Extension of plasticity theory to debonding, grain dissolution, and chemical damage of calcarenites

2016

Acta Geotech.

Self Cite

In this work, an extended theory of plasticity with generalized hardening is proposed to describe the response of geomaterials under both mechanical and environmental processes, which include as special cases several elastoplastic constitutive equations proposed in the literature to model such processes as desaturation or suction hardening, thermal softening, chemo-mechanical coupling 10 effects in fine-grained soils, as well as weathering of soft rocks. In the formulation of the theory, the coupling between mechanical and environmental processes takes place at two levels: first, as an additional direct contribution to the constitutive stress changes, taking place in both elastic and elastoplastic processes; and, second, as a result of the evolution of the internal state variables induced by changes 15 in the environmental process variables. This last effect is incorporated through a set of generalized hardening rules. As an example of application, the general formulation is specialized to the particular case of weak calcarenite rocks undergoing degradation processes due to plastic deformations, changes in degree of saturation (short-term debonding) and chemical dissolution of the bond material and the solid 20 grains (long-term debonding). The resulting model is implemented in a FE code by means of an implicit Generalized Backward Euler algorithm, suitably modified to incorporate the full formalism of plasticity with generalized hardening. Results of numerical simulations carried out at the element level show the accuracy and efficiency properties of the proposed stress-point algorithm. The simulation of a 25 representative initial-boundary value problem demonstrate the practical relevance of environmental degradation effects in practical applications, over periods of time comparable with the life cycle of most geotechnical structures.

Section: Application To Environmental Degradation Of Calcarenite Rocksmentioning

confidence: 99%

“…The debonding function D d adopted by Ciantia and di Prisco has been obtained by the upscaling of a heuristic micromechanical model for the chemical degradation process at the REV scale, see [10].…”

Section: Environmental Debonding and Damage Functionsmentioning

confidence: 99%

Plasticity with generalized hardening: constitutive modeling and computational aspects

Tamagnini

2016

Acta Geotech.

Self Cite

“…If F(X) in equation (15) is replaced by equation (10), this will imply that a good fit to the UCS data for this material should be obtained using, Indeed, this expression is very close to the optimal fit between UCS and the mixture ratio (n/Civ 0.21 ) previously obtained from laboratory data [21]. This suggests that, at least for preliminary purposes, the relation necessary for bonding initialization can be advantageously deduced from a suite of UCS tests.…”

Section: Discussionmentioning

confidence: 99%

“…It suggests that a more complex state equation than (7) above, perhaps including the other state variable, ps should control bonding degradation. Micromechanical studies or multiscale modelling approaches such as those presented by [10] and [25] respectively, are likely to be useful in this respect.…”

Section: Calibration Of Bonded-soil C-casm Parametersmentioning

confidence: 99%

“…Taking a different perspective, a number of researchers have successfully extended elasto-plastic models for soils of the critical state tradition to represent artificially cemented clays [5] and silts [6]. This approach is directly inspired by a long line of constitutive models originally developed for naturally structured soils and soft rocks ( [7], [8] , [9], [10]) Despite all those developments it is fair to say that simplified, elastic perfectly plastic models (with either a Mohr-Coulomb or Tresca failure criterion) still dominate numerical applications (e.g. [11], [12]).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Simplifying calibration of bonded elasto-plastic models

Rı́os

Computers and Geotechnics

González

et al. 2016

Using realistic constitutive models for artificially cemented soils is advantageous in design. However, the price of that increased realism is often a more elaborate model, which is difficult to calibrate. A database of high quality triaxial tests on compacted cemented silty sand is used to calibrate and validate a generalized critical state bonded soil model. The exercise highlights the staged calibration procedure that is convenient in this kind of application. The calibration results have shown a direct relation between added yield strength and a well-established soil-cement mixture ratio, which facilitates the application of the model in design. It is shown that such relation can be also deduced from the analysis of unconfined compressive strength tests.

A Nonlocal Elasto-Plastic Model for Structured Soils at Large Strains for the Particle Finite Element Method

Monforte

Lecture Notes in Civil Engineering

Carbonell

et al. 2021

This work presents a robust and mesh-independent implementation of an elasto-plastic constitutive model at large strains, appropriate for structured soils, into a Particle Finite Element code specially developed for geotechnical simulations. The constitutive response of structured soils is characterized by softening and, thus, leading to strain localization. Strain localization poses two numerical challenges: mesh dependence of the solution and computability of the solution. The former is mitigated by employing a non-local integral type regularization whereas an Implicit-Explicit integration scheme is used to enhance the computability. The good performance of these techniques is highlighted in the simulation of the cone penetration test in undrained conditions.