Question

A protective filter can also be called as __________

(a) Reverse filter and Inverted filter

(b) Horizontal filter

(c) None of the mentioned

(d) All of the mentioned

The question was asked in an interview.

Question is taken from Protective Filters topic in section Drainage and Dewatering of Geotechnical Engineering I

Answer 1

Correct answer is (a) Reverse filter and Inverted filter

For explanation I would say: In protective filter, each subsequent layer becomes increasingly coarser than the previous one, and hence, it is also called a reverse filter or inverted filter.