强降雨作用下山区岸滩渗流特性演化研究

Study on evolution of seepage characteristics of mountain riverbank under heavy rainfall

为预防由山区岸滩渗透破坏引发的崩岸,根据Boussinesq非稳定渗流微分方程,推导降雨和水位涨落联合作用下山区岸滩浸润线位置的解析解,并与有限元模拟结果对比,证明其正确性;以某山区岸滩为例,基于浸润线解析解揭示强降雨过程及雨停后各阶段岸滩渗流特性演化规律。结果表明:降雨初期,浸润线主要受雨水入渗补给而抬升,渗流方向朝岸滩临河侧;随着降雨持续,浸润线受雨水入渗和河水位上升共同作用而抬升,渗流仍朝临河侧;降雨停止后,临河侧浸润线先因水位持续上涨而逐步抬升至最高位置,再随水位下降而逐渐降低,渗流方向先由朝临河侧逐渐转向朝岸滩内侧再变成朝临河侧;岸滩渗流方向和渗透比降显著变化范围集中在临河侧附近。

In order to prevent seepage failure of mountain riverbank and riverbank collapse,on the basis of Boussinesq unsteady seepage differential equation,an analytical solution was derived for the location of phreatic line in the mountain riverbank under the combined action of rainfall and water level fluctuations. The solution was verified to be correct by comparing the finite element simulation results.A practical mountain riverbank was taken as the research object,the evolution of the seepage characteristics of the riverbank at different stages during and after heavy rainfall were revealed quickly with analytical solution of phreatic line.The results show that at beginning of rainfall,the phreatic line is mainly uplifted by infiltration of rainwater,and direction of seepage is facing the riverside.During the continued rainfall,the phreatic line is lifted by the combined action of rainwater infiltration and the rising water level,and the seepage direction is still towards riverside.After the rainfall,the phreafic line near the river first gradually rises to the highest position because of continuous rises of the water level,and then gradually decreases as the water level decreases,the direction of seepage flow gradually shifts from towards riverside to towards landside,and then again towards riverside.The significant changing range of seepage direction and gradient is concentrated near the riverside.