Development of a ground displacement measurement method for failed slopes at the toes of landslides

Sediments produced by a slope failure of the toe of a landslide are assumed to prevent the spread of the failure. Thus, sediment removal is an emergency measure that must be done safely while the slope is observed. Observation must also be done safely without requiring workers to enter the failed slope to avoid secondary disasters.Generally, a non-prism type totalstation is useful to measure ground displacement under such circumstances, because this type of totalstation can be used without placing targets on the slope. However, the lack of prisms results in problems related to the objectivity of measurement data, collimation error of the totalstation, measurement at night, and so on.The authors have developed targets and a remote target placing method in order to resolve the above problems. As a result, we have established remote measurement technique for ground displacement on failed slopes at the toes of landslides. This paper describes the .measurement technique that has been developed