Question

You are working on a construction site for GDOT, where an embankment will be built on a deposit of soft clay that is 4 ft thick. The clay is drained only at the top of the deposit.

(2a) If the proposed embankment is 30 ft tall and has a bulk unit weight γ = 108 pcf, then determine the initial increase in pore water pressure caused by the construction of the embankment.

(2b) Calculate the time for the clay to reach 90% consolidation, given Cv = 2.5x10-8 ft2 /sec.

100 80 Triangular initial excess porewater pressure 2 60 2 40 Uniform initial excess porewater pressure 20 Arrows show drainage direction 0 0.2 0.4 0.6 0.8 0

Answer 1

Given that hick = 4ft embankment = 30ft unit weight gamma = 108 pcf (a) the initial increase in pore water pressure caused by construction of dam The whole pressure will be take b pore water pressure 30 times 108 = 3240 pcf ft (b) c_2 = 2.5 times 10^- 8 ft/sec \r\n Time factor is TV = 1.781 = 0.9331 log(100 - v1) = 1.781 - 0.933 log(100 - 90) = 1.781 - 0.933 log (10) = 1.781 - 0.933 times (1) = 1.781 - 0.933 = 0.848. the day is draining from top & bottom sad = 4/2 = 2ft t = 0.848 times 2 times 2/2.5 times 10^- 8 = 3.392/2.5 times 10^- 8 = 135680000