Proposal of an Energy Comparison System in the SPT

G.W. Barreto, J.C.A. Cintra, N. Aoki

Article

Soils and Rocks, São Paulo, 37(1): 61-71, January-March, 2014 | PDF


Abstract

This paper describes a mechanical device to compare the energy transference from the blow of a hammer to the stem referring to standardized and non-standardized equipment in Brazil. The device allows to measure the vertical displacement of a sleeve due to one or more blows of a hammer falling freely. Tests were carried out using three pieces of equipment for the SPT measurements, but only one was mounted on a tripod standardized by the NB 6484:2001 norm. Based on the displacement values, a comparative analysis of the available energies of the equipment was conducted. The efficiency of the standard tripod for the test performed without a strict control of the fall of the hammer relative to the transfer efficiency of the test performed with a strict control of the fall height was 82.5%, showing a significant influence of human factor on the results. The lowest coefficient of variation of the displacements (5.05%) was obtained for the test using mechanized equipment with an automatic hammer. From the standpoint of the available energy of the system, it is possible to use non-standard equipment by applying the correction factor (Cf) to SPT results. Finally, static tests wereperformed on the sleeve and the energy transferred to the system was calculated.


Submitted on March 28, 2013; Final Acceptance on October 24, 2014; Discussion open until July 31, 2014.