Effects of Soil Properties and Operational Variables on the Compactibility of a Sandy Loam Soil

Abstract

The evaluation of an empirical equation for the determination of degree of compaction of a sandy loam soil was carried out using seven soil physical properties and four compaction operational variables. The soil used was obtained from a borrow pit in Gombe. Five levels of compactive effort, E/A, using a drop-weight type compactor varying from 107.91 to 539.55 Nm was used to compact each of seven pairs of embankment and slice thicknesses (Z, z respectively) with Z varying from 210 to 450 mm and z from 30 to 210 mm. The developed empirical equation, π₁ = Gπ₂^k in which π1 is the dimensionless degree of compaction and π₂ is a dimensionless combination of the soil properties and the compaction operational variables, has a very high coefficient of determination, r² varying from 98.8% to 98.9%. G and k are each polynomial functions of compactive effort per loading, e_L. that is, G = α_Ge_L²+β_G e_L + λ_G and k=α_ke_L²+β_ke_L+ λ_k. The values of the respective α, β and λ are highly statistically significant at 99.95 confidence level. The “dependent” variables (G and k) are highly correlated at 99.95% confidence level of statistical significance with the “independent” variable (e_L). The multivariate expression of the degree of compaction obtained in this study shows that compaction depends, not only on cumulative compactive effort, E/A, but also on the compactive effort per loading (e_L), embankment and slice thicknesses (Z and z respectively) as well as on easy-to-measure soil properties (i.e. soil texture, soil uniformity coefficient, antecedent soil moisture and antecedent bulk density).