8
Description
Where necessary, refer to the drawings in the
Equipment Diagrams
section.
Overview
After filling the sand tank with appropriate sand (not supplied) and filling the sump
tank with water the equipment provides a self contained facility for the study of flow
through permeable media. The sand tank has a toughened glass front and the
aluminium back permits the insertion of pressure tappings, tile drains etc.
Drainage and Seepage Tank
A metal frame supports the sand tank (1) above a sump tank (12) and centrifugal
pump (13). The frame has adjustable feet (10) to allow the glass fronted sand tank to
be levelled in both planes. The frame also includes a shelf (18) located in front of and
just below the bottom of the sand tank.
The sand tank is fabricated with an aluminium back panel (17) incorporating six
tapping points (6) and a front panel of toughened glass (19). The tappings in the rear
panel are fitted with sealing plugs that can be removed to incorporate a tile drain
(described in detail later) or used as tapping points, if required.
Two independently adjustable overflows (7 & 16) fitted through the floor, at each end
of the sand tank; allow different water levels to be maintained at each end of the
sand tank to suit different demonstrations. Water is returned to the sump tank by the
overflows. Each overflow incorporates a plug of open cell foam material to prevent
particles of sand from washing into the sump tank.
Two aluminium rails along the top edges of the sand tank provide location for an
adjustable clamp (5) for an impermeable baffle plate (4) or lateral pressure plate
(described later) when required. The rails also allow the position of the clamp (3) for
the water inlet (2) to the sand tank to be varied to suit different demonstrations.
A drain valve (8) in the floor of the sand tank allows water to be drained from the
sand tank after use. Care should be taken to ensure that no sand particles fall into
the sump tank when filling the glass fronted sand tank or making changes during
experiments.
The sump tank can be emptied using the sump tank drain (11).
An electrical switch (15) controls the operation of the pump and hence the supply of
water to the surface of the sand in the sand tank. The flow of water to the sand tank
can be varied using a flow control valve (14) at the pump outlet.
Permeable Medium (Sand)
The equipment supplied does not include the permeable medium (sand) required for
experimental studies. For the Teaching Exercises suggested it is advisable to use a
washed, narrow range sand (coarse sand) with no significant fraction finer than
0.5mm. Alternative sand can be used if required to suit specific requirements.
