Fundamental yet simplified model for liquefaction instability

Abstract

SUMMARYA fundamental procedure is proposed for the identification of liquefaction in saturated soils based on the instability in the material's microstructure. The disturbed state concept (DSC) provides a unified constitutive model for the characterization of entire stress-strain behaviour under cyclic loading, and the values of disturbance at threshold states in the deforming microstructure provides the basis for the identification of liquefaction. The procedure is verified with respect to laboratory behaviour of two sands, saturated Ottawa and Reid Bedford. A mathematical analysis of the DSC constitutive matrix is also performed. Procedures for the application of the DSC for simplified analysis and design, and in finite element procedures are presented. It is believed that the proposed model can provide a fundamental yet simplified procedure for liquefaction analysis, and as a result, it is considered to be an improvement over the available empirical and energy-based procedures.1998 John Wiley & Sons, Ltd.

Assessment of liquefaction potential based on modified disturbed state concept

“…According to the Disturbed State Concept (DSC) proposed by Desai et al (1998), external forces cause changes and disturbances in the microstructure system of a material. The stressstrain response of the material at a certain loading condition is then determined from the degree of disturbance caused by the external force.…”

“…Several soil models have been used for describing undrained behaviors of fully saturated sands under dynamic loading conditions (Finn et al, 1977;Iai et al, 1992;Desai and Ma, 1992;Desai et al, 1998). Representative examples are those of Finn et al (1977), Iai et al (1992), and Desai et al (1998), all of which are based on the effective stress concept.…”

“…Representative examples are those of Finn et al (1977), Iai et al (1992), and Desai et al (1998), all of which are based on the effective stress concept. According to Finn et al (1977), mobilized excess pore pressures under undrained conditions can be determined as a function of drained volumetric strains.…”

“…Desai (1980) introduced the Disturbed State Concept (DSC) in order to characterize the relationship between work-hardening behaviors of over-consolidated soils and those of normally consolidated soils. Subsequently, further development has been made for the description of undrained behaviors for saturated sands (Desai and Ma, 1992;Desai et al, 1991Desai et al, , 1998Katti and Desai, 1994;Desai and Toth, 1996;Desai and Rigby, 1997;Park, 1997;Choi, 2002). In the DSC model (Desai and Ma, 1992;Desai et al, 1998), dynamic responses of soils are defined as a function of the material disturbance caused by an applied force and induced deviatoric plastic strains.…”

“…Observed responses of the material are then given according to the relative differences between the RI and the FA states, which are quantified through material disturbance. While the DSC model has been successfully verified for many geotechnical dynamic problems (Desai et al, , 1998Desai and Toth, 1996;Desai and Rigby, 1997;Pal and Wathugala, 1999), these have been primarily for low excess pore water pressure and small-strain conditions. The application to liquefaction has been limited to determination of the initial liquefaction occurrence, and has not been fully implemented for a whole process of liquefaction analysis, including determination of liquefaction potential and factor of safety.…”