Dewatering Wells Research Articles

Improving the pit wall seepage resistance at the V. Grib diamond deposit

Introduction. V. Grib deposit development includes complex dewatering operations, all water-bearing rocks overlying the mining floor are drained. The open pit is mainly flooded by the Padunsky aquifer system. At present, the open pit is being drained by surface dewatering wells together with mine drainage. In total about 7–8 thousand m3 /h of drainage water is pumped out. Setting of the problem. Uncovering a multilayer water-bearing strata characterized by different filtration characteristics of rocks contributes to the formation of pit walls in the Padunsky strata that have not been dewatered. The height of groundwater seepage on pit walls reaches 50 m due to the low conductivity of the Padunsky strata bottom. It is suggested that the Padunsky strata bottom should be dewatered using lateral drain holes built from the pit to the wall benches in areas with no dewatering wells. Methods of research. For pit wall stability improvement, the developed multilayer numerical model of geofiltration is applied to study the use of lateral drain holes built from the pit. The finite difference method in the GMS MODFLOW package was applied for modelling. Research results. It has been found that the operation of 12 lateral drain holes during 1 year reduces the height of groundwater seepage on pit walls by 15–20 m, contributes to the groundwater level decline of the Padunsky aquifer system by 5–10 m on the drainage contour of dewatering wells; water inflow to lateral drain holes will be 810–850 m3 /h. Conclusions. The feasibility of lateral drain holes for the Padunsky strata dewatering intensification in the adjacent rock mass has been established using the method of numerical modeling.

Horizontal well dewatering systems in mining: Experience and prospects

Almost all mineral deposits being currently mined occur in the zones of risk governed by difficult geology, geomechanics, hydrogeology and engineering geology. The main complication factor is often groundwater. The choice of a dewatering system depends on the natural conditions and mining technology at each specific deposit. The article addresses issues of waterproof at an open pit mine of AGD Diamonds; the critical point here is pitwall rock mass dewatering. The performance of a horizontal well dewatering system as the internal pit drainage facility is described. The scope of the analysis embraces the current technology used in construction of horizontal wells of the optimized ‘telescopic’ structure and the size of stricken water influxes. The visual effectivity of pitwall drainage using the horizontal dewatering wells consists in the reduced seepage of groundwater on the pitwall and in the decreased gravity moisture of overburden rocks. The horizontal dewatering wells create conditions for the controllable groundwater removal from the Pandun rock mass at the drainage depth to 150–200 m, which greatly reduces the overall number of flowing water sources on pitwall in the test surface mine of AGD Diamonds. The concept is formulated for the efficient use of the horizontal well dewatering system as the permanent water protection of ultimate pitwall. The horizontal dewatering wells can be used as independent drainage elements and can be included in more complex systems generating an extended horizontal drainage at a certain depth from ground surface.

The influence of dewatering system on groundwater regime at NLMK Lipetsk

The analysis of geological and hydrogeological conditions at the industrial site of Novolipetsk Metallurgical Plant (NLMK Lipetsk) was performed. It was determined that the hydrodynamic regime of groundwater at the industrial site changed in the course of construction and operation of the metallurgical facilities, as well as during creation of the Matyrskoe reservoir. An increase in the infiltration feed of aquifers was detected due to the process water leaks, reduction of surface water runoff and backwater effect from the Matyrskoe reservoir. All of that led to increasing of groundwater levels in the aquifers at the industrial site and to underflooding of the buried structures of industrial facilities. The main elements of protection of buried buildings and structures from underflooding with groundwater of the Neogene–Quaternary aquifer are the permanent drainage sites and injectable plugging for fixing of aquifers rocks. Protection of buried structures from underflooding with groundwater is carried out using 30 dewatering wells located on four sites of permanent drainage. It was found that operation of the permanent drainage sites led to the formation of a depression funnel in the Neogene–Quaternary aquifer, to the flow of groundwater from the Devonian aquifers into the Neogene–Quaternary aquifer and to the change in the groundwater chemistry. The sources of groundwater pollution are the process water leaks from production workshops and settling tanks, chemical water treatment facilities, sewerage networks, and raw material storage sites. The main pollutants of groundwater are iron, manganese, cyanides, rhodanides, phenols, petroleum products and organic nitrogen-containing substances. It is shown that the localization of polluted waters occurs within the depression funnel, the center of which is in the location of sites of permanent drainage. The spread of polluted waters through the Neogene–Quaternary aquifer beyond the depression funnel and the Devonian aquifer contamination with seepage waters from the industrial site are eliminated.

Analysis of Wellbore Skin Samples-Typology, Composition, and Hydraulic Properties.

The presence of a wellbore skin layer, formed during the drilling process, is a major impediment for the energy-efficient use of water wells. Many models exist that predict its potential impacts on well hydraulics, but so far its relevant hydraulic parameters were only estimates or, at best, model results. Here, we present data on the typology, thickness, composition, and hydraulic properties obtained from the sampling of excavated dewatering wells in lignite surface mines and from inclined core drilling into the annulus of an abandoned water well. Despite the limited number of samples, several types of skin were identified. Both surface cake filtration and particle straining in the aquifer occur. The presence of microcracks may be a determining feature for the hydraulic conductivity of skin layers. In the case of the well-developed water supply well, no skin layer was detected. The observed types and properties of wellbore skin samples can be used to test the many mathematical skin models.

Percussion-rotary method of drilling large-diameter dewatering wells in "Bełchatów" liginte mine

Percussion-rotary method of drilling large-diameter dewatering wells in "Bełchatów" liginte mine

Integrating geological uncertainty into planning and modelling for modern and efficient dewatering concepts in large surface mines

The dewatering of subsurface unconsolidated rock strata is a critical prerequisite for many mining operations. The uncertainty in knowledge about the aquifer geometry is critical for both, the planning of directional dewatering drilling and the hydrological planning. This contribution focuses on investigating the influence of geological uncertainty on modern mining-related dewatering measures, namely horizontal directional dewatering wells. The traditional approach of drilling, planning and groundwater modelling on the basis of interpolated geological models is extended to integrate geological uncertainty. Using conditional simulation allows for more robust decisions in planning and subsequently increased efficiency. A case study in a large open pit operation demonstrates the benefit of using such methods. For a specified level of confidence, proposed methods provide a means of determining the number of samples required for the optimal placement of the filter section. The results also provide the means of quantifying uncertainty in predicting filter-well output.

Optimization of Mine Drainage Capacity Using FEFLOW for the No. 14 Coal Seam of China’s Linnancang Coal Mine

The hydrogeology of China’s Linnancang coal mine is very complicated. The aquifuge that lies between the no. 14 coal seam and the underlying K3 limestone aquifer is less than 20 m thick and the mine contains 10 known faults. The largest water inrush event exceeded 9.25 m3/min. Comprehensive modeling of the seepage field was undertaken to determine the appropriate water level in neighboring aquifers to reduce the likelihood of water inrush events. A 3-D hydrogeological model of the coal seam and associated aquifers was established to determine the characteristics of aquifers in the seepage field. The results, along with analysis of the existing mining conditions, showed that water levels will rise, but that if four dewatering wells were to be added in the mine area, the water levels would markedly decline. The water inflow forecast also showed that it is necessary to pump water and simulate water levels under different pumping pressure conditions. Based on this work, it appears that increasing the present drainage capacity by 30 % is economical and feasible.

ISOTOPIC DATA: IMPLICATIONS FOR THE SOURCE(S) OF OSIREION GROUNDWATER, ABYDOS, EGYPT

Among the many wars which depicted and documented at the ancient Egyptian history, little of themThe Osireion, formerly concealed within a West Bank Nile terrace, is thought to have been animportant building to the Ancient Egyptians. Its huge building blocks define a rectangular centralstone island surrounded by a water-filled channel nearly 13m below the surrounding land surface.The channel was cleared of debris to 4.3m in 1925, but not to its original depth. Westerman (2008)successfully probed to 10.4m using a metal rod. Seismic data suggest its walls may extend 15mbelow the water table. Westerman listed six questions that elude archeologists and Egyptologists.Why, when and how was the Osireion built? Is in the interior of the island hollow? Why was it built inwater? What is the source of the water? Eleven water samples were collected including the Nile,Osireion, two nearby idle dewatering wells, an active eastern French drain and six active watersupply wells. a18O and aD were measured by EAEA and PO4, Cl, Na+K and TDS by SohagUniversity. Factors such as evaporation, mixing, relative humidity, surface elevation and rechargeclimate can influence isotopic contents. The Nile sample appears most affected by evaporation,consistent with Lake Nasser’s great size and arid climate. Water samples fall below the GMWL andpaleowater line in a region expected of modern precipitation in arid, low latitude climates. Sinaigroundwater by contrast are isotopically lighter, suggestive of recharge at higher elevation duringcooler climates. a18O, aD, PO4, Cl, Na+K and TDS concentrations suggest Osireion waters are noteasily explained by simple evaporation of any supposed end member. a18O and aD concentrationsare strikingly different from two nearby down groundwater gradient, dewatering wells most likely froma mixed source not typical of the ten other samples. Upfllowing from a semi-confined artesianaquifer, possibly also diffuse regional leakage through the Esna Shale are suggested.