nisee

National Information Service for Earthquake Engineering
University of California, Berkeley

 Damage Due to Liquefaction
 Earthquake 
Engineering
 Contents
 Ground Failure
 Ground Shaking
 Solutions
 Foundation
 Superstructure
 Construction
 Research

      During an earthquake, significant damage can result due to instability of the soil in the area affected by internal seismic waves.  The soil response depends on the mechanical characteristics of the soil layers, the depth of the water table and the intensities and duration of the ground shaking.  If the soil consists of deposits of loose granular materials it may be compacted by the ground vibrations induced by the earthquake, resulting in large settlement and differential settlements of the ground surface. This compaction of the soil may result in the development of excess hydrostatic pore water pressures of sufficient magnitude to cause liquefaction of the soil, resulting in settlement, tilting and rupture of structures as illustrated in Slides J12-J18.

THE M = 8.6 ALASKA EARTHQUAKE
(March 27, 1964)

      This earthquake occurred in the Aleutian Alaska arc which is an important segment of the circum-Pacific belt of earthquakes where the Pacific Plate plunges downward and northward.  About 6 percent of the large shallow earthquakes of the world occur in this region.  During the 1964 Alaskan earthquake, the first slip occurred at a depth of approximately 30 kilometers under northern Prince William Sound, and the rupture of the rocks extended horizontally for 800 kilometers roughly parallel to the Aleutian trench.  It has been estimated that about 200,000 square kilometers of the crust were deformed in this earthquake.  It was the greatest area of vertical displacement ever measured in earthquake history.  The vertical fault displacement in place on Montague Island amounted to 6 meters [7, 8]
      This earthquake which was recorded to have an intensity of M = 8.6 resulted in approximately 130 deaths and property damage estimated in 300 million dollars (1967 dollars). Of the 130 deaths, only 9 persons died from the effects of ground shaking: approximately 120 persons were drowned by very large ‘tidal waves’ (tsunami) produced by the sudden upward movement of the Alaskan sea floor along the rupturing fault.  The greatest damage caused by the earthquake resulted from soil slides and from waves generated by those slides that occurred under water.  The most spectacular landslide involving about 9.6 million cubic meters of soil took place at the Turnagain Height area of Anchorage, Alaska.  The slide extended approximately 1600 meters and extended inland an average of 280 meters.  The Turnagain Height slide was a laterally spreading landslide caused by the combination of dynamic stresses and induced high pore water pressure in layers of soft clay and sands underlying the sliding mass.  Within the slide area the original ground surface was completely devastated by displacements that broke up the ground into a complex system of ridges and depressions as illustrated in Slide J12.  In the depressed areas, the ground dropped an average of 11 meters during the sliding.  Houses in the area, some of which moved laterally as much as 150 or 180 meters, were completely destroyed.

J12.  Displacement and tilting of houses due to soil liquefaction in the Turnagain Height area of Anchorage during the 1964 Alaska Earthquake [7, 8].

 

THE M = 7.5 NIIGATA, JAPAN, EARTHQUAKE
(June 16, 1964)

J13.  Tilting of apartment buildings at Kawagishi-Cho, Niigata, produced by liquefaction of the soil during the 1964 Niigata Earthquake [9].

J14.  Collapse of the super- structure of the Showa Bridge by falling off its piers; 1964 Niigata Earthquake [9].

      The Niigata Earthquake resulted in dramatic damage due to liquefaction of the sand deposits in the low-lying areas of Niigata City.  In and around this city, the soils consist of recently reclaimed land and young sedimentary deposits having low density and shallow ground water table.  At the time of this earthquake, there were approximately 1500 reinforced concrete buildings in Niigata City.  About 310 of these buildings were damaged, of which approximately 200 settled or tilted rigidly without appreciable damage to the superstructure as is illustrated in Slide J13.  It should be noted that the damaged concrete buildings were built on very shallow foundations or friction piles in loose soil.  Similar concrete buildings founded on piles bearing on firm strata at a depth of 20 meter did not suffer damage.
      Civil engineering structures which were damaged by the Niigata Earthquake included port and harbor facilities, water supply systems, railroads, roads, bridges, airport, power facilities and agricultural facilities.  The main reason for these failures was ground failure, particularly the liquefaction of the ground in Niigata City which was below sea level as a result of ground subsidence.  Slide J14 illustrates the collapse of the superstructure of the Showa Bridge which was caused by the movement of the pier foundations.

THE M = 7.4 CAUCETE, ARGENTINA, EARTHQUAKE
(November 23, 1977)

      Approximately 65 persons were killed, 284 injured, and between 20,000 and 40,000 were left homeless by this earthquake.  No surface faulting was detected, and the most notable effect of this earthquake was the extensive area of liquefaction (possibly thousands of square kilometers).  Some of the effects of this liquefaction are illustrated in Slides15 through J17.

J15.  Linear fissure in a soccer field in the town of Caucete caused by the liquefaction that occurred in the 1977 Caucete Earthquake.

 

J16.  One-story masonry house in a main housing development in the town of Caucete, damaged due to differential settlement caused by liquefaction in the 1977 Caucete Earthquake.

J17.  Damaged ground floor reinforced concrete slab of the house shown in the preceding slide.  Mud (sand) covers part of the floor.

      The most dramatic effects of the liquefaction were observed in the town of Caucete, located approximately 70 kilometers from the epicenter.  In this area not only were large amounts of sand boils observed but large linear and arcuate fissures were induced.  Slide J15 illustrates one of the fissures that appeared in a soccer field in Caucete after the soil was compacted and covered by more that 0.25 meters of water.  In some places this fissure was 1 meter wide and more than 2 meters deep.  Houses that straddled these fissures were damaged as illustrated in Slides J16 and J17.  In some of these houses, the ground floor slabs were covered by more than 10 centimeters of sandy mud.  There were places where it was estimated that the subsidence that developed as a consequence of compaction during the liquefaction reached values of approximately 1 meter.

THE M = 7.7 NIHONKAI-CHUBU, JAPAN, EARTHQUAKE [10, 11]
(May 26, 1983)

      In spite of the fact that the epicenter of this earthquake was located approximately 100 kilometers offshore from Akita City, the seismic disturbance and the tsunami of this earthquake resulted in significant damage to coastal areas along the Japan Sea.  The maximum ground acceleration recorded was 0.20g (200 gals) and it has been estimated that in one area the acceleration exceeded 0.30g (300 gals).  However, the duration was about 60 seconds, about twice as long as those recorded previously.  There were 104 deaths and 325 injuries.  5100 houses were either fully or partially destroyed, and significant damage was done to civil engineering structures, particularly port and harbor facilities.  Most of the deaths (100 of the 104) were caused by the tsunami, and most of the damage to houses and structures was cause by liquefaction, as illustrated in Slides J18, J42 and J43.

J18.  Tilting of a school flag pole due to ground failure caused by liquefaction during the 1983 Nihonkai-Chubu Earthquake.

      Slide J18 illustrates the ground failure cause by liquefaction.  The school that was built on this site and was supported on piles embedded down to a layer of soil offering large penetration resistance did not suffer structural damage in spite of the fact that as much as 0.5 meters subsidence developed at this site as a consequence of compaction as illustrated in Slides J44 and J45Slide J46 shows the inside of the gymnasium (the basketball court) of this school that was intact in spite of the fact that the surrounding soil had subsided more than 0.30 meters.  This illustrates and emphasizes the importance of proper foundations in earthquake-resistant design as will be discussed and illustrated later.

      Slide J43 show two large cranes at the Nakajima Wharf in the Akita Port.  One of the cranes (furthest from the camera) was derailed and its supports failed.  Due to liquefaction of sand backfill the aprons (slab or pavement) cracked and collapsed.

CONCLUDING REMARKS

Avoiding serious damage is the main goal of earthquake-resistant construction.  The seismic-resistant design provisions of most codes are concerned only with assuring an effective design and construction of structures against damage that might be induced by the vibratory response of the structure to the shaking introduced at their foundation by the ground.  Slides J2 through J18 illustrate the importance of damage caused by ground failure and the need for an analysis of the suitability of the site selected for the structure before its design and construction.  While in certain cases of ground failure it is possible to design safe structures by proper design of their foundation, in other cases the only rational solution is a change of site.  These are areas where the potential for severe ground failure is so high that government authorities should prohibit the building structures.

Damage Due to Surface Faulting Click here for Table of Contents Damage Due to Ground Shaking

The University of California, Berkeley
Copyright 1997, The Regents of the University of California.
Structural Engineering Slide Library, W. G. Godden, Editor
Set J: Earthquake Engineering, V. V. Bertero

Site Design: Vivian Isaradharm,  Oct. 97.
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