DEM simulations of simple fragmentation experiments

• Published in: Landslides and Engineered Slopes. Experience, Theory and Practice Vol. 1; pp. 2113 - 2119
• Main Authors: Zhao, T., Dai, F., Crosta, G.B., De Blasio, F., Utili, S.
• Format: Book Chapter
• Language: English
• Published: CRC Press 2016
• Edition: 1
• Subjects: Inter-particle Bonds; Acoustic Fluidization; Parallel Bond Model; DEM Simulation; Granular Density; Bonded Particle Model; Runout Distance; Overburden; Slope Break; Fragments Deposit; Weak Zones; Rock Mass; Rock Avalanches; Rock Block; Rock Fragmentation; Breakage Ratios; Intact Rock Block; Slope Geometry; DEM; Granular Mass; Parallel Bond; Flat Horizontal Plane; Horizontal Floor; Maximum Tangential Force; DEM Model
• ISBN: 1138029882; 9781138029880
• DOI: 10.1201/9781315375007-256

Fragmentation can occur in rapid solid mass movements due to different controlling factors. In particular, here we consider the initial state of stress, rapid unloading, shearing of highly stressed grain chains and extremely rapid loadings. The last two cases could also be described as dynamic fragmentation, while the first two are more typical of instability phenomena. In this contribution, we present a series of simulations by Discrete Element Method (DEM) for a simple block and slope geometry, where a particle agglomerate of prismatic shape is released along a sliding plane and subsequently collides onto a flat horizontal plane at a sharp kink point. These conditions have been chosen because two sets of experiments with the same settings (Bowman et al. 2010) are available in the literature and resemble simplified natural geometries. In this study, we analyze how dynamic fragmentation occurs in the numerical model and the modes of failure for different rock blocks. The rock fragmentation occurs mainly in the lower part of the rock block after direct impacts with the ground floor, producing several small fragments. The upper part of rock block suffers little influence from the impacts, creating relatively large fragments. Rock masses with many initial weak zones (e.g. fractured or highly weathered rock) exhibit very poor performance of integrity, as represented by their short final runout distances, large breakage ratios, small fragment mass ratios and low final energy. This chapter presents a series of simulations by Discrete Element Method (DEM) for a simple block and slope geometry, where a prismatic particle agglomerate block is released along an inclined sliding plane until collision onto a flat horizontal plane at a sharp break. It illustrates the DEM bonded-particle contact model and provides the model configuration of rock avalanche and presents the obtained numerical results. The chapter provides the capability of the DEM to model rock fragmentations. The DEM has been widely used to simulate rock avalanches and has proven to be useful in enhancing our understanding of the behavior of rock avalanches. In the DEM model, the rock block is made of densely packed particles, and bonded together by breakable parallel bonds of assigned strength. In the DEM model the width of the sliding channel is slightly larger than the width of the granular block, such that the rock mass can slide downslope quickly.