Callovo-Oxfordian(COx)claystone has been considered as a potential host rock for geological radioactive waste disposal in France(Cigéo project).During the exploitation phase(100 years),the stability of drifts(e.g...Callovo-Oxfordian(COx)claystone has been considered as a potential host rock for geological radioactive waste disposal in France(Cigéo project).During the exploitation phase(100 years),the stability of drifts(e.g.galleries/alveoli)within the disposal is assured by the liner,which includes two layers:concrete arch segment and compressible material.The latter exhibits a significant deformation capacity(about 50%)under low stress(<3 MPa).Although the response of these underground structures can be governed by complex thermo-hydro-mechanical coupling,the creep behavior of COx claystone has been considered as the main factor controlling the increase of stress state in the concrete liner and hence the long-term stability of drifts.Therefore,by focusing only on the purely mechanical behavior,this study aims at investigating the uncertainty effect of the COx claystone time-dependent properties on the stability of an alveolus of Cigéo during the exploitation period.To describe the creep behavior of COx claystone,we use Lemaitre’s viscoplastic model with three parameters whose uncertainties are identified from laboratory creep tests.For the reliability analysis,an extension of a well-known Kriging metamodeling technique is proposed to assess the exceedance probability of acceptable stress in the concrete liner of the alveolus.The open-source code Code_Aster is chosen for the direct numerical evaluations of the performance function.The Kriging-based reliability analysis elucidates the effect of the uncertainty of COx claystone on the long-term stability of the concrete liner.Moreover,the role of the compressible material layer between the concrete liner and the host rock is also highlighted.展开更多
In geotechnical engineering,modeling geo-structures is challenging,particularly in cases where the interaction between the structures and soil or rock is complex.Most wellknown commercial modeling software is based on...In geotechnical engineering,modeling geo-structures is challenging,particularly in cases where the interaction between the structures and soil or rock is complex.Most wellknown commercial modeling software is based on homogenous and isotropic materials.However,soil and rock are often modeled in heterogeneous and anisotropic media because of the inherent anisotropy of sedimentary rock masses and their stratified structure.In recent decades,coupled hydro-mechanical(HM)interactions in isotropic porous media have been studied;however,the behavior of transversely isotropic porous media is rarely considered.In addition,it is difficult for commercial software such as Plaxis and Flac3D to express complex rock formation where the anisotropy of the material and the associated cracks and fractures could be assembled into a single model.In this study,a finite element implementation using Differential Equation Analysis Library(DEAL.II),an open-source library of finite element codes,was developed to model the fully coupled HM behavior of transversely isotropic porous media.The proposed implementation can be applied to both isotropic and transversely isotropic porous media based on Biot’s theory.The developed code can be used to model poroelastic media with(1)equations of linear elasticity for the solid matrix and(2)diffusion equations for fluid flow based on mass and linear-momentum conservation laws.We verified the performance and accuracy of the code through two examples,i.e.,Mandel’s problem with a compared analytical solution and a tunnel excavation process with the Flac3D software.On the basis of these numerical applications,we present the code to model the behavior of various geo-structures such as tunnels and pile–soil interactions with anisotropic materials.展开更多
文摘Callovo-Oxfordian(COx)claystone has been considered as a potential host rock for geological radioactive waste disposal in France(Cigéo project).During the exploitation phase(100 years),the stability of drifts(e.g.galleries/alveoli)within the disposal is assured by the liner,which includes two layers:concrete arch segment and compressible material.The latter exhibits a significant deformation capacity(about 50%)under low stress(<3 MPa).Although the response of these underground structures can be governed by complex thermo-hydro-mechanical coupling,the creep behavior of COx claystone has been considered as the main factor controlling the increase of stress state in the concrete liner and hence the long-term stability of drifts.Therefore,by focusing only on the purely mechanical behavior,this study aims at investigating the uncertainty effect of the COx claystone time-dependent properties on the stability of an alveolus of Cigéo during the exploitation period.To describe the creep behavior of COx claystone,we use Lemaitre’s viscoplastic model with three parameters whose uncertainties are identified from laboratory creep tests.For the reliability analysis,an extension of a well-known Kriging metamodeling technique is proposed to assess the exceedance probability of acceptable stress in the concrete liner of the alveolus.The open-source code Code_Aster is chosen for the direct numerical evaluations of the performance function.The Kriging-based reliability analysis elucidates the effect of the uncertainty of COx claystone on the long-term stability of the concrete liner.Moreover,the role of the compressible material layer between the concrete liner and the host rock is also highlighted.
文摘In geotechnical engineering,modeling geo-structures is challenging,particularly in cases where the interaction between the structures and soil or rock is complex.Most wellknown commercial modeling software is based on homogenous and isotropic materials.However,soil and rock are often modeled in heterogeneous and anisotropic media because of the inherent anisotropy of sedimentary rock masses and their stratified structure.In recent decades,coupled hydro-mechanical(HM)interactions in isotropic porous media have been studied;however,the behavior of transversely isotropic porous media is rarely considered.In addition,it is difficult for commercial software such as Plaxis and Flac3D to express complex rock formation where the anisotropy of the material and the associated cracks and fractures could be assembled into a single model.In this study,a finite element implementation using Differential Equation Analysis Library(DEAL.II),an open-source library of finite element codes,was developed to model the fully coupled HM behavior of transversely isotropic porous media.The proposed implementation can be applied to both isotropic and transversely isotropic porous media based on Biot’s theory.The developed code can be used to model poroelastic media with(1)equations of linear elasticity for the solid matrix and(2)diffusion equations for fluid flow based on mass and linear-momentum conservation laws.We verified the performance and accuracy of the code through two examples,i.e.,Mandel’s problem with a compared analytical solution and a tunnel excavation process with the Flac3D software.On the basis of these numerical applications,we present the code to model the behavior of various geo-structures such as tunnels and pile–soil interactions with anisotropic materials.
