Mining Tremors Research Articles

The Specificity of Dynamic Resistance of Existing Bridge Structures in Mining Areas

The article presents the results of a dynamic resistance analysis of selected existing bridge structures. The numerical calculations performed with the use of THA (time history analysis) pertained to road and rail bridges of steel and concrete structures—not paraseismically designed. The purpose of the work was to determine the dynamic resistance of objects to the influence of paraseismic impacts resulting from mining operations. The specificity of performing calculations in this area of engineering issues is presented. Real mining tremor signals, registered in the vicinity of the objects were used in the numerical analyses. The correct determination of the dynamic resistance of the object can be used as a basis for performing repair/strengthening of existing objects, which in the future will be loaded with additional paraseismic influences.

The influence of distant coal seam edges on seismic hazard during longwall mining

Underground coal seam mining has been carried out in the Upper Silesian Coal Basin, Poland, for many years and with a simultaneous increase in exploitation depth. Frequently, coal seams are not fully extracted due to numerous reasons which lead to their edges and remnants remaining in the rock mass. Even in the case of the full extraction of a coal seam, mining usually ends at the border of a protecting pillar to protect underground or surface objects, sometimes at the border of the mining area, or some distance from the old goaf or high throw fault. Extraction of subsequent coal seams in an analogous range results in a cluster of coal seam edges remaining. In the vicinity of the mentioned remainders, the disrupted stress distribution is expected. The infraction of the aforementioned equilibrium repeatedly results in the occurrence of strong mining tremors. The observations from the studied coal seam no. 408’s longwall panel indicated that mining works are able to disturb the present stress-strain equilibrium in the area of the edges of other coal seams, even if they are located at a greater vertical distance away. The seismological parameters and distributions have been applied for this purpose.

High-rate GPS positioning for tracing anthropogenic seismic activity: The 29 January 2019 mining tremor in Legnica- Głogów Copper District, Poland

High-rate GNSS observations are usually studied in relation to earthquake analysis and structural monitoring. Most of the previous research on short-term dynamic deformations has been limited to natural earthquakes with magnitudes exceeding 5 and amplitudes equal to several dozen centimetres. High-frequency position monitoring via GNSS stations is particularly important in mining areas due to the need to monitor mining damages. On 29 January 2019 (12:53:44 UTC), an M3.7 event occurred in the area of Legnica-Głogów Copper District.This study presents GPS-derived displacement analysis in relation to seismological data. Station position time series were determined by double differencing and Precise Point Positioning. The peak ground displacement was 2–14 mm. The correlation coefficients between GPS and seismological displacement time series reached 0.92. A statistical evaluation of GPS displacement time series was carried out to detect an event using only GPS observations.

Mining-triggered seismicity governed by a fold hinge zone: The Upper Silesian Coal Basin, Poland

Mining tremor mechanisms and principal stress directions were analysed in order to compare characteristics of seismic events and stress regimes with tectonic settings in the Bytom Syncline, located in the Upper Silesian Coal Basin. The results of seismic moment tensor inversion calculated for 41 events with magnitudes > M2.0 were used to trace changes in types of mechanism (normal, strike-slip, reverse) with the progress of mining from Panel 3, coal seam 503, Bobrek Mine. The data was sourced from the IS-EPOS Platform, an open data infrastructure for the study of anthropogenic hazards linked to georesource exploitation. The foci were located below the seam and followed a longwall excavation. The computed mechanisms and distribution of spatial-temporal events enabled three clusters representing three different stages of stress regimes to be distinguished. The calculated principal stress axes indicated the main stress directions present in the studied area, enabling a local model of the derivative pattern of neotectonic deformation to be described. The regime changed from horizontal extension in the syncline limb (first cluster) to transpression (second cluster) to dominating compression in the hinge (third cluster), resulting in reverse fault production. Finally, the results revealed the causes of seismicity in the studied area and showed that the studied events had been mostly triggered.

A comprehensive geomechanical method for the assessment of rockburst hazards in underground mining

Rockburst hazard in mining industry all over the world is one of the most severe hazards. It is becoming increasingly common because of the ever-growing depths of mining operations accompanied by the increasing strength of rocks. One of the most difficult issues is to predict this hazard before the mining operations, whether geophysical investigations have been conducted or not. Polish experience in this field shows that in such cases an effective solution can be the geomechanical method. Therefore, extensive studies on rockburst hazard should focus on three main aspects: (1) rock mass and rock (and coal) predisposition to rockburst–laboratory tests and empirical analyses based on lithology, (2) identification of the potential places with stress and elastic energy concentration in the rock mass within the area planned for exploitation, and (3) the assessment of the impact of mining tremors on the surface. This preliminary geomechanical analysis assesses the propensity of the rock mass to dynamic breakage and provides quantitatively the level of rockburst hazard. The paper presents Polish experience in rockburst hazard assessment with the use of geomechanical method, as well as some solutions and examples of such analyses.

Identification of the ground movements caused by mining-induced seismicity with the satellite interferometry

Abstract. The assessment of the impact of mining-induced seismicity on the natural environment and infrastructure is often limited to the analysis of terrain surface vibrations. However, similar seismic phenomena, like earthquakes, may also imply dislocations and deformations of the rock mass. Such ground movements may occur in areas which are not directly under the influence of the mining. The study of the displacement field caused by mining-induced seismicity is usually carried out with the use of geodetic methods. Classical geodetic measurements provide discrete information about observed ground movements. As a result, they generally do not provide spatially and temporally relevant estimates of the total range and values of ground movements for specific periods of interest. Moreover, mining-induced seismicity causes a severe threat to buildings. That is why, regarding the complexity of the mechanism of occurrence of mining-induced seismicity and their impact on ground movements, this problem remains a substantial research issue. The presented research aimed to analyse the ground movements caused by mining-induced seismicity. The ground displacements were established based on data from Sentinel-1 satellites applying differential interferometric synthetic aperture radar (DInSAR). The results of the investigation in the copper mining area of the Lower Silesia region of Poland revealed that the observed subsidence caused by mining-induced seismicity usually has a shape of a regular ellipse. The radius of these ground movements does not exceed approximately 2–3 km from the mining-induced tremor's epicenter, and the total subsidence reaches ca. 10–20 cm. More than 50 % of the total subsidence is observed on the surface within a few days after the mining tremor occurrence. Furthermore, the deformations of the surface occur when the energy of mining-induced tremor reaches values of the order of 105 J or higher. The presented research can contribute to better identification and evaluation of the mechanism of the rock mass deformation process caused by mining-induced seismicity. In addition, the use of satellite radar interferometry improves the quality of monitoring of these dynamic phenomena significantly. The data retrieved using this method allow for quasi-continuous monitoring of the local subsidence bowls caused by mining-induced seismicity.

Wahania zwierciadła wód podziemnych pod wpływem wstrząsów górniczych w obszarze górniczym kopalni Rydułtowy

Groundwater level changes caused by influence of mining tremors – case study from the Rydu³towy Mine Area (Poland). A b s t r a c t. In 2018, as part of the implementation of a European project: European Plate Observing System (EPOS-PL), a hydrological monitoring system was installed in a Rybnik test site. The system is configured to measure changes of groundwater level caused by seismic events which were induced by mining exploitation. The piezometers were drilled within an active mining area, in close vicinity to mining longwalls of the Rydultowy Coal Mine, an industrial partner in the project. The paper presents the state of knowledge on the phenomena of co-seismicity in hydrology, a description of installed measuring system, and the first hydrographs registered for mining tremors with a local magnitude from 2.7 to 3.1, which occurred up to 3 km away from the location of piezometers.

Co-seismic signals of mining tremors in continuous recordings of gravity by gPhoneX tidal gravimeters

Co-seismic signals of mining tremors in continuous recordings of gravity by gPhoneX tidal gravimeters

Directional Attenuation Relationship for Ground Vibrations Induced by Mine Tremors

The paper presents the discussion on problems involving the reproduction of the acceleration field of ground vibrations based on the pointwise registration carried out in coal mines subjected to seismic hazard. Simple model that takes into account directional effects of seismic wave attenuation has been presented. It has been accepted the assumption that the contours of the peak ground accelerations take the shape of an ellipse. The carried out calculations for three cases of very strong ground vibrations caused by mine tremors which occurred in three regions of coal mines, show that the application of the proposed model allows us to reduce the value of standard error of the estimate as compared to the results obtained with the commonly applied regression model, which does not allow for the directional effects of attenuation. For the investigated regions, it was showed, that the directional effects of the attenuation depends on the directions of the nearest big tectonic faults.

Directional Attenuation Relationship for Ground Vibrations Induced by Mine Tremors

Directional Attenuation Relationship for Ground Vibrations Induced by Mine Tremors

Study on characteristics of EP responsing to coal mining

Geophysical methods have been applied for monitoring and forecasting dynamic failure of coal rock in mining engineering widely. Previous researches indicate that electric potential (EP) signals are produced during the deformation and fracture process of coal rock under load, which are closely related to the stress state and damage evolution. On this base, the response of EP signal characteristics of coal seam to mining activity were tested and analyzed. The results showed, with the advancing of mining face, the stress state of coal mass near EP measuring point transited from the original stress zone to the stress concentration and distressed zones. It led to the increase of loading stress and damage degree of coal mass, resulting in the fluctuation and enhancement of EP strength. The response trend of EP exhibited great correspondence with the regular monitoring indexes. Besides, the phenomenon of periodic pressure also caused the abnormal response of EP. Furthermore, before the occurrence dynamic failure (mine tremor), the EP signals showed significant precursory warning characteristics. It was verified by monitoring the results of electromagnetic radiation (EMR). The study indicates the prospect of applying EP monitoring to evaluate the stress state and early warning of dynamic coal rock failure.

The ratio of response spectra from seismic-type free-field and building foundation vibrations: the influence of rockburst parameters and simple models of kinematic soil-structure interaction

Mining-related seismicity is a significant problem in regions with the exploitation in underground mines. Despite the fact that mining tremors result from human activity and are classified as so-called paraseismic shocks, as with earthquakes, they are random events. Moreover, these rockbursts could cause significant damage to surface structures, including buildings. This paper deals with the analysis of experimentally obtained results in terms of the differences between the mine-induced vibrations described by the response spectra from the free-field near a given building and the simultaneously recorded vibrations in the building foundations. The influences of epicentral distance, mining tremor energy and the value of peak ground acceleration on the curves of free-field—foundation response spectra ratio were studied. The impact of the type of building on the transmission of response spectra from the free-field vibrations to the building foundations was also analysed for three types of apartment buildings (low-rise, medium-rise, high-rise). The usefulness of the approximate models of the phenomenon of soil-structure interaction during earthquakes proposed in the literature is also estimated in this paper in specific instances of mining tremors. Furthermore, the study presents original, simple, empirical models for the evaluation of the differences in the response spectra originating from free-field and building foundation vibrations in the mining region.

Experimental study on models of cylindrical steel tanks under mining tremors and moderate earthquakes

The aim of the study is to show the results of complex shaking table experimental investigation focused on the response of two models of cylindrical steel tanks under mining tremors and moderate earthquakes, including the aspects of diagnosis of structural damage. Firstly, the impact and the sweep-sine tests have been carried out, so as to determine the dynamic properties of models filled with different levels of liquid. Then, the models have been subjected to seismic and paraseismic excitations. Finally, one fully filled structure has been tested after introducing two different types of damages, so as to verify the method of damage diagnosis. The results of the impact and the sweep-sine tests show that filling the models with liquid leads to substantial reduction in natural frequencies, due to gradually increasing overall mass. Moreover, the results of sweep-sine tests clearly indicate that the increase in the liquid level results in significant increase in the damping structural ratio, which is the effect of damping properties of liquid due to its sloshing. The results of seismic and paraseismic tests indicate that filling the tank with liquid leads initially to considerable reduction in values of acceleration (damping effect of liquid sloshing); however, beyond a certain level of water filling, this regularity is inverted and acceleration values increase (effect of increasing total mass of the structure). Moreover, comparison of the responses under mining tremors and moderate earthquakes indicate that the power amplification factor of the mining tremors may be larger than the seismic power amplification factor. Finally, the results of damage diagnosis of fully filled steel tank model indicate that the forms of the Fourier spectra, together with the frequency and power spectral density values, can be directly related to the specific type of structural damage. They show a decrease in the natural frequencies for the model with unscrewed support bolts (global type of damage), while cutting the welds (local type of damage) has resulted in significant increase in values of the power spectral density for higher vibration modes.

Impact of seismic-type shock parameters on the soil-structure interaction effect in the USC mining region

The paper deals with seismic-type surface and building vibrations randomly occurring as a result of rockbursts in mining regions (random events as with earthquakes). The focus is on the problem of ground vibrations transmission to building foundation – it is one of very important phenomenon associated with soil-structure interaction effect. One of the ways of estimation of possible differences between simultaneously developing free-field vibrations next to a building and building foundation vibrations, i.e. using a ratio of response spectra (RRS), is applied to this study. Analysis concerns the ratio of dimensionless and dimensional acceleration response spectra (β and Sa) – denoted as RRS(β) and RRS(Sa), respectively. Horizontal vibrations parallel to the transverse (x) and longitudinal (y) axis of the representative (typical) two-storey, masonry office building are discussed. Calculations are based on the results of in situ surface vibration measurements performed in the seismically active Upper Silesian Coalfield (USC) mining area in Poland (long-term, full-scale monitoring). Evaluation of the dependence of the curves of ratio of response spectra on some parameters corresponding to mine-induced vibrations (i.e. epicentral distance, mining shock energy, peak value of free-field vibrations) is executed. From the obtained results, it can be definitely concluded that the influence of the most important mining tremor parameters (i.e. epicentral distance, mining shock energy, peak value of free-field vibrations) on the ratio of response spectra calculated in the successive ranges of these parameters, is clearly observed.

Exact solutions of generalized thermoelastic medium with double porosity under L–S theory

In this paper, a general solution to the field equations of a generalized thermoelastic medium with double porosity has been obtained. To investigate the problem, we use the Lord–Shulman theory in the thermoelasticity. The half-space of an isotropic homogeneous thermoelastic material is considered. Using the normal mode analysis and the numerical inversion technique, the analytic expressions of the physical quantities are obtained. Numerically, computed results for these quantities and its depicted graphically lead to study the effect of porosity. Comparisons in the presence and absence of double porosity, in two different times, are obtained. Although the problem has been solved theoretically, it is possible for researchers to benefit from their results in many different sciences, for example, in the field of geophysics, earthquake engineering, along with seismologist working in the field of mining tremors and drilling into the crust of the earth.

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

Abstract Seismic 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.

Application of a Small Baseline Subset Time Series Method with Atmospheric Correction in Monitoring Results of Mining Activity on Ground Surface and in Detecting Induced Seismic Events

The article presents the results of applying a Small Baseline Subset (SBAS) method to the monitoring of the influence of underground mining exploitation on terrain surface. Calculations were performed on the basis of two large SAR data sets. Calculations of time series additionally employed the Tymofyeyeva and Fialko empirical method for estimating atmospheric delay. A series of test calculations allowed verifying the potential of the method. The SBAS calculations were based on theoretical data prepared with the use of the Mogi model. This approach allowed simulating both underground mining exploitation and induced tremors. The results indicate that the model is useful in detecting sudden ground surface deformations. In such a situation, the image of a tremor can be observed in the atmospheric component. The actual data used in the analysis covered a region of underground copper ore extraction in southwest Poland. The calculations were based on SAR data obtained from the Sentinel 1A/B satellites, for the period between the end of 2014 and May 2018, from paths 22 and 73. In both cases, the total number of images exceeded 120. They served to calculate over 420 interferograms for each set. The results of ground surface displacements allowed precise identification of areas affected by underground mining activity. Over the acquisition period of six days, sufficient amount of SAR data was obtained to precisely monitor surface changes in the analyzed area. The employed empirical atmospheric delay reduction method was demonstrated to enable the detection of sudden ground surface changes due to mining tremors. This feature makes the method useful in detecting induced seismic events in areas characterized by intensive mining activity. It allows determining tremor locations in cases when acquisition dates are greater than the optimal value of 6–12 days (in the case of Sentinel 1A/B).

Investigation of post inducted seismic deformation of the 2016 MW 4.2 Tarnowek Poland mining tremor based on DinSAR and SBAS method

Investigation of post inducted seismic deformation of the 2016 MW 4.2 Tarnowek Poland mining tremor based on DinSAR and SBAS method

Forecast and assessment of the effects of the impact of mining tremors, induced by exploitation, on building objects with the use of GIS system

The article presents an analysis of the possibilities of using the GIS (Geographic Information System) class system to forecast and assess the impact of mining tremors on buildings located on the surface. The research was conducted with reference to the scope of activities which should be carried out by the mining entrepreneur, conducting exploitation in conditions of seismic hazard, specified in the Rules for the use of the GSIS-2017 mining seismic intensity scale. Due to the fact that the implementation of the mining tasks in a coal mine requires the processing of a huge number of information, deriving from different sources, it can be considered that it is a deliberate use of the GIS class systems. The article presents an analysis of the possibilities of using the GIS class systems based on a database developed in the ArcGIS system, containing observation material from the area of one of the coal mines, operating in the area of the Upper Silesian Coal Basin. The research has shown that the ArcGIS tooling system allows for the implementation of almost all tasks in the scope of the assessment of the mining tremors impact, including documenting damage to objects. In the case of tasks concerning forecasting the support programs are required.

Source Analysis of Post-Blasting Events Recorded in Deep Copper Mine, Poland

Seismic and rock burst hazard is a very important factor that has to be considered in seismically active mining areas. Several different methods are used to decrease seismic activity in mines. Among others, an active prevention method known as destress blasting, is considered the most effective technique. The aim of this work is to find possible influences of such active prevention on observed seismic activity recorded in the established waiting time after blasts. Using technological knowledge and seismic data recorded by an underground seismic network, we estimated several parameters that characterize sources provoked by blasting works and compared them with the parameters obtained for spontaneous, non-provoked mining tremors. According to our studies the source mechanisms of post-blasting seismicity are characterized by the similar non-DC part of the full moment tensor whereas the source mechanisms of spontaneous events are not characterized by any specific features. On the other hand non-provoked seismicity presents lowest values of apparent stress. Also ES to EP ratio suggest some differences between events occurred immediately after blasting (up to 30 s) and the rest dataset. We believe that these parameters could be considered valuable tools supporting established safety time limitations after active prevention.