عنوان مقاله [English]
Because it is not possible to recognize the mechanism of cantilever failure in field studies, this type of common failure in riverbanks is investigated in the laboratory. For this purpose, two samples of susceptible soil that forms an overhanging block in riverbanks are used for physical model tests to determine their physical, chemical and mechanical characteristics. Soil blocks of different densities were formed and then undermined by hand at specific depths over specific time increments and the stability of the overhanging block were assessed at each step. The results showed that, under these laboratory study conditions, the dominant failure mechanism is toppling. This finding is in accordance with the overhanging failure pattern in the Kordan Riverbanks. It was also found that the failure mechanism in cohesive soil is progressive and accompanied by tension crack development. In Loess material, the failure mechanism is momentary and no deformations in the upper part of the soil block are observed.
Dapporto, S., Rinaldi, M., Casagli, N. and Vannocci, P. 2003. Mechanisms of riverbank failure along the Arno River, central Italy. Earth Surface Processes and Landforms. 28(12): 1303-1323.
Darby, S. E., Gessler, D. and Thorne, C. R. 2000. Computer program for stability analysis of steep, cohesive riverbanks. Earth Surface Processes and Landforms. 25(2): 175-190.
Rinaldi, M. and Darby, S. E. 2008. Advances in modelling river bank erosion process. In: Habersack, H., Piégay, H., Rinaldi, M. (Eds). Gravel-Bed Rivers 6: From Process Understanding to River Restoration. Series Development in Earth Surface Processes. Elsevier. The Netherland. 213-239.
Samadi, A. 2007. Personal Communication with Prof. Colin Thorne. Dept. of Irrigation and Reclamation Engineering. Uni. Tehran. IRAN.
Samadi, A., Amiri-Tokaldany, E. and Darby, S. E. 2009. Identifying the effects of parameter uncertainty on the reliability of riverbank stability modeling. Geomorphol. 106, 219-230.
Samadi, A. 2011. Experimental, and Analytical Investigation of the Stability of Riverbanks against Cantilever Failure. PhD Thesis. Dept. Irrigation and Reclamation Engineering. Uni. Tehran. IRAN. (in Farsi)
Simon, A., Curini, A., Darby, S. E. and Langendoen, E. J. 1999. Streambank mechanics and the role of bank and near-bank processes in incised channels. In: Darby, S. E., Simon, A. (Eds). Incised River Channels: Processes, Forms, Engineering and Management. John Wiley and Sons. Ltd. Chichester. U.K. 123-152.
Thorne, C. R. and Tovey, N. K. 1981. Stability of composite river banks. Earth Surface Processes and Landforms. 6, 469-484.