Avaliação da altura de queda do martelo do SPT manual

Abstract

The method of subsoil investigation carried out with the Standard Penetration Test (SPT) is a percussion test that is widespread in the world. In Brazil, it is practically the only field test method used in almost 100% of the foundation projects, for being a cheap and accessible methodology in all parts of the country. With SPT it is possible to obtain information about an index of resistance to soil penetration (N) on which the loads of a building will act through the foundation elements. The results of this sounding method are extremely important, because they will reflect in the structural dimensioning of the foundation, and, mainly, in its performance. For this reason, the data collected must be of the best quality possible, since there is a standardized testing methodology, NBR 6484/2020 (Soil - Simple recognition drilling with SPT - Testing method). Despite being standardized, percussion soundings with SPT receive several criticisms from Geotechnical Engineering scholars, because the lack of compliance to the requirements of the standard during the test can compromise the performance and economy of the final product, the work. To carry out this end-of-course work, an SPT drilling campaign was monitored in the city of Aracaju on May 06 and May 10, 2022. Video recordings were made of 186 standard SPT hammer blows, performed by 5 different drillers. Data analysis revealed that the average hammer drop height operated by the monitored drilling crews was above the standard value recommended by the test standard, i.e., exceeding 0.75 m. The average values of the hammer heights of the 186 hits recorded ranged from 0.77 m to 0.82 m, with a standard deviation around 0.08 m, indicating an expressive height variation in the hammer operation. The minimum and maximum values recorded were 0.61 m and the highest 0.94 m, respectively.