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Instructor: JM Albaine

Introduction & Overview Lecture

SPRING 2013

Ground Rules, Syllabus etc.

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"As a designer, realize that what your professors taught you is onlyabout 1%(maybe 0.9% for a B.S. and 1.1% for a Ph.D.) of whatyou really need to know.

The good news is that you have about 40 years to learn the rest"

INTRODUCTION TO GEOTECHNICAL ENGINNERING

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Process of solving problems that involve safe and economical transfer of structural loads to the ground.

Interface or transition elements between (super) structure and ground.

Transfer/transmit loads from structure to underlying material (soil/rock).

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Geotechnical EngineeringSoil MechanicsRock MechanicsEngineering Geology

Foundation DesignSlope Stability AnalysisRetaining Structure Design

Landfill DesignWaste ContainmentSubsurface Remediation and Cleanup

Basic Sciences

Traditional Applications

Geo-Environmental Applications

Types of Foundations

• Shallow Foundations– Footings– Rafts

• Deep Foundations– Piles– Caissons

Built Near Ground Surface

(if near surface ground is competent)

Penetrate Deep into Ground

(if near surface is notcompetent)

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Shallow Foundations

• Combined FootingIsolated Footing

Shallow Foundations

• Strip FootingStrap Footing

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Shallow Foundations

Raft/Mat Foundation

Deep Foundations

• Piles

Single Pile Pile Group Piled Raft/Mat

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Shallow and Deep Foundations

Column

Single Pile

Pile Group

Pile Cap

Building

Beam

Ground Surfac

Sequence of Activities in a Foundation Problem

Global Scale1. Owner/Developer Acquires Site2. Owner Hires Architects/Consultants3. Consultant Hires Specialty

Contractors/Consultants4. Planning, Design, Construction, Testing5. Monitoring/Performance Evaluation

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Scale of Foundation Engineering

Problem Identification

(say, a Hotel or a Football Stadium)

Information Collection• Loads• Ground Conditions

Information ProcessingSelection of Foundation Type(s), Design Method(s), Construction Method(s) etc.

Execution• Design

• Construction

Evaluation• Load Test on

Foundation(s)• Performance

Monitoring

Corrective Measure

(if required)Foundation Retrofitting

Foundation Decisions

• Choice of Foundation Type(s)• Choice of Design Parameters and Design

Method(s)• Choice of Method(s) of Construction and

Testing• Choice of Methods of Monitoring

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Factors Governing Selection of Foundation Type

• Feasibility• E.g., Large load or Soft Soil typically requires Deep Foundations

• Constructability• E.g., Driven Piles cannot be used for a Site Filled with Boulder

• Availability of Construction Equipments• E.g., If Site is Perfect for Driven Piles but Pile Driving Equipment is not

Locally Available, then Bored Piles have to be Constructed

• Project Specific Factors• E.g., Tight Deadlines may preclude certain Foundation Types; If

Lowering of Water Table is not permitted then Shallow Foundations have to be avoided

• Environmental Factors• E.g., Pile Driving may not be possible if Adjacent Structures are

Damage-prone

Foundation Design ApproachesWorking/Allowable Stress Design (WSD/ASD)

• Factor of Safety Design• Calculate Ultimate Foundation Capacity (or Resistance)

Cultimate• Estimate Working Load Lworking• Decide on required Factor of Safety F• Design such that Cultimate/F = Callowable ≥ Lworking

Limit State Design (LSD)Load and Resistance Factor Design (one type of LSD)

Reliability Based Design (RBD)• Probabilistic Estimation of Foundation Capacity and

Applied Loads – Accounts for “Uncertainty”• Probabilistic Estimation of Safety Against Potential

“Failures”

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Limit States• Serviceability Limit States – set of unacceptable

conditions related to Performance, e.g., excessive settlement or tilt• Excessive Settlement of a Building Leading to

Malfunctioning of Service Lines• Excessive Uneven Settlement Leading to Building

Cracks

• Ultimate Limit States – set of unacceptable conditions related to Safety/Danger, e.g., collapse• Bearing Capacity Failure leading to Plunging of

Foundation• Excessive Settlement of Building leading to Structural

Collapse

Trends in Geotechnical Design

• Traditional Approach – Working Stress Design (WSD)

• Current Trend – Load and Resistance Factor Design (LRFD)

Load and Resistance Factor Design• Special Type of Limit State Design (LSD) • Borrows Concepts from Reliability Based Design (RBD)

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Geotechnical Engineering is a Science but its practice an Art

Structural Engineering is the art and science of molding materials we donot fully understand into shapes we cannot precisely analyze to resistforces we cannot accurately predict, all in such a way that the societyat large is given no reason to suspect the extent of our ignorance.

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