Determination of SPT End Bearing and Side Friction Resistances Using Static Uplift Tests

Abstract This note described a simplified procedure and an interpretation method introduced to the standardized standard penetration test (SPT) routine to obtain new parameters for the design of foundations. For the application of this new methodology, the following two additional measurements were necessary: the energy delivered to the rod during hammer impact and the sampler shaft resistance determined from static uplift. In this investigation, nine uplift tests were conducted on the SPT sampler at three different depths for the determination of the SPT side friction resistance. The SPT end bearing resistance was calculated from the difference between the shaft resistance and the static resistance of the SPT sampler during driving, which was estimated using Hamilton's Principle. The preliminary results of this research are promising and show that the SPT could provide measurements of end bearing and side friction resistances along the soil profile investigated. From these parameters, an SPT normalized friction ratio was determined for the classification of soil in a way that is similar to the normally used method based on CPT data. In addition, the results indicated that the direct correlation between SPT and CPT end bearing resistances appears to be more reliable than the commonly used correlation between CPT end bearing and SPT N-value.