【作者】 汪鹏程；

【导师】 朱向荣；

【作者基本信息】 浙江大学 ， 岩土工程， 2005， 博士

【摘要】 研究内容主要包括软化剪胀土中的球形(柱形)孔扩张问题和沉桩挤土效应问题。 使用变换法，获得了小应变情况下，弹塑性材料中孔扩张问题一般解，进一步推导了理想弹塑性和弹脆塑性土体中孔扩张问题的解答，另外还分析了弹脆塑性材料的弹塑性交界面两侧的速度间断。 在前人研究的基础上，假定土体为均质各向同性的弹塑脆塑性体，用应力跌落模型描述土体的应变软化，引入剪胀角来考虑土体的剪胀特性，采用双剪统一强度理论和不相关联的流动法则，获得了考虑土体软化和剪胀特性的任意变形情况下的球形(柱形)孔扩张统一解，分析了孔扩张后的体积变化，并给出了孔扩张后卸载情况下的应力和位移解答，在此基础上，分析了土性参数如弹性模量、泊松比、抗剪强度、应变软化系数、剪胀角以及考虑中间主应力影响与否、大小应变等因素对解答的影响，并将本文方法计算的极限扩张压力值与实测值进行了比较，结果吻合得很好，从而验证了该方法的合理性和可靠性。 将土体视为各向同性的弹脆塑性体，用应力跌落模型描述应变软化，采用双剪统一强度理论和不相关联的流动法则，利用0初始孔径孔在极限扩张压力作用下，塑性区位移场具有几何自相似的特性，推导了极限扩张压力的精确相似解。 假定桩沉入时桩尖附近土体按球形孔扩张，以无限空间中球形孔扩张解为基础，借助源源和源汇的手段，模拟了在半无限空间中的沉桩挤土问题，获得沉桩挤土位移场的半数值解。 对沉桩后桩周土体中的超静孔压消散进行了解析分析。分析中不考虑竖直方向的变化，认为土体只在径向上固结，将问题简化为平面应变问题，但考虑了土体的黏性性质和桩体本身的半渗透性，得到了超静孔压的解析表达式，在此基础上，讨论了土的性质以及桩、土的渗透性对孔压消散的影响。 将沉桩后土中应力松弛问题简化为无限空间中无限长圆柱形孔扩张后的应力松弛问题，将土视为最一般的粘弹粘塑性材料，采用由饱依丁—汤姆逊元件和宾汉姆元件串连而成的粘弹—粘塑性模型作为沉桩后桩周土的模型，推导出桩周土中应力、粘塑性区半径等与时间的关系式，通过编制程序计算，得到了它们随时间变化的数值结果，并就有关因素对应力松弛的影响进行了讨论。 鉴于目前绝大多数用有限元法分析沉桩挤土问题都没有考虑土体剪胀性的事实，本文利用大型商用有限元软件ABAQUS，对具有应变软化和剪胀特性的土体中沉桩挤土应力场和位移场进行了性状分析，在分析中考虑了土体大变形，得出了一些规律性结论。另外，还分析了若干因素对沉桩挤土效应的影响。更多还原

【Abstract】 Cavities expansion in soils with softening and dilation and pile driving effects ware studied.By using variable transform, general solutions to cavities expansion in elastoplastic material ware obtained in case of small deformation, the solutions to cavities expansion in elastic-perfectly plastic materials and in elastic-brittle-plastic ones ware deduced.On the base of past researches, soil was assumed to be a homogeneous, isotropic and elastoplastic-brittleplastic material, stress dropping model was used to describe strain softening, a dilation angle was used to consider dilation. By using twin-shear united strength theory and non-associated flow rule, united solutions to spherical and cylindrical cavities expansion in the soils with softening, dilation and large deformation ware obtained, volume changes of the soil after expansion ware analyzed, the stresses and displacements in case of unloading after expansion ware obtained too. On these bases, some factors influencing solution results ware analyzed, and limit expansion pressures from computation ware compared with ones from survey.By making use of the characteristic of cavities expansion with zero initial radius that under limit expansion pressure, displacement field in plastic zone is self-similarity, rigorous similarity solution to limit expansion pressure was obtained.On the study of displacement after pile driving, a model of spherical cavity expansion at the pile top wile pile driving ware introduced, by making use of the solution to spherical cavity expansion and a source-source and a source-sink imaging technique, a half-numerical solution to displacement field in the soil surrounding pile ware obtained.On the premise that the problem about the excess pore pressure dissipation ware reduced to be a plane strain problem, in which the soil ware regarded as a viscoelastic material, and partially permeable characteristic of the pile was considered, a formulas of the pore pressure was obtained. Moreover, some factors influencing the porepressure penetration ware analyzed.By regarding the problem on stresses relaxation in the soil after pile driving as a plane strain problem, and assuming that the soil was a viscoelastic-viscoplastic material, formulae of the stresses and radius of the viscoplastic zone ware deduced, and by computation with program compiled by author, numerical results ware presented, moreover, several relative factors ware discussed.Famous software ABAQUS was used to analyze the stress and displacement fields due to pile driving considering softening, dilation and large strain, moreover, some factors ware discussed, and several conclusions ware presented.更多还原