A large waste landslide struck in a landfill located outside of Bogota, the capital city of Colombia.
The incident occurred in Dona Juana, a sanitary landfill that receives mixed municipal solid waste (MSW), on April 28, 2020. It is the major site for solid-waste disposal of Bogota for 31 years.
MSW landslides frequently occur in landfills as a result of unsafe disposal practices. The current slide deposited around 60,000 m3 of waste material.
The evidence shows that while the basal area of the slide is large, its depth is relatively low. Therefore, the waste failure appears to be translational. A translational-type landslide occurs in a distinctive plane of weakness, thus, it is not associated with the material’s shear strength but with the strength of the plane itself. It is suggested that such a slip surface had been created during the disposal process.
Fortunately, there were no victims associated with the aforementioned failure but, similar waste slides pose a severe threat especially in less developed countries where people live near the disposal sites and may be highly affected. Besides the immediate hazard of debris flow damaging the local infrastructure, there is a secondary threat associated with MSW slides as toxic gases may be released from waste leading to people's intoxication.
Local people reported being disturbed by an unpleasant smell deriving from the landfill that was probably associated with the incident. The landslide raised questions about the viability of the landfill project. Some residents believe that it should be shut down and waste should be treated using clean technology. In addition, there have been certain arguments about the practices of the private firm that manages the dumping ground but there are no detailed reports on the nature of those concerns.
Click the first video below to watch footage of the site, the day before the failure. It seems that a large tensile crack has appeared in the crown of the slide hours before the incident.
The second video presents the outcome of the waste slide. The footage, that is impressive, shows the enormity of the failure.
Massive landslide in Dona Juana landfill, 1997
A much larger waste slide had occurred at the landfill back in 1997 depositing around 800,000 tons of solid waste. The MSW consisted of 47,8% of organic matter, 44,6% of high deformability material and 7,5% of inert material, and also presented a high water content.
Direct shear strength tests were performed on undisturbed specimens measuring 90 centimeters in diameter. A shear box and a modified Menard pressure-phicometer were used to derive the shear strength of the material near the ground surface as well as at greater depths.
The results, evaluated utilizing the Mohr-Coulomb Failure Criterion, yielded an average friction angle of 23° and an apparent cohesion of 67 kPa.
The failure was a result of multiple factors with the most decisive being the high pore water pressure which was built up due to several reasons. These included the rapid construction of the landfill, something that made the dissipation of pore pressure impossible as well as the decline of leachate collection capacity which increased the waste's water content, thus, lowering its gas permeability.
To find out more about the 1997 landslide, you can access a relevant Conference Paper, published in 2002, here.
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