Reduction of Permeability of Soil

This paper focuses on the study of the collapsible soil (sand) characteristics and how their property of permeability can be improved through fly ash application as well as cement addition. It discusses the importance of soil permeability in construction and engineering, and provides insights on the effects of different factors on the permeability of sand and silt soil.

REDUCTION OF PERMEABILITY OF SOIL
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ABSTRACT
The knowledge of soil structure is very crucial as far as building and construction is
concerned. Engineers rely on this particular knowledge to facilitate erection of structural stable
buildings and infrastructure. This particular paper focused on the study of the collapsible soil
(sand) characteristics and how their property of permeability can be improved through fly ash
application as well as cement addition. When using this test then it was considered very
important to perform as many replicate experiments as possible so to ensure that the observed
effect was the real and could be the basis of drawing conclusion. The equivalent or the average
permeability coefficient of the sand deposit commonly abbreviated Keq, was found to entire rely
on the flow direction in relation to the bedding plane orientation. The study further indicated that
addition of the fly ash also improved the permeability of the sand soil and silt by decreasing the
ratio of the voids.

Contents
ABSTRACT....................................................................................................................................................2
INTRODUCTION...........................................................................................................................................3
Background..............................................................................................................................................4
PROJECT DETAILS.....................................................................................................................................6
Roles and Responsibilities.......................................................................................................................8
Project Risk Assessment......................................................................................................................9
LITERATURE REVIEW....................................................................................................................................9
METHODOLOGY.........................................................................................................................................17
CEMENT AND FLYASH ADDITION...............................................................................................................18
Cement..................................................................................................................................................18
Flyash.....................................................................................................................................................18
PROJECT ANALYSIS AND FEASIBILITY.....................................................................................................19
RESULTS ANMD DISCUSSION.....................................................................................................................20
Results...................................................................................................................................................20
Samples with added cements and flyash...........................................................................................20
Samples without Cement and Flyash addition...................................................................................21
Discussion..............................................................................................................................................21
APPLICATIONS...........................................................................................................................................22
FUTURE WORK...........................................................................................................................................24
COST ANALYSIS......................................................................................................................................24
CONCLUSION.............................................................................................................................................25
REFRENCES................................................................................................................................................26

INTRODUCTION
One of the most engineering properties of the soil is the capacity to allow for the passage
of different kinds of fluids via the interconnecting voids present in it. As far as the branch of
science called soil mechanics is concerned, the study of soil permeability is very crucial aspect.
It is through such kind of the studies that the quantity of the underground passage or seepage
under various hydraulic situations is uncovered. In such studies, one of the key factors that have
been targeted is the coefficient of permeability whose value is obtained by the permeability test
of constant head. The constant is use in the calculations of the stability, filtration drainage and
finally settlement determination (Milunović et al 2017).
The above highlighted challenges are very important aspect of the environment when it
comes to control of the slope stability, management of waste water as well as the failure of
structures in relation to settlement issue s of the ground. The water movement as well as drainage
in any fine-grained soil have been treated as the main primary vital as fat as the study of soil
science, geotechnical engineering and hydrology is concerned. In the geotechnical engineering
field, there is significance influence of the permeability on the soil consolidation characteristics
alongside mobilization of the soil shear strength. This is because it is a consequence of the soil
drainage. Also the study of the sand seepage, flow of groundwater, problems of the slope
stability and other relevant topics will always need reliable information of the fine-grain soils
permeability properties.

In the case of the layered system of the soil, the bedding planes of such kind of the layers
can be either in vertical or horizontal or in extreme cases inclined. When this happens, every
layer will be expected to have its own coefficient value of the permeability commonly marked as
constant, K. The equivalent or the average permeability coefficient of the stratified deposit
commonly abbreviated Keq, will entire rely on the flow direction in relation to the bedding plane
orientation. The possible flow to be identified include: A flow which is parallel to the direction
of the soil and flow which appears to be perpendicular to the layer.
The other geological problems which are common are the dispersion, expansion as well as
collapsibility of soil. This simply implies reduced or inadequate bearing capacity of such soils.
The moisture sensitive soils or collapsible soils are characterized by high moisture content to the
extent that very little introduction of water contributes to the destruction of the soil particle
structure. In fact such will start to fall even before they become saturated fully. Such poor
characteristics of the sand soil are associated with the destruction of the structures in certain parts
of the UAE. The soil is therefore refered to as problematic types of soils. This particular project
has tried to analyses the permeability of the soil in selected areas of Al Ain and Sharjah through
scientific research methods that which included the prescribed test before presenting the facts as
they were.
Background
One of the basic properties of sand which actually deserves proper investigation is permeability.
This particular property was investigated both in the field and through comprehensive laboratory
work. While solving some of the geotechnical problems, the accurate knowledge of the
permeability property is very crucial. This should be determined with economically margin of

the reliable safety. There has been recognition of at least three categories of the problems
terotechnology where the data on the permeability is very essential including:
 Water retaining structures and dams
 Earth structures settlements on the deposits of the soft sand and silt soil over the world
 Problems of the environment as related to the hazardous as well as toxic disposal of
wastes.
One such practical example considered crucial as identified by the scholars is the impact
that the structure has in the case of the newly generated dam. In such studies the dam is treated as
very unique features of the geography. It is usually characterized by the creation of the large
hydraulic gradient. The research that had been conducted on similar structure was clear in the
illustration of permeability reduction in the sections of the foundation especially in the ratio
approximated to be 102.
This process actually led to the development of the creation of the underground barrier to
the hydraulics. On this particular barrier, there was concentration of the seepage action which
contributed to the system failure. This failure was through sliding of the foundation of the dam
along the fault found under the structure .The large structures natural foundation as well bas
man-made rock slopes are usually subjected to the water flow which is subsurface. Such flows
are closely linked to the natural conditions of hydrological circumstances including rain.
Some of these conditions like the floods of the river are very dangerous in terms of the
consequences considering that they are usually hard in the prediction index. In similar cases, the
hydraulic gradients are usually small as compared to those which have been induced by the
constructed structure s like the dams. One of the important aspects of the operation of these kinds

of the processes is that they are responsible for the generation of the forces that have the same
order of magnitude. Such magnitude of forces nearly resembles those acting on the masses as a
result of the gravitational impact.
Although there is a requirement of the proper analysis of the hydraulic barrier beneath the
structures on sand or silt soil, the results should be used for the future analysis of the impacts of
the properties of the soil when constructions are to be done.
PROJECT DETAILS
Goals and Objectives of the project
Aims and scope of the Research
The research work had the following general aims:
 To reduce swelling and shrinking of the soil samples under study
 To effectively prevent structure damage
 To achieve space reduction between soils which is collapsible
 To achieve crack reduction in the boundary walls which are consequences of
shrinking
Scope Definition
 Undrained Shear
There was considering of a single type of sand soil which had permanent water. This was
followed by the adoption of various experimental procedures in setting up the testing of
permeability starting from the form of slurry. The recent years has been characterized by several
attempts of the permeability testing. These testing have been artificial. They have involved the

use of liquid wastes as permeants besides traditional techniques of using water. The use of
different types of permeants on the soil samples subjected to the multitude histories of stress was
in attempts to duplicate the possible conditions of the silt and sand. Unlike other types of soil, the
permeability data of sand is expected to be greater than 1x10-7m/s for the effective establishment
of reliable decision of the support.
Constraints
 Accessibility to specific sites with unique soil characteristic was one of the major
challenges
 Project was relatively expensive
This particular research is actually concerned with the permeability measurement of the samples
of the silt and sand to properly investigate permeability development.
Project Management Approach
The project employed the synthesis approach whereby every stage or step was allocated its
sufficient period for the delivery.
Project Timeline

March
2019
April
2019
May
2019
June
2019
July
2019
August
2019
September
2019
Research and Preliminary Studies
Literature review
Proposal Writing
Class Presentation
School Presentation
Material Acquisition
Experimental work
Set up and Testing
Additional modification
Final Report Write Up
Final Presentation
Roles and Responsibilities
Provision of the most effective manner of soil permeability study

Project Risk Assessment
LITERATURE REVIEW
The technique in which the water flows past a porous soil material is very vital in the study of
soil mechanics and it:
 Includes the total volume of flow of the water past the soil particles, that is, the sand and
silt dam leakage determination.
 Includes the foundation settlement rate
 Includes the strength, that is, determining safety embankment issues
The flow of water in the soil does not follow any given formula from point to point with the
velocity being constant but in various directions of the soil pores. Bernoulli in his equation stated

that the sum of velocity head, elevation head and pressure head gives the total head at a
particular point of the flowing water(Lara et al 2017).
Where Pw/y= the fluid pressure head of a given unit length
V2/2g= fluid kinetic or the fluid velocity head of a given unit of length.
Due to the small velocities of the flowing water, the elevation head and the pressure head re also
small and therefore velocity head can be assumed.
Z= elevation head with regard to arbitrary datum. This is the measure of distance between the
datum and the head. in case the point appears to be under the datum, the value is negative and is
positive when the datum is below the point. This results into the formula below:
In which i= gradient of the hydraulic
L= length of flow past which head loss occurs
Darcy's Law:

The law mainly covers the flow velocity discharge in a saturated soil and can be expressed in the
formula below;
V=Ki
In which K is the coefficient of permeability in cm/s and V is the superficial or discharge
velocity.
Usually in determining the discharge velocity, it is assumed that;
-there is no friction between the joints
-the saturation of the soil is at its maximum
-the fluid is in laminar type of flow in which the number of Reynolds is less than one
In which v is the velocity of discharge
D10 is the effective diameter of the soil
~s is the water dynamic velocity
The flow of water past the molecules of the soil results into seepage forces or the drag forces on
the grains which alters the flow direction and at the same time alters the pressure of the pore
water and soil effective stress.
The value K which is the coefficient of permeability is determined by;
 shape of the soil particle

 structure of the soil
 pore sizes which depends of the sizes of the particles and how they are arranged
The permeability of the relies on the following factors;
Equation of Kozeny Carman:
The equations as per polssenles law indicates the effect of soil features and permeant on the
value of K.
The equations both presumes the joint pores of the soil acting as capillary tubes that provides
flow path for the water.
Permeability in sand and silt
According to Darcy, the flow of water through the pores of the soil is proportional to the
hydraulic gradient and can be given as;
q/A =-ki
Where q= rate of flow
A= cross-section area in relation to the flow direction

I= hydraulic gradient and
K= permeability or the hydraulic conductivity
The formula is based on the law of Darcy which is a very vital tool in the field of
research for conducting both experimental and theoretical work to determine the flow rate of
water in a porous soil. The law majors on the factors that influence the value of k which is the
hydraulic conductivity of the sand and silt. The ability of sand and silt soil to allow water to seep
through it depends on a number of factors ranging from compactness of the particles to whether
the soil sample used to determine the permeability is reconstituted from slurry or extracted from
a pure block. For that case, the preparation sample method and the type of sample used
determines the difference in values of permeability.
Factors that influence the permeability of sand and silt soil can be categorized into two, that is,
mechanical and compositional factors. Mechanical factors are composed of the hydraulic
gradient, the saturation level, methods and procedures involved in the test, and the conditions of
the initial stress. Compositional factors compost of the different mineral content of the sand and
silt, permeant features and mineralogy of the sand and silt. The two effects are somehow relayed
and impacts they have on permeability of sand and silt soil can be expressed in terms of their
effects on the fabric as well as structure of the sand and silt. Apart from these two factors,
changes in temperature and thixotropy (ageing factor of sand and silt) also affects permeability
of the sand and silt soil.
The table below gives the factors that mostly affect the permeability of sand and silt.

Theoretical permeability study on porous materials is based on set principles controlling the fluid
flow past a given small medium. The permeability according to the equation of Hagen-Poiseuille
of flow past the capillary tubes,
In which Vave is the average velocity of the flow
R is the capillary radius
ρP is the density of the fluid in the pore and
μ is the pore fluid viscosity

Hagen-Poiseuille, Kozeny and Carman depicted that the fluid flow in a structure composed of
channels of different sizes and shapes assumes a laminar flow, and together with the law of
Darcy the expression below for permeability of sand and silt was obtained.
In which ϒp is the specific weight,
μ is the permeant viscosity,
C is the factor of the shape of the pore,
S2 is the known surface of the particle per unit volume,
E is the void ratio and
T is the tortuosity factor expressed to be
Where L= apparent length of flow
Le= effective length of flow
Usually the influence of permeant features are taken care of in case the absolute permeability, K,
is

Assumptions which were made with regard to the equations above is that the viscous flow
complies with law of Poiseuille, the law od Darcy is correct, tortuosity of the mediums of flow
does not change and has a value of around 21/2 and that the sizes of the pores or channels are the
same. The equations in relation to Darcy’s law predicts the rate of flow in a porous material
which is saturated with liquid keeping on hold that the particles of the medium of flow are
approximately uniform, equal in its dimensions, of moderate size to allow for the conditions of
laminar flow. All these principles as well as the three conditions mentioned above can be
achieved in the prediction of the rate of flow through the sand particles.
The sand and silt voids are non-uniform and this is more important in the permeability as well as
the substantial correlation of permeability of the void ratio as was stressed on by a scholar. The
scholar specified on the physical features of the water within the pore with an immediate
alteration on vicinity of the surfaces of sand and silt in order to affect the model of viscous flow.
Another scholar on his study of a compact sand and silt indicated that permeability of sand and
silt is also affected by molding content of water, the void ratio, permeant feature and the
components of the soil.
According to this scholar, the changes in composition has no relation to both the equations of
Kozeny and Corman, he then made a conclusion that the structure of sand and silt is a very
important factor to consider in permeability control. It was concluded that the behavioral
differences observed between the equations of Kozeny and Carman and the explanations were
from the non-uniformity of the sizes of the pores in the fabric of sand and silt. A cluster model
which was put in place by a scholar to determine the effect of non-uniformity of the pores on

permeability of different samples showed a ratio of an estimated rate of flow to the predicted rate
of flow as in the graph below.
From the graph, it can be seen that;
 The value of measured permeability can either be high or low compared to the predicted
permeability value.
 There is a rapid decrease in measured value of permeability with porosity decrease for
compressions at porosities above 40% compared to the predicted permeability.
 The rapid of decrease reduces for measure permeability for compressions at porosities
below 40% compared to the measured permeability and
 Low rapid increase in measured permeability in case of rebound compared to the
predicted permeability.
Assuming that it is the pore of large size in the clusters of sand and silt particles through which
water flows but not the intra-cluster pores, the ratios of estimated rate of flow to that predicted by
the equation of Kozeny-Carman is can be obtained by;
In which et= ec +ep
and et is the ratio of void, ec is intra-cluster void ratio, ep is the inter-cluster void ratio and N is
the particles number in a cluster.
METHODOLOGY
 The analysis of drain size distribution

 The constant head permeability test
The analysis of drain size distribution
Test for the Constant Head Permeability
 Sieving is conducted to eliminate particles of large sizes. Measurement is taken for the
soil particle to aid in determining the volume. In determining the specific content of
moisture and density calculations are made for the total amount of dry soil and water
CEMENT AND FLYASH ADDITION
Cement
 Samples of sand and silt soil which was collected from different locations in the areas of
study were put into testing kits
 Varying amount of sand was then added at controlled/regulated amounts including 5%,
10%,12% and finally 15%.The samples were tested for the permeability properties
 The soil had varying densities of 17.5, 18.5 and finally 19.5 as expressed in kN/m3. This
became the point of understanding the effect of adding cement to the permeability of each
and every sample of the soil while closely relating to the sizes of the grain.
Flyash
 The collected soil samples of sand and silt were introduced into the testing kits. This
involved addition of different percentages of cement ranging from 5%, 10%,12% and
finally 15% to the two samples of the soil which was collected from three different
locations of AlAin & Sharjah) in UAE.

The soil had varying densities of 17.5, 18.5 and finally 19.5 as expressed in kN/m3. This became
the point of understanding the effect of adding cement to the permeability of each and every
sample of the soil while closely relating to the sizes of the grain.
Figure 1: Laboratory set up of Constant Head Permeability
PROJECT ANALYSIS AND FEASIBILITY
Various methods of permeability tests were effectively conducted in the laboratory by the use of
sand and silt soil. This was followed by the determination of the permeability coefficient for
these types of the layered soil (Mohanty et al 2017). The result analysis is as indicated below.

RESULTS ANMD DISCUSSION
Results
Samples with added cements and flyash
The results which were obtained from the experiment were tabulated as indicated below. Results
of Permeability of two layered soil System with Sand and silt combination were generally. The
easiest two-layer frameworks were acquired by following the penetrability technique with sand
and silt soil as the materials of individual layers. The addition of cement and flyash will
contributed to the increased density of the sand and silt samples. With these two soils samples
six two-layer frameworks were gotten with various extent of material. The table demonstrates the
examination between the comparable coefficients of porousness of the two-layer frameworks got
from the direct estimation and from the utilization of Darcy's condition.
The watched contrast between the two amounts is of the request of about 20%. As the estimation
of Keq is in the middle of Kinlet and Kexit, what's more, as the progression of stream over the whole

thickness of the stratified store must be guaranteed, it creates the impression that the coefficients
of porousness of both the layers framing the stratified store must be not quite the same as their
individual qualities when considered independently.
Samples without Cement and Flyash addition
Discussion
A permeability characteristic is considered to be one of the most important aspects of soil to be
studied. In general, there is preference of low permeability for all the activities which involve
improvement of the soil work. The used sand in the study was estimated to be having
permeability of 3.74*10-3.This is generally very high permeability. In order to achieve low

permeability of this particular sand soil sample, there was addition of cement in the first phase of
the experiment. According to the results were obtained from the laboratory work, cement was
found to be responsible for the reduction of the permeability of the sand. This was achieved due
to the fact that cement reduced the voids ratio. In this particular experiment, cement was used to
reduce the factor or the coefficient of the permeability. Analysis of the results obtained indicated
that the density of the soil also changed as the ratio of cement increased. In comparison, the
permeability of the soil samples from Sharjah was found to be higher than the permeability of
soil samples from AL AIN for every respective value of densities.
It is interesting to note that the increase in the densities of the collected soil samples
increased as the addition value of flyash and cement increased from 5% up to 12% with 12%
being regarded as the optimum percentage value. There was a drastic decrease in these values at
percentage beyond 12% say 15% and above. The best results from the permeability test were
thus found to be at 12% addition of cement and flyash.
APPLICATIONS
The slurry is put in a Rowe cell to be used in measuring the vertical measurement as well
as characteristics of compression therefore is not as difficult as inserting the block samples.
Whereas vertical block specimen is being set up in a Rowed cell is considered to be the most
reasonable straightforward as the specimen are being set up for horizontal measurement of the
characteristics flow since it is somehow easier due to the need of placing the rigid internal porous
drain. Due to necessary procedure intricacy therefore it is very possible the setting up of the
sample be done in a horizontal flow to allow the sample to introduce itself to some of distorting
factors into the permeability as well as permeability anisotropy values that can be observed as

their cooperation with the vertical flow characteristics that are normally measured on an identical
sample
It has been discovering that it is so very difficult and even not practical setting up
specimen inside Rowe cell under the water particularly in the horizontal low specimens.
Therefore, this makes the method to be abandoned only after very few trials in the early part of
the stud. Another procedure was employed a part from using the vacuum application.
Immediately when the specimen has been placed into the oedometer, the whole apparatus is the
put in water having an airtight chamber like a desiccator while the entire valve was opened. Then
the chambers are evacuated for 30 minutes to ensure that all the air bubble is removed and even
the desired permeant. In most cases it is very advisable when investigating any other strategy of
sample preparation.
The study of how the undrained shearing affect the kaolin permeability is very clear than
the inconclusive. Even though time in many cases has not permit a very extensive study while
the preliminary result obtained have showed that the response aspect to be further invested.
When using this test then it will very important to perform a s many replicate experiments as
possible so to ensure that the observed effect is the real one and are not experimental procedure
artifacts. The anisotropy was further observed to be reducing with the increase in compression
after the undrained shearing is curious and therefore be combined with a microscopy same of the
same so as to clarify there is a fabric anisotropy evidence that is changing in the similar
way(Vergani and Graf 2016).
Lastly, all the testing that had been reported to have been performed on artificial
laboratory sand and silt. Since this is the most convenient sand and silt used in the laboratory

study, since it presents most natural sand and silt. When the testing procedures that have reached
the reasonable confidence level then it is possible for the extraction of undisturbed sample from
different sofa/sift sand and silt site used to measure the permeability’s as well as comparison
permeability anisotropy using the values from the situ measurements. Anisotropy is very crucial
since it influences the sand and silt mechanical behavior and also the long term desirable
research aim is to relate the mechanical anisotropy that is need a very elaborate testing for it to
be evaluated.
FUTURE WORK
According to these reasons that showed that the test reported programmer here core found
not to be more extensive, though it was confirmed that there were some areas where the
additional testing is most preferable. The equipment that exist consist of three tank, a cylinder as
well as two process of filter, that are all designed to produce the best quality of the uniform block
samples, in providing sufficient quantity as well as in provision of sample preparation apparatus
range. Whereas the apparatus currently available for the permeability testing that is in horizontal
as well as in vertical direction that include a pair of Rowe cells each having a pair of GDS flow
pumps can be thereby expanded so to increase the advantages. Therefore, it is wary advisable to
wait for a long duration to ensure a full permeability testing particular stage whereas most
sample completed the consolidation as well as experiments shear phase. Therefore, an additional
oedometer set as well as the flow pump is very useful in case this type of research is to continue
and expand.
COST ANALYSIS
The project is expected to be more costly as the exercise seeks to give more details of the subject
matter under investigation. The collection of the data samples (types of soil from various

locations) was estimated to be $450. Experimental analysis equipment was estimated to cost $
500.Labour charges were estimated to $100
The total cost of the project $1050.
CONCLUSION
The study from the laboratory that was conducted on both two layers as well as two-layer soil
system that consist of various layer types, type of soil as well as those having different
proportional silt and sand soil and the result was that permeability equivalent coefficient varies
as per the calculated values according to the law of Darcy. The existed layer controlled the
permeability even if the permeability measure was considered lesser or greater than stratified
deposit theoretical values.
The soil permeability coefficient sometimes seems to be interactions function between the
soil as well as its surroundings of its contact. In case there is a need of avoiding ratio, thickness
as well as the type of soil in a layered system. Then therefore the consideration of the soil
coefficient permeability must be put into an account depending on the direction of flow, relative
position as well as the layer thickness since the study is based purely on experimental therefore
the study opens up the scopes for any further work and even where there is a need of obtaining
the mathematical equation of the layered soils.

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