Robert L. Kondner

Correlation of Creep and Dynamic Response of a Cohesive Soil

The static and dynamic response of a cohesive soil tested in uniaxial compression is formulated in terms of a response spectra. The stress-strain-time behavior of the soil is definitely nonlinear; however, the concept of a compliance function is employed to represent the response over nine decades of time. The experimental data within this range of the time spectrum are obtained from an extensive series of transient (creep) and steady-state (vibratory) tests. The compliance function representation of the response is presented in terms of the Gauss Error Integral. This integral gives a quantitative form of nonlinear constitutive equation for the cohesive soil and offers a unified presentation of quasi-static and dynamic response characteristics by a single phenomenological expression. Moisture content variations are taken into account by normalizing the response with respect to a strength-consistency index. The ratio of the stress level to the strength-consistency index (stress-strength parameter) is included as one of the arguments in the definition of the compliance function. This is necessary for generality, not only because of moisture content variations, but also because of the nonlinearity of the soil response. The nonlinearity is handled by reducing the response to a constant stress level which can be approximated by linear theory. The stress level considered is the special case where the applied stress vanishes. Such a condition represents the limiting magnitude of the compliance function as the applied stress approaches zero and provides a convenient datum from which the stress dependence of the compliance function is ultimately developed.

Creep compliance response of a cohesive soil

Abstract The creep response of a cohesive soil tested in uniaxial compression is presented in terms of a creep compliance function. The variables considered include strain, time, stress level, and moisture content. The soil response is definitely nonlinear, but the stress dependence of the creep compliance is written in explicit form. Variations in moisture content are handled by normalizing the response with respect to the unconfined compressive strength as a consistency index. The compliance method of response representation is related to theoretical aspects of the viscoelasticity of cohesive soils. Nonlinear aspects of soil response are discussed.