High Pressure Isotropic Compression and Grain Crushing of Coarse Granular Materials

Park, Joon Soo

Graduate Thesis Or Dissertation

High Pressure Isotropic Compression and Grain Crushing of Coarse Granular Materials Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/h702q6756

Abstract

The effect of grain crushing and grain size on the evolution of water retention curve is investigated based on the framework of Unsaturated Breakage Mechanics (UBM) (Buscarnera & Einav, 2012). The previous study by Gao et al. (2016) have been complemented by additional compression and soil water retention data on two types of granular soils with coarser and finer initial gradings than the ones presented in Gao et al. (2016). The model satisfactorily captures the co-evolution of suction air-entry value (S_AEV) and the degree of grain breakage during compression. In addition, this study revealed that the effect of grain shape and pre-yielding void collapse are necessary components for future enhancement of the breakage mechanics model.

The compressive and breakage response of coarse granular materials are further investigated using the High Pressure Isotropic Compression (HPIC) device (Mun & McCartney., 2017). This thesis introduces several troubleshooting attempts of the HPIC device and the developed protocols to conduct high-pressure crushing tests. Coarse quartz sand and crushed shale sand are subjected to the high pressure isotropic compression test under dry and saturated states. Differences between the two materials in the compression curve are observed and the possible reasons are discussed. The compression tests are stopped at various stress levels to allow for inspections on the grain size distribution (GSD). Based on these measures, the degree of grain breakage is quantified via Einav’s breakage index (Einav, 2007). A clear increase on grain breakage at elevated stress states and the evolution towards an ultimate fractal state is clearly observed. The obtained results are interpreted using a new 1D breakage model to serve as the basis of the next-generation breakage mechanics models.

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