Cases Histories and Recent Development of the Sand Compaction Pile Method as a Countermeasure Against Liquefaction

The Sand Compaction Pile (SCP) method is the most useful countermeasure against liquefaction in Japan. The investigation on the effectiveness of improved ground by the SCP method suffered from the past large-scale earthquakes (the 1993 Kushiro-Oki Earthquake, the 1994 Hokkaido Toho-Oki Earthquake, the 1995 Hyogo-ken Nambu Earthquake etc.) were conducted and found that the behavior of the compacted ground apparently differ from unimproved one. Especially less subsidence occurred on the compacted area compared with the unimproved area at Port Island and Rokko Island during even the 1995 Hyogo-ken Nambu (Kobe) earthquake. The conventional SCP method aims to increase the bearing capacity of soft ground by reinforcing it as compacted ground, or by increasing the density of loose sandy ground, through the vibratory installation of additional sand piles. However, the use of a vibro-hammer generates noise and vibration, which may adversely affect the surrounding environment. It is therefore difficult to use this method for ground improvement work in urban areas or on sites close to existing structures. To reduce noise and vibration, the non-vibratory SCP method which is based on a rotary penetration system using a forced lifting/driving device and a rotary drive motor were developed. This paper describes the case histories during the past large-scale earthquakes and newly development (objectives, applications etc.) of the SCP method applied as a countermeasure against liquefaction in Japan