Assessing the strength of stabilized soils using non-linear failure envelop

Enzymes as soil stabilizers are used extensively in road construction. Recently reported studies on soil stabilization reveal consistent road improvements and better performance in enzyme-treated soil compared to non-treated soils. Successful application of enzymes in road construction reported in many countries including India, Malaysia, China and western USA. An important design parameter of these road constructions is the strength of stabilized soil mix. The assessment of the stabilized soil strength in current practice is either based on enzyme specific standards or site specific soil laboratory experiments. However, the response of the road performance during live traffic can be substantially different from such sample/standard based strength predictions. This could be mainly due to the misinterpretation of stabilized soil strength which in reality bounds within non-linear strength envelop in contrast to linear response assumed in current design practice. The current study investigates a methodology to implement non-linear increase in strength prediction of stabilized material due to addition of chemicals/enzymes. Experimentally observed non-linear strength response of stabilized soil mix has been implemented into commercial finite element (FE) program through FORTRAN based user subroutine. Having validated the model for different stress paths on the basis of published data in literature, 3-D FE analyses were conducted to predict the response of an unbound pavement under traffic loads. The results showed that the response of stabilized road pavements using realistic non-linear strength envelops is substantially different from the traditional pavement response predictions. Thus, the implemented model will allow more realistic assessments of enzyme contribution during design than are currently used.