Question

In: Civil Engineering

Q4. A rigid strip footing is constructed on a layered soil deposit, as shown in the...

Q4. A rigid strip footing is constructed on a layered soil deposit, as shown in the figure.

Before construction of the footing, laboratory tests on a saturated clay sample, taken at a depth of 6 m below the ground surface, 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 = 19.5 kN/m3

  1. Calculate the settlement of the footing due to deformation of the sand layer only. Sand properties are as follows:         
  • Total unit weight: gt = 18 kN/m3             
  • Young’s modulus: Es = 30 MPa                 
  • Poisson’s ratio: n = 0.25
  1. Based on the elastic theory (Boussinesq’s equation), calculate the change in vertical stress at point A long time after applying the surcharge load.
  2. Using the theory of 1-D consolidation, calculate the total settlement of this rigid footing due to consolidation of the clay layer only, long time after applying the total load.

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