Question

i) How high the water will rise if piezometers are placed at points a, b, c and d, indicated in the figure shown below (set the datum at the ground surface)? ii) What would be the total energy head at points a, b, c and d? iii) What would be the pore water pressures at these points if the discharge velocity is neglected? Use distance estimates based on the scale of the figure. Sheet pile 5 m Ground surface 11.5 m MI 10 m a 3! Impermeable layer

Answer 1

5m patuno Ground Surface M om anh I 13 14 sd Impermeabte tager - Static head 5-1.5 = 3.5m. No. of potential drops = 6 Hence loss of head per potential drop = 3.5

* wpto boibt'@ head loss=no. of botential drop xhead loss per potential drop = 1 x 3.5 - 7 m 6 22

I rise of water in brezometer = 5-7 = 4-417m . above ground surface 72 similarly for point 6 head loss = 2x 3.5 = 1.167 m rise of water is biezometer = 5-1. 167 above ground surface = 13.833m * similarly for point ® head loss = 5x 3-5 = 2.917m. rise of water in piezometer above ground surface = 5-2-997 = 12.083m

* Similarly for @ as ☺ cand are on saine equipotential potential line. Hence rise inill be same. = 12.083ng _Total Energy_heads: Zet at 6 let distance from Ground = 5m Ha= -5 + Yw (5+5) - head loss] yw Ha sm Ha= -5+ 10 7 = 14.417m 12 Ang at (distance from Ground = zosm) H = -7.5+ yw (5+7.5-head loss) Hb = -7.5+ 125-1167=13.833ml

ato (distance from Ground = 2.50) He= -2.5 + Yws (1-5 + 2.5 + head loss) Yet to occur Yw { here due to upward seepage at "C" 7 we have used positive lread Loss I which is yet to occur beyond "C" He-25 + 4 + 1X 3-5 = 2.083 m at D Cdistance from Ground = gom) Ons Hd = -10 + Ywl 1.5+ 10+ head loss ton occur bey and d) Hd = -10 + 11-5 t 3-5 083 m pore water pressure at Va= Yo[ S+S-7 ] = 92.38 kg

at 6 as un= yw [5+7.5 – :967] U = 111.18 KN m ? ate 1 Uc= Yu [2.5 +1.5 +3.5) do 6 Uca 44.96 KN m2 ato UAE yw [1-5+10 +3.5) d = 118.5 37 KN ma