For the concrete Dam shown in figure, determine the total average seepage for the given permeable strata by drawing Flow Net. The detail dimensions are given on the figure. The head of water on upstream side is 6ft and on downstream side is 1ft. Assume of Nf= 3, Nd= 6 and rectangular flow elements.

 

Q#:For the concrete Dam shown in figure, determine the total average seepage for the given permeable strata by drawing Flow Net. The detail dimensions are given on the figure. The head of water on upstream side is 6ft and on downstream side is 1ft. Assume of Nf= 3, Nd= 6 and rectangular flow elements. 

Solution#

 ANSWER 

 SOLUTION

For rectangular channel

n=b/L = 2/4 =0.5

seepage equation for rectangular chanel                                                                           

 

                                                                                                                 k = 4×10^-4 ft/day

q = kH (Nf / Nd)                                                                                       H = h₁ - h₂

                                                                                                                 H = 6-1 = 5

No. of potetial drop = 6                                                                           Nf =  3

No. of Flow lines     = 3                                                                           Nd = 6

H = 6 - 1 = 5'

 

Rate of Seepage

 

 q = nf / nd kh

  

q = 3/6×4×10^-4 × 5

 q = 1×10^-3 ft³ /day/ft