逆作法中外加环箍套管控制立柱桩竖向抬升位移的设计与施工

Design and construction of the vertical lifting displacement of column pile with steel strapped casing pile in Top-down method

在逆作法施工过程中,由于结构上部荷载不断增加,立柱桩会不断地发生沉降;同时,由于上方土体不断开挖导致基坑土体产生隆起,带动立柱桩体上移,且越靠近基坑中部其抬升量越大(或沉降量越小).为控制在此种因素影响下立柱桩间的不均匀沉降,提出一种外加环箍套管法,即在立柱、立柱桩外侧加设环箍套管,且立柱、立柱桩与环箍套管间留有一定间隙,以此避免基坑土体回弹时摩擦力带动立柱、立柱桩上移.以立柱采用钢管混凝土柱、桩采用钢筋混凝土灌注桩为例,介绍了该方法的设计方法与施工技术,最后采用ANSYS软件分别对有无环箍套管的立柱桩(其他条件相同情况)进行了沉降量的模拟分析,以此验证了本文所提出方法的有效性.

During the construction of top-down method,with the load from upper structure continuously increasing,the column pile will keep settling.Meanwhile,because of the heave of soil resulted from the excavation of foundation pits,the soil beneath the foundation ditch will make the column pile move up,and more close to the center of the foundation ditch,the heave value is more bigger.For controlling the differential settlement between column pile resulted from the reason above,we put forward the method that adding steel strapped casing pile outside the solider pile,and making a little interval between them to keep them disengaged status,to avoid making the solider pile and stand column move up.In this paper,we introduce the design method and construction technology using concrete filled circular hollow section columns and drilled filling pile,and one columns upported by one pile as example.In the end,to verify the effectiveness of this method for the similar practical engineering,we would made model analysis on the settlement of the solider pile with the adding steel casing pile or not.