Evaluation and zonation of liquefaction potential of coastal deposits (case study: coastal region of southern Pars gas-field)

Liquefaction is considered as natural hazard that directly affect the stability of infrastructures projects. The potential of liquefaction for an area is controlled by many factors including the type of soil, water presence and the seismicity risk. South Pars region is located to the southern part of Bosheher Province which is recognized as developed industrial area and include many lifeline and sensitive projects. From the geological point of view, the study area is formed as an alluvial fan which consists of loose and young deposits that is a mixture of clay, silt, sand and gravel layers. In this research, investigation reports of the phases 12, 14, 19 and many related reports of the coastal part of southern Pars Gas-field were collected and studies. The N values calculated from SPT tests and other geotechnical data for 60 boreholes were used to evaluate the liquefaction potential of the sand layers. Due to the large amount of the reviewed data, the information of only 16 boreholes were presented in this paper. The results showed that during the event of large earthquake of magnitude of 7 on the Richter scale and production of horizontal acceleration at 0.3g, liquefaction occurrence in the region at phases 12 and 19 is possible. Based on the calculation of liquefaction potential index (LPI), the results showed that by approaching the coast line the potential of liquefaction of sand deposits is increased due to high percentage of soil saturation. In contrast, by distancing from the coast line towards the land this potential is decreased due the increment of soil gradation.