Correlation between standard penetration (N SPT) and shear wave velocity (V S) for young coastal sands of the Caspian Sea

Abstract

Nowadays, the dynamic properties of soil and study of its dynamic response in connection with the designing of the structures resistant against earthquake seems more critical day by day along with the increase of the structures’ height and specialization of the civil operations. Since geophysical tests are often costly and time consuming, applying other tests results for estimation of Shear wave velocity is extremely useful. For this purpose, this paper focuses on determining and offering a relationship between the results of standard penetration test (SPT), which is highly quick, cost-effective, and common test, with shear wave velocity of soil. For this end, several boreholes with different depths were drilled in several coastal cities of the Caspian Sea, and SPT was carried out in them. Then downhole test for calculating shear wave velocity profile was performed in all the studied sites using the same borehole and, in some cases, by drilling a new borehole. After that, the data were analyzed for determining the correlation via a suitable statistical method. The results indicated that the obtained relationship is suitably compatible with the universal practical relationships presented for sandy soils and stands approximately in the upper limit of the relationships. It is noteworthy that although applying these relationships for the estimation of shear wave velocity in the coastal sands of the Caspian Sea for small projects and the initial phases of the average and big projects is recommended, it must be considered that direct geophysical methods must be employed in cases where this parameter seems more critical.