软岩地基中大直径布袋桩抗拔试验研究

Experimental study of large-diameter bag uplift pile in soft rock foundation

西北地区深大基础工程日益增多,兼顾基础抗浮和耐久性问题的研究空白,借助西宁火车站综合改造工程,引入大直径布袋桩技术,有效解决了基础抗浮和耐久性问题;选择6根试桩进行了现场单桩抗拔载荷试验,最大加载量为9 060 k N;运用MATLAB软件分别拟合出3种抗拔极限承载力预测函数模型的曲线,同时运用PLAXIS软件对不同等级荷载桩-土位移进行模拟,并与实测的荷载-位移曲线对比分析。研究发现:双曲线和幂函数模型较适合此类抗拔桩极限承载力预测;本地区类似地基预测大直径缓变形抗拔桩极限荷载所需的极限位移标准应由0.030D减小为0.025D;仅根据土层的物理力学特征确定抗拔桩桩周土的极限摩阻力不够完善,至少还要考虑埋深不同对具有相似物理力学特征土层性质的影响。

Deep foundation engineering is increasing in northwest China. The anti floating and durability for deep foundations problem research is a blank. This paper effectively solved the anti floating and durability problem by introduction of large diameter bag pile technology to comprehensive renovation project of Xining Railway Station. The 6 piles are selected to conduct on-site single pile load test; it is shown that the maximum load weight is 9 060 k N, Using MATLAB to fit out the three prediction function models of uplift ultimate bearing capacity curve; and using PLAXIS to simulate for different grades of pile soil load displacement. The study results show that the hyperbola and exponential function models to predict ultimate bearing capacity of uplift pile are appropriate; similar foundation prediction of large diameter corrosion deformation of uplift pile ultimate load corresponding standard limit displacement should be reduced from 0.030 D to 0.025 D. The ultimate friction based only on physico-mechanical characteristics of soil to determine the anti pulling pile surrounding soil is not enough; the influence of different buried depths of similar physico-mechanical characteristics of soil should be considered.