LIQUEFACTION COUNTERMEASURE METHODS USING A COMBINATION OF PILES AND RAFT FOUNDATIONS

Saturated loose sandy ground is easily liquefied and damaged during earthquake shaking. In recent years, seismic design that takes into account liquefaction has become required in various kinds of standard specifications. Some countermeasures for liquefaction have been developed, including soil improvement techniques and seismic reinforcement using piles. This paper reports on liquefaction countermeasure methods using a combination of piles and raft foundations. Raft foundations with sallow soil improvement could reduce the differential settlement of building. The piles could share parts of lateral loading during sand liquefaction and reduce the shear deformation of the ground surrounded by piles. The purpose of this research is to understand the lateral-loading share ratio of piles and shear-deformation reduction rate of ground with different pile spacings. It will attempt to solve engineering questions on designing piles foundations against sand liquefaction, both in simplified terms and in terms of providing a basic understanding for appropriate analytical platforms. The performance of piles in liquefying ground under lateral loading is a complex problem, so to simplify it, our research is two-fold: 1) the lateral-loading share ratio of piles, and 2) shear deformations reduction rate of ground. This paper focuses on the first part: the lateral-loading share ratio of piles.