Research On Stability Of Cofferdam Under Seepage And Seismic Coupling Influence

Cofferdam is a temporary retaining structures to ensure that underwater con-struction projects such as hydropower built on the dry land. Its security issue is not onlyrelated to the construction progress and safety of the main project, but also related tothe people’s lives and property safety downstream. Cofferdam’s seepage and seismicissues in the earthquake zone is two important factors that caused cofferdam crashed. Inthe cofferdam seismic stability analysis’ objective is to provide seismic design methodand reasonable measure based on the engineering destructive characteristics anddestructive mechanisms. This paper combined with the earth-rock cofferdam upstreamin Jinsha River of a project, use flac3d numerical analysis software to study the dynamicresponse characteristics and destructive mechanism in the earth-rock cofferdam, Themain work and the results are as follows:(1) Discourse systematically the principles and methods of seismic and seismiccoupling seepage with in flac3d, and compared with the finite element results, theresults showed that: using flac3d to simulate the earthquake response in cofferdam isreasonable.(2) Simulate the cofferdam’s deformation under seismic loads, analyze the seismicresponse characteristics, such as seismic displacement variation, acceleration variationand stress distribution, the location destruction which the earth-rock cofferdam arisepossibly and the entire earth-rock cofferdam stability, the results showed that: thevertical displacement of the earth-rock cofferdam mainly appear in the weir crest at37mbelow; level displacement of the earth-rock cofferdam is significantly greater than thelevel displacement of foundation; the earthquake damage is beginning to weir crest orsurface.(3) Simulate the cofferdam’s deformation under seismic loads coupling of steadyseepage, and analyze the seismic response characteristics, such as seismic displacementvariation, acceleration variation and stress distribution, and the entire earth-rockcofferdam stability, the results showed that: geomembrane is the dividing line of thevertical displacement and level displacement; the partial reinforcement must be taken inthe positive side near weir crest the17m below.(4) Simulate the cofferdam’s deformation under seismic loads coupling ofnon-steady seepage, simulate and analyze the seismic response characteristics, such as seismic displacement variation,under the water level changes in speed of slowlychanges and sudden changes coupling of seismic loads, and the entire earth-rockcofferdam stability, the results showed that: compared with the stable level, whether thewater level is rise or fall the maximum increase amplitude of the vertical displacementand level displacement are quite obvious, the maximum increase amplitude of thevertical displacement and level displacement is large when the water level changes inspeed of slowly changes, but when the water level changes in speed of sudden changesthe increase amplitude decreased.