Question

Given below are the two statements.
Statement I: In case of any kind of water harvesting embankment is constructed across the flow in a river or channel; creep theory states that piping will always occur along the line of creep inside the foundation of the structure
Statement II: Weighted creep ratio is an indicator to decide or design creep length, and it remains a ratio of weighted creep distance and the associated head
In light of the above statements, choose the most appropriate answer from the options given below

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is correct but Statement II is false
• D. Statement I is incorrect but Statement II is true

Hint:

Lane's Weighted Creep Theory gives vertical creep 3 times more weightage than horizontal creep ($L_w = N_v + \frac{1}{3} N_h$).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Bligh's and Lane's creep theories analyze seepage paths along the contact profile between hydraulic foundations and subsoil.
Key Formula or Approach:
\[ C_w = \frac{L_w}{H} = \frac{\sum d_v + \frac{1}{3}\sum L_h}{H} \quad \text{(Lane's Weighted Creep Ratio)} \]

Step 2: Detailed Explanation:
1. Statement I: According to Bligh's and Lane's classical seepage theories, percolating water creeps along the contact surface between the foundation base and the permeable soil. If the total path of creep is insufficient for the hydraulic head, piping erosion initiates along this line of contact. Hence, Statement I is true.
2. Statement II: Lane's Weighted Creep Ratio ($C_w$) is the ratio of total weighted creep length ($L_w = \text{Vertical paths} + \frac{1}{3}\text{Horizontal paths}$) to the total effective head ($H$). It is the primary engineering design criterion for safe impervious apron length. Hence, Statement II is true.

Step 3: Final Answer:
Therefore, Both Statement I and Statement II are true, corresponding to option (A).