Large-Scale Lab Model Test Study On The Mechanism Of Bank Collapse In Middle-Downstream Of Yangtze River

The bank collapse is a quite prevalent and prominent geologic hazard along the middle-downstream Yangtze River, which highly menaces the safety of the dikes and cities along the river. However, the study on the mechanisms of bank collapse are still immaturity and have limitation, which are almost based on certain examples by analyzing and empirically summarizing and are parlous lack of lab and field test studies. Therefore, the study on the mechanism of bank collapse, especially the study on the lab and field test, should be reinforced to obtain the causes and the laws of development of bank collapse, which have imponderable value for the flood control and disaster mitigation.Based on the collecting and analyzing the former research results, different classifications of bank collapse are summarized, the internal relation between them is analyzed and characteristics of bank collapse and characteristics of influencing factors along the middle-downstream Yangtze River are induced. Then, via the large-scale lab model test, the study on common phenomena of bank collapse and its main influencing factors is conducted on the base of field survey and analysis on bank collapses along the river, the internal mechanism on predisposing causes and developing process is obtained and the preventive measures and processing means are advanced. Main conclusions are listed as follow:1. The potential liquefying sand of the bank under the scouring effect of current and the shearing action of seepage is impossible to occur the phenomenon of retrogression liquefaction during the collapse progress.2. The parameter of the pore water pressure and soil pressure are unfitted as the monitoring and forecasting index for bank collapse. The parameter of displacement can use as the monitoring and forecasting index, but the inbuilt position of displacement gauges should be carefully set at the potential slide mass.3. The longitudinal distribution of the characteristics of the influencing factor affects the plane shape of bank collapse, and the transverse distribution of the characteristics affects the stress condition and the failure format of avalanche body.4. Bank collapse is outcome of the dynamic variety of the bank stability. The process of bank collapse is a dynamic and progressive cyclic process under the action of manifold influencing factors, and the specific form of bank collapse is the outcome of combined action of endogenesis and exogenesis. In the middle of influencing factors, geology factor is endogenesis, which is the most important factor, and the other factors, such as river dynamics factor, hydrometeorology factor, human activities and nature activities, etc, are the evoked condition of bank collapse.