A normally consolidated clay layer in the field has a thickness of 3.2 m with an average effective stress of 70 kN/m². A laboratory consolidation test on the clay gave the following results.

  

      

  

a. Determine the compression index, C_c.

  

b. If the average effective stress on the clay layer  is increased to 115 kN/m², what would be the total consolidation settlement?

  

      

Pressure (kN/m) 100 200 Void ratio 0.905 0.815