Elastoplastic damage modeling of desaturation and resaturation in argillites

Abstract

SUMMARYThe development of a coupled elastoplastic damage constitutive model for argillites is presented. Emphasis is put on the description of post-failure and coupled hydromechanical behavior of argillites during the desaturation/resaturation processes. A short summary of experimental investigations is given in the first part, which shows an important plastic deformation coupled with damage and a significant influence of water content on the mechanical behavior of argillites. Based on the framework of poroplasticity and continuum damage mechanics, a general constitutive model is proposed for the poromechanical behavior of argillites in both saturated and unsaturated conditions. Main features observed in experiments are taken into account, in particular the elastic degradation due to microcracks, residual strength, coupling between plastic deformation and induced damage, influence of water content on plastic flow, variation of permeability induced by microcracks as well as the deformation generated in the desaturation/resaturation processes. The performance of the model is examined by comparing numerical simulations with test data in representative load paths. Finally, the model is applied to hydromechanical coupling study of four time-dependent tests subjected to a step change in relative humidity.

About the effect of relative humidity on the indentation response of Meuse/Haute–Marne argillite

“…7 and 8. A quasi-linear decrease in the drained modulus (between 2,500 and 6,500 MPa) with the relative humidity is observed; this decrease in mechanical strength was also observed on the same material in [16]. The internal friction angle is about 10 degrees.…”

“…According to [16], the decrease in the Young's modulus caused by the increase in relative humidity may have several origins: microcracks, coupling between plastic deformation and damage, permeability induced by microcracks, deformation generated in the desaturation/resaturation. Based on these observations, further micromechanical investigations are in progress in our group to follow the promising approach presented in [22,23].…”

An Elastoplastic Model for Partially Saturated Collapsible Rocks

“…Laboratory tests conducted on chalks have demonstrated that the mechanical strength of rocks is reduced under high-moisture conditions (Taibi et al 2009;Schroeder et al 1998). Other experimental results also show that there is a strong correlation between relative fluid saturation and mechanical behavior such as pore collapse, yielding, plasticity, and failure (Bell et al 1990;Talesnick et al 2001;Duperret et al 2005;Brignoli and Sartori 1993;Papamichos et al 1997;Jia et al 2010).…”

Study on the Elastoplastic Damage-Healing Coupled Constitutive Model of Mudstone

“…0 and are the initial yield threshold and final plastic hardening value. The plastic flow rule is determined by plastic potential, and the mudstone plastic potential function proposed by Jia et al [17] is modified to be…”

“…The initial yield threshold 0 is determined through initial yield surface, while is acquired by fitting the peak strength. The turning point between compression and dilatation, , is ascertained by the stress point in triaxial test where volumetric strain ratėV is equal to 0 [17].…”