Abstract:

The Yanbaru Pumped Storage Power Station is the unique hydro-electric power station utilizing seawater, located in Okinawa Island, Japan. The construction of underground house was completed in 1999 and it is located at a depth of about 132 m below the ground surface. This underground powerhouse provides a unique chance to monitor its dynamic and multi-parameter responses during earthquakes and long-term period. The authors installed three accelerometers in the underground powerhouse and one accelerometer at the ground surface to observe its acceleration response during earthquakes. In addition, some displacement gap sensors, AE sensors at the adjacent connection tunnel, rock temperature and environmental parameters such as temperature, humidity and CO2 sensors in the powerhouse and ground surface were installed to monitor its multi-parameter responses. In this study, the authors describe this instrumentation, some numerical analyses and the results obtained so far.

1 Introduction

The Yanbaru Seawater Pumped Storage Power Station is the first experimental hydro-electric power station utilizing seawater, located in Okinawa Island, Japan (Fig. 1). The construction was completed in 1999. The underground powerhouse is located at a depth of about 132 m below the ground surface (Fig. 2).

This underground powerhouse provides a unique chance to monitor its dynamic and multi-parameter responses during earthquakes and long-term period. The authors initiated a collaborative research since July 2017. Four accelerometers were installed in the underground powerhouse to observed its acceleration response during earthquakes. Specifically, one accelerometer at the bottom level, two accelerometers at the mid-level and one accelerometer at the ground surface at an elevation of 132 m were installed. Furthermore, micro-tremor measurements were carried out in the powerhouse, access tunnel and the ground surface.

Some displacement gap sensors, AE sensors at the adjacent connection tunnel and environmental parameters such as temperature, humidity and CO2 sensors in the powerhouse and ground surface were installed to monitor its multi-parameter responses. Recently, some temperature sensors installed to observe the temperature of rock mass in relation to the temperature variation in the powerhouse.

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