SEISMIC RESPONSE CHARACTERISTICS OF FOUNDATION COMPOSED OF MICROPILES AND SOILBAGS AND ITS SUPERIORITY TO PILE FOUNDATION

抄録

 In this paper, a new type of foundation composed of micropiles and soilbags is proposed. The foundation is characterized by laying soilbags between the pile head and footing on which a superstructure stands. The expected effects of the foundation are: (1) eliminating the fixed junction between the piles and the footing, (2) reducing the diameter of piles, and (3) reducing the response acceleration of structures. In this study, a seismic response evaluation method for the proposed structure in real-scale is also proposed, and the seismic responses of the proposed structure and pile foundation are compared with different conditions of input acceleration and height of pier. From the calculation results, except for the case where the pier height was low, it was found that, compared to a pile foundation, the prolonged period due to the uplifting of footing during rotation may cut off peak response acceleration of the pier and suppress the bending moment at the base of the pier. It was also found that the response displacement of the proposed structure was almost the same as that of the pile foundation, and that the residual displacement of the proposed structure was smaller than that of the pile foundation. Moreover, it became clear that laying the soilbags could suppresses the bending moment of piles.