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Soil liquefaction and cyclic mobility evaluation for level ground during earthquakes

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    ABSTRACT: Focusing on soil liquefaction, the seismic records during the Niigata-ken earthquake in 1964, the southern Hyogo prefecture earthquake in 1995 and the 2011 off the Pacific coast of Tohoku earthquake are analyzed by the non-stationary Fourier spectra. The shift of dominant frequency in the seismic record of Kawagishi-cho during the Niigata-ken earthquake is evaluated based on the time-variant property of dominant frequencies. The reduction ratio of the soil stiffness is evaluated from the shift ratio of dominant frequency. It is detected that the pulse wave in the transient process during the progressing liquefaction is composed of the primary mode and the secondary modes. Using the seismic records at the underground of Port Island during the southern Hyogo prefecture earthquake in 1995, the amplification of liquefaction is evaluated by comparing the maximum amplitude spectra of seismic records at GL 0 m and GL-83 m. The average shear strain of underground is calculated from the numerically integrated displacement profiles and the deterioration ratio of stiffness is evaluated from the G- relation. The amplification of liquefaction at Chiba bay area is evaluated by using the ratio of the maximum amplitude spectra of CHB024 and CHBH10 (Borehole) from the mainshock and the aftershock of the 2011 off the Pacific coast of Tohoku earthquake.
    Soil Dynamics and Earthquake Engineering 04/2015; 71. DOI:10.1016/j.soildyn.2015.01.017 · 1.30 Impact Factor
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    ABSTRACT: Bedsa is one of the districts in Dahshour that lays south west of Cairo and suffered from liquefaction during October 1992 earthquake, Egypt. The soil profile consists of alluvial river Nile deposits mainly sandy mud with low plasticity; the ground water is shallow. The earthquake hypocenter was 18 km far away with local magnitude 5.8; the fault length was 13.8 km, as recorded by the Egyptian national seismological network (ENSN) at Helwan. The analysis used the empirical method introduced by the national center for earthquake engineering research (NCEER) based on field standard penetration of soil. It is found that the studied area can liquefy since there are saturated loose sandy silt layers at depth ranges from 7 to 14 m. The settlement is about 26 cm. The probability of liquefaction ranges between 40% and 100%. The presence of impermeable surface from medium cohesive silty clay acts as a plug resisting and trapping the upward flow of water during liquefaction, so fountain and spouts at weak points occurs. It is wise to use point bearing piles with foundation level deeper than 14 m beyond the liquefiable depth away from ground slopes, otherwise liquefaction improving techniques have to be applied in the area.
    09/2014; 5(3). DOI:10.1016/j.asej.2014.02.001
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