既有涵洞回填区桥梁群桩旋挖钻成孔施工技术研究

Research on the Construction Technology of Bridge Group Piles in the Backfilling Area of Existing Culverts by Rotary Drilling

重庆市高新区沿山大道一期Ⅲ标段高腾立交A匝道桥11#墩柱位于市政道路既有涵洞回填区,墩柱基础为4根嵌岩桩基,采用旋挖钻干法作业成孔时因遭遇沙土层和地下水,3根桩基在孔口以下6~13.5m范围发生塌孔。根据实际揭露的水文地质情况,通过对比钢护筒、泥浆护壁、混凝土回填护壁3种处理方案的工期、经济效益,选择“素混凝土回填护壁”方法对塌孔进行了处理,历时17天,完成11#墩柱桩基施工。经第三方检测,处理后的桩基混凝土强度、桩身完整性等指标均满足设计及规范要求,为今后既有涵洞回填区桥梁群桩旋挖钻成孔施工提供了一定的经验。

The 11#pier column of Gaoteng Interchange A Ramp Bridge in Section III of Yanshan Avenue Phase I of Chongqing High tech Zone is located in the backfill area of existing culverts on municipal roads.The foundation of the pier column is composed of 4 rock embedded pile foundations.When using the rotary drilling method to form holes,due to encountering sand and soil layers and groundwater,3 pile foundations collapsed within 6~13.5m below the hole mouth.Based on the actual revealed hydrogeological conditions,by comparing the construction period and economic benefits of three treatment schemes:steel casing,mud wall protection,and concrete backfill wall protection,the“plain concrete backfill wall protection”method was selected to treat the collapsed hole.It took 17 days to complete the construction of the 11#pier column pile foundation.After third-party testing,the processed pile foundation concrete strength,pile body integrity and other indicators meet the design and specification requirements,providing some experience for the future construction of bridge group piles in the backfill area of existing culverts through rotary drilling.