DEM: 3D Block failure 1. The effect of material cohesion

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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.

The effect of material cohesion is examined 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. The movies show experiments where:

1. The breaking strains (0.025-0.05) are fixed and the seed for failure is changed (a) 20%, r_0.5_seed_20.gif, (b) 40%, r_0.5_seed_40.gif, (c) 60%, r_0.5_seed_20.gif and, (d) 80%, r_0.5_seed_20.gif.

2. The seed for breaking bonds is fixed (50%) and the range of breaking strain is changed (50%) (e) 10% (bst=0.005-0.05), (f) 50% (bst=0.025-0.05) and, (g) 90% (bst=0.045-0.05).

Combinations of these two properties can be used to investigate the effects of material strength on slope failure.

See the pdf for static images of the experiments and further information. For a more detailed explanation of the methodolgy used in these experiments please follow the links below to publications using this methodology.