The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.
Various media outlets are reporting at least two unusual landslides that occurred on 18 September 2023 at Dolton in Illinois, USA. These landslides, which were triggered by unusually intense precipitation, occurred on the edge of a large, raised landfill site that has been encapsulated and turfed over.
ABC7 Chicago has a tweet showing one of them, for example:-
The site of this landfill is [41.643, -87.594]. There is a good archive of imagery on Google Earth, which includes this view from July 2021:-
It appears to me that the site had suffered a similar landslide at that time.
These are classic translational landslides, almost the perfect “infinite slope” type of failure. It is clear that the geomembrane that is being used to encapsulate the landfill is providing the sliding surface. I would hypothesise that this is providing a permeability barrier, allowing high pore water pressures to develop, lowering the resistance to failure. It might also be providing a low friction sliding surface, allowing quite high mobility.
There is a hint in the aerial images that there might be three of these failures at Dolton – one additional slide appears to sneak into view in the footage. If so, then a substantial amount of work is going to be needed at this site.