Water table management

(Figure) The scheme of the water table management at the open-pit mineWATER TABLE MANAGEMENT (EN: fall of water table; DE: Wasserabsenkung; FR: abattement des eaux, epuisement; ES: descenso del nivel acuifero; RU: водопонижение) is the method for the lowering of the level and pressure of the water with the help of the drainage devices during the conducting of the mining works.

They conduct the water table management mostly during the period of the construction, and during the start of the operation, of the underground mines and open-pit mines, for the intensive lowering of the level of the underground waters, on the account of the intensified extraction of the static reserves, and of the interception of the dynamic inflow. The water table management is performed mainly using the dewatering boreholes (sometimes in combination with the well point installations, and with the advanced drainage trenches), at the places of the penetration of the capital mine workings, and at the places of the priority operational works.

They equip the dewatering boreholes with the filters (within the interval of the aquifers), and with the submersible pumps for the pumping-out of the water, which are connected with the collectors for the diversion of the water, and with the control board for the automatic control. Depending on the quantity of the aquifers, on their thickness and filtration properties, the quantity of the boreholes varies, and is reaching 100 and more. The predominant yield of the dewatering boreholes at the underground mines and within the open-pit mines is 30-100 cubic metres per hour (sometimes 250 cubic metres per hour); in this case, the magnitude of the lowering of the level of the underground waters within the major aquifers reaches several tens of the metres. The intensive lowering of the level of the water usually proceeds during 2-3 years, then later the yield of these boreholes stabilizes, and gradually decreases, as the result of the total depletion of the resources of the underground waters, and as the result of the significant clogging of the filters within the boreholes (see the Figure). After the undercutting of the dewatering boreholes using the underground mine workings, these boreholes are re-equipped into the through-flow filters, the water from which is diverted to the water management installation. At the deposits with the complex hydrogeological conditions, the water table management is most effective in case of the high coefficient of the filtration of the water-bearing rocks (more than 3 metres per day), and in case of the lowering of the water levels, which is advancing by 1-2 years (in relation to the mining works). See also the "Drainage" article.