Dr. P. NANJUNDASWAMYDr. P. Nanjundaswamy SJCE Mysore January 9, 2018 40 Reinforced Earth -Examples...

Reinforced Earth Structures

Dr. P. NANJUNDASWAMY

Professor of Civil Engineering

S J College of EngineeringMysore – 570 006Contact : 94492 [email protected]

Dr. P. Nanjundaswamy SJCE Mysore 2

Outline

1. Introduction

2. Applications - Examples

3. Principles and Mechanism

4. Advantages and Limitations

Dr. P. Nanjundaswamy SJCE Mysore January 9, 2018 3

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1965 1975 1985 1995 2005

0 5 11

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Evolution of total amount of Reinforced Earth built worldwide


Introduction

Use of Soil in Civil Engineering Practice

• Construction material (earth dam, embankments)

• Manufacture of bricks, tiles, earthenware

• Fill material behind retaining walls, abutments . . .

• Foundation material


Introduction….

Ground Improvement In-situ soil treatment

Stabilization chemical injection or groutingPre-compressionVibroflotationDynamic compactionElectro-osmosis

Soil reinforcementPilesStone columnsMetallic or non-metallic elements


Introduction….

Nicholson (2015)


Reinforced Earth - Examples



Before



During



After



Reconstruction of the slope of embankment using GRS-RWs having a FHR facing for a

track of bullet trains (Shinkan-Sen)



COASTAL EROSION



Geotextile as separator & filter



PavementStonebase

Soil subgrade

Topsoil

450 mm

400 mm

300 mm

Crushed stone/perforated pipe

GT

(GT Filter in Excavated Trench) (Crushed Stone & Perforated Pipe)



Tunnel Waterproofing

• many old tunnels without GMs are leaking

• white staining on surface is the “tell-tale”

• key is to use a GT and GM behind the permanent concrete surfacing

• in turn, this requires a GP drainage system



Rehabilitation


In this Course


In this Course

Basics of Reinforced Earth

General

Origin

Definition

Principles

Mechanism and Concept

Components

Advantages and Disadvantages

Application areas


In this Course . . .

Geosynthetics

Introduction and Overview

Classification

Functions

Manufacturing methods

Characteristics and Testing



Design of Reinforced Earth Structures

Retaining walls

Embankments

Earth Dams and Slopes

Foundation structures



Soil Nailing Techniques

Mechanism

Methods of Soil Nailing

Construction Sequence

Design Aspects



Geosynthetics for other applications

Filter and Drain

Landfills

Roads


References

Design with Geosynthetics

Robert M. Koerner

Fifth Edition 2005

Pearson Prentice Hall

ISBN 0-13-145415-3


References . . .An Introduction to Soil Reinforcement

and Geosynthetics

Shivakumar Babu G. L.

First Published 2005

Orient Blackswan

ISBN 978-81-737-14818


References . . .

Earth Reinforcement and Soil Structures

Colin J F P Jones

Third Edition 1996

Thomas Telford

ISBN 978-0-727-73489-1


References . . .

Geosynthetics and their applications

Edited by

Sanjay Kumar Shukla


Thomas Telford Limited

ISBN 0-7277-3117-3


References . . .

Geosynthetics in Civil EngineeringEdited by

Sarsby R. W.First Published 2007 Woodhead Publishing Ltd. and CRC Press

ISBN 978-1-85573-607-8


References . . .

Fundamentals of Geosynthetic Engineering

Sanjay Kumar ShuklaJian-Hua Yin


Taylor & Francis Group

ISBN 978-0-415-39444-4


References . . .• Reinforced Soil and its Engineering

ApplicationsSwami SaranI. K. International Pvt. Ltd., New Delhi, 2006

• Engineering with GeosyntheticsEd. G.V.V. Rao & G.V.S.S. RajuTMH, India, 1996


References . . .

Reinforced Earth and Geosynthetics

My Notes

Revised 2014


Concept, Principles and Mechanism


Definition

Composite material formed byembedding reinforcing material in asoil fill.

Reinforcing elements interact with soilthrough friction and/or adhesion andable to resist tensile stresses.


Principles


Principles….


Concept

Frictional earth-reinforcement interaction

Interaction between soil and reinforcement- a sort of restraint on the soil mass

• Equivalent confining stress concept

• Pseudo-cohesion concept

Principles….


Principles….

Equivalent confining stress conceptσ1

σ3σ3

σ1

Unreinforced Soil

σ3σ3

σ1+Δσ1

Reinforced Soil

Δσ3

Δσ3

Δσ3

Δσ3

σ1+Δσ1


Principles….

σ1 Δσ1

σ3 Δσ3

σ

Ø

Reinforced Soil

Unreinforced Soil

Equivalent Confining Stress

Equivalent confining stress concept

q


Principles….

Pseudo-cohesion concept

σ1

σ3σ3

σ1

Unreinforced Soil

σ3σ3

σ1+Δσ1

Reinforced Soil

σ1+Δσ1

Ø only C and Ø


Principles….

σ1 Δσ1

σ3

σ

Ø

Reinforced Soil

Unreinforced Soil

Pseudo-cohesion concept

q

Ø

c


Mechanism

Stress on soil mass – strain in soil – transmit tensile load to

reinforcement

Tensile fore is not constant

– exhibits peaks

Line of maximum tensile force – potential failure surface


Advantages

• Cost effective

• Ease and rapidity of construction

Std prefabricated elements

• Adaptability to various slopes & soil conditions

mid size construction equipment

• Flexibility

• Aesthetic


Disadvantages

• Non availability of suitable fill material

• Suitable design criteriaCorrosion, deterioration and degradation

• Shared responsibilityMaterial suppliers, designers, contractors and engineers

• Design and construction practiceStandardization of specifications, and contracting practices

Dr. P. Nanjundaswamy SJCE Mysore 71

Thank you

Dr. P. NANJUNDASWAMYDr. P. Nanjundaswamy SJCE Mysore January 9, 2018 40 Reinforced Earth -Examples...

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