液状化地盤上の盛土耐震補強技術の開発(その2)
補強効果に関する遠心模型実験および現場施工試験
三角 真貴子*1・藤原 斉郁*1・立石 章*1・青木 智幸*1
盛土など土構造物を扱う地盤分野において,地震時の被害程度を予測する必要性が高まっている。このうち,液状化対策に関しては,従来の地震による液状化の発生を抑制する方法に対し,ある程度の変形を許容しつつ所定の機能維持を図る方法が考えられる。本研究では,この新たな液状化地盤上の既設盛土の耐震補強法について遠心模型実験を行った。その結果,補強の有無による盛土の損傷の違いに加え,改良体の位置や法面の抑え範囲を縮小させたモデルにおいても補強効果が確認でき,地盤の変形とアンカー張力の関係などが明らかとなった。また,実規模大の施工試験を行い,液状化が懸念される緩い砂地盤において本補強法の構成要素である改良体の施工が可能であることを示した。
キーワード: | 盛土,耐震補強,液状化,地盤改良,グランドアンカー |
*1 技術センター 土木技術研究所 地盤・岩盤研究室
Development of a Reinforcement Method for Existing Embankment on Liquefiable Ground (Second Report)
Centrifuge Testing and Field Experiment of Reinforcement Method
Makiko MISUMI*1, Tadafumi FUJIWARA*1, Akira TATEISHI*1 and Tomoyuki AOKI*1
In recent years, performance-based specifications have been adopted for aseismic structural designs. At the same time, it is becoming necessary to predict the settlement and lateral displacement of geotechnical engineering structures such as embankments. Specifically, when an embankment stands on liquefiable ground, a method that ensures proper function in the events of increased pore pressure in the foundation ground and that accepts some deformation may be more rational than conventional methods of suppressing excess pore pressures induced by an earthquake. In this study, a rational method of reinforcing existing embankments on liquefiable ground was developed and verified through centrifuge model tests. An embankment model with no reinforcement suffers catastrophic failure from liquefaction, while the model utilizing the developed method of reinforcement showed no damage to its top surface. The models with shorter tendon length or with smaller bearing plates also were effective against earthquake-induced liquefaction. The relationship between the ground deformation and anchor tension was presented. We performed full-scale field experiments to construct the improved soil columns in liquefiable ground.
Keywords: | embankment, reinforcement against earthquake, liquefaction, ground improvement, ground anchor |
*1 Soil and Rock Engineering Research Section, Civil Engineering Research Institute, Technology Center
16 - REPORT OF TAISEI TECHNOLOGY CENTER No.44 2011