Shallow Foundations MCQ with answer and solution

Concept

IS 456:2000 sets a minimum edge thickness for RCC footings: 150 mm on soil and 300 mm above pile tops on piles.

Step-by-step solution

1. Recall IS 456:2000, Cl. 34.1.2 (Footings – thickness at edge). 2. For footings on soils, the edge thickness shall not be less than 150 mm. 3. For footings on piles, it shall not be less than 300 mm above the top of the piles. 4. So the answer is 150 mm, option (C).

Explanation

IS 456:2000 says the edge of an RCC footing on soil must be at least 150 mm thick. This gives enough depth for cover, bars and anchorage. For footings on piles the limit is higher, 300 mm above the pile tops.

Why the other options are wrong

A: 100 mm is less than the code minimum. B: 200 mm is not the code value for footings on soil. D: 50 mm is too thin and is only near a cover value.

Shortcut

Footing edge: Soil = 150 mm, Pile = 300 mm (double).

Common mistake

Mixing up the 150 mm (on soil) limit with the 300 mm (on piles) limit.