PERMEABILITY TEST

Constant Head Apparatus

BS 1377; EN 1997-2; ASTM D2434; AASHTO T215

This equipment is used for testing the permeability of

granular soils (sands and gravels).The specimen is

formed in a permeability cell and water is passed through

it from a constant level tank. Take-off points located

along the sides of the permeability cell are connected to

three manometer tubes mounted on a panel complete

with a metre scale. Water passing through the specimen

is collected and measured, either for a specific quantity

or over a period of time. The reduction of head is noted

from the variation of water level in the manometer tubes.

Falling Head Apparatus

Clays and silts are tested using the falling head

technique. Flow of water through the specimen is

observed by monitoring the rate of fall of water in the

tube. It is essential that soils of very low permeability are

sealed inside the cylinder to prevent seepage along the

sides of the specimen. Before testing, the specimen must be completely saturated with water as the presence of air will restrict the flow of water.