Abstract
Exterior deformation is one of the most important items to measure when managing the safety of embankment dams. A conventional surveying method, using targets installed on the crest and the slopes of the embankment dams, is usually employed to measure exterior deformation. It is difficult, however, to measure the deformation by such a method immediately after an earthquake or other emergency. A displacement monitoring system using GPS (Global Positioning System) was developed to continuously monitor the deformation of dams. The system can provide three-dimensional displacements at many points simultaneously with high accuracy at the millimeter level. Ishibuchi Dam is a concrete-face rock-fill dam; it is one of the oldest rock-fill dams in Japan. After the large settlement caused by the Iwate-Miyagi Nairiku Earthquake of 2008, the above GPS displacement monitoring system was installed to continuously monitor the deformation behavior. On March 11, 2011, the Great East Japan Earthquake struck near the northeast coast of Honshu Island. This paper describes the results of the deformation monitoring of Ishibuchi Dam before, during, and after the Great East Japan Earthquake, and discusses the validity of the system for the safe management of dams after earthquakes.
