Geotechnical Earthquake Engineering

Transcription

1 Geotechnical Earthquake Engineering by Prof. Deepankar Choudhury Professor, Dept. of Civil Engg., Indian Institute of Technology (IIT) Bombay Powai, Mumbai , India. URL: Lecture 2 1

2 Module 1 Introduction to Geotechnical Earthquake Engineering 2

3 Effects of Earthquake Devastating effects of earthquakes due to failure of structure Earthquake never kills, but damage of structures during earthquake due to incorrect or insufficient design and constructions kills 3

4 Effects of Earthquake Devastating effects of earthquakes due to failure of soil beneath Structure is safe, but it has settled down by huge amount, due to failure of ground beneath. Buildings dilapidated because of failure of soil beneath 4

5 Effects of Earthquake Devastating effects of earthquakes due to landslides and rockslides Fig. Landslides in Sikkim during 2011 earthquake Fig. Rockslides in Sikkim at different road streches 5

6 Effects of Earthquake Tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake. Tsunami is a Japanese word with the English translation, "harbor wave ("tsu," means harbor, while "nami," means "wave ) Figures showing disasters due to Tsunami 6

7 Principal Types of Earthquake Damage Structural Caused by excessive ground shaking Strongly influenced by local soil conditions 7

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9 Ground Shaking: Shakes structures constructed on ground causing them to collapse Liquefaction: Conversion of formally stable cohesionless soils to a fluid mass, causing damage to the structures Landslides: Triggered by the vibrations Retaining structure failure: Damage of anchored wall, sheet pile, other retaining walls and sea walls Fire: Indirect result of earthquakes triggered by broken gas and power lines Tsunamis: large waves created by the instantaneous displacement of the sea floor during submarine faulting 9

10 Damage due to Earthquakes Earthquakes have varied effects, including changes in geologic features, damage to man-made structures and impact on human and animal life. Earthquake Damage depends on many factors: The size of the Earthquake The distance from the focus of the earthquake The properties of the materials at the site The nature of the structures in the area 10

11 Ground Shaking Frequency of shaking differs for different seismic waves. High frequency body waves shake low buildings more. Low frequency surface waves shake high buildings more. Intensity of shaking also depends on type of subsurface material. Unconsolidated materials amplify shaking more than rocks do. Buildings respond differently to shaking depending on construction styles, materials Wood -- more flexible, holds up well Earthen materials, unreinforced concrete -- very vulnerable to shaking. 11

12 Collapse of Buildings June 28th (Mon), :13 pm M7.1, D=0km (Fukui Earthquake, 1948) Death Toll: 3,769 Injured: 22,203 Collapse Ratio of Houses: almost 100% (The Area of South- North 20km by East- West10km of Fukui Plain) Damage to Pile-Heads of Hokuriku Haiden Building. (Shear Cracks) 12

13 Collapse of Buildings (Fukui Earthquake, 1948) Damage to the Pile Foundations of Hokuriku-Haiden Building caused by the 1948 Fukui Earthquake Settlements of the First Floor Cracks at the Column-Heads of the Second Floor and the Floor Slabs of the First Floor 13

14 Image of Bachau in Kutch region of Gujarat after earthquake 14

15 Principal Types of Earthquake Damage Liquefaction Occurs in loose, saturated sands Grain structure collapses Pore pressure increases Effective stress decreases Strength and stiffness decrease 15

16 Soil Liquefaction Termed liquefaction, the strength of the soil reduced, often dramatically, to the point where it is unable to support structures or remain stable. Fukui 1948 Earthquake, Liquefaction Failure 16

17 1964 Niigata Earthquake June 16th (Tue) 1964, 13:02pm Magnitude M=7.5 (Reference: The 1995 Great Hanshin Earthquake M=7.2, The 1923 Great Kanto Earthquake M=7.9) Death Toll: 29 Total Burnt and Collapse of Houses: 3,557 Damage: Soil Liquefaction, Bridge Collapse, Fire of Oil Storage Tanks (Fire continued 300 hours) Tokyo Olympic Games: October 10th -21st,

18 Collapsed Buildings (Kawagishicho Apartments) due to Soil Liquefaction Accelerometers: At bldg. top: 184 Gal, At bldg base: 159 Gal 340 RC Buildings were damaged in Niigata City. The damage ratio of RC building is 22%. Nigata 1964 Earthquake, Liquefaction and Bearing Failure 18

19 Nigata 1964 Earthquake, Liquefaction and Other Failures 19

20 The 1995 Great Hanshin (Kobe) Earthquake January 17th 1995 (Tue), 05:46 am Epicenter: Awaji Island, Depth: 14km Magnitude: 7.2 Death Toll 6,439, Heavy Injured 1,883, Light Injured 26,615, Missing 2 Completely Destroyed House: 93,773, Partially Destroyed: 107,008 Collapsed Bridge: 46, Collapsed or Heavily Damaged Building: 3,081 Total Monetary Loss: 96 billion US dollars 20

21 Data of Kobe 1995 Earthquake 21

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24 Sand Boil: Ground water rushing to the surface due to liquefaction Sand blow in mud flats used for salt production southwest of Kandla Port, Gujarat 24

25 Principal Types of Earthquake Damage Landslides Can occur due to liquefaction Can occur in non-liquefiable soil 25

26 Earthquake Destruction: Landslides Devastating effect of earthquake on slope stability during San Fernando 1971 earthquake Courtesy: EERC library, UC Berkeley D. Choudhury, IIT Bombay 26

27 Devastating effect of earthquake on pavement foundation during Chile 1960 earthquake Courtesy: EERC library, UC Berkeley D. Choudhury, IIT Bombay 27

28 Devastating effect of earthquake by Liquefaction induced movement during Niigata 1964 earthquake Courtesy: EERC library, UC Berkeley D. Choudhury, IIT Bombay 28

29 Devastating effect of earthquake by Liquefaction induced Bearing capacity failure during Turkey 1999 earthquake Courtesy: EERC library, UC Berkeley D. Choudhury, IIT Bombay 29

30 Lateral Spreading: Liquefaction related phenomenon Upslope portion of lateral spread at Budharmora, Gujarat 30

31 Lateral spreading in the soil beneath embankment causes the embankment to be pulled apart, producing the large crack down the center of the road. Cracked Highway, Alaska,

32 Earthquake Destruction: Retaining Structure Failure September 1999 Chi Chi Earthquake, Taiwan 32

33 Liquefied soil exerts higher pressure on retaining walls,which can cause them to tilt or slide. 33

34 Increased water pressure causes collapse of dams 34

35 Earthquake Destruction: Lifelines 35

36 Earthquake Destruction: Fire Earthquakes sometimes cause fire due to broken gas lines, contributing to the loss of life and economy. The destruction of lifelines and utilities make impossible for firefighters to reach fires started and make the situation worse eg Loma Prieta 1906 San Francisco 36

37 Earthquake Destruction: Tsunamis Tsunamis can be generated when the sea floor abruptly deforms and vertically displaces the overlying water. The water above the deformed area is displaced from its equilibrium position. Waves are formed as the displaced water mass, which acts under the influence of gravity, attempts to regain its equilibrium. Tsunami travels at a speed that is related to the water depth - hence, as the water depth decreases, the tsunami slows. The tsunami's energy flux, which is dependent on both its wave speed and wave height, remains nearly constant. Consequently, as the tsunami's speed diminishes as it travels into shallower water, its height grows. Because of this effect, a tsunami, imperceptible at sea, may grow to be several meters or more in height near the coast and can flood a vast area. 37

38 Tsunami Tsunami Movement: ~800 kmph in deep water ~350 kmph in medium depth water ~50 kmph in shallow water 38

39 Geomorphological Changes Geomorphological changes are often caused by an earthquake: e.g., movements--either vertical or horizontal-- along geological fault traces; the raising, lowering, and tilting of the ground surface with related effects on the flow of groundwater; An earthquake produces a permanent displacement across the fault. Once a fault has been produced, it is a weakness within the rock, and is the likely location for future earthquakes. After many earthquakes, the total displacement on a large fault may build up to many kilometers, and the length of the fault may propagate for hundreds of kilometers. 39

40 Year Location Deaths Magnitude 1556 China 5,30, San Francisco S. Chile 2, Alaska China 7,00, Mexico City 9, California Kobe 5, Gujarat, India 1,00, Sumatra 2,20, Pakistan 1,00, China 90, Haiti 2,22, Chile 50, List of Major Historic Earthqu akes in World 2011 Japan 1,00,

41 LIST OF SOME SIGNIFICANT EARTHQUAKES IN INDIA AND ITS NEIGHBOURHOOD DATE EPICENTRE LOCATION MAGNITUDE Lat( Deg N ) Long( Deg E ) 1819 JUN KUTCH,GUJARAT JAN NEAR CACHAR, ASSAM MAY SOPOR, J&K JUN SHILLONGPLATEAU APR KANGRA, H.P JUL SRIMANGAL, ASSAM JUL DHUBRI, ASSAM JAN BIHAR-NEPALBORDER JUN ANDAMAN ISLANDS OCT ASSAM AUG ARUNACHAL PRADESH-CHINA BORDER JUL ANJAR, GUJARAT DEC KOYNA, MAHARASHTRA JAN KINNAUR, HP AUG MANIPUR-MYANMAR BORDER AUG BIHAR-NEPAL BORDER OCT UTTARKASHI, UP HILLS SEP LATUR-OSMANABAD, MAHARASHTRA MAY JABALPUR,MP MAR CHAMOLI DIST, UP JAN BHUJ, GUJARAT

42 Table: Historical strong earthquakes and damages worldwide till 2010 Date Magnitude Location Effects October 20, Lima, Peru Destroyed much of the city. July 8, Valparasio, Chile Killed about 3000 people. November 1, Lisbon, Portugal Also generated Tsunami and killed about 60,000 people and destroyed much of Lisbon. November 7, Valdivia, Chile Generated Tsunami and killed atleast 58 people in Hawaii. August 13, Africa, Peru (currently in Chile) Generated catastrophic Tsunami and kille about 25,000 people in South America. June 15, Sanriku, Japan Generated a Tsunami and killed atleast 22,000 people. January 31, Off the coast of Ecuador and Colombia. Generated Tsunami and killed atleast 500 people. Choudhury, D. (2010) in Structural Longivity. 42

43 Table (contd.): Historical strong earthquakes and damages worldwide till 2010 Date Magnitude Location Effects November 11, Chile-Argentina border August 15, Assam, India and Tibet Killed several hundred people. Killed about 780 people. May 22, Southern Chile Also generated Tsunami and killed atleast 1,716 people. March 27, Prince William Sound, Alaska December 26, Off the Indonesia Island of Sumatra February 27, Offshore Maule, Chile Also generated Tsunami and killed about 128 people. Triggered a Tsunami that killed about 226,000 people in 12 countries, including 165,700 in Indonesia and 35,400 in Sri Lanka. Generated Tsunami and number of people killed and massive damages in Chile Choudhury, D. (2010) in Structural Longivity. 43

44 Table: Worldwide largest and deadliest earthquakes during 2000 to 2010 Largest Earthquakes Date February 27, 2010 September 29, 2009 Magn it u d e Fataliti es May 12, ,587 September 12, 2007 November 15, Deadliest Earthquakes Region Date Magnitude Fatalities Region Offshore Maule, Chile Samoa Islands region Eastern Sichuan, China Southern Sumatera, Indonesia January 12, ,570 Haiti September 30, ,117 May 12, ,587 August 15, Kuril Islands May 26, ,749 Southern Sumatra, Indonesi a Eastern Sichuan, China Near the Coast of Central Peru Java, Indonesi a Choudhury, D. (2010) in Structural Longivity. 44

45 Table: Worldwide largest and deadliest earthquakes during 2000 to 2010 Largest Earthquakes Date March 28, 2005 December 26, 2004 September 25, 2003 November 3, 2002 Magni t u d e Fataliti es 8.6 1, , June 23, November 16, 2000 Deadliest Earthquakes Region Date Magnitude Fatalities Region Northern Sumatra, Indonesia Off West Coast of Northern Sumatra Hokkaido, Japan Region October 8, ,361 Pakistan December 26, ,898 December 26, , Central Alaska March 25, , Near Coast of Peru New Ireland Region, P.N.G. Off West Coast of Northern Sumatra Southeastern Iran Hindu Kush Region, Afghanist an January 26, ,023 Bhuj, India June 4, Southern Sumatera, Indonesia Choudhury, D. (2010) in Structural Longivity. 45

46 Earthquake Records (courtesy: Tohoku, Japan (2011) 46

47 Share of Earthquake Disaster in 20 th Century Walling and Mohanty (2009) 47

48 Earthquake Fatalities vs. Magnitude Hough and Bilham,

49 End of Module 1 49