Monitoring And Simulation Analysis Of The Saturation Line Of The Miyun Reservoir Earth-rockfill Dam With Inclined Core Wall

China is the world's largest dam industry and some of these dams have problems of various degrees.Once a dam appears dangerous,it will endanger people's lives in the downstream.It has a major impact on people's productive lives.With the increasing attention to dam safety,the dam safety monitoring problem has become the focus of people's analysis and research.The normality of the dam saturation line is the key factor affecting dam safety.Therefore,dam safety monitoring data are used statistically to analyze the dam saturation line and the finite element software is used to simulate the dam saturation line.The research on the dam saturation line from various aspects has become the main direction of this research.In this paper,Miyun Reservoir earth-rockfill dam with inclined core wall is taken as an example.A series of research work has been carried out on the earth-rockfill dam saturation line through the dam monitoring data and related permeability coefficients of the earth-rockfill dam materials uses regression analysis and numerical simulation methods.The research contents are:(1)Qualitative analysis of earth-rockfill dam monitoring dataFrom the perspective of the correlation between the piezometric water level and reservoir water level,the data of the piezometric water level and reservoir water level for the past 54 years from 1961 to 2015 were collated and qualitative analysis of the dam saturation line was conducted using comparative and mapping methods.It shows that the piezometric water level in the dam is significantly lower than the reservoir water level.The degree of correlation with the reservoir water level is poor and the saturation line of the dam is basically normal.(2)Analysis of saturation line based on regression analysisStatistical analysis of monitoring data over the years was conducted to consider independent variables such as reservoir water level,downstream water level,precipitation and time effects.Based on the principle of least squares,a statistical model including one-dimensional linear regression,multiple linear regression and stepwise linear regression was established to analyze the importance of influence each variable pair on piezometric water level and a more concise statistical model of stepwise regression is determined.The results show that the main influencing factors of the piezometric water level are the upstream and downstream water levels,especially the downstream water level while the precipitation and time effects have little effect on the piezometric water level and the time effect has the least influence on the piezometric water level.(3)Analysis of saturation line based on finite element numerical simulationBased on the monitoring data of the actual saturation line of the earth-rockfill dam,GeoStudio a two-dimensional finite element seepage software was used to perform seepage calculation to determine the permeability coefficient of the earth-rockfill dam material and this permeability coefficient was used to determine the location of the saturation line within the earth-rockfill dam under different water levels.The results show that under different working conditions,the location of the infiltration line downstream of the earth-rockfill dam is relatively low and the change of the water level with the reservoir is small.The anti-seepage effect of the inclined core wall is good and the seepage of Miyun Reservoir earth-rockfill dam with inclined core wall is normal.In this paper,Through the statistical analysis of monitoring data and the simulation and analysis of two dimensional finite element seepage software,the main factors affecting the water level of the pressure measuring pipe in the monitoring section of the infiltration line of the earth rock dam are determined,and the stepwise regression statistical model is determined.It shows that the water level of the pressure pipe is less influenced by the upstream water level,and the effect of the anti seepage system of the inclined wall is good,the location of the infiltration line in the lower reaches of the earth and rock dam is low,and the change range is small,and the seepage of the earth rock dam is normal.