Field monitoring is essential for assessing the stability of natural as well as well-designed slopes to confirm the validity of the design. Many instruments and systems are available for monitoring the slope behavior. Interpretation of the monitoring results for assessing the stability of slopes is an important task. Displacements are usually plotted versus time, and their transition and rate of increase are observed and compared with the criteria. This is a common and useful practice, but it is based on an empirical method. Therefore, a method for assessing the stability of slopes on the basis of rock mechanics is required. This paper outlines a back analysis method originally proposed by Sakurai in 1987 to estimate the factor of safety from the measured displacements. Two case studies are demonstrated to confirm the validity of the method. By applying the back analysis method to natural and well-designed slopes, the time transition of the factor of safety can be estimated from the measured displacements. The applicability and limitations of the method are also discussed.
In recent years, slopes in various areas of Japan have collapsed because of heavy rain and large-scale earthquakes. Therefore, it is important to properly assess the stability of slopes to reduce the risk of public disasters. In general, the stability of slopes is assessed by calculating the force balance using the mechanical constants obtained from geological surveys and laboratory and in situ tests. Field monitoring is essential for assessing the stability and confirming the validity of the design.
Many instruments and systems are available for monitoring the slope behavior. Extensometers and inclinometers are often used. GPS/GNSS is now a well-known method for monitoring three-dimensional displacements [1]. DInSAR has the potential to observe displacement distribution over extensive areas [2].
Interpretation of the monitoring results for assessing the stability of slopes is an important task. Displacements are usually plotted versus time, and their transition and rate of increase are observed. The results are compared with the threshold or the critical value for assessing the stability.