基于节理网络有限元的柱状节理岩体等效变形模量结构效应研究

Structural effect on equivalent modulus of deformation of columnar jointed rock mass with jointed finite element method

因其特殊的地质成因,柱状节理成为一种具有强烈非连续性及各向异性的特殊岩体结构。以白鹤滩水电工程设计、建设中所遇到的柱状节理玄武岩体为背景,针对柱状节理岩体的等效变形模量问题,在探讨了其结构效应表征参数的基础上,利用节理网络有限元为工具,研究各结构效应表征参数对柱状节理岩体等效变形模量的影响。研究结果表明:在柱轴线横向平面上,对于柱体不规则程度,当柱体完全不规则相对于完全规则情况,等效模量提高大约10%左右;在其他条件不变情况下,当柱体平均边长从0.1 m增加至0.5 m时,等效模量从5.36 GPa增加至23.4 GPa;对不同加载方向的研究结果表明,柱状节理在柱轴横向平面上可以视作各向同性;当节理刚度线性递增时,相应的岩体等效模量也基本符合线性递增的规律。在平行柱体轴线平面,节理组2间距越大,柱状节理岩体的等效变形模量越大;随着错距比的增加,柱状节理岩体的等效变形模量呈现先增加后减少的趋势,当错距比为50%时,节理岩体的等效变形模量取最大值;对于节理刚度的影响,与柱轴横向平面类似的,随柱体轴线平面上节理刚度的线性增加,相应的岩体模量也基本符合线性递增的规律。该研究成果与已有的现场研究成果及三维数值模型成果相比,吻合良好。说明了文中提供的研究结论具有较好的可信度及参考价值。

Due to the distinctive formation mechanism of columnar joints, columnar jointed basalt exhibits strong discontinuity and anisotropy. The columnar jointed basalt rock mass in Baihetan project is selected as a case study. The structural control effect on the equivalent modulus of deformation is discussed by using jointed finite element method（JFEM）. The results show that, on the transverse plane, the equivalent modulus of deformation increases with the column irregularity, which increases about 10% from completely irregularity to completely regularity. This trend also agrees with the increase of the column size. The equivalent modulus of deformation corresponding to a side length of 0.1 m is 5.36 GPa, and this value increases up to 23.4 GPa for a side length of 0.5 m. Columnar joints rock mass may be considered as isotropic on the transverse plane, and basically, the equivalent modulus of deformation varies correspondingly with joint stiffness. But when it comes to the longitudinal plane, the wider joint spacing of the joint set 2 is, the higher equivalent modulus of deformation is. The equivalent modulus of deformation increases firstly then decreases, and reaches its maximum value when the cross-bedding ratio is 50%. The equivalent modulus of deformation on the longitudinal plane shows a similar correspondence relationship with the joint stiffness on the transverse plane. The simulation results obtained by JFEM agree well with the existing field observations and 3D numerical studies.