Question

19. In order to determine the factor of safety of the d/s slope during steady seepage, the section of a homogeneous earth dam was drawn to scale of 1 cm = 10 m; and the following results were obtained on a trial slip circle. Area of N-diagram = 12.15 sq cm. Area of T-diagram = 6.50 sq cm. Area of U-diagram = 4.02 sq cm. Length of arc = 11.60 cm The dam material has the following properties : Effective angle of internal friction = 26° Unit of cohesion = 19.62 m2 Unit weight of soil = 19.62 m2 Determine the factor of safety of the slope. (Ans. F.S. 1.21)

Answer 1

Solution: - 1. ..! - Scale Iim = lom i'. x + 1o'mi i i. consider 1 cm length of the dam. EN - An 2²r. = 112.15 a 10² x 19.62 ) 1 , 238 38.3 KN ET = Aga²r 6.50x 10 x 19.62 ł 12753 KN Eu = Au 2² rw = 4,02 x 10² x 9,81 = 39 43.62 Î = 11.60 x 10 =116 m. Also, it was given; e'= 19062 kN/m² & p = 26° Cool factor of seifet y of is given by el + tand' EN-u) F = 19:62 X 116 + (23838,3 - 3943.62 ) tem 26° 12753 - 0.939 Hence, factor of safety. of the s slope 0.939 Aus