压缩条件下玄武岩柱各向异性及破裂机理数值模拟研究

Numerical Simulation of Anisotropy and Fracture Mechanism of Columnar Jointed Basalts Under Compression

构建不同柱体倾角的玄武岩柱图像,基于RFPA^(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,开展单轴压缩及围压条件下的玄武岩柱数值试验,研究其强度和变形的各向异性,及其破裂机理与破坏模式。研究表明:对于围压0 MPa~8MPa的情况,玄武岩柱试件的抗压强度随柱体倾角的增加大致呈U型分布;随着围压的增加,各柱体倾角的试件抗压强度有较明显的提升;在不同围压条件下,抗压强度的最小值,出现在β=30°的位置。以柱体倾角β=15°、45°的玄武岩柱为例,研究其在单轴及围压条件下的渐进破裂机理;并研究围压8 MPa条件下不同柱体倾角玄武岩柱的损伤破裂特征。

In this paper images of columnar jointed basalts(CJBs)with different dip angles are constructed,and then based on digital image processing of RFPA^(3D)-CT software,CJBs images are transformed into finite element mesh models,and material mechanical parameters of joint and rock are given respectively.Numerical tests of CJBs under uniaxial compression and confining pressure are carried out to analyze the anisotropy of strength and deformation,as well as the fracture mechanism and failure mode.The results are as follows.When the confining pressure is between 0 MPa and8 MPa,the compressive strength of CJBs is distributed in approximately U-shaped trend with the increase of column dip angle;with the increase of confining pressure,the compressive strength of the specimens with different dip angles of column is obviously improved.The minimum compressive strength under different confining pressure conditions appears inβ=30°.Taking CJBs withβ=15°and 45°as an example,the progressive fracture mechanisms under uniaxial compression and confining pressure are discussed.In addition,the damage and fracture characteristics of CJBs with different dip angles under confining pressure of 8 MPa are analyzed as well.