苏彦 周记名 谭维佳

摘 要：为提升后注浆超长钻孔灌注桩的承载性能，以静载试验数据为基础，对3根后注浆超长钻孔灌注桩的桩侧阻力、桩身轴力以及荷载-沉降等因素进行了系统分析。通过拟合Q-S曲线预测了单桩极限承载力，并利用有限元模型分析了桩端注浆桩单桩承载力的影响因素。研究表明，1）桩端注浆超长桩的Q-S曲线变形缓慢;2）桩身荷载主要由下部土层决定;3）桩侧摩阻力的产生与桩土相对位移有着紧密的联系;4）3种函数的拟合效果均较好，得到的极限承载力差距不大;5）桩端持力层为粉砂时注浆效果较好，注浆量对极限承载力的影响较小。研究结果可为此类工程的后注浆超长钻孔灌注桩的设计及施工提供一定的借鉴。

关键词：地基基础工程;桩端注浆;超长桩;现场足尺试验;拟合预测;数值分析

中图分类号：U473.1   文献标识码：A

DOI： 10.7535/hbgykj.2021yx02010

Research on ultimate bearing capacity of end-grouting super-long

cast-in-place pile

SU Yan1，ZHOU Jiming2，TAN Weijia3

（1.Tianjin Huatie Engineering Consulting Company Limited， Tianjin  300202， China;2. China Civil Engineering Construction Corporation，Beijing 100038，China;3. College of Geological Engineering and Survey，Chang′an University，Xi′an，Shaanxi 710054，China）

Abstract：

In order to improve the bearing capacity of the post-grouting super-long bored cast-in-place piles， on the basis of the static load test data， the influence factors of side resistance， axial force and load settlement of the three post-grouting super-long bored cast-in-place piles were analyzed systematically. The ultimate bearing capacity of single pile was predicted by fitting the Q-S curves， and the factors influencing the single pile bearing capacity of end-grouting piles were analyzed by finite element model. The results show that： 1）the Q-S curves of the super-long piles with pile end grouting are slowly deformed;2）the load of the pile body is mainly determined by the lower soil layer;3） the generation of the side friction of the pile is closely related to the relative displacement of the pile and soil; 4） the fitting effects of the three functions are good， and the difference of the ultimate bearing capacity is not significant; 5） when the bearing layer of pile end is silty sand， the grouting effect is better， and the effect of grouting quantity on ultimate bearing capacity is small. The conclusions can provide some guidance for the design and construction of post-grouting super-long bored cast-in-place pile in similar projects.

Keywords：

foundation engineering; pile end grouting; super-long pile; full-scale test in site; fitting prediction; numerical analysis

為了提高超高层建筑的单桩承载力，超长桩后注浆技术在工程中得到了越来越广泛的应用[1-5]。吴江斌等[6]在充分调研上海地区桩端后注浆灌注桩的工程现状的基础上，分析得到了合理注浆量，并提出桩端后注浆灌注桩在软土地区的承载力计算方法;杨生彬等[7]对后压浆钻孔灌注桩做了大量动荷载和静荷载的对比试验，不仅提高了试验的精度，提高了单桩承载力的预测准确性;朱向荣等[8]提出与地质条件相适应的相关技术参数，推动了桩端后压浆技术的发展;

黄生根等[9]对苏州大桥进行了大量平衡静载试验，分析得出桩端压浆既可以改良桩和桩周土体接触面的性质，也可以提高桩端阻力。……