LANDSLIDE MONITORING FOR PRESUMPTION OF UNDERGROUND SLIDE SURFACE

摘要

An analytic procedure using the three dimensional displacement vector of ground objects tracked in the landsliding field demonstrates the applicability of photogrammetry to the measures of landslide disaster reduction and to the presumption of underground slide surface geometry. To obtain the reliable information of ground movement caused by rapidly growing landslide where no field surveying is acceptable, only the aerial photogrammetry can be used safely and effectively. The three dimensional displacement vector, which is considered to represent the characteristics of mass-movement on the underground slide surface, is detected by the positional data of tracking points recorded in the series of photographs taken at different time flights on the landslide area. Projecting a number of the displacement vectors on a horizontal plane, the direction and velocity of mass-movement, which are important information for planning and accomplishing the measures against the landslide disaster, are analyzed. In this analysis, the influence of errors unavoidably included in each displacement vector is considered to detect acculate behavior of the landslide. On a vertical projection plane taken parallel to the main direction of the mass-movement, the characteristics of the movement, i.e., simple rotational slide, translational slide, complicated slide, etc., are judged to select the analytic method for presumption of the geometry of underground slide surface. For this presumption, the author has devised several analytic methods (Yoshizawa,1987,1989,1992). They are applied to actual landslides occurred in Japan. The utility of the photogrammetry in the field of disaster reduction techniques is vrified by practical analyses shown in this paper.