REPORT CONCERNING THE POSSIBILITIES OF LANDSLIDES ON THE BULGARIAN DANUBE RIVERBANK AS A CONSEQUENCE OF FAST DANUBE PROJECT

 

The goal of this report is to analyse the possibility of triggering or activation of existent landslides on the right bank (Bulgarian) of Danube, at the critical points, as a consequence of dredging activities and other works/ interventions (scenario 1 and scenario 2) proposed in the FAST DANUBE project -Improvement of the Navigation Conditions on the Romanian-Bulgarian Common Sector of the Danube.

 

This report is based exclusively on the field visits performed during March 2021, on the data provided by the Client (landslides monitoring reports), on the geotechnical investigations performed by AFDJ on the Danube riverbed in June 2020, on the scientific papers written by the Bulgarian researchers that studied previously the already existant or future issues concerning landslides, on the right Danube river bank and expert judgement/interpretation of the available data.

 

The most important factor that determines the landslides activation is rainwater or snow, water from snowmelt and groundwaters. In the area of landslides, the layer of moving material cover, the water springs and block the free flow of the water, moisture in excess the land and determining the decreasing of the shear strength values. Inside the landslide body, the shear strength and friction between the particles are influenced by the presence of absorbed water; a high percentage of the clay fraction and the high humidity determines small values of the internal friction angle, even near zero value.

 

The study concludes that dredging the fairway of Danube, up to 3.5 m depth, at a proximity of 190 m from the bank (in the worst case scenario) and other engineering proposed works as established by the FAST Danube project, will not affect the stability of the slopes on the right bank of Danube (Bulgarian bank) and it is not considered necessary to perform more detailed geotechnical studies or more monitorization during the implementation of the project.