Delineation of Endangered Areas in a Slowly Moving Landslide by the Pressure Probe Method

Abstract

Mechanically weak zones which may not visible from the surface and which may occur e.g. due to landslides can be detected and characterized by the newly developed Pressure Probe (Pre-P) method. On a high bank at Dunaszekcso, Hungary, the fracture system of the loess landslide area was investigated by large resolution applying this method and proved that: (1) cracks as small as 2-3 cm wide are detectable; (2) The fractures follow each other almost periodically; (3) On the side of the fractures towards the slump there are less fractured zones whose width correlates with the width of the given fracture. We also demonstrated that on the passive side of the clearly visible fracture: (1) There are also fractures along which future rock displacement is expected; (2) These fractures are at least as wide as the active side fractures; (3) The blocks there are about twice as wide as those on the active side. A block several meters wide is expected to fall before the main mass movement. The Pre-P method seems to be the most powerful tool to map the fracture system of such landslides because of its speed, simplicity of application, cost and interpretation. The Pre-P profiles and maps of the fracture system of a landslide enable to understand landslide evolution and delineate endangered areas earlier than by other methods.