深基坑开挖时既有管网的支护方法与管线保护

基坑开挖中,在满足基坑侧壁强度要求的前提下,如何降低对既有管线的扰动是施工中急需解决的关键问题。以某供热管线工程为背景,通过建立深基坑开挖过程遇到的几种管线计算模型,计算得到了基坑侧壁与管线在应力、位移等方面的变化规律。结果表明:垂直穿越基坑的管线支护前变形方式为U型,采用悬吊支护后为W型,采用简支支护方式后为VVV型,支护后应力变为原来的1/10~1/7;基坑侧壁水平位移随开挖深度的增加先减小后增大再减小,位移最大处发生在管涵的正下方;采用工字钢桩+横向支撑侧壁、简支管涵后,侧壁水平位移由125.43 mm减小为20.53 mm。所提出的方法既符合现场施工要求,又有效控制了既有管线的变形,起到了很好的保护作用。

Supporting method and pipeline protection for existed pipe network in deep foundation excavation

During the foundation pit excavation, how to reduce the disturbance to the existed pipeline is a key problem to be solved urgently under the premise of meeting the supporting requirement of foundation pit. Based on a heat pipeline project, several pipeline models in the deep foundation pit excavation are established to obtain the stress and displacement change regularity of sidewall and pipeline. When the pipeline crosses the foundation pit horizontally, the deformation mode before support was U-shaped, and then it changed to W-shaped under suspension support, and the deformation mode became VVV-shape under simply support, and the stress is 1/10~1/7 times of the original. The horizontal displacement of pit sidewall decreased at first, then increased and finally decreased again with the excavation depth increasing, and the maximum displacement occurred beneath the pipe culvert. Using the steel I-piles + lateral support for side wall and simply support for pipe culvert, the horizontal displacement of the side wall reduced from 125.43 mm to 20.53 mm. The proposed method not only can meet the requirements of on-site construction, but also effectively can control the deformation of existing pipeline.