Vertical bearing mechanism of pile foundation in volcanic ash soil

摘要

Pile foundations for bridge piers and abutments constructed in volcanic ash ground are currentlyrndesigned based on specifications for sandy soil ground due to the similar density and internal fiction anglernof volcanic ash as those of normal sandy soil. However, mechanical characteristics of volcanic ash, such asrnfriability against confining pressure, differ strongly from those of normal sandy soil. To confirm the verticalrnbearing capacity piles in volcanic ash ground, vertical loading tests for actual piles of bridge foundations andrnstatic cone penetration tests were conducted at 14 construction sites. As the results, it was found that the skinrnfriction f of piles in pyroclastic fall deposits (fa) of volcanic ash soil developed in a manner similar to that ofrnnormal sandy soil, but that in pyroclastic flow deposits (fl) of volcanic ash soil tended to be lower comparedrnwith that of normal sandy soil, and also a correlation was confirmed between the cone tip resistance qt and skinrnfriction f of piles.