A serious accident occurred in the province of Lualabain the Democratic Republic of Congo: the failure of a portion of land covering the access tunnel to one cobalt mine. The landslide event caused the death of at least 32 workersaccording to local authorities. The video demonstrates the significant extension of the landslide and its impact on the adjacent areas. Rescue operations are still underway and the toll of the serious accident could worsen.
Even though the site had been declared unusable due to recent heavy rainssome workers were in the area at the time of the collapse, and subsequently suffered the collapse. Local authorities have stated that the cause of the landslide can be traced back to the rain events of the previous days. In fact, the rainfall was abundant water infiltrations into the overlying groundaltering the hydraulic regime normally present in the layers of the “coverage” and, consequently, the stability of the geotechnical system which until now allowed the transfer of stress to the lateral terrain areas.
Water, by penetrating the solid skeleton of the soil (which has its own porosity), can – in general – be the cause of resistance reduction: the result, as in this case, can be the trigger of phenomena landslides or structural failuresthe latter only if there are structural works that interact with the layers of soil affected by the phenomenon.
The first reconstructions incorrectly speak of a “collapsed bridge”, but technically it is one excavation cap formed following mining operations. This appears to lack real engineering, according to the current documents and information that can be found online. The phenomenon is similar to one induced landslidelinked to the variation in interstitial pressures and the loss of balance of the layers of soil above the excavation, already weakened in themselves by the presence of the works and – in the specific case – not equipped with an appropriate cambering system capable of guaranteeing the right condition of balance (as happens, for example, inside a tunnel).
