Question

In 1951, a small approach embankment was constructed for a highway bridge over a river south of Los Angeles. The embankment was underlain by 5 ft of organic clay. Records of the settlement rate indicate that 90% of the consolidation settlements occurred in the first 4.5 years after construction. A new bridge over the river is now planned for a site a few hundred yards from the old bridge. The approach embankment to the new bridge will be underlain by 20 ft of the same organic clay found at the old bridge site. Estimate the time required to achieve an average degree of consolidation of 90% under the new embankment. Assume single drainage from the organic clay at both sites..

Answer 1

72 years

Step-by-step explanation:

The degree of consideration is the same for both bridges = 90%

Height of first highway bridge( d1 ) = 5 ft

Time to consolidation ( t1 )= 4.5 years

Height of second bridge ( d2 ) = 20 ft

Time to consolidation ( t2 ) = ?

we will apply this relation below

Tv = Cv * t / d^v

Tv = constant

for a single drainage condition : t ∝ d^v hence; d = H

∴
`(t_(2) )/(t_(1) ) = ((d_(2) )/(d_(1) ))`^2

t2 = t1 ( d2/d1 )^2

= 4.5 ( 20 / 5 )^2

= 72 years