Development of Slope Deformation Monitoring System Based on Tilt Sensors with Low Power Wide Area Network Technology and Its Application

A simple monitoring method for observing slope movement and deformation can be performed with tilt sensors. A more efficient monitoring method, using a type of wireless communication called LPWA (Low Power Wide Area) network technology, has also recently become available. In the present study, a monitoring system was developed that combines tilt sensors and LPWA network technology for measuring the movement of slopes and sending the information through wireless communication. Firstly, radio wave propagation experiments were conducted to find the proper location for the gateway device of the monitoring system. Then, in March 2018, the developed system that consists of tilt and water-level sensors and the wireless communication of LPWA was installed at an observation site. Since the installation, the data from the tilt sensors have been successfully collected through LPWA, and a slope failure was unexpectedly observed at the observation site during the Heavy Rain Event of July 2018, which caused severe disasters, particularly from western Japan to the Tokai region. Using the data from the tilt sensors, the rainfall data, and the groundwater level, the slope failure was analysed. A site investigation was conducted, and the shear strength parameter was examined using back analysis method. In conclusion, the developed system using sensors and LPWA has continued to efficiently monitor the movement of the targeted slope, but the collection of additional data will be required to increase the reliability of the system.