Geotechnical Engineering

DHARM

42 GEOTECHNICAL ENGINEERING

Handle

Hole

Cylinder

Cover plate

of shutter

Shutter

Cone

100 mm

100 mm

125 or

150 mm

(a) Sand-pouring cylinder (b) Calibrating container
Fig. 3.7 Sand pouring cylinder
The procedure consists of calibration of the cylinder and later, the measurement of the
unit weight of the soil.
(a) Calibration of the Cylinder and Sand: This consists in obtaining the weight of sand
required to fill the pouring cone of the cylinder and the bulk unit weight of the sand. Uni-
formly graded, dry, clean sand is used. The cylinder is filled with sand almost to be top and the
weight of the cylinder with the sand is taken (W 1 ).

The sand is run out of the cylinder into the conical portion by pulling out the shutter.

When no further sand runs out, the shutter is closed. The weight of the cylinder with the

remaining sand is found (W 2 ). The weight of the sand collected in the conical portion may also

be found separately for a check (Wc), which should be equal to (W 1 – W 2 ).

The cylinder is placed centrally above the calibrating container such that the bottom of

the conical portion coincides with the top of the container. There sand is allowed to run into

the container as well as the conical portion until both are filled, as indicated by the fact that no

further sand runs out; then the shutter is closed. The weight of the cylinder with the remain-

ing sand is found (W 3 ). The weight of the sand filling the calibrating container (Wcc) may be

found by deducting the weight of sand filling the conical portion (Wc) from the weight of sand

filling this and the container (W 2 – W 3 ). Since the volume of the cylindrical calibrating con-

tainer (Vcc) is known precisely from its dimensions, the unit weight of the sand may be ob-

tained by dividing the weight Wcc, by the volume Vcc. (Wcc may also be found directly by strik-

ing-off the sand level with the top of the container and weighting it).

The observations and calculations relating to this calibration part of the work will be as

follows:

Initial weight of cylinder + sand = W 1

Weight of cylinder + said, after running sand into the conical portion = W 2

∴ Weight of sand occupying conical portion, Wc = (W 1 – W 2 )

Weight of cylinder + sand, after running sand into the conical portion and calibrating

container = W 3

∴ Weight of sand occupying conical portion and calibrating container = (W 2 – W 3 )