Argillaceous rocks are considered ideal host geomaterials for deep geological disposal of radioactive waste due to their low permeability,notable sorption capacity,low diffusion coefficient,limited natural fracturing,...Argillaceous rocks are considered ideal host geomaterials for deep geological disposal of radioactive waste due to their low permeability,notable sorption capacity,low diffusion coefficient,limited natural fracturing,and capacity for self-sealing.In line with this objective,substantial efforts have been made in the literature over the past decades to model their behavior numerically.Yet,accurately modeling the hydromechanical behavior of argillaceous rocks remains a significant challenge in geomechanics,highlighting the need for further research.Despite the wide variety of geomaterials in this class,common behavioral features are observed,such as anisotropy,structural degradation,strain localization,creep,heterogeneity,and self-sealing.This study summarizes these common features observed in laboratory and field settings and reviews the developed approaches for modeling each behavioral aspect.The goal is to establish a comprehensive framework for the practical modeling of these geomaterials,specifically aimed at applications in the geological disposal of radioactive waste.展开更多
This study presents a fully coupled thermo-hydro-mechanical (THM) constitutive model for clay rocks. The model is formulated within the elastic-viscoplasticity framework, which considers nonlinearity and softening aft...This study presents a fully coupled thermo-hydro-mechanical (THM) constitutive model for clay rocks. The model is formulated within the elastic-viscoplasticity framework, which considers nonlinearity and softening after peak strength, anisotropy of stiffness and strength, as well as permeability variation due to damage. In addition, the mechanical properties are coupled with thermal phenomena and accumulated plastic strains. The adopted nonlocal and viscoplastic approaches enhance numerical efficiency and provide the possibility to simulate localization phenomena. The model is validated against experimental data from laboratory tests conducted on Callovo-Oxfordian (COx) claystone samples that are initially unsaturated and under suction. The tests include a thermal phase where the COx specimens are subjected to different temperature increases. A good agreement with experimental data is obtained. In addition, parametric analyses are carried out to investigate the influence of the hydraulic boundary conditions (B.C.) and post-failure behavior models on the THM behavior evolution. It is shown that different drainage conditions affect the thermally induced pore pressures that, in turn, influence the onset of softening. The constitutive model presented constitutes a promising approach for simulating the most important features of the THM behavior of clay rocks. It is a tool with a high potential for application to several relevant case studies, such as thermal fracturing analysis of nuclear waste disposal systems.展开更多
Acoustic waves in the pseudo-triaxial experiment system experience refraction phenomena.The conventional assumption that acoustic waves propagate along a straight line in traditional methods can lead to significant er...Acoustic waves in the pseudo-triaxial experiment system experience refraction phenomena.The conventional assumption that acoustic waves propagate along a straight line in traditional methods can lead to significant errors in localization results.To the end,this paper presents a method for locating acoustic emission(AE)sources in pseudo-triaxial experiments using shortest paths and orthogonal constraints.The approach consists of three main steps:(1)establishing control equations for refraction paths from AE sources to sensor locations;(2)calculating refraction point locations using the shortest travel principle and orthogonal constraints;(3)determining source coordinates using Taylor's first-order expansion.The results from laboratory AE experiments demonstrate that the average localization accuracy of the new method is only 6.5 mm,which is 66%more precise than the accuracy(19.4 mm)of the traditional method.Furthermore,simulation results indicate that the new method is not affected by the refraction ratio of the media and maintains the highest positioning accuracy across various arrival and velocity errors.展开更多
基金financial support of the French National Radioactive Waste Management Agency(Andra)is gratefully acknowledged.
文摘Argillaceous rocks are considered ideal host geomaterials for deep geological disposal of radioactive waste due to their low permeability,notable sorption capacity,low diffusion coefficient,limited natural fracturing,and capacity for self-sealing.In line with this objective,substantial efforts have been made in the literature over the past decades to model their behavior numerically.Yet,accurately modeling the hydromechanical behavior of argillaceous rocks remains a significant challenge in geomechanics,highlighting the need for further research.Despite the wide variety of geomaterials in this class,common behavioral features are observed,such as anisotropy,structural degradation,strain localization,creep,heterogeneity,and self-sealing.This study summarizes these common features observed in laboratory and field settings and reviews the developed approaches for modeling each behavioral aspect.The goal is to establish a comprehensive framework for the practical modeling of these geomaterials,specifically aimed at applications in the geological disposal of radioactive waste.
基金funded by the European Union's Horizon 2020 research and innovation programme under a grant agreement (Grant No.847593)partially supported by the Fundamental Research Funds for the Central Universities (Grant No.22120240029).
文摘This study presents a fully coupled thermo-hydro-mechanical (THM) constitutive model for clay rocks. The model is formulated within the elastic-viscoplasticity framework, which considers nonlinearity and softening after peak strength, anisotropy of stiffness and strength, as well as permeability variation due to damage. In addition, the mechanical properties are coupled with thermal phenomena and accumulated plastic strains. The adopted nonlocal and viscoplastic approaches enhance numerical efficiency and provide the possibility to simulate localization phenomena. The model is validated against experimental data from laboratory tests conducted on Callovo-Oxfordian (COx) claystone samples that are initially unsaturated and under suction. The tests include a thermal phase where the COx specimens are subjected to different temperature increases. A good agreement with experimental data is obtained. In addition, parametric analyses are carried out to investigate the influence of the hydraulic boundary conditions (B.C.) and post-failure behavior models on the THM behavior evolution. It is shown that different drainage conditions affect the thermally induced pore pressures that, in turn, influence the onset of softening. The constitutive model presented constitutes a promising approach for simulating the most important features of the THM behavior of clay rocks. It is a tool with a high potential for application to several relevant case studies, such as thermal fracturing analysis of nuclear waste disposal systems.
基金the financial support provided by the National Key Research and Development Program for Young Scientists(Grant No.2021YFC2900400)the National Natural Science Foundation of China(Grant No.52304123)the China Postdoctoral Science Foundation(Grant No.2023M730412).
文摘Acoustic waves in the pseudo-triaxial experiment system experience refraction phenomena.The conventional assumption that acoustic waves propagate along a straight line in traditional methods can lead to significant errors in localization results.To the end,this paper presents a method for locating acoustic emission(AE)sources in pseudo-triaxial experiments using shortest paths and orthogonal constraints.The approach consists of three main steps:(1)establishing control equations for refraction paths from AE sources to sensor locations;(2)calculating refraction point locations using the shortest travel principle and orthogonal constraints;(3)determining source coordinates using Taylor's first-order expansion.The results from laboratory AE experiments demonstrate that the average localization accuracy of the new method is only 6.5 mm,which is 66%more precise than the accuracy(19.4 mm)of the traditional method.Furthermore,simulation results indicate that the new method is not affected by the refraction ratio of the media and maintains the highest positioning accuracy across various arrival and velocity errors.
