Question

What type of filter is provided at the bottom of drainage sumps and trenches?

(a) Drainage filter

(b) Reverse filter

(c) Weighting filter

(d) Horizontal filter

This question was posed to me during an online interview.

The question is from Protective Filters in chapter Drainage and Dewatering of Geotechnical Engineering I

Answer 1

The correct option is (c) Weighting filter

The best I can explain: Weighting filters at the bottom of drainage sumps and trenches arrest the percolating water at the exit and allow its safe exit without inducing piping.