长江某大桥高峰岸锚碇基坑边坡应力变形及支护效果数值模拟分析

Numerical Simulation Analysis of Stress Deformation and Anchoring Support Effect of Foundation Pit Slope for One Bridge on Gaofeng Bank of Yangtze River

依据工程地质资料及锚碇基坑支护设计方案,利用ANSYS软件构建长江某大桥锚碇基坑的三维地质概化模型,将模型导入FLAC3D中模拟分析了锚碇基坑开挖支护全过程中的应力、变形及塑性区演变特征。结果表明:基坑开挖过程中,岩体应力集中现象相对较轻,整体以压应力为主,分布较均匀;开挖后基坑的整体变形趋势是向上向临空面回弹变形,底板最大综合位移为14.7 mm,边坡最大变形出现在北侧反倾向边坡,变形值8.65 mm;塑性区体积持续增大,仅在最后一级开挖时有所降低;开挖完成后,基坑北侧的岩体内出现大量塑性区。与单一锚杆支护方案相比,锚杆+锚索支护方案北侧高边坡岩体变形平均减小16.6%,开挖完成后塑性区体积减小8600 m^(3),最大分布深度从15 m减小到5 m。锚杆+锚索支护方案不仅较好地抑制北坡变形,而且有效减小岩体内塑性区分布深度,提高岩体稳定性,基坑边坡支护效果更好。

Based on the engineering geological data and the anchoring support scheme for a foundation pit,a three-dimensional geological generalization model was constructed with ANSYS software for the foundation pit of one bridge over the Yangtze River.This model was then imported into FLAC3D to simulate and analyze the stress,deformation and plastic zone evolution characteristics of the foundation pit during the process of excavation and anchoring support.The results show that during the excavation of the foundation pit,the rock mass is generally subjected to well-distributed compression,with less concentrated stress.After excavation,the foundation pit generally appears to have an upward rebound deformation,with the displacement of bottom plate maximally reaching 14.7 mm.It is shown that the counter-trend slope on the north side has the maximum deformation up to 8.65 mm.The volume of the plastic zone continues to increase,and then decreases during the excavation of the last step.After the excavation is completed,a large number of plastic zones appear in the rock mass on the north side of the foundation pit.Compared to the support scheme with only anchor rods,the support with anchor rods together with anchor cables can make the deformation of the rock mass of slope on the north side reduced by 16.6%on average,as well as the volume of plastic zone reduced by about 8600 m^(3) and the distribution depth reduced from 15 m to 5 m after excavation is completed.It is concluded that the support scheme with both anchor bolts and anchor cables can not only effectively suppress the deformation of the slope on the north side,but also effectively reduce the distribution depth of plastic zone in the rock mass and improve the stability of rock mass,presenting better support effect for the foundation pit slope.