Supporting data for PhD thesis "Particle-scale Modeling of Soil Behaviors Associated with Instability Problems"

<p dir="ltr">This dataset supports the research work in the PhD thesis entitled "Particle-scale Modeling of Soil Behaviors Associated with Instability Problems." All data are generated through numerical modeling of strength-deformation-permeability behaviors of granular geomaterials. Data files (i.e., .xlsx files) are categorized in different chapters of the thesis.</p><p dir="ltr">In this thesis, an efficient three-dimensional particle-scale model based on the discrete element method (DEM) is created to simulate soil behaviors under the CSD, constant-volume (CV), and conventional drained (CD) paths. Representative volume elements (RVE) with various initial states (i.e., void ratio and stress) are generated to examine the state dependence of instability. We employ the classic second-order work criterion to identify the onset of instability and synchronously track the deformation. Moreover, the role of fine grains in stimulating instability is explored. The DEM is then coupled with the lattice Boltzmann method (LBM) to examine permeability development along with deformation. </p><p dir="ltr">For typical loose and medium-dense packings, a substantial plastic strain starts developing once the second-order work becomes nonpositive along the CSD path, associated with a volumetric transition from dilation to contraction and magnifying difficulty in maintaining the deviatoric stress constant. At an almost identical stress ratio, shear strength drops dramatically in corresponding CV tests. In contrast, for dense packings, large deformation initiates at a larger stress ratio when the CSD stress path meets the critical state line, beyond which the second-order work turns nonpositive. A quantitative relationship is established between the stress ratio at which the second-order work becomes zero and the state parameter in the framework of critical state soil mechanics (CSSM). Furthermore, micromechanical results verify the stress-force-fabric relationship under the CSD path. Particle-scale analysis reveals that even a small percentage (5% by weight) of additive fines accelerates the inception of instability, enhances flow mobility and induces a prominent reduction in contact number. </p><p dir="ltr">The indiscernible deformation before instability initiation (axial strain ) cannot provide forewarning. However, shear wave velocity is demonstrated as an acuter indicator, which declines considerably as CSD loading proceeds. A notable drop in permeability after instability corroborates salient threats of loosely packed granular slopes. Moreover, anisotropy of wave velocity and permeability can be correlated with fabric anisotropy and axial strain, respectively. This study develops a robust numerical model and provides fundamental particle- and element-scale information for developing advanced constitutive models, which facilitates the continuum simulation of rainfall-induced flowslides.</p>