IDENTIFICATION OF FACTORS AFFECTING LIQUEFACTION-INDUCED ROAD SUBSIDENCE IN URAYASU CITY EXTRACTED FROM DIGITA SURFACE MODELS

The 2011 off Pacific coast of Tohoku Earthquake measuring Mw of 9.0 caused significant liquefaction in the Tokyo Bay area, which had been in its peak period of land reclamation projects since the World War II. In order to identify factors affecting liquefaction-induced damage to roads, the authors extracted values of road subsidence at total 224 points in Urayasu city, Chiba prefecture, from a subsidence map of the liquefied ground obtained from Airborne LiDAR surveys before and after the earthquake. The result indicates that the values of subsidence along arterial roads with thicker roadbeds are larger than those of residential roads. This feature is implemented in the empirical formula to describe road subsidence in terms of liquefaction potential index PL. In addition, improvement effects of liquefaction countermeasure are quantitatively examined on the subsidence map of the liquefied ground.