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. Keywords: mine roadways, mining support, stability of roadways, rock mass monitoring 642Efektem poszukiwania nowych rozwiązań technologicznych w zakresie obudowy wyrobisk korytarzowych w kopalniach węgla kamiennego, jest w ostatnich latach dość powszechne stosowanie obudowy podporowo-kotwowej. Na jej efektywność wpływa miedzy innymi możliwość zabudowy kotew w późniejszym okresie niż drążenie wyrobiska, uzyskiwanie dużej nośności, czy odporność na obciążenia dynamiczne. Duża liczba możliwych do zastosowania wariantów połączeń obudowy podporowej z kotwami o różnej kon...

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Assuring the stability of underground headings in order to fulfill their technical functions without any disturbance and provide a safe workplace for mining staff seems to be a fundamental issue in mining activity. In recent years, rockbolts: bar or cable have been most frequently applied as a means of reinforcement. Such a construction is often referred to as a stand-and-roofbolting support. The paper presents sample results of monitoring stand-and-roof-bolting support systems selected from numerous research projects carried out by the authors. The results discussed below are based on the measurements of the strength parameters of rocks in the laboratory and in-situ research, convergence of underground excavations, forces in rockbolts, separation of roof rock strata tested with extensometric probes, telltales and endoscopes, as well as steel yielding support frames load tested with dynamometers. The complex measurements of stand-and-roof-bolting supports along with specifications of geological, mining and geomechanical conditions allowed to formulate a proper evaluation of support behavior and its effectiveness for particular conditions.

Geomechanical data are never sufficient in quantity or adequately precise and accurate for design purposes in mining and civil engineering. The objective of this paper is to show the variability of rock properties at the sampled point in the roadway’s roof, and then, how the statistical processing of the available geomechanical data can affect the results of numerical modelling of the roadway’s stability. Four cases were applied in the numerical analysis, using average values (the most common in geomechanical data analysis), average minus standard deviation, median, and average value minus statistical error. The study show that different approach to the same geomechanical data set can change the modelling results considerably. The case shows that average minus standard deviation is the most conservative and least risky. It gives the displacements and yielded elements zone in four times broader range comparing to the average values scenario, which is the least conservative option. The two other cases need to be studied further. The results obtained from them are placed between most favorable and most adverse values. Taking the average values corrected by statistical error for the numerical analysis seems to be the best solution. Moreover, the confidence level can be adjusted depending on the object importance and the assumed risk level.