Investigation of Dynamic and Kinematic Landslide Processes by Borehole Tiltmeters and Extensometers

Landslides cause many damages both in properties and in human life. The high loess banks along the River Danube are the most susceptible areas to mass movements in Hungary. Two test sites, one in Dunaföldvár and the other in Dunaszekcső, were chosen for the investigation of the kinematic and dynamic processes of the high loess banks due to tectonic, hydrologic and environmental effects. On both test sites, more landslides occurred in the last century. In Dunaszekcső the latest landslide took place in 2008. Here a new landslide has been developing since 2010. In Dunaföldvár borehole tilt and borehole extensometric measurements have been carried out since 2002. In Dunaszekcső the borehole measurements began in the autumn of 2007, thus both the large landslide formed in 2008 and the newly developing landslide could be observed. Comparison of tilt data with ground water level changes and the stage of the River Danube resulted in new knowledge of the landslide development processes of the high loess banks. The measurements made evident that the ground water level changes have two-three orders of magnitude larger effect on the high bank stability than the water level variations of the River Danube. The characteristic tilt processes during a 3-4 weeks period before the slump can be used for early warning of landslides. The increasing tilt amplitudes and regression coefficients between tilt and ground water levels could be the precursor of a forthcoming landslide.