球状风化孤石群内端承桩复合成孔施工技术

Composite Construction Technology of Boring for End-bearing Pile in Spherical Weathered Boulders

摘要:

在深圳地铁4号线403标，需要在高强度、各向异性、大倾角等特性的球状风化花岗岩孤石群地层中进行端承桩成孔，成孔与周围建筑物距离仅约20 m，且一幢建筑物已严重倾斜，鉴定判断已属于危房等级，经多次论证，最终采用对周边环境影响较小的回转钻孔工艺。先后采用刮刀钻头切削钻进、球齿滚刀钻头碾压钻进、套筒取心钻头环切纠偏等多种钻孔措施相结合的复合钻孔工艺，配以反循环泥浆护壁进行钻孔施工，取得成功。该项技术可为类似地质条件桩基成孔提供良好的技术支持。

Abstract:

In 403 section of Shenzhen metro Line 4, borehole should be completed for end-bearing pile in spherical weathered granite with high strength, anisotropy and large inclined angle, which was only 20m to nearby buildings, so rotary drilling was adopted for safety. Composite drilling technology of drag bit cutting drilling, button roller bit compacting and rectification by annular coring bit was adopted with wall protection by slurry reverse circulation.