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根据单桩静载试验和基础沉降实测资料表明:超长单桩在设计工作荷载作用下的桩顶沉降量St主要为桩身混凝土压缩量Ss,且侧阻力很大,端阻力发挥很小。超长单桩上部黏性土中桩侧摩阻力充分发挥所需的桩土极限相对位移约17～20 mm。当桩土相对位移大于该极限位移后,桩上部土层发生桩土滑移呈现侧阻软化现象。群桩基础的沉降随着施工荷载水平的增加而增大。其规律为:施工层数很低时(5层以下),主裙楼一体沉降;随着主楼施工层数(8层后)增加,主楼沉降增大,同时由于主楼的“促沉”作用会使得裙楼沉降得以延续;随着主楼施工层数(30层后)继续增加,由于主楼核心筒相对裙楼沉降较大引起的对裙楼的“牵拉作用”会使裙楼出现轻微上翘的现象,但由于总体沉降量较小,所以裙楼、主楼、主楼核心筒的角点和边点沉降值相差不大。群桩效应沉降比Rs随着荷载水平(施工层数)的增大而先增大后减小。
According to the measured data of single pile static load test and foundation subsidence, it shows that the settlement of pile top St is mainly Ss of pile concrete compression with large lateral resistance and little end resistance. The relative displacement of pile-soil limit required for full exertion of pile-side frictional resistance in the upper cohesive soil of overlength single pile is about 17-20 mm. When the relative displacement of pile-soil is greater than this limit displacement, the pile-soil slip occurs in the upper soil layer of the pile and softens. Settlement of pile foundation increases with the increase of construction load. The law is as follows: when the number of construction layers is very low (less than 5 floors), the main podium will settle together; with the increase of the number of main building (after 8 floors), the main building will increase in settlement; meanwhile, With the main building construction layer (after 30 layers) continue to increase, due to the main building core podium relative to the settlement of the podium caused by the podium of the “pull effect” will make the podium However, due to the small total settlement, the difference between the corner point and the edge point settlement value of the podium, main building and main building core tube is not big. The settlement ratio Rs of pile groups firstly increases and then decreases with the increase of load level (the number of construction layers).