【作者】 崔杰；

【导师】 门福录；

【作者基本信息】 中国地震局工程力学研究所 ， 岩土工程， 2002， 博士

【摘要】 饱水介质中的波传播和砂土液化是地震工程和岩土工程中两个重要的问题。本论文就这些问题做了一些研究工作，内容如下： (1)简要回顾了在不变形介质的前提下二维地下水的波动问题的研究成果。然后在可变形介质的前提下，直接从两相介质动力方程出发，对含水土层中的波动问题进行了研究。编制了可考虑弹塑性、非线性本构关系、剪胀性、刚度退化等各种因素的影响的计算程序。通过计算对各种土壤刚度、渗透条件、边界透水条件、荷载形式、本构关系和不均匀性等情况做了比较研究，发现了一些新规律和新现象。并对它们做了一些讨论和分析。 (2)对不含水土层分层排列、饱水土层分层排列、不含水土层与饱水土层分层交错排列情况下对波传播和地面运动的影响做了一些研究，考虑到土壤的剪胀性、线性和非线性本构关系，刚度退化等因素，编制了可适用上述各种情况和任意多土层(包括含水或不含水、力学性质不同、厚度不同、边界连续条件不同等)，在不同基底输入或上边界输入作用下的通用分析程序，通过对相当数量的典型情况进行的分析计算，得到了一些趋势性的认识，特别是对饱水与不含水土层分层交错情况，取得了一些新认识。 (3)基于两相介质理论，提出了一种新的从机制上可更合理地解释砂土液化的数理分析方法。该方法可同时考虑到土—水相互作用，惯性力，水渗流，和各种非线性影响因素在内，把剪胀做为使土—水相互运动的动因，并可同时求解出土、水的运动和应力状态。通过一系列数值计算，分析了剪胀、本构关系、刚度退化、土层厚度、孔隙率、边界条件等对液化的影响，编制了计算程序。 (4)首先介绍了提出Rayleigh波是液化主因的背景，基于宏观震害资料的启示，提出了Rayleigh波可能是造成砂土液化的主要动因的新见解。并用单相介质模型的总应力法，分析了Rayleigh波可能产生的应力大小。进一步，基于两相介质理论的有效应力法，研究了Rayleigh波在饱水介质中的传播情况，给出了Rayleigh方程，分析了饱水介质中产生的应力，并同单相介质模型的结果做了对比，证实了Rayleigh波较S波可产生较大的剪应力和法向应力梯度，从而导致液化的论断。 (5)利用基于剪切波速的砂土液化判别法，提出了一种可考虑剪切波速的随机性和液化及液化危害等级的模糊性的液化和液化危害等级的判别一法。讨论了当剪切波速具有随机性时液化的发生概率，进而给出了确定场地液化和危害程度的发生概率，在此基础上，结合液化和液化危害程度 （等级）的模糊性，利用模糊事件的概率分析方法，提出了可同时考虑随机性和模糊性场地液化和液化危害性的发生概率的计算方法。 比）通过应用 Seed提出的自由场地液化分析方法和 Meek，Wolf等人提出的锥体动力学模型，提出了一种可用于分析结构物地基液化的简化分析方法，并用有限元分析法做了对比分析，结果符合的很好。同时，还提出I一种可分析结构物地基沉降的分析方法，该法把沉降分为三个部分，即：（1）由于地震循环剪切荷载产生的体积压缩而产生的沉降；（2）由于地震的动剪形变产生的沉降；（3）由于土壤模量软化和重力产生的沉降。上述用于分析液化和沉降的简化方法便于计算，物理意义明确，具有一定的工程上可接受的精度，有明显的实用价值。更多还原

【Abstract】 Wave propagation in saturated soil and sand liquefaction are two important subjects in earthquake engineering and geotechnical engineering. In this dissertation, after making a short review of the state-of-the-art of studies on the topics, the author present the study results, which include the following contents:(1) After simply reviewing the research results of two-dimensional wave propagation in the non-deformable porous media, a series of studies on wave propagation in the deformable porous saturated soil layers are made. They include compiling a computer program which permits to incorporate various constitutive relation of soil skeleton, dilatancy, stiffness deterioration etc. Comparative studies are made for various cases of soil stiffness, resistance of percolation, drain condition on boundary, loading form, constitutive relation, and stratification. As a consequence, some new trends and phenomena are discovered.(2) Some studies are made for the subject of various effects on wave propagation and ground motion of multi-dry, multi-saturated, and alternate dry and saturated soil layers. A comprehensive computer program is compiled, accounting for soil dilatancy, linear and non-linear constitutive relation, rigidity degradation and suiting to any combinations of soil layers, dry and/or saturated with different thicknesses, properties, continuity conditions at interfaces, and inputs at base and top boundaries. From the numerical results obtained for a quite large number of typical cases, some knowledge of general trends of response for, especially, the cases of alternate dry and saturated soil layers are gained both quantitatively and qualitatively. Therefore, some conclusions and suggestions are presented.(3) A new approach being able to provide more thorough understanding of the mechanism of soil liquefaction is presented. The approach consists of accounting for the soil-water interaction, regarding the dilatancy as a source term enabling relative motion between soil and water to occur, and simultaneously solving these equations to obtain the details of development of the stress and motion of soil and water. After some numerical analyses, the effects of dilatancy, constitutive relation, rigidity degradation, thickness, properties, continuity conditions at interfaces are analyzed.(4) An introduction of the background that makes us present this study is made. Based on some macroscopic evidences gained in actual earthquake fields and on a preliminary theoretical analysis, it has been pointed out that the Rayleigh waves should be an essential cause of liquefaction for the fields beyond the epicentralregion with saturated sand deposits at shallow depths. After the simple analyses with the single phased media theory, a more detailed analyses has been done, based on two phased media theory, on Rayleigh wave propagation in saturated soil. The new results show that Rayleigh wave will really cause larger shear stress and pore pressure than S wave in shallow layers and thus easily induce sand liquefaction.(5) Based on an empirical formula, in terms of soil shear velocity, to evaluate soil liquefaction, which is simple to handle and prospective in further application, the author presents, in the probabilistic and fuzzy way, the formulae for the evaluation of liquefaction probability and fuzzy probability at given depths and for a fuzzy evaluation of liquefaction hazard of the total soil layers. A probabilistic liquefaction index and a fuzzy probabilistic liquefaction index are tentatively suggested to show approximately the liquefaction hazard of soil layer in an indeterministical way,(6) By taking the advantage of Seed’s simplified method for free ground sites and of the cone model concept well developed by Meek and Wolf in dynamics in recent years, a new simplified method is presented on the basis of a review of the limited number of literature in respect of model tests and finite element analysis on the sand liquefaction evaluation of subsoil of buildings. It is concluded that the effec更多还原