【作者】 乔燕燕；

【导师】 牛志荣；

【作者基本信息】 太原理工大学 ， 岩土工程， 2010， 硕士

【摘要】 在21世纪的今天,桩基的施工技术不断地更新和改进,正朝着低公害工法桩方向、扩孔桩方向、异型桩方向、埋入式桩方向、组合式工艺桩方向、高强度桩方向以及多种桩身材料等方向发展。在这种发展趋势下,浙江天海管桩有限公司提出了一种新型的桩基础——新型带肋预应力管桩,基于桩-土接触面积来提高单桩承载力,可以通过静压置入土体,接桩头时采用机械快速接技术取消了焊接接桩,有着施工方便、成桩质量稳定、噪音低等优点。作为一种相对较新的桩型,目前新型带肋预应力管桩这项新技术尽管工程实践效果明显,但整体上仍处于技术开发和推广应用阶段,理论上缺乏系统地研究。与传统预应力管桩相比,桩体外侧加设了环状凸肋和纵状凸肋。因此,研究肋部构造尺寸变化对沉降的影响规律,可以为今后工程施工、设计提供合理的依据。本文基于现场静载荷试验,结合日本的竹节桩的研究,对新型带肋预应力管桩的单桩沉降进行探讨。本文主要作了以下研究:1、在总结单桩沉降计算方法的基础上,结合《建筑桩基技术规范》(JGJ94-2008),考虑桩径影响的Mindlin解计算地基土附加应力,基于弹性理论法,推导出竖向荷载作用下新型带肋预应力管桩的沉降计算公式。结合浙江杭州的两个工程实例,采用15m和24m两种不同桩长的新型带肋预应力管桩的竖向抗压静载试验结果进一步验证了推荐计算方法的适用性。并且改变环状凸肋下部宽度时,在两组对比中均发现,桩顶沉降随着环状凸肋下部宽度的增大而增大,但变化幅度越来越小。每级荷载作用下的相差趋势基本不变,相对比较稳定。最后建议在实际工程应用中环状凸肋下部宽度应小于160mm。2、以现场静载试验的地质条件为参考,运用MIDAS/GTS软件进行数值分析,改变新型带肋预应力管桩的一些参数,并对这些参数的影响作出分析。(i)环状凸肋直径的影响荷载水平较小时,环状凸肋直径对桩顶沉降的影响不太明显;荷载水平较大时,环状凸肋直径较大的新型带肋预应力管桩沉降相对较小。相同荷载水平作用下,桩顶沉降随着环状凸肋直径的增大而减小,减小的幅度也越来越大。(ii)环状凸肋间距的影响荷载水平较小时,环状凸肋间距对桩顶沉降的影响不太明显;荷载水平较大时,桩顶沉降随着环状凸肋间距的增大而增大,环状凸肋间距小于1.5m时,增大的幅度较大。环状凸肋间距大于1.5m时,桩顶沉降随着环状凸肋间距的增大仍在增大,但增大的幅度明显变小。(iii)环状凸肋下部宽度的影响当环状凸肋下部宽度超过160mm后改变环状凸肋下部宽度已经对新型带肋预应力管桩没有意义,建议工程实际应用中环状凸肋下部宽度小于160mm。荷载水平较小时,环状凸肋下部宽度对桩顶沉降的影响不太明显;荷载水平较大时,环状凸肋下部宽度的影响越来越明显,相同荷载水平作用下,桩顶沉降随着环状凸肋下部宽度的增大而增大,增大的幅度也越来越大。该结论与本文第三章中计算公式与工程实例对比分析结果基本吻合,进一步证实了计算公式的适用性。更多还原

【Abstract】 In the 21st century, the construction technology of pile foundation continues to be updated and improved in the direction of low-pollution, pile with reaming, special-shaped pile, submerged pile, portfolio constraction process pile, high-strength pile and a variety of pile body materials. In this development tendency, Zhejiang Tianhai Pipe Corporation put forward to a new type pile foundation—a new type ribbed prestress pipe, to improve the bearing capacity of single pile based on expland the pile-soil contact area. Dependent on static pressure, this pile push into soil then use mechanical trailer coupling pile extention instead of welding pile extention. Therefore it has those advantages: convenient construction, stability quality, low noise and so on.As a relatively new type pile, this prestressed ribbed pipe even though the new technology works in practice effect, but are still in the stage of technology development and application, lack of a systematic study in theory. Compared with the traditional pre-stressed pipe, pipe lateral side is added to ring-shaped convex rib and longitudinal convex rib. Therefore, researching the influence law to settlement under the change of structure dimensions can provide the reasonable basis for design and construction of future engineering. Based on the static load test,combined with the study of Japanese nodular piles, settlement of new type ribbed pretressed pipe pile is discussed in this paper. The research in this paper mainly including:1、Based on the summary of pile settlement calculation method, combining with《Technical Code for Building Pile Foundations》(JGJ94-2008) and calculating additional stress of foundation soil Mindlin stress factor considering piles diameter impact, using elastic theory method, the settlement of new type ribbed prestress pipe under vertical load were deduced. Using the two engineering examples from Hangzhou, Zhejiang, the vertical compression static load test results for new type ribbed prestress pipe with different lengths verified recommended calculation method of application any further. To change the under part length of annular flange rib of new type ribbed concrete pipe with calculation method, comparison in both groups,it is found that, the settlement is increase with the increase of the under part length of annular flange rib, but the increasing amplitude decreases. When the load is a certain level, the settlement is basically unchanged, the trend is relatively stable. Finally the paper puts forward the suggestion that practical engineering application of the under part length of annular flange rib is less than 160mm.2、Referring to geological conditions of static load test and using MIDAS/ GTS software for the numerical analysis, to change some parameters of new type ribbed concrete pipe, and to make an analysis of the influence of these parameters.(i)the effect of diameters of annular flange rib When the load level is smaller, the effect to settlement is not obvious; When the load level is higher, the settlement is relatively small if the diameter of annular flange rib is larger. Under the same load level, the deformation decreases with the increse of diameter of annular flange rib, decreasing amplitude increases.(ii)the effect of annular flange rib pitchWhen the load level is smaller, the effect to settlement is not obvious; When the load level is higher, the deformation increases with the increse of annular flange rib pitch,When annular flange rib pitch is less than 1.5 m, decreasing amplitude is larger. When annular flange rib pitch is larger than 1.5 m, the deformation still increases, but the decreasing amplitude is smaller.(iii)the effect of the under part length of annular flange ribIt is explained that the change of the under part length of annular flange rib of new type ribbed pretressed pipe is no meaning to settlement when it is larger than 160mm. It is suggest the under part length of annular flange rib is less than 160mm in the furture engineering application. When the load level is smaller, the effect to settlement is not obvious with the increase of the under part length of annular flange rib; When the load level is higher, the effect of deformation is more and more obvious with the increase of the under part length of annular flange rib, under the same load level, the deformation decreases with the under part length of annular flange rib, increasing amplitude increases.The conclusion agrees well with the third chapter about calculation formula with the engineering example analysis, further confirms the applicability of the calculation formula.更多还原