Landslide in Grijalva River, México

Along world history, there have existed an endless number of landslides, this represents a geological phenomenon being the main cause for deaths and material damages attributed to natural disasters. On November 4th , a huge landslide occurred in the right bank of the Grijalva River, which closed the flow of the river and implied 3 imminent risks: first the risk for the population living nearby, second was conceived as a technical problem for the regular operation of the Malpaso and Peñitas dams and third the magnitude of the landslide calculated in 55 million cubic meters. The landslide produced a obstruction of the river in a length of 800 meters inside the reservoir of the Peñitas dam, causing it to stop functioning. To solve the problem, , it was planned to excavate a channel to the elevation +100.0 (meters above sea levels) with a cask six meters wide, representing a excavation volume near to 900 thousand cubic meters in order to continue in later stages until reaching elevation +85.0. After several geological and geothecnichall studies, such as back analyses, unconfined and triaxials compression test, the failure mechanism was identified being caused by two main phenomena: one geological related to the litologic and structural aspects, and one meteorological related to intense rain reaching 1000 mms between October 28th and November 3rd 2007, causing increments on the water table levels in the rocks and therefore, an increasing of the pore pressure in the failure plane. The basic premise to define the solution was that, in a minor period of time, the Grijalva river should be flowing again. This landslide might be classified as a Rock Block Landslide constituted by sandstones and shales. This type of phenomenon should be extensively studied in order to prevent similar experiences minimizing the impact for people and infrastructure.