Liquefaction-induced road embankment failures

The intensive and long-lasting seismic shaking during the 2011 great east Japan earthquake left enormous amounts of scars on the ground surfaces and inflicted damage to private houses, buildings and constructed infrastructure. Many of the ground failures were associated with subsurface soil liquefaction. Forensic field investigations were conducted at one of the illustrative sites with the help of field penetration tests. The site is a road embankment over a reclaimed soil deposit located at the foot of a steep cliff along the coast of Hitachinaka city. Road pavements were broken, subsided from portion to portion and failed to perform their traffic-bearing function. Upheavals were observed on the ground surface further from the foot of the road embankment, over which liquefied subsurface soil erupted, and a nearby seafood factory was damaged. It was evident from depth-wise profiles of penetration tests that slip failures had taken place involving part of the road embankment underlain by the liquefied, loose, reclaimed soil deposit. The effect of a soft reclaimed soil deposit bounded by a stiff steep cliff and an underlying stiff mudstone layer at the site is discussed.