Evaluation of friction angle in sand and cohesion in Clay based on SPT-N values in Jordan, Palestine, and the USA.

The Standard Penetration Test (SPT) is used to determine the soil strength for many purposes. This research aims to estimate the relationship between the friction angle of sand and the cohesion of clay in Jordan, Palestine and the USA, using SPT since the soil strength tests are expensive and the SPT is common test and widely use. After data collection, comprehensive laboratory tests were carried out. The regression analysis was used to draw relationship between studied parameters (friction angle vs SPT in sand and cohesion vs SPT in clay). The proposed equations were validated and compared with other equations obtained from similar regions. Furthermore, the proposed equations were used to calculate the friction angles and cohesion values. Moreover, the results from Palestine and USA equations show good correlations with errors not more than 10% and (13 to 30) kPa, for friction angle and cohesion, respectively. The Jordan national code equation overestimated the results compared with the proposed equation for Jordan. The Jordanian national code equations need to be changed to calculate friction angle and cohesion based on the proposed equations. Accordingly, the proposed equations are useful to estimate the friction angle and cohesion based on the SPT prior to the final design stage. [ABSTRACT FROM AUTHOR]