A 3.5 m thick layer of normally consolidated clay (Cc = 0.6, e₀ = 1.35) has an effective vertical stress of 100 kPa at its mid-depth. A wide fill raises the vertical stress in the clay by 110 kPa. Treat the layer as one sublayer with the stresses at its mid-depth. Find the primary consolidation settlement S in mm.
Consolidation settlement worksheet with answers
A 3 m thick normally consolidated clay layer (γsat = 17.5 kN/m³, Cc = 0.4, e₀ = 1.15) lies below 4 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 135 kPa. Treat the layer as one sublayer with the stresses at its mid-depth. Find the primary consolidation settlement S in mm.
A 6 m thick overconsolidated clay layer has Cc = 0.45, Cr = 0.02 and e₀ = 0.65. At its mid-depth the effective vertical stress is 95 kPa and the preconsolidation pressure is 215 kPa. A new building adds 80 kPa of vertical stress at mid-depth. Find the primary consolidation settlement S in mm.
A 4 m thick overconsolidated clay layer has Cc = 0.5, Cr = 0.02 and e₀ = 1.2. At its mid-depth the effective vertical stress is 120 kPa and the preconsolidation pressure is 150 kPa. A new building adds 180 kPa of vertical stress at mid-depth. Find the primary consolidation settlement S in mm.
A clay layer 6.5 m thick has a coefficient of consolidation cv = 1 m²/year. It lies between two sand layers, so water drains out at the top and the bottom. For 50% average consolidation the time factor is Tv = 0.197. How many years t does the layer take to reach 50% consolidation?
In a laboratory oedometer test, a clay specimen 25 mm thick, drained at the top and bottom, reaches 50% consolidation in 10 min. In the field the same clay forms a layer 5.5 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?
Answer key
- 1. S = 287.9 mm
- 2. S = 236.8 mm
- 3. S = 19.3 mm
- 4. S = 277.2 mm
- 5. t = 2.081 years
- 6. t = 1344 days
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