Underground monitoring as the best way of roadways support design validation in a long time period
Piotr Małkowski1, Zbigniew Niedbalski1, Tadeusz Majcherczyk1, Łukasz Bednarek1
1AGH University of Science and Technology, Krakow, 30-059, Poland
Min. miner. depos. 2020, 14(3):1-14
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Purpose. The aim of this paper is to show the importance of geotechnical monitoring in assessing stability of an underground excavation. Every mining excavation is designed on the basis of limited geotechnical data and with some physical assumptions.
Methods. The monitoring in the brought up herein cases covered the rock mass and the support, and was carried out over a period of 6 years. Three long-term roadways in the hard coal mine, and with different support schemes, were studied. The monitoring methods included: convergence measurements, roof bed separation control, load on standing support and load on bolts.
Findings. The obtained results of the displacements of the roof rocks were highly affected by the type of the used support, roof stratification, and a rock strength. The more cracked and stratified were the roof rocks the stronger was the separation and the movement towards the excavation. The steel arch support sets with the bullflex bags lining can restrain this effect, but not the roof bolting with strand bolts grouted segmentally deep in the roof.
Originality.Rock mass and support monitoring of such a large scope, which was the subject of this research, is very seldom carried out in underground mining. Moreover, it was conducted over an exceptionally long period of six years. Five different techniques were used to assess the roadway’s stability. Such a long-term monitoring and investigation allowed to find the relationships between the support scheme of the excavation and the rock mass movements around it.
Practical implications. A long-term monitoring allowed for a development of the deformation characteristics of the rock mass, defining the time of secondary equilibrium, and determination of the strain of the support elements. This, in turn, allowed for a verification of the correctness of selection of the support, installed in specific mining and geological conditions.
Keywords: rock mass monitoring, mining support monitoring, excavation stability, in-situ measurements, numerical modelling verification
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