Discussion on overconsolidation ratio for underconsolidated soils

Underconsolidated soil is the soil that has not finished consolidation under its self-weight. At present, there are two types of overconsolidation ratio for underconsolidated soil in literature, i.e., equal to 1 and less than 1 respectively, which may cause confusion or misusing problems. We have sorted out the relevant contents of overconsolidation ratio in the widely used soil mechanics textbooks and found that there are two different definitions for overconsolidation ratio, where the different denominators result in the difference of overconsolidation ratio for underconsolidated soil. Using knowledge graph method, we comprehensively analyze the conceptual meaning, historical origin and practical applications for overconsolidation ratio and underconsolidated soil. Results show that degree of consolidation or consolidation state parameters can be used as substitution for overconsolidation ratio while involved in the problems related to underconsolidated soil. Overconsolidation ratio should be defined as the ratio of preconsolidation stress to existing effective stress (OCR = p(c)/p '(c) is the effective consolidation pressure in the early stage, g is the vertical effective stress), which is consistent with the influence mechanism of stress history on soil behavior, as well as the historical origin meaning of the concept.