【作者】 周淼；

【导师】 王立忠；

【作者基本信息】 浙江大学 ， 岩土工程， 2005， 硕士

【摘要】 土的结构性是决定软土工程特性的一个内在因素，开展软土结构性方面的试验和理论研究对进一步弄清软土地基的固结沉降特性是非常重要。我国东南沿海地区广泛分布海相淤泥，在该地区桩基础是被普遍采用的处理大型工程软基的常用方法。而当桩周土的沉降大于桩基的沉积时，就会在桩身产生负摩阻和显著的下拉荷载。本文从土体结构性的角度，探讨了结构性软土地基及其扰动的固结性状，并对位于结构性软土地基中的桩基负摩阻性状进行了分析，用于指导工程实践，具有重要的理论和工程意义。 首先，介绍了天然结构性软土的工程特性及其研究现状，并结合温州粘土的薄壁土样固结压缩试验结果，介绍了原状土的固结和压缩性状，加压率对其性状的影响及原位压缩曲线校正方法。 其次，结合结构性软土压缩特性研究，提出了扰动土的原位压缩曲线校正方法，通过运用多层地基一维固结解析解和迭代法，建立了能考虑土体结构性和土体自重的非线性一维固结问题的半解析方法，通过详细的计算，得到了结构性软土的孔压消散曲线和固结度随时间变化曲线，揭示了结构性软土地基的一维固结沉降规律及地基扰动对固结和最终沉降量的影响。在此基础上建立了能综合考虑荷载、土的成层性和自重等因素的的成层结构性软土地基的固结控制方程，分析了变荷载下成层结构性软土地基一维固结性状。 最后，将结构性软土地基固结沉降的求解运用到位于结构性软土地基中的桩基负摩阻力求解中来，并结合天然结构性软土中静止土压力系数K₀及泊松比v特性研究成果探讨了考虑结构性的桩基负摩阻力性状。本文最后介绍了桩基负摩阻力的试验研究成果，分析了不同的成桩工艺对桩基负摩阻力的影响。更多还原

【Abstract】 Since the soil structure characteristic is an intrinsic determinative factor of soft clay engineering property, it is necessary that experiment and theory research on the soft clay structure characteristic be carried on in order to explain the consolidation settlement property of the soft clay ground. Soft clay extensively distributing near the littoral in Southeast China, and pile foundations are in common use in improving the soft ground of large-scale engineering buile in this area. Negative skin friction will develop whenever the adjacent soil settles more than the pile.The magnitude of downdrag can be quite significant. In this dissertation, the study of one dimensional consolidataion behaviour of structured soil and evaluation of the distrubance effect and behaviour of negative skin friction should be based on the study of structured soft clay in order to guide the practice in reason.First, the engineering characteristics of natural clay and the research actuality are introduced. Based on the results of laboratory tests of Wenzhou clay, the relation between structure character and mechanical properties of structured soft soil is examined. The different compressibility of undisturbed soil and remolded soil is compared, and the effect of the rate of loading on the compressibility is analyzed. The method to predict the virgin compressibility curve is introduced.Second, according to the compressibility of structured soft soil ,a method to predict the field compression curve of disturbed soil is developed. Based on the general analytical solution and iterative methods available for the problem of one-dimensional consolidation of layered soils, the semi-analytical solution for one dimensional non-linear soil consolidation considering the structure and self-weight is presented. The computed results about the pore pressure and the degree of consolidation demonstrate the difference between the behavior of undisturbed and disturbed structural soft soils. The corresponding governing equation are presented, in which the influences such as time dependent loading, layered soils and actual overburden pressure are taken into consideration. The behavior of layered structured soft soil under time-dependentloading is discussed.Finally, The solution for negative skin friction based on the solution of layered structuredsoft soil consolidation considering the characteristic of K0 and Poisson ratio is presented.Then, the behavior of negative skin friction is discussed. Lastly ,The study result of tests of negative skin friction are introduced, the influence of the construction technology on negative friction is proposed.更多还原