0 Laz 3. A 40 ft layer of silty clay is overlain by 5 ft of sand and underlain by siltstone bedrock. Water table is at ground surface. The initial vertical effective stress ovo' and maximum past pressure Ovm' profiles with depth are plotted in the Figure to the right. 1D consol- idation test results yielded the following: Cc virgin compression index = 0.55, CR recom- pression index = 0.072 and initial void ratio eo=0.91. A vertical surcharge load p of 1400 lb/ft2 is placed on top of the ground over a wide area. To estimate the settle- ment in the clay, 4 sublayers are used each depth (ft) 10 stress (lb/ft2) 1000 2000 profile 3000 400 sand layer 1 20 -m clay layer 2 layer 3 30 40 50 layer 4 10 ft in thickness. Layer 1 is from 5' to 15' depth, layer 2 from 15' to 25', layer 3 from 25' to 35' and layer 4 from 35' to 45' depth. (a) Using the Figure above, estimate the initial ovo', maximum past pressure Ovm' and final ouf', after loading at the midpoint of layer 4 (you don't need to calculate ovo'; just use the Figure). Initial ovo max. pp vm' final ovf' (b) Estimate the final consolidation settlement pct for layer 4 due to the surcharge loading p (don't esti- mate settlement for the other 3 layers). = (c) The coefficient of consolidation c, 5.0 ft/year for the clay. Assuming the siltstone is impervious, how long will it be before the average degree of consolidation U of the entire 40' clay layer is 40%? (d) For the condition in (c), what is the excess pore pressure u, at the midpoint of the 40' clay layer?