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Name: ____________________ Date: ____________
1.Easy
A 4 m thick normally consolidated clay layer (γsat = 18.5 kN/m³, Cc = 0.4, e₀ = 1.3) lies below 4.5 m of sand (γ = 17.5 kN/m³). The water table is at the top of the clay; use γw = 9.81 kN/m³. A wide fill raises the vertical stress throughout the clay by 25 kPa. Treat the layer as one sublayer with the stresses at its mid-depth. Find the primary consolidation settlement S in mm.
sand: Hs = 4.5 m, γ = 17.5 kN/m³clay: H = 4 m, γsat = 18.5 kN/m³γw = 9.81 kN/m³Cc = 0.4e0 = 1.3Δσ = 25 kPa
S = mm
2.Easy
A 5 m thick normally consolidated clay layer (γsat = 17.5 kN/m³, Cc = 0.45, e₀ = 1.3) lies below 3 m of sand (γ = 17 kN/m³). The water table is at the top of the clay; use γw = 9.81 kN/m³. A wide fill raises the vertical stress throughout the clay by 125 kPa. Treat the layer as one sublayer with the stresses at its mid-depth. Find the primary consolidation settlement S in mm.
sand: Hs = 3 m, γ = 17 kN/m³clay: H = 5 m, γsat = 17.5 kN/m³γw = 9.81 kN/m³Cc = 0.45e0 = 1.3Δσ = 125 kPa
S = mm
3.Medium
A 2.5 m thick overconsolidated clay layer has Cc = 0.25, Cr = 0.02 and e₀ = 0.95. At its mid-depth the effective vertical stress is 85 kPa and the overconsolidation ratio is OCR = 3. A new building adds 30 kPa of vertical stress at mid-depth. Find the primary consolidation settlement S in mm.
A 7.5 m thick overconsolidated clay layer has Cc = 0.25, Cr = 0.03 and e₀ = 1.05. At its mid-depth the effective vertical stress is 55 kPa and the preconsolidation pressure is 155 kPa. A new building adds 160 kPa of vertical stress at mid-depth. Find the primary consolidation settlement S in mm.
A clay layer 4.5 m thick has a coefficient of consolidation cv = 0.8 m²/year. It lies between two sand layers, so water drains out at the top and the bottom. For 90% average consolidation the time factor is Tv = 0.848. How many years t does the layer take to reach 90% consolidation?
In a laboratory oedometer test, a clay specimen 19 mm thick, drained at the top and bottom, reaches 50% consolidation in 5 min. In the field the same clay forms a layer 3 m thick. It lies on impervious rock, with sand above it, so water drains out only at the top. How many days t does the field layer take to reach 50% consolidation?