管幕内顶进箱涵顶部管幕承载作用的分析

上海市中环线虹许路北虹路下立交工程是目前世界上在饱和含水软土地层中施工的横截面最大的管幕法工程。根据地面沉降限制要求,并按照以较缓慢速度顶进箱涵且开挖土体过程中前方土体滑动的极端不利情况分析了顶部钢管幕的承载作用,针对钢管不同部分的受力状况不同,主要按两端固定梁以及弹性地基梁2种模型分情况对钢管的不同部分进行计算分析,并对该工程的情况进行了具体的计算。结果发现在箱涵顶进过程中,管幕起到相当大的力学作用,上覆土体的重量有一定量被顶部管幕承担而不向其下面传递,有助于提供箱涵前端网格尺寸经济而合理的设计。

SUPPORT EFFECT ANALYSIS OF UPPER PIPE-ROOF DURING A BOX CULVERT BEING PUSHED WITHIN PIPE-ROOF

Up to now,the subway crossing project through Hongxu Road is a pipe-roof project with largest cross-section box culvert in the world. It is constructed in saturated soft soil stratum in the Beihong Road located in the middle ring-road in Shanghai. Based on restrictions of ground settlement and extremely dangerous potential sliding condition on soil in front of the box culvert during the culvert being pushed slowly and some soil being excavated,support effect of upper pipe-proof is analyzed in order that mechanical characteristics of the pipe-roof can be completely known. Because different segments of these pipes have different mechanical status,they are analyzed mainly by supported beam model with two fixed ends and beam on elastic foundation model. Support effect of the upper and middle pipe is analyzed in detail in the practical project. The results show that the pipe-roof plays an important mechanical role in the course of the culvert being pushed. It can support quite a little weight of soil on it so that only partial weight will transfer to the stratum under it. So the pipe-roof can be benefit for economic and rational design of steel grids inverted in the front of the culvert for stabilizing the cutting surface.