At a reclamation project site, the seabed is found to be 6 m below the water level. A layer of soft clay, which is 5 m i

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At A Reclamation Project Site The Seabed Is Found To Be 6 M Below The Water Level A Layer Of Soft Clay Which Is 5 M I 1 (146.82 KiB) Viewed 21 times

At a reclamation project site, the seabed is found to be 6 m below the water level. A layer of soft clay, which is 5 m in thickness, overlies a stiff stratum of permeable sand. The saturated unit weight of the soft clay is 15 kN/m². A layer of fill material will be placed above the original seabed. The fill material has a unit weight of 18.5 kN/m when saturated, and 18 kN/m when above the water level. The reclamation design requires the final ground level to be 2 m above the water level, considering the consolidation settlements caused by the fill placement. (1) If the fill thickness is 8.5 m, estimate the effective vertical stress and pore water pressure at the middle of clay layer, immediately after fill placement and many years after fill placement (4 marks) (ii) The volume compressibility (my) is originally assumed to be 1.0 m²/MN for the entire clay layer. Determine the consolidation settlements in the clay. Are the project requirements on final ground level fulfilled in this case? (3 marks) (iii) The value of my was later found to be 1.7 m²/MN. Discuss, with calculations, how that would affect your reclamation design in terms of fill thickness and consolidation settlements. (7 marks) (iv) The coefficient of consolidation (C) of the clay is found to be 1.25 m²/year. Assuming instantaneous loading (i.e. not necessary to correct for construction period), estimate the time required for 25% and 75% of the consolidation settlements to complete. (4 marks) (v) The construction period will take 12 months. Revise the estimates on time required for 25% and 75% of the consolidation settlements to complete. (4 marks) (vi) Suggest one engineering measure to accelerate the consolidation process, and explain why it would be effective. (3 marks) Relationship between time factor (Tv) and degree of consolidation (U): T, = 1 U2 U <0.6 -0.933 log(1 - U) -0.085 U > 0.6