DEM: 3D Block failure 3. Comparing the effect of layer thickness 2
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.
In these movies examples of changing layer thickness where the block of material contains:
1. half weak/strong layers: SW_5-5 & WS_5-5
2. a strong internal layer of increasing thickness: WS_2-6-2, WS_3-4-3 & WS_4-2-4
3. a weak internal layer of increasing thickness: SW_2-6-2, SW_3-4-3 & SW_4-2-4
4. two interbedded weak-strong layers : WS_3-2-3-2 & SW_2-3-2-3
5. five interbedded weak-strong layers: SW_alternate & WS_alternate.
The *_f files show the experiment from the front and *_a are plan view.
The first file: DEM: 3D Block failure 3. Comparing the influence of layer thickness 2.pdf contains still images of the experiments.
Experiments comparing the effect of the seed and b_range are presented in doi:10.48420/19635106 and some investigating the effect of the relative thickness of a strong layer over a weak one are available at: doi:10.48420/20209514
The two references below link to other 3D applications of the method.