压缩条件下不同形状玄武岩柱破裂机理数值模拟研究

Abstract

摘要: 压缩条件下,不同形状玄武岩柱的强度和变形存在差异,且其破裂机理和破坏模式亦存在区别。本文构建不同形状的玄武岩柱图像,然后将细观损伤力学、统计强度理论、连续介质力学相结合,基于RFPA$^{\rm 3D}$-CT软件的数字图像处理,将玄武岩柱图像转化为有限元网格模型,并分别赋予节理、岩石的材料力学参数,其中,考虑节理及岩石的非均质性。进一步开展不同侧压条件下的玄武岩柱数值试验,以研究其强度和变形特性,及其破裂机理与破坏模式。研究表明：对于侧压0 MPa的情况,尺寸1.5 m$\times$3 m,3 m$\times$3 m,6 m$\times$3 m的玄武岩柱的抗压强度随柱体倾角的增加大致呈U型分布;对于侧压6 MPa的情况,尺寸1.5 m$\times$3 m,3 m$\times$3 m,6 m$\times$3 m的玄武岩柱的抗压强度随柱体倾角的增加大致呈V型分布。分别以尺寸1.5 m$\times$3 m,6 m$\times$3 m,柱体倾角$\beta $为15$^\circ$和45$^\circ$的玄武岩柱为例,研究其在不同侧压条件下的破裂机理及破坏模式,分析了加载过程中应力集中、裂纹萌生、扩展、破碎带形成的全过程,以及声发射特征。

The strengths and deformations of columnar jointed basalts (CJBs) with different shapes are different under compression, and the fracture mechanisms and failure patterns are also different. In this paper, the images of CJBs with different shapes are constructed. Then, by combining meso-damage mechanics, statistical strength theory and continuum mechanics, the images of CJBs are transformed into finite element mesh models based on RFPA$^{\rm 3D}$-CT digital image processing, and mechanical parameters of joints and rock materials are assigned respectively, in which the heterogeneity of joints and rock is considered. Further, numerical tests of CJBs under different lateral pressures are carried out to study their strength and deformation characteristics, fracture mechanisms and failure patterns. The results show that for the case under the lateral pressure of 0~MPa, the compressive strength of CJBs (with dimensions of 1.5~m$\times$3~m, 3~m$\times$3~m and 6~m$\times$3~m) generally exhibits U-shaped distribution with the increase of column dip angle; under the lateral pressure of 6~MPa, the compressive strength generally exhibits V-shaped distribution with the increase of column dip angle. For CJBs with dimensions of 1.5~m$\times$3~m and 6~m$\times$3~m, and column dip angles of $\beta=15^\circ$ and $\beta=45^\circ$, the fracture mechanisms and failure patterns under different lateral pressures are studied. The whole processes of stress concentration, crack initiation, propagation, fracture strip zone formation and acoustic emission characteristics are analyzed.