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Study on field detection and monitoring of slope instability by measuring tilting
motion on the slope surface
Détection et surveillance in situ des phénomènes d'instabilités de pente par mesure locale des
mouvements de surface
Wang L., Nishie S., Seko I.
Chuo Kaihatsu Corporation, Tokyo, Japan
Uchimura T.
University of Tokyo, Japan
ABSTRACT: Monitoring and early warning is one of the most effective methods toward reduction of disasters induced by landslides
and slope instabilities, but the traditional methods such as multiple borehole inclinometers or extensometer are expensive and
unsuitable to zoning monitoring. To overcome the above weaknesses, a simple and low-cost early warning system was developed for
slope failure and landslide (Uchimura et al. 2009). The developed tilt sensor is easy to install and it can monitor slope deformation by
means of a tilting MEMS module angle which embedded in the sensor, and transfers real time data via wireless network. The warning
system with its developed equipments has been deployed in several actual slopes for validation of field performance in Japan and
China. In this paper, the authors will show that the developed system and sensor can successfully detect the situation of slope and
landslide, and issue useful information that allows residents to avoid slope failure or landslide disasters. Based on the results of field
case studies, the developed low-cost sensor unit and real-time warning system are considered particularly effective against rainfall-
induced slope failure or landslides and its general use is recommended.
RÉSUMÉ : Une surveillance constante associée à un dispositif rapide d’avertissement est une solution efficace pour lutter contre les
désastres et les pertes humaines liés aux glissements de terrain ou aux ruptures de pentes. Cependant, les équipements traditionnels
tels que les inclinomètres ou extensomètres installés par forage sont généralement d’un coût prohibitif et sont peu adaptés à une
surveillance plus généralisée du territoire. Un nouveau système plus flexible et de coût plus réduit a été proposé par Uchimura et al.
(2009). Il incorpore des micro-inclinomètres de type MEMS faciles d’installation qui permettent d’estimer les mouvements de
surface. Les données peuvent être transmises en temps réel via réseau sans fil. Ce système a été déployé sur plusieurs sites en Chine et
au Japon. A partir des données recoltées sur ces sites, il est démontré que ce système est efficace et fiable dans l’estimation et la
détection précoce des glissements de terrain, et qu’il permet d’obtenir des renseignements cruciaux pour prévenir leur poursuite ou
pour réduire les dégâts occassionés.
KEYWORDS: landslide, slope failure, monitoring, early warning.
1 INTRODUCTION.
Typical measures to prevent slope failure are retaining walls
and ground anchors which improve safety factor against failure.
These measures have been widely used everywhere in the world
and its effectiveness has been confirmed. However, the
traditional methods take a lot of cost, as a result that a limited
application can be used only for large scale slopes. In fact, most
of landslide occurs at small scale slopes, but with a large
number. It is not realistic to apply mechanical reinforcement
measures for these slopes with potential risk.
Rainfall-induced slope failures are one kind of the most
destructive natural hazards. Many slope failures have been
observed to occur during or immediately after rainfall. For a
wide range slope safety monitoring, a problem in the first was
that the equipments were high-cost; this is a problem that
disaster prevention measures was difficult for implementation
into developing countries. The cost issues should be overcome
for a purpose of widespread use; another is that a simple and
effective real-time monitoring becomes necessary.
The authors have proposed an early warning system for
sediment disasters, as one of more feasible countermeasures for
small-scale slope failures. The system measures minimum
number of items by using the developed smart sensor units; the
measured data is transferred through wireless network. Thus,
the system is low-cost and simple enough so that the residents
in risk areas can handle it to protect themselves from slope
disasters (Uchimura et al. 2009).
2 A LOW-COST AND SIMPLE WARNING SYSTEM.
A simple and low-cost early warning sensor unit was developed
that only two parameters of the volumetric water content of soil
and the inclination of slope or landslide were focused, and its
applicability and effectiveness were tested on model slopes
under artificial heavy rainfall (Uchimura et al. 2009). The senor
unit works with batteries, and transfers real time data via
wireless network, and installation is simple and easily to control
so that non-expert residents in risk area can handle it by
themselves, even in developing countries. Figure 1 shows the
basic concept of the wireless monitoring unit using for early
warning system.
Figure 1. Wireless tilt sensor unit with water content sensor.
2.1 RF (Radio Frequency) wireless data transmit method
Figure 2 shows the outline of wireless monitoring and early
warning system for slope failure. The system is designed to be
wireless, that is, each unit works autonomously with
