Question

Problem 13 a. Draw the flow net for the dam shown below (datum is at the 54 ft bedrock-soil interface). The dam has a 36-ft sheet pile driven into the granular soil layer. Redraw the schematic to scale. Use solid 24 ft 21 ft lines to indicate flow lines and dashed lines to indicate Soil equipotential lines. b. Calculate the rate of seepage at 36 ft the exit of the dam in ft/day per 60 ft Sheet pile unit width of the dam (into the plane of the page). The hydraulic conductivity of the soil is 1.5x10-5 WWWWWWWWABedrock ft/s. c. Suppose that the saturated unit weight of the soil is 120 lb/ft3. Do you expect piping to occur at the dam exit?

Answer 1

24t 2.147 1567 1. Nd - I - TI > flow lines - No.of fiew lines 23,NA ---- No.of equipotential lines = 10, Nd from figure H = 21 ++; k = 1.5x165 H/sec b) q= k H2 NF = 1,5*10***21* & fi dee per unit .. width of dam 9- 9.45x10x xGOxG0X 24 1 (60X 60X24) day 9 = 8.16 ## dan per unit witth of dam c) Vsay = 12000lt² rw = 62-4eb1|t² 'sat VW 120-62-4 = 0192 1 rw 624 Fosic toxit = Head hou during flow auwse the end field equare Length of flow in the end Field Square = 18+ les 2 from flownet Tw FOS = Texit - 0.13

fos = ic i e 0.92 = 7007 Di13 No piping occurs