二元地层超深基坑桩锚撑组合支护轴力报警与变形协调分析

Analysis on Axial Force Alarm and Deformation Coordination of Combined Support of Pile,Anchor Bolt and Bracingfor Super-deep Foundation Pit in Binary Stratum

二元地层中超深基坑采用两种不同刚度的支护结构时会产生变形协调问题,特别是采用吊脚桩加锚喷支护时,其属于上刚下柔的支护结构,在分析其整体变形、局部变形和支撑内力时,采用不同的模拟计算方法对施工等各方面均影响较大。文章以国内首个深层隧道中的某个超深基坑为研究背景,分析了国内相关领域的技术成果,当采用两种以上支护方式时,该结构的变形计算和支撑轴力计算将变得更复杂,当采用分开计算时,支撑轴力往往偏小,在施工时常常引起轴力报警。文章结合工程实例,通过采用分开建模和整体建模两种方式进行数值模拟,得出结论如下:当采用刚度不同的支护形式进行组合支护时,刚性结构与柔性结构结合部位的变形协调对支撑轴力影响较大;通过采用整体建模与分开建模相结合的方法,总结提出了修正刚柔体系过渡段变形协调产生附加内力的计算新思路,对类似工程有借鉴意义。

In order to solve the problem of deformation coordination of supporting structures with two kinds of stiffness in the super-deep foundation pit in the binary stratum,especially the supporting structure with upper rigid part and lower flexible part when using suspension pile and anchor shotcrete support,different simulation calculation methods to analyze the overall deformation,local deformation and support internal force have great influence on construction and other aspects.Taking certain super-deep foundation pit of the first deep tunnel in China as the background,this paper analyzes some technical achievements of related fields,and finds that the calculations of the structural deformation and the axial force of support become very complex if more than two support methods are adopted,the axial force of support is often small if separate calculation is adopted,which often causes axial force alarm during construction.Based on the engineering example,the separate modeling and the overall modeling are used to simulate the numerical simulation,and it come to the following conclusions:the deformation compatability of the rigid structure and the flexible structure in joint part has a great influence on the support axial force if the combined support forms with different stiffness are adopted.A new calculation method of correcting additional internal forces caused by deformation compatability of the transition section of rigid system and flexible system is summarized by combining the integral modeling with the separate modeling.