Continuous displacement monitoring is very important to study the displacement behavior of a slope in order to assess its stability, to predict its future failure, and to design countermeasure works. The Global Positioning System (GPS) is being used widely for monitoring rock displacements. The most important technical issue for the practical use of GPS is to perform real-time and precise monitoring even under adverse observation conditions, i.e., steep slope with narrow sky view over the antennas and large height difference between measurement points and reference point. The authors and their colleagues have developed a precise real-time displacement monitoring system using GPS and have established a method of data processing to reduce the errors caused by meteorological factors and obstructions above the antennas. The system has been applied to continuously monitor the slope behavior of an unstable steep slope along a traffic road in Yamaguchi Prefecture, Japan since 2012. At the slope site, large displacements sometimes occurred due to heavy rain, and then local collapses were recorded in some areas of the slope. The groundwater level of the slope has also recorded at a few wells.
In this paper, the GPS displacement monitoring system is applied to monitor the displacements of the unstable steep slope for assessing its stability. Three-dimensional displacement monitoring results and displacement vectors are shown.
