Question

In: Civil Engineering

(a) At a reclamation site, a 6-m thick sand layer overlies a 5.8-m thick clay layer,...

(a)
At a reclamation site, a 6-m thick sand layer overlies a 5.8-m thick clay layer, which is underlain by impermeable rock stratum. The water level is initially 2.5 m above the ground surface. The saturated unit weights of sand and clay are 19 kN/m3 and 17 kN/m3, respectively. A 5-m thick layer of fill will be placed on the original ground surface, and the unit weights of fill are 19 kN/m3 and 20 kN/m3 above and below water table, respectively. Determine the water pressures and effective vertical stresses at the middle of clay layer (i) immediately after the fill is placed, and (ii) many years after the fill is placed.
(b)
Following part (a), the clay has an initial void ratio of 1.02, with compression index (Cc) of 0.34 and recompression/expansion index (Ce) of 0.073. It is also found to be overconsolidated, with OCR of 1.23 throughout the entire layer.
i. Making use of results from part (a) and considering stresses at the middle of clay layer, determine the final consolidation settlements of the clay.
ii. Assuming instantaneous loading (no need to correct for construction time), estimate the consolidation settlements after 12 months and 36 months, if the coefficient of consolidation (cv) equals 1.5 m2/year.
iii. Now consider the necessary correction for a construction period of 10 months. Counting from start of fill placement, how long does it take for 65% consolidation to complete?
iv. For the corresponding stress range, what will be the equivalent value of coefficient of volume compressibility (mv) in m2/MN?

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Expert Solution

Ally Wells answered 10 months ago
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