某大桥锚碇基坑三维应力变形分析

Three Dimensional Analyses for Stress and Deformation of Anchorage Foundation Pit of Bridge

利用ANSYS软件建立某大桥锚碇基坑的三维地质概化模型,并导入FLAC^(3D)中对锚碇基坑开挖全过程进行数值仿真,分析锚碇基坑开挖过程中的应力变形规律。结果表明,基坑开挖期间,岩体应力分布较规律,拉应力区域范围较小、量值不大,岩体受力情况良好;岩体主要向临空面变形,最大变形量为10 mm;基坑开挖后因产生临空面,在坑口周围的覆盖层内分布有塑性区,随着基坑开挖,部分塑性区岩体被挖除,塑性区整体体积有所减少;基坑边坡岩体稳定性良好,支护结构内力较小,远低于锚杆设计承载力。

A three⁃dimensional geological model was established for an anchorage foundation pit of a bridge by using ANSYS software,and the whole excavation process of anchorage foundation pit was numerically simulated in FLAC^(3D) to analyze the law of stress and deformation in the excavation process of anchorage foundation pit.The results show that the rock mass has the stress in a regular distribution during the excavation of foundation pit,the tensile stress being relatively lower and distributed within a small area,showing that it is in a good stress condition.The rock mass has the deformation mainly occurring in its free face,with a maximum value of 10 mm.Furthermore,there are plastic zones distributed in the overburden around the pit mouth because of free face generated after excavation.Subsequently,part of the rock mass in the plastic zone is removed during the excavation of the foundation pit.As a result,the overall volume of the plastic zones is reduced.It is found that the rock mass at the slope of the foundation pit is in a good stable condition,with the internal force of the supporting structure being far lower than the designed bearing capacity of the anchor bolt.