期刊
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
卷 121, 期 3, 页码 1425-1440出版社
AMER GEOPHYSICAL UNION
DOI: 10.1002/2015JB012179
关键词
brittle-ductile failure; damage rheology; porous rock; cataclastic flow; higher-order continuum; discrete element method
资金
- Earth Materials and Processes program at the U.S. Army Research Office [W911NF-14-1-0658, W911NF-15-1-0581]
- Mechanics of Material program at National Science Foundation [CMMI-1462760]
- Provost's Grants Program for Junior Faculty
- Graduate Innovation Project of Jiangsu Province [KYLX-0094]
- Excellent Dissertation and Creative Talent Fund [CE02-1-26]
- Directorate For Geosciences
- Division Of Earth Sciences [1516300] Funding Source: National Science Foundation
- Div Of Civil, Mechanical, & Manufact Inn
- Directorate For Engineering [1462760] Funding Source: National Science Foundation
A micromechanical distinct element method (DEM) model is adopted to analyze the grain-scale mechanism that leads to the brittle-ductile transition in cohesive-frictional materials. The cohesive-frictional materials are idealized as particulate assemblies of circular disks. While the frictional sliding of disks is sensitive to the normal compressive stress exerted on contacts, normal force can be both caused by interpenetration and long-range cohesive bonding between two particles. Our numerical simulations indicate that the proposed DEM model is able to replicate the gradual shift of porosity change from dilation to compaction and failure pattern from localized failures to cataclastic flow upon rising confining pressure in 2-D biaxial tests. More importantly, the micropolar effect is examined by tracking couple stress and microcrack initiation to interpret the transition mechanism. Numerical results indicate that the first invariant of the couple stress remains small for specimen sheared under low confining pressure but increases rapidly when subjected to higher confining pressure. The micropolar responses inferred from DEM simulations reveal that microcracking may occur in a more diffuse and stable manner when the first invariant of the macroscopic couple stress are of higher magnitudes.
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