ABSTRACT The liquid limit (LL) is an important parameter for soil classification systems. The use of the cone penetrometer technique for measuring the liquid limit is an attractive alternative method since the percussion method is highly operator dependent. In this article, the importance of specifying the procedure and equipment used to determine the LL of a clay soil is highlighted using LL test results conducted on different clay soils. The results of LL, obtained by the percussion method proposed by Casagrande (LLc) and by the penetration cone method (LLp) on clay soils of different geological origins and plasticity were compared. The LLp values were determined using the British cone (20 mm fall cone penetration) method. The LLc values were determined using different hardnesses of Casagrande apparatus. The LL test results show that variations on the investigated methods depend on the mineralogy of the clay soil and the hardness base of the Casagrande cup. The data obtained for kaolinites and illites minerals or low LL soils yielded LLp>LLc. The results obtained for smectite minerals or soils with high LL values indicated LLp<LLc and a greater dispersion among the results. Statistical analyses of residues show that empirical LLp-LLc correlations through a linear regression analysis should be used with caution.

A forma dos grãos tem importante papel na avaliação da distribuição granulométrica das partículas de um solo. Entretanto, a maioria das técnicas de peneiramento evidencia que os grãos são esféricos e descritos por um único parâmetro, o diâmetro. Este trabalho teve por objetivo estudar a aplicação da análise de imagens, aliada ao grau de esfericidade e à teoria dos fractais, como ferramenta para mensurar parâmetros de forma e textura superficial de duas areias de características supostamente distintas da região da Grande Vitória, Espírito Santo, Brasil. Os resultados dos parâmetros de forma e textura superficial das amostras são apresentados e discutidos. As análises dos resultados para a variável esfericidade mostram diferenças estatísticas significativas entre as duas areias de origens diferentes. A areia de jazida de cordão litorâneo (AJ) apresentou grau de esfericidade ligeiramente superior e textura superficial mais lisa do que a de rio (AR), indicando que as areias AJ sofreram maior intemperismo em razão do transporte.

The Shape of sand grains plays an important role in evaluation of soil particle size distribution. However, in most sieving techniques it is assumed that grains are spherical and can be described by a single parameter, diameter. Moreover, the subjectivity of the tests used to estimate sand roughness makes it difficult to obtain data that accurately represent reality. The aim of this paper was to study the use of image analysis together with the degree of sphericity and fractal theory as a tool to measure the textural parameters of the shape and surface texture of two types of quartz sands with supposedly distinct characteristics from the region of Vitória, Espírito Santo, Brazil. The results of the shape and surface texture parameters of the samples are presented and discussed. Statistical analyses of the results for the sphericity variable showed significant statistical differences between the two sands of different origins. The results show that river sands (RS), though having been subjected to a greater degree of transport and attrition, do not have a greater degree of roundness and a smoother surface texture than sands from the coastal spit (BS). The values obtained in the test were statistically analyzed, and again it was confirmed that the sand of the BS has a slightly greater sphericity and smoother surface texture than that of the RS, indicating that the BS sands underwent greater weathering due to transport.