ASABE Technical Library - Abstract

Abstract. Reliable prediction of soil properties under in-situ field conditions is critical for the design of traction devices of off-road vehicles. The goal of this research is to develop an inverse solution technique to determine in-situ engineering properties of soil for use in mobility and traction studies. The methodology involves integration of response surface methodology (RSM) with finite element analysis (FEA) for inverse solution of in-situ properties of soil in conjunction with limited experimental measurements. The nonlinear elastoplastic behavior of soil was characterized by a complex six-parameter constitutive model —— two elastic parameters (i.e., bulk modulus, K and the Poisson‘s ratio, υ), three plastic parameters (i.e., angle of internal friction, φ; cohesion, c and soil hardening parameter, λ), and one soil physical condition parameter (i.e. initial void ratio, e*). Soil failure was represented by the Durcker-Prager yield criterion and associated flow rule. LS-DYNA FEM software package was used to model the soil-cone interaction problem. An interface element and erosion criteria based on volumetric strain were used to model this cone penetration problem. FEM simulations were conducted for a set of soil properties properly selected within the defined parameter space. The soil penetration force displacement curves could be represented by two piecewise smooth functions - a parabola followed by a straight line, very well after the data were smoothed by a moving window filter. The coefficients of these two curves were used to create fourth order response surfaces using a stepwise multiple linear regression technique. The adequacy of the response surface model was validated by evaluating the model at randomly selected soil parameter values within the response surface parameter space. The values of cohesion and soil hardening parameter were predicted for each curve of calibration set and validation set using a search algorithm. The results showed both the value of soil cohesion and soil hardening parameter could be predicted using the soil penetration force displacement curve.