土石围堰渗流场分析及稳定性评价

Fluid flow analysis and stability evaluation of earth-filled cofferdam

为了分析上游土石围堰防渗设施的布置方案及其阻渗效果,对设有防渗墙的土石围堰进行渗流计算,确定设计洪水期的堰体渗流场,并对防渗墙入岩深度、基岩、防渗墙渗透系数等进行敏感性分析:材料渗透系数的变化对渗透坡降的影响较大,其中防渗墙渗透系数改变后的影响最为显著。同时,运用瑞典法、Bishop、Janbu法计算各工况的围堰堰坡安全系数,其计算成果显示:各工况的堰坡稳定性符合一般规律;设计洪水期以及同时考虑与地震组合作用时,堰坡的稳定系数降低明显;如不考虑防渗措施,其围堰的稳定性系数还将降低更多,说明该工程的防渗设施是有效的。防渗墙的质量优劣对堰体渗流控制和安全稳定性起着重要的作用,在施工阶段一定要严格施工质量,保证工程的安全运行。

To analyze the cut-off scheme and the effect of earth-filled cofferdam,fluid flow analysis was applied for the earth-filled cofferdam with the cut-off wall considering the design water level.And then,sensitivity analysis was used considering depth of cut-off wall infixed in the rock,foundation rock,hydraulic conductivity of cut-off wall,the above three results which considered parameter changing showed that the variation of hydraulic conductivity,especially the hydraulic conductivity of cut-off wall influenced the hydraulic gradient greatly.And simultaneously,Swedish circular method,Bishop method、Janbu method were used to calculate the safety factor of earth-filled cofferdam slope.The results show that all the safety factors corresponded with the general law.However,safety factor considering design water level and earthquake was less than the operation mode with no water in due to the high upriver water level and seism effect.According to the above results,the safety factor fell more with no cut-off scheme.Therefore,quality of the cut-off wall in the period of construction is important for seepage controlling and safety of the earth-filled cofferdam,which will influence the operation of the project.