筒型基础–砂土地基动力响应的离心振动台试验研究
Centrifugal shaking table tests on dynamic response of bucket foundation-sandy soil
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摘要: 抗震规范要求对地震烈度大于Ⅷ度地区15 m以内的土层进行砂土液化判断。新型海上风电筒型基础入土深度较浅,对地震作用下砂土地基的液化较为敏感。为研究砂土中新型筒型基础与地基的地震响应规律,设计并开展了系列离心机振动台试验,监测了砂土中新型筒型基础与地基在震中和震后的加速度变化和孔压响应,分析了筒型基础影响砂土地基抗液化性能的规律性。结果表明:地震荷载作用下,砂土地基中筒型基础加速度响应系数大于1.0,且响应系数与基础重量呈正相关关系;新型筒型基础因其直径通常大于30 m,质量大于2000 t,与上部荷载的联合作用显著增加了地基中的附加应力,有利于提高砂土地基的抗液化能力;基于超静孔压比建立了筒型基础影响区域地基抗液化性能的判别方法,定量分析筒型基础提高砂土抗液化能力的程度。Abstract: In the sites with seismic intensity greater than 7 degrees, liquefaction identification of sandy soil within 15 m is required by the relevant seismic codes. The shallow-buried bucket foundation, a new type of foundations for offshore wind turbines, is sensitive to the liquefaction of shallow sandy soil subjected to earthquake loads because of the shallow depth of its burial. To study the seismic response rules of shallow buried-bucket foundation-sandy soil, a series of centrifugal shaking table tests are designed and carried out. Acceleration changes of shallow-buried bucket foundation and sandy soil as well as the pore pressure responses of the sandy soil are monitored during and after earthquakes. Also, the influence rules of bucket foundation on the anti-liquefaction performance of sandy soil foundations are analyzed. The results show that the acceleration response factor of bucket foundation in sandy soil subjected to seismic loading is greater than 1.0, and the response coefficient is positively correlated with the bucket foundation weight. As the shallow-buried bucket foundations are usually larger than 30 m in diameter and 2000 t in weight, the combined effect with the upper loads significantly increases the additional stress in the sandy soil foundation, which is beneficial to improve the anti-liquefaction capability of sandy soil foundations. Based on the excess pore pressure ratio, the method for determining the anti-liquefaction performance of sandy soil affected by the bucket foundation is established. And the degree of improving the anti-liquefaction of sandy soil by the bucket foundation is quantitatively analyzed.