Environmental Geomechanics: A Recent Development in Environmental Geomechanics: A Recent Development in Geotechnical EngineeringGeotechnical Engineering

DR. D. N. SINGHDR. D. N. SINGHPROFESSORPROFESSOR

Geotechnical Engineering DivisionGeotechnical Engineering DivisionDepartment of Civil EngineeringDepartment of Civil Engineering

I.I.T. BOMBAYI.I.T. BOMBAY

dns@civil.iitb.ac.in

"...to design and construct public works..."

Civil Engineering

Practice of improving and maintaining the built and natural environment to enhance

the quality of life for present and the generations to follow

Transformation

Role of Civil Engineers

“Designers and Builders ofThe Quality of Life…….”

Creators of the Civilised Society Environment

Providing solutions to the needs of a developing global

population

Performers (on a world stage) as strategic thinkers and

global managers

Pillars of local Economies

Creating and maintaining complex infrastructure in

wealth creation

Subject Organization

Rock MechanicsRock Mechanics

FoundationsFoundations Retaining StructuresRetaining Structures Seepage/Slopes/DamsSeepage/Slopes/Dams

Soil MechanicsSoil Mechanics

GeomechanicsGeomechanics EnvironmentEnvironment

Geotechnical EngineeringGeotechnical Engineering

Challenge

Effect is morepronounced

Environmental GeomechanicsGenesis

Population ExplosionIndustrializationSluggish and “Don’t bother approach”IgnoranceHuman Greed

Is a Philosophy put in practice to deal with

under-ground “environment” & Problems associated with it

Combination/Blend of Geotechnical Engg. and Environmental Engg.

Average water table

Waste Disposal Strategies

Above ground storage

No protection Protected by geologic materials

wet period

average

dry period

Backfill

Shallow trench burial

Engineered Backfill geological materials.

Deep Disposal

with backfill Protected by high-

retardation geologic material

Average water table

Backfill

Waste

Large boreholes 10 to 20 meters deep

Protective Geologic material

Backfillmaterial

Waste

deposits

Unfrcturedclayey

Issues areIssues are

• Ascertaining the quality of air, water, and land resources;• Transport, use, and disposal of hazardous wastes• water and wastewater treatment, and reuse.

• Analysis and design of foundation systems, seepage control, earth dams and water resource structures, response of foundations and embankments to the ENVIRONMENTAL ACTIVITIES

Man made Natural earthquakes/(& to some extent other natural calamities).

industrialization/population explosion

SCOPE of Environmental Geomechanics

Protection of ground water aquifers from contamination(Containment)(Containment)

Assessment of pollutants being discharged on/in the soil deposits (Disposal/Handling/storage)(Disposal/Handling/storage)

Process by which the pollutants travel in geo-environment (Contaminant Transport)(Contaminant Transport)

Methods of cleaning the contaminated sites(Remediation)(Remediation)

Methods of creating “Value added” products(Recycling & Reuse)(Recycling & Reuse)

Specific Studies on

• Hazardous wastes• Physical, Chemical, Mineralogical, Electrical and Thermal characterization• Geoenvironmental hazards:

Natural and man madeRecycle and Reuse of Industrial waste(s)

• Role of Geotechnical engineering in environmental protection• Surface and subsurface contamination• Characterization of contaminated ground• Geoenvironmental site investigation• Site assessment technologies

 

 

 

 

 

 

 

Soil-Water-Environment Interaction

The Natural Environment

Geomicrobiosphere Man Made Environment

The Particle Energy Field Theory

Environmental Geotechnical

Problems

Understanding of Soil response to

Environments

(Short & long-term)

Requires knowledge from other DisciplinesBacteriology Biology Chemical Engg.

Climatology Geohydrology Geophysics

Geochemistry Hydrogeology Mechanics

Microgeology Physico-Chemistry Soil Science

Soil Engineering Toxicology

 

 

 

 

 

 

 

The Natural Environment

AtmosphereBiosphere

Oxygen CycleNitrogen CycleCarbon Cycle

HydrosphereLithosphere

Geomicrobiosphere Ecosphere

The Cycle of Nature

Man-made Environment

Agricultural wastes

Human and Animal wastes

Industrial wastes

Mine wastes……Acid mine waste (due to oxidation of Iron Sulphide (FeS2) or Pyrites to H2SO4)

Nuclear wastes

Construction Effects (Blasting/Dewatering/debris…)

Solid Liquid

 

 

 

 

 

 

 

Soil Response to Environments

Soil structures (on/in/with)Pore fluid characteristicsSoil-heatSoil-ChemicalSoil BacteriaSoil-RootSoil-ElectricalSoil-Liquid (water)

Basic concepts of Analysis

Most geotechnical projects occur in nature

Long-term phenomenon

Soil is more sensitive and susceptible to environment than any other construction material

Loading may greatly affect soil properties but not the only Parameter to be considered

Think of other factors:

HeatMoisture (wet/Dry)Pollution intrusion

Classical Soil Mechanics: Some flaws

Specific gravity and Atterberg limits are constant

Void ratio and porosity as indicators of soil deformation

Water in the soil mass is mainly gravity water(need to consider Environmental water)

Flow through a soil mass is only due to hydrostatic potential(need to consider thermal/electrical/magnetic/chemical effects)

Constitutive models are arbitrarily chosen.

Stress-strain relationship

Soil Classification: Controlling Parameters

Grain-size distributionSoil Consistency (moisture content)LLPLPI

Present scenario

(Parameters)

Proposed scenario

(Parameters)

% Passing #200 SieveSpecific surfacepH in pore fluidIon-exchange capacityAbsorption & adsorptionThermal properties (Conductivity, diffusivity, specific heat)Dielectric constant (Electrical properties)

Environmental Geomechanics Laboratory @ IIT Bombay

www.civil.iitb.ac.in/~dns

You are most welcome to Visit the laboratoryYou are most welcome to Visit the laboratory