Resumo

HOSSNE G, Américo et al. Resistencia terramecánica en función de la  humedad edáfica de un suelo ultisol de sabana del estado Monagas,Venezuela. Bioagro [online]. 2003, vol.15, n.3, pp.173-182. ISSN 1316-3361.

Terramechanic resistance as a function of moisture content of a savanna Ultisol soil in Monagas State, Venezuela It is usual to evaluate the resistance of agricultural soils as a function of compression when measuring the bulk density without making reference of the soil moisture. The shear strength (t ) is the index of the soil resistance due to any load type. Soils resist in an opposite way to their wetness for different values of normal tension on the failure plane according to the Coulomb-Mohr theory. The index of resistance of the agricultural soils is useful to evaluate the tractive requirements of the farm implements, tractors and, probably, the process of root growth. The objectives of this research consisted on evaluating the shear strength at different levels of soil moisture (w) for each normal tension (s ) and the interrelations with the cohesion (C) and the angle of internal friction (f ) of an agricultural soil of savanna. A triaxial apparatus was used to determine t , and a regression analysis to interpret the proportion of the variance among the different parameters. We concluded that the algebraic expression t = - 0.782 w + 1.180 C + 6.745 f - 1.152 was the best for R² adjusted = 1***, that the resistance increases when increasing the normal tension but it is inversely proportional to the soil moisture and tends to zero when the state of the soil comes closer to the liquid limit (around 17% of moisture for the studied savanna soils). This soil shows cohesion regardless its high percentage of sand. The soil moisture was the index that most affected the shear strength while the angle of internal friction influenced more than cohesion on the referred soil resistance

Palavras-chave : Physical implicatios; soil workability; triaxial .