---
title: "Factors affecting capillary rise"
subject: "Soil Mechanics"
chapter: 6
key: "semester_4/soil_mechanics:capillary-rise-factors"
source: https://www.bctengineer.com/q/semester_4/soil_mechanics/capillary-rise-factors
site: BCT Engineering
---

# Factors affecting capillary rise

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

- Asked in: 2073 Bhadra, 1 marks
- Video: [Capillary Rise in Soils](https://www.youtube.com/watch?v=AjQ7LWyUkRQ) — Elementary Engineering
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/soil_mechanics/capillary-rise-factors
- Whole chapter: https://www.bctengineer.com/md/semester_4/soil_mechanics/chapter-6

## Question

What are the factors that influence the height of capillary rise in soils?

## Short answer

Capillary rise depends on small pore size (inversely proportional to effective grain size D10 and void ratio), surface tension of water, and contact angle. Finer soils, lower void ratios, and high surface tension give greater rise.

## Answer

Capillary rise $h_c = \dfrac{4T\cos\alpha}{\gamma_w d}$ depends on:

1. **Grain/pore size:** smaller effective diameter $D_{10}$ and void size gives greater rise ($h_c \propto 1/d$; $h_c \approx C/(eD_{10})$).
2. **Void ratio:** smaller $e$ gives higher rise.
3. **Surface tension of water** (and temperature, impurities).
4. **Contact angle** between water and particle surface.
5. **Soil type and packing,** clean surfaces and degree of saturation of the soil.

## Check yourself

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

1. Capillary rise h_c is:
   A. Proportional to the pore diameter
   B. Independent of grain size
   C. Greater in coarser soil
   D. Inversely proportional to the pore diameter, so larger in fine soil
   Answer: D. h_c = 4T cos(alpha)/(gamma_w d), so smaller d gives higher rise. (Key point: Effect of grain size)

2. A smaller void ratio e gives:
   A. Higher capillary rise
   B. Lower capillary rise
   C. No change
   D. Zero capillary rise
   Answer: A. h_c is approximately C/(e D10), so smaller e gives greater rise. (Key point: Effect of void ratio)

3. Which also influences capillary rise?
   A. Colour of soil
   B. Surface tension and contact angle
   C. Depth of the foundation
   D. Cohesion of the soil
   Answer: B. Surface tension T and contact angle alpha appear directly in the formula. (Key point: Other factors)

## Related in Soil Mechanics

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- [Factors affecting degree of consolidation](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Afactors-affecting-degree-consolidation) — Soil Mechanics, chapter 9

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