基坑抢险斜撑撑脚稳定性模型实验及数值分析

Model Test and Numerical Analysis of Stability of Diagonal Brace Foot for Emergency Reinforcement of Foundation Excavation

在既有基坑工程实践中经常采用钢管斜撑对变形达到预警值的基坑侧壁进行抢险支护,能够获得较好的加固效果。但其支护的承载能力往往受到斜撑撑脚地基土体的稳定性所控制。针对基坑抢险工程中常用的无基座斜撑撑脚稳定性问题开展了室内物理模型试验研究。并对不同埋置深度的斜撑撑脚地基进行了试验加载和数值分析研究,获得了荷载位移曲线和地基土变形特征,并据此讨论了斜撑撑脚地基承载机理及破坏模式。当撑脚埋置深度较浅时,撑脚地基土体容易发生被动土压力破坏;当撑脚埋置大于一定深度时,撑脚地基承载力才能得到有效发挥。研究结果建议在实际工程应用中要确保斜撑撑脚有2倍管径以上的埋置深度。

The steel pipe diagonal brace is often used to rescue and protect the sidewall of the excavation when the ground deformation reaches the alert threshold.However,its bearing capacity depends on the stability of the ground close to the diagonal brace foot.A series physical model tests were conducted to study the stability of the diagonal brace foot.Experimental loading tests and numerical analysis were carried out on the diagonal brace foot with different embedding depths,the load-displacement curves and the deformation characteristics of the ground soil were obtained.Based on this,the bearing mechanism and failure modes of the diagonal brace foot were studied.When the embedding depth of the brace foot is shallow,the ground close to the brace foot is trend to be the passive failure state.When the depth is larger than a certain value,the bearing capacity of the diagonal brace foot can then be fully activated.The results of the experimental and numerical studies suggest that in engineering applications,it is necessary to ensure that the brace foot has an embedding depth of larger than 2 times the pipe diameter.