昆明景成大厦大直径超长灌注桩设计及承载特性研究

Study on design and bearing characteristics of large-diameter and super-long cast-in-place piles in Jingcheng Tower in Kunming

介绍昆明景成大厦的大直径超长灌注桩设计、轴力测试及单桩竖向抗压静载试验等情况,根据测试结果对单桩承载特性进行分析,研究大直径超长灌注桩极限侧阻力、端阻力分布及不同荷载水平下侧阻力、端阻力的发挥情况,以及后注浆工艺对单桩承载力的影响,并对试桩采用双套筒方式消除无效桩段的效果进行了分析。研究表明,由于超长桩的桩身压缩量较大使下部桩变形量偏小,导致下部桩侧阻力和端阻力不能充分发挥;采用后注浆工艺可显著提高超长灌注桩承载力,增大注浆量可提高超长灌注桩承载力并可改变桩侧阻力和端阻力的分布,采用在桩端部和下段进行后注浆可提高超长灌注桩端部承载力的发挥效率,并提出超长桩的静载试验不宜以总沉降量作为终止加载条件。

The design,axial force test and vertical compression static load test of large-diameter and super-long cast-in-place piles in Jingcheng Tower in Kunming were introduced.According to the test results,the bearing characteristics of the single pile were analyzed,and the ultimate lateral resistance and end resistance distribution of large-diameter and super-long cast-in-place pile under different load levels were studied,and the influence of post grouting technology on the bearing capacity of single pile was studied.The effect of eliminating invalid pile section of the test pile was analyzed by double sleeve method.The results show that the lateral resistance and end resistance of the super-long pile cannot be fully exerted due to the smaller deformation of the lower pile than that of the super-long pile;the bearing capacity of the super-long cast-in-place pile can be significantly improved by using post grouting technology,and the bearing capacity of the super-long cast-in-place pile can be improved by increasing the grouting amount,and the distribution of the lateral resistance and end resistance can be changed.It is suggested that the total settlement should not be taken as the end loading condition in the static load test of super-long piles.