深厚淤泥土层大型沉井基础下沉阻力研究

为了解深厚淤泥土层中大型沉井基础下沉阻力的分布特征,以温州瓯江北口大桥(主桥为主跨800m的三塔钢桁梁悬索桥)为背景,对中塔沉井基础下沉阻力监测数据进行分析,研究侧壁土压力、底面支承反力分布规律,以及刃脚底面反力与静力触探指标之间相关性。结果表明:淤泥土地层中施工的大型沉井基础,其侧壁压力沿深度方向近似线性增长,其值略大于相同深度位置的水土自重压力;沉井刃脚底面及斜面的反力值在底口入土一定深度后保持稳定,刃脚底面与斜面反力的比值为1.8~2.2,相对稳定;刃脚底面反力值与静力触探试验的锥尖阻力具有较高的相关性,在沉井底口中心下沉到一定深度后,其比值为1.4~2.2。

Study of Resistances to Large Caisson Sinking in Thick Clay Layer

To examine the distribution property of resistant forces to large caisson sinking in thick clay layer,the Oujiang North Estuary Bridge in Wenzhou,a three-tower steel truss girder suspension bridge with a main span of 800 m,is taken as the background project.The monitored resistant forces to the sinking of central pylon caisson was analyzed,the lateral soil pressure on the caisson wall and distribution property of reactions in the caisson base as well as the correlation between the reactions in the base of the cutting edges and those from the cone penetration test were studied.The results show that for the large caisson foundation located in clays,the lateral soil pressure on caisson wall shows sign of quasi-linear increasing along the depth direction,which is slightly bigger than the pressure generated by self-weight of water and soil at the locations with the same depth.The reactions in the base and slant faces of cutting edges tended to be constant after the caisson base immersed in the clay layer to a certain depth,with a ratio from 1.8 to 2.2,relatively stable.A high correlation between the reactions in the base of cutting edges and those from cone penetration test was observed.When the center of the caisson base sunk to a specified depth,the correlation ratio was within the range of 1.4 to 2.2.