The evaluation of mechanical behavior of Marun Dam using three-dimensional numerical analysis

An earth/rockfill dam is always located in a valley of a river which can have different shapes as a natural structure. Valleys normally appear regularly or irregularly and they can be idealized in the shapes of V, U, rectangular and etc. the shape and type of the valley affect all steps of a dam project, from initial studies up to construction and dam behavior. Consequently, the shape and size of the valley as an effective factor should be considered in all steps of the project because narrow valleys are the circumstances which are always a barrier of constructing the earth dams. So the behavior of earth dams in narrow valleys is affected by 3D effects of valley. The geometry of dam and especially the ratio of crest length to dam height are affecting the 3D behavior. Consequently 3D analysis seems to be necessary for large dams in narrow canyons. Current paper is an attempt on estimation of the 3D effects of narrow valley on the behavior of Marun rockfill dam with crest length of 345m and height of 165m (L/H=2.1), which is located in the south west of Iran. In accordance with this goal, 2D and 3D analyses of dam have been carried out by FEM method and the results are compared with each other. According to the analyses results it’s seemed that in the narrow valley of Marun dam, there are some 3D effects which couldn’t be applied to the model through 2D analysis. Both of analyses showed a same trend for results and the reductions and increases were the same. But the eye taking difference between these two analyses was the overestimation of results of 2D analysis. Both displacements, vertical and horizontal ones, in 2D analysis results were more than 3D values and even more than natural values. Comparison of results may confirm the necessity of 3D analyses for these types of dams. It could be stated that an earth dam in a narrow canyon is a structure which should be considered as a 3D volume. In this situation, the 3D effects applied with the valley aren’t negligible and a 2D analysis cannot include this 3D behavior and would result in overestimated results which aren’t reasonable at all. Anyhow, the results of this article belong to a case study which has its special conditions and wouldn’t be applied for all the dams in narrow valleys because each case has its certain conditions and consequently its different manner.