Geotechnical engineering i For Civil Engineering Students

1. Shree Swami Atmanand Saraswati Institute of
Technology
Prepared By:-
Korat Harshad 120763106022
Mehta Moxesh 120763106024
Dhameliya Dhaval 120763106025
Vaghani Shaunak 120763106026
Seminar on
Methods of in site Permeability Test
Guided By:-
__________________1

2. Content
• Introduction
• Pumping Test
• Percolation Test
• Single Ring Falling Head Infiltrometer Test
• Double Ring Infiltrometer Test
• Slug tests
• Hazen Method
• Guelph Permeameter
2

3. Introduction
• What is Permeability….?
• Permeability is a property of soil which allows a water or any fluid to pass
through it…
• Methods of determination of permeability in field is shown in fig.
3

4. Pumping test
• The purpose of pumping test is to get the information of permeability;
• Pumping test is the active way to get k, the permeability. The passive way
is to do the percolation test.
• The principle of a pumping test is that if we pump water from a well
and measure the discharge of the well and the drawdown in the well and in
piezometers at known distances from the well, we can substitute these
measurements into an appropriate well-flow equation and can calculate
the hydraulic characteristics of the aquifer
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5. • The well will consist of an open-ended pipe, perforated or fitted with a screen in the
aquifer to allow water to enter the pipe, and equipped with a pump to lift the water to the
surface
• A pumping test does not require expensive large-diameter wells. If a suction pump
placed on the ground surface is used, as in shallow watertable areas, the diameter of the
well can be small. A submersible pump requires a well diameter large enough to
accommodate the pump.
• The well should be drilled to the bottom of the aquifer, if possible, because this has
various advantages, one of which is that it allows a longer well screen to be placed, which
will result in a higher well yield.
• The well should be developed by being pumped at a low discharge rate. When the
initially cloudy water becomes clear, the discharge rate should be increased and pumping
continued until the water clears again. This procedure should be repeated until the
desired discharge rate for the test is reached
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6. 6

7. 7

8. • After the pump reaches a steady state ( the water table drawdown does not
change with respect to time), for a given amount of time T, the amount of
water has been pumped out is Q, in the unit of volume, like cubic meter.
where k is permeability
H is the head
q is the flow rate, and
h1 & h2 is head
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9. Percolation Test
• Percolation test is a passive and cheap way to estimate soil permeability.
• Need more than 6 holes, after test do the average;
• Each hole to certain depth, usually 3’-5’
• Put 2” thick of coarse sand or gravel into the hole;
• Fill 12” water above the sand/gravel
• Stay overnight
• In the next day before testing filling water by 6”above the sand/gravel
• Measure the water level drop at 30 minutes interval for 4 hours. Every time, if
needed, add 6” of water again
• The drop occurred at the final 30 min. is used to determine the percolation rate
• If the soil is highly permeable, use 10 min. for the duration of 1 hour
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10. in situ hydraulic conductivity tests for compacted clay soils adapt similar
approach as showed in the above percolation test. It is dry and straight
forward, you can easily read through it.
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11. 11

12. Slug tests
• The aquifer tests that we have discussed so far involve pumping and have
some practical problems. They are expensive, requiring monitoring wells
and many person-hours of labor to conduct
• An alternative to a pump test is a slug test (also called a baildown test). In
this test the water level in a small diameter well is quickly raised or lowered.
The rate at which the water in the well falls (as it drains back into the
aquifer) or rises (as it drains from the aquifer into the well) is measured and
these data are analyzed.
• Water can be poured into the well or bailed out of the well to raise or lower
the water level. However, perhaps the easiest way to raise the water level in
the well is to displace some of the water in the well by lowering into it a
solid piece of pipe called a slug, So that’s where the name comes Slug Test
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13. • Procedure
In this slug test, water level is raised in a well, and the level of
the water in the well is measured over time as the water drains back
into the aquifer and the level falls.
A plot is made on
semi-log graph paper,
with the ratio of the
measured head to the
head after injection
(H / H0) plotted on
the Y (linear ) axis
and time plotted on
the X (logarithmic)
axis.
13

14. • The ratio of H/H0 is equal to a defined function:
H / H0 = F(η,µ)
Where...
• Values of F have been tabulated for different µ (mu) and η (eta). To
analyze the slug test data we need to match the data curve to one of a series
of type curves.
• Each type curve consists of H/H0 values plotted against a range of η values
for a particular value of µ.
• In this case, we need to keep the Y axis of the two graphs the same, while
sliding the overlay along until the data points are matched by one of the
curves.
• The matched curve gives us an approximate value for mu, while reading
the time value from the data graph that is equivalent to eta = 1, gives us a t1
value.
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15. • We can solve the following equations and find permeability
(K):
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16. Single Ring Falling Head Infiltrometer Test
• Principles:
Known boundary and pressure
conditions are used to determine the
unrestricted 3-dimensional infiltration
capacity, of a soil confined below the single,
steel ring. The ability for the soil to transmit
water (be permeable) is hence determined
through steady state calculations and, this
Saturated Hydraulic Conductivity (Ksat),
which is universally used as an empirical
constant to quantify specific, soil-water flow
and infiltration capacity problems. Ksat “is
one of the most important factors playing a
role in many agronomic, engineering and
environmental activities” (Herman et al, 2003)
and hence, is a useful term to quantify.
Single ring Infiltrometer ; in action
Single ring Infiltrometer; finished
16

17. Methods:
A single steel ring with dimensions (20cm
diameter and 17cm tall) is inserted 2cm into
the soil surface.
It is with 2L of fresh water by sealing with a
plastic sheet, pouring the water over the
plastic and pulling the plastic slowly.
The initial height is measured once all the
water is released and time initiated.
Further water level (height) measurements
are taken at 15-second intervals for the first
few minutes and, after 2 minutes another 15
seconds is added to the interval period
(subject to intensity of infiltration; figure 2).
This process is continued until all the water
has infiltrated or a steady state rate is
recognisable.
The single ring infiltrometer was used at all
10 sites within the study area and at the soil
pit.
Filling ring with water and taking initial
measurement
Method for
taking
continuous
height
measurements17

18. Analysis
output for analysis of C1, linear equation sited
(note the exclusion of points not in a steady
state of infiltration, the red line represent the
steady state function)
For each individual site, the x,y distribution of
time against cumulative infiltration is displayed,
so that the point steady state infiltration can be
visually determined.
A line is then fitted along the steady state
portion of the graph. Within the resulting linear
equation, the gradient is equated as the soil-
water flux (q).
Using q = Ksat.{(C/G.pi.r)+1}
Ksat (mm/h) of the soil can be
determined as all other components are known
or estimated.
q = statistically determined (cm/min)
C = wetting front potetenial (estimated
for clays at 150 cm)
G = shape factor for infiltration
(0.8456)
pi = 3.1415...
r = radius of ring (10cm)
18

19. Double Ring Infiltrometer Test
Principle of how it works:
The double ring Infiltrometer is a way of measuring saturated hydraulic
conductivity of the surface layer.
It consists of an inner and outer ring inserted into the ground. Each ring is
supplied with a constant head of water either manually or from mariotte bottles.
Hydraulic conductivity can be estimated for the soil when the water flow rate in
the inner ring is at a steady state.
It works by directing water onto a known surface area due to the parameters of
the inner ring.
The rate of infiltration is determined by the amount of water that infiltrates into
the soils per surface area, per unit of time.
Infiltration can be measured by either a single or double ring infiltrometer, with
preference usually lying with the double ring because the outer ring helps in
reducing the error that may result from lateral flow in the soil.

20. The outer ring virtually turns a 3D single ringed
system of looking at infiltration into a one
dimensional model by allowing water in the
center ring to flow nearly exclusively straight
down. This allows much easier calculation by
taking out the need to account for lateral flow.
This schematic diagram shows the vertical flow
that is generated form the inner ring which is
allowed by the outer ring accounting for all the
lateral flow.
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21. Description of apparatus/method:
• Before the double rings can be placed in position the ground cover must be removed
without disturbing the soil surface.
• The rings can be set in position and knocked into the ground about 10cm, or until the
rings are set firmly in the ground.
• When filling up the rings the outer ring is filled first so that the soil profile around the
inner ring would be wet and only vertical flow would occur when the inner ring is
filled later.
• Apply the water to the centre ring, then finally measuring infiltration at certain time
intervals.
• When filling the inner ring water is poured in on a plastic sheet, then once the desired
amount of water is in the ring on the sheet, the sheet is removed quickly. The level of
the water is recorded at this point as the start of infiltration.
• Water can be supplied inside the rings either by a marriotte bottle assembly, to keep a
constant head or manually.

22. 22

23. Analysis of Data:
Data is gained by a drop in water height, giving an infiltration of water over
time. These data points are plotted in a graph of infiltration versus time.
Theoretically, once the soil becomes saturated, a steady state infiltration rate will
be reached, which is seen on a graph as a section of data points infiltrating
showing linearity.
Once this linear section is identified other outlying data points can be excluded
from the analysis and a line of best fit can be fitted to the applicable data. The
gradient of this fitted line gives the steady state infiltration rate for that
particular soil. The steady state infiltration rate can then be multiplied 1.45, to
obtain the hydraulic conductivity (Ksat), of that soil. This is a measure of how
conductive a soil is at saturation, which is a measure of permeability.

24. Problems with method:
Some draw-backs of the double ring are that
1- It is very time consuming,
2- Requiring frequent attention, either by recording measurements or by
maintaining equilibrium in the height between the rings.
3- The practicality of the instrument is reduced by the fact the rings are
extremely heavy to move.
4- It also requires a flat undisturbed surface which sometimes is not available.
5- The infiltration rate varies with different soil types, which can effect the
accuracy of the results.
6- The soil type that the above results were obtained from is a Vertosol. These
soils are known for their shrink/swell properties, which result in cracks when
dried and can lead to misleading results. The double ring method is not reliable
on soils with vitric properties. (McKenzie et al., 2002).

25. Estimated Methods- Based on Grain Size
Hazen Method:-
Applicability: sandy sediments
• K = C*d10
2
• d10 is the grain diameter for which
10% of distribution is finer,
"effective grain size" - where D10
is between 0.1 and 0.3 cm
• C is a factor that depends on grain
size and sorting
Very Fine
Sand, poorly
Sorted
40 - 80
Fine Sand with
fines
40 - 80
Medium Sand,
Well Sorted
80 - 120
Coarse Sand,
Poorly Sorted
80 - 120
Coarse sand,
well
Sorted, clean
120 - 150
C- Factor
25

26. Guelph and Amoozegar
Borehole Permeameter
Field Testing 26

27. • The Guelph Permeameter is an easy to use
instrument for quickly and accurately measuring
in-situ hydraulic conductivity. Accurate
evaluation of soil hydraulic conductivity, soil
sorptivity, and matrix flux potential can be made
in all types of soil. The equipment can be
transported, assembled, and operated easily by
one person. Measurements can be made in 1/2 to
2 hours, depending on soil type, and require
only about 2.5 liters of water.
• Measurements can be made in the range of 15 to
75 cm below the soil surface. The Guelph
Permeameter is a complete kit consisting of the
Permeameter, field tripod, well auger, well
preparation and cleanup tools, collapsible water
container, and vacuum test hand pump, all
packaged in a durable carrying case.
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28. 28

29. • The Guelph Permeameter (GP) is a constant-head device,
which operates on the Mariotte siphon principle and provides a
quick and simple method for simultaneously determining field
saturated hydraulic conductivity, matric flux potential, the α*
parameter and soil sorptivity in the field.
• Using the Guelph Permeameter, measurements in high and
moderately permeable soils can usually be made and results
calculated in less than an hour
• The implements needed for excavating and preparing a well
borehole are included in the Guelph Permeameter Kit.
29

30. • Auger Cutting Diameter - 6.0 cm (2-3/8”)
• Well Height Range - 2.5 cm to 25 cm
• Hydraulic Conductivity Range – 0.0001 to 0.0000001 m/sec
0.01 to 0.00001 cm/sec
• Collapsible Water container Capacity - 11.36 liters (3.0
gallons)
• Maximum Permeameter Capacity - 3.18 liters (.84 gallons)
• Overall Carrying Case Size - 132.08 cm (50”) long x 44.45
cm (17.5”) wide x 15.24 cm (6”) deep
• Overall Carrying Case Weight - 11 kg (25 lbs)
• Depth Range, “Standard Unit” - 15 - 75 cm (Note: with
Extension Tubes, measuring depths can be increased).
• Cell Constant Values with Standard Deviation
- X = 35.22 ( + 0.18 (1%)
- Y = 2.16 ( + 0.04 (2%) 30

31. • Simply center the Tripod over the well
hole and slowly lower the Permeameter
so that the Support Tube enters the well
hole, being careful not to knock debris
off the sides of the well into the hole
bottom. Flexibility in the Tripod Base
allows the angle of the Tripod Legs to
be adjusted to accommodate variation in
slope of the land. The Tripod is used to
support the Permeameter in wells down
to approximately 38 cm (15 inches) in
depth. The tripod chain can be loosened
as necessary to allow the Tripod Legs to
flex. 31

32. Where…
a - Well radius, in cm.
C - Shape factor dependent primarily on the H/a ratio
C1, C2 - C factors corresponding to H/a
H2/a, respectively
H1, H2 = Well height for first and second measurements
respectively, in cm.
K - Hydraulic conductivity, in cm/sec.
Kfs - Field-saturated hydraulic conductivity (entrapped air
present), in cm/sec.
α - Alpha Parameter, slope of the line relating the natural
log of K, hydraulic conductivity, to Q, the soil water
pressure head, in cm-1
α* is obtained from the site analysis
Analysis
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33. References
• http://www.soilmoisture.com
• http://www.water-research.net
• www.specializedengineering.com
• www.gmeconsultants.com
• http://www.usyd.edu.au/agric/web04/Single
%20ring%20final.htm
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34. Thank You
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