Influence of rotation velocity in the torque measurement in SPT-T test

Abstract

In Brazilian foundation practice, SPT Test is generally used in the design of pile and shallow foundations. By the way, Mayne (2001) inquire how just a number (N-value) is enough to estimate a great number of different soil parameters and advocated the use of in situ testing with hybrid devices. Ranzini (1988) just already suggested supplementing the conventional SPT with measurement of the torque required to turn the split spoon after driving. After this, some engineers began to use that new technique. Peixoto (2001), in her Ph.D. Thesis "The SPT-T Test and his Application in Foundation Engineering”, studied several aspects of that test: the behavior of the torque versus rotation degree shape; the T/N ratio; the speed test and a suggestion of a method to predict the bearing capacity of piles. But, it is either necessary to study the influence of the rotation velocity in the torque measurement. In this manner, this research pretends verify the efficiency of the torque measurement correlating to the rotation velocity when the torque is applicated. In each in situ test, it will be obtained a torque versus rotation-degree curve, as Peixoto (2001). Through these curves will be analyzed the behavior of the curve and the rotation velocity. It will be also analyzed the influence of a single velocity when different torque values are applied, and will be done a statistical analyzes to verify the repeatability results.