Problems of Ground Improvement Raised in Recent Earthquakes and Their Subsequent Response

Abstract

In the field of earthquake engineering, many problems have been raised in past large earthquakes, and subsequent research and technical development are being carried out. Three important problems of ground improvement raised in recent earthquakes are introduced in this paper. Since the 1995 Hyogoken-Nanbu (Kobe) Earthquake caused a very strong shake, it was necessary to consider a new design philosophy concerning liquefaction countermeasure that can withstand extremely strong shake. Therefore, not only the occurrence of liquefaction but also a new evaluation method to estimate the deformation of the structure was introduced. The 2004 Niigataken Chuetsu Earthquake caused severe damage to residential complexes developed by artificially embanking at hills and terraces. Therefore, researches on appropriate ground improvement method to prevent slide of the embankment slope began. The 2011 Great East Japan (Tohoku) Earthquake demonstrated the need for a new concept of measures to prevent liquefaction in areas encompassing houses, roads and lifelines because liquefaction occurred in many residential areas. Then a new project to improve the liquefiable soil of an entire area by lowering water table started.