of Earth Science |Northeastern
Objectives #11 (October 2,
the end of today's class, you
should be able to do the following:
Properties of Porous Materials
- Define the following terms, using appropriate units of
conductivity and permeability,
and explain the difference between them.
- Characterize rocks and sediments in terms of their
hydraulic conductivity and permeability,
giving typical ranges of values of these properties for each type of
rock and sediment.
- Define the terms aquifer and aquitard, giving
examples of rocks/sediments that might compose each.
- Explain what makes water flow.
- Define the term hydraulic gradient.
- Find total hydraulic head at any point in a system of tubes
and buckets (e.g. a siphon) and correctly predict which way flow will
proceed (if at all).
- Use Darcy's
Law by applying it to a permeameter system.
v Properties of Porous Materials:
- Define these properties of
materials: hydraulic conductivity
Explain the difference between them.
Write formulas to express
each quantity. Give a typical range of values for each property
in various rocks and sediments.
Hydraulic Head, Hydraulic Gradient, and
- Define the terms aquifer and aquitard.
the hydraulic head within a bucket of water. (Hint: you will need
to start by setting an arbitrary datum.)
- If two
buckets are connected by a tube (see
a simple worksheet here), find the total
hydraulic head at each end of the tube. What does this tell you
about direction of flow? What if the end of the tube is higher
than water level in the lower bucket? What happens if the
tube is made longer? Looped? Made shorter? Packed with sand?
- Given a
system of two water buckets with a tube between them (see the
worksheet here), say whether water will
flow from one bucket to the other (and if so, which way). Come up
with a general rule that tells whether water will flow or not and if
so, which way.
- Return to the system
of two buckets connected by a long tube, the tube packed with
sand. Find the hydraulic head at a point exactly halfway between
the two ends of the tube, and at points exactly one-fourth of the way
from each end. Then, consider a shorter tube packed with
sand, but starting and ending at the same places as the longer
one. Find the hydraulic head at the 1/4, 1/2, and 3/4
How is this system like/unlike the system with the longer tube?
Explain the term hydraulic
a way to combine hydraulic
conductivity, cross sectional area,
gradient to give the discharge of water flowing through a tube
packed with sand. Check to be sure the units of measurement work
out! Find a
statement of Darcy's
Law in your textbook, and tell how it compares with what you
- Draw a
sketch of your experimental set-up from last time (the
permeameter). Determine the hydraulic head at these two points:
as water entered the sediment sample, and as it exited the sediment
sample. Find the hydraulic gradient within the sample. How
could you have increased discharge (Q) through the sample by altering
your experimental set-up?
© 2007 Laura L.
Last updated October 2, 2007.