Forecasting of Rainfall-Induced Slope Disasters by Ground-Based Tilt Sensors

This chapter addresses the tilt sensor for slope monitoring, with which the behaviour of unstable slopes is monitored at low cost (less expensive than conventional tools such as extensometers and borehole inclinometers) and early warning is issued. The traditional kind of inclinometers used to be placed on the slope surface, and their operation was not easy. In contrast, the new tilt sensor that monitors the angular change as well is attached to the top of an embedded rod that rotates together with the slope movement. This rotation is monitored by the tilt sensor, and the record is transferred to the head quarter. The threshold for issuing a warning is based on the rate of tilting that appropriately expresses the ongoing extent of slope instability. An example of the tilt-sensor record is presented together with the records obtained by extensometers and borehole inclinometers in order to verify that the tilt sensor is an equivalent but less expensive choice to the conventional devices.