A Study on Efficacy of Design Charts in Slope Stability of an Earthen Dam

Slope stability is a matter of tremendous concern in construction of earthen dams where the failure of slopes may incur severe loss of life and damage to property and should be designed in such a way that it satisfies both safety and economic consideration. The basic design requirement of earth dam is overtopping, stability analysis and seepage control. Slope stability chart are useful for preliminary analysis before using a computer programme to determine the approximate values of the Factor of Safety (FoS) as it allows some quality control and a check for the subsequent computer-generated solutions (Salmasi F, Pradhan B, Nourani in Prediction of the sliding type and critical factor of safety in homogeneous fnite slopes. Applied Water Science Journal 9:158–169 [1]). Another use of slope stability charts is to back calculate strength values for failed slopes to aid in planning remedial measure. The various design charts available in literature are Taylor stability chart, Spencer Chart, Bishop and Morgenstern Chart, Michalowski Chart etc. The primary objective of the study is to identify the stability of a proposed homogeneous earthen dam composed of low compressibility clay (CL) to be constructed in Eastern Part of India. The study focusses stability of adopted section for End of Construction, Steady State Seepage and Rapid draw down condition using SLIDE 2D (Rocscience) software (Bishop Method) as well as with design charts. In the present study, Taylor Chart for End of construction condition, Bishop and Morgenstern Chart for Steady state seepage condition and Morgenstern Chart for Rapid draw down condition have been used.