Humboldt H-4146 Compaction Permeameters - Manual (Page 3)

General
The H-4145 and H-4146 Permeameters are designed for performing either
constant head or falling head permeability tests on undisturbed, remolded or
compaction soils. The units consist of a standard compaction mold and collar,
mounting base with porous stone and brass pipe fitting and head with air
escape valve and fitting.
Sample Preparation
For tests on cohesionless soils, such as sands and gravels the soils are placed
in to the mold by a spoon or any other desired method. To avoid entrapped
air it is advisable to raise the water level in the cylinder as the soil is placed,
maintaining about one inch of free water above the surface of the sample. If the
sample contains fines, care must be exercised to avoid segregation. After the
material has been placed and is at the proper voids ratio the collar is removed
an the test head and gasket are set in position and tightened.
For tests on remolded, compacted soils such as silts and clays, the cylinder and
the collar are mounted on a compaction test base and the sample is compacted
as per Standard Proctor Method or other method applicable to the desired
test results. With the specimen properly compacted, the collar should be
removed and the upper surface of the soil squared with the end of the cylinder.
The cylinder and soil are then placed on the permeameter base and the head
fastened in place. Care must be taken to keep air out of the system at all stages
of preparation for the test.
For tests on undisturbed soil samples, the specimen is trimmed to fit the
cylinder without air space between soil and the wall. If this is impossible, the
sides of the sample should be sealed with paraffin and the sample fitted to the
cylinder. The cylinder is then placed on the permeameter base and the head
fastened in place.
For tests on rock samples (rock cores), the sides are coated with paraffin in
order to fit tightly in the cylinder. With this completed the cylinder is placed on
the permeameter base and the head fastened in place.
Test Instructions
Constant Head Test—This test is generally used for determining permeability
of materials, such as sands, gravels, etc. A constant head supply can adjusted
to give the desired hydraulic gradient. This discharge can be conveniently
collected in a 100cc graduate. A stop watch is required for timing the discharge
period.
Falling Head Test—For soils with low permeability, the falling head test is most
applicable. The drain at the base is connected to a tank, which will give the tail
water elevation. The falling source is connected to the pipe fitting at the head