Experimental study of a rational liquefaction countermeasure for pile foundations in volcanic ash ground

Abstract

We study the applicability of a grid-form ground improvement method, whereby the ground around the pile foundation is enclosed by a ground improvement wall that is not in contact with the existing structure, as an aseismic reinforcement technique applicable to cases where the stability of pile foundations is only impaired due to liquefaction in volcanic ash ground, based on centrifugal model tests. As a result, it was considered that a grid spacing of 7.0 m or less and a separation distance of 2.0 m or more from the center of the outermost pile would be adequate to maintain the coefficient of horizontal subgrade reaction of the pile due to liquefaction without affecting the bridge upper and lower works or the entire bridge system. The optimum combination with improvement strength and layout should be set according to the required performance.