Progressive failure mechanism of reinforced ground and its application to limit state design

土体加筋结构的设计方法主要基于极限平衡法，假定破坏机理的位置和形状。另外，在现行的设计方法中，假定加筋地基的破坏机理与非加筋地基相同，并根据其抗拉强度在设计计算中加入了加筋材料的影响。考虑到设计方法的未来趋势，应从经济的角度对其进行优化。这是通过“极限状态设计”的发展而实现的。此外，这种设计的新的可行性或应用应该是下一个目标。为此，有必要从变形机理和破坏机理两个方面研究加筋地基的实际性状。根据加筋效果可以认为，加筋效果与变形局部化程度(…)密切相关。本研究的目的是研究加筋地基的实际渐进破坏行为，建立有效的基于真实破坏机理的定量设计计算方法。首先，利用铝棒模拟地基进行了一系列不同长度、不同性质加固材料的模型加载试验。在载荷试验的基础上，利用图像处理技术，不仅研究了土体的承载能力，而且对土体的渐进破坏机理进行了分析。在此基础上，结合微观观测和分析结果，对加筋地基的渐进破坏机理进行了详细的探讨。并用刚塑性有限元方法对试验结果进行了分析。在分析中，新发展了加筋土模型，并考虑了几何非线性，以求得到地基的渐进性状。通过与模型试验结果的对比，验证了该方法的有效性。此外，还提出了与观测机理相适应的简化上限机制，并应用于试验案例，为加筋地基的变形局部化和渐进破坏奠定了基础。这些结果可以为今后的设计方法提供不可缺少的信息。此外，本文提出的加筋土地基分析方法对加筋土结构的承载能力具有很大的指导意义。较少

Design methods for earth reinforcement structures are mainly based on the limit equilibrium method which assumes the location and the shape of failure mechanism. In addition, in the current design method, it is assumed that the failure mechanism of the reinforced foundation ground is the same as that of non-reinforced foundation ground and the effect of reinforcing material is added in the design calculation in term of its tensile strength. Considering the future trend of the design method, it should be optimized from an economical point of view. This has been achieved by the development of "limit state design". Also, the new feasibility or application of this design should be the next target. For this purpose, it is necessary to investigate actual behavior of the reinforced foundation ground on both deformation and failure mechanism. According to the effect of earth reinforcement, it may be considered that the reinforcing effect is deeply related with the localization of deformation a … More nd progressive failure.The purpose of this research is to investigate the behavior of real progressive failure of the reinforced foundation ground and to establish a valid quantitative design calculation which could be based on the real failure mechanism. First of all, a series of model loading tests using the simulation of foundation ground by aluminum rods are conducted, in which the length and the property of the reinforcing material are varied. Based on the results of the loading tests, not only the bearing capacity but also the mechanism of progressive failure is investigated by using image processing analysis. Thus the progressive failure of the reinforced foundation ground are discussed in detail based on the microscopic observation and the analyzed results. These experimental results are concurrently analyzed by using "rigid-plastic finite element method". In the analysis, the model of reinforced soil is newly developed and also geometrical nonlinearity is taken into consideration in order to obtain the progressive behavior of the ground. The validity of the proposed method are verified by comparing with the results of the model tests. In addition, a simplified upper-bound mechanism appropriate to the observed mechanism is proposed, and applied to the test cases.The results achieved through this research are fundamental on the localization of deformation and progressive failure of the reinforced foundation ground. These results could be proved to be indispensable information for the future design method. Furthermore, the proposed analytical method for the reinforced foundation ground could have a great promise for the bearing capacity of reinforced earth structures. Less