Many masonry retaining walls which were constructed by using square pyramidal stones over 100 years ago exist on cutting-slopes in Japanese railways. In these walls, there are some arch-deformed walls that resulted from receiving external force like an earth pressure or a seismic shaking. These deformed walls have a relatively high risk of collapse in case of receiving the large external force. But the relationship between the deformation amount and the stability of the wall is unclear. For this reason, this study evaluates the threshold deformation ratio of the maximum horizontal displacement of the wall to its height for discriminating unstable masonry retaining walls by modelling tests. In the model- ling tests, we collapsed two meter-tall masonry retaining walls which are composed of 200 mm × 200 mm × 334 mm- square pyramidal stones by vertical loading applied at the top of slope, and measured earth pressure and horizontal displacement of the wall. As a result of the test, the masonry retaining wall was deformed over 4% deformation ratio by receiving the limit earth pressure against the bearing capacity. This study made it clear that old masonry retaining walls existing in Japanese railways which are deformed over 4% deformation ratio should be judged as unstable. Furthermore we developed simple reinforcement works for the deformed walls and confirmed the deformation prevention effect of those works by the modelling test.
deformation ratio, earth pressure, masonry retaining walls, modeling test, reinforcement work
 Amano, K., Nishida, K., Watanabe, T., Tamano, T. & Hakamura, H., Historical and empirical study on osaka castle masonry wall at tokugawa period. Journal of Japan Society of Civil Engineers, 2000(660), pp. 101–110, 2000. http://dx.doi.org/10.2208/jscej.2000.660_101
 The Japanese geotechnical society, Method for Portable Dynamic Cone Penetration Test, Japanese geotechnical society standards, JGS1433, 2012.