Internal Erosion Occurs Due to the loss of Soil Particles As a result of Seepage phenomenon. Existing dam safety has been one of the most important hydro system engineer's worries and identification of serious accidents which may cause dam failure, is very crucial. To assess the probability of internal Erosion, the risk analysis can be utilized. Monte-Carlo simulation is one of the tools which can quantify the risk analysis result due to uncertainties in the Geotechnical engineering soil parameters. In the present study, the probability of dam failure and the reliability analysis of dam was estimated against internal erosion. FLAC software has been used together with Monte-Carlo simulation to Compute exit gradient and effective stress in the toe of dam. A case study, namely, Doosti Dam in Khorasan Razavi Provence, Iran has been considered. The analysis procedure also verify with instrumentation data which were installed in section 2–2. As a result and Based on the numerical analysis, it shows that the dam has above average reliability index, β=2.7, against internal erosion in outlet of horizontal drainage.


In recent years, headline news has been overwhelmed with stories about dam and levee failure, which is caused by initiation erosion in body or foundation of dams, including the 2005 levee breaches in New Orleans, the 2006 Kaloko dam failure in Hawaii and the 2008 Redland Dam failure in Arizona. Since 2000, state and federal agencies have reported 92 dam failures in the United States to the national performance of dams program (NPDP, 2007). Incidents such as these have brought both national and worldwide attention to the need of prediction for embankment dam and levees failure. The two most common causes of earthen embankment and levee failure are overtopping and internal erosion (Fell et al., 2003).

According to high prices of dam projects, it is more important to evaluate the workability of dams during their life. Risk and reliability are two major concepts in hydro system engineering. Reliability can be defined as a probability of non-failure. Therefore by increasing the probability of system failure the reliability of system will decrease. Estimation of system reliability needs many statistical tools because it always reports as a probability and it is necessary to have sufficient knowledge about the probability theory and statistics rules. Load forces and resistance of a system are two main part of the risk and reliability analysis. Moreover due to uncertainties in geotechnical parameters evaluating of load and resistance are complicated. Monte-Carlo simulation is one of the practical tools for estimating these parameters to analyzing risk and reliability.

In this paper first we proceed Internal Erosion Background and Reliability analysis, after that by using Finite difference program (FLAC) with help of Monte-Carlo simulation we evaluate the Reliability of Internal erosion in Doosti dam.

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