【作者】 江浩；

【导师】 汪稔；

【作者基本信息】 中国科学院研究生院（武汉岩土力学研究所） ， 岩土工程， 2009， 博士

【摘要】 钙质砂是一种海洋生物成因的特殊岩土介质,在我国主要分布在南海诸岛海域,由于其物理力学性质的特殊性,钙质砂中桩基工程有着特殊的承载性状。在过去几十年里,在钙质砂地层上设计和建造海洋石油平台已经成为海洋工程中一个重大的科技挑战。在不同碳酸钙含量和胶结度钙质砂地层上的桩基工程建设中,基于其他材料上的传统经验已经被证明是不适用的。因此,本文通过室内模型试验和理论分析相结合的方法对钙质砂中桩基承载性状进行了系统的研究。1.阐述了取自南沙群岛永暑礁附近海域钙质砂独特的基本物理性质和测量方法,并对模型试验所用钙质砂以及作为对比试验所用石英砂的物理力学参数进行了分析。详细介绍了模型试验中模型箱、模型桩基的设计和制作,以及试验所采用的量测设备、加载方案和数据处理方法。2.对钙质砂中单桩和群桩分别进行了室内模型试验,对比研究了桩端开、闭口和不同相对密度情况下的桩基承载和变形性能及其影响因素。并通过与石英砂中桩基模型试验结果的对比,重点揭示了钙质砂中单桩、群桩与石英砂中承载特性及荷载传递的特有规律,并得到了桩侧阻力、桩端阻力的发挥模式。3.结合国内外研究资料和室内模型试验结果,从桩侧阻力、桩端阻力以及群桩效应等几个方面,对钙质砂中的桩基承载性状进行了深入的研究。4.考虑到钙质砂桩侧摩阻力的深度效应,在前人的研究基础上,建议桩侧传递函数采用三折线模型,桩端传递函数采用双折线模型,提出了钙质砂单桩荷载沉降传递计算模型,并详细推导了单桩在轴向荷载作用下的荷载-沉降解析解。更多还原

【Abstract】 Calcareous sand is a special marine geotechnical medium, which is widely spread throughout the oceans near Nansha Islands. Since its unexpected physical and mechanical properties, pile foundations in calcareous sands have lots of particular behavior. During the past 30 years, the design and construction of offshore oil platforms founded in calcareous sands have been a major technical challenge for the offshore industry. The traditional practice, successfully used for other types of materials, proved to be ineffective when used for pile foundations driven into calcareous sands. In this thesis, based on the existing theory, the bearing behavior of pile foundations in calcareous sands is systematically studied by means of laboratory testing and theoretical analysis.1. The special physical properties and measurement methods of calcareous sands are introduced first, which are taken from the Yongshu coral reefs in Nansha Islands in South China Sea. The physical and mechanical parameters of calcareous sands and silica sands, which are used in model tests, are analysed. Model test equipment is introduced, which includes the design and construction of model chamber and model pile groups. The measurement equipment and test program used in model tests are also explained.2. Model pile and pile groups tests with open or close ended are carried out to investigate the bearing and deformation characteristics in calcareous sands with different relative density. In contrast to the tests with silica sands, the difference in the bearing capacity behavior and load transfer of piles between calcareous sands and silica sands, are emphasized in the analysis. The action laws of pile end resistance and shaft friction are obtained.3. Based on research data and model test result, the bearing behavior of piles in calcareous sands is analyzed, which includes pile end resistance, shaft friction and the effect of pile group.4. Considering the depth effect of shaft friction of pile in calcareous sands, a set of analytical solutions for the axial loading-settlement curve of pile in calcareous sands is established. Three fold-lines model is used in the load transfer functions of pile shaft, and the load transfer functions of pile end uses two fold-lines model.更多还原