Theoretical investigation of the time-dependent behaviour of rockfill

Abstract

Long-term strain records obtained in large-diameter oedometer tests on compacted gravels demonstrated that strains could be linearly related with the logarithm of time. Delayed compressibility coefficients were found proportional to the conventional stress-induced compressibility coefficients. A framework rooted on the phenomenon of crack propagation in rock particles induced by stress corrosion mechanisms is adopted to explain macroscopic observations. A model of crack propagation in loaded disc-shaped particles has been developed in order to explain the nature of particle breakage and its relationship with time, macroscopic stress and total suction. Experimental observations such as the existence of threshold stresses that mark the onset of delayed deformations are explained by the model. It was also found that the main features of the delayed deformation of rockfill could be physically explained within the developed framework. In particular, a simple closed-form relationship between the coefficient of delayed deformation, the compressibility coefficient and a parameter describing the rate of crack propagation could be found. It was found to be consistent with experimental observations.

Static Fatigue Controls Particle Crushing and Time Effects in Granular Materials

“…Thus, the pH in the humid environment as well as the presence of other chemical components near the crack tips may serve to increase the speed of stress corrosion (Wiederhorn, 1975). Oldecop and Alonso (2007) investigated the eŠect of water on the time-dependent behavior of rockˆll and they found that the settlement of rockˆll dams with time could be understood in terms of the water-enhanced static fatigue of the rockˆll.…”

Degradation of Compacted Marls: A Microstructural Investigation

“…proposed by Oldecop and Alonso (2007), where de is the strain increment and t the time measured at each loading step. The values obtained for some of tests performed on compacted marls are presented in Fig.…”

Effects of Particle Characteristics on the Viscous Properties of Granular Materials in Shear

“…Unbound granular materials (unbound GMs) (e.g., unbound sands and gravels) may exhibit signiˆcant ratedependent behaviour (including signiˆcant creep deformation) inˆeld full-scale cases (e.g., Tatsuoka et al, 2000Tatsuoka et al, , 2001; Jardine et al, 2005Jardine et al, , 2006; Oldecop and Alonso, 2007). A number of laboratory stress-strain tests showed that unbound GMs have signiˆcant viscous properties and their trend is similar to that of saturated clays and bound materials (i.e., sedimentary soft rocks and cement-mixed soils) (e.g., Yamamuro among many others).…”