Applicability, Quality Control and Quality Assurance in

Report
Applicability, Quality Control and Quality
Assurance in Ground Improvement
Presented by
Kulbir Singh Gill,
Associate Prof. GNDEC,
Ludhiana
INTRODUCTION
 Unfortunately, soils are made by nature and not by man,
and the products of nature are always complex(Karl
Terzaghi 1936).
 The advancement in geotechnical engineering has
provided many alternatives to deal with the problems
encountered during soil investigation for the site selection
of a particular project.
 Since the safety of lives and property are at stake, it is
important to consider the geotechnical merits or demerits
of various sites before the final decision is taken for that
project.
 Moreover risks and costs needs to be evaluated.
Contd.
 Due to the lower value of land to population ratio in India, it
is utmost important to utilize any type of land available for
construction.
 So keeping in view the above stated problem , different types
of ground improvement techniques are adopted to make the
weak soils suitable to meet the minimum requirement for
any particular project.
 The various types of ground improvement techniques which
are commonly used are:
Contd.
 Improvement by vibro compaction
 Ground improvement using vibro replacement
 Ground improvement using deep soil mixing
 Ground improvement using permeation grouting.
 Improvement by increasing effective stresses.
 Improvement by admixtures.
 Geotechnical reuse of waste materials.
 Weight reduction.
 In this presentation only the applicability, quality control and
quality assurance are covered.
Applicability of the Vibro Compaction
 This technique is used to increase the bearing capacity
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of foundations and to reduce their settlements.
Another important application is to mitigate the
liquefaction potential in earth prone areas by
densification of sand.
Vibro compaction can be used to support any type of
projects from embankment to chemical plants.
Mainly this technique depends on the granular soil to
be compacted.
So far the deposits down to 65m have been improved
by vibro compaction.
Quality Control and Quality Assurance
 In general quality control programme is divided into
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categories, namely monitoring of compaction parameters
and post compaction testing.
The compaction parameters(depth and power
consumption) are monitored using computerized systems.
Post-compaction testing is performed to ensure that the
specifications are met.
Dynamic penetrometer tests(DPT),standard penetration
tests(SPT) and cone penetration tests(CPT) is most popular
post compaction test.
At least one week cooling period must be given after the
compaction in order to dissipate the excess pore water
pressure to initial level before compaction.
Limitations
 Vibro compaction technique is most effective for
sands and gravels with fines less than 15 to 20% as
shown in Figure
Applicability of Ground Improvement
using Vibro Replacement
 : The unique characteristic of the vibro replacement technique is
that it is able to treat a vide range of weak soils from loose silty
sands, soft marine clays, ultra soft silts and clay from mine tailings,
garbage fill to peaty clays.
 The various types of structures which can be supported soil
improved by vibro replacement are simple earth embankments,
modern expressway embankments, bridge approaches, high speed
railway embankments, marine and offshore structures,
seaport/airport facilities, power plant structures, chemical plants,
sewerage treatment plants and large storage tanks.
 The basic aim of vibro replacement is to increase the stability and
bearing capacity of weak soil as well as to restrict the settlement.
In earthquake prone areas it has also been used to mitigate
liquefaction potential.
Quality Control and Quality Assurance in
Vibro Replacement
 In vibro replacement method, quality control monitoring
consists of monitoring of column construction parameters
and post construction testing.
 During construction, the main parameters of the
construction process(depth, vibration energy during
penetration and compaction processes and stone
consumption) are recorded continuously as a function of
time, thus ensuring the production of a continuous well
compacted column.
 The performance of vibro stone columns is assessed using
plate load tests which should be carried out by loading a
rigid steel plate or cast in situ concrete big enough to span
one or more columns and the intervening ground.
Contd.
 . In contrast to the more familiar load tests in piles, both the
column and the tributary area of soil around the column are
loaded.
 In addition, the performance of the treated soil to support the
intended structure is evaluated based on the results of
instrumentation such as rod settlement gauges, inclinometers, etc.
Limitations:
 Vibro stone columns are not suitable in liquid soils with very low
undrained shear strength, because the lateral support may be too
small.
 In general, the technique is applied to structures with high order
of settlement tolerance.
Applicability of Deep Soil Mixing
 The technology of deep soil mixing can be implemented on
wide range of weak and problematic soil types such as loose
sands, soft marine clays, ultra soft slimes, weak silty clays and
sandy silts.
 Typical applications include foundation s of embankment fill
for roads, highways ,railways and runways; slope
stabilization, stabilization of cuts and
excavations(Topolinicki,2004 and Raju et.al., 2005).
 The DSM technology can also be used for vibration reduction
applications and to partially reduce water paths for water
tight applications.
Quality Control and Quality Assurance
of Deep Mixing Soils.
 For both wet and dry deep soil mixing ,quality control during
execution is important to ensure uniform improvement of soil and
to ascertain that the required amount of binder has been mixed
uniformly over the entire depth of treatment .
 For this purpose, the mixing units are equipped with automated
computerized recording devices to measure the real-time
operating parameters such as depth of mixing tools, volume or
weight of binder used etc.
 After allowing for sufficient curing period(typically,3 to 4 weeks),
the mixed columns can also be tested using single/group column
plate load tests, unconfined compressive strength tests on
cored/backflow samples, visual examination of exposed columns,
etc.
Applicability of Ground Improvement
using Permeation Grouting
 This type of grouting is very effective in sands gravels,
coarser size materials(e.g .boulders and cobbles) and
fissured, jointed and fractured rock formations.
 The technique is well suited for a wide variety of
applications, such as foundation retrofitting, dam
rehabilitation, subsidence and liquefaction mitigation etc.
 Applications can be categorized into the following general
areas, site improvement, foundation rehabilitation,
excavation support, ground water control.(Karol, 1990).
Applicable soil types for Permeation
Grouting
Limitations
 Permeation grouting is not suitable in cohesive soils
such as silts and clays.
 The other types of grouting techniques such as
fracturing grouting and jet grouting can be considered
to improve such soils.
Applicability of Ground Improvement
using Weight Reduction
 This technique involves reduction of weight applied to
a soft compressible soil by the use of light weight fill
material.
 The over all benefits gained from the light fill
materials include reduced settlement, increase in
slope stability and reduced lateral earth pressure on
retaining structures.
 A key benefit is material’s high resistant to earthquake
effects (the low unit weight results in lower seismic
inertial forces).
Light Weight Materials used for
Ground Improvement
Fill Material
Source/Process
Dry Unit Weight (Kg/m3)
Wood fibres
Sawed lumber waste
550-960
Shredded tyre
Mechanical cut tyre chips
600-900
Calm shells
Dredged under water deposits
1100-1200
Expanded shale
Vitrified shale or clay
600-1040
Fly ash
Residue of burned coal
1120-1400
Air-cooled slag
Blast furnace material
1100-1500
Flowable fill
Foaming agent in a concrete matrix
335-770
Geofoam
Block moulded expanded polystyrene
12-32
Quality Control and Quality Assurance in Ground
Improvement using Weight Reduction:
 The key issues with the weight reduction method of ground
improvement are to placement of the light weight material
and its durability and long-term performance.
 Well planned laboratory experimentation is needed to
optimize the use and performance of light weight materials .
 Durability can be checked in the laboratory.
Limitations
 Some of the material are susceptible to various types of
problems after their placement in the field, e.g. geofoam can
easily catch fire also deterioration can occur gasoline spills or
insect borrowing.
 Continued crushing and knitting of the shells during
compaction of the shells under the influence of vehicular
traffic may reduce the drainage potential of embankment.
 Thus resulting in ponding of water at the surface and also it
may reduce the frictional angle of the material, thus
increasing the lateral pressure on the supporting structures.
Applicability of Ground Improvement
using Admixtures.
 Use of various admixture such as lime, cement, fly ash and furnace slag are
well understood to the geotechnical engineers.
 But recently several environmental friendly enzymes have come into the
market such as Fujibeton, Terrazyme and Renolith etc. These materials are yet
to gain popularity in the field of ground improvement.
 The fujibeton material, developed in Japan, is climatically stable material and
suitable for stabilization of all types of soils. Basically, the product is an
inorganic polymer that chemically binds with all compounds when blended
with OPC in 1 to 3% by weight. The blended mix is called fujibeton mix.
 The technology can be advantageously used in the construction of low volume
roads where aggregates are not available at economical rates but also for all
type of soil conditions
 . Fujibeton improves CBR of the subgade and does not create shrinkage cracks
and is there for highly effective for clayey soils. With fujibeton, a high dry
density is obtained with minimum compaction, therefore simple and small
equipments are sufficient for construction.
Terrazyme
 Terrazyme is a natural, non-toxic, environmentally safe, bio
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enzyme product that improves engineering properties of soil.
The function of terrazyme is to minimize absorbed water in the
soil for maximum compaction, which decreases the
swelling capacity of soil particles and reduces permeability.
The application of terrazyme enhances weather resistance and
increases load bearing capacity of soils especially in clayey
soils.
This will provide cost effective both in the initial construction cost
and maintenance cost of roads.
Terrazyme technology is also advantageous in:considerable
improvement in the soil CBR.Minimum loss of gravel due
to erosion or abrasion by the traffic preserving original
transverse section.
Renolith
 Renolith is a polymer based chemical, which is
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environmentally friendly and facilitates the bonding of soil
mass.
The soil-cement with renolith has a high modulus of elasticity
and can disperse the wheel loads very effectively.
It is a semi rigid material.
This type of construction does not require surfacing for low
volume roads, since the base course is stabilized.
It is expected to give good performance with longevity and
reduces maintenance costs and almost dust free environment
Quality Control and Quality Assurance in
Ground Improvement using Admixtures
 The design concept is based on the optimization of admixture
quantity for stabilization based on unconfined compressive
strength or CBR test results determined on the given soil for
different proportions of soil and admixtures.
 After the construction ,core can be taken and tested for
unconfined compressive strength in the laboratory.
 Limitations: Limited research is available with soil cement
and these admixtures in abroad but similar studies are yet to
be carried out in India
Thanks

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