Assessment of effects of geological and geotechnical factors on coal burst proneness

A rockburst is an energy release phenomenon which occurs by the interaction of multiple factors in complex geological and geotechnical conditions. Rockbursts have been recognised as one of the most catastrophic hazards experienced in underground mines and tunnels. In coal mining terminology, coal burst refers specifically to a burst event that expels coal into a mine opening. Despite the widespread and long-lasting experience of bursts, their underlying mechanisms are still not fully understood. The ultimate aim of this thesis was to improve the understanding of the fundamental coal burst mechanisms and assist mine operators to evaluate coal burst proneness in their mines. Firstly, a semi-quantitative classification system has been proposed in this study to assess coal burst proneness in underground coal mines. Moreover, an energy-based quantitative burst proneness rating system specifically designed for development roadways has also been introduced. Several burst and no-burst cases from Australia, China and the United Sates were back-analysed using the developed systems. Furthermore, numerical analyses have been conducted to examine the effects of geological structures on burst proneness near roadways. The model outcomes were then compared to benchmark cases to assess relative proneness of varying mining environments. The studies quantified the impacts of geological faults and dykes on energy release and storage mechanisms; and showed that unfavourably positioned geological structures can increase coal burst proneness in roadways. In addition, the effects of pre-existing discontinuities on coal mass strength and energy release characteristics have been investigated. It was found that higher cleat density can notably reduce energy release magnitudes and rates in a coal mass. To sum up, along with several other factors, mining depth, geological structures and coal mass conditions have been shown to play an important role in elevation of risk of coal burst occurrence. The outcomes of this thesis have demonstrated the complexity of coal bursts and highlighted the importance of a multifactorial approach in evaluating of coal burst risks in mines. The results of the parametric analyses and proposed risk-based methodologies provide an improved understanding of coal burst mechanisms and guidance for effective management of coal burst risk in underground coal mines

Technical and economic evaluation of energy production from wind in Istanbul and surrounds

Istanbul is located in the northwest part of Turkey and has the greatest population of any city in the country. Istanbul and its surroundings were researched for wind potential. Energy production from wind was evaluated technically and economically in this study. Çorlu, Kumköy and Şile sites were examined. Other sites in the same region (Göztepe, Kireçburnu, Bahçeköy, Florya and Kartal) were also evaluated but the results were not satisfactory, and for this reason, these sites were not examined in this study. When we checked daily, monthly and yearly wind speed values and frequency distributions, the wind energy potential of Çorlu, Kumköy and Şile were greater than other sites. Çorlu, Kumköy and especially Şile’s wind speed data are statistically decreasing. A Nordex N117 91m hub height wind turbine can produce 6099 MWh in Çorlu, 6459 MWh in Şile, 7265 MWh in Kumköy. A Nordex N117 140 m hub height wind turbine can produce 6471 MWh in Çorlu, 7439 MWh in Şile and 8175 MWh in Kumköy. The energy costs were calculated by the average of 36 years of wind measurement data using Nordex N117 turbines. Energy costs with Nordex N117 91 m and 140 m hub height in Çorlu, Şile and Kumköy are 0.025-0,027 US$/KWh, 0.022-0,025 US$/KWh, 0.020-0,023 US$/KWh, respectively

Design combined support under arbitrary impulsive loading

Rock bolts and cable bolts are usually considered to experience static loads under relatively low-stress conditions. However, in burst-prone conditions, support elements are subjected to dynamic loading. Therefore, it is important to understand cable bolt behaviour under dynamic loading conditions, particularly their energy absorption capacity. Rock bolts and cable bolts as well as steel mesh are widely used as permanent support elements in tunnelling, underground excavations and surface slope stability. This paper aims to determine the amount of the dissipated energy which can be taken into account to design combined yielding supports when subjected to dynamic loading. A ground support approach is suggested for underground excavations undertaking a range of mining-induced coal burst. A bench mark based on the largest expected impact loading is considered to conclude the level of coal burst risk and select an appropriate approach, whether quasi-static or dynamic, for the mine support

Numerically and Analytically Forecasting the Coal Burst Using Energy Based Approach Methods

Coal burst is referred to as the violent failure of overstressed coal, which has been recognised as one of the most critical dynamic failures in coal mines. This chapter aims to analytically and numerically evaluate the energy transformation between the different strata and coal layers. An accurate closed-form solution is developed. Due to the complexity of the causes and mechanisms contributing to the coal burst occurrence, 3D finite element modelling as well as discrete element models will be developed to validate the suggested analytical assessments of rock/coal burst occurrence. The energy concept is emphasised in order to improve the understanding of the underlying mechanisms of coal burst. Only with enhanced understanding of the driving mechanisms, a reliable coal burst risk assessment can be achieved

Numerical analysis of strain energy density at development and longwall face

Strain energy stored within coal mass is one of the main energy sources of coal bursts. Damage caused by a coal burst event can be attributed to the magnitude of strain energy accumulated around excavations. In this study, strain energy density (SED) within coal seam is examined around excavation boundaries during development and longwall retreat. Several numerical models are generated to investigate SED distributions for mining depths ranging between 100 m and 1000 m. For both development and longwall retreat, the maximum SED area migrated deeper into excavation boundaries with increasing mining depth. When the mining depth increased from 100 m to 1000 m, the maximum SED around development increased from approximately 6 kJ/m3 to 780 kJ/m3, while the maximum SED at longwall face increased from approximately 102 kJ/m3 to 1710 kJ/m3. The maximum SED around roadway ribs was lower than that at longwall face at the same mining depth. The sensitivity analyses presented in this study can provide guidance to geotechnical engineers to better understand and evaluate associated risks for different mining conditions

A Power Case Study for Monocrystalline and Polycrystalline Solar Panels in Bursa City, Turkey

It was intended to reveal the time dependent power generation under different loads for two different solar panels under the conditions of Bursa province in between August 19 and 25, 2014. The testing sets include solar panels, inverter, multimeter, accumulator, regulator, pyranometer, pyrheliometer, temperature sensor, and datalogger. The efficiency of monocrystalline and polycrystalline solar panels was calculated depending on the climatic data’s measurements. As the result of the study, the average performances of monocrystalline and polycrystalline panels are 42.06 and 39.80 Wh, respectively. It was seen that 87.14 W instantaneous power could be obtained from monocrystalline solar panel and that 80.17 W instantaneous power could be obtained from polycrystalline solar panel under maximum total radiation (1001.13 W/m2). Within this frame, it was determined that monocrystalline solar panel is able to operate more efficiently under the conditions of Bursa compared to polycrystalline solar panel. When the multivariate correlations coefficients were examined statistically, a significant relationship in positive direction was detected between total and direct radiation and ambient temperature on energy generation from monocrystalline and polycrystalline panel

Analysis on Photovoltaic Energy-Assisted Drying of Green Peas

A photovoltaic energy-assisted industrial dryer has been analyzed. The dryer has been tested in various weather and working conditions with 3 kg of green peas from 75.6% initial moisture content to 20% final moisture content (w.b.). The effect of various drying air temperatures at three levels (40, 50, and 60°C) and two distinct air velocities (3 m/s and 4 m/s) was examined. Drying performance was assessed with regard to criteria including drying kinetics, specific and total energy consumption, and color and rehydration ratio. The results have proved that total drying duration reduces as air velocity rate and drying air temperature raise. Relying upon the drying durations, the generation performances of photovoltaic panels were between 5.261 and 3.953 W. On the other part, energy consumptions of dryer were between 37.417 and 28.111 W. The best specific energy consumption was detected in 50°C at 3 m/s for 600 minutes with 7.616 kWh/kg. All drying conditions caused darkening as color parameters. Rehydration assays have showed that rehydrated green peas attained higher capacity with raised air temperature and air velocity

A New Concept to Numerically Evaluate the Performance of Yielding Support under Impulsive Loading

The dynamic capacity of a support system is dependent on the connectivity and compatibility of its reinforcement and surface support elements. Connectivity refers to the capacity of a system to transfer the dynamic load from an element to another, for example, from the reinforcement to the surface support through plates and terminating arrangements (split set rings, nuts, etc.), or from a reinforcement/holding element to others via the surface support. Compatibility is related to the difference in stiffness amongst support elements. Load transfer may not take place appropriately when there are strong stiffness contrasts within a ground support system. Case studies revealed premature failures of stiffer elements prior to utilising the full capacity of more deformable elements within the same system. From a design perspective, it is important to understand that the dynamic-load capacity of a ground support system depends not only on the capacity of its reinforcement elements but also, and perhaps most importantly, on their compatibility with other elements of the system and on the strength of the connections. The failure of one component of the support system usually leads to the failure of the system

Procena troškova kombinovanja sakupljanja kišnice sa solarnom irigacijom

Water availability is becoming acute in all over the world. Increased water demands have generated interest in different systems. Rainwater harvesting is one of the promising way to meet water demand for agricultural irrigation. However, water transmission between water resources and the field requires energy. There are several ways for powering irrigation systems. One of the options is to use solar panels as an alternate energy source, and it is mainly use in where there is no electricity. This study represents the analysis of combined rainwater harvesting with monocrystalline or polycrystalline or amorphous silicon solar power based irrigation systems. The study found for all solar powered irrigation cost huge because of primary investment. Nevertheless, the need for fossil fuel can be decreased by using solar panels and proposed solution for the present energy crisis for the farmers.Dostupnost vode postaje otežana širom sveta. Povećane potrebe za vodom povećale su interesovanje za različitim sistemima. Sakupljanje kišnice je jedan od načina koji obećavaju zadovoljenje potreba za vodom za navodnjavanje u poljoprivredi. Prenos vode od izvora do parcela zahteva energiju. Postoji nekoliko načina za pogon sistema za navodnjavanje. Jedna od opcija je upotreba solarnih panela kao alternativnog izvora energije koji se koristi tamo gde nema električne energije. Ovaj rad predstavlja analizu sakupljanja kišnice sa navodnjavanje sa monokristalnim, polikristalnim ili amorfnosilikonskim solarnim pogonom sistema za navodnjavanje. Rezultati su pokazali da su za svako navodnjavanje sa solarnim pogonom bili veliki troškovi zbog velikih primarnih ulaganja. Ipak, potrošnja fosilnih goriva može da bude smanjena upotrebom solarnih panela i ovo može da bude rešenje za sadašnju energetsku krizu

A Power Case Study for Monocrystalline and Polycrystalline Solar Panels in Bursa City, Turkey

It was intended to reveal the time dependent power generation under different loads for two different solar panels under the conditions of Bursa province in between August 19 and 25, 2014. The testing sets include solar panels, inverter, multimeter, accumulator, regulator, pyranometer, pyrheliometer, temperature sensor, and datalogger. The efficiency of monocrystalline and polycrystalline solar panels was calculated depending on the climatic data's measurements. As the result of the study, the average performances of monocrystalline and polycrystalline panels are 42.06 and 39.80 Wh, respectively. It was seen that 87.14 W instantaneous power could be obtained from monocrystalline solar panel and that 80.17 W instantaneous power could be obtained from polycrystalline solar panel under maximum total radiation (1001.13 W/m 2 ). Within this frame, it was determined that monocrystalline solar panel is able to operate more efficiently under the conditions of Bursa compared to polycrystalline solar panel. When the multivariate correlations coefficients were examined statistically, a significant relationship in positive direction was detected between total and direct radiation and ambient temperature on energy generation from monocrystalline and polycrystalline panel