Viscosity and secondary consolidation in one-dimensional loading

Abstract

Viscosity and secondary consolidation effects are observed in one-dimensional compression, but it remains unresolved if viscous effects occur during the primary consolidation phase and consequently whether the end of the primary consolidation (EOP) line is unique and the H2 scaling law applies. Dynamical systems soil mechanics suggests that viscosity and secondary consolidation each have a separate physical basis. Viscous behaviour is due to strain rate dependence of the coefficients of friction at interparticle contacts as they slide against each other in simple friction, and occurs during both primary consolidation and secondary consolidation. Secondary consolidation is the continued deformation of the soil structure after excess pore pressure has dissipated, as small numbers of particles move at random shear strains, in a Poisson process, to new final positions. The near constant C(αe)/Cc ratio is due to the form of the equation that expresses this ratio and because very few particles move to new positions during secondary consolidation. Strain rates for typical geotechnical problems being pseudo-static, viscous effects in the field are small, and the current design practice of using the EOP curve and C(αe) to calculate compression settlements appears reasonable. Empirical evidence suggests that adsorbed water layers control strain-rate-related effects.

An experimental investigation of the influence of plasticity on creep degradation rate

“…Some suggest that viscous behaviour occurs during and after primary consolidation in accordance with Creep Hypothesis B, formally proposed by Ladd et al [42]. Creep deformation occurs because of the breakdown of interparticle bonds [46,48], jumping of the molecule bonds [41,49], sliding among particles [39], double porosity [63,75] and the strain rate dependence of the coefficients of friction at the interparticle contacts [34,35]. The Creep Hypothesis B is referred to as the isotache theory, in which the strain at EOP increases with the thickness of the clay and leads to unique secondary compression [14-18, 24, 36, 44, 60, 65, 71].…”

Experimental insights into consolidation rates during one-dimensional loading with special reference to excess pore water pressure

“…In this work, it is assumed that creep is a process in which the deformation of soil will occur as a function of time and that the creep rate is controlled by viscous resistance [19]. Joseph [25] studied the viscous and secondary consolidation phenomena to understand their physical mechanisms using the Dynamical Systems Theory [26]. Suggestion was made that viscous behaviour occurs both during and after primary consolidation in accordance with Creep Hypothesis B and is due to the strain rate dependence of the coefficients of friction at interparticle contacts.…”

“…This view is referred to as the isotache theory in which the strain at EOP consolidation increases with the thickness of the clay and leads to unique secondary compression behaviour [12,13,18,19,35,37,72,81,82]. According to Joseph [25], secondary compression is the continued deformation (after completion of dissipation of the excess pore water pressure) of the soil structure after consolidation due to the small numbers of particles moving at random shear strains, in a Poisson process, to the new final positions. Based on Hypothesis B, many different elastic viscoplastic (EVP) constitutive models have been used to calculate consolidation settlements of soft soil ground [71,73,[76][77][78]83].…”

Determination of quasi-filtration phase of consolidation based on experimental and theoretical course of the uniaxial deformation and distribution of pore pressure

“…This mechanism describes the reaction of particles to one-dimensional loading and results from the friction on the contact surfaces of strain-bearing particles. -The Poisson process occurs during one-directional consolidation (Joseph 2013(Joseph , 2014a(Joseph , 2014b) -particle movement during one-directional consolidation, approaching a set structure pseudo-flow state with random shearing deformations. -In the case of low permeability soils, the stabilization of the dispersion of excessive pore pressure is observed before its complete dissipation.…”