深基坑前排倾斜双排桩设计与施工技术研究

Research on Design and Construction Technology of Front Pile Inclined of Double-row Piles in Deep Foundation Excavation

介绍了一种新的支护形式--前排倾斜双排桩,总结了该支护形式的结构性状、设计与施工技术。相对于常规双排桩,因前排倾斜桩可承受轴向力,可起到一定支撑作用,更有受力优势。性状上,后桩桩身位移小于前桩、弯矩略大于前桩,支护位移最大点不在桩顶;当桩径和倾角一定时,增加前后桩桩长、缩小桩间距、缩短连梁,都可提高支护效果。若前桩进入底部硬层土,对支护效果提高更为明显。介绍了设计中需重点考虑的问题,采用全套管全回转钻机结合旋挖钻机斜成孔施工,形成成桩全过程套管护壁并最终回收,采用双层钢筋笼等专项技术解决成桩中的特殊工艺问题。

This paper introduces a new form of support“front pile inclined of double-row piles”,the technical contents of the structural traits,design and construction of the support are summarized.Compared with the conventional double-row pile,the front pile inclined piles can bear the axial force and play a certain supporting role,and the support has more advantages.In the trait,the displacement of the rear pile is smaller than that of the front pile and the bending moment is slightly larger than the front pile,and the maximum displacement of the support is not at the top of the pile.When the pile diameter and the inclination angle are fixed,increasing the length of the pile,reducing the spacing of the piles,and shortening the coupling beam can improve the supporting effect.If the front pile enters the bottom hard layer soil,the effect of support is more obvious.The front pile reinforcement is mainly considered to be subjected to bending and shearing,and the axial bearing is mainly composed of soil layer bearing capacity.During the construction,full casing full rotary rig and conventional rotary rig are used for oblique hole construction,forming the whole process of casing into the wall and finally recycling,special techniques such as double-layer steel cages are used to solve special process problems in piles.