Question

Q3. A sand sample of 35 cm2 cross sectional area and 20 cm long was tested in a constant head permeameter. Under a head of 60 cm, the discharge was 120 ml in 6 min. The dry weight of sand used for the test was 1120 gm, and Gs = 2.68. Determine (a) the hydraulic conductivity in cm/sec, (b) the discharge velocity, and (c) the seepage velocity.

Subject: Geotechnical Engineering (soil mechanics).

Answer 1

liiven data: Area of sand sample, A= 35 cm length of sample, L= 20cm head, h= 60cm sis charge, O=12ome in t= 6min S O=120 cm in t= 360 seconds dry weight of sand, Md = 1120gm les=2.68 a) hydraulic conductivity, K= OL k=120x20 35x60x 360 k= 3.175% 1019 cm/sec b) Discharge velocity, U= kxi Where: iz hydraulic gradient = h 2 = 60 = 3 V- 3.175 x 103x3 | V= 9.52 x 103 cm/sec. I Aht

c) Seepage velocity, Us=Y - Where: me porosity Now dry und weight of sand Vd = Maxg - 1120x9.81 kN/m volume AXL Va = 1120 x9.81 kN/m Vd = 15.7 kN/m² Nd= lis Vw e=void Ite 15.7 = 2.68x9.81 ratio Ite or n= e= 0.675 e = 0.675 = Ite = 0.403 +0.675 : Vs = v= 9.52 x 10 0.403 culs Vs = 0.0236 cml