【作者】 彭建宇；

【导师】 张延庆；

【作者基本信息】 北京工业大学 ， 结构工程， 2004， 硕士

【摘要】 摘要 挤扩支盘灌注桩是一种新型桩，是在原有等截面钻孔灌注桩的基础上发展而来的。该桩利用桩身不同部位的硬土层设置分支或承力盘, 将摩擦桩变革为变截面多支点摩擦端承桩, 改变了桩的受力机理，使桩的承载力大大提高,沉降变形显著减小。 本文重点研究了挤扩设备挤压土体形成承力盘的力学过程和该过程对桩周围土体的影响范围。考虑土应力-应变关系的非线性，假设挤土臂上的土压力服从二次抛物线分布；考虑土的回弹性，假设挤土臂与土体的接触长度满足公式x=l[(90－α)/90]1/2。在以上假设的基础上建立了挤扩装置工作时的力学模型，得出了挤扩装置作用力和挤土臂土压应力的关系式。利用圆柱孔扩张理论分析了承力盘挤扩过程，通过计算得到了不同挤扩张角下的塑性区范围开展图，并得出结论：（1）单向挤扩时，承力盘以下土体受到充分挤压，能有效提高支盘桩的竖向承载力；（2）双向挤扩时，承力盘水平方向土体受到充分挤压，能有效提高支盘桩的横向承载力。 运用大型有限差分计算软件 FLAC-2D 对挤扩过程进行了数值模拟分析。根据挤密效应试验资料建立了挤扩过程数值计算模型，得到了承力盘挤扩成型后对桩周土的影响范围:（1）单向挤扩时，桩周土挤密效应的影响范围在水平方向达到1.8m，尤其在 0.9m 内挤密效果显著；竖向方向挤密效应的影响范围为承力盘以下 1.4m,承力盘以上 0.7m，尤其在盘下 0.6m 以内挤密效果显著。（2） 双向挤扩时，桩周土挤密效应的影响范围在水平方向达到 2.5m，在 1.3m 范围内挤密效果显著；竖直方向挤密效应影响范围达到 1.1m。 理论分析和数值模拟结果与试验数据吻合较好，说明本理论模型符合工程实际情况，为今后进一步研究奠定了基础。更多还原

【Abstract】 As a type of new pile, the squeezed pile with expanded branches orplates is developed on top of the traditional cast-in-place pile. In thisapproach, the hard soil layers around different parts of the pile areutilized to form branches or plates to turn a friction pile into amulti-fulcrum, end bearing one. By changing the mechanism of bearing ofthe pile, the capability of bearing is improved significantly while thesettlement of the pile decreases dramatically. This paper focuses on our study of the squeezing process as well asthe suffering area of the soil surrounding the pile in the process ofsqueezing. Considereding the non-linearity of soil, we supposed that thepressure on the squeezing arms obey the law of two-times-paraboladistributing;Considering the flexibility of soil, we gave the formula ofthe contact length,namely (x=l[(90－α)/90]1/2).Based on two assumptionsabove, we built the mechanic model for the squeezing equipment and derivedthe mechanic parameter expressions . We then applied the Columnar HoleExpansion Theory to the squeezing process to analyze the influence on soilaround the branches or plates in two different squeezing processes,one-side and two-side squeezing. For both cases, we plotted the plasticarea as a function of the expanding angle. Finally, we came to thefollowing conclusions: 1. One-side squeezing process can significantlyimprove the vertical load because the soil under the plates has been fullysqueezed; 2. Two-side squeezing process can significantly improve thelateral load because the soil about the plates has been well squeezed. Finally, we simulated the squeezing process using the software of FLAC.According to the date derived from squeezing effect experiment, we builtthe numerical calculating model for the squeezing equipment,and got thesuffering area after squeezing process..For one-side squeezing,theimpact area reaches 1.8m in the level direction and,especially, the soilwithin 0.9m is well squeezed; In the vertical direction, the inpact areareaches 1.4m under the plate and 0.7m on top of it.For two-sidesqueezing,the impact area reaches 2.5m in the level direction and the soilwithin 1.3m is fully squeezed;In the vertical direction,the impact areareaches 1.1m. The experimental result of the squeezing effect matches well with theconclusions drawn from the theoretical analysis thus it verified that ourmechanical models are correct and it is a good beginning for deep researchin the future.更多还原