Q4. A rigid strip footing is constructed on alayered soil deposit, as shown in the figure.
Before construction of the footing, laboratory tests on asaturated clay sample, taken at a depth of 6 m below the groundsurface, gave the following results:
- Compression index: Cc = 0.3,
- Recompression index: Cr = 0.08
- Over consolidation ratio: OCR = 1.5
- Water content: w = 25%
- Specific gravity: Gs = 2.65
Saturated unit weight of clay: gsat = 19.5kN/m3
- Calculate the settlement of the footing due to deformation ofthe sand layer only. Sand properties are asfollows:
- Total unit weight: gt = 18 kN/m3
- Young’s modulus: Es = 30MPa
- Poisson’s ratio: n = 0.25
- Based on the elastic theory (Boussinesq’s equation), calculatethe change in vertical stress at point A long time after applyingthe surcharge load.
- Using the theory of 1-D consolidation, calculate the totalsettlement of this rigid footing due to consolidation of the claylayer only, long time after applying the total load.
