Cyclic stress–strain response of compacted gravel

Abstract

The positive effect of artificial densification on the stress-strain performance of granular materials is acknowledged from very ancient times but its importance greatly increased after the development of powerful machineries for the construction of large earth and rockfill dams. It is, however, pointed out that the extensive exploitation of gravelly soil is rarely supported by a thorough analytical assessment of the compaction effects on the constitutive relationships of materials, as would be desirable considering the massive dimension of these works and the complexity of typical loading conditions. The present research aims to fill this gap by means of a detailed experimental investigation and a theoretical analysis on the stress-strain response of dense gravels under monotonic and cyclic loading. The experimental campaign consists of a large number of triaxial tests performed at different initial mean effective stresses, following different stress paths and sequences, on artificially reconstituted samples of large dimensions compacted at different initial densities. The great care placed in the accuracy of laboratory instrumentation enables a high repeatability of experimental results, which is necessary to provide a clear focus on non-linearity in the limited strain range of the pre-failure response of the gravel. Based on the curve-fitting method the ingredients of an elasto-plastic constitutive model have been defined to predict the response of gravel under monotonic and cyclic loading. Elastic stiffness is simulated with a model derived from the literature which assumes a dependency on soil density together with inherent and stress-induced anisotropy. Plastic strain development from different initial stress and volume states of gravel is simulated by a critical state, multiple yielding constitutive model. Hardening and flow rules for the latter have been obtained by modifying previously existing laws in order better to reproduce the observations under monotonic compression, extension and cyclic loading. Validation of the proposed model is finally provided by comparing simulations and experimental results in a variety of testing conditions.

The Relationship between InSAR Coseismic Deformation and Earthquake-Induced Landslides Associated with the 2017 Mw 3.9 Ischia (Italy) Earthquake

“…The assumed simplified rigid-block analysis does not allow quantifying accurately the amplitude of the earthquake-induced landslide movements; this is the reason why we normalized the computed displacement values. Indeed, estimating earthquake-induced displacements requires: (i) a detailed geological and geotechnical characterization of the outcropping lithologies; (ii) a rheological model accounting for the complex elastic-plastic behavior of soils subjected to cyclic loads [52,53]; (iii) a proper characterization of the seismic load. The performed analysis is adequate for the required target, i.e., the identification of areas potentially affected by earthquake-induced landslides at a regional scale.…”

The influence of rubber crumbs on the critical state behavior of waste mixtures

“…This method of extrapolation to determine the critical state parameters of a fine granular material (tailings) was vividly described by Carrera et al [14] and by Modoni et al [15] for compacted gravel, and subsequently extended to coarse granular materials (ballast) by Indraratna et al [16]. Fig.…”

“…Two components can be distinctly considered in the total work, i.e. volumetric and deviatoric components, and by decoupling these two components, the increment of work applied onto the sample can be determined by [15]:…”

Assessment of the seismic performance of a bituminous faced rockfill dam

“…It is finally pointed out that the constitutive model adopted for the rockfill embankment does not reproduce the coupling between volumetric and distortional strains before failure and thus the estimated settlements and strains could be underestimated as they do not include the accumulation of volume strains typically produced by cyclic loading on gravelly soils [27]. It must be however noticed that most of the deformation is concentrated in the upper portion in the embankment (Figs.10 and 12), i.e.…”

“…With regard to the second issue, former studies highlight the fundamental role of the seismic input [25], the nonlinear, irreversible, stress dependent behavior of the materials [26,27], the geometry of the embankment [28] and the interaction among the different components [29,20].…”