What is the groundwater table, and how is its position determined? Relate the groundwater table to the pressure in the water

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What is the groundwater table, and how is its position determined? Relate the groundwater
table to the pressure in the water. Explain what the phreatic zone is and what it has to do
with the groundwater table?
6-A-2 Explain the difference between a soil stratum that is an aquifer and one that is an aquiclude.
What, then is an aquitard? Also, what types of soils are expected to form an aquifer? an
aquiclude? an aquitard? And what would be the expected range for the coefficient of
permeability in aquifers, in aquicludes, and in aquitards.
6-A-3 Make drawings that show the sequence of soil layering that occurs in the ground to form:
A. Unconfined aquifer; B. Confined aquifer; C. Perched water table.
In which of these three aquifers would artesian condition most likely develop?
and how would such artesian conditions develop?
6-A-4 What is the vadose zone in an area's subsurface region? Describe each of the three
sub-strata of the vadose zone relative to the presence of water in soil pores, and relative
position below ground surface. Which part of the vadose zone is saturated? How?
6-A-5 Explain how capillarity works to cause saturated conditions to be present above the
groundwater table.
6-A-6 Write the Bernoulli Equation, as it is most commonly used in analyzing the flow of water
through the ground, and explain what each of the parts of the equation are and how they are
measured. Also, explain what part of Bernoulli's equation is not used in geotechnical study
of groundwater, and why it is not used.
6-A-7 For water to flow through the ground, there must be a force or energy. Explain what the
"force" is that makes water flow through the ground, and how Bernoulli's equation is used to
assess the magnitude of force that is acting to move water.
6-A-8 Explain what is "hydraulic gradient" as it relates to the movement of water through the
ground, and how it is quantified. Write the equation used to calculate "hydraulic gradient".
6-A-9 Describe the two different types of geotechnical instrumentation that are used to measure
groundwater levels, and explain what it is that each measures, how that measurement is used
to determine the groundwater level. Also explain in what types of soils each of these different
instruments should be used.CIVE 3300 - Soil Mechanics - Home Problems Set 6-A, Groundwater Fundamentals, Page 2 of 2
6-A-10 In a silt soil, the D10 size is 0.01mm. If the effective pore size for estimating capillary rise is
taken as 1/5 of D10, approximately what height of capillary rise will occur?
6-A-11 Explain what is the consequence of capillarity in silts soils that are the subgrade soils below
road pavements in cold New England winters. Also, describe what happens when the ground
thaws in the spring that affects the performance of road pavements.
6-A-12 Explain what the permeability (or hydraulic conductivity) of soil is. What units are most
commonly used? Does the permeability represent the average rate of flow or the actual?
6-A-13 The coefficient of permeability is generally greater for coarse soils (sands and gravels) than
for fine-graded soils (silts and clays). What effect does particle size have on permeability?
Explain why this effect occurs.
6-A-14 The void ratio for clay soils commonly is greater than the void ratio for the coarse-grained
soils, but the coefficient for permeability of clay soil is much slower.
Explain why this seemingly contradictory behavior occurs.
6-A-15 A constant head permeability test passes water through a soil mass that has a sample
length of 150 mm and cross section that is square and is 20 mm by 20 mm. A constant head
of 2 ft. is maintained throughout the test. The khyd value of the soil is 0.1 mm/sec.
Make a sketch to show the test set-up.
Now calculate the amount of water that will flow through the soil sample in 5 minutes,
expressing the answer in liters of water.
6-A-16 Explain why the actual velocity of groundwater movement through the soil voids will be
much faster than the average rate of flow which is predicted using Darcy's equation.
What calculation is used to determine a value for the 'actual' groundwater flow velocity?
6-A-17 A falling head test is performed in the laboratory to determine the coefficient of
permeability for a fine-grained soil.
Use the following data to determine k, and then indicate the probable soil classification.
- length of soil sample = 150 mm
- cross-sectional area of sample = 1,140 sq. mm
- cross sectional area of standpipe = 200 sq.mm
- at the start of the test, the water level in the supply standpipe is 1m above
the top of the permeameter.
- one hour after start, the water level in the supply standpipe
is 0.95m above the top of the permeamete