東北地方太平洋沖地震で効果が確認された液状化対策事例と新たな地盤改良工法
石井 裕泰*1・船原 英樹*2・松井 秀岳*1・堀越 研一*1
先の東北地方太平洋沖地震においては,甚大な津波被害と並んで,地域によっては著しい液状化被害がもたらされた。震災から復旧した産業施設,あるいは他地域に位置するもについて,今後,地盤の耐震補強の必要性が高まることが見込まれる。特に,既設構造物を対象とする場合,様々な施工上の制約が課されることになり,これらを克服できる技術の重要性も高まるものと考えられる。
本報ではまず,筆者らが関わった液状化対策を概観し,東北地方太平洋沖地震で確認された対策効果に言及する。次にこれらの具体例を題材に,液状化対策における施工条件を比較する。最後に,供用中のタンク直下を対象とした最新の液状化対策工法を取り上げ,適用技術の特徴や適用効果を示す。
キーワード: | 地盤改良,液状化対策,砂杭締固め,浸透注入 |
*1 技術センター 土木技術研究所 地盤・岩盤研究室
*2 技術センター 建築技術研究所 建築構工法研究室
Effectiveness of Liquefaction Countermeasures in 2011 Tohoku Region Pacific Coast Earthquake, and an Innovative Soil Improvement Method for Existing Structures
Hiroyasu ISHII*1, Hideki FUNAHARA*2, Hidetake MATSUI*1 and Kenichi HORIKOSHI*1
In addition to the damage caused by the tsunami, the 2011 Tohoku Region Pacific Coast Earthquake created vast areas of liquefaction. Demand for seismic reinforcement of soils beneath existing structures appears to have increased not only in the devastated areas, but also in other places where seismic events are expected in the near future. This paper reviews the liquefaction countermeasures that the authors were in charge of during construction. Work restrictions are highlighted to show how they were overcome. The effectiveness of the liquefaction countermeasures are also examined through site inspections. Finally, an innovative soil improvement method recently developed by the authors is introduced. The method consists of directional drilling and permeation grouting that can effectively and economically improve the soil beneath existing structures.
Keywords: | ground improvement, liquefaction countermeasure, sand pile compaction, permeation grouting |
*1 Soil and Rock Engineering Research Section, Civil Engineering Research Institute, Technology Center
*2 Building System and Material Research Section, Building Engineering Research Institute, Technology Center
08 - REPORT OF TAISEI TECHNOLOGY CENTER No.44 2011