Monitoring rock deformations is important to assessing the stability of rock structures, i.e., slopes, tunnels, dams, foundations, etc., to confirm the validity of the design under/after construction and to assist in answering specific questions on a project, etc. In order to perform monitoring successfully, various instruments and systems have been developed. The Global Positioning System (GPS) and Synthetic Aperture Radar (SAR) have the potential for application to displacement monitoring over an extensive area as attractive new monitoring tools in Rock Engineering.
In this paper, outlines of the methods for displacement monitoring using GPS and SAR (InSAR) are described. Practical and trial applications of both technologies to an unstable steep slope, a large landslide occurring due to heavy rains, dam behavior caused by the attack of a large earthquake, and dam deformation monitoring are introduced
Monitoring is important for assessing the stability of structures and for confirming the validity of the design during the construction and operation stages. Monitoring is also useful for predicting risks, for managing safe operations, and for reducing project costs. The ideal monitoring system for projects in Rock Engineering should be able to continuously and automatically monitor the behavior of an extensive area in real time and with high accuracy. In addition, the costs should be low and the handling should be easy.
There are various types of instruments for monitoring displacements in Rock and Geotechnical Engineering, such as extensometers, inclinometers, laser distance meters, etc. Although they are useful for monitoring, they can be applied only in local areas. Conventional surveying methods, like electronic distance meters, leveling, etc., are often used in monitoring the behavior of an extensive area. However, they generally require a lot of time, labor, and financial resources. In addition, the measurement accuracy is not sufficient in comparison to that achieved when using geotechnical instruments.
In order to overcome such problems of the conventional methods, modern satellite technologies for navigation/surveys and earth observation, i.e., GPS (Global Positioning System) and SAR (Synthetic Aperture Radar), have begun to be used in the Rock Engineering field. GPS is a space-based satellite system for navigation and long baseline surveys which provides the three-dimensional coordinates of certain locations on or near the Earth. SAR is a kind of radar which is used to create images of a landscape; these images can be two- or three-dimensional representations of the object. Both technologies can be applied to monitor the displacement/deformation of the ground and the surfaces of structures.
This paper provides outlines of the monitoring methods using GPS and SAR, and introduces examples of their applications to monitoring the displacements of slopes, landsides, and dams.