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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The constantly growing, broadly understood, construction industry requires the use of a large amount of aggregates. The construction of roads, motorways, railway lines and hydrotechnical structures requires the use of aggregates of high quality, which is primarily determined by mechanical properties. The basic parameters describing mechanical properties of aggregates are the Los Angeles (LA) fragmentation resistance coefficient and the Micro-Deval (MDE) abrasion resistance coefficient. The LA and MDE coefficients depend mainly on the type of rock and its physical and mechanical properties. This has been thoroughly researched and documented as evidenced by the abundant literature in the field. However, the correlation between LA and MDE coefficients still gives rise to extensive discussions and some concerns. A number of publications demonstrate dependencies for various types of aggregates. Therefore, research was undertaken to present statistical analysis for one type of aggregate and one geological area.This article presents the results of the fragmentation resistance test in the Los Angeles drum and the abrasion resistance test in the Micro-Deval drum of aggregates from Carpathian sandstone deposits. Aggregate samples were divided into three groups according to the location of the deposits and the tectonic unit from which they originated. The obtained results were subjected to static analysis to fit the best mathematical function describing the relationship between the two parameters.

The phenomenon of the floor upheaval occurs in virtually every type of rock mass and at every depth, accompanying the process of excavation of tunnels and headings. Despite its inconvenience, it is rarely studied because of the complexity of the process and the multiplicity of the factors causing deformations in floor rocks. To quantify the effect of the selected factors on floor upheaval, this article presents an analysis of results of in situ measurements carried out in three coal mine roadways at 15 measuring stations. These measurements were taken over varying periods of time, between 129 and 758 days. Groundwater and fault zones intersecting the excavations were considered as the key factors that affect floor upheavals. Therefore, the measurement bases were located at local faults and sites of water inflow. To compare the results, the stations were also located where the rock mass was not exposed to any factors other than stresses resulting from the depth of the excavation. The excavations were driven in various rocks and were located at different depths from 750 to 1010 m. The analyses of the study results show that the floor upheaval always depends on time and can be described in polynomial form: ufl = a·t2 + b·t + c or by a power function: ufl = a·tb. However, the further regression analyses show that roadway’s floor upheaval can be expressed by a complex form using the key parameters determining the phenomena. In the absence of an impact of geological factors on the stability of the excavation, the floor upheaval depends on floor rocks compressive strength σc and Young’s modulus E: ln(ufl)=a·ln(tσc)−bE−c; in the case of rock mass condition affected by water depends on the rock compressive strength reduction after submerging rock in water σcs 6h: ufl=a·t0.5−bσcs 6hσc+c and in the case of fault depends on the fault’s throw f: ufl=a·t0.8+b·f1.2−c. Statistical analysis has shown that the matching of the models to the measurement data is high and amounts to r = 0.841–0.895. Hence, in general, the analysis shows that the floor upheaval in underground excavation in any geological conditions may grow indefinitely.

One of the most important elements of road construction is its substructure, which constitutes the base on which the next layers of road are placed. Mixture of crushed-stone aggregate is very often used as material for substructure. The most frequently used type of aggregate is magma rocks, due to its good physical-mechanical properties. However, it is not always available, so it is substituted by sandstone or even concrete rubble aggregates. The bearing ratio CBR is a parameter determining the suitability of a certain aggregate for road substructure. It is also one of the most popular quality tests of aggregate as it does not require complex apparatus. This paper analyses the results of physical and geotechnical tests with particular focus on CBR bearing ratio of crushed aggregates and their application as substructure for road construction. There has also been an attempt to find the correlation between CBR bearing ratio and other physical and geometrical properties.

Underground salt mining accounts for about 16 percent of the total salt production worldwide. When excavating salt rock, the cutters of the road header come into contact with the rock. This produces friction and, consequently, a rise in temperature. Generally, as temperature increases, salt gradually loses its plasticity. The extent of these alterations depends on the presence of other minerals in the rock. This paper presents the results of laboratory tests on regularly shaped samples of salt. An analysis was performed of the results of compressive, tensile and induced-shear strength, and of Young's modulus, Poisson's ratio, cuttability index and side chipping angle. The testing was conducted on samples with a temperature of about 20°C and samples heated to 50°C and 80°C. The tests showed that as temperature increased, so did compressive and tensile strength, and longitudinal and transverse strain of salt. The temperature increase caused, however, a decrease in shear strength. The cuttability index and the side chipping angle also decreased when the heated samples were being cut. The percentage changes in the parameters within the 60-degree temperature range were as high as several dozen percent.

Ensuring the stability of mining excavations is a crucial aspect of underground mining. For thispurpose, appropriate shapes, dimensions, and support of workings are designed for the given mining andgeological conditions. However, for the proper assessment of the adequacy of the used technical solutions,and the calibration of the models used in the support design, it is necessary to monitor the behavior of theexcavation. It should apply to the rock mass and the support. The paper presents the automatic systemdesigned for underground workings monitoring, and the example of its use in the heading. Electronicdevices that measure the rock mass movements in the roof, the load on the standing support, and on bolts,the stress in the rock mass, are connected to the datalogger and can collect data for a long of time withoutany maintenance, also in hard-to-reach places. This feature enables the system to be widely used, inparticular, in excavations in the vicinity of exploitation, goafs, or in the area of a liquidated exploitationfield.

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