中文摘要：

VMIB模型是在VIB基础上提出的一种新型多尺度力学模型,VIB模型认为固体材料在微观上是由随机分布的质量微粒组成,微粒与微粒之间由一虚内键连接;而在VMIB模型中,微粒与微粒之间则由切向键和法向键共同连接或者由具有法向刚度和切向刚度的虚内键连接.材料的宏观本构方程直接由微粒之间的相互作用推导出来.由于VMIB能够再现材料泊松比的多样性,因此可以应用到更广泛的工程材料.非均质材料（岩石）由不同的组分构成,因此,材料中各点的力学属性不同.为有效地模拟这种材料的破坏过程,初步将岩石的非均质特性引入到VMIB模型中,并对裂纹的生成及扩展过程进行模拟.数值模拟结果表明：如果将岩石视为均质材料,则在围压下的裂纹扩展具有很强的规则性,出现单一剪切裂纹,岩石呈剪切破坏;如果将岩石视为非均质材料,则多条裂纹同时在不同点处开始生成、扩展并汇合,破坏模式总体上呈剪切破坏.从数值模拟结果来看,该法能够模拟非均质材料（岩石）的破坏过程,并能初步反映非均质特性对宏观裂纹行为的影响.

英文摘要：

Virtual multi-dimensional internal bonds（VMIB） is a multiscale mechanical model developed from virtual internal bond（VIB）.It is deemed that the material particles in microscopic are connected with virtual normal bond and shear bond or with normal bond possessing normal and shear stiffness.The macro-constitutive relation in terms of bond stiffness is derived from the interaction between material particles.Owing to its ability to present the diversity of Poisson ratio,VMIB can be applied to more extensive engineering materials.The heterogeneous material,e.g.rock,is composed of different components.The mechanical property varies with location.In order to model the heterogeneous material,thereafter,to simulate its fracture process,the heterogeneity is primarily incorporated into VMIB.The heterogeneous material is assumed to consist of unit cells in which the virtual bonds are spatially randomly distributed.To represent the heterogeneity,the mechanical property of unit cells is assumed to be randomly distributed,which leads to a heterogeneity property on the integrated material level.However,the bond stiffness in a certain unit cell is assumed to be uniform,which leads to a homogeneity property on the cell level.To examine the performance of the presented method,the fracture process of a specimen subjected to confining stress is simulated.In the case where the rock is treated as a homogeneous solid,a run-through shear fracture is observed and the trace of fracture is regular while in the case that the rock is treated as a heterogeneous solid.Many fractures are observed to simultaneously initiate randomly in different locations;and then propagate and finally coalesce.But the general trend is of shear failure.The simulation results show that the presented method could simulate the fracture processes of heterogeneous rocks and primarily reflect the effect of heterogeneity on the failure behaviors of heterogeneous rocks.