In situ determination of engineering properties of soil

A response surface methodology which employs an orthogonal regression technique and a third-order correction was used to determine in situ engineering properties of an untilled and a tilled Yolo loam soil. The technique employed an elasto-plastic constitutive material model for soil with Drucker Prager yield criterion. The plate sinkage test results using a 101.6 mm circular plate were used to estimate five engineering properties of soil (logarithmic unloading and reloading bulk modulus κ; Poisson's ratio ν; yield surface shape factor K; cohesion c; and soil internal friction angle φ). Although the parameters estimated from 101.6 mm plate tests could predict the sinkage of this plate accurately, use of these values underpredicted the sinkage characteristics of a 50.8 mm diameter plate, perhaps due to the edge effect. These results indicate the need for interface elements to properly model the edge effects that occur in plate sinkage tests. Alternatively, the use of large-diameter plates may reduce the edge effects.