---
title: "Define permeability"
subject: "Engineering Geology I"
chapter: 6
key: "semester_3/engineering_geology_i:define-permeability"
source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/define-permeability
site: BCT Engineering
---

# Define permeability

Engineering Geology I · Chapter 6: Physical Geology

- Asked in: 2061 Baisakh (old course), 1 marks
- Video: [Porosity and Permeability](https://www.youtube.com/watch?v=8mfBomrw0rs) — GeoScience Videos
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/engineering_geology_i/define-permeability
- Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-6

## Question

Define permeability.

## Short answer

Permeability is the ability of a rock or soil to transmit fluid through interconnected voids and fractures. It is quantified by the coefficient of permeability k (or hydraulic conductivity K, in m/s). Coarse materials (gravel, sand) are highly permeable; clays and intact granite are impermeable.

## Answer

**Permeability** is the property of a rock or soil by which it allows fluid (water) to pass through its interconnected pores, fractures and voids. Its measure is the coefficient of permeability $k$ (or hydraulic conductivity $K$, in m/s). Gravel and clean sand are highly permeable; clay and unfractured granite are practically impermeable.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Permeability is:
   A. Ratio of void volume to total volume
   B. Strength against sliding
   C. Ability to resist weathering
   D. The property of a material to let fluid pass through its interconnected pores and fractures
   Answer: D. That ratio is porosity. (Key point: Definition)

2. Which material is highly permeable?
   A. Gravel and clean sand
   B. Clay
   C. Unfractured granite
   D. Shale
   Answer: A. Clay and unfractured granite are practically impermeable. (Key point: Highly permeable)

3. Permeability is measured by:
   A. Angle of friction
   B. Coefficient of permeability k (hydraulic conductivity K in m/s)
   C. Porosity percentage
   D. Unconfined strength
   Answer: B. k or K quantifies how readily water flows. (Key point: Measure)