Seismic Reinforcement for Foundation Utilizing Sheet Piles and Soil Improvement

抄録

This paper reports a case study of seismic reinforcement for pile foundation of Daisokugawa Bridge in Kagawa prefecture in Shikoku Island. The most popular reinforcement method for the foundation is the additional pile method; however, it was difficult to adopt this method for Daisokugawa Bridge because some piers were close to the road. Therefore, we considered the possibility of adopting a reinforcement method utilizing sheet piles that can minimize the area widening of the footing. In conducting the design, it was necessary to verify that the shear failure would not occur during the Level 2 earthquake motion by executing a beam spring analysis. As a result of the design calculation, this reinforcement method couldn’t prevent the shear failure of the piles and the footing because the superstructure’s inertial force is large and the liquefaction may occur during the earthquake. In consideration of these circumstances, we adopted a reinforcement method utilizing sheet piles and soil improvement: improving soil inside the steel sheet piles by the high pressure injection stirring construction method. Already, installation of the steel sheet piles, the soil improvement and the expansion of the footing of two piers have been finished.