20.500.12556/DKUM-70686 The development of a “drive-in” filters dewatering system in the Velenje coal mine using finite-element modelling Razvoj vtisnih filtrov odvodnjevalnega sistema premogovnika Velenje s pomočjo metode končnih elementov During the mining operations at the Velenje coal mine, groundwater has been presenting a constant threat to underground works. The hydrogeological setup is so complex that a lot of structural drilling and well-logging operations were needed in the past to clarify it. Above the lignite seam is a Pliocene and Pleisticene multilayer aquifer system, composed mainly of permeable sand layers and impermeable clay layers. In 1981 the Pliocene aquifers were divided into three packages. Based on the water-table data of each aquifer, pumping tests, chemical analyses of the groundwater and the geophysical properties the Pliocene aquifers directly above the seam, together with impermeable layers, were divided into: a) the first water-bearing sands (Pl1), b) the aquifers 2080 m above the coal seam (Pl2) and c) the upper Pliocene aquifers (Pl3). For the mining operations the most important aquifer of saturated sands is Pl1. The hydraulic pressure of the groundwater in these sands directly affects the safety of the mining. These aquifers are mostly affected by the dewatering activities, too. However, the dewatering wells are constructed in such a way as to capture the whole Pl2 and, somewhere, even a part of the Pl3 complex, too. The water pressure in this multilayer aquifer can reach over 35 bars, so a massive program of drawdown activities has been needed and is still in place to decrease the water table in the area related to the mining operations. Special, multilevel observation wells are used to monitor the water level. A number of 3D finite-difference models (FDMs) were used to estimate the regional groundwater drawdown. It was observed that the FDMs performed well when predicting the regional situation, but the model-predicted drawdown was lower than the observed values at observation points in the area where the dewatering operations using “drive-in” filters have taken place in the past. This is a well-known problem of the FDM: the drawdown being rather a function of the cell size than of the flow net. The risk of water inrushes will increase, especially after 2012 and 2017, when a series of surface-drilled wells, connected into the mine’s pumping-line batteries, will be abandoned due to excavation works and mining-subsidence effects. Consequently, the dewatering schemes had to be completely reviewed. The destroyed, first-order dewatering structures will have to be replaced by a series of “drive-in” filters, drilled from the mine roadways in the area of the planned longwall face operations. For the drive-in filter-system design the FDM does not seem to be appropriate. This is especially so if the error in the drawdown and pumping flow prediction is taken into account. That led, in 2007, to the selection of the finite-element method (FEM) for the prediction of the groundwater drawdown and the water pumping rates in the areas were the underground works will encounter the risk of a water inrush. Based on the FEM prediction the sizing and the layout pattern of the “drive-in” filters were made. Podzemna dela v premogovniku Velenje ves čas ogroža prisotnost podzemne vode. Zaradi zapletene geološke zgradbe premogovnika je bilo izvrtanih veliko strukturnih vrtin in v njih izdelanih geofizikalnih karotažnih meritev. Nad debelim lignitnim slojem se nahaja večslojni pliocenski in pleistocenski vodonosnik, ki ga izmenično sestavljajo peščene in glinaste plasti. Leta 1981 je bil pliocenski vodonosnik razdeljen v tri vodonosne sisteme glede na hidravlične tlake v njih, črpalne teste, kemizem vode in geofizikalne lastnosti: a) prvi vodonosni paket (Pl1), b) vodonosnik 20 - 80 m nad premoško plastjo (Pl2) in c) zgornji pliocenski vodonosnik (Pl3). Za rudniška dela je najpomembnejši vodonosnik saturiranih peskov (Pl1). Hidravlični tlak v tem vodonosnem paketu direktno vpliva na varnost v spodaj ležečem rudniku. Ti vodonosniki so tudi najbolj pod vplivom odvodnjevanja. Ne glede na to pa so črpalne vrtine izdelane tako, da zajemajo cel paket Pl2 in ponekod tudi dele Pl3. Hidravlični tlaki v teh vodonosnikih lahko dosežejo vrednost do 35 barov, zato so pred leti pričeli z obsežnim programom zniževanja tlakov nad deli, kjer potekajo rudarske aktivnosti. Za opazovanje tlakov so bili na teh območjih izdelani več nivojski piezometri. Za predikcijo razvoja tlakov so bili uporabljeni številni 3D matematični modeli končnih diferenc (FDM). Praksa je pokazala, da so ti modeli za določanje regionalnega trenda toka podzemne vode dobri, glavna slabost pa se pokaže na točkah opazovanja tlakov podzemne vode, ki se nahajajo na mestih odvovodnjevanja z vtisnimi filtri, kjer prihaja do manjših napovedi znižanja od dejanskih. Ta slabost FDM je že dolgo poznana in se pojavlja zaradi večje odvisnosti napovedanega znižanja od velikosti celice kot pa od tokovnega polja. Nevarnost vdorov vode v premogovnik Velenej se bo še posebej povečala po letih 2012 in 2017, ko bodo zaradi posedanja terena, ki nastaja zaradi odkopavanja in subsidence, opustili površinska črpališča. Zaradi tega bo morala biti na novo postavljena strategija odvodnjevanja. Uničene odvodnjevalne objekte prvega reda bo potrebno nadomestiti z vtisnimi filtri, ki bodo izvrtani iz rudniških prog okoli odkopnih čel. Za dimenzioniranje vtisnih filtrov uporaba FDM ni primerna glede na napake, ki nastanejo pri napovedih znižanj in črpanj. To je leta 2007 privedlo do uporabe metode končnih elementov (FEM) za predikcijo znižanja podzemne vode in količin črpanja v območjih, kjer bodo rudniška dela izpostavljena nevarnostim vdorov vode iz površine. Na osnovi predikcije s FEM metodo smo lahko napovedali velikost in opremljenost vtisnih filtrov. drive-in filters groundwater mining water mining hydrology geophysical well login mathematical modelling vtisni filtri podzemne vode rudniške vode rudniška hidrogeologija geofizikalna karotaža matematično modeliranje true false true Angleški jezik Slovenski jezik Fakulteta za gradbeništvo, prometno inženirstvo in arhitekturo Univerze v Mariboru Znanstveno delo 2018-06-06 11:05:25 2018-06-06 11:06:39 2022-08-01 19:40:54 2019-07-11 18:16:11 2009 0 0 str. 50-63 št. 1 Letn. 6 2009 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 1854-0171 622.5 215987712 948575 1854-0171 URN:SI:UM:DK:OJZUZPTL Acta_geotechnica_Slovenica_2009_Vizintin_et_al._The_development_of_a_drive-in_filters_dewatering_system_in_the_Velenje_coal_mine_using_f.pdf Acta_geotechnica_Slovenica_2009_Vizintin_et_al._The_development_of_a_drive-in_filters_dewatering_system_in_the_Velenje_coal_mine_using_f.pdf 1 35D253A2B60D650F89C706A0508DB04E faae43bc66e85702117b3ef499ec6cd2f2e8b5947e726725500575127ba1aa9e 00bac6c8-7c10-11eb-bb7a-00155d0001ca 20.500.12556/dkum/866adbc3-af83-4201-840f-a80b00c72bc2 https://dk.um.si/Dokument.php?lang=slv&id=125321 http://fgserver3.fg.um.si/journal-ags/2009-1/article-4.asp 1 https://dk.um.si/Dokument.php?lang=slv&id=125320 Fakulteta za gradbeništvo, prometno inženirstvo in arhitekturo Acta geotechnica Slovenica 0 0 0