An Alternative Method of Measuring SPT Energy

Despite problems associated with its repeatability and reliability, the standard Penetration Test (SPT) continues to be the most widely used in-situ test for liquefaction potential assessment. There are many factors known to influence the SPT results but the most significant factor affecting the N value is the amount of hammer energy delivered into the drill rods. The existing method of SPT energy measurement consists of attaching a load cell near the top of the drill rods and measuring the force time history during hammer impact. An alternative method of SPT energy determ1nat1on based on measurement of both force and acceleration time history is described. It is shown that the proposed method is more fundamental and avoids several shortcomings in the existing method. Field measurements are presented and SPT energies calculated by both methods are compared