Answer:
A) For a double drainage system the time taken for total settlement will differ from that of a single drainage system, because in a double drainage case clay water escapes from both sides unlike in a single drainage case. hence water and air will be be expulsed faster for a double drainage making it attain total settlement faster.
B) for only single = 12 years
Explanation:
Given data :
ultimate clay settlement = 32 cm
settlement of clay in 3 years = 7.5 cm
Cv ( coefficient of consolidation ) = 1.5 x 10^-4 cm^2 /s
A) For a double drainage system the time taken for total settlement will differ from that of a single drainage system, because in a double drainage case clay water escapes from both sides unlike in a single drainage case. hence water and air will be be expulsed faster for a double drainage making it attain total settlement faster.
note : Total settlement is the same in both drainage system.
<u>B) Determine how long it will take for 7.5 cm of settlement to occur if there is only single </u>
applying the relation below
Tv = Cv t / H^2
where Tv = time factor , d = thickness of layer , H = drainage path
Given that Tv and Cv are constant in both cases
t ∝ H^2 hence
------ ( 1 )
t1 = time for single drainage for d meters , t2 = time for double drainage for d meters
equation 1 can be rewritten as
t1/t2 = d^2 / (d/2)^2
∴ t1 = 4t2
given that t2 = 3 years ( value gotten from question )
t1 = 4 * 3 = 12 years
