Melnikov Research Institute of Comprehensive Exploitation of Mineral Resources, Russian Academy of Sciences, Moscow, Russia:

N. A. Miletenko, Senior Researcher, Candidate of Engineering Sciences, nmilet@mail.ru
V. N. Odintsev, Leading Researcher, Doctor of Engineering Sciences
E. V. Fedorov, Head of Department. Candidate of Engineering Sciences

The innovative resource saving and ecologically balanced geotechonology for exploitation of KMA Korobkovskoye deposit involves hydraulic filling of excavation chambers with tailings. In terms of geomechanics complete filling of excavations is associated with increased resistance of interchamber pillars, increased stress state and loss of strength of the interchamber ceiling and possible penetration of the filling pulp into excavation and lower chambers in process. A new element of research in this field is evaluation of possible filtration of the pulp liquid fraction from the worked out chambers into extraction chambers below. Modelling of stress-strain state (SSS) of the rock mass was performed to a depth of excavation horizons. The problem of SSS evaluation under gravity forces was solved in the plane strain conditions by final element method. The following conclusions about SSS of the ceiling and rock mass were made basing on the modeling: 1) a 20 m ceiling has a good bearing capacity and should withstand the load of the hydraulic fill in the upper chamber (unless there are natural disturbances); 2) there are no conditions for development of cracks in the ceiling that may serve as channels for the pulp flow from the upper into the lower chamber. Since pulp flow through the ceiling into chambers via induced macrocracks was found unlikely, water penetration from the upper into the lower chamber was modeled by filtration mechanism. The model for non-stationary water filtration in rock mass with various filtration characteristics was used. The following conclusions were made as a result of this study. Pulp breakthrough from the upper into the lower chamber is unlikely (unless there are substantial natural disturbances in the ceiling). Maximal filtration flow into the lower chamber is possible before the upper chamber is drained. In this case water
inflow may reach about 10 m³ per day for a rather limited penetrability of the ceiling material and the ceiling area of the lower extraction chamber 1500 m². Drainage of the upper chamber may result in about ten-fold reduction in the filtration flow from the upper into the lower chamber. These results may be used to improve technologies for hydraulic filling of chambers.

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