LIQUEFACTION FAILURE PORE-PRESSURE MODELS OF ZHOUSHAN MARINE SANDY SOIL UNDER CYCLIC EXCITING LOADING
WANG Yajun1，2，JIN Feng2，ZHANG Chuhan2，WANG Jinting2，GAN Xiaoqing3
(1. School of Naval Architecture and Civil Engineering，Zhejiang Ocean University，Zhoushan，Zhejiang 316000，China；2. State Key Laboratory of Hydroscience and Hydraulic Engineering，Tsinghua University，Beijing 100084，China；3. Key Laboratory of Geotechnical Mechanics and Engineering of Ministry of Water Resources，Yangtze River Scientific Research Institute，
Wuhan，Hubei 430010，China)
Abstract：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.
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2013, Vol. 32 
