Abstract: Stress history of soft soil analyzed by in-situ test technology can avoid the structural disturbance of soils during sampling and laboratory experiments, and better reflect their real property. Traditional overconsolidation ratio (OCR) calculation methods of cone penetration test with pore pressure measurement (CPTU) technology are mainly based on overconsolidated soils and lack consideration of those soils under the condition of underconsolidated state. Therefore, it shows certain limitations in practical application. Based on literature review, a consolidation state evaluation method is introduced in detail. First, the in-situ initial pore pressure is deduced through final part of the incomplete pore pressure dissipation test curve together with the extrapolation method of inverse time square root of time. It means that there exists inherent pore pressure if the initial pore pressure is greater than hydrostatic pressure; and the soil is underconsolidated. Then, the degree of underconsolidation of soft soil can be quantitatively evaluated by calculating the parameter of consolidation state. Engineering application indicates that the method is not only reasonable but feasible, and can be widely used without limitation of soil property and region. The method can effectively determine the consolidation degree of soft soil without any laboratory consolidation test. The research achievement is instructive for reasonable engineering property assessment of underconsolidated soft soils.

Key words: piezocone penetration test (CPTU), dissipation test, inherent pore pressure, parameter of consolidation state