【作者】 樊向阳；

【导师】 黄宏伟； 顾国荣；

【作者基本信息】 同济大学 ， 结构工程， 2007， 博士

【摘要】 桩基础是土木工程常用的基础形式之一。静压桩由于其诸多优点而在软土地基城市建设中获得日益广泛的应用。然而,由于受桩型选择和设备选型等因素的影响,静压桩在施工前要对其沉桩阻力进行估算,评价沉桩可能性;另外,静压桩都是挤土桩,部分工程施工前要分析沉桩挤土效应的影响,并提出防护措施的建议。从前人的探索可以看到,沉桩阻力和沉桩挤土效应涉及到多方面的理论,是非常复杂的。虽然有不少学者提出了各自的见解,尤其在沉桩挤土方面,给出了不少计算方法或计算公式,但因受计算过程复杂,计算参数多且难以确定等不同因素的影响,迄今为止,还没有一个普遍适用的计算方法或计算公式来指导静压桩设计与施工,这也成了制约静压桩发展的主要因素。本文本着“从实践中来,到实践中去”的原则,收集了大量的工程资料,进行了部分原型试验,在总结前人研究的基础上,运用理论分析、数值分析、计算机模拟等技术,对沉桩阻力和沉桩挤土效应开展了进一步的研究。主要工作和取得的成果有:1.充分利用国内外已有研究成果,对沉桩阻力的影响因素及变化规律进行了详尽的研究,得出了以静力触探比贯入阻力作为主要参数的估算沉桩阻力的经验公式。考虑到沉桩过程中土体被扰动,公式中引入了土体灵敏度的概念,并给出了上海地区常见粘性土层的土体灵敏度推荐值。利用大量的工程实测资料和试验资料,对本文公式进行了验证,同时给出了估算后期沉桩阻力的方法,以及用其它参数估算沉桩阻力的公式。2.建立了估算沉桩阻力的人工神经网络模型,用大量工程实测数据对模型进行了训练,并对拟合结果进行了验证。分析表明,用人工神经网络模拟沉桩阻力简便可行,是有一种估算沉桩阻力的有效方法,可以与用经验公式估算的沉桩阻力相互补充,相互校核。3.运用大量工程资料,得出了上海地区不同地层组合中静压桩沉桩阻力与单桩极限承载力的相互关系。通过大量试验数据,从单桩承载力时效性的角度,给出了单桩极限承载力与沉桩阻力及休止期的相互关系。4.利用Segaseta的源—源(汇)理论,得出了饱和软粘土中沉桩挤土效应引起的地表位移的计算公式,并根据不同的影响因素对计算结果进行修正。通过大量工程实测资料,给出了不同修正系数的计算方法和取值范围。最后提出了一些合适的沉桩挤土效应防治措施。5.编制了计算沉桩阻力和沉桩挤土效应的应用软件。软件操作简单,计算结果以计算书的形式输出,避免了繁琐的数据计算,使用非常方便。更多还原

【Abstract】 Pile foundation is one of the basic foundation forms widely used in the civil engineering. Static-press piling has been used in the groundsill building for many of its advantages. Taking into account the choice of pile and equipment type, the pile-sinking resistance must be estimated and the probability of pile-sinking should be evaluated before the construction. In addition, with analyzing the affect of pile-sinking compaction effect, the defending suggestions also need to be put forward before the construction. The previous studies indicated that the pile-sinking resistance and the pile-sinking compaction effect related to various theories and are complicated. Although many insights, especially the calculating methods and formula from the aspect of the pile-sinking compaction, were brought forward by the previous scholars, up to the present, no universal calculating method or formula for guiding the design and construction of the static-press piling has been obtained.Based on abundance engineering datum and partly archetype experiments, further study of the pile-sinking resistance and the pile-sinking compaction effect was carried out in this study with the techniques such as theoretically analysis, numerical analysis and computer simulation. The main conclusions are as follows:1. Taking full advantage of the previous study results, detailed investigation on the affecting factors and variation rules of the pile-sinking resistance was carried out. An experimental formula for calculating the pile-sinking resistance was achieved by taking the specific penetration resistance of static cone penetration test as the main parameters. Considering the disturbing of the soil during the pile-sinking, the concept of the soil sensitive was introduced and also the recommendatory value of the soil sensitive for the clay layers in Shanghai area was presented. The formula in this study was validated by using large numbers of actual engineering datum and experimental datum, and also the method of evaluating the pile-sinking resistance and the formula of evaluating the pile-sinking resistance with other parameters was offered.2. An artificial neural network model for evaluating the pile-sinking resistance was established and trained with large numbers of actual engineering datum. The modeling result was also validated. It indicates that the artificial neural network modeling the pile-sinking resistance is an easy, feasible and effective way to evaluate the pile-sinking resistance. It can be reinforced and tested each other with the result evaluating by the experimental formula.3. Based on abundance engineering datum, the correlation between the pile-sinking resistance of static-press piling and the ultimate bearing capacity of single pile in the different strata combination in Shanghai area was obtained. From the aspect of bearing capacity of single pile’ time-dependent, the correlation of the bearing capacity of single pile, the pile-sinking resistance and resting time was also presented by large amount of experimental datum.4. The formula for calculating the surface displacement caused by the pile-sinking compaction effect in the saturated soft clay was acquired by using the Segaseta’s source-source (or confluence) theory, and the results was also corrected according to different affective factors. At the same time, the calculating methods and value ranges for different correctional coefficients were listed. Finally, some useful defending suggestions for the pile-sinking compaction effect were provided.5. The software using to calculate the pile-sinking resistance and the pile-sinking compaction effect was compiled. It is easily operated and the results are outputted by calculation report format, which avoids complicated calculation.更多还原