可液化土中单桩地震响应的离心机试验研究

Centrifuge investigation on seismic response of single pile in liquefiable soil

通过离心机动力模型试验,观测了饱和砂土层中单桩-上部结构在强震中的反应,并通过数值方法导出了桩土水平相对位移和侧向土阻力的演变。研究结果表明:强震下饱和砂土中孔压增长较快,孔压的增长减弱了土阻力及桩身内力,同时使桩基础的竖向承载力降低;砂土接近液化时,桩基础失去大部分承载力,上部结构沉降严重。本研究加深了对砂土液化过程中的桩–土动力相互作用机理的理解,有助于建立液化土中桩基抗震设计方法。

Seismic response of soil-pile-superstructure system was a very complicated issue, especially when liquefiable soil is involved. Centrifuge dynamic model tests were performed, with response of single-pile foundation under strong shaking being observed and recorded. By some numerical approaches, evolutions of soil-pile relative lateral displacement and lateral soil resistance were derived from the experimental data. It was shown that the excess pore pressure increased in a fast rate under strong earthquake. As the excess pore pressure increased, the lateral soil resistances and bending moments along the pile tended to decrease; the bearing capacity of pile foundation reduced as well. When the liquefaction was approaching, the pile foundation lost most of its bearing capacity, which resulted in a severe settlement of the superstructure. The research has furthered our understanding on the mechanism of dynamic soil-pile interaction during the development of liquefaction, and would be helpful for establishing a guideline for aseismatic design of pile foundation in liquefiable soil.