International audienceLaboratory pull-out tests were conducted on the following rock bolts and cable bolts: steel rebars, smooth steel bars, fiberglass reinforced polymer threaded bolts, flexible cable bolts, IR5/IN special cable bolts and Mini-cage cable bolts. The diameter of the tested bolts was between 16 mm and 26 mm. The bolts were grouted in a sandstone sample using resin or cement grouts. The tests were conducted under either constant radial stiffness or constant confining pressure boundary conditions applied on the outer surface of the rock sample. In most tests, the rate of displacement was about 0.02 mm/s. The tests were performed using a pull-out bench that allows testing a wide range of parameters. This paper provides an extensive database of laboratory pull-out test results and confirms the influence of the confining pressure and the embedment length on the pull-out response (rock bolts and cable bolts). It also highlights the sensitivity of the results to the operating conditions and to the behaviour of the sample as a whole, which cannot be neglected when the test results are used to assess the bolt-grout or the grout-rock interface

Based on extensive experience in shield support design and the results of underground measurements and observations, the major factors influencing the stability of the roof in retreat longwall panels were determined. A practical method for assessing the risk of roof falls is presented. It is a combination of empirical methods and expert techniques that enable investigators to determine the probability and potential consequences of roof falls. This report includes an example of applying the method to one longwall panel. The method is a practical decision tool to support the mining management when planning the roof fall preventive measures.

In Poland, the mining waste from underground coal mines is commonly deposited in surface dump sites, forming slopes or piles of materials dozens of meters high. Because of the loose structure of a mine waste dump slope, landslides may occur after a heavy rainfall. This requires significant labor costs in reforming the mine waste dump sites and disturbs the continuity of the depositing operations. Moreover, if the mine waste dump sites located in the built-up areas, such as in the Janina mine waste dump, landslides apparently can threaten even lives and properties. Therefore, a mine waste dump stability analysis is necessary for ensuring safety. In this paper, slope stability analysis was conducted using numerical modeling under the impact of rainfall for the Janina mine waste dump, located in Libiąż, Poland. The results indicated that slope tends to loose stability in case of high rainfall intensity and short duration. Then, slope reinforcement using soil nailing and steel mesh was proposed to prevent landslide under the impact of high rainfall intensity. Once again, slope stability analysis was carried out with selected reinforcement. Meanwhile, slope monitoring was performed to assess the slope reinforcement implementation at the Janina mine waste dumps against the impact of high rainfall intensity. Based on the modeling and monitoring outcomes, assessments of slope stability and selected landslide prevention measures for the Janina mine waste dump under the impact of rainfall were presented.

Dump fires are a significant environmental problem in post-mining areas. The TEXMIN project has shown that climate change could lead to more extreme weather events in the future, intense precipitation among them. The impact of water erosion on the development of endogenous fires in coal waste heaps has not been investigated thus far. Meteorological data collected from the studied dump area in Libiaz, Poland confirmed that heavy rainfall occurred many times, causing surface erosion on the slope. Gully erosion was observed on the western slope of the heap, the depth of which was up to 1.6 m. Data showed that between areas with and without water erosion, there was a significant difference in measured temperatures and gas concentrations that defined the fire intensity. Erosion facilitated self-heating such that internal temperatures increased to 52.9 degrees C. Further, at a depth of 1 m in the self-heating zone, maximum gas concentrations were 15.65 vol%. CO2 , 10 ppm CO, and 0.435 vol%. CH4 , while the O-2 concentration dropped below 1.0 vol%. These results show that despite preventative measures, thermal activity reactivated in the vicinity of gully erosion and caused the self-heating zone to expand.