Factors Influencing Rock Burst Hazard in Deep Copper Ore Mine, SW Poland

Abstract

In underground mines of copper ores, which are situated in Lower Silesia in SW Poland, the most common and dangerous threats pose seismic tremors and rock bursts. Copper ore exploitation is carried out in three mines, which are owned by KGHM Polish Copper JSC, i.e. Lubin mine, Rudna mine and Polkowice-Sieroszowice mine. Despite many rock burst preventive operations carried out over several decades of mining activity and aimed at counteracting seismic dynamic events, these phenomena have not been eliminated. The applied rock burst prevention measures only limit or mitigate the effects of seismic events. In mining, a concept of seismicity is used, which is defined as the tendency of an intact rock mass to seismic tremors induced by mining work in an area that was previously aseismic. Tremors and their results i.e. rock bursts affect not only excavations and underground infrastructure, but also the terrain surface. In the KGHM’s mines, seismic activity is monitored by the Mining Geophysics Stations. The number, coordinates and energy of tremors and rock bursts are registered, which helps determine the rock mass reaction to the adopted system and operation technology. The main purpose of the paper is to analyse seismic dynamic phenomena damaging mining excavations, i.e. rock bursts, in the Lubin mine, which took place from the beginning of the mine’s operation in 1975 to 2016 (over 41 years) and to identify and investigate geological and mining factors (parameters) facilitating the growth of seismic and rock burst hazards. The following factors (parameters) favourable for the occurrence of dynamic phenomena with damaging effects in excavations were taken into consideration: the seismic activity of the rock mass (spontaneous and provoked tremors), the deposit depth and thickness, geomechanical properties of rocks, exploitation systems, the method of elimination of mined-out space, the occurrence of gobs, tectonic disturbances and the life time of excavations. The results of the observation of selected parameters made it possible to determine the causes of rock bursts as well as to evaluate the impact of the exploitation system including the technology and rock burst prevention on seismic and rock burst hazard. Moreover, seismic activity of the mining division with the highest number and energy of rock bursts was analysed. The effectiveness of rock burst prevention measures used in this division was assessed too. The results of the analyses indicated some interdependencies between factors that may affect the phenomena discussed.

Hydrogen sulphide (H2S) migration in groundwater of the Zechstein strata in the Legnica-Głogów Copper Basin and its vicinity, SW Poland

“…Ver ti cal rock frac tures above the cop per-bear ing layer in the LGCB are the re sult of min ing ac tiv i ties, seis mic trem ors and rock bursts (Burtan, 2017;Gogolewska and Strzeszyñska, 2019). Some seis mic events in the study area are high-en ergy (Szczerbowski, 2019).…”

Tracking Deformation Processes at the Legnica Glogow Copper District (Poland) by Satellite InSAR—I: Room and Pillar Mine District

“…The mining-induced seismicity and related rock burst hazard may be the function of several parameters: in LGCD, the principal factors influencing the seismic hazard level (measured by the number of registered seismic events and the total seismic energy released) are the regional geological setting, i.e., the effective mining thickness and the thickness of burst-prone roof rock strata, and the possible variation of tectonic stress intensity [36]. Limestones and anhydrites that lie above the ore store elastic strain energy that can be released through fracturing and rock bursts [19]. Moreover, the depth of the excavations (that varies from 600 m up to 1200 m in LGCD) and the retreat mining method of excavation can provide favorable conditions for energy accumulation [64].…”

“…In the room-and-pillar system, the deposit bed is cut (using blasting technique) into rooms and belts, which create technological pillars. The operating pressure causes damages to these pillars [19], which can evolve following a rock burst. An intact rock mass can therefore be affected by seismic tremors induced by mining work in an area that was previously aseismic.…”

“…The related fracturing causes subsidence that affects not only excavations and underground infrastructure, but also the terrain surface. Therefore, the superficial ground deformation phenomena that can occur at active room and pillar mining districts can be related to both (i) land subsidence above the underground excavation rooms, produced at the advancing working face in the excavation direction (e.g., [20]) or due to yielding in the abandoned mines (e.g., [20]), and (ii) mining-induced tremors, related to post-pillar-failure disasters [19,20]. The effect of mining-induced tremors also results in a subsidence phenomenon, but it could take place in peculiar ways and times (e.g., [21]).…”

Tracking Deformation Processes at the Legnica Glogow Copper District (Poland) by Satellite InSAR—II: Żelazny Most Tailings Dam

“…During the Pleistocene, Central Europe was affected by at least three glaciations with relative progradation of glacial masses towards the south of Poland, where the study area is located [1, 29,39]. The thickness of the ice masses was at least 1000 m and the weight caused deformation phenomena (the so-called glacio-tectonics) that could have affected the subsoil up to hundred meters in depth [1,29].…”