Author List: S. Na, W.C. Sun, H. Yoon, M. Ingraham
Abstract: For assessing energy-related activities in the subsurface, it is important to investigate the impact of the spatial variability and anisotropy on the geomechanical behavior of shale. The Brazilian test, an indirect tensile-splitting method is performed in this work, and the evolution of strain field is obtained using digital image correlation. Experimental results show the significant impact of local heterogeneity and lamination on the crack pattern characteristics. For numerical simulations, a phase field method is used to simulate the brittle fracture behavior under various Brazilian test conditions. In this study, shale is assumed to consist of two constituents including the stiff and soft layers to which the same toughness but different elastic moduli are assigned. Microstructural heterogeneity is simplified to represent mesoscale (e.g., millimeter scale) features such as layer orientation, thickness, volume fraction, and defects. The effect of these structural attributes on the onset, propagation, and coalescence of cracks is explored. The simulation results show that spatial heterogeneity and material anisotropy highly affect crack patterns and effective fracture toughness, and the elastic contrast of two constituents significantly alters the effective toughness. However, the complex crack patterns observed in the experiments cannot completely be accounted for by either an isotropic or transversely isotropic effective medium approach. This implies that cracks developed in the layered system may coalesce in complicated ways depending on the local heterogeneity, and the interaction mechanisms between the cracks using two-constituent systems may explain the wide range of effective toughness of shale reported in the literature. [URL]
MR004: Data-driven and theoretical approaches for modeling, prediction, analysis of thermo-hydro-mechanical behaviors of frozen soil and rocks
Submit an Abstract to this Session Session ID#: 27208
Frozen soil and rocks are integrated parts of the Earth’s climate system. The timing, duration, thickness and distribution of frozen geomaterialsare dominated by heat exchanges between the environment and the land surface and the multiphysical coupling effects. During freezing and thawing cycles, microscopic mechanisms such as cryo-suction, thermal and hydraulic convection-diffusion, micro-cracks, enhanced particle interlocking and ice strengthening may have a profound effect on the land surfaces at the field scale. Yet, incorporating these complex micro-mechanical coupling effects for applications to earth system modeling remains difficult. This AGU session seeks contributions that innovate new techniques in (1) experimental and field works across length scales (e.g. micro-CT imaging, Lidar scan); (2) numerical modeling of frozen geomaterials, and (3) emerging technologies in data generation, collection and interpretation, such as climate-controlled experimental tests, data-driven machine learning and other approaches that improve the forward prediction and understanding of frozen geomaterials.
Primary Convener: WaiChing Sun, Columbia University, Civil Engineering and Engineering Mechanics, New York, NY, United States
Conveners: Seth Saltiel, Lawrence Berkeley National Laboratory, Berkeley, CA, United States and Jonathan Blair Ajo Franklin, Lawrence Berkeley National Laboratory, Geophysics, Berkeley, CA, United States
0702 Permafrost [CRYOSPHERE]
0704 Seasonally frozen ground [CRYOSPHERE]
0798 Modeling [CRYOSPHERE]
3902 Creep and deformation [MINERAL PHYSICS]
News about Computational Poromechanics lab at Columbia University.