Soil liquefaction observed at the lower stream of Tonegawa river during the 2011 off the Pacific Coast of Tohoku Earthquake

Earthquake reconnaissance investigations were carried out at regions located along the lower stream of Tonegawa River where widely spread soil liquefaction and associated phenomena were observed following the main shock and aftershocks of the 2011 off the Pacific coast of Tohoku Earthquake. A multiple series of Swedish Weight Sounding tests were carried out at Sawara of Katori City, Hinode of Itako City, and Wanigawa and Fukashiba of Kamisu City. The soil profiles responsible for the damage inflicted by soil liquefaction were demonstrated along with the help of SPT data. At some locations where the soil samples of erupted sand boils were retrieved, the profiles of relative density and factor of safety against liquefaction with depth are estimated and discussed in detail. The use of Swedish weight sounding tests along with a help of SPT soil profiling proved an effective method for detecting liquefiable soil layers responsible for widespread soil liquefaction induced damage.