水位变动条件下二元结构岸坡稳定性分析——以扬中市指南村崩岸段岸坡为例

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

以指南村崩岸段岸坡为研究对象,通过实地调查开展地质钻探工作,获取岸坡土体的物理力学参数,并基于饱和非饱和土渗流理论、非饱和土抗剪强度理论及极限平衡法,研究江水水位变动过程中二元结构岸坡稳定性的变化。结果表明:①岸坡土体为二元结构,上层为粉质黏土,下层为粉砂,粉砂层厚度较大且透水性较好,为地下水流动提供良好环境。②水位变动引起的饱和非饱和土渗流对于岸坡稳定性有明显影响,岸坡稳定性在涨水期随水位上升而增大,在退水期随水位下降而减小。退水期安全系数明显低于相同条件下涨水期和洪水期,即水位降落导致岸坡稳定性降低,极易发生岸坡崩塌。③水位上升速度越快,岸坡安全系数最大值越大,即岸坡在水位骤涨时更加稳定;水位下降速度越快,岸坡安全系数的最小值越小,即岸坡在水位骤降时更容易发生失稳崩塌。

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.