Estimation of Standard Penetration Test (SPT) of Hilla City - Iraq by Using GPS Coordination

Abstract

In many parts of the world, The Standard Penetration Test (SPT) is still considered one of the most common in-situ tests to evaluate the strength of coarse grained soil and often the only in-situ test performed during a site investigation. In the present study, site characteristics of Hilla city are investigated by using in-situ (SPT) test by drilling five boreholes distributed over Hilla city with different depths (15-17) m below natural ground surface. In this study, site characterization is treated as a task of function approximation of the large existing data from standard penetration tests of Hilla City, Iraq. The number of blows (N) from more than (950) field standard penetration tests has been collected with different depths from 110 boreholes spreaded over Hilla city, Iraq. Distribution and variation of N values of standard penetration tests at different depths are presented and discussed in this paper. Results from data analysis show that large variation of N values occurs at the upper layer of the soil and that variations decrease with increasing depth below ground surface. The results indicate that N values increase with increasing the depth to approximately 5 meters below natural ground surface, after that N values decrease with increasing the depth up to 8 m, then N values increase with increasing depth below 8m. Mathematical model is presented by using Statistica program to find N values (number of blows ) of SPT test for Hilla city by using GPS coordination (Latitude (N) and longitude (E)) in any location of the study area. The results obtained show that the statistical model is accurate in predicting N values (number of blows ) of SPT test in Hilla city and that the empirical equation can be depended on.