Question:

If the coefficient of permeability is doubled and the coefficient of volume compressibility is simultaneously halved, the coefficient of consolidation

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Remember the consolidation relation: \[ \boxed{ C_v=\frac{k}{m_v\gamma_w} } \] Thus, \[ C_v\propto\frac{k}{m_v}. \] If \(k\) doubles and \(m_v\) becomes half, \[ C_v=4\times\text{original value}. \]
Updated On: Jul 23, 2026
  • Increase by \(2\) times
  • Decrease by \(2\) times
  • Increase by \(4\) times
  • Decrease by \(4\) times
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The Correct Option is C

Solution and Explanation

Concept: The coefficient of consolidation is given by \[ \boxed{ C_v=\frac{k}{m_v\gamma_w} } \] where \[ k=\text{Coefficient of permeability}, \] \[ m_v=\text{Coefficient of volume compressibility}, \] and \[ \gamma_w=\text{Unit weight of water}. \] Thus, \[ C_v\propto\frac{k}{m_v}. \]

Step 1:
Write the proportional relationship. Initially, \[ C_v\propto\frac{k}{m_v}. \] After the changes, \[ k'=2k, \] and \[ m_v'=\frac{m_v}{2}. \]

Step 2:
Calculate the new coefficient of consolidation. \[ C_v' = \frac{2k}{m_v/2} = \frac{2k\times2}{m_v} = 4\frac{k}{m_v} = 4C_v. \] Therefore, \[ \boxed{C_v'=4C_v.} \] Hence, the coefficient of consolidation increases four times. Therefore, the correct option is \[ \boxed{(C)\;\text{Increase by 4 times}.} \]
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