Tail Gate Research Articles

High Drilling Methane Drainage in Fracturing Zones Formed by Water Injection into Boreholes

AbstractMethane drainage method should be used before coal mining of many modern collieries because venti lation air methane is in sufficient to keep methane level within regulation values. The technology of high drilling methane drainage (HDMD) has been used for methane drainage although its effect is not very stable due to parameter design. The height of the fracturing zones is determined mostly according to empirical formula, on-site observation and numerical simulation analysis. In this paper, a method was introduced for determining the height of the air f ract uring zones (AFZs) based on its high similarity to the characteristics of Fracturing zones and the relationship between the height of Fracturing zones and the strain of overl ying rock strata. The application of water injection in both Shuangdingshan and Dongrong collieries found that the theoretically calculated the height of the Fracturing zones was approximately equal to the measured one in field tests within a permissible error of less than 5%, proving that the method is feasible. Based on the designed drainage parameters, the u tilization of HDMD technology in the collieries mentioned above found that the methane concentrations in both tail gate and upper corner were controlled in the ranges of 0.17% to 0.32% and 0.26% to 0.84%, respectively. These results showed that the water injection verified HDMD in Fracturing zones could effectively solve the problem of metha ne overrun and also verified the accuracy and reliability of its related theory.

EXTENSION OF EXCAVATION DAMAGED ZONE DUE TO LONGWALL WORKING EFFECT

In advance longwall mining, the safety of mine network, production rate, and consequently, economic conditions of a mine are dependent on the stability conditions of gate roadways. The gate roadway stability is a function of two important factors: 1) characteristics of the excavation damaged zone (EDZ) above the gate roadway and 2) loading effect due to the caving zone (CZ) above the longwall working, which can extend the EDZ size. Generally, due to the coal seam dip, the failure possibility of main gate roadway is more severe than tail gate roadway. The aim of this work is to determine the longwall working effect on the EDZ extension above main gate roadway. To achieve this purpose, considering three factors involved in the CZ characteristics, the coal seam properties (dip and thickness) and the geomechanical properties of hangingwall, a new geometrical model is developed. Then, based on the geometrical calculations, a new relationship is presented to determine the working influence coeffiecint. Furthermore, taking into account the new geometrical model, an algorithm is suggested for the stability analysis of main gate roadways. Validation of the new geometrical model is carried out by the instrumentation and monitoring results of a longwall working carried out in the Parvade-2 coal mine of Tabas, Tabas, Iran. The results obtained show that there is a good agreement between the values obtained by the new model and the actual measured values. Finally, a sensitivity analysis is carried out on the effects of pillar width, bearing capacity of support system, and coal seam dip.

Fundamental understanding of goaf gas displacement in longwall goaf

Fundamental understanding of the goaf gas distribution in a gassy coal mine is necessary for developing effective goaf gas drainage strategies in the longwall coal mine. The goaf gas was subjected to the surface and body forces that were classified depending upon whether they acted on the surface area or the volume of the gas element. Of these forces, the body forces were more predominant in displacing the goaf gas present in the underground mine. The buoyancy forces were classified as the body forces; they are the predominant forces acting on the goaf gas. The buoyancy forces depend mainly upon the density variation in the gas species and the panel orientation or panel geometry. If the temperature variations are neglected, the buoyancy forces that cause the displacement of the goaf gas depend mainly upon the panel orientation. In this work, numerical investigations were carried out using the computational fluid dynamics (CFD) techniques for the fundamental understanding of the goaf gas displacement for various panel orientations. The numerical results obtained for various panel orientations indicated that the goaf gas is displaced towards the tailgate (TG) side when the maingate (MG) was downdip, towards the MG side when MG was updip, towards the start-up of the panel when the face was downdip, and towards the face when the face was updip.

CFD Modeling of Methane Gas Distribution and Control Strategies in a Gassy Coal Mine

High methane (CH4) gas emission from the goaf in a gassy coal mine diffuses the gas into the face that leads to hazardous working environment and create operational difficulties. Electrical equipment which are loaded with sensors get tripped off when CH4 level is greater than 2%. Oxygen (O2) ingresses more on the maingate (MG) side than the tailgate (TG) side of the goaf due to high ventilation air pressure and hence no major gas issues are dealt on this side of the goaf. However, when the air flows along the face, air pressure decreases and less O2 ingress on TG side of goaf and more CH4 gas diffuse into the face in these regions. CH4 gas diffusion not only disrupts the functioning of electrical equipment but also creates hazardous environment for the operator. In this paper, an attempt was made to understand the CH4 gas distribution at the TG for gas emission rate of 1000l/s respectively and investigate the control options available for diluting the gas concentrations in the TG region. From Computational Fluid Dynamics (CFD) investigations, it was concluded that for gas emission rates over 1000l/s the CH4 concentration level at the TG region was above 2% and demand for control measures. Gas control strategies with goaf drainage, back return ventilation system and curtains across the face in the TG region were investigated using CFD techniques. From numerical investigations, it can be concluded that gas control strategy with goaf drainage was able to reduce the CH4 level to below 1% and back return system at the TG side was able to completely eliminate gas traces. Placing a curtain assisted in shifting the gas fringes into the goaf and thereby reducing the gas concentrations to below 1%.

Reducing and Optimizing Tailgate Closing Effort in Automotive Car

This Project investigated the scope of automotive tailgate closure closing effort and optimization. Tailgate closing effort can be reduced with the aid of car body dimensional analysis and corrections. Dimensional analysis mainly deals about dimensional position of car body, seal gap at rear tailgate closure, margin and flushness between tail lamp and tailgate, bumper and tailgate, roof and tail gate. Dimensional position investigates car body and sub assembly manufacturing controls to ensure dimensional repeatability by using fixture integrity concepts, and incoming level supplier part dimensional variations. Fixture integrity concepts mainly focus to bring the car body towards nominal of its dimensional position. Seal gap at rear tailgate closure is a gap between weather strips mounting at framed body flange to tailgate resting surface. More seal gap gives less closing effort, more wind noise and less seal gap gives more closing effort, less wind noise. Margin and flushness between outer peripheral supports wind noise. Closures closing effort, Wind noise and air leak is integrated parameters in automotive car body.

Three-Dimensional Numerical Simulation of the Mass Exchange Between Longwall Headings and Goafs, in the Presence of Methane Drainage in A U-Type Ventilated Longwall / Symulacja Numeryczna 3D Procesów Wymiany Masy W Układzie Wyrobiska Ścianowe Zroby, W Aspekcie Prowadzenia Odmetanowania Ściany Przewietrzanej Systemem Na „U”

Abstract The phenomena related to the occurrence of methane in underground mines pose a considerable danger in the process of coal seam exploitation. Quite often, experimental analysis falls short of investigating their areas of origin (goafs area, affected rock mass, the tail gate area with abandoned excavation). Therefore, an invaluable tool for evaluating the risk involved in the exploitation process might be the numerical simulation of the phenomenon in question, carried out with the use of the latest CFD methods. Due to its application, we are able to recreate and predict the mechanism of the studied phenomenon, with certain assumptions and simplifications made. The present paper discusses the results of the numerical simulation of the process of mass exchange occurring between affected rock mass and longwall headings. The calculations were performed for two test cases - 100 meter long walls.

Effect of longwall face advance rate on spontaneous heating process in the gob area – CFD modelling

A commercial CFD software programme, FLUENT, was used to study the oxidation process of coal in the mined-out longwall (gob) area. A three-dimensional, single-phasemodel with a continuously advancing longwall face has been developed. For the model, the gob longwall area was designed on the basis of the actual longwall panel operating in the Ostrava-Karviná Coal Mines (OKD, Czech Republic). The behaviour of the coal to oxygen was modelled using the results arising mainly from the former laboratory-scale experiments with Czech bituminous coals. Basically, the technique of pulse flow calorimetry and measurements at a continuous airflow reactor were applied during the laboratory investigations. In the contribution, the main focus was to understand the effect of the longwall face advancing speed on the oxidation heat production as well as evolution of the gases in the gob area. Simultaneously, the effect of coal crushing in the mined-out area on the spontaneous heating process was examined.Numerical simulations confirmed the existence of a “favourable” zone for the onset and development of the spontaneous heating process in the gob area. The location and the maximal temperature reached in the “favourable” zone were found to be significantly affected by the advancing rate of the coalface. The slower the advancing rate is, the higher the maximal temperature and smaller the depth of the “favourable” zone in the gob area are. When the rate drops to a certain “critical” value, spontaneous heating turns to flammable combustion of the coal. The value of the “critical” advancing rate was confirmed to increase if the grain size of the coal left in the gob decreases. Numerical examinations of carbon monoxide concentrations then proved that small incidents of spontaneous heating could occur in the gob area that need not be detected in the airflow of the longwall tail gate.

Sound damping and sealing system for tail gate

A sound damping system for a swinging tail gate of a dump truck is described. The system comprises a two-part seal formed by a compressible sound damping material and a rigid compressing projection. One part of the two-part seal is secured along opposed vertical edges of opposed side walls of an open-top-end box of the truck. The other part is secured on opposed sides of an inner wall of the tail gate and aligned for facial contact with the first part. The tail gate is hingedly secured at a top end thereof to the opposed side walls of the box. The sound damping system also provides a more efficient sealing system between the gate when in a closed position with the box of the truck.

The ventilation and climate modelling of rapid development tunnel drivages

Abstract The extraction of minerals and coal at greater depth, employing higher-powered machinery to increase production levels has imposed an increased burden on ventilation systems to maintain an acceptable working environment. A deterioration in the climate experienced within these workings may also adversely affect the health and safety of the workforce. In the UK, mineral extraction is now being practiced at depths of over 1000 m. In addition, the adoption of continuous miner and tunnel bolting support methods has permitted improved development rates to be achieved at the cost of increased emissions of dust, gas and heat and humidity. There is a recognized need to improve the efficiency in the design and operation of auxiliary ventilation systems to maintain an adequate underground environment and climate. Any improvement achieved in the quality, quantity and control of the delivered ventilation will assist in the provision of improved gas and dust dilution and climatic control. Due to the constraints imposed by the mining method, there may be an economic or practical limit to the climatic improvement that may be obtained by the sole use of ventilation air. Where this limit is identified, there may be the need to consider the selective application of air-cooling systems. The paper details the construction of a computer based climatic prediction tool developed at the University of Nottingham. This work builds upon earlier research (Ross et al., 1997, Proceedings of 6th International Mine Ventilation Congress, SME, Littleton, CO, pp. 283–288) that developed a prototype model for short tunnel developments. The current model predicts the psychrometric and thermodynamic conditions within long rapid development single entry tunnel drivages. The model takes into account the mass and heat transfer between the strata, water, machinery and the ventilation air. The results produced by the model have been correlated against ventilation, climatic and operational data, obtained from a number of rapid tunnel developments within UK deep coalmines. The paper details the results of a series of correlation and validation studies conducted against the ventilation and climate survey data measured within 105s district Tail Gate tunnel development at Maltby Colliery, UK. The paper concludes by presenting the results of a case study that illustrate the application of the validated model to the design and operation of an integrated mine ventilation and cooling system. The case study illustrates the effect that an increased depth and hence increased virgin strata temperature has on the climate experienced within rapid tunnel developments. Further investigations were performed to identify the optimum cooling strategy that should be adopted to maintain a satisfactory climate at the head of the drivage.

On establishing uniform channel flow with tail gate

On establishing uniform channel flow with tail gate

On establishing uniform channel flow with tail gate

Steady uniform flow is a basic reference condition for hydraulic analyses of water surface profiles, resistance, velocity and pressure distributions, and channel geometry effects for open-channel flows. In laboratory experiments uniform flow is often generated by adjusting tail and entrance gates such that the flow depth remains constant along the channel. This note shows that the constant depth criterion is necessary, but insufficient, to obtain a true uniform flow for which cross-sectional flow velocity and stress distributions should also remain unchanged for a short reach around the measurement section.

On establishing uniform channel flow with tail gate

Steady uniform flow is a basic reference condition for hydraulic analyses of water surface profiles, resistance, velocity and pressure distributions, and channel geometry effects for open-channel flows. In laboratory experiments uniform flow is often generated by adjusting tail and entrance gates such that the flow depth remains constant along the channel. This note shows that the constant depth criterion is necessary, but insufficient, to obtain a true uniform flow for which cross-sectional flow velocity and stress distributions should also remain unchanged for a short reach around the measurement section.

Buy Skinny, Sell Fat

FICTION Buy Skinny, Sell Fat Ralph Price HECK DROVE UP to the junkyard on Pope's Nose Hill looking for a used rear end. His was going out. He felt it on the curves. The junk man pulled one from a faded aqua fifty-five. Greasy Red wanted forty bucks—too much—but threw in the set of livestock racks that were moldering on the junker. They were almost a fit for his Dodge short bed, and they looked good, too, except that there was no tail gate. He found a piece ofhalf-inchplywood for the gate, and placed the plywood facing inward. The plywood was a road sign stolen from the county road and bridge crew, and bore the warning, DANGER UP AHEAD. Then Heck put the Hi-Lift jack, the jumper cables, two quarts of Dollar Store oil, and a pint of coffee on the crowded seat beside him, and he drove over to Richmond to get into the pig business. There was a big sale there because of the rain the night before. Too wet to work in the fields—Let's go sell the one-eyed boar—Get us a bottle. E. R. Yakes was there at the sale, and he took Heck over to number seven to see a skinny black sow Yakes's brother-in-law had brought in. She was skinny, yes—but not sick. Yakes knew that for a fact. Heck bought the sow and her five pigs for sixty-five dollars and hauled them home without changing a tire. He took his Colt .32 revolver out of the glove box and shot a pig for dinner. The others went into a recently-repaired slab and metal hog pen, where they settled in with much sniffing and shuffling of straw. The pigs grew like the grass. They gained weight faster than seemed possible. Heck found them each morning a new size, and each day worth more than the day before. But the sow was a worrier. She fretted. Some days she'd hardly get out of bed. She had a dark side, that was sure, and often she'd escape. Then Heck would have to track her down in some farmer's back yard, pin her up in the hen house or the coal shed, load her backwards into the truck, and haul her brooding home, back to her squealing young. He'd soon had enough of that, and so off she went to the sausage man. The sausage man lived in a dark alley lined in weeds and runt sunflowers and covered with flattened cans. He offered to buy the sow, fatten her up. It would be a shame, the butcher said, to kill the 49 sow so small. Heck asked him what he would give. Sixty-five dollars, he said. No, Heck told him. He'd rather have the meat. The four pigs grew into lovely fat hogs with white hair and pink bellies. They ate everything but grapefruit and jimson weed, quarreled over the egg shells, and never got enough. About that time the price of pork went through the roof. Nobody saw it coming, but coming it came, and then everybody said they weren't surprised. Heck cashed in for the quick profits. As he said to C. T, he was in it, by God, for the money. Well, the money rolled in, and each time he sold, he bought. Soon he had pigs and hogs of all sizes and colors. He spent many cold mornings hauling corn to the mill to be ground and mixed with bean meal. He sat on a wooden bench at the mill while his corn was being ground, and he read magazines with titles like Pork Producer Monthly or Stockman's Digest. July and hot as inside the cow. Bugs flew out of control, heavy as stones. Birds awake at midnight. Lightning. Wild Roses. Heck's favorite sow was due. Her tits were hard as oranges, and there was milk when you squeezed the nipples. She'd thrown together a cockeyed nest a little before dark, then torn it up again. She didn't eat, but took a little water. The lightning...

A Survey of Transport for Children in Wheelchairs

This article is the result of an investigation carried out during 1988/1989 into the way in which local education authorities transport children in wheelchairs to and from school. It covers areas such as the number of children with special needs transported on a daily basis, the ownership of the vehicles used to transport them, the use of tail gate lift vehicles and the details of any accidents that had happened during the previous 5 years. There did seem to be a wide variation across the country in the suitability of transport provided for the children. In general, Northern Ireland and the metropolitan areas of England provided more appropriate transport.

採掘跡ライナー坑道枠の変形計測

Support deformation of gate roadway was monitored at four longwall panels of Kushiro Colliery in order to determine the design criteria for construction of the liner road which had been newly developed instead of advancing tail gate. The mining depth of those panels was 660m below the sea level, and the mining geometries of them were almost similar to each other. All the liner roads were constructed within 7m from ribside and used for return air ways.The measurement revealed that there was little deformation- of support within 20m behind coal face, but after that the deformation increased with advance of the coal face as shown in Figs. 4, 8, 11 and 15, which was approximated by a piece-wise linear curve with respect to distance from the coal face, Fig. 17. Also the support deformation varied periodically along the liner road as shown in Fig. 5, 9, 12, and 16 so that the predominant wavelength was, for instance, 71, 33 and 14m in a typical panel. The upper half arc of the circular ring support or the arch member of the arch-invert support was not only lowered, but also deformed toward the ribside of the panel, Figs. 6 and 13. Furthermore the uplift of floor was profited by level surveying along the liner road.The results obtained from measurement, therefore, imply that the support deformation of the liner road may scarecely be affected by caving of the immediate roof just after advance of powered support, but may be dominated by main roof lowering and floor heave accompanied by face advance.

太平洋炭砿におけるライナー坑道を用いた採炭

The main mining system at Kushiro Colliery is the longwall mining system with shield supports and drum shearer. On the occasion of this mining, generally main gate road, tail gate road and face road must be driven by means of continuous miner before mining. However, with the increase of mining depth, successive maintenance of gate roads has been confronted with difficulties.Accordingly, for the purpose of solving this problem, liner road system was investigated and adopted to the longwall mining system. In the liner road system, at the beginning main gate road and face road are driven, and tail gate road is constructed in goaf with advance of face.From September 1979 to February 1983 this liner road system has been adopted to 17 mining panels. Total distance of liner road was 7, 644 m and total coal productions amounted 2, 168, 010 tons (clean coal).In the future longwall mining plan, the proportion of liner road system will increase. Furthermore, in order to increase the recovery and reduce the cost, the new technical and economical improvement of liner road system is examined and the first step has put into practice