CAJ | 학술논문

为探究舟山海相土在海洋环境中的液化失效规律,选用2类代表性海相砂土:乌石塘海相粗砂MS1及东沙海相细砂MS2,利用X射线衍射(XRD)及扫描电镜(SEM)试验获得微细观物相结构,二者均属石英矿相碱性海相沉积物.在不同激振幅值下,采用GDS动三轴系统进行一系列双向循环激振加载试验.试验结果表明:海相粗砂MS1产生高周循环液化时对应的激振幅值较低,而在低周液化下激振幅值则较高,海相细砂 MS2在液化偏应力较小时可承受高周循环加载,而在液化偏应力较大时只可承受低周循环.基于归一化初始液化周数比建立舟山海相砂土的液化孔压模型并给出参数取值,模型揭示:2类海相砂土均随激振应力比增加而更易于液化;基于循环增量孔压比及Finn破损参数,建立舟山海相砂土初始液化破坏内时模型,并给出试验参数,模型揭示:过大的激振压缩应变诱发剪缩变形,导致海相粗砂MS1液化破坏,而海相细砂MS2的液化破坏则源于拉应变增大诱发的颗粒间接触失效.海相砂土宏观尺度的初始液化破坏是其微细观物相结构劣化积聚的最终结果,宏观力学机制与微细观试验分析结论吻合.
위탐구주산해상토재해양배경중적액화실효규률,선용2류대표성해상사토:오석당해상조사MS1급동사해상세사MS2,이용X사선연사(XRD)급소묘전경(SEM)시험획득미세관물상결구,이자균속석영광상감성해상침적물.재불동격진폭치하,채용GDS동삼축계통진행일계렬쌍향순배격진가재시험.시험결과표명:해상조사MS1산생고주순배액화시대응적격진폭치교저,이재저주액화하격진폭치칙교고,해상세사 MS2재액화편응력교소시가승수고주순배가재,이재액화편응력교대시지가승수저주순배.기우귀일화초시액화주수비건립주산해상사토적액화공압모형병급출삼수취치,모형게시:2류해상사토균수격진응력비증가이경역우액화;기우순배증량공압비급Finn파손삼수,건립주산해상사토초시액화파배내시모형,병급출시험삼수,모형게시:과대적격진압축응변유발전축변형,도치해상조사MS1액화파배,이해상세사MS2적액화파배칙원우랍응변증대유발적과립간접촉실효.해상사토굉관척도적초시액화파배시기미세관물상결구열화적취적최종결과,굉관역학궤제여미세관시험분석결론문합.
@@@@Cyclic triaxial tests were performed on marine sandy soil from Zhoushan Seas by GDS loading apparatus under different exciting amplitudes of bidirectional wave loadings to study the liquefaction of typical marine soil samples MS1 and MS2,which are taken from Wushitang coast and Dongsha coast respectively. X-ray diffraction(XRD) and scanning electron microscope(SEM) experiments were accomplished to study the phase structures of MS1 and MS2. MS1 and MS2 are both alkaline marine sediments with quartz mineralography. It is found that the high-cycle liquefaction on marine coarse sand MS1 can be induced under low amplitude and its low-cycle liquefaction can be induced under high amplitude. The marine fine sand MS2 can carry high-cycle wave loading under low liquefying deviatoric stress and can carry only low-cycle wave loading under high liquefying deviatoric stress. The liquefaction pore pressure model and its controlling parameters′values are established based on the normalized relationship between cycle-time at any time during initial liquefying period and initial-liquefaction critical cycle-time. The typical marine sandy samples MS1 and MS2 are inclined to be liquefied under the accumulation of exciting stress ratio. The endochronic failure model under initial-liquefaction and its controlling parameters′ values are obtained based on dynamically incremental pore-pressure ratio and damage parameter introduced by Finn. It is found that the liquefying failure of MS1 is induced by shear-contraction due to excessively exciting compression strain;and marine fine sand MS2 is liquefied under cumulative tension strain that causes the contacts failure of soil particles. The cumulative deterioration for micro-meso-physical structures of marine sediments induces their macro initial-liquefaction failure. The macro-mechanical characteristics of marine sandy soil from Zhoushan Seas consist with their micro-meso-physical phase structures evolution.