大断面箱涵下穿高速公路过程的施工监测分析

 郑州—开封(郑开)城市通道下穿京港澳高速公路工程中，顶进箱涵机动车道外廓尺寸为46.8 m×9.3 m(宽×高)，当时其宽度为国内第一。在高速公路路面和箱涵布置大量监测点，重点对路面位移和箱涵顶进姿态进行监测。监测成果表明：在路面西侧测点的最终沉降值中，第一节箱涵推进后的阶段性沉降值占一半以上，南区测点超过60%，北区测点超过54%；箱涵顶进高速公路的3/4时，路面两端位移开始加速。分析认为，路面变形较大原因之一在于覆盖层薄、箱涵断面尺寸大以及地质条件差等工程特征，之二为一些设计意图未能在施工中落实，主要体现在管棚和滑行轨道的施工效果上。对箱涵顶进过程中箱涵本身和周边环境的监测信息进行深入分析，可为今后类似工程提供借鉴。

ANALYSIS OF CONSTRUCTION MONITORING OF LARGE-SECTION BOX CULVERT JACKING PROCESS UNDERPASS EXPRESSWAY

There is a large-section box culvert jacking underpass expressway in Zhengzhou—Kaifeng city access project with the largest section size in China. Systematic monitoring work is arranged for the project，the deformation on expressway and the box posture control are focused on the whole jacking process. Monitoring results show that over half of total settlements appear after the first box section underpass on west side expressway；the southern region is over 60% and the northern region is over 54%；while the box culvert is jacked into the 3/4 width of the expressway，the deformation on expressway begins to speed up on both ends. Analysis shows that engineering characteristics such as thin coverage，large-section and unfavourable geological conditions are the main factors leading to large deformation on expressway；the fact that design idea has not been carried out in jacking process increases the deformation on expressway，which leads to poor quality in construction of pipe shed and pilot draft. By analysing the monitoring information of the box and the surrounding environment，some reference can be achieved in similar projects in the future.