Research on Elucidation of Failure Mechanism in Reinforced Earth Structures and Introduction of the Reliability Design Method

钢格栅加筋土是格栅式加筋土的一种，兼有摩擦和承载两种加筋机理。它比传统的加筋土方法更有用。针对现有的设计方法对钢格栅加筋土的承载力不高的问题，本文尝试采用可靠性设计理论建立有效的设计方法，并通过第一年的室内拉拔试验，对钢格栅加筋土的承载机理进行了研究。在此基础上，提出了基于室内拉拔试验结果的钢格栅加筋土承载力估算公式，并与现场拉拔试验结果进行了比较。估算的抗拔力与室内测试结果一致，但小于现场实测值。另外，为了研究加筋土的破坏机理，我们自制了一套离心模型试验装置，并在第二年进行了一系列的室内拉拔试验和现场实测。为了将可靠性设计方法引入加筋土结构，有必要对其力学性能进行深入研究。特别是在日本这样的地震多发国家，钢格栅加筋土的动力特性研究更是重中之重。因此，我们进行了一系列循环上覆应力下的循环拉拔试验。循环应力条件下的最大抗拔力远小于静态应力条件下的最大抗拔力。通过现场实测，研究了钢格栅加筋土挡墙变形与降雨量的关系。结果表明，加筋土挡墙的变形不仅与降雨总量有关，而且与降雨历时有关。

Steel grid reinforced earth, which has both frictional and bearing reinforcing mechanisms, is one of grid type reinforced earths. It is more useful than conventional reinforced earth methods. Because available design methods aren't effective for the steel grid reinforced earth, we tried to establish the effective design method using the reliability design theory.We investigated the bearing mechanism of steel grid reinforced earth by a laboratory pullout test in the first year. Then, we proposed an equation to estimate bearing resistance of steel grid reinforced earth based on the laboratory pullout test result, and the equation was examined through a comparison with a field pullout test result. The estimated pullout resistance agreed with the laboratory test result, however, it was smaller than that measured in the field. Also, to investigate failure mechanism of reinforced earth, we made a centrifugal model test apparatus.In the second year, we performed a series of laboratory pullout test and field measurement. To introduce a reliability design method to reinforced earth structures, it was necessary to deeply investigate its mechanical behavior. Especially, the dynamic behavior of steel grid reinforced earth was the most important in the countries which have many earthquakes like Japan. Therefore, we performed a series of cyclic pullout test under the cyclic overburden stress. The maximum pullout resistance under the cyclic stress condition was much less than that under the static stress condition. The relationship between deformation of steel grid reinforced earth wall and rainfall was also investigated by a field measurement. It was found that deformation of the reinforced earth wall was related to both total amount and period of the rainfall.