---
title: "Coefficient of transmissibility"
subject: "Soil Mechanics"
chapter: 6
key: "semester_4/soil_mechanics:transmissibility-define"
source: https://www.bctengineer.com/q/semester_4/soil_mechanics/transmissibility-define
site: BCT Engineering
---

# Coefficient of transmissibility

Soil Mechanics · Chapter 6: Principle of Effective Stress, Capillarity and Permeability

- Asked in: 2078 Chaitra, 1 marks
- Video: [Hydraulic Conductivity and Transmissivity](https://www.youtube.com/watch?v=WA7G5Yoe2fM) — Dane Andersen
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/soil_mechanics/transmissibility-define
- Whole chapter: https://www.bctengineer.com/md/semester_4/soil_mechanics/chapter-6

## Question

Define coefficient of transmissibility.

## Short answer

Coefficient of transmissibility T is the discharge through a vertical strip of aquifer of unit width and full saturated thickness under a unit hydraulic gradient, equal to k times the aquifer thickness b, with units m2/s or m2/day.

## Answer

**Coefficient of transmissibility** $T$ is the rate of flow of water through a vertical strip of aquifer of unit width and full saturated thickness $b$ under a unit hydraulic gradient. It equals the coefficient of permeability times the aquifer thickness:

$$
T = k\,b
$$

Its unit is m²/day or m²/s.

## Check yourself

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

1. The coefficient of transmissibility is the flow through:
   A. A unit area of aquifer under unit head
   B. A vertical strip of aquifer of unit width and full saturated thickness under unit hydraulic gradient
   C. A well of unit radius under unit drawdown
   D. A horizontal layer of unit thickness under unit pressure
   Answer: B. T is the flow per unit width over the full saturated thickness b at unit gradient. (Key point: Definition)

2. Transmissibility T is related to permeability k and aquifer thickness b by:
   A. T = k/b
   B. T = k b^2
   C. T = k b
   D. T = b/k
   Answer: C. T = k b. (Key point: Formula)

3. The unit of transmissibility is:
   A. m/s
   B. m^2/s
   C. m^3/s
   D. m/s^2
   Answer: B. k (m/s) times b (m) gives m^2/s (or m^2/day). (Key point: Unit)