Investigation of the Effect of Block Size, Shape, and Freeze Bond Strength on Flexural Failure of Freshwater Ice Rubble Using the Discrete Element Method

2021 ◽  
Vol 143 (5) ◽  
Author(s):  
Soroosh Afzali ◽  
Rocky Taylor ◽  
Eleanor Bailey ◽  
Robert Sarracino ◽  
Marjan T. Boroojerdi
Keyword(s):  
Three Dimensional ◽  
Block Size ◽  
Discrete Element ◽  
Failure Behavior ◽  
Discrete Element Modeling ◽  
Freshwater Ice ◽  
Flexural Failure ◽  
Broken Ice ◽  
Parameter Values ◽  
Damping Model

Abstract As part of the Mechanics of Ice Rubble project, recent experiments have been carried out to study the strength and failure behavior of ice rubble beams and the freeze bonds that form between individual ice blocks. In this study, we present results obtained from a newly developed model for the three-dimensional (3D) discrete element modeling (DEM) open-source code LIGGGHTS. The ice model contains normal and shear springs that operate between neighboring particles which are bonded or that overlap due to compressional stresses. Energy dissipation is accounted for by using a viscous damping model. Using this DEM model, medium-scale freshwater ice rubble punch tests have been simulated. Rubble specimens were generated by “raining” individual DEM ice pieces into a rectangular form and compacting the rubble mass to achieve the target porosity. Before the compacting pressure was removed, bonds between contacting blocks were introduced with parameter values based on representative freeze bond experiments. The rubble beam was then deformed by pushing a platen vertically downward through the center of the beam until failure occurred. Two types of block size and shapes have been simulated: cuboid blocks generated based on the size distribution of the actual rubble, and rubble blocks generated by image processing of actual blocks of broken ice used in the comparison experiments. The mechanism of flexural rubble failure for both cuboid block [s4.2] simulations and empirical block [s4.3] simulations is in line with experimental results; however, the empirical block simulations provide a significantly better estimation of the failure force.

Investigation of the Effect of Block Size, Shape and Freeze Bond Strength on Flexural Failure of Freshwater Ice Rubble Using the Discrete Element Method

2019 ◽  
Author(s):  
Soroosh Afzali ◽  
Rocky Taylor ◽  
Eleanor Bailey ◽  
Robert Sarracino ◽  
Marjan T. Boroojerdi
Keyword(s):  
Discrete Element Method ◽  
Size Distribution ◽  
Numerical Models ◽  
Block Size ◽  
Discrete Element ◽  
Failure Behavior ◽  
Freshwater Ice ◽  
Flexural Failure ◽  
Dem Model ◽  
Element Method

Abstract Understanding ice rubble strength and associated failure mechanics is important for a variety of engineering applications in marine ice environments, including the design and operation of coastal, offshore, subsea and floating structures. As part of the Mechanics of Ice Rubble project, recent experiments have been carried out to study the strength and failure behavior of ice rubble beams and the freeze bonds that form between individual ice blocks. These new results serve as an important guide for the development of improved numerical models. The discrete element method (DEM) is a direct modeling approach which has the potential to both describe and enhance understanding of the behavior of brittle granular materials, especially with regard to the evolution of damage towards failure. In this study we present results obtained from a newly developed model for the 3D DEM open-source code LIGGGHTS. The ice model contains normal and shear springs that operate between neighboring particles which are bonded or that overlap due to compressional stresses. Energy dissipation is accounted for by using a viscous damping model. Using this DEM model, medium-scale freshwater ice rubble punch tests have been simulated for ice rubble beams with nominal dimensions of 0.50m × 0.94m × 3.05m. Rubble specimens were generated by “raining” individual DEM ice pieces into a rectangular form and compacting the rubble mass to achieve the target porosity. Before the compacting pressure was removed, bonds between contacting blocks were introduced with parameter values chosen based on representative freeze bond experiments. The ice rubble beam was then deformed by pushing a platen vertically downward through the center of the beam until failure occurred. For the numerical simulations presented here, two types of block size and shapes have been considered: cuboid blocks generated based on the size distribution of the actual rubble, and rubble blocks generated by image processing of actual blocks of broken ice used in the comparison experiments. Results obtained for these two scenarios are compared with corresponding experimental test data. These results highlight that the DEM model is useful for estimating the flexural strength of the rubble, simulating the failure mechanism and for examining the extent to which the ice rubble beam failure is controlled by the strength of the freeze bonds. These results also provide valuable new insights regarding the importance of shape and size distribution of ice blocks on simulated ice rubble strength and failure behavior. Recommendations for future work are provided.

scholarly journals Ballast bed resistance characteristics based on discrete-element modeling

2018 ◽  
Vol 10 (6) ◽  
pp. 168781401878146 ◽  
Author(s):  
Zhiping Zeng ◽  
Shanyi Song ◽  
Weidong Wang ◽  
Haijian Yan ◽  
Guoshu Wang ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Discrete Element ◽  
Discrete Element Modeling ◽  
Slope Gradient ◽  
Three Dimensional Model ◽  
Lateral Resistance ◽  
In Situ Experiments ◽  
Distribution Limits ◽  
Longitudinal Resistance

In this study, in situ experiments were conducted to study the changing characteristics of the lateral and longitudinal resistance of a ballast bed, and a three-dimensional model for the ballast bed and sleeper was constructed based on the discrete-element method. The effects of the lateral and longitudinal resistance of the ballast bed, such as gravel ballast grading, sleeper depth, the angle of the shoulder slope, and ballast bed shoulder width, among others, were studied. The results suggest that (1) the lateral and longitudinal resistance of the ballast bed increases with the widening of ballast grading, and within the size distribution limits, the resistance of the ballast bed satisfies the specification; (2) the lateral and longitudinal resistance of ballast bed increases with an increase in the sleeper depth and the resistance of ballast bed satisfies the specifications for sleeper depth greater than 150 mm; (3) the lateral resistance of the ballast bed increases with a decrease in the angle of the shoulder slope, whereas the longitudinal resistance remains unchanged and the resistance of the ballast bed satisfies the specifications for slope gradient of 1:1.75 or less; and finally, (4) the lateral resistance of the ballast bed increases with the widening of the ballast bed shoulder, whereas the longitudinal resistance remains unchanged, and the resistance of ballast bed satisfies the specifications when the shoulder width is greater than 400 mm.

Investigation of failure and damage processes of andesitic rocks

2021 ◽  
Author(s):  
Özge Dinç Göğüş ◽  
Deniz Yılmaz ◽  
Elif Avşar ◽  
Kamil Kayabalı
Keyword(s):  
Three Dimensional ◽  
Strain Curve ◽  
Damage Threshold ◽  
Peak Stress ◽  
Discrete Element ◽  
Discrete Element Modeling ◽  
Shear Cracks ◽  
Major Mechanism ◽  
Damage Process ◽  
Dem Analysis

<p>In this research, failure and deformation processes of andesitic rocks are investigated through laboratory and discrete element modeling (DEM) analysis to reveal the transition of the cracking, namely from microscale to mesoscale (lab scale). For this purpose, the mechanical properties of Ankara andesites were initially investigated by performing uniaxial - triaxial compressive and indirect tensile laboratory tests. Further, these properties were used as reference parameters for the calibration process in a numerical model, generated through a three-dimensional open source code (Yade) based on the discrete element method (DEM). Our results show that during the linear-elastic region of the stress-strain curve, the major mechanism of rock behavior is driven by tensile cracks. When the crack damage threshold is reached, as a result of plastic strain, the strength related to the inherent cohesion significantly decreases and damage in the rock cannot be prevented anymore. At the peak stress of the curve, both tensile and shear cracks accumulate, intensively. Even the mesoscale failure mechanism is controlled by shearing at the residual stage of the yielding, based on the micro-scale process in the DEM model, the number of micro shear cracks is very limited compared to the tensile ones. This finding shows that the friction takes the control of the damage process as the only driving force during residual phase time.  </p>

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