大鳌特大桥深水大直径变截面桩基施工技术研究

Construction Technology of the Large Diameter and Variable Cross-section Foundation in Deep Water for the Muzhou-Da'ao Extral-large Bridge

深水大直径变截面钻孔灌注桩施工中,常出现变直径段桩轴线偏心严重、多层钢筋笼使变截面处部分砼保护层偏薄、灌筑工艺不精细使变截面处砼松散及桩底外围沉淀超规范等质量缺陷。本文通过大鳌特大桥深水大直径变截面桩基施工实践,采取了变截面段加导向环成孔技术、PHP泥浆泥沙分离循环系统、灌筑混凝土技术等方法,取得了全部桩基达I桩的效果。

In the construction of large diameter and variable cross-section drilled grouting piles,some quality defects are often occurred,such as the serious axial eccentricity of the variable diameter section,parts of thin concrete protective layers occurred due to multi-layer reinforcement cage,loose concrete at the variable section caused by crude pouring technology,and the outer layer sedimentation of pile foundation is out of standard. Based on the construction practice of large diameter and variable cross-section foundation in deep water for the Muzhou-Da'ao Extral-large Bridge,some methods are taken such as hole forming technology with guiding ring at the variable cross-section,PHP mud and sediment separation-recycle system,pouring concrete technology,which achieves an effect of all pile foundations reach the first grade level.