Prediction of resilient modulus with consistency index for fine-grained soils

It is crucial to accurately predict the resilient modulus of subgrade soils. The modulus is influenced by a soil's properties, as characterised by the soil's moisture index values. Thus, it may be feasible to predict resilient modulus based on the soil index. Consistency index, as one of the common soil indices, incorporates plasticity index and moisture content. Therefore, this study aims to establish its relationship with resilient modulus. By collecting and analysing the previous testing results, it is found that resilient modulus was well correlated and increased with consistency index. Two prediction models, a consistency index model and a modified consistency index model, were also proposed to evaluate the resilient modulus of 15 soils with plasticity indices ranging from 6 to 52 at various moisture contents. Model parameters of the consistency index model were estimated from the plasticity index and exhibited excellent correlation. The modified consistency index model incorporated stress states to predict resilient modulus. The models were validated using selected testing results. Despite some limitations, it proves reasonable as a simple alternative means to determine the resilient modulus of fine-grained soils for foundation design, in place of complex resilient modulus testing.