Transcript GIT-SDP - Guru Nanak Dev Engineering College

Ground Improvement and Ground
Control including Waste
Containment with Geosynthetics
Dr. J.N.Jha,
Professor and Head (Civil Engineering),
Guru Nanak Dev Engineering College,
Ludhiana, Punjab-141006
Ground Improvement Tehnique: Issues,
Methods and their Selection
Present Day Scenario
• Best buildable lands not available for construction
• Available sites are having low strength because :
 Filled up sites,
 Low lying water logged,
 Waste lands,
 Creek lands with deep deposits of soft saturated
marine clays
• Another problem: Design loads are high and the site
is situated in seismic zones
What are the options?
•Traditional foundation techniques sometimes costlier than
the super structure and in many situations can’t be built
•when a poor ground exists at the project site, designer
faces following questions:
Should the poor ground be removed and replaced with a
more suitable material?
Should the weak ground be bypassed laterally by
changing the project’s location or vertically by the use of
deep foundations? or
Should the design of the facility (height, configuration,
etc) be changed to reflect the ground’s limitations?
•Development of ground improvement, gives the
designer/bulder has a fourth option
To “fix” the poor ground and make it suitable for the
project’s needs
• Now the designer/builder faces new questions:
Should the problematic ground at the project site be
fixed instead of bypassed?
What are the critical issues that influence the successful
application of a specific fixing tool? And
Which fixing tool to be used from comprehensive
and diversified set currently available in the tool box?
What are the major functions of Ground improvement in
soil ?
(1) To increase the bearing capacity
(2) To control deformations and accelerate consolidation
(3) To provide lateral stability
(4) To form seepage cut-off and environmental control
(5) To increase resistance to liquefaction
• Above functions can be accomplished :
 by modifying the ground’s character - with or without
the addition of foreign material
The current state of the practice:
•Densification
•Consolidation
•Weight reduction
•Reinforcement
•Chemical treatment
•Thermal stabilization
•Electrotreatment
•Biotechnical stabilization
Ground Improvement by Densification
Methods of Application :
 Vibrocompaction
Dynamic Compaction
Blasting
Compaction Grouting
Key Issues affecting densification:
(a)
(b)
(c)
(d)
(e)
Percent of fines in the soil,
Ability of the soil to dissipate excess pore water pressure,
Energy felt by the soil,
Presence of boulders, utilities and adjacent structures, and
Mysterious phenomenon of ageing.
Ground Improvement by Consolidation
Methods of application:
Preloading with or without vertical drains
Electro-osmosis
Vacuum consolidation
Key Issues associated with consolidation:
(a)stability during surcharge placement,
(b)clogging of vertical drains, and
(c)maintenance of the vacuum.
Ground Improvement by Weight Reduction
Methods of Application:
•Placing lightweight materials over the native soil in
one of three ways:
spread in a loose form, then compacted
cut in block forms, then stacked according to a
certain arrangement, or
pumped in a flowable liquid form
key issues with the weight reduction method
(a) Placement of the lightweight material,
(b) Longevity and long-term performance.
Ground Improvement by Reinforcement
Methods of Application:
Mechanical stabilization
Soil nailing
Soil anchoring
Mirco piles
Stone columns
Fiber reinforcement
Key Issues Affecting Soil Reinforcement:
(a)Load transfer to the reinforcing elements,
(b)Failure surface of the reinforced soil mass,
(c)Strain compatibility between the soil and the reinforcement,
(d)Arrangement of the reinforcing elements,
(e)Durability and long-term behavior of the reinforcements.
Ground Improvement by Chemical Treatment
Methods of Application:
Permeation grouting
Jet grouting
Deep soil mixing
Lime columns
Fracture grouting
Key Issues involved in Chemical Treatment
(a)soil-grout compatibility and reactivity,
(b)operational parameters,
(c)column verticality, and
(d)weathering effects
Ground Improvement by Thermal Stabilization
Methods of Application:
Ground freezing
Vitrification
Key Issues of thermal stabilization
(a)Degree of saturation of the soil,
(b)Rate of groundwater movement,
(c)Creep potential of the frozen ground,
(d)Post thawing behavior,
(e)Heat transfer in the melted soil and
(f)Impact of heat on utilities and adjacent structures.
Ground Improvement by Electrotreatment
Methods of Application:
Electrokinetic remediation
Electroheating
Electrokineting fencing
Bioelectrokinetic injection
Key Issues in Electrotreatment
(a)Soil’s electrical conductivity,
(b)Ionic characterization of the contaminants, and
(c)Impact on buried objects and utilities
Ground Improvement by Biotechnical
Stabilization
Methods of Application:
Brush layering
Contour wattling
Reed-trench layering
Brush matting
Live staking and others
key issues affecting biotechnical stabilization
(a)Development of artificial cohesion in the ground,
(b)Effects of evapotranspiration, and
(c)Durability of the vegetation
Factors affecting the selection of a ground
improvement method
(a)Ground,
(b)Groundwater
(c)Construction considerations including schedule,
materials, accessibility, right-of- way, equipment and
labor
(d) environmental concerns,
(e) durability, maintenance and operational requirements
(f) contracting, politics and tradition,
(g) cost
Waste Containment with Geosynthetics
Large quantities of waste are being produced
since 1990 due to Rapid industrialisation and
Excessive urbanisation
Waste needs to be disposed off and only disposal
bin is ground and it occupies large chunk of land.
 One million ton of municipal solid waste
occupies approximately one million square meter
(One square kilometer of land area when waste is
spread uniformly with a thickness of one meter)
Other problem associated with waste disposal
Another problem with the disposal of waste :
Source of pollution
Contaminates the soil beneath the waste
Contaminates the ground water as
contaminants travel from the solid waste to
the subsurface environment
Other sources of subsurface contamination
Ponding or impoundment of Liquid Waste :
Slurry type liquid waste
Leakage from storage of liquids in underground
tanks
Leakage from pipelines that transport liquid
Accidental spills of toxic liquid
Application of fertilizers , pesticides on large
agricultural areas
How to tackle and minimise this damage
Design and implementation of solution for
detection, control, remediation and prevention of
subsurface contamination
Protection of uncontaminated land
Analysis of the fate of contaminants on and in
the ground including transportation through
geomedia
Use of waste material on and in the ground for
geotechnical construction
Pollution:MSW/ISW
Municipal solid waste/Industrial solid waste place on the
ground: two most significant source of subsurface
contamination
Water infiltrates into waste and reacts physically,
chemically and biologically to produce leachate
Leachate infiltrates into the ground causing subsoil and
ground water contamination
Solid waste continues to stay at the location where it is
placed for years
Therefore the process of leachate infiltration into
subsurface environment continues , slowly but surely for
several yearss
Control and Remediation
Clean up of soil involves - Treatment of three phases in
soil:Solid soil particle, Liquid pore fluids and Pore gases
Methods
Controlling the spread of polluted zone by installing
impermeable vertical barriers (cut-off walls) all around
and horizontal cover above the contaminated site
Removing the source of contamination and placing it in
designed facility
Excavating the affected soil, washing it or teating it and
placing it back after treatment
Pumping out the contaminated ground water by using a
set of tube wells installed in the
Contaminated zone , treating the ground water and the
injecting the purified waterback (Pump and Treat
Method)
Pumping out pore gas from the unsaturated zone using
gas wells and allowing air to enter through injection
wells
Using micro-organism to biomediate the sub soil and
ground water by transforming or immobilzing the
contaminants
Using thermal treatment e.g. incineration
Control of subsurface contamination for
new facility
For solid waste: Providing impermeable flexible liners at
the base and covers on top of all Solid waste disposal
facilities to minimize leachate formation
For slurry type waste: Providing storage in ponds and
impoundments having incrementally raised
embankments and impermeable flexible liners at the base
For liquid: providind storage in ponds with impermeable
flexible liner
For underground liquid storage facility: Providing
double walle tanks with leakage detention system placed
between the walls
Thankyou...............