静压钢管桩在砂性土持力层承载特性分析

Analysis of Bearing Characteristics of Static Pressure Steel Pipe in Sandy Soil Bearing Layer

为探究钢管桩端地基土发生流砂破坏对单桩承载力的影响规律,开展了桩端地基土流砂破坏监测和不同龄期下单桩静载试验研究。文章以苏州某高层建筑地基加固纠偏项目为工程依托,对钢管桩现场静载试验结果和地基土流砂破坏情况进行分析,并定量分析了钢管桩端流砂破坏对单桩承载力的影响程度,结果表明:钢管桩休止期28 d内桩端砂性持力层地基土发生流砂破坏是单桩承载力增长不大的主要原因,试验12根钢管桩内流砂破坏土塞高度增加0.09 m~0.43 m,平均增长高度为0.26 m,但休止期内单桩承载力却增长不大。砂性土作为静压钢管桩桩端持力层易发生管涌或流砂,引起建筑物发生蠕变变形,采用桩端注浆的方式增加单桩承载力的同时,还可抑制建筑后期沉降。

To investigate the influence of sand flow failure on the bearing capacity of single pile,the monitoring of sand flow failure and static load test of single pile at different ages were carried out.Based on the foundation reinforcement and rectifying project of a high-rise building in Suzhou,the static load test results of steel pipe pile and the damage of flowing sand in foundation soil are analyzed,and the influence degree of flowing sand damage at the end of steel pipe pile on the bearing capacity of single pile is quantitatively analyzed.The results show that the main reason for the small increase of the bearing capacity of a single pile is the flow sand failure in the foundation soil of the sand-bearing layer at the end of the steel pipe pile within 28 d of the rest period.The plug height of the flow sand failure in 12 steel pipe piles increases by 0.09-0.43 m,and the average increase height is 0.26 m.However,the bearing capacity of single pile does not increase much during resting period.Sand soil,as the pile end bearing layer of static pressure steel pipe pile,is prone to piping or flowing sand,which causes creep deformation of the building.The pile end grouting method can increase the bearing capacity of single pile and restrain the settlement of building.