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Japan Earthquake/Tsunami Reconnaissance Team 2 -- Days 5 and 6

Liquefaction, Shifting Evident North of Tokyo

A team from the Embankment, Dams and Slopes (EDS) Committee of the Geo-Institute arrived in Japan on April 23 for a one-week engineering reconnaissance of the region affected by the Tohoku Japan earthquake. The three-person team is led by Joseph Wartman, Ph.D., P.E., M.ASCE, of the University of Washington, and includes Binod Tiwari, M.ASCE, of California State University, Fullerton, and Daniel E. Pradel, Ph.D., P.E., D.GE, F.ASCE, of Praad Geotechnical Inc. and the University of California, Los Angeles. The EDS/GI team is being hosted by Professor Keizo Ugai, president of the Japanese Landslide Society and an instructor at Gunma University. The team is also working with the Japanese Geotechnical Society. Team members will be posting updates to the ASCE web site throughout the week. 

Read each day's entries:
Days 1 and 2  |  Days 3 and 4  |  Days 5 and 6 

Days 5 and 6 -- Thursday, April 28 and Friday, April 29

Report by Daniel Pradel 

Pradel with liquefaction settlement
April 27, the GI/EDS team was split into two groups in order to cover more terrain, since the region that experienced strong ground shaking on March 11 is enormous.  While Joseph Wartman and Binod Tiwari were visiting sites around Sendai, I was visiting levees and embankments in the Tokyo bay and in the Kanto plain, north of Tokyo. The visits were organized by Professors Ishihara of Chuo University and Tsukamoto of the Science University of Tokyo. Our Japanese hosts were extraordinarily helpful and gracious. The visits provided a unique opportunity to witness the widespread effects of liquefaction on levees, embankments, retaining walls and residences.

Liquefaction-caused crack 

Yesterday, I visited sites along Tokyo Bay in and around Makuhari, in Chiba prefecture. Damage from liquefaction including lateral spread, post-liquefaction settlement, and retaining wall failures were obvious along river embankments and canals. Although, settlement often exceeded 30 centimeters (about one foot), most structures did not appear to have experienced structural distress.

Warped canal wall
Today, I visited several levees that were affected by liquefaction along the Tone River. Although extensive emergency repairs have and are being made in preparation for the rainy season, which begins next month, numerous sand boils were still visible along the toe of many levees on both the upstream and downstream faces. Liquefaction resulted in lateral spread which created deep fissures between the Tone River and the toe of levees.  At bridge abutments evidence of lateral spread exceeding 1.5 meters (five feet) was visible. Additionally, deep cracks up to 30 centimeters wide  were still present on the upstream face (the riverside slope) of several levees. Several failures along the steeper downstream face were also visible, including one that damaged structures along the toe of the levee.

Sand boils
I also visited Fuda, a small village along the Tone River, where extensive liquefaction-related damage was reported. Evidence of subsidence exceeding 45 centimeters (1.5 feet) was visible at several locations. Although settlement was extensive, most structures appear to have experienced only structural distress.

Shifted residence in Fuda 

Days 1 and 2  |  Days 3 and 4  |  Days 5 and 6  

 

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