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Tadeusz Majcherczyk, Zbigniew Niedbalski and Daniel Wałach

Abstract

The paper presents geomechanical properties of rock mass occurring in the initial section of shaft lining during its execution. The shaft being sunk is surrounded with cohesive soils, mainly clays with sand layers and silts. Such lithology causes that in various levels some parts of strata are saturated with water. This results in a considerable changeability of soil properties in time. With high water content, the soil is washed away leading to local loss of contact between shaft lining and surrounding soils. This, in turn, results in lack of proper support for curbs and shaft lining fracture in some sections. Engineering activity in such a case should embrace sealing injections in selected parts of the shaft in order to resume proper reinforcement in the lining-rock mass system. The studies of the soils surrounding shaft lining were supposed to help design curbs with increased bearing capacity. The tests of soils indicated that the angle of internal friction and cohesion do change not only at different depths but also at the same depth in different points of perimeter. It was also observed during the study that the mechanical parameters of the analyzed soils improve as the distance from the shaft lining increases, which clearly indicates change of soil properties in the direct neighborhood of the shaft. Considerable number of tests carried out in the study allowed to determine the relationship between water content and angle of internal friction or soil cohesion. The determined relationships can help to estimate change of soil properties under the influence of water with considerable precision. The reinforcement of curbs executed with the use of ground anchors allowed for further shaft sinking. The tests of concrete used in the shaft carried out in the analyzed section produced results similar to the values assumed in the project.

Open access

Tadeusz Majcherczyk, Zbigniew Niedbalski and Michał Kowalski

The paper presents an evaluation of 3D numerical modeling of the first road tunnel built mining method in Poland, on the Polish-Slovakian border. The Laliki tunnel presents a unique case for an assessment of 3D numerical modeling as a tool for tunnel design due to detailed data being available from monitoring during construction. Geotechnical evaluation carried out for the project proved insufficient, which called for an urgent necessity to work out an additional reinforcement of preliminary lining, using forepoling as the arch support. Stability analyses of the tunnel with new lining were carried out on the basis of 3D numerical modeling of displacements and stresses around the tunnel.

Open access

Tadeusz Majcherczyk, Zbigniew Niedbalski and Łukasz Bednarek

Abstract

Back in the early 1980s, coal deposits occurring at depths of ~700 m below surface were already regarded as large-depth deposits. Meanwhile, today the borderline depth of large-depth mining has extended to >1,000 m. Design, excavation and maintenance of mining roadways at the depth of >1,000 m have, therefore, become crucial issues in a practical perspective in recent years. Hence, it is now extremely important to intensify research studies on the influence of large depths on the behaviour of rock mass and deformation of support in underground excavations. The paper presents the results of the study carried out in five mining excavations at depths ranging from 950 to 1,290 m, where monitoring stations with measurement equipment were built. The analysis of data from laboratory and coal mine tests, as well as in situ monitoring, helped to formulate a set of criteria for stability assessment of underground excavations situated at large depths. The proposed methodology of load and deformation prediction in support systems of the excavations unaffected by exploitation is based on the criteria referring to the depth of excavation and the quality of rock mass. The depth parameter is determined by checking whether the analysed excavation lies below the critical depth, whereas the rock mass quality is determined on the basis of the roof lithology index (WL) and the crack intensity factor (n)

Open access

Tadeusz Majcherczyk, Zbigniew Niedbalski, Piotr Małkowski and łukasz Bednarek

Abstract

The result of the search for new technological solutions in the field of support for roadways in coal mines has in recent years been the widespread use of steel arch with rockbolt support systems. The efficiency of these systems is affected among other things by the option of installing rock bolts after the actual driving the mine roadway, the increased load capacity that these systems can support, and their resistance to dynamic weight. Large variation in the way that these steel arch support can be connected using different types of rock bolts necessitates mining research revealing the effectiveness of such solutions. Although the steel arch with rockbolt support system is used in the majority of European coal mines, it is still not possible to apply templates of schemes due to the diversity of geological and mining conditions. Therefore, throughout a period of several years, the authors of this article conducted research in situ under conditions of different schemes related to connecting arched support frames with rock bolts, with only selected results being presented in the article. The measurements of convergence, load supported by the system frame, load supported by the rock bolts, and the stratification of roof rocks were analyzed, carried out in two roadways with yielding steel arch support in which strand bolts were applied. The article also proposes the index for working maintenance n uw , used in preliminarily assessing the stability of a given working with a limited number of data concerning geomechanical conditions. Additionally considered are empirical methods used in Poland for designing steel arch with rock bolt support systems.

The results of mine research indicate that strengthening yielding steel support with strand bolts through steel beams maintains the stability of a roadway, even when exposed to the exploitation stress. Aside from the impact of exploitation, deformations of the support system are negligible, despite the fact that the tensile forces acting on the rock bolts can reach values of up to 160 kN. Under favorable geological and mining conditions, support system frames can be spread up to 1.5 m apart when using rock bolts between them. The conducted measurement of convergence during a three year period revealed a compression amounting to a few centimeters. The results obtained by the research fully confirm the effectiveness of combined yielding steel arch with rock bolt support systems under different mining conditions.

Open access

Tadeusz Majcherczyk and Zbigniew Niedbalski

Abstract

The paper presents an analysis of seismic activity for selected areas of hard coal mine executing exploitation in a rock mass with a variable degree of rock disturbance, i.e., also with a varied number of previous mined-out seams. A distribution of vertical stress and a value of vertical stress concentration coefficient were also determined in the strata of immediate roof of the seams planned for mining. In the analyzed case, despite the lack of thick and solid strata of sandstones in the roof, the rock mass emits seismic activity, where the energy largely depends upon an impact of exploitation edges and tectonic disturbance.

Open access

Tadeusz Majcherczyk and Katarzyna Kryzia

Abstract

This article presents the impact of the retreat mining (i.e., involving an intended collapse of the excavation roof, subsequent to extraction) on the subsidence of the ground surface. The analysis was carried out for two areas of coal underground mining located in the Upper Silesian Coal Basin (Górnośląskie Zagłębie Węglowe). The assessment of the influence of exploitation on the ground surface was based on the results of geodetic measurements performed over a long period of time, whereas the land deformation prediction was made with the use of the EDNOPN program. The calculated and the predicted values were further compared, and the parameters of theory were determined. The results discussed in this paper have been shown by way of diagrams. The observed differences in the processes of vertical displacement were used in the analysis which took into account the degree to which the rock mass had been disturbed during the previous excavations, as well as the type of incumbent rock in the area under study.

Open access

Tadeusz Majcherczyk, Zbigniew Niedbalski and Artur Ulaszek

Abstract

The paper presents the application of a 3D laser measurement technology in a modern monitoring of roadways. The authors analyze the possibility of using a three-dimensional scanning measurement of longwall working dimensions. The measurement results are presented in the form of a cloud of points obtained from a 3D laser scanning. The paper also presents a comparison of the results obtained from the convergence of traditionally-made measurements with the measurements derived from the threedimensional scanning and discusses possible methods of comparing different point clouds.

Open access

Tadeusz Majcherczyk, Zenon Pilecki, Zbigniew Niedbalski, Elżbieta Pilecka, Mateusz Blajer and Joanna Pszonka

Wpływ warunków geologiczno-inżynierskich i geotechnicznych na dobór parametrów obudowy wstępnej tunelu drogowego w Lalikach

Tunel drogowy w Lalikach został wykonany w silnie niejednorodnych, w dużym stopniu zniszczonych tektonicznie i w przeważającej części bardzo słabych utworach fliszowych Karpat Zachodnich. W przeważającej części tunel był drążony w warunkach dużego udziału procentowego bardzo słabych łupków ilastych laminowanych i utworów strefy zwietrzelinowej, niekorzystnego, bardzo stromego nachylenia warstw skalnych i zmiennego zawodnienia z wypływami wody w rozluzowanych strefach tektonicznych. Górotwór ten charakteryzuje się dużą niepewnością rozpoznania jego właściwości i struktury.

Praca omawia wpływ warunków geologiczno-inżynierskich i geotechnicznych na dobór parametrów obudowy wstępnej tunelu drogowego. Przeprowadzono analizę deformacji obudowy wstępnej w zależności od procentowego udziału piaskowców i łupków, punktacji klasyfikacji geomechanicznych RMR (Bieniawski 1989) i QTS Tesařa (1979), typów obudowy wstępnej oraz wykorzystania kotew i mikropali. Analiza ta została poprzedzona charakterystyką warunków geologiczno-inżynierskich na trasie tunelu oraz charakterystyką typów zastosowanej obudowy wstępnej.

W trakcie drążenia tunelu z wyprzedzeniem w kalocie, kilkakrotnie występowały przemieszczenia obudowy wstępnej kaloty większe od projektowanych maksymalnych. Wprzypadku, gdy wartości deformacji osiągały stan alarmowy dla danego typu obudowy i nie wykazywały tendencji do stabilizowania się, podejmowano decyzję o jej wzmocnieniu dodatkowymi kotwami, siatką oraz torkretem do czasu osiągnięcia stabilizacji deformacji. W najtrudniejszych warunkach obudowa wstępna była wzmacniana parasolem mikropalowym. Parametry obudowy dobierano, zgodnie z zasadami NATM, na podstawie prowadzonych na bieżąco obserwacji geologiczno-inżynierskich i geotechnicznych.

Tunel w Lalikach jest przykładem bardzo słabej samonośności górotworu. Obserwowane przemieszczenia w górotworze wskazywały, że strefa spękań wokół wyrobiska była stosunkowo silnie rozwinięta. Obudowy wstępne stosowane w tego rodzaju warunkach, na niewielkich głębokościach, powinny charakteryzować się stosunkowo dużą nośnością.

Doświadczenia, jakie uzyskano wskazują, że realizacja obudowy wstępnej w silnie zmiennych warunkach fliszu karpackiego wymaga prowadzenia szczegółowych badań geologiczno-inżynierskich w trakcie drążenia tunelu, które należy wykonywać na bieżąco wraz z postępem dobowym dla weryfikacji założeń projektowych. W przypadku potrzeby należy zastosować wzmocnienia obudowy wstępnej na podstawie wyników właściwie prowadzonych pomiarów geotechnicznych zachowania się układu obudowa-górotwór.