Geomechanical safety assessment for transversely isotropic rock mass subjected to deep mining operations

2015 ◽  
Vol 52 (10) ◽  
pp. 1477-1489 ◽  
Author(s):  
W. Pytel ◽  
B. Pałac-Walko
Keyword(s):  
Rock Mass ◽  
Focal Mechanism ◽  
Geophysical Methods ◽  
Safety Margin ◽  
Main Roof ◽  
High Energy ◽  
Anisotropic Rock ◽  
Mining Operations ◽  
Safety Level ◽  
Transversely Isotropic Rock

The largest risk for mining operations conducted within the Legnica–Głogów Copper Basin is created mostly by high-energy tremors, the hypocenters of which are located within the main roof strata composed of sedimentary-type rocks — mainly dolomite and anhydrite — about 40–200 m above the excavated copper ore body. These categories of rock clearly exhibit anisotropic strength–deformation characteristics that may significantly affect the safety level value represented by the appropriate safety margin (or safety factor) based on an adequate strength hypothesis. As the focal mechanism most often encountered in such tremors is a slipping-type mechanism with a rupture plane, typically the Mohr–Coulomb theory of strength is applied for a safety level assessment in Polish copper mines. It has been assumed, however, that strength theories based on anisotropic failure criteria should serve as better indicators of correlation between observed and well-characterized sedimentary rock strata failure mechanisms and the location of concentrated areas of the negative values of margin of safety within the rock mass. As changing levels of stress in the rock mass during the mining process may be tracked effectively using solutions offered by appropriate three-dimensional geomechanical models (e.g., finite element method), the assessment of these changes due to mining-face progress is also possible in the location where the seismic tremor occurred. This assessment is characterized by its focal mechanism using the appropriate geophysical methods that permit finding such geomechanical conditions, engaging also the rock mass’ strain–stress states and the material anisotropic characteristics. On the basis of the long-term path of rock mass loading — due to mining predicted by numerical modeling — this could indicate the necessary conditions that should be fulfilled if the anticipated methods of the geophysics failure mechanism could be developed. This is particularly important for anisotropic rock structures. The proposed approach is illustrated using an example of a strong seismic energy event of 0.22 GJ that occurred in 2005 in an area of the Rudna mine.

scholarly journals High-energy seismic events in Legnica–Głogów Copper District in light of ASG-EUPOS data

2019 ◽  
Vol 107 (1) ◽  
pp. 25-40 ◽  
Author(s):  
Zbigniew Szczerbowski
Keyword(s):  
Rock Mass ◽  
Regional Scale ◽  
Geophysical Methods ◽  
Geodetic Network ◽  
High Energy ◽  
Tectonic Activity ◽  
Baseline Length ◽  
Seismic Events ◽  
Gnss Data ◽  
Mining Tremors

AbstractSeismic events in the area of Poland are related mostly to copper and coal mining, and they are regarded as the most dangerous natural hazard. Although development of geomechanical modelling as the development of geophysical methods determining seismic hazard are evident, low predictability of the time-effect relationship still remains. Geomechanical models as geophysical data analysis highlight the interaction between parts of rock mass or allow to reconstruct the way of rock mass destruction and to understand the processes that take place in the high-energy tremors.However, the association of larger mining tremors with pre-existing geological features has been reported by many investigators; in geomechanical practice, investigations of rock mass condition concentrate on this problem in the local scale. Therefore, the problem of relations between high-energy seismic events in Legnica–Głogów Copper District (LGCD) and regional scale deformations of terrain surface resulting from possible tectonic activity is discussed in this paper. The GNSS data evaluated from the observations of ASG-EUPOS (Active Geodetic Network – EUPOS) stations in the area of LGCD and in the adjacent areas is analysed in this study. Temporal variation of distances between the stations and evaluated on that base so called apparent strain was combined with the occurrence of high-energy tremors. Consequently, after the examination and analysis of occurrences of mining tremors, it is found that high-energy seismic events and periods of strain accumulation evaluated from GPS/GNSS data have temporal relations. Although the seismic events were triggered by mining, nearly all the events with energy E > 108 J occurred in the periods when the analysed stations’ positions demonstrated a decrease in the baseline length.

scholarly journals Optimization of Measuring Points Layout around a Tunnel in the Transversely Isotropic Rock Mass

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Zhizeng Zhang ◽  
Yongtao Li ◽  
Weili Yang ◽  
Shunchuan Wu ◽  
Xiaoli Liu ◽  
...  
Keyword(s):  
Rock Mass ◽  
Lateral Pressure ◽  
Back Analysis ◽  
Transversely Isotropic ◽  
Anisotropic Rock ◽  
Maximum Displacement ◽  
Transversely Isotropic Rock ◽  
Isotropic Rock ◽  
Anisotropic Rock Mass ◽  
Principle Of Maximum

The arrangement of measuring points has a great impact on the uniqueness and accuracy of the back analysis of displacement. To explore the arrangement method of measuring points in the anisotropic rock mass, the principle of maximum displacement is applied to study the optimization of measuring points layout around a tunnel in the transversely isotropic rock mass. Firstly, the criterion of maximum displacement is deduced. Secondly, the variations of displacement with angle and radius are analyzed, respectively, and two key lateral pressure coefficients are obtained. Thirdly, some principles of measuring points arrangement are summarized according to the criterion of maximum displacement. Finally, an example is given to prove the correctness of these principles. These principles can be used to guide the arrangement of displacement measuring points in the transversely isotropic rock mass, especially suitable for shaft excavation in horizontal sedimentary rock.

scholarly journals GEOPHYSICS APPLIED TO THE MAPPING OF NATURAL CAVES HOSTED IN IRON ORE IN CARAJÁS (PA), BRAZIL

2019 ◽  
Vol 37 (3) ◽  
pp. 249
Author(s):  
Maria Filipa Perez da Gama ◽  
Marco Antonio Braga ◽  
Marcelo Roberto Barbosa ◽  
Rafael Guimarães de Paula ◽  
Daniele Freitas Gonçalves ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Rock Mass ◽  
Geophysical Methods ◽  
Mining Operations ◽  
Near Surface ◽  
Geophysical Surveys ◽  
Iron Mine ◽  
Northern Brazil ◽  
Ground Penetrating ◽  
The Impact

 ABSTRACT. The Brazilian environmental licensing for mining activities requires technical-scientific studies to demonstrate that natural caves will be protected from the impact of the mining operations. This study presents the results of near-surface geophysical methods applied to geostructural mapping of the rock mass in which the caves are hosted. The ferruginous karstic terrains are challenging to the geophysical interpretation due to the caves’ modest dimensions and the large variations in the host rock physical properties. Electrical Resistivity and GPR (Ground Penetrating Radar) geophysical surveys, were performed overlaying a natural cave located in the surroundings of the N4EN iron mine, in the Carajás Province, northern Brazil. The resistivity data were useful to discriminate different lithotypes as well as the presence of humidity in the rock mass, while the GPR data revealed a detailed degree of fracturing of the rock mass. The presence of humidity and the highly fractured zones may constitute zones of greater fragility of the cave walls and ceiling.Keywords: speleology, GPR, electrical resistivity, near-surface geophysics.RESUMO. O licenciamento ambiental brasileiro para atividades de mineração requer que estudos técnico-científicos demonstrem que as cavernas serão protegidas do impacto das operações de mineração. Este artigo apresenta os resultados de métodos geofísicos rasos aplicados ao mapeamento geoestrutural do maciço rochoso em que as cavernas estão hospedadas. Os terrenos cársticos ferruginosos são desafiadores para a interpretação geofísica, devido às modestas dimensões das cavernas e às grandes variações nas propriedades físicas da rocha hospedeira. Levantamentos geofísicos de Resistividade Elétrica e GPR (Radar de Penetração no Solo) foram realizados sobre a uma caverna localizada no entorno da mina de ferro N4EN, na Província de Carajás, região Norte do Brasil. Os dados de resistividade foram úteis para discriminar diferentes litotipos, bem como a presença de umidade na massa rochosa, enquanto os dados de GPR revelaram em grau detalhado o fraturamento da massa rochosa. A presença de umidade e as zonas altamente fraturadas podem constituir zonas de maior fragilidade das paredes e teto da caverna.Palavras-chave: espeleologia, GPR, resistividade elétrica, geofísica rasa.

scholarly journals The Impact of the Coexistence of Methane Hazard and Rock-Bursts on the Safety of Works in Underground Hard Coal Mines

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 128
Author(s):  
Justyna Swolkień ◽  
Nikodem Szlązak
Keyword(s):  
Rock Burst ◽  
Methane Concentration ◽  
High Energy ◽  
Hard Coal ◽  
Coal Seams ◽  
Safety Level ◽  
Methane Drainage ◽  
Innovative Methods ◽  
Hard Coal Mining ◽  
The Impact

Several natural threats characterize hard coal mining in Poland. The coexistence of methane and rock-burst hazards lowers the safety level during exploration. The most dangerous are high-energy bumps, which might cause rock-burst. Additionally, created during exploitation, safety pillars, which protect openings, might be the reason for the formation of so-called gas traps. In this part, rock mass is usually not disturbed and methane in seams that form the safety pillars is not dangerous as long as they remain intact. Nevertheless, during a rock-burst, a sudden methane outflow can occur. Preventing the existing hazards increases mining costs, and employing inadequate measures threatens the employees’ lives and limbs. Using two longwalls as examples, the authors discuss the consequences of the two natural hazards’ coexistence. In the area of longwall H-4 in seam 409/4, a rock-burst caused a release of approximately 545,000 cubic meters of methane into the excavations, which tripled methane concentration compared to the values from the period preceding the burst. In the second longwall (IV in seam 703/1), a bump was followed by a rock-burst, which reduced the amount of air flowing through the excavation by 30 percent compared to the airflow before, and methane release rose by 60 percent. The analyses presented in this article justify that research is needed to create and implement innovative methods of methane drainage from coal seams to capture methane more effectively at the stage of mining.

Application of geophysical methods for the investigation of the large gravitational mass movement of Séchilienne, France

2005 ◽  
Vol 42 (4) ◽  
pp. 1105-1115 ◽  
Author(s):  
O Meric ◽  
S Garambois ◽  
D Jongmans ◽  
M Wathelet ◽  
J L Chatelain ◽  
...  
Keyword(s):  
Rock Mass ◽  
Mass Movement ◽  
Seismic Refraction ◽  
Geophysical Methods ◽  
Time Lapse ◽  
Gravitational Mass ◽  
Electrical Tomography ◽  
Refraction Tomography ◽  
Geophysical Surveys ◽  
Geophysical Techniques

Several geophysical techniques (electromagnetic profiling, electrical tomography, seismic refraction tomography, and spontaneous potential and seismic noise measurement) were applied in the investigation of the large gravitational mass movement of Séchilienne. France. The aim of this study was to test the ability of these methods to characterize and delineate the rock mass affected by this complex movement in mica schists, whose lateral and vertical limits are still uncertain. A major observation of this study is that all the zones strongly deformed (previously and at present) by the movement are characterized by high electrical resistivity values (>3 kΩ·m), in contrast to the undisturbed mass, which exhibits resistivity values between a few hundred and 1 kΩ·m. As shown by the surface observations and the seismic results, this resistivity increase is due to a high degree of fracturing associated with the creation of air-filled voids inside the mass. Other geophysical techniques were tested along a horizontal transect through the movement, and an outstanding coherency appeared between the geophysical anomalies and the displacement rate curve. These preliminary results illustrate the benefits of combined geophysical techniques for characterizing the rock mass involved in the movement. Results also suggest that monitoring the evolution of the rock mass movement with time-lapse geophysical surveys could be beneficial.Key words: gravitational movement, geophysical methods, Séchilienne.

scholarly journals Geophysical identification of voids and loosened zones in the shallow subsurface of post-mining areas

2018 ◽  
Vol 66 ◽  
pp. 01001 ◽  
Author(s):  
Zenon Pilecki
Keyword(s):  
Rock Mass ◽  
Geophysical Methods ◽  
Ore Deposits ◽  
Hard Coal ◽  
Shallow Subsurface ◽  
Mining Areas ◽  
Upper Silesian Coal Basin ◽  
Discontinuous Deformation ◽  
Ground Penetrating ◽  
Terrain Surface

The shallow historic exploitation of Zn-Pb/Fe ore deposits as well as hard coal has generated many discontinuous deformations on the terrain surface in the Upper Silesian Coal Basin/Poland. Discontinuous deformations occur in different forms as sinkholes, synclines, cracks, faults or ditches. The basic cause of their occurrence is the presence of void and loosened zones in the shallow subsurface. If the appropriate conditions arise, the sinkhole process begins to move upwards and may cause a discontinuous deformation on the terrain surface. Typically, geophysical methods are used for void and loosened zone identification. The most effective methods are gravimetric, seismic, electric resistivity and ground penetrating radar (GPR). Geophysical testing, requires distinct changes in the physical properties in the rock mass. The identified geophysical anomalies should be verified by control borehole and borehole tests to confirm the presence of the void and loosened zones in the rock mass. The results of control drilling and borehole tests determine the need to apply treatment works. In order to assess the threat of the occurrence of discontinuous deformations in the areas of historical shallow mining in Upper Silesia, a classification system based on geophysical tests has also been developed.

scholarly journals MODERNIZATION OF THE MINING SYSTEM OF SMALL DEPOSITS OF RICH COPPER PYRITE ORES

2020 ◽  
Vol 12 (3) ◽  
pp. 444-453
Author(s):  
Igor SOKOLOV ◽  
◽  
Yury ANTIPIN ◽  
Artem ROZHKOV ◽  
◽  
...  
Keyword(s):  
Mathematical Modeling ◽  
Rock Mass ◽  
Average Length ◽  
Thickness Variation ◽  
Chamber System ◽  
Mining Operations ◽  
Mining System ◽  
Ore Body ◽  
Experimental Block ◽  
Sublevel Caving

The purpose work. Substantiation and selection of a safe and effective option of mining technology of the experimental block in the pilot industrial mining of the Skalistoe deposit. Method of research. Analysis and synthesis of project solutions, experience in mining inclined low-thickness ore bodies, economic and mathematical modeling and optimization of the parameters of options mining systems in the conditions of the experimental block. Results of research. As a result of research it was established: - the sublevel caving mining system with the parameters adopted in the project does not guarantee the completeness of the extraction of reserves and the effectiveness of mining operations. Project indicators of extraction by sublevel caving technology with frontal ore drawing are overestimated and difficult to achieve in these geological and technical conditions (combination of low thickness and angle of ore body); project scheme for the delivery and transportation of rock mass seems impractical due to the significant volume of heading workings and increased transportation costs; - eight technically rational options of various mining systems were constructed, most relevant to the geological and technical conditions of the deposit. Five variants of the sublevel chamber system and pillar caving, a project variant of sublevel caving technology with frontal ore drawing and two options flat-back cut-and-fill system were considered; - for mining the Skalistoe deposit, according to the results of economic and mathematical modeling, optimal by the criterion of profit per 1 ton of balance reserves of ore is a option of the technology of chamber extraction with dual chambers, frontal drawing of ore by remote-controlled load-haul-dump machine and subsequent pillars caving, as having the greatest profit; - the calculations justified stable spans of dual chambers (25.3 m) and the width of panel pillars (3 m). With an allowable span of 25.3 m, the roof of the dual chambers will be stable with a safety factor of 1.41, and a panel pillar with a width of 3 m has a sufficient margin of safety (more than 1.6) in the whole range of ore body thickness variation; - the proposed scheme of delivery and transportation of rock mass, which allows to reduce the volume of tunnel works by 26% and the average length of transportation by 10-15% compared with the project. Findings. Developed in the process of modernization the technology sublevel chamber system with double-chamber, compared with the project technology, it is possible to significantly increase the efficiency of mining of the low thickness deposit of rich ores Skalistoe by reducing the specific volume of preparatory-rifled work by 34%, the cost of mined ore by 12%, losses and ore dilution – by 2 and 2.9 times, respectively.

Sign in / Sign up

Export Citation Format

Share Document