【作者】 徐亮；

【导师】 朱大勇；

【作者基本信息】 合肥工业大学 ， 建筑与土木工程（专业学位）， 2020， 硕士

【摘要】 为了满足实际工程中建筑物基础的承载条件以及施工环境的要求,扩底抗拔桩作为一种变截面桩,通过增大抗拔桩在桩端的结构尺寸,从而能较大幅度的提高其极限承载力。因此,对于抗拔桩的承载力及工作性能的研究与探讨具有重要意义。基于此本文对砂土中桩的抗拔承载特性进行以下研究:(1)本文首先设计了室内抗拔试验的加载装置及试验方案,对两根等截面试验桩进行室内抗拔试验,试验条件等其他变量均相同仅桩径不同,测定在每级上拔荷载作用下桩身稳定时桩顶的竖向位移,得出了抗拔桩的桩径越大,极限抗拔承载力越大,且承载性能更优的结论。介绍了几种常用的等截面抗拔桩理论计算模型,带入各项试验参数得出抗拔桩极限承载力的理论计算结果,并与试验结果进行对比分析。(2)对不同类型的扩底抗拔桩进行了室内抗拔试验,分别研究探讨了在桩径、扩大端上部的开展角及埋置深度不同的条件下,桩顶荷载-位移(Q-S)曲线、桩身轴力分布曲线、桩侧平均摩阻力分布特点。结果表明,增加桩的埋深对提高扩底桩的承载力效果显著,埋深较深与埋深浅相比极限承载力提高了55.6%,桩径与扩大端上部的开展角的增加,使得扩底桩的承载力提高了22.2%、27.3%。同时对比发现,扩底抗拔桩较等截面桩承载力提高了28.6%～75%,且承载性能随着桩径、桩的埋深及扩大端上部的开展角的增大而增加。(3)根据假设在极限荷载作用下的扩底抗拔桩破坏时破裂面的形状与方程,推导出扩底桩极限承载力表达式,将理论预测结果与上文室内抗拔试验的结果进行对比分析,发现当扩大端直径较大时,预测结果与试验结果相比较为符合。更多还原

【Abstract】 In order to meet the requirements of bearing conditions and construction environment of building foundation in engineering,base-enlarged tension piles,as a kind of variable section pile,can improve ultimate bearing capacity greatly and have better bearing performance by increasing the structure size of the pile at the pile end.Therefore,it is great significance to study the bearing capacity and deformation of the uplift pile.Based on this,the following researches are carried out on the uplift characteristics of piles in sand:At first,this paper designed the pull-out test of loading device and testing scheme,two equal section test piles were tested in laboratory,test conditions and other variables are the same only pile diameter were different,determination the vertical displacement of pile head when pile body under pulling load on each level is stable,it is concluded that the larger the pile diameter,the greater the ultimate uplift capacity and the better bearing capacity.This paper introduces several commonly used theoretical calculation models of equal section tensile pile,and taking various test parameters to obtain the theoretical calculation results of ultimate bearing capacity of uplift pile,and makes a comparative analysis with the test results.In this paper,the indoor tensile tests of different types of base-enlarged tension piles were carried out,and the load-displacement(Q-S)curve of pile top,axial force distribution curve of pile body and average friction resistance distribution characteristics of pile side were studied and discussed under different conditions of pile diameter,development Angle of enlarged end and buried depth of test pile.The results show that the bearing capacity of the enlarged pile can be improved significantly by increasing the pile depth,the ultimate bearing capacity can be increased by 55.6%,and the bearing capacity of the belled pile can be increased by22.2% and 27.3% by increasing the pile diameter and the developing Angle at the top of the enlarged end.At the same time,the comparison shows that the bearing capacity of the belled pile is improved by 28.6%～75% compare with the equal cross section pile,and the bearing capacity increases with the improve of the pile diameter,the buried depth of the pile and the development Angle of the upper part of the expanded end.According to hypothesis when base-enlarged tension piles damaged,the failure surface shape and equation under the ultimate load,the expression of ultimate bearingcapacity of belled pile is derived,the theoretical prediction results compare with indoor pull-out test results of the above analysis.It is found that when the diameter of the expanded end is larger,the predicted results are more consistent with the experimental results.更多还原