Observed data analysis of earth pressure during earthquake of retaining wall of a base-isolated building

The authors developed network seismic observation system that can measure from small ambient vibration to large-scale earthquake into a base-isolated building. Earth pressure cells are also installed onto retaining wall of base isolation foundation, therefore dynamic behavior of retaining wall of base isolation foundation can be observed as well as a superstructure. The observation started from 2014 and several earthquakes have been observed by this system. In this paper, dynamic behaviors of a superstructure, retaining wall of a base isolated building, and surface ground are discussed based on the observed earthquake records, especially dynamic earth pressure of retaining wall of base-isolated building is focused. Superstructure of the base-isolated building is a five-storied RC frame structure, and network type seismometers are installed at base isolation basement, ground floor, and top floor. Earth pressure cells are placed at GL-2m of retaining wall of which height is about 3m in ground. After the start of observation, nine small or intermediate earthquakes have been observed. Dynamic behaviors of earth pressure cells are also discussed based on the observed data. Four cells are installed onto retaining wall of base isolated foundation at GL-2m. Two of them are NS direction, and the other two are EW direction. The superstructure has L-shaped plan and the locations of earth pressure cells are on the same side, namely all of them are installed on the courtyard side because of the condition around the building. As well as observed data of seismometers, observed data of dynamic earth pressure during earthquake are compared.