Seyed Abolhassan Naeini - Associate Professor, Department of civil engineering, Imam Khomeini
Reza Ziaie Moayed - International University, Qazvin, Iran
Afshin Kordnaeij - PhD. student, Department of civil engineering, Imam Khomeini International University, Qazvin, Iran

In engineering design of structures, instead of modeling the subsoil in all its complexity, it can bereplaced by a much simpler parameter called subgrade reaction modulus ( s K ). Plate load test (PLT) isone of the frequently applied methods to determine this parameter directly. As the determination of Ksfrom PLT is relatively time-consuming and costly, especially in depths, various empirical correlationshave been proposed to relate the s K to the results of standard penetration tests (SPT) which is one of themost frequently utilized tests during the geotechnical investigation. The purpose of this study is toperform regression analyses to correlate the s K with the corrected SPT blow count ( 60 N ) and soilindex parameters such as liquid limit (LL), plastic index (PI) and fine-grained content (FC) using adatabase containing 123 data set obtained from a geotechnical investigation sites performed in Qazvin,Iran. In accordance with these correlations, new empirical equations are developed. Furthermore, theaccuracy of the previously proposed empirical correlations was determined using the available data. Theresults demonstrate that an improvement with respect to the other correlations has been achieved.

Subgrade reaction modulus, plate load test, standard penetration test, clayey soil