Question

A clay layer of thickness \(4\) m is sandwiched between two pervious layers. The maximum drainage path in the clay layer is

• A. \(2\) m
• B. \(4\) m
• C. \(1\) m
• D. \(0.4\) m

Hint:

Remember: Single drainage: \[ H_d=H \] Double drainage: \[ H_d=\frac{H}{2} \] A clay layer between two pervious layers always has double drainage.

Answer 1

The Correct Option is A

Concept: The maximum drainage path is the maximum distance that pore water must travel to escape from the soil layer during consolidation. For a clay layer, - If drainage occurs from both top and bottom (double drainage), \[ \boxed{H_d=\frac{H}{2}} \] - If drainage occurs from only one side (single drainage), \[ \boxed{H_d=H} \] where \[ H=\text{Thickness of clay layer}. \]

Step 1: Identify the drainage condition. The clay layer is sandwiched between two pervious layers. Hence, drainage takes place from both the top and bottom surfaces. Therefore, \[ \boxed{\text{Double drainage condition}.} \]

Step 2: Calculate the drainage path. Given, \[ H=4\text{ m} \] Using \[ H_d=\frac{H}{2}, \] we get \[ H_d=\frac{4}{2}=2\text{ m}. \] Hence, \[ \boxed{\text{Maximum drainage path}=2\text{ m}.} \] Therefore, the correct option is \[ \boxed{(A)\;2\text{ m}.} \]