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Permeability test

General

The rate at which water flows through a soil is proportional to the hydraulic gradient and is expressed by Darcy's Law as:

Equation Set 1.1: Darcy's Law

The coefficient of permeability varies with the type of soil and conditions.  It is influenced by:

  1. Size and shape of the soil particles
  2. Void ratio
  3. Temperature
  4. Degree of saturation

Empirical methods to estimate permeability using Hazen equations:

Equation Set 1.2: Hazen equations

for sands:

for estimating flow through graded sand filters (clean sands and gravels):

Several different laboratory testing methods can be performed to more accurately determine permeability, including constant-head and falling-head types.   For our purposes, a falling-head test will be performed.  The falling-head test essentially consists of measuring change in head and quantity of flow over time as follows:

Equation set 1.3: Falling head test

 

Apparatus

 

Permeameter (1/30 cf volume) apparatus
Burette stand
Meter stick
#4 sieve
Stopwatch
Pan
Tamper
 

Procedure

 

 

Procedure and data sheets [right-click | "save target as" Excel Office 2000 ]

References

Al-Khafaji & Andersland (1992), pages 472-481.

Lambe (1951), 29 - 42.