CAJ | 학술논문

主震结束后，余震引起的再液化会对土工结构物带来进一步的严重灾害。以人工岛为研究对象，基于 FE-FD 耦合有限元方法，考虑有无余震、不同余震大小和主余震不同时间间隔因素，探讨对人工岛再液化灾害的影响规律。研究结果表明：主震结束后，随着超孔隙水压力的消散，人工岛砂土层液化区域逐渐减小，余震发生时液化区域又开始扩展，甚至可能大于主震结束时的液化区域面积，且其灾害程度比无余震发生时的要大得多；随着主、余震的时间间隔增加，间隔期的土层固结排水很大程度地提高人工岛的抗再液化能力，当超孔隙水压力消散完后，在相同余震等级情况下很难再次达到完全液化；随着余震峰值加速度的增加，人工岛的沉降量和水平侧移量都随之增加，再次液化时间点会向前提前数秒，主震结束后，随着土层的固结排水，人工岛的沉降会继续增加，甚至超过主震引起的沉降量，而水平侧移的产生主要发生在地震液化过程中，在后续的固结排水中几乎不变；余震发生前，如果人工岛的砂土土层仍处于液化状态，则液化层可能会起到隔震作用，减轻余震对岛体造成的灾害。
주진결속후，여진인기적재액화회대토공결구물대래진일보적엄중재해。이인공도위연구대상，기우 FE-FD 우합유한원방법，고필유무여진、불동여진대소화주여진불동시간간격인소，탐토대인공도재액화재해적영향규률。연구결과표명：주진결속후，수착초공극수압력적소산，인공도사토층액화구역축점감소，여진발생시액화구역우개시확전，심지가능대우주진결속시적액화구역면적，차기재해정도비무여진발생시적요대득다；수착주、여진적시간간격증가，간격기적토층고결배수흔대정도지제고인공도적항재액화능력，당초공극수압력소산완후，재상동여진등급정황하흔난재차체도완전액화；수착여진봉치가속도적증가，인공도적침강량화수평측이량도수지증가，재차액화시간점회향전제전수초，주진결속후，수착토층적고결배수，인공도적침강회계속증가，심지초과주진인기적침강량，이수평측이적산생주요발생재지진액화과정중，재후속적고결배수중궤호불변；여진발생전，여과인공도적사토토층잉처우액화상태，칙액화층가능회기도격진작용，감경여진대도체조성적재해。
Re-liquefaction induced by aftershocks causes serious hazards on soil structures after the end of the main shock.In this study,the influences of aftershocks on an artificial island are discussed based on the FE-FD coupling finite element analysis method at different scales of after-shocks and interval time between the main shock and aftershock.The results indicate that with dissipation of excess pore-water pressure after the main shock,liquefied areas in the sand layer of the artificial island gradually decrease;however,the liquefied areas expand rapidly when an after-shock occurs,and can possibly be larger than the liquefied areas induced by the main shock;the extent of damage to the artificial island is much worse when an aftershock occurs than when it does not.The increasing of the interval time between the main shock and aftershock results in the drainage consolidation during this time significantly improving the ability of the artificial island to re-liquefy;thus,full-scale re-liquefaction in the artificial island is difficult when the excess pore-water pressure entirely dissipates.Settlement and horizontal displacement of the artificial island increases with increase of the peak acceleration of the aftershock and the liquefaction point-in-time of the sand layer occurs a few seconds early.After the main shock,with drainage by consolidation in the soil,settlement of the artificial island continues to increase,and is even larger than the set-tlement induced by the main shock,but the horizontal displacement barely changes.Before the af-tershock,if the sand layer of the artificial island is still liquefiable,the sand layer may play a role in seismic insulation and reduce the hazards caused by the aftershock to the artificial island.There-fore,it is necessary to consider multiple seismic fortifications during a period of time for offshore structures,especially for artificial islands.