波动水位下河道堤防壤土斜墙截渗分析

Seepage Interception Analysis of Loam Slope Walls in Riverbank Levees Under Fluctuating Water Levels

考虑水位波动和防渗墙的尺寸结构对堤防渗流特性的影响,共设计了28种工况,对比分析波动水位下防渗墙的厚度、防渗墙的嵌入深度和堤基的渗透性对堤防的渗流量、膜后浸润线高度、防渗墙底部及溢出点水力坡降的影响。结果表明,相比防渗墙的厚度变化,增加防渗墙的嵌入深度更能有效控制堤防渗流量、降低膜后浸润线高度和溢出点水力坡降;当嵌入深度为0~2 m时,水力坡降随嵌入深度的增加而减少,且呈现先快后慢的变化趋势,当嵌入深度超过2 m以后,水力坡降随嵌入深度的增加而增加,且在5 m时达到峰值,超过5 m时水力坡降骤降;此外,对于悬挂式防渗墙设计,当坝基渗流量控制在75%时,溢出点水力坡降均小于0.25,防渗墙嵌入深度与坝基渗透系数之间存在强对数线性关系,所建拟合公式可用于类似代建工程防渗墙嵌入深度的初步设计或已建工程的渗流控制评估。

Considering the influence of water level fluctuations and the dimensional structure of impermeable walls on the seepage characteristics of embankments,28 scenarios were designed to compare and analyze the effects of the thickness of impermeable walls,the embedding depth of impermeable walls,and the permeability of the embankment based on the seepage flow,the height of the seepage line behind the membrane,and the hydraulic slope at the bottom and overflow point of impermeable walls under fluctuating water levels.The results indicate that,compared to changes in the thickness of impermea-ble walls,increasing the embedding depth of impermeable walls can more effectively control seepage flow of embankments,reduce the height of the seepage line behind the membrane,and decrease the hydraulic slope at overflow points.For embedding depths ranging from 0 m to 2 m,the hydraulic slope decreases initially with increasing depth,showing a trend of rapid decline followed by a slower decrease.Beyond 2 m,the hydraulic slope increases with depth,reaching its peak at 5 m before sharply declining when exceeding 5 m.Additionally,in suspended-type impermeable wall designs,when controlling the dam base seepage at 75%,the hydraulic slope at the overflow point remains below 0.25.A robust logarithmic-linear relationship exists between the embedding depth of the impermeable wall and the dam base permeability coefficient.The derived fitting equation can be applied for the preliminary design of impermeable wall embedding depth in similar construction projects or for evaluating seepage control in existing projects.