civil engineering

1. GROUNDGROUND
IMPROVEMENTIMPROVEMENT
TECHNIQUESTECHNIQUES
Presented byPresented by
MOHAMMED. OSMAN ALI KHAN,MOHAMMED. OSMAN ALI KHAN,
B.Tech., (Civil) Final Year,B.Tech., (Civil) Final Year,
Medak College of Engineering.Medak College of Engineering.

2. Abstract:Abstract:
Ground Improvement is the most imaginativeGround Improvement is the most imaginative
field of geotechnical engineering. It is a field infield of geotechnical engineering. It is a field in
which the engineer forces the ground to adoptwhich the engineer forces the ground to adopt
the projects requirements, by altering the naturalthe projects requirements, by altering the natural
state of the soil, instead of having to alter thestate of the soil, instead of having to alter the
design in response to the grounds naturaldesign in response to the grounds natural
limitations. The results usually include saving inlimitations. The results usually include saving in
construction cost ad reduction of implementationconstruction cost ad reduction of implementation
time.time.

3. There are number of techniques available for
improving the mechanical and engineering
properties of the soil.
To improve the strength of the soils, especially
in case of granular type of soils, COMPACTION
METHODS are found as best methods among
all type of techniques. Based on the
mechanism applied for compacting the soil, it is
sub divided into different methods like dynamic
compaction, blasting, vibro techniques… etc.

4. Introduction:Introduction:
Large Civil Engineering Projects are beingLarge Civil Engineering Projects are being
executed in all over the country in order toexecuted in all over the country in order to
enhance the infrastructure of the country.enhance the infrastructure of the country.
Thus it is increasingly important for theThus it is increasingly important for the
engineer to know the degree to which soilengineer to know the degree to which soil
properties may be improved or otherproperties may be improved or other
alternations that can be thought of foralternations that can be thought of for
construction of an intended structure atconstruction of an intended structure at
stipulated site.stipulated site.

5. If unsuitable soil conditions are encountered at the
site of a proposed structure, one of the following four
procedures may be adopted to insure satisfactory
performance of the structure.
By pass the unsuitable soil by means of deep
foundations extending to a suitable bearing material.
Redesign the structure and it’s foundation for
support by the poor soil. This procedure may not be
feasible or economical.
Remove the poor material and either treat it to
improve and replace it (or) substitute for it with a
suitable material.
Treat the soil in place to improve its properties.

6. Ground ImprovementGround Improvement
Techniques:Techniques:
On the basis of mechanism by which they improveOn the basis of mechanism by which they improve
the engineering properties of soil, the most ofthe engineering properties of soil, the most of
common of these can be divided into the followingcommon of these can be divided into the following
major categories. These aremajor categories. These are
 Densification Techniques.Densification Techniques.
 Reinforcement Techniques.Reinforcement Techniques.
 Stabilization Techniques.Stabilization Techniques.
 Miscellaneous Methods.Miscellaneous Methods.
Apart from the methods listed above, there areApart from the methods listed above, there are
some other simple methods like removal andsome other simple methods like removal and
replacement of soil. In this paper these arereplacement of soil. In this paper these are
discussed first before taking up above techniques.discussed first before taking up above techniques.

7. Removal and Replacement ofRemoval and Replacement of
Soil:Soil:
One of the oldest and simplest soilOne of the oldest and simplest soil
improvement methods is to simply excavateimprovement methods is to simply excavate
the unsuitable soil and replace them withthe unsuitable soil and replace them with
compacted fill. This method is often usedcompacted fill. This method is often used
when the problem the soil is that it is toowhen the problem the soil is that it is too
loose. In that case, the same soils used toloose. In that case, the same soils used to
build the fill, except now it has a higher unitbuild the fill, except now it has a higher unit
weight (because of compaction) and thus hasweight (because of compaction) and thus has
been better engineering properties. This is abeen better engineering properties. This is a
common way to remediate problems withcommon way to remediate problems with
collapsible soils.collapsible soils.

8. Removal and replacement is generallyRemoval and replacement is generally
practical only above the ground waterpractical only above the ground water
table. Earthwork operations become moretable. Earthwork operations become more
difficult when the soil is very wet, evendifficult when the soil is very wet, even
when the free water pumped out, and thuswhen the free water pumped out, and thus
are generally avoided unless absolutelyare generally avoided unless absolutely
necessary.necessary.

9. Pre-compression of Soil:Pre-compression of Soil:
 It requires only conventional equipmentIt requires only conventional equipment
earthmoving equipment, which is readilyearthmoving equipment, which is readily
available. No special or proprietary equipment isavailable. No special or proprietary equipment is
needed.needed.
 Any grading contractor can perform the workAny grading contractor can perform the work
 The results can be effectively monitored by usingThe results can be effectively monitored by using
appropriate instrumentation and ground levelappropriate instrumentation and ground level
surveys.surveys.
 The method has a long track record of success.The method has a long track record of success.

10.  The cost is comparatively low, so long as soil forThe cost is comparatively low, so long as soil for
preloading is readily available. However, therepreloading is readily available. However, there
also are disadvantages.also are disadvantages.
 The surcharge fill generally must extendThe surcharge fill generally must extend
horizontally at least 10m beyond the perimeter ofhorizontally at least 10m beyond the perimeter of
the planned construction. This may not possiblethe planned construction. This may not possible
for confined sites.for confined sites.
 The transport of large quantities of soil onto theThe transport of large quantities of soil onto the
sites may not be practical, or may havesites may not be practical, or may have
unacceptable environmental impacts (i.e., dust,unacceptable environmental impacts (i.e., dust,
noise, traffic) on the adjacent areas.noise, traffic) on the adjacent areas.
 The surcharge must remain in place for months orThe surcharge must remain in place for months or
years, thus delay in construction.years, thus delay in construction.

12. Densification Techniques:Densification Techniques:
The strength and stiffness of the soil isThe strength and stiffness of the soil is
higher when the particles are packed in ahigher when the particles are packed in a
dense configuration than they are packeddense configuration than they are packed
loosely. As a result, densification is one ofloosely. As a result, densification is one of
the most effective and commonly usedthe most effective and commonly used
means of improving soil characteristics. Thismeans of improving soil characteristics. This
can be approaches in following ways.can be approaches in following ways.

13. Vibro Techniques:Vibro Techniques:
Vibro techniques use probes that areVibro techniques use probes that are
vibrated through soil deposit in a gridvibrated through soil deposit in a grid
pattern to densify the soil over the entirepattern to densify the soil over the entire
area of thickness of the deposit. Thesearea of thickness of the deposit. These
are classified in to the following methods.are classified in to the following methods.
These areThese are

14. 1Vibro Compaction:1Vibro Compaction:
Vibro Compaction is a method forVibro Compaction is a method for
compacting deep granular soils by repeatedlycompacting deep granular soils by repeatedly
inserting a vibratory probe. It is also knowninserting a vibratory probe. It is also known
as VIBRO DENSIFICATION.as VIBRO DENSIFICATION.
By inserting depth vibrations, theBy inserting depth vibrations, the
vibrations are produced by rotating a heavyvibrations are produced by rotating a heavy
eccentric weight with the help of an electricaleccentric weight with the help of an electrical
motor with in the vibrator. The vibratorymotor with in the vibrator. The vibratory
energy is used to rearrange the granularenergy is used to rearrange the granular
particles in a denser state. Penetration of theparticles in a denser state. Penetration of the
vibro is typically aided by water jetting at thevibro is typically aided by water jetting at the
tip of the probe.tip of the probe.

15. The Vibro-Compaction
Process

16. Some of advantages andSome of advantages and
disadvantages of this method aredisadvantages of this method are
given below.given below.
 It is often an economical alternative toIt is often an economical alternative to
deep foundations, especially whendeep foundations, especially when
considering the added liquefactionconsidering the added liquefaction
protection in seismic ares.protection in seismic ares.
 It is most effective in granular soilsIt is most effective in granular soils
 It cannot be sued in cohesive soils.It cannot be sued in cohesive soils.

17. Vibro Flotation:Vibro Flotation:
In vibro floatation a torpedo like probe (theIn vibro floatation a torpedo like probe (the
vibro float) suspended by a crane is used tovibro float) suspended by a crane is used to
density a soil deposit. Vibro floats usually 12 to 18density a soil deposit. Vibro floats usually 12 to 18
inch in diameter and about 10 to 16 ft long, containinch in diameter and about 10 to 16 ft long, contain
weights mounted eccentrically on a central shaftweights mounted eccentrically on a central shaft
driven by electric or hydraulic power.driven by electric or hydraulic power.
The vibro float is initially lowered to the bottomThe vibro float is initially lowered to the bottom
of the deposit by a combination of vibration andof the deposit by a combination of vibration and
water or air jetting through ports in its pointed nosewater or air jetting through ports in its pointed nose
cone. The vibro float is then incrementally withcone. The vibro float is then incrementally with
drawn in 2 to 3 ft intervals at an over all rate ofdrawn in 2 to 3 ft intervals at an over all rate of
about 1ft/min to loosen the soil above the vibroabout 1ft/min to loosen the soil above the vibro
float temporarily and aid in its with drawl. Thefloat temporarily and aid in its with drawl. The
vibrations produce a localized zone of temporaryvibrations produce a localized zone of temporary
liquefaction that causes the soil surrounding theliquefaction that causes the soil surrounding the
vibro float to densify.vibro float to densify.

18. Principle of the techniquePrinciple of the technique
 Vibro floating is most effective in clear granularVibro floating is most effective in clear granular
soils with the contents less than 20% and claysoils with the contents less than 20% and clay
contents below 3%contents below 3%
 Vibro flotation has been used successfully toVibro flotation has been used successfully to
density soils to deep [this of up to 115ft]density soils to deep [this of up to 115ft]

19. Dynamic Compaction:Dynamic Compaction:
Dynamic Compaction is normally used under theDynamic Compaction is normally used under the
following circumstances:following circumstances:
 To increase in-situ density and this way improve theTo increase in-situ density and this way improve the
bearing capacity and consolidation characteristics ofbearing capacity and consolidation characteristics of
soils (or waste materials) to allow conventionalsoils (or waste materials) to allow conventional
foundation and surface bed construction to be carriedfoundation and surface bed construction to be carried
out. The technique typically improves the in-situ soilsout. The technique typically improves the in-situ soils
such that allowable bearing pressures of up to 250such that allowable bearing pressures of up to 250
kpa can be used with foundation settlements of thekpa can be used with foundation settlements of the
order of 10 to 20 mm.order of 10 to 20 mm.
 To increase in-situ density and in this way improve in-To increase in-situ density and in this way improve in-
situ permeability and/or reduce liquefaction potential.situ permeability and/or reduce liquefaction potential.

20. What soils are suitable:What soils are suitable:
Most soil types can be improved,Most soil types can be improved,
including silts and some clays. The mostincluding silts and some clays. The most
commonly treated soils are old fills andcommonly treated soils are old fills and
granular virgin soils. Soils below the watergranular virgin soils. Soils below the water
table are routinely treated. However, carefultable are routinely treated. However, careful
control has to be used to allow dissipation ofcontrol has to be used to allow dissipation of
excess pore pressures created during theexcess pore pressures created during the
weight dropping.weight dropping.

21. Blasting:Blasting:
 Blasting is most effective in loose sandsBlasting is most effective in loose sands
that contain less than 20% silt and lessthat contain less than 20% silt and less
than 5% clay.than 5% clay.
 Although blasting is quite economical, it isAlthough blasting is quite economical, it is
limited by several considerations, as itlimited by several considerations, as it
produces strong vibrations that mayproduces strong vibrations that may
damage near by structures or producedamage near by structures or produce
significant ground movements.significant ground movements.

22. Reinforcement Techniques:Reinforcement Techniques:
In some cases it is possible to improveIn some cases it is possible to improve
the strength and stiffness of a existingthe strength and stiffness of a existing
soils deposit by installing discretesoils deposit by installing discrete
inclusions that reinforce the soil. Theseinclusions that reinforce the soil. These
inclusions may consist of structuralinclusions may consist of structural
materials, such as steel, concrete ormaterials, such as steel, concrete or
timber and geomaterials such as densifiedtimber and geomaterials such as densified
gravel.gravel.

23. Compaction Piles:Compaction Piles:
Compaction piles improve the seismic performance ofCompaction piles improve the seismic performance of
a soil by three different mechanisms. First the flexurala soil by three different mechanisms. First the flexural
strength of piles themselves provides resistance to soilstrength of piles themselves provides resistance to soil
movement (reinforcement). Second, the vibrationsmovement (reinforcement). Second, the vibrations
and displacements produced by their installationand displacements produced by their installation
cause densification. Finally, the installation processcause densification. Finally, the installation process
increses the lateral stress in the soil surrounding theincreses the lateral stress in the soil surrounding the
piles.piles.
Compaction piles generally densify the soil with in aCompaction piles generally densify the soil with in a
distance of 7 to 12 pile diameters and consequentlydistance of 7 to 12 pile diameters and consequently
installed in a grid pattern. Between compaction piles ainstalled in a grid pattern. Between compaction piles a
relative density of up to 75% to 80% are usuallyrelative density of up to 75% to 80% are usually
achieved. Improvement can be obtained withachieved. Improvement can be obtained with

24. JETJET
GROUTINGGROUTING

25. JET GROUTINGJET GROUTING
In jet grouting the soil is mixed with cementIn jet grouting the soil is mixed with cement
grount injected horizontally under highgrount injected horizontally under high
pressure in a previously drilled bore hole.pressure in a previously drilled bore hole.
Jet grouting uses a special pipe equippedJet grouting uses a special pipe equipped
with horizontal jets that inject grout into thewith horizontal jets that inject grout into the
soil at high pressure. The pipes are firstsoil at high pressure. The pipes are first
inserted to the desired depth, then they areinserted to the desired depth, then they are
raised and rotated while the injection is inraised and rotated while the injection is in
progress, thus forming a column of treatedprogress, thus forming a column of treated
soil.soil.
Because of high pressure, this method isBecause of high pressure, this method is

26. Electro Osmasis and ElectroElectro Osmasis and Electro
Chemical Hardening Method:Chemical Hardening Method:
The electroosmasis process can be used to increaseThe electroosmasis process can be used to increase
the shear strength and reduce the compressibility ofthe shear strength and reduce the compressibility of
soft clayey and silty soils beneath foundation. Bysoft clayey and silty soils beneath foundation. By
introducing an electrolyte such as calcium chloride atintroducing an electrolyte such as calcium chloride at
the anode, the base exchange reaction between thethe anode, the base exchange reaction between the
iron anode and surrounding soil is increased, resultingiron anode and surrounding soil is increased, resulting
in the formation of ferric hydroxides which bind the soilin the formation of ferric hydroxides which bind the soil
particles together. However because cost of electricparticles together. However because cost of electric
power and wastage of electrodes, electroosmasis withpower and wastage of electrodes, electroosmasis with
or without electrochemical hardening can beor without electrochemical hardening can be
considered only for special situations where theconsidered only for special situations where the
alternative of piling cannot be adopted.alternative of piling cannot be adopted.

27. Conclusion:Conclusion:
 Unfavorable soil conditions can frequently beUnfavorable soil conditions can frequently be
improved using soil improvement techniques. Aimproved using soil improvement techniques. A
variety of soil improvement techniques have beenvariety of soil improvement techniques have been
developed. However a suitable technique has todeveloped. However a suitable technique has to
be adopt according to necessity of the structurebe adopt according to necessity of the structure
and economy.and economy.
 Mainly soil improvement techniques can beMainly soil improvement techniques can be
divided in to four broad categories; Densificationdivided in to four broad categories; Densification
technique, Reinforcement technique, grouting ortechnique, Reinforcement technique, grouting or
mixing technique and stabilization technique.mixing technique and stabilization technique.

28.  Densification is probably the most commonly usedDensification is probably the most commonly used
soil improvement technique. Most densificationsoil improvement technique. Most densification
techniques relay on tendency of granular soils totechniques relay on tendency of granular soils to
densify when subjected to vibrations. Howeverdensify when subjected to vibrations. However
there is a possibility of damaging adjacentthere is a possibility of damaging adjacent
structures and pipelines due to application of thisstructures and pipelines due to application of this
technique.technique.
 Reinforcement techniques introduce discreteReinforcement techniques introduce discrete
inclusions that stiffen and strengthen a soilinclusions that stiffen and strengthen a soil
deposit. The high stiffness and strength of thedeposit. The high stiffness and strength of the
inclusions also tend to reduce the stressesinclusions also tend to reduce the stresses
imposed on the weaker materials between theimposed on the weaker materials between the
inclusion.inclusion.

29. Thank YouThank You