This paper presents an analysis of the influence of burden deviation from the designed one on the intensity of blasting vibrations through the use of laboratory and field examinations. By definition, ...the burden represents the shortest distance from the axis of an explosive column charge to the free surface. It should be measured along the entire hole length, although, in practice, it is often measured only on the bench surface as the shortest distance from the axis of the explosive column charge to the crest. The real surface of the bench slope (free face) can be very irregular and should be considered during every blast. The deviation of burden in the blast pattern represents a serious problem in the field during blasting operation. Burden deviation from the designed one can be greater or lesser, affecting the results of blasting through poor fragmentation and sometimes causes unwanted effects like increased blasting vibrations or fly rock. The influence of burden deviation on the intensity of blasting vibrations was tested on a laboratory model, where 8 mm diameter holes were drilled into blocks with certain dimensions. The small explosive charges placed in blastholes were initiated. The design burden was set at 30 mm, as the distance from blastholes to the free face of the blocks. Any deviation in distance greater than the designed burden was taken as a parameter for comparison. During each initiation, vibrations were measured using a seismic instrument at a distance of 150 mm from the borehole. At the same time, the free face in the front of the blastholes was photographed to create a detailed 3D model of the blasted surface of the blocks for each blasting. Each measurement is presented on a diagram and classified depending on the values of the burden in the cases where the value of the burden is equal to the designed one, as well as any deviation that is smaller or larger than 30 mm. A total of 55 tests were carried out. The results were analyzed, and the model of dependence of each burden deviation from the designed one on the intensity of blasting vibrations was established under laboratory conditions. To verify the model, the same experiments were also applied in the field. The basic parameter of the model, the coefficient K, which represents the ratio of peak particle velocity and the surfaces of the blasted material from laboratory and field testing, indicates that there is a connection between these values. The deviation of the coefficient K, obtained from laboratory and field measurements, was 5.5%.
In the name of a better and safer energy future, it is our responsibility to focus our knowledge and activities to save on imported liquid and gas fossil fuels, as well as coal on which energy ...security of Serbia is based. The rationalization in the use of available energy resources certainly positively affects economy and the environment of a country. This paper indicates motivations for the application of the underground coal gasification process, as well as surface gasification for Serbia. The goal is to burn less coal, while simultaneously utilizing more gas from the onsite underground coal gasification, or by gasification in various types of gas generators mounted on the surface. In both cases, from the obtained gas, CO2, NOx, and other harmful gases are extracted in scrubbers. This means that further gas combustion byproducts do not pollute the atmosphere in comparison with traditional coal combustion. In addition, complete underground coal gasification power requirements could be offset by the onsite solar photovoltaic power plant, which furthermore enhances environmental concerns of the overall coal utilization.
In the course of court trials and for the purpose of legal proceedings, forensic engineers often produce estimations of the explosive mass based on the explosion effect using empirical formulas. This ...paper describes experimental surface explosions of variable mass of known explosive charge on the asphalt with the objective to make correlations between causes and consequences of an explosion. Dimensions of the resulting craters were measured and an overview of experimental tests and reliability of nine equations for calculating the mass of explosive based on the dimensions of the craters is given. The asphalt surfaces were chosen since the highest number of explosions, which are the results of terrorist or some other criminal acts, occur in urban conditions where asphalt is the dominant surface. Based on the given overview it is possible to give an evaluation of equation's reliability for explosive mass less than 1kg. The paper also gives the proposition of the new equations for preliminary estimation of explosive charge mass based on volume of the crater resulting from the surface explosion on asphalt.Original Abstract: U tijeku sudenja, a za potrebe sudskih postupaka, forenzicki inzenjeri cesto proizvode procjene ksplozivne mase na temelju ucinka eksplozije pomocu empirijskih formula. Ovaj clanak opisuje eksperimentalne povrsinske eksplozije na asfaltu sa promjenjivom masom poznatog eksplozivnog naboja s ciljem uspostavljanja korelacije izmedu uzroka i posljedica eksplozije. Dimenzije proizislih kratera su mjerene i dan je pregled eksperimentalnih ispitivanja i pouzdanost devet jednadzbi za izracunavanje mase eksploziva na temelju dimenzije kratera. Obzirom da se najveci broj eksplozija, koje su posljedica teroristickih ili nekih drugih kaznenih djela, dogadja u urbanim uvjetima gdje je asfalt dominantna povrsina izabran je asfalt za ispitivanje. Na temelju danog pregleda je moguce dati procjenu pouzdanosti jednadzbi za eksplozivne naboje manje od 1 kg. Rad takoder daje prijedlog novih jednadzbi za preliminarne procjene mase eksplozivnog punjenja na temelju volumena kratera kao posljedice eksplozije na povrsini asfalta.
Underground mine projects are often associated with diverse sources of uncertainties. Having the ability to plan for these uncertainties plays a key role in the process of project evaluation and is ...increasingly recognized as critical to mining project success. To make the best decision, based on the information available, it is necessary to develop an adequate model incorporating the uncertainty of the input parameters. The model is developed on the basis of full discounted cash flow analysis of an underground zinc mine project. The relationships between input variables and economic outcomes are complex and often nonlinear. Fuzzy-interval grey system theory is used to forecast zinc metal prices while geometric Brownian motion is used to forecast operating costs over the time frame of the project. To quantify the uncertainty in the parameters within a project, such as capital investment, ore grade, mill recovery, metal content of concentrate, and discount rate, we have applied the concept of interval numbers. The final decision related to project acceptance is based on the net present value of the cash flows generated by the simulation over the time project horizon.
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