University of Manchester
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DEM: 3D Block failure 2. Comparing the effect of layer thickness 1

posted on 2022-07-08, 09:40 authored by Emma FinchEmma Finch

These movies show the effect of material cohesion on block failure using a discrete element model. Experiments use a block consisting 232,500 spherical elements in a regular hexagonal packing where each element is in contact with 14 neighbours. Elements interact as though connected by breakable elastic springs, where each link between an element pair can be assigned unique properties to introduce heterogeneity into the system. 

Material cohesion is achieved by modifying either of two parameters, the breaking strain between an element pair or the percentage of bonds that are broken are the start of an experiment. The breaking strain is modified by assigning a percentage (b_range) of the maximum defined value to all elements (e.g. a breaking strain of 0.05 units with a b_range of 50 will assign breaking strains between 0.025 and 0.05 unit to an element). The breaking strain of the link is calculated from the average breaking strain of the two elements it connects. The lower the value of b_range, the greater the variation in breaking strains for elements within the material. To seed the media for failure, a percentage of the initial intact bonds within a defined layer are broken. This randomly selects bonds, so all the links between one element and its' neighbours can be broken, or none at all. 

Presented here are experiments where the relative strength and thickness of weak and strong layers in a block are investigated with a the basal layer made of weak material and an overlying strong upper layer. In the strong layer the b_range is 90 (bst: 0.045-0.050) with 10% of the initial bonds broken and for the weak layer the b_range is 30 (bst: 0.015-0.05) with 50% of the initial bonds broken. The relative thickness of the weak layer increases from 40% to 90% and images demonstrates the percentage of broken bonds from white to dark blue. 

The movies represent models where the weak layer compared to the total thickness of the inital media is (a) 40% (WS_4-6), (b) 50% (WS_5-5) (b) 60%  (WS_6-4), (c) 70% (WS_7-3), (d) 80% (WS_8-2) and, (e) 90% (WS_9-1).

Movies entitled  *_P show a plan view of each experiment. For a more detailed explanation of the methodolgy used in these experiments please follow the links on the webpage to publications using this methodology.  

Experiments comparing the effect of the seed and b_range are presented in doi://10.48420/19635106 and experiments with multi-layered models can be viewed here:  10.48420/20209907 

The references below show other 3D applications of the code.


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