stability control of narmab dam and sensitivity analysis of reliability coefficients

static and quasi-static stability analysis of embankment dams is of vital importance in different stages of dam’s design, construction and operation. the stability can be studied using different techniques which are generally analyzed through limit equilibrium method. base on this main method, the critical slip surface is selected and the shear strength required to counter the slip at the selected surface is obtained and compared with shear strength of the soil at that surface in order to obtain confidence coefficient. in the present research, the geo-studio slope/w software that is a geotechnical software based on finite element method and is widely used in geotechnical field, is employed in order to analyze the stability of the body and foundation of narmab dam in golestan province. narmab dam is a homogeneous embankment dam with a height of 60 m, crest length of 807 m and reservoir volume of 115 million cubic meters. the confidence coefficients provided by the software are compared to the permissible confidence coefficients. moreover, the sensitivity of the confidence coefficients values to the changes in the effective factors, adhesion and internal friction coefficient, is analyzed. the analyses were performed on 8 values (±5, ±10, ±15, ±20) of c and φ and the obtained values of confidence coefficients were compared. in addition, a comparison was made between different methods of stability analysis. according to the static and quasi-static conditions, narmab dam is stable in all loading stages (end of construction, first impounding and steady state seepage and in general, only for the static conditions of the end of construction stage, the sensitivity of adhesion is greater than the angle of internal friction, but, in other conditions and stages, the sensitivity of friction angle has more effects.