A 5.5 m thick layer of normally consolidated clay (Cc = 0.15, e₀ = 1.3) has an effective vertical stress of 55 kPa at its mid-depth. A wide fill raises the vertical stress in 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.
Consolidation settlement worksheet with answers
A 5 m thick normally consolidated clay layer (γsat = 19.5 kN/m³, Cc = 0.15, e₀ = 0.75) lies below 3.5 m of sand (γ = 18.5 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 65 kPa. Treat the layer as one sublayer with the stresses at its mid-depth. Find the primary consolidation settlement S in mm.
A 7 m thick overconsolidated clay layer has Cc = 0.5, Cr = 0.04 and e₀ = 0.6. At its mid-depth the effective vertical stress is 75 kPa and the preconsolidation pressure is 105 kPa. A new building adds 140 kPa of vertical stress at mid-depth. Find the primary consolidation settlement S in mm.
A 2 m thick overconsolidated clay layer has Cc = 0.35, Cr = 0.02 and e₀ = 0.7. At its mid-depth the effective vertical stress is 110 kPa and the overconsolidation ratio is OCR = 2. A new building adds 170 kPa of vertical stress at mid-depth. Find the primary consolidation settlement S in mm.
A clay layer 8.5 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 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 4 min. In the field the same clay forms a layer 9.5 m thick. It lies between two sand layers, so water drains out at the top and the bottom. How many days t does the field layer take to reach 50% consolidation?
Answer key
- 1. S = 58.37 mm
- 2. S = 102.1 mm
- 3. S = 706.4 mm
- 4. S = 50.21 mm
- 5. t = 15.32 years
- 6. t = 694.4 days
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