Low-cost and simple early warning systems of slope instability

Abstract

In the projects of IPL 139 (Development of low-cost early warning system of slope instability for civilian use) and IPL 127 (Development of low-cost detector of slope instability for individual use), a low-cost and simple monitoring method for early warning of landslides was proposed. A wireless sensor unit which is equipped with a MEMS (Micro Electro Mechanical Systems) tilt sensor and a volumetric water content sensor was developed and tested on eight real slopes in Japan and China. The sensor unit measures rotation angle on a slope surface by the tilt sensor. In order to examine its relevance, model tests were conducted, and it was confirmed that rotation of the slope surface was observed 30-50 minutes before failure. A similar trend was also observed in a real slope. This could be useful as a signal for early warning. The authors also developed a new sensor device named the 'Miniature Ground Inclinometer'. It is a long stainless steel pipe with a small diameter, which is equipped with MEMS tilt sensors. By installing it vertically into the slope ground, the array of tilt sensors detects the lateral displacement of the ground. It can be directly inserted into the slope ground together with the sensor units inside by using a small hammer. This allows low cost and quick installation of the device in landslide sites.