基于改进遍布节理模型的岩石基坑开挖稳定性数值分析

Stability Analysis of Rock Foundation Pit Excavation Based on Improved Ubiquitous-joint Model

为解决现有研究针对开挖于层状岩体中且边坡含高倾角外倾结构面的岩石深基坑开挖稳定性的研究相对欠缺问题,依托徐州地铁3号线南三环站基坑工程,通过对FLAC3D中既有遍布节理模型的改进,得到了可同时考虑层状岩体变形和强度各向异性的横观各向同性弹塑性遍布节理模型。基于该本构模型采用数值模拟方法对不同岩层倾角下基坑及围护结构的变形特点进行了模拟分析。结果表明:地面沉降最大值和围护桩的最大水平位移均受岩层倾角影响,当岩层倾角为50°时上述量值最大。为定量分析岩层倾角影响下围护桩的变形规律,对模拟结果进行了数据拟合,获得了围护桩最大变形与岩层倾角的理论关系。强度折减计算结果表明,岩层倾角为50°时基坑开挖完成后的安全系数最低,并获得了不同岩层倾角下基坑开挖完成后边坡的安全系数分布及基坑边坡的潜在破坏面形式,给出了依托工程的围护桩的桩间距优化建议。

In order to address the relative lack of research on the stability of deep foundation pit excavation in layered rock mass with slopes containing high inclination and external inclined structural planes,based on the foundation pit project of the South Third Ring Station of Xuzhou Metro Line 3,a transversely isotropic elastic-plastic ubiquitous joint model was obtained by improving the existing ubiquitous joint model in FLAC 3D,which could comprehensively consider both deformation and strength anisotropy of layered rock mass.With the adoption of the constitutive model,deformations of foundation pit and retaining structure under different rock dip angles were simulated and analyzed,the results manifest that both the maximum value of ground settlement and the maximum horizontal displacement of retaining piles are affected by the dip angle of rock stratum,with the two values achieving the maximum under the dip angle of 50°.Additionally,with the aim to quantitatively analyze the deformation law of retaining piles under the influence of various rock dip angles,data fitting was performed on the simulation results,the theoretical relationship between the maximum deformation of retaining pile and the dip angle of rock stratum was obtained.The strength reduction calculation results show that the safety factor is the lowest when the dip angle of rock is 50°,the distribution of safety factors and potential failure surface forms of the slope after excavation of the foundation pit under different rock strata inclination angles are obtained,and the optimization suggestions for the spacing of retaining piles are given.