Shree Swami Atmanand Saraswati Institute of Technology

Prepared By:-Korat Harshad 120763106022Mehta Moxesh 120763106024Dhameliya Dhaval 120763106025Vaghani Shaunak 120763106026

Seminar onMethods of in site Permeability Test

Guided By:-__________________1

Content

• Introduction

• Pumping Test

• Percolation Test

• Single Ring Falling Head Infiltrometer Test

• Double Ring Infiltrometer Test

• Slug tests

• Hazen Method

• Guelph Permeameter

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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.

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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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• 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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• 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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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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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.10

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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 Test12

• 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.

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• 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). Toanalyze the slug test data we need to match the data curve to one of a seriesof type curves.

• Each type curve consists of H/H0 values plotted against a range of η valuesfor a particular value of µ.

• In this case, we need to keep the Y axis of the two graphs the same, whilesliding the overlay along until the data points are matched by one of thecurves.

• The matched curve gives us an approximate value for mu, while readingthe time value from the data graph that is equivalent to eta = 1, gives us a t1value.

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• We can solve the following equations and find permeability

(K):

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Single Ring Falling Head Infiltrometer Test

• Principles:

Known boundary and pressureconditions are used to determine theunrestricted 3-dimensional infiltrationcapacity, of a soil confined below the single,steel ring. The ability for the soil to transmitwater (be permeable) is hence determinedthrough steady state calculations and, thisSaturated Hydraulic Conductivity (Ksat),which is universally used as an empiricalconstant to quantify specific, soil-water flowand infiltration capacity problems. Ksat “isone of the most important factors playing arole in many agronomic, engineering andenvironmental activities” (Herman et al, 2003)and hence, is a useful term to quantify.

Single ring Infiltrometer ; in action

Single ring Infiltrometer; finished16

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

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

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.

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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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.

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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.

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).

Estimated Methods- Based on Grain Size

Hazen Method:-

Applicability: sandy sediments

• K = C*d102

• 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

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Guelph and Amoozegar Borehole Permeameter

Field Testing 26

• 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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• 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.

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• 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

• 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

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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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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Thank You

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