There are two methods that people have used to model HDPE liners in Slide:
- In Slide you can model a HDPE membrane as a thin material layer with a polyline search focus. See Tutorial 3 for more information on doing non-circular searches with a focus entity. Numerous customers of ours use Slide for modeling failure along HDPE membranes. As far as the thickness of the HDPE material layer is concerned, there is no limitation but I would use a reasonable thickness compared to the overall size of the model (1/100-1/1000 of a typical dimension) just to make the modeling easier. If you did a sensitivity analysis on thickness it would turn out to have little effect on the results at this scale. This method is good for looking at failure along the HDPE-soil interface. In which case you define the strength of the layer as the shear strength of the HDPE-soil interface.
- Using a series of geotextile support elements along the interface (see below image). The tensile strength of the geotextile is basically the rupture strength of the HDPE. This method assumes that failure passes through the HDPE and that the HDPE provides some stability through its tensile strength, similar to a geogrid or geotextile. The only thing I would suggest is that you change the anchorage of the geotextile to both ends. This basically means that the geotextile will always fail in tension and that pullout is not an issue and will not be checked. If the geotextile is buried along the length of the slope, it won’t pullout. This way, you’ll at least know the amount of force (the tensile strength) that the geotextile is putting back into the system.