Earthquake Resistant Design of Geotechnical Structures ...

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by

Deepankar Choudhury, FNASc

Professor, Dept. of Civil Engg., IIT Bombay, Mumbai, India.Also, Adjunct Professor, Academy of CSIR (AcSIR), India.

(connected to CSIR-CBRI Roorkee)

Earthquake Resistant Design of Geotechnical Structures –

Theory and Practice

Institute Award Lecture at IIT Bombay on 1st November, 2017

Deepankar Choudhury, IIT Bombay, India

* PhD Scholars : Dr. Sanjay Nimbalkar, Dr. Syed Ahmad, Dr.Purnanand Savoikar, Dr. V. S. Phanikanth, Dr. Sumedh Mhaske, Dr.Jaykumar Shukla, Dr. Sunil Rangari, Dr. Amey Katdare, Dr. RanjanKumar, Dr. Sarika Desai, Dr. Nisha Naik, Dr. Reshma Raskar-Phule, Dr.Kaustav Chatterjee, Dr. Anindya Pain, Dr. Shylamoni, Dr. B. G. Rajesh.

(Present) Mr. Ashutosh Kumar Mr. Milind Patil, Ms. Sujatha Manoj & others.

* Collaborators : Prof. Rolf Katzenbach, Germany; Prof. HarryPoulos, Australia, Dr. G. R. Reddy, Prof. D. L. Shah, Mr. R. Roy, India.

* Funding Agencies: British Petroleum, UK; Alexander vonHumboldt Foundation, Germany; ThyssenKrupp Pvt. Ltd., NPCIL,India, Chemie-Tech. Pvt. Ltd., India.

* Society/Code Committee: ISSMGE TC 212 - Deep Foundations,International Building Code (IBC-1803), USA.

Acknowledgements

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D. Choudhury, IIT Bombay, India

Share of Earthquake Disaster in 20th CenturyRef: Walling and Mohanty (2009)

Why Earthquake Study is Important ?

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Damages due to Geotechnical Issues during Earthquake

D. Choudhury, IIT Bombay 4

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5D. Choudhury, IIT Bombay, India

Failure of Retaining Walls Retaining walls may fail during an earthquake, if they are

not designed to resist additional destabilizing earthquake forces

Development of New Pseudo-Dynamic Approach

Soil amplification is considered.

Frequency of earthquake excitation is considered.

Time duration of earthquake is considered.

Phase differences between different waves can be considered.

Amplitude of equivalent PGA can be considered.

Considers shear and primary wave velocities traveling during earthquake.

Advantages

Pseudo-Dynamic Approach by Steedman and Zeng (1990) and Choudhury and Nimbalkar (2005)

Choudhury, D. and Nimbalkar, S. (2005), in Geotechnique, 55(10), 949-953.

ah(z, t) = ah sin [{t – (H – z)/Vs}]

av(z, t) = av sin [{t – (H – z)/Vp}]

Pseudo-Static Approach by Mononobe-Okabe (1929)

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The coefficient of seismic passive resistance (Kpe) is given by,

The seismic passive earth pressure distribution is given by,

where and


Typical non-linear variation of seismic active earth pressure

Choudhury and Nimbalkar (2006), in Geotechnical and Geological Engineering, 24(5), 1103-1113.

ah(z, t) = {1 + (H – z).(fa – 1)/H}ah sin [ {t – (H – z)/Vs}]

Effect of soil amplification onseismic active earth pressure

Nimbalkar and Choudhury (2008),in Journal of Earthquake and Tsunami, 2(1), 33-52.

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Validation of Analytical Results of Pseudo-DynamicApproach with Dynamic Centrifuge Test Results

Dynamic moment increment,

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Plays vital role in the safety of port

and harbor structures

Damages to sea walls in Tohuku

earthquake 2011 is extensive


Failure of Waterfront Retaining Structures

Kobe Earthquake, 1995(www.ce.washington.edu)

Bhuj Earthquake, 2001(Madabhushi and Haigh ,2005)

Tohuku Earthquake, 2011(www.impactfoecasting.com)

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D. Choudhury, IIT Bombay

Design Solutions for Waterfront Retaining Walls (Sea Walls) subjected to both Earthquake and Tsunami

(1) For Tsunami attacking the wall (passive case)

(a) Against Sliding mode of failure(b) Against Overturning mode of failure

(2) For Tsunami receding away from wall (active case)

(a) Against Sliding mode of failure(b) Against Overturning mode of failure


Tsunami wave recedes back – Active state

Forces acting on the waterfront retaining wall

Choudhury, D. and Ahmad, S. M. (2007) in Ocean Engineering, Elsevier, 34(14-15), 1947-1954.

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Design solutions proposed by Choudhury and Ahmad (2007)

Factor of Safety against Sliding Failure:

Factor of Safety against Overturning Failure:

Choudhury, D. and Ahmad, S. M. (2007) in Ocean Engineering, Elsevier, 34(14-15), 1947-1954.

Tsunami wave attack : Passive Case

Choudhury, D. and Ahmad, S. M. (2007) in Applied Ocean Research, Elsevier, 29, 37-44.

CRATER (2006)

Combined effects of tsunami and earthquakeOn rigid waterfront retaining wall

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Passive Case (Results)

Choudhury, D. and Ahmad, S. M. (2007) in Applied Ocean Research, Elsevier, 29, 37-44.

Factor of safety against sliding

Factor of safety against overturning

Comparison of Results

Choudhury and Ahmad (2008) in Jl. of Waterway, Port, Coastal and Ocean Engg., ASCE, 134, 252-260.

Choudhury and Ahmad (2008)

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Various Deep Foundation Systems

8 November 2017

Deep Foundations

Foundations Deep excavations Tunnels

Katzenbach, Choudhury and Chang (2013) in TC 212 General Report of 18ICSMGE, Paris

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Glory of Deep Foundations

8 November 2017

Burj Khalifa, Dubai

Poulos and Bunce (2008)

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Introduction - Super Tall Towers

ongoing construction boom - supertall towers of 200 to 600 m

- 800 to 1000m tall vertical cities

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Future of Deep Foundations

8 November 2017

Proposed Kingdom Tower, 1001 m, Jeddah

Katzenbach, Choudhury and Chang (2013)

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Foundation system of World’s Tallest (1001m) Building at Jeddah

Foundation raft (4.5 m thick)

Piles (45 m long)

Piles (65 m long)

Katzenbach et al. (2013)

Concept of Combined Pile-Raft Foundation (CPRF)

Skin friction Pile

Foundations

Raft foundation Deep (Pile) foundation Combined Pile-Raft Foundation (CPRF)

Base pressure

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INTRODUCTION to CPRF

Piled raft foundation(also called composite foundation)solve:

1. Settlement – through interaction and load sharing.2. Differential settlement – raft provide stiffness

against load.3. Economical - reducing number of piles.

Poulos et al. (2001) has examined a number ofidealized soil profiles, and found that soil profilesconsisting of relatively stiff clays and relativelydense sands may be favourable for piled raftfoundation.

Construction: 1988 - 1990

Foundation: CPRF

Height: 256 m Messeturm tower, Germany

(Katzenbach et al. 2005)23

Accomplished: CPRF of 64 piles (laverage = 30 m)

Costs of pile production: 64 piles of 30 m at 780 US$/m 1.5 Mio. US$

Pile foundation: 316 piles (l = 30 m)

Costs of pile production: 316 piles of 30 m at 780 US$/m 7.4 Mio. US$

Savings in costs of pile production 5.9 Mio. US$

Comparison of costs for the piles

Messeturm · Frankfurt am Main, Germany

Katzenbach and Choudhury (2011)

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International Design Guideline for CPRF –by ISSMGE TC 212 – Deep Foundations (2013)

8 November 2017Eds. Katzenbach and Choudhury (2013)

dydxy,x,s)s(R k,raft

m

1jk,raftj,k,pilek,tot sRsRsR

sRsRsR j,k,sj,k,bj,k,pile

Total resistance of the CPRF:

Pile resistance:

Raft resistance:

Bearing concept of a Combined Pile-Raft Foundation (CPRF)

Katzenbach and Choudhury (2013)

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2727

Some of the failures of structures supported on Pile Foundation due to Earthquakes :

(a) Piled “Million Dollar” bridge after 1964 Alaska earthquake (USA);

(b) Piled “Showa Bridge” after 1964 Niigata earthquake (JAPAN);

(c) Piled tanks after 1995 Kobe earthquake (JAPAN)

[photo courtesy NISEE].


Seismic Zonation Map of India as per IS 1893: 2002 / 2016, Part I & III

Zone DBEII 0.10gIII 0.20gIV 0.25gV 0.40g

• Only 3 types of soil!!!Soft soil, Medium

soil, Hard rock• Characterization of Soil Based on SPT ‘N’ Value, irrespective of soil type !!

• Very little DYNAMICS (for soil characterization) is involved!!!

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Soil Classification for Seismic Design in USA (NEHRP)

Choudhury (2010) in Structural Longivity, 3(2), 155-170.

Dr. Deepankar Choudhury, IIT Bombay

Soil Classification as per Eurocode 8 (2003)

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Dynamic Design Parameters

Characteristic stiffness-strain behavior of soil with ranges for typical geotechnical structures and different test (Atkinson, 2004)

• Stiffness parameter

• Damping Parameters

• Poisson's ratio of material

• Density of material

• Stiffness Parameters required at low shear strains

• The small-strain shear modulus (Gmaxor G0) is typically associated with strains on the order of 10-3%

Pile Foundation under Earthquake

Condition – Soil Liquefaction

Steps of Design for Mumbai, India


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Seismic zonation map of India [as per IS 1893 – Part I (2002)] with highlight on Mumbai city (zone III), which was originated from

seven islands


Typical soil profile for Mumbai city[Mhaske and Choudhury, 2011, GSP, ASCE]

Influence of Local Soil Conditions on Seismic Response of Foundations

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Preparation of Seismic Liquefaction Hazard Map


Soil liquefaction at Kandla Port during 2001 Bhuj earthquake

Liquefaction Hazard Map of Mumbai City for Mw = 7.5

36Mhaske and Choudhury (2010) in Journal of Applied Geophysics, Elsevier, Vol. 70(3), 216-225.

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LIQUEFACTION RISK MAP for Mumbai(Phule and Choudhury, 2017)

Risk Index (RI) = Hazard (PL or PC) x Exposure (EVo) x Vulnerability (VIo)

Liquefaction risk map of Mumbai city for transportation Infrastructure for Mw of 6.5 at amax of 0.3g

Most of the wards of Mumbai city have areas subjected to liquefaction risk index of 0.25

to 0.75 while ward A, F/N and G/N have areas with liquefaction risk of 0.75 to 1.0

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EQUIVALENT-LINEAR and NON-LINEAR GROUND RESPONSE ANALYSIS FOR MUMBAI

Mangalwadi site near Girgaon (MBH#1, MBH#2);

Walkeswar site (WBH#1, WBH#2) ; and

BJ Marg near Pandhari Chawl site (BBH#1, BBH#2 & BBH#3)

Equivalent-Linear and Non-Linear Ground response Analysis for some typical Mumbai Soil sites:

[Phanikanth, Choudhury and Reddy (2011), Geotech. and Geological Engg.,]

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Acceleration-time history of2001 Bhuj earthquake

Acceleration-timehistory of 1989 LomaPrieta earthquake

Similarly 1989 Loma Gilory earthquake (MHA = 0.442g and Tm = 0.391s, and 1995 Kobe earthquake (MHA = 0.834g and Tm = 0.641s) motions are used

Input Earthquake Motions considered in present study

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NONLINEAR GROUND RESPONSE ANALYSIS

Dividing the soil layer into ‘N’ sub layers and by finite difference

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ii+1

N+1

z

x

ρsi, Vsi


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Acceleration response spectra at ground level with 5% damping for soil site MBH#1 at Mumbai under various earthquake motions[Phanikanth, Choudhury and Reddy (2011), Geotech. and Geological Engg.,]


Typical soil amplification for earthquake acceleration at various soil sites in Mumbai under different earthquake motions[Phanikanth, Choudhury and Reddy (2011), Geotech. and Geological Engg.,]


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Piles in liquefying soil under lateral loads:

Force method

Non-liquefiable layer

Non Liquefiable layer

HNL

Liquefiable layer

qL =30% of over burden pressure Pressure

qNL = Passive earthPressure

HL

JRA (1996, 2005): Idealisation for pile design in liquefying soils


Two major effects of earthquake on pile foundations: (i) Inertial and (ii) Kinematic

Governing Equations for solving the basic differential equation of laterally loaded pile in liquefied zone is given below:

y = lateral displacement of pile; z = depth from ground; EI = flexural rigidity of pile.

Sf is scaling factor varying from 0.001 to 0.01 (Ishihara and Cubrinovski,1998) as compared to normal soil condition where there is no liquefaction .

Tokimatsu et al. (1998)

[Phanikanth et al. 2013]


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Bending moment in non liquefied and liquefied soil for free headed single pile with floating tip in Mumbai [Phanikanth et al. (2013), Int. Jl. of Geomech., ASCE,]


Dr. Deepankar Choudhury, IIT Bombay, India

For More Details,

(1) New Text Book (2016)

(2) Online NPTEL Video Course:

“Soil Dynamics” and“Geotechnical EarthquakeEngineering” – free in YouTube

http://www.nptel.iitm.ac.in/courses/105101134/

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• Piles have to be set directly under the load of the superstructure. Earthquake study is a must for foundation design.

• The centre of the pile group should be under the center of the loads.

• Few long piles are better than many short piles.

• The length of the piles has to be adapted to the loads. At the edge and the corners of the raft shorter piles and in the inner part of the raft longer piles are recommended.

• Optimum of the CPRF-coefficient: αCPRF = 0.5 … 0.7

Recommendations for the design

, ,1

,

( )

( )

m

pile k jj

CPRFtot k

R s

R s

CPRF coefficient:

Towards Building of Earthquake Resistant Geotechnical Structures

47Dr. Deepankar Choudhury, IIT Bombay

Contact Email: [email protected]

[email protected]

Homepage: http://www.civil.iitb.ac.in/~dc/ 48

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