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

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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.