超长大直径钻孔灌注桩自平衡法试验研究——以海峡西岸某标志性建筑为案例

Experimental study on self balance method of super long and large diameter bored pile——Take a landmark building on the west coast of the Strait as an example

海峡西岸某标志性超高层建筑桩基础采用超长大直径钻孔灌注桩,试验桩桩长达90m^103m,桩径1300mm,设计砼强度水下C50,采用了自平衡试桩法静载试验,设计要求的最大加载值高达55 000kN。通过自平衡法试验、桩身内力测试、钻芯法等检测方法,测到单桩竖向抗压极限承载力、各土层桩身侧阻力和混凝土试件抗压强度检测值等参数,并基此深入分析了桩基破坏模式、桩身侧摩阻力的发挥、桩端承载性状、桩身混凝土抗压强度等。研究结果认为,自平衡法静载试验相较于传统的静载试验具有不受场地条件影响等诸多明显优势,为超长大直径灌注桩的承载力试验提供了一种相对可靠的直接试验方法。同时,建议福建省尽快出台有地区代表性的芯样强度折算系数。

A landmark super high-rise building on the west side of the straits adopts extra long and large diameter bored pile as pile foundation. The length of the test piles is 90-103 m,the diameter of the piles is 1300 mm,and the design concrete strength is C50 under water. The self-balance test method is used for static load test,and the maximum load value required by the design is 55000 k N. In this paper,the ultimate bearing capacity of vertical compression of single pile,the side resistance of pile body in each soil layer and concrete compressive strength are obtained by self-balance test,internal force test of pile body and compressive test. The failure mode of pile foundation,the exertion of side friction resistance of pile body,the bearing behavior of pile end,and the compressive strength of concrete of pile body are analyzed in depth. The results show that compared with the traditional static load test,the self balanced static load test has many obvious advantages,such as not affected by the site conditions. It provides a relatively reliable direct test method for the bearing capacity test of super long and large diameter cast-in-place pile. At the same time,it is suggested that Fujian Province should issue the strength conversion coefficient of concrete core samples with regional representation as soon as possible.