عنوان مقاله [English]
Liquefaction-induced damages are more highlighted in saturated fine-sand deposits where huge pore pressure buildup will cause premature strength loss within stratum underneath. The potential for occurrence of liquefaction is directly dependent on factors like soil type, seismicity of the region, location of water table and the overlying non-liquefiable stratum thickness. The current paper will focus on the effect of the overlaying non-liquefiable stratum on the liquefaction potential of the underlying layer which is inherently liquefiable. Ishihara method was invoked for this aim and a corrected safety factor was proposed which considers the effect of liquefiable underlying and non-liquefiable overlying layers depth. In order to implement the suggested liquefaction potential correction scheme to a case in real world, Mazandaran province in North Iran was selected to investigate the liquefaction potential in its different regions. Liquefaction potential was sought by
adoption of different criteria. In all the employed criteria, standard penetration test, SPT data was used to calculate the cyclic resistance ratio and the cyclic stress ratio was also estimated according to the seismicity of
the region. Then the liquefaction potential is calculated from different methods. Correction is finally applied to the calculated safety factors which reflect the liquefaction potential in different regions. A tentative
liquefaction zoning map was then provided for Mazandaran province which enables the engineers to avert uncalled-for situations by emphasizing the necessity of detailed study in zones with high liquefaction potential. The proposed zonnation map is more or less qualitative due to the lack of sufficient test boreholes and also the need for more sophisticated in-situ test schemes. However it can pave the way toward an initial understanding of the liquefaction potential in different urban areas. To be more specific, it is crucially important to pay more attention to the liquefaction issue in some coastal cities like, Babolsar and Mahmoudabad which are heavily populated and potentially liquefiable at the same time. Measurements like deep and mat foundations, gravel or stone columns and wick drains are alternative in case remedial or improvement provisions are necessary. Microzonnation will however need more densely-allocated in-situ test scheme and detailed investigation on
the liquefaction potential which is followed according to the importance of the structure and the construction location.