Efeito do teor de finos nos parâmetros de estados críticos de solos transicionais

Abstract

Mixtures of sand and fines exhibit different behaviour than pure materials. These mixtures are referred to as transitional soils. Several studies have found that there is a fines content above which the properties of the mixture are dominated by the fines matrix. This parameter is referred to as the transitional fines content. Freire (2019) determined compressibility and strength parameters for mixtures of fines and sand from the Post Barreiras Formation collected in the city of Natal, Brazil. This work, which continues the work of Freire (2019), aimed to analyse the critical state parameters of the same materials. The finenesses used were: 0, 10, 20, 30, 40, 50, 75 and 100 mass percent of the sandy fraction. Geotechnical characterization tests were performed to determine the critical state parameters. Triaxial tests were performed. For the undrained triaxial tests were performed. Effective compressive stresses of 50 kPa, 100 kPa, and 200 kPa were used for the undrained triaxial tests. It was found that the critical state line was not unique for the tested compounds. The threshold value for the fineness determined using the Ueda model varied from 19.7% to 24.3%. The maximum effective friction angle was observed for the transition fines content. The Alfred packing model proved to be a good tool for determining the fines content that gives the highest effective friction angle for the critical condition. The results show that the size distribution of sand and fines significantly affects the transition fines content. This work also proposes the application of a topological hypothesis (TH) to the phase transitions of soil mixtures. Considerable changes in the topology of the mixtures are found, confirming the transitional behaviour. Finally, the concept of critical states is discussed from a topological point of view as the state of maximum entropy.