http://www.jofamericanscience.org s) 2013;9(3 Journal of American Science 63 Combining Appropriate Soil Behavior Models for simulating Taham Rockfill Dam Mohammadkeya Khosravi 1 , Dr. Mohammad Hadi Davoudi 2 , Akbar Pashazadeh 3 1 Lecturer of Islamic Azad university-Tehran Jonoub Branch, Tehran, Iran 2 Associated Professors, Soil Conservation and Watershed Management Research Institute, Iran 3 Young Researchers Club, Central Tehran Branch, Islamic Azad University, Tehran, Iran * kh.mkia@gmail.com Abstract: Studies over determining the behavior and modeling the rock fill dams have always been of great importance, because the built dam shows a 1:1 physical model of the real behavior of a dam and evaluating the behavior of such dams in of prior importance for organizing the principles of designing and introducing new experiences. In this paper the instrumentation system for monitoring of Taham dam is thoroughly examined, which includes: pressure cells and electric piezometers in the critical section of the dam. The recorded results of instrumentation and monitoring system of the dam are as well evaluated. Based on the dominant facts over the project and by applying the technical features of the design and engineering interpretations, technical judgments and filtration is done over fine and possibly damaged (of no right function) instruments. Then based on mechanical parameters of the materials (according to the report of the design stage) and using Geo-Studio software the behavior of the dam is modeled. Numerical analyses are done by using three behavioral models: linear-elastic model, cam- clay model (combined with linear elastic model) and elastic-plastic model in two loading modes of: 1-whole loading process and 2-step-loading process. The body of the dam is considered in two forms of homogeneous and inhomogeneous. In the second mode (inhomogeneous) the geometry of changes of material properties inside the core is supposed vertically. But the geometrical changes in the material properties inside the shoulders supposed in two different alternatives: the first one has the vertical direction of the layers (of filling) and the second one forms right angle with the direction of the stress counters. Comparing the results of the all models with observation data (summaries of instrumentations) shows that the use of elastic-plastic behavioral model, is known to be as the best alternative, if done step-loading and considered as inhomogeneous material in a way that: the changes of material properties inside the core reapplied in the vertical direction and the direction of changed materialism shoulders should form a right angle with the direction of the stress counters. [Khosravi Mk, Davoudi MH and Pashazadeh A. Combining Appropriate Soil Behavior Models for simulating Taham Rockfill Dam. J Am Sci 2013;9(3s):63-70]. (ISSN: 1545-1003). http://www.jofamericanscience.org . 9 Keywords: rock-fill dams, monitoring, numerical modeling 1-Introduction Tendency for monitoring the rock fill dam bodies for organizing the designing principles and introducing new experiments had been always, and is still, focused by dam building staff. In Iran, too, several case studies on some dams have been carried out and their resulted data have been broadcasted in the few past years, and the aim of the present research was the possibility to provide an acceptable database on organizing the designing principles of soil dams. Such researches have been led by Dr. Mirqasemi and his coworkers during 2003 to 2004, within which the instrumentation systems of “Lar” and “panzdah-e- khordad” dams have been evaluated. A study over “Taham dam” had also been done by FarzinKarimi and AbbasSorush from Amir-Kabir University, they have used “Flac” software, but in their method of modeling; making of the layers and applying the inhomogeneity in the shoulders and in the core have not been focused as one of the main goals. In this paper, pressure cells and electric piezometers of Taham dam is thoroughly examined in the critical section of the dam. 2-Dam Features and Methodology 2-1. Technical Properties of Taham Dam: This dam is a rock fill dam with a watertight clay core with the height of 124 meters, crest length of 458 meters, heel width of 535 meters, body volume of 128 million square meters, the maximum unload capacity of 1000 square meters per second, and is located 15 kilometers far from north of Zanjan. The materials which make the body of the dam are as follows: A. Impervious RCC concrete joint between the core and the foundation B. Impervious core, which is consisted of a watertight clay core with a very low permeability of about 10 E -7 to 10 E -8 cubic cm per second. C. Filters D. drainage in the downstream