Discrepancy in the Critical State Void Ratio of Poorly Graded Sand due to Shear Strain Localization
| Autor: | Riyadh I. Al-Raoush, Wadi H. Imseeh, Khalid A. Alshibli |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
021110 strategic
defence & security studies Oedometer tests Materials science Conventional triaxial compression Void ratio 0211 other engineering and technologies 02 engineering and technology Microcomputed tomography Geotechnical Engineering and Engineering Geology Granular material Oedometer test Shear bands Sand Shear stress Geotechnical engineering Critical state 021101 geological & geomatics engineering General Environmental Science |
| Zdroj: | Journal of Geotechnical and Geoenvironmental Engineering. 146 |
| ISSN: | 1943-5606 1090-0241 |
| Popis: | The critical state (CS) concept is a theoretical framework that models the constitutive behavior of soils, including sand and other granular materials. It supports the notion of a unique postfailure state, where the soil ultimately experiences continuous shearing with no change in the plastic volumetric strain. However, the published literature has frequently noted the nonconvergence of sand specimens with different initial densities to a unique CS in the compression plane due to many factors such as specimen fabric, particle morphology, breakage, and grain size distribution. This paper examines the CS for poorly graded (uniform) glass beads and 3 different types of silica sands using 50 conventional triaxial compression (CTC) experiments, 12 oedometer tests, and in situ synchrotron microcomputed tomography (SMT) scans for 10 CTC experiments. The results of the 50 CTC experiments revealed a diffused CS zone in the compression plane, which was further examined using the in situ SMT scans. A thorough three-dimensional image analysis of the SMT scans accurately quantified the evolution of the local void ratio (elocal ) versus axial compression within zones of intensive shearing toward the center of the specimen. The evolution of the void ratio was also measured using the entire volume of the specimen (eglobal ). At the CS, the elocal/eglobal ratio was assessed to be ∼1.25 when a single shear band developed within the scanned specimens and ∼1.1–1.15 for specimens that failed via external bulging that was internally manifested by the development of multiple shear bands. This finding suggests that the CS zone in the compression plane can be attributed to the common wrong consideration of eglobal evolution in lieu of elocal within the developing shear bands. Furthermore, the lack of shear band development in uniaxial compression has made the results of the oedometer test reliable in quantifying the CS parameters in the compression plane. This material was partially funded by the US National Science Foundation (NSF) under Grant CMMI-1266230. Any opinions, findings, conclusions, and recommendations expressed in this paper are those of the authors and do not necessarily reflect the views of the NSF. The SMT scans presented in this paper were collected using the X-Ray Operations and Research Beamline Station 13-BMD of the Advanced Photon Source (APS), a US Department of Energy (DOE) Office of Science User Facility operated by the Argonne National Laboratory (ANL) under Contract DE-AC02-06CH11357. We acknowledge the support of GeoSoilEnviroCARS (Sector 13), which is funded by the NSF Earth Sciences (EAR-1128799), and the DOE Geosciences (DE-FG02-94ER14466). We thank Dr. Mark Rivers for his guidance at APS. Scopus |
| Databáze: | OpenAIRE |
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