Question-4: (a) The time required for 50% consolidation of 25mm thick clay layer (drained at both...

 

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Question-4: (a) The time required for 50% consolidation of 25mm thick clay layer (drained at both top and bottom) in the laboratory is 2 minutes and 20 seconds. (i) Determine how long (in days) will it take for a 3m clay layer of the same clay in the field under the same pressure increment to reach 50% consolidation? In the field, there is a rock layer at the bottom of the clay layer. [CLO 3] (ii) Determine how long (in days) will it take in the field for 30% primary consolidation to occur? [CLO 3] [2.5] (b) A 12 meter thick layer of clay is half closed from the bottom. The coefficient of consolidation C 8x10-8 m/sec. The initial excess pore water pressure is uniform and is equal to 100 kPa. Find the average degree of consolidation and excess pore water pressure for the clay 5 years after loading at depths 3, 6, 9 and 12 meters. Z = z/d 1 15 -T-0- T-0.051 170 0.1 0.10 0.15 0.20 0.30 0.40 0.50 0.60 200 0.2 0.3 13 0.801 -0.848 0.70 0.90 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Consolidation ratio U, [CLO 3] [2.5] Question-4: (a) The time required for 50% consolidation of 25mm thick clay layer (drained at both top and bottom) in the laboratory is 2 minutes and 20 seconds. (i) Determine how long (in days) will it take for a 3m clay layer of the same clay in the field under the same pressure increment to reach 50% consolidation? In the field, there is a rock layer at the bottom of the clay layer. [CLO 3] (ii) Determine how long (in days) will it take in the field for 30% primary consolidation to occur? [CLO 3] [2.5] (b) A 12 meter thick layer of clay is half closed from the bottom. The coefficient of consolidation C 8x10-8 m/sec. The initial excess pore water pressure is uniform and is equal to 100 kPa. Find the average degree of consolidation and excess pore water pressure for the clay 5 years after loading at depths 3, 6, 9 and 12 meters. Z = z/d 1 15 -T-0- T-0.051 170 0.1 0.10 0.15 0.20 0.30 0.40 0.50 0.60 200 0.2 0.3 13 0.801 -0.848 0.70 0.90 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Consolidation ratio U, [CLO 3] [2.5]