Underground spaces having features such as stability, resistance, and being undetected can play a key role in reducing vulnerability by relocating infrastructures and manpower. In recent years, the competitive business environment and limited resources have mostly focused on the importance of project management in order to achieve its objectives. In this research, in order to find the best balance among cost, time, and quality related to construction projects using reinforced concrete in underground structures, a multi-objective mathematical model is proposed. Several executive approaches have been considered for project activities and these approaches are analyzed via several factors. It is assumed that cost, time, and quality of activities in every defined approach can vary between compact and normal values, and the goal is to find the best execution for activities, achieving minimum cost and the maximum quality for the project. To solve the proposed multi-objective model, the genetic algorithm NSGA-II is used.
The paper presents an analysis of overvoltages caused by a direct lightning strike in intrusion detection system equipped with underground radiating cable sensors. Waveforms of currents and voltages in the system components are calculated using analytical formulas basing on a transmission-line model in the frequency domain. The time-domain waveforms are computed using the inverse fast Fourier transform (IFFT). Three network configurations of the intrusion detection system are analyzed.
The coal exploitation in the Upper Silesia region (along the Vistula River) triggers the strata seismic
activity, characterized by very high energy, which can create mining damage of the surface objects, without
any noticeable damages in the underground mining structures. It is assumed that the appearance of the
high energy seismic events is the result of faults’ activation in the vicinity of the mining excavation. This
paper presents the analysis of a case study of one coal mine, where during exploitation of the longwall
panel no. 729, the high energy seismic events occurred in the faulty neighborhood. The authors had analyzed
the cause of the presented seismic events, described the methods of energy decreasing and applied
methods of prevention in the selected mining region. The analysis concluded that the cause of the high
energy seismic events, during the exploitation of the longwall panel no. 729 was the rapid displacements
on the fault surface. The fault’s movements arose in the overburden, about 250 m above the excavated
longwall panel, and they were strictly connected to the cracking of the thick sandstone layer.
The propagation of EM waves in soil is defined by permittivity and permeability which are in turn affected by the soil parameters such as soil moisture and texture. Therefore, a suitable Dielectric Model like MBSDM is required for the channel characterization of WUSN. Effect of soil parameters and environmental conditions on signal propagation is modelled using Superposition Model. The simulation of these stages is done in MATLAB for UG-UG, UG-AG and AG–UG scenarios. The system is further implemented on the ZYNQ ZC–702 hardware platform.
The main optimized objects in underground mines include: stope layout, access layout and production scheduling. It is common to optimize each component sequentially, where optimal results from one phase are regarded as the input data for the next phase. Numerous methods have been developed and implemented to achieve the optimal solution for each component. In fact, the interaction between different phases is ignored in the tradition optimization models which only get the suboptimal solution compared to the integrated optimization model. This paper proposes a simultaneous integrated optimization model to optimize the three components at the same time. The model not only optimizes the mining layout to maximize the Net Present Value (NPV), but also considers the extension sequence of stope extraction and access excavation. The production capacity and ore quality requirement are also taken into account to keep the mining process stable in all mine life. The model is validated to a gold deposit in China. A two-dimensional block model is built to do the resource estimation due to the clear boundary of the hanging wall and footwall. The thickness and accumulation of each block is estimated by Ordinary Kriging (OK). In addition, the conditional simulation method is utilized to generate a series of orebodies with equal possibility. The optimal solution of optimization model is carried out on each simulated orebody to evaluate the influence of geological uncertainty on the optimal mining design and production scheduling. The risk of grade uncertainty is quantified by the possibility of obtaining the expected NPV. The results indicate that the optimization model has the ability to produce an optimal solution that has a good performance under the uncertainty of grade variability.
One of the most critical aspects of mine design is to determine the optimum cut-off grade. Despite Lane’s theory, which aims to optimize the cut-off grade by maximizing the net present value (NPV), which is now an accepted principle used in open pit planning studies, it is less developed and applied in optimizing the cut-off grade for underground polymetallic mines than open pit mines, as optimization in underground polymetallic mines is more difficult. Since there is a similar potential for optimization between open pit mines and underground mines, this paper extends the utilization of Lane’s theory and proposes an optimization model of the cut-off grade applied to combined mining-mineral processing in underground mines with multi-metals. With the help of 3D visualization model of deposits and using the equivalent factors, the objective function is expressed as one variable function of the cut-off grade. Then, the curves of increment in present value versus the cut-off grade concerning different constraints of production capacities are constructed respectively, and the reasonable cut-off grade corresponding to each constraint is calculated by using the golden section search method. The defined criterion for the global optimization of the cut-off grade is determined by maximizing the overall marginal economics. An underground polymetallic copper deposit in Tibet is taken as an example to validate the proposed model in the case study. The results show that the overall optimum equivalent cut-off grade, 0.28%, improves NPV by RMB 170.2 million in comparison with the cut-off grade policy currently used. Thus, the application of the optimization model is conducive to achieving more satisfactory economic benefits under the premise of the rational utilization of mineral resources.
The paper describes experimental investigations of vibrations caused by train passages in the shallow underground tunnel (in Warsaw, Poland) in comparison to the results of measurements of vibrations from ground surface transportation (trams and buses). Propagation of surface ground vibrations from underground tunnel is presented. The problem of dynamic response of a building and influence of vibrations caused by underground on people residing in a building is discussed as well. The dynamic response of the building to underground vibrations is essentially different from the response of a building excited by surface sources of transport vibrations. Also the distribution of influence of the transport vibrations on people in the building is significantly different in both cases.
This article concerns numerical modeling of the impact of mining operations on fault behavior, carried out on the basis of a calculation program based on the finite element method. It was assumed that the fault is a single discontinuity in the form of a vertically-oriented plane, and the conditions in which surfaces merge are defined by the right of the Coulomb friction. On the one hand, the calculations are related to the fault’s response to additional weight resulting from mining operations, and on the other, they are related to the impact that occurrences in the fault’s plane had on the immediate surroundings of the extraction center. The behavior of the fault was analyzed based on distributions in the plane of shear stress and slip, together with their range and energy dissipated due to friction. In turn, the impact of the fault on its immediate environment was analyzed based on variations in the total energy density of elasticity. The results of numerical modeling made it possible to draw conclusions concerning mining operation in the proximity of tectonic dislocations in the context of seismic hazard’s levels.
With reference to the situation experienced in several Polish collieries where the risk of occurrence of gas-geodynamic phenomena is increasing and decisions to start the mining activities need to take numerous constraints associated with previous mining into account, this paper addresses certain geo-mechanical aspects of longwall mining in the zones of excavation edge interactions giving rise to major changes in the conditions of the deposit and rock strata, as a consequence of previous mining operations in adjacent coalbeds. Starting from the analytical description of displacements and stresses in the proximity of longwall mining systems, the paper summarizes the results of model tests and investiga-tions of the influence that the excavation edge has on the behavior and structural continuity of a portion of the coal body in the coalbed beneath or above an old excavation. Based on selected nonlinear functions emulating the presence of edges in the rock strata, a comparative study is carried out by investigating two opposite directions of workface advance, from the gob area towards the coal body and from the coal body towards the gobs. The discussion of the results relies on the analysis of roof deformation and the concentration factor of the vertical stress component at the workface front.
The current rockburst hazard conditions in the copper mines are the consequence of mining-induced seismicity of the rock strata whilst the majority of registered rockbursts have been caused by high-energy seismic events. T he analysis of seismic activity in recent years indicates that the region of the Rudna mine is the region of the highest seismic activity. This paper is an attempt at evaluating the seismicity levels in the Rudna mine in the period from 2006-2015, within the entire mine and in its particular sections. Key parameters of seismic activity include the number of registered seismic events, total energy emission levels, and a unit energy factor. The variability of Gutenberg -Richter (GR) parameters are analyzed and the epicenters’ locations are investigated with respect to the stope position. T he distinction is made between low-energy (103 ≤ As < 105 J) and high-energy (As ≥ 105J) seismic events ahead of the stope, in the opening-up cross-throughs and in the gob areas. It appears that the risk level of a high-energy event occurrence in the R udna mine has not changed in recent years and has remained on a high level whilst the differences in seismic activity, in particular mine sections, are attributed to the varied extraction height and varied thickness of rockburst-prone carbonate layers in the roof of the copper ore deposit. The analysis of the epicenters’ locations with respect to the stope reveals that no matter what the seismic energy levels, the largest number of rockbursts are registered in the opening-up cross-through zone. Low-energy tremors are mostly located in the gob areas, high-energy events occur mostly ahead of the stope. T hus, the evaluation of the seismicity conditions in the Rudna mine seems to positively verify the relationship between the number of registered events and the levels of generated seismic energy, taking the local geological and mining conditions and the specificity of the room and pillar mining method into account.
Mining-induced seismicity, particularly high-energy seismic events, is a major factor giving rise to dynamic phenomena within the rock strata. Rockbursts and stress relief events produce the most serious consequences in underground mines, are most difficult to predict and tend to interact with other mining hazards, thus making control measures difficult to implement. In the context of steadily increasing mining depth within copper mines in the Legnica-Głogów Copper Belt Area (Poland) alongside the gradually decreasing effective mining thickness, a study of the causes and specificity of mining-induced seismicity in specific geological and mining settings may improve the effectiveness of the prevention and control measures taken to limit the negative impacts of rockbursts in underground mine workings, thus ensuring safe working conditions for miners. This study investigates the presumed relationship between the mined ore deposit thickness and fundamental parameters of mining-induced seismicity, with the main focus on the actual locations of their epicenters with respect to the working face in commonly used room-and-pillar systems. Data recalled in this study was supplied by the O/ZG Rudna geophysics station. Based on information about the actual ore deposit thickness in particular sections of the mines (Rudna Główna, Rudna Północna, Rudna Zachodnia) and recent reports on seismic activity in this area, three panels were selected for further studies (each in different mine region), where the ore deposit thickness was varied (panel G-7/5 – Rudna Główna, panel XX/1 – Rudna Północna, panel XIX/1 – Rudna Zachodnia). Data from seismic activity reports in those regions was used for energetic and quantitative analysis of seismic events in the context of the epicenter location with respect to the selected mining system components: undisturbed strata, working face and abandoned excavations. In consideration of the available rockburst control methods and preventive measures, all events (above 1 × 103 J) registered in the database were analysed to infer about the global rockburst hazard level in the panel and phenomena induced (provoked) by blasting were considered in order to evaluate the effectiveness of the implemented control measures.
This article presents the results of experimental studies aimed at identifying the forces and acceleration during the riding and braking action of a suspended monorail. The tests were conducted under in situ conditions, in a dip-heading “B” ZG SILTECH in Zabrze. The paper also discusses a test stand, a metering system, and presents the impact of changes in speed on forces in slings of the suspended route. The measurements of selected parameters were performed for three variants: the route, the emergency haulage braking and the braking trolley set braking. The results include waveforms of forces in route slings, and acceleration values acting on the operator and transported load.
The stability of gateroads is one of the key factors for the mining process of hard coal by a longwall system. Wrong designed and applied the gateroad support at the stage of drilling, may adversely affect the functionality of the gateroad and the safety of the crew throughout its existence.
The article presents the results of the underground tests and observations such as: convergence of the gateroad, stratification and the fractured zone range in the roof rocks, carried out in four longwall gateroads at the stage of their drilling.
The obtained test results were the basis for the assessment of the possibility of using a convergence control method in the design of the gateroad support. The method is based on three interdependent relationships, such as: Ground Reaction Curve (GRC), Longitudinal Displacement Profile (LDP), and a Support Characteristic Curve (SCC). All calculations were performed using numerical modeling in the Phase2 program, based on the finite element method (FEM).
Geodesic measurements of mining area deformations indicate that their description fails to be regular,
as opposed to what the predictions based on the relationships of the geometric-integral theory suggest.
The Knothe theory, most commonly applied in that case, considers such parameters as the exploitation
coefficient a and the angle of the main influences range tgβ, describing the geomechanical properties of the
medium, as well as the mining conditions. The study shows that the values of the parameters a = 0.8 and
tgβ = 2.0, most commonly adopted for the prediction of surface deformation, are not entirely adequate in
describing each and every mining situation in the analysed rock mass. Therefore, the paper aims to propose
methodology for determining the value of exploitation coefficient a, which allows to predict the values
of surface subsidence caused by underground coal mining with roof caving, depending on geological and
mining conditions. The characteristics of the analysed areas show that the following factors affect surface
subsidence: thickness of overburden, type of overburden strata, type of Carboniferous strata, rock mass
disturbance and depth of exploitation. These factors may allow to determine the exploitation coefficient a,
used in the Knothe theory for surface deformation prediction.