基坑双排管桩与盖板接头开裂原因分析及优化研究

Analysis and Optimization on the Causes of Cracking of Double-row Pipe Pile and Cover Joint in Foundation Pit

珠江三角洲某双排管桩基坑支护结构,在基坑开挖过程中发现盖板出现沿基坑边线方向开展的裂缝。为深入研究基坑开挖后双排管桩与盖板相互影响的受力特性、开裂原因及裂缝控制措施,本文采用ABAQUS有限元软件对该工程进行数值模拟计算,并根据不同荷载工况,分析管桩与盖板连接处的应力分布和变化的规律,探讨盖板开裂的原因,提出合理控制盖板开裂的改良措施。研究结果表明:盖板中严重受拉区域主要分布在前排桩前表面与盖板连接处和前排桩上方的盖板上表面,受拉应力最大值始终位于前排桩前表面与盖板连接处,内部钢筋较大应力值主要分布在后排桩;盖板开裂的直接原因在于前排管桩发生较大变形,由节点连接处传递变形挤压盖板;通过调整管桩桩顶锚入盖板深度与采用暗梁钢筋布置两项改良措施,可起到有效降低应力、控制裂缝的作用。

A double-row pipe pile pit support structure in the Pearl River Delta was found to have cracks in the cover plate developed along the direction of the pit edge during the excavation of the pit.In order to study the stress character-istics,cracking causes and crack control measures of the interaction between the double-row pipe pile and cover after the excavation of the pit,numerical simulation calculation of the project was carried out by ABAQUS finite element software,and according to different loading conditions,the stress distribution and changes in the connection between the pipe pile and the cover were analyzed,the causes of cover cracking were explored,and the improvement measures for reasonable control of cover cracking were proposed.The results show that:the severe tensile area in the cover is mainly distributed in the connection between the front surface of the front pile and the cover and the upper surface of the cover above the front pile;the maximum value of tensile stress is always located in the connection between the front surface of the front pile and the cover;the larger stress value of internal reinforcement is mainly distributed in the rear pile;the direct cause of the cover cracking is the large deformation of the front pipe pile and the extrusion of the cover by the transfer of deformation at the node connection;by adjusting the depth of the top of the pipe pile anchored into the cover by adjusting the depth of the top pile anchored into the cover and adopting two improvement measures,it can effectively reduce the stress and control the cracks.