Cyclic Behavior and Liquefaction Resistance of Fine Coal Refuse-Experimental and Numerical Modeling

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Fine coal refuse (FCR) is the waste produced in mining process. FCR can be classified as low-plasticity to non-plastic sandy silt or silty sand. Although FCR consists of appreciable amount of fines content (30% to 60%), there is a high liquefaction potential for hydraulically deposited FCR in impoundments due to its loose and saturated structure as well as its low permeability. Therefore, dynamic properties, particularly liquefaction resistance, of FCR should be investigated. In this study, cyclic direct simple shear (DSS) tests were performed on reconstituted samples of FCR to determine its dynamic properties and liquefaction resistance. Slurry deposition method, which mimics the fabric and structure of hydraulically deposited soils, was used to prepare representative samples of FCR. In addition, the results of cyclic DSS tests were used to calibrate plasticity constitutive models developed to simulate liquefiable materials. PM4Sand and PM4Silt are plasticity models that are developed to obtain monotonic and cyclic undrained shear behavior of liquefiable materials, for sands and low plasticity silts or clays, respectively. It was of interest to find which model better represents the dynamic characteristics of FCR since the material is composed of both silt and sand and exhibited behavior that could be characterized as both liquefaction and cyclic-softening. Therefore, the PM4Sand and PM4Silt constitutive models were calibrated for FCR using the DSS experimental results in FLAC, a 2-dimensional finite-difference program. The simulation results were compared against the experimental results. This research revealed the applicability as well as limitations of the two constitutive liquefaction models in simulating the cyclic shear response of fine coal refuse.



Presented at the Eighth International Conference on Case Histories in Geotechnical Engineering March 24–27, 2019 in Philadelphia, Pennsylvania



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