We investigate the problem of setting revenue sharing rules in a team production environment with a principal and two agents. We assume that the project output is binary and that the principal can observe the level of agents’ actual eort, but does not know the production function. Identifying conditions that ensure the eciency of the revenue sharing rule, we show that the rule of equal percentage markups can lead to ination of project costs. This result provides an explanation for project cost overruns other than untruthful cost reporting.
Recalling the body of experience gathered in the collieries of the Upper Silesian Coal Basin, the
increased risk of seismicity and rockburst occurrences in confined conditions including the exploitation of
remnants were identified. This study investigates geomechanical aspects of longwall mining in the areas
affected by old excavations aimed at relaxation of a multi-bed deposits within a thick coal seam or a group
of seams. It is assumed that high-energy seismicity is another factor determining the rockburst hazard
alongside the state of stress. A case study is recalled, describing a colliery where mining-induced seismic
activity of a de-stressed coal seam remained at the level comparable to or higher than it was experienced
in the de-stressed seam operations. An analytical model was used to study the stress state and potential
loss of structural continuity of an undisturbed rock body surrounding the longwall panel being mined
beneath or over the abandoned workings. Recalling the developed model of the system involving nonlinear
functions demonstrating the existence of abandoned mine workings within the rock strata, computer
simulations were performed to evaluate the rockburst hazards along the face area. Discussions of results
are based on observations of immediate roof convergence and the vertical stress concentration factor at
the longwall face zone. Computational data of the modelled mining situations demonstrates that despite
using the de-stressing method of mining, the occurrence of events impacting on mine working beneath
and over abandoned workings cannot be precluded. Here the scale of rockburst hazards is determined by
local mining and geological conditions, such as the type and extent of abandoned workings, their age and
vertical distance between them and the coal seam currently mined.
Predicted climate change may have negative impact on many environmental components including vegetation by increase of evapotranspiration and reduction of available water resources. Moreover, a growing global population and extensive use of water for irrigation and industry result in increasing demand for water. Facing these threats, quantitative and qualitative protection of water resources requires development of tools for drought assessment and prediction to support effective decision making and mitigate the impacts of droughts. Therefore, the Institute of Meteorology and Water Management, National Research Institute has developed and implemented a set of tools for the operational drought hazard assessment. The developed tools cover drought indices estimation, assessment of sensitivity to it formation and drought hazard prediction. They are streamlined into an operational scheme combined with data assimilation routines and products generation procedures.
A drought hazard assessment scheme was designed to be implemented into the platform of a hydrological system supporting the operational work of hydrological forecast offices. The scheme was launched to run operationally for the selected catchments of the Odra River and the Wisla River basins. The crucial resulting products are presented on the website operated by IMWM-NRI: POSUCH@ (Operational System for Providing Drought Prediction and Characteristics) (http://posucha.imgw.pl/). The paper presents the scheme and preliminary results obtained for the drought event which began in August 2011.
This paper considers electric shock hazard due to induced sheath voltages in 110 kV power cables. The purpose of this paper is to find an optimal configuration of the power cable system, taking into account electric shock hazard and ability of the system to transfer maximal power. A computer simulations on a computer model of the local power system, comprising high voltage power cables, were carried out. This model enables to analyse various configurations of the metallic cable sheaths bonding and earthing (singlepoint bonding, both-ends bonding, cross-bonding) and their impact on induced voltages in the cable sheaths. The analysis presented in the paper shows, that it is possible to find an optimal configuration of the complicated power cable system, in terms of electric shock hazard, maximal power transfer as well as economic aspects.
Methane is accompanied by most of the coal deposits. The methane hazard is excessive content of this gas in the mining excavations. This is a source of high risk security and continuity of the mine. The Piast–Ziemowit is the only non-methane mine in the Polish Mining Group. In 2015, 66,4% of the coal mined in Kompania Węglowa S.A. mines comes from methane coal seams. Methane drainage is the most effective but very costly method of combating methane hazard.The costs of prevention and eradication of methane hazard is charged to the costs of coal mining. Therefore, performance of methane drainage in the mines of the Polish Mining Group is adapted to the scale of the methane hazard. The article presents an analysis of the costs of prevention of methane hazard for mines with different absolute methane and its impact on the level of these costs.
A proper description of ground motions generated by seismic and paraseismic events requires gathering data of six components of seismic waves. T hree of them, the so called translational waves, are well researched and identified. Unfortunately, until recently, the remaining three components named as rotational waves were generally estimated with the use of indirect methods based on theoretical calculations. T his was related mostly with the lack of proper instruments for the recording of rotational seismic waves. T hus, rotational waves were not fully recognized thus far. Recently, several types of advanced instruments for direct measurements of rotation were invented. Based on the measurements of strong ground motions it was indicated that the amplitude of the rotational components in close distances from the seismic source can be significantly larger than expected. Apart from this, there is still a lack of analyses considering the characteristic of rotational seismic waves generated by induced seismic events. In this paper, the results of preliminary measurements of rotational motions generated by induced seismic waves were presented. Ground movements related with mining tremors were analyzed in terms of amplitude, frequency and duration.
The underground mining of coal deposits in the Upper Silesian Coal Basin (GZW) re-sults in an imbalance in the distribution of the stress in the rock mass, both in the immediate and distant surroundings of mining excavations. The occurrence of seismic tremors, among others, is the consequence of this process,. The intensities of seismic phenomena, which occur in several regions of the GZW (Bytomian Basin, Main Saddle, Main Basin, Kazimierzowska Basin, and the Jejkowice Basin) are very diverse, ranging from tremors unrecognizable by humans to strong tremors of the nature of weak earthquakes (Patyńska and Stec 2017). During the period of 15 years, i.e. from 2001 to 2015, the level of seismic activity changed and de-pended on both the intensity of the excavation work and the variability of the lithological and tectonic structures. On the other hand, the seismic activity analysis has shown that in recent years, despite a decrease in total output, seismic activity and rockburst hazard have increased. One of the rea-sons was the increase in mining output. Almost half of the output came from coal seams under the rockburst hazard. This resulted in an increase in the number of great energy tremors with the energy of 107, 108 and 109 J. It has been shown that the amount of energy tremors has a high impact on the level of the rockburst hazard. Between 2001 and 2015, as many as 20 rockburst were caused by seismic tremors above 107 J with 42 total phenomena (Patyńska 2002–2016). The purpose of characterizing the causes of this phenomenon was determined by the parameters characterizing the structure of the rock mass in places where the rockburst was recorded.
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.
The introduction of the article presents the problem of interpreting the level of fire hazard basing on Graham’s ratio, which, in certain ranges of the value of its denominator, may be wrong. The range of credibility for the index is also discussed. The issue of nitrogen inertisation and its influence on the value of the discussed index is also addressed. To determine the influence, two statistical samples were set. They consisted of the results of precise chromatographic analyses of the air samples collected in the longwall areas which were not subjected to inertisation and in the areas where nitrogen was applied as the inert gas. Then, with Student’s t-test, there was conducted a comparative analysis of both groups with regard to the equality of the average concentrations of gases emitted in the coal self-heating process. At the end, there were developed criteria for the application of Graham’s ratio for the air samples of the increased content of nitrogen, which, according to the discussed index, did not indicate the occurrence of an endogenous fire hazard.
There are about 8.5 million workers employed in the construction sector in India. Construction workers constitute a major portion of the unorganized labour and are characterized by their casual nature of employment, temporary relationship with the employer, prolonged and uncertain working hours, lack of safety and health measures, and inadequacy of basic amenities and welfare facilities. There are many legislation clauses providing safeguards for contract workers in India. Construction safety has been made legally enforceable after the enactment of The Building and Other Construction Workers (Regulation of Employment and Conditions of Service) Act in 1996 and the Central Rules in 1998. This paper details various statutory provisions for construction safety in India with specific reference to the BOCW Act, Central Rules, and State Rules.
The construction industry in India is the country’s second largest industrial sector, after agriculture. The construction industry makes a remarkable contribution to the Indian economy and provides employment to a large number of people of Idia. Fire is a chemical reaction of a combustible substance with oxygen, involving heat and is usually accompanied by a visual flame or incandescence. Ensuring fire safety has always been a challenge to the stakeholders, i.e. building owners, construction companies, contractors and sub-contractors, and government employees due to the multiplicity of the factors involved and their complexity. There are various legal standards and requirements for ensuring fire safety on construction sites. The buildings are normally provided with firewalls during construction and these firewalls separate two structures or divide a structure into smaller portions to prevent the spread of fire. The lightweight construction and trusses are designed to support only their own weight. During a fire, if one fails, a domino effect happens and all fail rapidly within 5 to 10 minutes. Prolonged exposure to fire may result in structural collapse and injury or death of the occupants of the building under construction. Fire safety on construction sites is still in its primitive stages in India. There is a great necessity to improve fire safety on construction sites to protect construction workers and other occupants of the buildings. This study aims to design and implement fire safety systems for construction sites, thereby enhancing the standards to meet the system requirements at par with global standards.
This paper describes the concept of controlling the advancement speed of the shearer, the objective
of which is to eliminate switching the devices off to the devices in the longwall and in the adjacent
galleries. This is connected with the threshold limit value of 2% for the methane concentration in the
air stream flowing out from the longwall heading, or 1% methane in the air flowing to the longwall.
Equations were formulated which represent the emission of methane from the mined body of coal in the
longwall and from the winnings on the conveyors in order to develop the numerical procedures enabling
a computer simulation of the mining process with a longwall shearer and haulage of the winnings. The
distribution model of air, methane and firedamp, and the model of the goaf and a methanometry method
which already exist in the Ventgraph-Plus programme, and the model of the methane emission from the
mined longwall body of coal, together with the model of the methane emission from the winnings on
conveyors and the model of the logic circuit to calculate the required advancement speed of the shearer
together all form a set that enables simulations of the control used for a longwall shearer in the mining
process. This simulation provides a means for making a comparison of the output of the mining in the
case of work using a control system for the speed advancement of the shearer and the mining performance
without this circuit in a situation when switching the devices off occurs as a consequence of exceeding
the 2% threshold limit value of the methane concentration. The algorithm to control a shearer developed
for a computer simulation considers a simpler case, where the logic circuit only employs the methane
concentration signal from a methane detector situated in the longwall gallery close to the longwall outlet.
Priority wise channelization of resources is the key to successful environmental management, especially when funds are limited. The study in hand has successfully developed an algorithmic criterion to compare hazardous effects of Municipal Solid Waste (MSW) dumping sites quantitatively. It is a Multi Criteria Analysis (MCA) that has made use of the scaling function to normalize the data values, Analytical Hierarchy Process (AHP) for assigning weights to input parameters showing their relevant importance, and Weighted Linear Combination (WLC) for aggregating the normalized scores. Input parameters have been divided into three classes namely Resident’s Concerns, Groundwater Vulnerability and Surface Facilities. Remote Sensing data and GIS analysis were used to prepare most of the input data. To elaborate the idea, four dumpsites have been chosen as case study, namely Old-FSD, New-FSD, Saggian and Mahmood Booti. The comparison has been made first at class levels and then class scores have been aggregated into environmental normalized index for environmental impact ranking. The hierarchy of goodness found for the selected sites is New-FSD > Old-FSD > Mahmood Booti > Saggian with comparative scores of goodness to environment as 36.67, 28.43, 21.26 and 13.63 respectively. Flexibility of proposed model to adjust any number of classes and parameters in one class will be very helpful for developing world where availability of data is the biggest hurdle in research based environmental sustainability planning. The model can be run even without purchasing satellite data and GIS software, with little inaccuracy, using imagery and measurement tools provided by Google Earth.
The present study addresses the utilization of induction furnace steel slag which is an anthropogenic waste, for enhancing the mechanical properties of a commercial aluminium alloy A356. Different weight percentage (3wt%, 6wt%, 9wt%, and 12wt%) of steel slag particles in 1 to 10 μm size range were used as reinforcing particles in aluminium alloy A356 matrix. The composites were prepared through stir casting technique. The results revealed an improvement in mechanical properties (i.e. microhardness and tensile strength) and wear resistance with an increase in weight percentage of the steel slag particles. This research work shows promising results for the utilization of the steel slag for enhancing the properties of aluminium alloy A356 at no additional cost while assisting at same time in alleviating land pollution.
Subnetwork with two nodes shared with entire ventilation network can be separated as its part. For the network under common ventilation conditions, one of these nodes will become the subnetwork starting node, while the other will be the subnetwork end node. According to the graphs theory, such a piece of the network can be considered as a subgraph of the graph representing the entire ventilation network. A special feature of that subgraph is lack of predecessors of the subnetwork starting node and lack of successors of the subnetwork end node. Ventilation district of a mine may be often treated as a subnetwork. Vicinity is a part of the network which is not separated as subnetwork. In the case of a ventilation district its vicinity forces air flow through the district. The alternative characteristic curve of the vicinity can therefore be compared to the characteristics curve of a fictional fan that forces the airflow in the district.
The alternative characteristics (later in the text: the characteristics) of the vicinity of the ventilation district in an underground mine strongly influence air quantity and therefore play a crucial role in the reduction of methane, fire and thermal hazards. The role of these characteristics and proper selection of their approximating function were presented in the article.
The reduction of resistance of an intake stopping (having influence on entire resistance of a ventilation district) produces increased airflow in the district. This changes of airflow in the district caused by a variation in internal resistance (e.g. by opening an internal regulation stopping) depends on the characteristic of the vicinity of the district. Proper selection of its approximating function is also important for this matter.
The methods of determination of the alternative characteristic curve of the district vicinity are presented. From these procedures it was possible to obtain the results of air quantities and differences in isentropic potentials between an inlet and an outlet to/from the ventilation district. Following this, the characteristics were determined by graphic and analytic methods. It was proved that, in contrast to flat vicinity characteristics, steep ones have a smaller influence on the airflow modification in the district (which are caused by a regulation of the district resistance). The characteristic curve of the vicinity determines the ability to regulate air quantity and velocity in the district.