Stability analysis of dual structure bank slope under the condition of water level fluctuation:Take the bank of Zhinancun bank collapsed in Yangzhong City as an example

Based on the theory of saturated-unsaturated seepage, shear strength theory of unsaturated soil and limit equilibrium method, the stability of the bank slope with dual structure in the process of river water level fluctuation was studied in this paper. The slope soil is a binary structure, the upper layer is silty clay, and the lower layer is silty sand. The silty sand layer is thicker and more permeable, which provides a good environment for groundwater flow. Saturated-unsaturated seepage caused by water level fluctuation has an obvious effect on the stability of bank slope. The stability of bank slope increases with the rise of water level in the flood period, and decreases with the decline of water level in the flood period. The safety coefficient in the water retreat period is obviously lower than that in the flood period and the flood period under the same conditions, that is, the stability of the bank slope is reduced due to the water level fall, and the bank slope collapse is easy to occur. The faster the water level rises, the greater the maximum safety factor of the bank slope is, that is, the more stable the bank slope is when the water level rises rapidly. The faster the water level drops, the smaller the minimum safety factor of the bank slope is, that is, the bank slope is more prone to instability and collapse when the water level drops abruptly.