Analysis On Stress Deformation Of Composited Geomembrane Core Wall Rock-fill Dam

The composited geomembrane core wall rock-fill dam is one of the important dam typesin hydraulic structures, because it has many features such as obtaining easily dammingmaterials, simply mechanized construction, short construction period, low cost and so on andthe composited geomembrane core wall has many advantages, such as good capacity adaptingto the deformation, acid and alkali resistance, anti-erosion, anti-aging, anti-seepageperformance, etal. So far it has been widely used in water conservancy and hydropowerprojects. However, the problem of stress deformation of composited geomembrane core wallrock-fill dam will also become a core issue of its design and construction.This paper describes briefly the characteristics of rock-fill dam and research status ofgeomembrane impervious body. According to the previous studies results,comparing toselect Duncan-Chang E Bmodel as the constitutive model of rock-fill body, thecomposited geomembrane and contact surface are simulated by geotextile grid cell andGoodman unit, and demonstrating the application of modal response spectrum method inrock-fill dam seismic response analysis. Based on the soil theory and traditional finite elementmethod, the paper takes some composited geomembrane core wall rock-fill dam inBailongjiang as an example, building a three-dimensional finite element model andcombining with MIDAS/GTS large geotechnical analysis software, the stress deformation ofcomposited geomembrane core wall rock-fill dam is simulated under three kinds of conditionswhich are the completion period, normal storage period and normal storage period with8degrees earthquake, the stress deformation laws of the dam are calculated under nocircumstances membrane,and analyzing the stress deformation effect of compositedgeomembrane on dam.By analyzing the results: in the completion period, the stress and deformation of dam andcomposited geomembrane are very small and basically symmetrical distribution, they expressthat pressure status do not occur tensile failure, the dam maximum stress occurs at the end ofthe dam, displacement expresses mainly the settlement deformation, and the maximumsubsidence occurs in two-thirds of the dam, while the composited geomembrane is impactednot only by its own weight, but also is dependent on the dam deformation which is larger thandam’s; in normal storage period, because of water pressure, the stress and deformation are nolonger symmetrical distribution, and substantially occurring near the water pressure surface。Composited geomembrane and dam performances in more parts of water level to moveupstream are tensile stress, under water level is still pressure stress and moves downstream.However, whether completion period or the normal storage period, the minor principal stressof dam and geomembrane is all compressive stress, only major principal stress occurs local tension, the dam occurs at the bottom, and the geomembrane occurs in dam or mountainconnection site. After plusing8degree earthquake, the tensile stress zone expands, damtensile stress mainly is located in the main part of rock-fill zone, the geomembrane stillappear in connection site with adjacent members, the deformation in the horizontal directionof the dam and the core wall moves overall downstream, while emerges elevation phenomenain the vertical direction. Under no circumstances membrane, stress deformation law isbasically the same with circumstances membrane, but the stress and deformation are increased.Thus: in the three conditions, both the dam and geomembrane emerge stress in turn from theinitial compression state, the tensile area expands under the earthquake, and the tensile stressincreases。Geomembrane in the joints appears a clear stress concentration; deformation isfrom the initial overall settlement deformation and the transition to local level and thenswarmes into the overall level and upper state; deformation of the films are mainlydependent on the dam deformation in addition to their deformation. Compared with the nomembrane situation, the composited geomembrane plays not only the impermeable role, hasgreatly improved the stress and deformation of dam, largely inhibiting stress and deformationof the dam.