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|Title:||Tünel kazılarında oluşan solunabilir tozun etüdü|
|Other Titles:||Respirable Dust Generation İn Tünnel Excavetions|
|Publisher:||Fen Bilimleri Enstitüsü|
Institute of Science and Technology
|Abstract:||Bu tez "Tünel Kazalarında Oluşan Sağlığa Zararlı (Solunabilir) Tozun Etüdü" ile ilgili bir çalışmadır. Tez kapsamında, istanbul Büyükşehir Belediyesi İstanbul Metrosu Tünel Kazılarının yapıldığı Taksim, Şişli ve Zincirlikuyu Şantiyeleri ile TKİ. Orta Anadolu Linyitleri İşletmesi 4207 Nolu Baca Kazısı Sırasında, Casella 113 A tipi toz örnekleyici ile ölçümler yapılarak toz yoğunlukları tespit edilmiş ve daha sonra bu toz örnekleri İstanbul Üniversitesi, Jeoloji Mühendisliği Bölümü, Petrografi Anabilim Dalında X- Ray Cihazı ile analiz edilerek kuvars içerikleri araştırılmıştır. Bu ölçüm ve analizler vasıtasıyla kazı işyerlerinin tozluluk durumu belirlenmiş ve standartlara uygunluğu araştırılmıştır. Ayıca şimdiye kadar yapılan araştırmalarla tespit edilmiş olan, tozun oluşum nedenleri ve oluşan tozun ortam havasına dağılmasına yol açan faktörlere ait teoriler de yapılan ölçüm ve gözlemler sayesinde bu kaza işyerlerinde incelenmiştir. Çalışmanın sonucunda İstanbul Metrosu Taksim Şantiyesi ile Şişli Şantiyesinin bir bölümünde ve T.K.İ. Orta Anadolu Linyitleri İşletmesi 4207 Nolu Baca kazısında oldukça yüksek toz yoğunlukları tespit edilmiştir. Söz konusu toz yoğunluklarına, özellikle havalandırmanın yetersiz olmasının ve tozu bastırmada su kullanımına önem verilmemesinin yol açtığı anlaşılmıştır. Bu iki faktör optimum olarak yerine getirilmediği taktirde toz yoğunluğu artmaktadır. Diğer önemli bir faktör ise kazalan kayacın özellikleridir. Araştırma sırasında kayaç sertliği arttıkça toz oluşumunun da arttığı gözlenmiştir. Ayrıca kaza işinin mekanize olarak (kollu galeri açma makinası gibi) yapılmasının da toz oluşumunun artmasına neden olduğu anlaşılmıştır.|
This theisis is a study related with respirable dust generated during the excavation works in tunnels. Healtf and safety of the workers and working place is inevatebly important matter for the sake of achieving required standarts and high productivity. Among these requirements, the dust is especially important in excavation works. In this study, the dust concentrations were measured by utilizing the Gravimetrik Dust Sampler in which type of MRE Casella 1 13 A. Samples taken were analyzed and investigate the occurrence of quartz on X-Ray equipment. As a result of these measurements and analyses, the dust level of excavation working places was determined to achieve the required health and safety standarts. Furthermore, the theories at this area were used to validate with experimental data. The term "dust" is applied to suspensions of finely divided solid matter in the air. Instabilitiy, coagulation and precipitation are their special characreristics. Dust includes a wide range of particle sizes of from over 1 mm to under 1 um. (one thousandth of a milimeter). The size of particles considerably influences their behavior. Dust particles are usually divided into three classes. 1. Particles greater than 10 um, which settle according to the laws of gravity, i.e., with increasing velocity in still air 2. Particles between 0. 1 to 10 um, which in still air settle at a constant velocity which can be calculated by Stoke's law (the uniform settling velocity depends on particle size and density, viscosity of the medium, and acceleration due to gravity). 3. Particles between 0.01 and 0.1 um, which do not settle but diffuse in the air and remain in a colloidal state. A dust cloud consisting of particles 5 um. in size is not visible to the naked eye. It cloud not be seen in the strongest beam of light underground, but would appear as motes in a beam of sunlight. Dusts can be classified according to their harmful physiological effects. In the section 1 the lists different types of dusts in order of decreasing harm in each category. To adequately control particulate matter in the mine atmosphere, the following basic principles of behavior must be understood. 1. Particulate matter, whether liquid or solid, exhibits remarkably similar behavior when airborne. The following discussion pertains to the properties and control of solid contaminants, since they are by far the more prevalent in mine air, but the same principles apply to liquid contaminants. XI 2. Dust particles either pathological or combustible consequence are predominantly below 10 urn. in size (10 um = 0.0004 in.). Those below 5 um are classfied by mine health authorities as respirable dust. 3. Particles larger than 10 um. are unlikely u remain long in suspension in airstreams unless high velocities are encountered. These particles, however are not of primary concern. 4. Industrial and mine dusts characteristically have a mean particle size in the range of 0.5 to 3 um. 5. Chemical activity increases with decreasing particle size. 6. The dust below 10 um. in size, which are of serious consequence in air hygiene, have no significant weight or inertia and hence can remain suspended indefinitely in an atmosphere. The expectation that such dusts will "settle out" of the airstream is wishful thinking. 7. The control of fine dusts (below 10 um.) that have become airborne requires control of the airstream in which they are suspended. This is the basic concept of dust control. Güyagüler (1991), has investigated to form of dust, which is referred to this study in terms of a dust-producing index, can be quantitatively related to mechanical and physical rock characteristics. Fine particles of dust constitute both a health hazard and a nuisance in mines. Thus far, the main methods of dust control used in mines have focused on reducing the amount of dust alrady in the air. Recently, however, attention has turned to avoiding dust generation at source. Determining to what extent rock properties influence dust production would, therefore, be helpful. The investigations of Güyagüler demonsrated that the influence of various factors on dust fomation shows variation under different conditions. From regression analysis for individual factors it was concluded that the brittleness : toughness ratio and the hardness of a rock are the inherent properties that most significantly influence the dust-producing index. Hardness shows the highest positive correlation coeffient with the index, the ratio of brittleness to toughness being the most influential factor . Dust is generated and dispersed into the mine air through rock breakage, rock loading, transportation and unloading, and through the flow of ventilating air. Dust is produced in all rock-breaking processes. The quantity of potantially airborne dust produced is related to the quantity rock broken. Rock-cutting processes are performd by percussion and rotary drills, tunnel-boring machines, and continuous miners. These machines break rock through a complex process of impact and fracture. Primarily there are two phases involved cutting the chip and removing it from the rock face. In the cutting process the production of potentially airborne dust is inversely related to size of the rock chips. In order to reduce the formation of such dust, the intensity of the cutting force should be as high as possible and should be applied to a small area with a greater depth of cut. The design of cutting tools to xn achieve this is complex. The minimum spesific energy consumption in rock breaking and the minumum spesific dust generation are usually achieved simultaneously. The chip-removal process in drilling can generate airborne dust. Insufficient clearance or not enough flushing can produce further breakage of chips, decreaesde cutting speed and energy loss in the drill rod with increased spesific dust generation. The handling of the broken rock has a significant effect on the dipersion of the fine dust in the mine air. Although all fine dust, potentially airborne dust cloud be dispersed by repeated handling in an airstream, generally this occurs to only a portion of it. The quantity of dust dispersed in the handling process is determined by :. The amount of fine dust created in the breaking process. The extent to which the material is disturbed in handlign. The energy expended to create new breakage. The kinetic energy imparted to the freshly broken rock particles by the stress relief in the material bnken. Ambient air velocities The following üst is demonsrated that the effects of different operations and factors in mining on dust production; 1. Cutung-Drilling-Blastmg : In this process the stress applied must exceed the ultimate stress, whether confined under pressure as in solid blasting, or open-face cutting. Under confined comditions the stress may rougly be equal to hardness. So the production of dust will depend purely on brittleness and the volume of rock affected. Sharpness of tools means less area to be brought to the failure point, which may result in less dust. Coal plough thus have an advantage over cutter-loaders in this respect. In these processes higher rank coals like anthracites may even give rise to more dust in spite of high hardness. 2. Loading-Unloading : Here the production of dust depends mainly on the height of all. If the height of all is not sufficient to bring the material to crushing point no dust will be formed even with highly brittle substanceslike antracite. Coaking coals are worst affected in this process. In such a case uniaxial strength under dynamic condition is the breaking stress and not the hardness, as the materials are not confined. 3. Crushing-Screening-Preparation : These processes are similar to cutting or drilling excepting the fact that the material is not confined and as such the pressure required for crushing is comprehensive strength at a quick rate of loading. As the material will be necessarily brought to the crushing point, the fundamental force behind the production of dust is the brittleness. XIII 4. Mining Method-Support Roof Pressure : Due to roof pressure the coal seam may be brought to the crushing stress. The same may be induced locally due to improper mining method and support. Production of dust, therefore, in such a case will depend on brittleness. The effects of other factors in mining may be summarized as follows; Depth : With increase in depth confining pressure increases and as a result the material becomes less brittle. Similar effect is visible as a result of higher temperature at greater depths, as brittleness of a substance decreases with increases in temperature. For this reason inherent dustability characteristic may decrease with depth. But on the other hand crushing may take place due to pressure at a greater depth. Dry or Wet Mines : In dry conditions dispersibility is higher, wet conditions have coagulating effects. Ventilation : High velocity of air causes more dispersion of dust in the air. Fight Against Dust : Water or chemical infusion reduces the formation of dust and dispersal into the mine atmosphere. The mining system, the context in which it is discussed, and dust sources being described must be defined to relate equipment design to the need for dust control. There are two major elements of the mining system that must be differantiated : The"cutting system," which is defined as the bit-mineral interface where fragmentation by the cutting tool or bit occurs, and the balance of the mining system, with all other activities directly supporting the cutting system. The phrase "directly supporting the cutting system" is intentionally used. This is an extremely important distinction to remember because, although the cutting tool is one of the cheapest and most expendable items in the mine, it is the only item in the mine producing a salable product. In addition, correct or incorret use of the cutting tool will affect all minerals in the face area, the mining machine, the preparation plant, and the final percentage of salable product recovered from the mine. During product recovery the cutting tool forced into the coal face creates dust by compressive fractures and tensile failure to recover a salable product. Major factors affecting this product recovery include coal characteristics, bit geometry, and bit usage (the way the tool is mounted on and used by the continuous mining machine, CMM). The following list is summarazied of primary dust control techniques with rotary drum cutting. This list presents options currently available for control ling primary dust generation.. Use lowest possible included tip angle on the bit.. Use only sharp bits to maintain maximum sump rate.. Use spacing of two to three times two-thirds the depth of cut.. Use only enough gage cutters on the end ring to be effective. XIV . Change head gearing to reduce drum rpm.. Increase advance rate (sump rate).. Operators should always crowd machine to just below the stall point. In summary, cut at maximum depth (maximum sumping or advance rate) at all times, at minumum rpm, with the fewest possible bits, that have the lowest possible included tip angle. If this fails, redesign the supporting equipment to use a constant depth linear cutting system. Any dust, if present in excessive quantities and inhaled for a sufficiently long time, can cause physiological damage. Factors determine the harnfulness of any dust are its composition, particle size, concentratino in mine air, exposure time, and susceptibility of the exposed individual. These factors are examined in Section 3. Pneumonconiosis can be defined as the accumulation of dust in the lungs and the reaction of lung tissue to the presence of that dust. Coal workers' pneumonconiosis is caused by inhalation and retention of coal mine dust. Silica (SİO2 ) dust causes the lung disease known as silicosis. Centuries before the Christian era, Hippocrates wrote of a lung disease common to those who mined in hard rock. He was obviously discussing silicosis. Other ancient writings indicate the Egyptians were aware of this malady. Silicosis among hardrock miners was certainly described by Agricola in his De Re Metallica published in 1956. The medical community in Europe and the U.S. recognized the silica health hazard in the early 1900s. They were concernd about the health hazard of sandblasting in polishin shops, the efficiency of exhaust systems, and the necessity to protect the sandblasters again the dust hazard. Sandblasting, hardrock mining, and drilling are equally hazardous occupations. Winslow, a professor of public health at Yale School of Medicine, recommended in 1919 a dust level below 21 mg/m3 of air and the use of a positive pressure helmet an respirator. The U.S. Department of Labor described the need for personal respiratory protection in 1939 : "prevention of silicosis consists of preventing silica dust from getting into the air that workers breathe." In 1966 the American Conference of Government Industrial Hygienists (ACGIH) made a recommendation on allowable silica levels in the work place atmosphere. In 1972 Cralled reported that "silicosis remains a serious occupational disease throughout the world." The ACGIH establishes TLV-TWA (threshold limit values/time-weighted average) values for dusts which are for illustration purposes only, since the current standarts of ACGIH as reported in then- annual publications may change. The dust standarts of different countries illustrate the variety of ways in which dust concentration may be measured. Some of these atandarts are listed in Section 5. Three main categories of instnimuents are used in underground mines to measure concentration of respirable dust in mine atmosphere. These are (1) gravimetrin dust samplers, (2) short-term dust monitors, and (3) instruments for particle-size measurements. As the name implies, gravimetric sampling is carried out for the assessment of dust concentrations by mass. Gravimetric sampling consists basically of two steps : first, the collection of a representative portion of the dust from the air, and XV second, the assessment of the collected material by determination of its mass and analysis by X-Ray diffractions or chemical means. In this investigation, MRE Gravimetric Dust Sampler Was used during the measurements. The technique of the measurements device and working principlies was described in Section 6. The samples of accumulated dust was analyzed by X-Ray diffractometer. It has shown that the dust samples does not contain any quartz contents. It was observed that the dust threshold value is higher than the standart values in Şişli- Taksim field of work and the Middle Anatolia Lignits Enterprise. These high value dust was occured owing to the insufficient ventilation and lake of water sprays. The other important factor is the properties of broken rocks. During this research, it was observed that if the hardness of rock increases, the production of dust increases too. In addition to these, mechanized excavation causes increament on the dust generation.
|Description:||Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 1995|
Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 1995
|Appears in Collections:||Maden Mühendisliği Lisansüstü Programı - Yüksek Lisans|
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