水中超深大沉井施工期间侧压力现场监测研究

On-site monitoring of lateral pressure of ultra-deep large and subaqueous open caisson during construction

以目前世界规模最大沉井基础——沪通大桥29~#沉井的施工为背景,对沉井整个施工过程开展现场监测试验,分析监测数据,得出朗肯静止土压力理论和规范算法与实测数据相比存在较大误差。采用折线分布推算也因侧压力影响因素较多,分布规律复杂,所得结果较差。再分别对沉井下沉和接高施工期间侧压力的大小和分布特性的影响因素进行研究,得出了侧压力在沉井下沉阶段和接高阶段的主要影响因素为沉井倾斜、沉井埋深、外井壁台阶设置和压力松弛影响范围。通过对比分析,对各种因素的产生原因和影响机制进行了说明。在消除沉井倾斜对水中超深大沉井侧压力影响后,确定了侧压力在沉井侧壁上沿深度的分布形式,并建立侧摩阻力计算模型。

On the basis of construction of the No.29 open caisson of Hutong Bridge,which is the largest open caisson in the world,in-site monitoring tests were carried out on the entire process of the open caisson construction.By analyzing the monitoring data,it is concluded that results predicted by Rankine’s theory of stationary earth pressure and its normative algorithm are significantly different from the measured data.The result of polyline distribution projection is not satisfactory because there are many influencing factors of lateral pressure and its distribution is complicated.Then,the influencing factors on the size and distribution of lateral pressure during the sinking and subsequent construction of caisson are studied.It is concluded that the main influencing factors of the lateral pressure during the sinking stage and the heightening stage are the slant of caisson,the depth of caisson,the step setting of caisson sidewall and the range of pressure relaxation.The causes and mechanism of various factors are explained based on comparison and analysis.The distribution of lateral pressure along the vertical caisson sidewall and the side frictional resistance calculation model are determined after eliminating the effect of the caisson slant on the lateral pressure of the ultra-deep large and subaqueous open caisson.