Evaluation of Chahchahe Earth Dam Behaviour during Construction and First Impoundment Stage Using the Results of Monitoring and Back Analysis

The study of earth dams behavior during the construction, completion and also the first impoundment as one of the most critical times during the life time of the dam because of the stress and water pure pressure in the core and also water level in this period has special importance. For this purpose, the behavior of the Chahchahe dam was studied by using of obtained results from monitoring recorded data and back analysis was done by GeoStudio finite element software. This dam is an earth dam with core clay and its maximum height is 47 meters from the natural bed of river. Chahchahe dam which has been constructed on Chahchahe river is located in the Kalat basin watershed, in 95 kilometers northeast of Mashhad. In order to consider the parameters in design process and simulate as real conditions of dam construction, back analysis was done base on the results of monitoring to can be predict the behavior of dam. In this study, the comparison of numerical model and monitoring results show acceptable and suitable accordance, so that the amount of settlement in the clay core was obtained 65 cm from monitoring result and evaluated 66 cm by numerical model. Also, the maximum stress at the 530 meter level in the core was read 820 kPa, which was calculated 950 kPa based on the numerical model at the same level, and in all of cases, the obtained values from numerical models are as confidence.