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Kajetan D’Obyrn

The Wieliczka Salt Mine is the most famous and the most visited mining industry monument in the world and it requires modern methods to ensure rock mass stability and tourists’ security. Both for conservation and tourism organization reasons, the group of Warszawa-Wisla-Budryk-Lebzeltern-Upper Witos Chambers (Photo. 1, 2. 3) located the Kazanów mid-level at a depth of 117 m underground is extremely important. Discontinuous deformation occurring in this Chamber complex was eliminated by comprehensive securing work with anchor housing, but their final securing and stability is conditioned by further backfilling and sealing the Witos Chambers situated directly beneath. In the 1940s and 1950s, the Witos Chamber was backfilled with slag from the mine boilerhouse. However, slags with 80% compressibility are not backfilling material which would ensure the stability of the rock mass.

The chambers were exploited in the early nineteenth century in the Spizit salts of the central part of the layered deposit. The condition of the Upper Witos, Wisla, Warszawa, Budryk, and Lebzeltern Chambers is generally good. The western part if the Lebzeltern Chamber (Fig. 1), which was threatened with collapse, was backfilled with sand. In all the chambers of the Witos complex, local deformation of ceiling rock of varying intensity is observed as well as significant destruction of the side walls of pillars between chambers. No hydrogeological phenomena are observed in the chambers. It has been attempted to solve the problem of stability of the rock mass in this region of the mine by extracting the slag and backfilling with sand, erecting concrete supporting pillars, backfilling the voids with sand, anchoring the ceiling and the side walls, the use of the pillar housing. The methods have either not been applied or have been proved insufficient to properly protect the excavation situated above.

In order to select the optimal securing method, a geomechanical analysis was conducted in order to determine the condition of the chambers with particular emphasis on the pillars between the chambers. The analysis demonstrated the need to backfilling the Witos Chambers in order to improve the strength parameters of the pillars and the cross-level ledge. The next step consisted of selecting the sealing mix and testing how the additional burden and improving the slag strength parameters shall affect the stability of the excavations of the Kazanów mid-level. In order to determine the optimal composition of the backfilling mixtures, formulas of sealing brine slurries have been developed. Laboratory tests were also conducted concerning the strain parameters specifications of slags extracted from the Witos Chamber. Taking into account the slurry tests, and in particular, the density, strength and strain parameters, the optimal composition of the sealing mix was selected. The analysis of the results of numerical recalculations demonstrate that even the use of highest-density mixtures, backfilling(sealing) of the Witos Chambers should not cause significant disturbance of the current tension in the surrounding rock mass. The longterm impact of sealing should lead to improvement of the strain levels on the ledges between Level III and Kazanów mid-level chambers.

The positive results of applying in the Mine of injection slurries for sealing and stabilizing the rock mass and the construction of the injection node on the surface of the Kosciuszko shaft area have allowed resuming work in the Witos Chambers. The main injection over 1,000 m long pipeline was constructed from the injection node through the Kosciuszko Shaft and along Level III of the mine. The sealing of the Witos Chambers complex was divided into three areas (Fig. 2) separated by backfilling dams. Each region was connected to an injection and venting pipeline, and areas of possible injection material off-flow from backfilling locations were secured. Once that the Chambers are sealed with the use of the pipeline seven bore holes will be drilled from excavations situated above through which the sealing slurry will be administered. The operation will serve to eliminate any voids and re-seal the slag, and it will be conducted until pressures of approximately 0.5 MPa on the bore hole collar is achieved.

As past experience indicates, injection slurry formula can be regularly adjusted adequately to the changing geomechanical parameters and the type of sealing work at the Wieliczka Mine.

Once that the backfilling and sealing process in the Witos Chambers complex is completed, it shall be necessary to conduct monitoring activities in order to determine the processes occurring in the rock mass after the backfilling.

The properties of sealing mixtures qualify those for use in the environment both of salt mines and other mineral ore mines to stabilize the rock mass in the mining-geomechanical context precluding the possibility of weakening the rock mass strength parameters and at the same time sealing the rock mass and the loose material deposited in the excavation.

Open access

Kajetan d’Obyrn and Joanna Hydzik-Wiśniewska

Abstract

As a result, of more than 700 years of exploitation in the Wieliczka Salt Mine, a network of underground workings spreading over eleven levels was created. All mine workings of significant historic and natural qualities and the majority of functional mine workings designated to be preserved are located on levels I to V. The most precious of them, available to tourists, are located in the central part of the Mine on levels I-III. The Mine is not anticipating to make levels IV, Kołobrzeg and V available for a wider range of visitors, even though there are historically and naturally precious workings in those areas as well. The most valuable of the mine workings come from the eighteenth and nineteenth centuries and were exploited mainly in a bed of fore-shaft salt, Spiza salt and the oldest ones. The characteristic feature of these excavations, distinguish them from the chambers located on the levels I-III, is the room-and-pillar system that had been used there. Mine workings exploited in this system measure up to 100 metres in length, and the unsupported pillars standing between the chambers measuring 4-10 metres in width were remained. The described above levels, including levels of VI-IX are to provide a stable support for the workings located higher up. The remaining part of the mine, with the exception of the function workings, is designated for liquidation by backfilling.

The article presents an assessment of stability of the mine workings, located on levels IV-V, and their impact on the surrounding rock mass and the land surface. The analysis was based on geodetic measurements and numerical calculations for strain state of rock mass surrounding the mine workings, in actual conditions and after partial backfilling, and forecast of the rock stability factor after the end of backfilling. The assessment stability factor in the vicinity of excavations at levels IV-V was based on the results of spatial numerical analysis covering the entire central area of the mine from the surface to level V. Numerical calculations were performed using FLAC programme based on the finite difference method, allowing to observe the mechanisms and processes of destruction and deformation. The calculations were performed for the elastic-plastic medium with the Mohr-Coulomb failure criterium. The choice of this computational model was dictated by a very diverse geological structure of the Wieliczka rock mass and a complex system of excavations.

Open access

Kajetan D’Obyrn and Joanna Hydzik-Wiśniewska

Each excavation or excavation complex intended to be backfilled or secured requires an individual approach, and conducting a detailed geomechanical analysis which will allow the selection of the appropriate manner of securing or backfilling or liquidation, and the order of performing mining works. The numerical model of the selected chamber or group of chambers must accurately reflect the reality and have an appropriately selected calculation model.

The paper presents the selected aspects of numerical modelling of the “Wieliczka” salt rock mass. There are method of selection of geotechnical and rheological parameters of salt, the geometrization of the excavations continues and selection calculation model.

Open access

Kajetan D’Obyrn and Antoni Tajduś

Abstract

Salt was excavated at the “Wieliczka” Salt Mine for over 700 years. Underground mining operations terminated in 1996, by which time almost 2,400 chambers and 245 km of galleries had been created underground, situated on 9 levels and a few interlevels. In 1978, the mine was included in the UNESCO World Heritage List, which stated that parts of the mine with historical value had to be preserved for future generations. In order to preserve the most valuable chambers and galleries, activities aimed at establishing a protection pillar for excavations were conducted in the conservation area on Levels I-V. The need of large scope preserving works created the necessity to conduct a new and truly comprehensive geomechanical analysis. Such an analysis could only be done by means of advanced numerical modelling codes. Three-dimensional calculations were performed by means of FLAC 3D finite difference code. Rock mass stability assessment in the vicinity of excavations was carried out on the basis of the distribution and range of the so called failure zones. This comprehensive geomechanical analysis allows for verification and give the directions for future preservation and closure works in the “Wieliczka” mine.

Open access

Kamil Juśko, Jacek Motyka, Kajetan d’Obyrn and Zbigniew Adamczyk

Abstract

Areas of intense mine drainage that are subjected to numerical modelling require the construction of a complex model structure that will properly reflect actual conditions. This paper presents the process and results of constructing such a structure for the Olkusz Zinc and Lead Ore Mining Area, an area situated in a cone of depression the extent of which reaches 500 km2. This size range calls for a selection of appropriate external boundaries, properly separated from these of the mine drainage area. The complex geological structure of the Olkusz area, associated with considerable variation in the thickness of rock formations, discontinuities of rock levels and occurrence of numerous faults, must be schematised so that calculation layers can be identified. The faults in the study area have to be reflected in the regional model structure, although only those faults that actually affect groundwater flows should be selected. The model structure needs to include detailed recognition and reflection of hydraulic contacts between aquifer levels, together with a selection of hydrogeological parameters that are different for particular formations. Only a complex structure built in such a manner may be the foundation of further model studies.

Open access

Marek Cała, Agnieszka Stopkowicz, Michał Kowalski, Mateusz Blajer, Katarzyna Cyran and Kajetan D’obyrn

Abstract

Stability of mining openings requires consideration of a number of factors, such as: geological structure, the geometry of the underground mining workings, mechanical properties of the rock mass, changes in stress caused by the influence of neighbouring workings. Long-term prediction and estimation of workings state can be analysed with the use of numerical methods. Application of 3D numerical modelling in stability estimation of workings with complex geometry was described with the example of Crystal Caves in Wieliczka Salt Mine. Preservation of the Crystal Caves reserve is particularly important in view of their unique character and the protection of adjacent galleries which are a part of tourist attraction included in UNESCO list. A detailed 3D model of Crystal Caves and neighbouring workings was built. Application of FLAC3D modelling techniques enabled indication of the areas which are in danger of stability loss. Moreover, the area in which protective actions should be taken as well as recommendations concerning the convergence monitoring were proposed.

Open access

Kajetan D’Obyrn, Beata Klojzy-Karczmarczyk and Janusz Mazurek

Strcszczcnic

Badania monitoringowe jakości środowiska gruntowo-wodnego na terenach byłego obszaru gór- niczego Barycz Kopalni Soli w Wieliczce a wykorzystywanego obecnie pod składowanie odpadów komunalnych, prowadzone są nieprzerwanie od 2000 roku. Lokalizacja punktów monitoringu oraz zakres badanych parametrów zostały oparte na posiadanych danych archiwalnych, przy uwzględ- nieniu lokalnej budowy geologicznej, hydrogeologicznej oraz warunków hydrologicznych w rejonie potencjalnego oddziaływania składowiska. Prowadzony przez Kopalnię Soli Wieliczka SA. oraz IGSMiE PAN monitoring zlewni Malinówki obejmuje swym zakresem zarówno punkt położony na odcinku powyżej składowiska (punkt E), jak i punkt zlokalizowany poniżej składowiska odpadów komunalnych (punkt D) (rys. 1). Przyjęty system opróbowania pozwala na porównanie aktualnego poziomu zanieczyszczenia poniżej składowiska z lokalnym tłem hydrogcochcmicznym, za jakie można uznać wyniki pomiarów składu chemicznego wód w rejonie źródliskowym Malinówki. W pracy przedstawiono, uśrednione w kwartałach, wyniki pomiarów jakości wód Malinówki z lat 2012-2014. Stężenia chlorków oraz azotanów i fosforanów w wodach potoku Malinówka, pobie- ranych w punkciel poniżej składowiska, kształtują się na średnim poziomic kilka razy wyższym niż w rejonach źródliskowych. Zawartość chlorków w wodach przed składowiskiem kształtuje się na uśrednionym poziomic około 50 mg/dm3, natomiast poniżej składowiska wzrasta czterokrotnie. Zawartość azotanów i fosforanów wzrasta natomiast kilkakrotnie przyjmując jednak niskie wartości na poziomic do kilku mg/dm3. Generalnie nic zauważa się zdecydowanego podwyższenia zawartości metali ciężkich w punkcie poniżej składowiska. Ich wartości zarówno w punkcie E, jak i w punkcie D są niskie, często poniżej granicy oznaczalności. W wodach potoku Malinówka poniżej składowiska (punkt D) obserwowany jest jedynie niewielki wzrost zawartości miedzi, cynku i rtęci oraz w po- jedynczych przypadkach także chromu.

W latach 2012-2014, wykonano dodatkowo kilka serii badań jakości solanek ujmowanych w otworach odprężających oraz grupach otworów na obszarze byłego obszaru górniczego Barycz (otwory E-872 i E-945 oraz E-627 a także grupa otworów SI). Znajomość składu chemicznego solanek oraz porównanie z parametrami charakterystycznymi dla wód powierzchniowych z obszaru zwią- zanego z oddziaływaniem składowiska, może ułatwić wyciąganie wniosków, co do udziału anali- zowanych źródeł w zanieczyszczeniu wód potoku Malinówka. Solanki charakteryzują się bardzo wysoką mineralizacją, związaną Równic z obecnością chlorków. W pobranych solankach pomierzono ponadto wielkości wskaźników, które charakteryzują się podwyższonymi wartościami w wodach powierzchniowych, w punkcie poniżej składowiska (punkt D). Zawartości azotanów i fosforanów w solankach kształtują się na poziomic uzyskanym dla wód powierzchniowych potoku Malinówka. W solankach analizowano także zawartość rtęci i stwierdzono jej obecność na poziomic nieco wyższym niż w ciekach powierzchniowych w granicach od 0,001 do 0,002 mg/dm3.

Analiza jakości wód Malinówki oraz solanek może stanowić istotny element w procesie rozpoz- nania źródeł zanieczyszczeń, spowodowanych byłą eksploatacją górniczą oraz eksploatacją składo- wiska odpadów komunalnych. Przypuszczalne kierunki przepływu wód infiltrujących z powierzchni oraz wód podziemnych wskazują na istnienie strefy potencjalnego mieszania wód opadowych, płytkich wód podziemnych oraz odcieków ze składowiska. Ze względu na warunki geologiczne i hydrogeologiczne obszaru, widoczny przyrost zawartości chlorków w wodach Malinówki, można wiązać zarówno z potencjalnym oddziaływaniem składowiska, jak też z wpływem pozostałości po dokonanej eksploatacji otworowej soli kamiennej (głównie otwory odprężające oraz deformacje górotworu). Natomiast wzrost zawartości azotanów oraz fosforanów może być wynikiem oddzia- ływania obiektu składowania odpadów lub lokalnych cieków i rowów odwadniających zasilanych zanieczyszczonymi wodami opadowymi i prawdopodobnie ściekami bytowymi z okolicznych gospo- darstw'. Wzrost zaw'artości niektórych metali w- wfodach możne dodatkowa sugerować negatywne oddziaływfanic składowiska odpadów komunalnych. Podwyższenie zawartości rtęci w punkcie po- niżej składowiska potwierdza istnienie wzajemnych kontaktów' hydraulicznych w górotworze z wo- dami opadowymi infiltrującymi wr podłoże. Istniejące wyniki badań pozwalają na potwierdzenie rodzaju ognisk zanieczyszczeń, jednak nic pozwalają na bardziej dokładne określenie ich wT>ływru na wielkość sumarycznego ładunku zanieczyszczeń w wrodach Malinówki poniżej obszaru górniczego kopalni, a tym samym poniżej 1 etapu składowiska odpadów w' Baryczy. Dla osiągnięcia tego celu wskazana jest weryfikacja i rozszerzenie zakresu badań w analizow'anym obszarze.