinsic drawbacks: the grain shape of spherical particles is quite different from that of rock materials， and the ratio of unconfined compressive strength to tensile strength(UCS/TS)is low. Based on this， taking the typical sandstone in Lüliang area of Shanxi Province as an example， the rigid block numerical specimens are established by Voronoi tessellations， and the mechanical properties of sandstone are studied by using the softe-bond model(SBM). The results show that the scheme has three advantages compared with the traditional numerical simulation based on spherical particles and PBM: compared with the spherical sample， the grain interlocking between the rigid blocks increases， and the coordination number between the rigid block models increases significantly， which can better simulate the grain shape and mechanical behavior of real sandstone. The SBM can simulate the larger unconfined compressive strength to tensile strength ratio of sandstone， which can truly characterize the mechanical properties of sandstone under multiple stress paths. The numerical model based on rigid block and SBM can truly reflect the typical shear failure mode of sandstone.