Aplicação de modelos de ajustes de curvas características solo água em solos tropicais

Abstract

The characteristic curve soil water is an important property of the soil that allows hydraulic analyzes, particle-size analysis and other properties related to the structural arrangement. The curve adjustment is necessary for obtaining parameters that allow your application in the various geotechnical, agrarian and environmental solutions (t.i. air entrance value, residual saturation etc). In the literature, there are several adjustment models, each one with its parameters and variables appropriate for the type of soil and behavior which gave it origin. Most of these models were developed based on soils formed in temperate regions and therefore do not result in good adjustment for soils of tropical regions, especially those with high degree of weathering. Two tropical soils located in two different regions of Brazil, Goiás and Santa Catarina were used for this study. Through the laboratory tests to characterize and determine the characteristic curve soil water, the soils had their behavior compared. The characteristic curves were obtained by means of the filter paper test performed by two authors, Feuerharmel (2007) - Santa Catarina soil - and Araujo (2010) - Goiás soil. From these tests, it was observed that the obtained curves have bimodal behavior in which the first stretch is defined by the macropores, then it is verified the existence of a plateau and, finally, the third stretch is defined by the micropores. This type of behavior is very common in tropical soils highly weathered. The application of three adjustment models, Brooks and Corey (1964), Van Genuchten (1980) and Gitirana Jr. and Fredlund (2004), showed that only the last one, developed for tropical soils, resulted in a good adjustment allowing the obtaining of a parameter which define the hydraulic behavior of the soil, such as air entrance value and residual saturation of macro and micropores.