Geological structure of the dam base as a factor of its reliability during flood periods (Hanoi)

Abstract

The object of study is a system of protective dams in Hanoi. In the new social and political conditions of Vietnam’s transition economy, the transformation of the riverside territories is of great importance for both the city of Hanoi and the country as a whole. A special role is given to the system of dams along the Hanga River (Red), which protect the city from floods. During the long history of construction and operation of the dams in Hanoi, many cases of their damage and destruction are known. The aim of the study is to assess the sustainability of the dams, the possible mechanisms of dam stability loss due to changes in hydrological conditions are examined. By mathematical modeling, the stability of the dam slopes and filtration strength of its base soils are calculated due to an increase in time during flooding hydraulic gradient. This task was solved in the flat setting, meanwhile, filtration modeling was carried out by the finite element method, and the estimation of the dam slopes stability was carried out based on the limit equilibrium method. The mathematical modeling allowed to estimate the dam stability from two positions: 1) change of the dam slope factor safety in time during the flood period; 2) increase of the hydraulic gradient in soils of the dam base during the flood period. The results obtained showed that the reliability of the dam depends both on the thickness of the clay layer at its base and on the duration of flooding. The factors we have identified that affect the stability of dams during flood periods can be used for predicted purposes to assess their reliability.