Coefficient of Consolidation calculation

Problem: A 3m layer double drainage of saturated clay under surcharge loading underwent 90% consolidation in 75 days. Find the coefficient of consolidation?
Exam Name: PGCL 2017


Solution:
We know,
            T_v= C_vt /  H_dr²

      Here,  T_v= 0.848 (for 90% consolidation)
                   t = 75 days
               H_dr = (3/2) m (for double drainage)
                C_v = ?

                 C_v= 0.848* (3/2)2/ 75
                      = 0.025 m²/day
                      = 2.894 * 10^-7 m²/s
Answer: 2.894 * 10^-7 m²/s

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