基于Cosserat理论的柱状节理岩体各向异性本构模型研究

STUDY OF ANISOTROPIC CONSTITUTIVE MODEL OF COLUMNAR JOINTED ROCK MASSES BASED ON COSSERAT THEORY

针对白鹤滩柱状节理岩体的各向异性力学特性,引入三棱柱和四棱柱概化模型,采用Cosserat理论和Goodman当量叠加原理,基于一组节理岩体的微观介质体,得到其Cosserat扩展介质本构关系;然后将其用节理法向刚度和切向刚度简化处理,并叠加到空间三维Cosserat介质本构关系中,建立宏观意义上的四棱柱和三棱柱柱状节理本构模型;最后基于FLAC3D,将Cosserat各向异性本构模型用于白鹤滩柱状节理岩层隧道开挖数值模拟中,并对比分析各向同性和各向异性条件下围岩开挖各阶段应力–应变的差异及对工程的影响。相比各向同性本构模型,Cosserat各向异性本构模型3个方向上的应力相差较大,更能反映工程实际,对工程优化设计有着重要的意义。

According to anisotropic mechanical properties of Baihetan columnar jointed rock masses,triangular and quadrangular prism generalized models were introduced. Based on microscopic media of a group of jointed rock masses,Cosserat extended constitutive equation was obtained by using Cosserat theory and Goodman equivalent superposition principle. Triangular and quadrangular prism columnar jointed constitutive models were established. At last,by using FLAC3D,Cosserat anisotropic constitutive model was applied to tunnel excavation numerical simulation of Baihetan columnar jointed rock masses. Variations in stresses and strains at different excavation stages and influences on engineering were comparative analyzed under isotropic and anisotropic conditions. Comparing with isotropic constitutive model,stresses in three directions of Cosserat anisotropic constitutive model have larger differences;it can reflect engineering reality better;and it is more important for design optimization of engineering.