Effect of Soil Moisture, Soil Density, and Cone Penetrometer Material on Finite Element Prediction of Soil Hardpan Depth

Abstract

An accurate soil hardpan determination is important for maximum precision tillageperformance. Soil cone penetrometer data are often analyzed to predict soil hardpan depths. Theprediction in layered soils may be limited due to the complexity of soil reaction to cone penetration.An axisymmetric finite element (FE) model was developed to investigate soil hardpan predictions andsoil deformation failures on layered Norfolk sandy loam soil. The soil was considered as a non-linearelastic-plastic material modeled using a constitutive relationship from Drucker-Prager model with theHardening option in ABAQUS, a commercially available FE package. ABAQUS/Explicit was used tosolve the simulation of soil-cone contact pair interaction using a frictional property. The resultsshowed that the FE model captured the soil cone penetration trend in layered soil with two deflectionpoints indicating the start of the hardpan and the peak cone penetration resistance. The FE modelpredicted hardpan depth (8.62 cm) was smaller than the cone penetrometer predicted depth (11.03cm). Soil moisture, bulk density and cone material significantly affected the FE and conepenetrometer predicted soil hardpan depths. The simulation also showed soil deformation zonesabout 3 times the diameter of the cone developed around the advancing cone.