Research On Analyzing FoSi Dam Seepage And Slope Stability

Water conservancy in China has been developing for a long time and a large number of water conservancy projects have been built. Earth-rock dam of which the performance is easy to maintain has been wildly used for its simple structure and construction technology, low costs and high adaptability. Seepage analysis and slope stability analysis are the key factors in both designing earth-rock dam and safety assessment analysis, through which the potential and existing threat could be identified and prevented by taking measures to ensure the dam’s safe operation. In this paper, GeoStudio was applied in Fosi reservoir which is an earth-rock dam to analyze its seepage stability, aiming to evaluate this dam’s safety.Firstly, the research status and methods of seepage and slope stability analysis were introduced based on previous studies. Then, the theoretical basis of seepage analysis and its related finite element method’s rationale and computational process were explained as well as the research technique of slope stability analysis:limit equilibrium method and finite element method. Finally, combining BP neural network method and finite element method, the back analysis of this dam’s seepage coefficient was demonstrated on the basis of Fosi reservoir’s data. GeoStudio was then used to examine the dam’s seepage and slope stability in order to assess its safety.The seepage back analysis result shows that the clay core, the upstream loam and the downstream loam in0+510.1cross section are5.90E-06cm/s,1.00E-05cm/s and2.00E-04cm/s respectively. The seepage back analysis indicates that the clay core and upstream loam in0+510.1cross section play significant roles in seepage drain while sand gravel layer in dam foundation is helpful for seepage draining. However, there are still parts of Head contour distributing in the weathered rock of dam foundation. Under condition of high water level, the higher horizontal percolation gradient will possibly lead to the seepage failure in clay core. The seepage flow per unit width in this cross section varies from0.257m3/d to0.855m3/d under different conditions, reducing with the decrease of water level. The slope stability analysis proves that0+510.1cross section’s slope stability basically meets specifications.But when the design flood level fast falls to the spillway weir crest elevation, the anti-slide safety factor cannot meets specifications, resulting in slope instability. The calculation and analysis testifies that the cross section’s seepage stability meets specifications. Curtain grouting in the no-grouting area of dam foundation is suggested to improve seepage condition; anti-seepage reinforcement on high percolation gradient area is suggested to maintain the seepage stability of dam foundation; seepage drain reinforcement measures is suggested to be taken to prevent slope instability due to the sudden drawdown of water level.