# Civil Engineering - UPSC Civil Service Exam Questions - Discussion

Discussion Forum : UPSC Civil Service Exam Questions - Section 3 (Q.No. 3)
3.
To make certain that the backfill material is more pervious than the soil to be drained, the relationship used in
(D15)Filter ≤ 5 (D85)Protected soil
(D15)Filter ≥ 5 (D85)Protected soil
(D15)Filter ≥ 5 (D15)Protected soil
(D15)Filter ≤ 5 (D15)Protected soil
Explanation:
No answer description is available. Let's discuss.
Discussion:
9 comments Page 1 of 1.

Yasir said:   3 years ago

Priyanka said:   3 years ago

Amit Singh said:   3 years ago
(D15)filter/(D85)soil<5.
4<((D15)filter/(D15)soil)<20.
(D50)filter/(D50)soil<25.

Hence, option D is correct.

A Ali said:   4 years ago
C should be the right answer.

Akash said:   5 years ago
(D15)Filter ≥5 (D15)Protected soil. So, C is correct.

Dolly said:   6 years ago
According to me, C is the correct option.

Priya said:   6 years ago
Yes, it's C. I also agree.

Lara said:   7 years ago
Which is the correct answer C or D? can you explain for me?

Karan said:   7 years ago
Correct Ans is C.

Explanation : For the filter to provide full drainage.
k of filter >= 25k of protected soil.
Where k is permeability and proportional to square of particle size. So,
d15 of filter >= 5 d15 of protected soil.