Concept

The constant head permeability test is a common laboratory testing method used to determine the permeability of granular soils like sands and gravels containing little or no silt. This testing method is made for testing reconstituted or disturbed granular soil samples.

Description and Procedure

The constant head permeability test involves flow of water through a column of cylindrical soil sample under the constant pressure difference. The test is carried out in the permeability cell, or permeameter, which can vary in size depending on the grain size of the tested material. The soil sample has a cylindrical form with its diameter being large enough in order to be representative of the tested soil. As a rule of thumb, the ratio of the cell diameter to the largest grain size diameter should be higher than 12 (Head 1982). The usual size of the cell often used for testing common sands is 75 mm diamater and 260 mm height between perforated plates. The testing apparatus is equipped with a adjustable constant head reservoir and an outlet reservoir which allows maintaining a constant head during the test. Water used for testing is de-aired water at constant temperature. The permeability cell is also equipped with a loading piston that can be used to apply constant axial stress to the sample during the test. Before starting the flow measurements, however, the soil sample is saturated. During the test, the amount of water flowing through the soil column is measured for given time intervals.

Knowing the height of the soil sample column L, the sample cross section A, and the constant pressure difference Δh, the volume of passing water Q, and the time interval ΔT, one can calculate the permeability of the sample as

K=QL / (A.Δh.Δt)

Standards

• ASTM D7625-10: Standard Test Method for Laboratory Determination of Abrasiveness of Rock Using the CERCHAR Method Link
• NF P94-430-1: Roches - Détermination du pouvoir abrasif d'une roche - Partie 1 : essai de rayure avec une pointe
• ISRM Suggested Method for Determining the Abrasivity of Rock by the CERCHAR Abrasivity Test Link

References - External Links

1. Head, K. H., 1982, Manual of soil laboratory testing, Vol 2, Pentech Press, ISBN 0-7273-1305-3

• General description of the permeability tests MADHIRA R. MADHAV, Indian Institute of Technology
• Determination of coefficient of permeability of sand by constant head method Dr Anand J Puppala, Lecture notes, SOIL MECHANICS LABORATORY, THE UNIVERSITY OF TEXAS AT ARLINGTON
• Constant head permeability test method, DEPARTMENT OF TRANSPORTATION, STATE OF CALIFORNIA— BUSINESS, TRANSPORTATION AND HOUSING AGENCY
• A powerpoint presentation of the constant head permeability test, Soil mechanics, Civil, architectural, & Environmental Engineering Department, Drexel University
• Constant head and falling head permeability tests, Binod Tiwari, Soil Mechanics Laboratory, California State University, Fullerton
• Illustrated description of constant head permeability tests, Prof. Krishna Reddy, Engineering Properties of Soils Based on Laboratory Testing, UIC