Moment tensors of mining tremors: Detection tool of the mode of rock-mass fracturing

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.

Download Full-text

THE EFFECT OF TEMPERATURE OF ROCKS ON MICROCLIMATIC CONDITIONS IN LONG GATE ROADS AND GALLERIES IN COAL MINES

Archives of Mining Sciences ◽

10.2478/amsc-2014-0014 ◽

2014 ◽

Vol 59 (1) ◽

pp. 189-216 ◽

Cited By ~ 1

Author(s):

Janusz Cygankiewicz ◽

Józef Knechtel

Keyword(s):

Rock Mass ◽

Coal Extraction ◽

Effect Of Temperature ◽

Coal Oxidation ◽

Temperature Changes ◽

Air Stream ◽

Finite Differences Method ◽

Microclimatic Conditions ◽

Rock Mass Fracturing

Abstract The aim of this study was to examine the effect of the temperature of surrounding rocks on enthalpy and temperature of air flowing along several model mine workings. Long workings surrounded by non- -coal rocks as well longwall gates surrounded by coal were taken into consideration. Computer-aided simulation methods were used during the study. At greater depths the amount of moisture transferred into a mine working from the rock mass is two orders of magnitude smaller than the moisture that comes from external (technological) sources, mainly from coal extraction-related processes, therefore in the equation describing temperature changes only the terms representing the flux of heat from rocks were included. The model workings, for calculation purposes, were divided into sections, 50 m in length each. For each of the sections temperature of its ribs and temperature and stream of enthalpy of air flowing along it were calculated with the use of the finite differences method. For workings surrounded by non-coal rocks two variant calculations were carried out, namely with or without technological sources of heat. For coal surrounded workings (longwall gates) a new method for determination of heat from coal oxidation was developed, based on the findings by Cygankiewicz J. (2012a, 2012b). Using the results of a study by J.J. Drzewiecki and Smolka (1994), the effects of rock mass fracturing on transfer of heat into the air stream flowing along a working were taken into account.

Download Full-text

An Analysis Of The Interaction During Simultaneous Use Of Copper Ore And Salt Deposits In The LGOM Mines With Regard To Displacement And Deformation Of Rock Mass

Archives of Mining Sciences ◽

10.1515/amsc-2015-0035 ◽

2015 ◽

Vol 60 (2) ◽

pp. 535-548

Author(s):

Edward Popiołek ◽

Zdzisław Kłeczek ◽

Zygmunt Niedojadło ◽

Ryszard Hejmanowski ◽

Wojciech Skobliński ◽

...

Keyword(s):

Rock Mass ◽

Land Surface ◽

Mineral Resources ◽

Theoretical Models ◽

Mining District ◽

Copper Ore ◽

Rock Mass Deformation ◽

Mining Works ◽

Mining Tremors ◽

The Impact

Abstract Excavation of the two bedded deposits of mineral resources in a small vertical distance may cause additional increased mining risks (rock mass deformation, rock bursts and mining tremors, threat to land surface). This paper considers the impact of excavation of the copper ore deposit on the bed of rock salt located above it and the opposite, in terms of displacements and deformations. We used the theoretical models of processes verified by previous in situ observations in the mines of the Legnica-Głogów Copper Mining District. We analysed the potential for reducing the risks, among others, through coordination of mining works.

Download Full-text

Land Surface Subsidence Due to Mining-Induced Tremors in the Upper Silesian Coal Basin (Poland)—Case Study

Remote Sensing ◽

10.3390/rs12233923 ◽

2020 ◽

Vol 12 (23) ◽

pp. 3923

Author(s):

Paweł Sopata ◽

Tomasz Stoch ◽

Artur Wójcik ◽

Dawid Mrocheń

Keyword(s):

Rock Mass ◽

Land Surface ◽

Continuous Monitoring ◽

Geological Structure ◽

Vertical Surface ◽

Coal Basin ◽

Surface Displacements ◽

Upper Silesian Coal Basin ◽

Mining Tremors

Seismic phenomena threaten land-based buildings, structures, and infrastructure and can transform land topography. There are two basic types of seismic phenomena, namely, tectonic and anthropogenic, which differ mainly in epicenter depth, surface impact range, and magnitude (energy). This article shows how a land surface was changed by a series of seven rock mass tremors of magnitude ML = 2.3–2.6 in March–May 2017. Their immediate cause was the “momentary” acceleration of void clamping, which was activated by local and short-term seismic phenomena caused by human activity. The induced seismic events resulted from the geological structure of the rock mass, which in the specific region of examination was classified as being highly prone to mining tremors. The authors focused on describing vertical surface displacements in the Upper Silesian Coal Basin in the south of Poland. The surface deformations were identified using DInSAR technology, which allows quasi-continuous monitoring of large areas of land surface. The present research used freely available data from the Copernicus Program and seismic data from the European Plate Observing System.

Download Full-text

Classification Method and Application of Rock Fracture Ability by Supercritical CO2 Blasting

Shock and Vibration ◽

10.1155/2022/7973016 ◽

2022 ◽

Vol 2022 ◽

pp. 1-11

Author(s):

Xiaohong Zhu ◽

Jianhong Jia ◽

Zhongwei Cai

Keyword(s):

Rock Mass ◽

Supercritical Co2 ◽

Evaluation Method ◽

Cloud Model ◽

Rock Fracture ◽

Evaluation Index System ◽

Classification Theory ◽

Classification Method ◽

Entropy Weight ◽

Rock Mass Fracturing

In order to study the fracture ability classification of rock mass under the cracking action of supercritical CO2 phase transition, based on the classification theory of rock mass in blasting engineering, an analytic hierarchy process (AHP)-entropy weight method (EWM) and the cloud model classification method for rock mass cracking under CO2 phase transformation are proposed. In this method, rock density, rock tensile strength, rock wave impedance, and rock mass integrity coefficient are used as the factors to determine the level of rock mass fracturing, and the evaluation index system of rock mass fracturing is established. Through this evaluation method, the rock mass in a reconstruction project section of Nyingchi, Tibet, is classified and evaluated. The results present that this new classification method of rock mass fracture ability uses AHP–EWM to carry out the weight distribution of the classification index. In addition, it is combined with the cloud model for the classification division, overcoming the traditional classification method fixed with appraisal pattern flaw. Therefore, it has validity and feasibility. According to the characteristics of fracture ability, the rock masses in the area to be rebuilt on the Tibet Highway are divided into grade II, grade III, and grade IV, which provides scientific guidance for the construction of the project.

Download Full-text

Multiconfiguration GPR measurements for geometric fracture characterization in limestone cliffs (Alps)

Geophysics ◽

10.1190/1.2194526 ◽

2006 ◽

Vol 71 (3) ◽

pp. B85-B92 ◽

Cited By ~ 57

Author(s):

Mathieu Jeannin ◽

Stéphane Garambois ◽

Colette Grégoire ◽

Denis Jongmans

Keyword(s):

Rock Mass ◽

Test Site ◽

Fracture Characterization ◽

Rock Stability ◽

Transmission Data ◽

Velocity Image ◽

Maximum Penetration ◽

Rock Mass Fracturing ◽

Ground Penetrating

Rock-mass fracturing is a key parameter in rock-fall hazard assessment. However, traditional geologic observations can provide information only about discontinuities at the surface. In this case study, detailed ground-penetrating-radar (GPR) measurements (with antennas of [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text]) were conducted on a test site, using different acquisition configurations deployed on vertical cliff faces. Conventional 2D profile data, common-midpoint (CMP) survey data, and transmission data were acquired to evaluate the potential use of radar waves to characterize the geometry and properties of the major discontinuities (fractures) within a Mesozoic limestone massif. Results showed that the continuity and geometry (orientation and dip) of the major observed fractures, which are crucial parameters for assessing rock stability, can be obtained by combining vertical and horizontal profiles measured along the cliff. We used [Formula: see text] antennae and reached a maximum penetration of [Formula: see text], which limits the technique to rock volumes of a few tens of thousands of cubic meters. We observed significant differences in reflectivity along the detected fractures, which suggests that the fractures’ characteristics vary in the rock mass. We used transmission data to obtain a radar velocity image. Although the results were consistent with radar profiles on the cliff, they showed that the technique has little utility, beyond that of more traditional GPR methods, for delineating fractures in a rock mass.

Download Full-text