Proposal of a revision scale of the degree of cohesion and tensile strength to aid in the diagnosis of the cohesive character in soils

Abstract

This study aimed to establish reference values for tensile strength (TS) to aid the diagnosis of the cohesive character of soils. The hypotheses were: i) the subjectivity leads to variability in the human perception in the qualitative assessment of the cohesive character; ii) it is possible to develop a TS scale that aids in the quantification and diagnosis of the cohesive character. Three evaluators measured the aggregates/clods’ tensile strength using TS-Soil equipment. An electronic dynamometer was used as a control group, using a completely randomized design. The data were analyzed using statistical tests and regression analysis. Additionally, the values assigned in the qualitative evaluation of consistency by the evaluators were related to the tensile strength data. When comparing the means of the evaluators, who used the TS-Soil equipment to quantify the TS of aggregates/clods, with the electronic dynamometer (standard equipment) using the Dunnett test, no significant differences were found in 70 % of the comparisons for horizons with cohesive character and 57 % for horizons without cohesive character. The threshold for diagnosing the cohesive character was set at a TS value 66 kPa (very hard consistency). A significant number of scores were associated with hard consistency (40≤ TS_kPa <66). The study concluded that there is variability in the qualitative assessment of cohesive character and that a TS scale can be useful in quantification and diagnosis. Furthermore, it highlighted the importance of considering a moderate degree of cohesion in taxonomic systems when diagnosing cohesive character. The academic contribution of this study materializes as soil taxonomic systems begin to incorporate quantitative criteria in the diagnosis of cohesive character in soils. As for practical applications, the use of the cohesion degree scale allows the pedologist to recognize the cohesive character in soils more assertively.