دانلود رایگان مقاله انگلیسی تخمین پتانسیل روانگرایی خاک با استفاده از سرعت موجی برشی در تهران، ایران - اشپرینگر 2017

ABSTRACT:

Shear-wave velocity (VS) offers a means to determine the seismic resistance of soil to liquefaction by a fundamental soil property. Iwasaki’s (1982) method is used to measure the liquefaction potential index for both of them. It follows the general format of the Seed-Idriss (1685) simplified procedure based on standard penetration test blow count and shear wave velocity (VS) on the basis of Andrus et al. (2004) using case history data from 43 boreholes in soils ranging from fine sand, silty sand, gravely sand to profiles including silty clay layers and the average soil shear wave velocity (VS 30) in the south Tehran. Liquefaction resistance curves were established by applying a modified relationship between the shear-wave velocity and cyclic stress ratio for the constant average cyclic shear strain. The study area is the south-east of Tehran and the route of Tehran Metro Line 7. It is observed that there is not a perfect agreement between the results of the two methods based on five empirical relationships assuming cemented and non-cemented condition for soils. Moreover, the liquefaction potential index (PL) value in the Standard Penetration Test (SPT) method is more than that of the VS method. Liquefaction potential index (PL) values based on shear wave velocity (VS) using five empirical relationships in two un-cemented and cemented soil show that the used relations are overestimated and most of them have shown non-liquefaction condition for soils in the studied area.

7. CONCLUSION

The present study investigated the two field methods used to evaluate liquefaction potential of soils including Standard penetration Test (SPT) and Shear wave velocity test (VS) based on empirical relationships between them. The comparison of the safety factor values and liquefaction potential index revealed that the severity/seriousness of liquefaction occurrence in the studied area based on VS method is was lower than the one based on SPT based method. Furthermore, it can be observed that the relationships between Standard Penetration Test and shear wave velocity are not appropriate. Because the relationships used in the present study are dependent on soil type, fines content (clay and silt), type of tests and their accuracy, it would be much safer to perform both methods for the same place and then compare the results in order to evaluate the liquefaction potential. Last but not least, further studies are called for to obtain better relationships based on the type of soils within the area of the study