Kherzet Youcef Mine Flooding of 2nd June 1990 Revisited (Northeastern of Algeria) Origine and Hydrogeological Consequences
Abstract This work is part of the hydro geological study of the Kherzet Youcef deposit. The polymetallic deposit of Kherzet Youcef is known since the beginning of the 20th century. It is known by the exploitation of Lead and Zinc ore. It is located 50 Km southeast of Setif (North-eastern Algeria) and 5.5 Km west of Ain Azel. Mineralization can be described by some ore bodies (about 25). The thickness variate from a few centimeters up to 3 m. These bodies are located on the layers of dolomite and dolomitized marl and along the Kherzet Youcef fault. The geological reserves of Zinc and Lead ore are of the order of 1.6 million tons. This ore has a Pb content of 3.6% and Zn content of 18.4%. The projected annual exploitation was 100 thousand tons per year. Hydro geological studies carried out successively (1973-1977) and (1981-1983) revealed the existence of an aquifer system located west of the Kherzet Youssef fault. It is characterized by the presence of Karts and by strong cracking due to local brittle tectonics. These two characteristics define the filtration and storage capacity of very abundant groundwater. This groundwater represented a major handicap for mining in view of the large amounts of water that required the installation of major pumping and drainage devices. The Kherzet Youssef mine has experienced frequent flooding in the past at a time when technology could not pump efficiently. It caused the mine to close several times. In June 1990, the mine experienced a flood of great magnitude that has never been observed and despite the large installed means of pumping, this 'water costled to the total drowning of the mine, the death of 19 workers and the stoppage of the exploitation of this deposit since. Pitting attempts were carried out with a pumping capacity of 1100 m3/h, then 1800 m3/h but without success. The interpretation of the drawdown data and field observations made it possible to conclude that this accident was only the result of the general destabilization of the massif. Our complementary work by geophysical prospecting made it possible to represent the configuration of the underground layers and demonstrate the hydrodynamic communication between the two East and West compartments of the deposit.