Significance of nonlinear soil-structure interaction (SSI) on the seismic performance of micropiles-retrofitted pile foundations

多年来，人们开发和采用了各种抗震加固技术和策略，以确保在修订抗震设计规范之前建造的现有桥梁的抗震性能。然而，对于翻新，人们往往把重点放在桥墩上，而对基础的关注较少。引起如此关注的原因有很多，其中一个原因是加固后的基础的抗震性能相对较少为人所知。2016年熊本地震造成的破坏揭示了一座桥梁基础的失效，尽管大桥的桥墩经过了抗震改造，这突显了对基础进行抗震改造的必要性。在实际地基加固中，由于微型桩的几个优点，往往比传统桩更受青睐。然而，考虑土-结构非线性相互作用(SSI)效应的微型桩基础在动力荷载作用下的性状仍是一个未知的问题。为此，对埋入土壤中的微型桩-加筋桩基在静、动载作用下的1G模型试验进行了研究。根据动力相互作用系数和桩头横向阻抗函数对计算结果进行量化。考虑了基于相似律的1/20加筋地基模型。对于土壤，选择干燥的岐阜砂。

Various seismic retrofitting techniques and strategies have been developed and employed over the years to ensure the seismic performance of existing bridges built prior to the revision of seismic design codes. For retrofitting, however, focus is often given to the bridge piers while lesser attention is paid to the foundations. Out of the many reasons for such attention to the foundations, one can be attributed to the relatively lesser-known seismic performance of the retrofitted foundations. Damage seen in 2016 Kumamoto earthquake revealed the failure of a bridge foundation even though the pier of the bridge was seismically retrofitted, highlighting the necessity of seismic retrofitting of foundations. In practice, for foundation retrofitting, micropiles are often preferred over the traditional piles for its several merits. The behavior of micropiles-retrofitted foundations considering the effects of nonlinear soil-structure interaction (SSI) under dynamic loading, however, is still largely unknown.To this end, 1g model testing of micropiles-retrofitted pile foundations embedded in soil is considered under a range of static and dynamic loads. Results are quantified in terms of kinematic interaction factors and lateral pile-head impedance functions. A 1/20 model of retrofitted foundation based on the law of similitude is considered. For soil, dry Gifu sand is selected.