Dissertations / Theses on the topic 'Pond ash'

The Latrobe Valley mines, Victoria, Australia, are facing some major challenges as they approach the end of their mining life. Most of these challenges surround current rehabilitation practice and the ability to create safe and stable landforms for future land uses well after the mines have closed. As there has been no developed alternative use for the brown coal at this stage, stopping power generation leads to the cessation of mining. AGL Loy Yang is undertaking rehabilitation cover trials on exposed coal batters to investigate optimal cover materials that will enable safe and stable batters well beyond mine closure. A series of rehabilitation trials using coarse coal ash have been constructed by AGL to assess the performance of coarse coal ash as a ‘subsurface drainage layer’. One of the trials includes the use of a 1 metre coarse coal ash layer placed below a 1 metre thick clay cover and above a coal surface shaped to approximately 18 degrees (1V:3H). Without a drainage layer, water may percolate through the clay cover or seep through the intact brown coal, resulting in a build of pore water pressure at the coal – clay interface and increasing the potential for slope failure. The aim of this research work was to assess the spatial distribution of ash properties known to affect drainage behaviour at the field scale; to test and calibrate field-monitoring equipment that can be used to assess drainage behaviour at the field-scale; to provide recommendations for further research on the use of coal ash drainage layer; and to provide a benchmark for future testing and monitoring. Through an experimental investigation, it was shown that there no significant variation exists in the coarse fraction of Loy Yang pond ash’s physical and chemical properties. Monitoring equipment used to determine the field drainage performance of the ash included a T8 Tensiometer and EnviroPro (multi-capacitance sensor) that were calibrated and tested in the laboratory. It was determined that monitoring devices used in this study were suitable for measuring the ash’s hydraulic behaviour only once calibrations had been performed. As a result the tested field equipment were included in the design of a future monitoring program.
Masters by Research

This research studies the performance of a salinity gradient solar pond driving an absorption cooling system, as an alternative to a conventional electrically powered cooling system, to provide cool air for a modern single family house in the hot dry climate of Baghdad, Iraq. The system comprises a salinity gradient solar pond, a hot-water-fired absorption water chiller, a chilled-water cooling coil which cools the air in the house, and a cooling tower which rejects heat to the ambient air. Hot brine from the pond circulates through a heat exchanger, where it heats water that is then pumped to the chiller. This arrangement protects the chiller from the corrosive brine. The system is controlled on-off by a room thermostat in the house. The system performance is modelled by dynamic thermal simulation using TMY2 hourly typical weather data. TRNSYS software is used for the main simulation, coupled to a MATLAB model of heat and mass transfer in the pond and the ground beneath it. The model of the pond and the ground is one-dimensional (only vertical transfers are considered). Radiation, convection, conduction, evaporation and diffusion are considered; the ground water at some depth below the pond is treated as being at a fixed temperature. All input data and parameter values in the simulation are based on published, standard or manufacturer's data. Temperature profiles in the pond were calculated and found to be in good agreement with published experimental results. It was found that a pond area of approximately 400 m2 was required to provide satisfactory cooling for a non-insulated house of approximately 125 m2 floor area. It was found that varying the pond area, ground conditions and pond layer thicknesses affected the system performance. The optimum site is one that has soil with low thermal conductivity, low moisture content and a deep water table. It is concluded that Iraq's climate has a potential for solar-pond-powered thermal cooling systems. It is feasible to use a solar-pond-powered cooling system to meet the space cooling load for a single family house in the summer season. Improving the thermal performance of the house by insulation could reduce the required solar pond area.

This study is based on compaction characteristics of Fly ash and pond ash. In thermal power plants, there are three kinds of ash formed named as (a) pond ash, (b) fly ash, and (c) bottom ash. Fly ash is one of the products of coal combustion, consisting of the fine particles that are determined out of the boiler with the flue gasses. The ash falls to the bottom of the boiler is called bottom ashes. In existing coal plants, generally,fly ash is captured by electrostatic precipitators and other clarified particles equipment before reaching the chimney. Pond ash is the by-product of thermoelectric power plants, which is recognized by means of an unused material and disposal is an important environmental issue and also needs a lot of removal regions. Several factors influence the dry density of Fly ash and Pond ash such as specific gravity, moisture content, compaction energy, layer thickness and mold area. The difference of the OMC and MDD of Fly Ash (collected from NTPC kanhia, Odisha) according to the standard proctor compaction energy is 0.90 – 1.59 gm/cc and 18 - 27%, respectively. This difference of the OMC and MDD of Pond ash as per standard proctor compaction energy at the level of 0.856 – 1.248 gm/cc and 33 - 46%, respectively. The study was that variation in these factors influencing the dry density of fly ash and ash pond significantly and to determine the Geotechnical properties of pond ash and fly ash.

Backfilling enables complete or around ninety percent extraction of coal from the seam and then filling the mine voids with mill tailings; sand or excavated stones etc. which provides additional ground support by constraining lateral deformation of surrounding coal pillars and roof. However the overall feasibility of the backfill operation with different materials has to be studied in detail. The objective of this project is to evaluate the suitability of using pond-ash as backfill material over fly ash and sand in respect to shrinkage of the stowed area. The shrinkage study is done with the help of numerical modeling in FLAC of a mine KTK-5 where pond-ash stowing is going to be implemented. The physical properties like bulk modulus, shear modulus, cohesion, friction angle etc. were also found out through experiments which are required during the numerical modeling. Moreover an effort has also been made to develop comprehensive flow model using CFD and then use the model for predicting pressure drop, volume fraction etc. A 20m pipe with diameter of 20cm is modeled, through which flow is conducted where modeling and meshing is done using ANSYS Fluent. High viscosity fly and pond ash slurry with different concentrations up to 70% by weight of pond ash is passed and for each concentration different velocities are used and pressure drops is calculated. MDD ranges from 1.07gm/cc to 1.27gm/cc. With increase in compaction energy MDD increases due to the closer packing of pond ash particles and OMC decreases from 38% to 28% approx. which might be due to the increase in moisture content leading to less friction between the particles and promoting compact packing with increase in compaction which in turn decreases voids and increase saturation limit. The settling rate for the sample is found to be around 30% with water-liquid (phase1) and pond-ash (phase2). Velocity of 3.5m/s of the paste are optimum with respect to pressure drop. The FLAC simulation yields factor of safety (FOS) after excavation of one pillar with no fill to be 1.5 whereas with pond ash fill it is 2.7. Similarly FOS after stowing with pond ash in the voids of two pillars was found to be 2.5 whereas without fill it was 1.2. After excavation of two and half pillars FOS was calculated to be 1.9 with pond ash fill and 1.0 without fill.

Vitality necessities for the creating nations like India specifically are met from coal based thermal power plants, where 75% of the aggregate force acquired is from coal-based thermal power plants. The coal used for power generation contains 30–40% of ash. The fly ash generation is more because of high ash coal. The fourth position acquired by the India on the world in the generation of coal ash as waste by-product after USSR, USA and China, in a specific order. Pond ash is the by-product of thermal power plants, which is a waste material and its disposal is a most important problem from an environmental point of view and also it needs a lot of disposal area. Acquiring open lands for disposal in creating nations. For example, India is troublesome, where the area to-population proportion is little. The area and population proportion is less so the area necessity and the expense of the area are expanding step by step, it is key to recover or enhance these ash beds so that the area could be used for the development of light and moderate common foundations. The slack ash fill structures may be susceptible to to collapse on wetting. So a research is carried out to observe the factors affecting the collapse of compacted ash fill on flood. If the ash beds intend to be used as footing subgrades to support civil infrastructure so we need to know its collapsibility behaviour. In the current work, importance has been given on the factors that affecting the collapse settlement of the compacted coal ash due to moistening. For this experimental study is taken up to known the collapsible potential of Pond ash. Attempts have been made to correlate the ash characteristics and the specific placement parameters such as dry unit weight, moisture content, and compaction energy and stress level at wetting with collapse. This was based largely on the single oedometer collapse test results. A sequences of tests, like, direct shear test, light compaction and in addition substantial compaction test are performed to evaluate the quality attributes of compacted pond ash and also tests like specific gravity test, grain size distribution test by mechanical sieve analysis and hydrometer test etc. are performed to get more or less physical properties of the pond ash. Total 145 single oedometer collapse tests were conducted to get the collapse potential of pond ash. The results of oedometer test were very much helpful for evaluating the factors affecting the collapse potential of pond ash.

Now, more than 100 million tons of coal fly ash is produced annually in India from combustion of coal in power plants. It is expected that about 150 million tons of coal ash will be produced due to burning of coal in power plants by the year of 2015. This will require about 30,000 hectare of land for the disposal of ash. One of the biggest problems due to disposal of large quantities of coal ash is the possible leaching of different hazardous pollutants, including fluoride. A thorough investigating concerning leaching of fluoride from fly ash is much more indispensable to know the impingement of fluoride due to its leaching from fly ash to ground water as well as surface water. In this paper, short term and long term leaching studies will be carried out on pond ash, pond ash water of different thermal power plants: Rourkela Steel Plant (RSP), Rourkela; National Thermal Power Corporation (NTPC), Kaniha; National Aluminium Corporation Limited (NALCO), Angul; IB Thermal Power Station (ITPS), Banharpali. The amount of fluoride released in different experiments will be evaluated. Environmental impact of pond ash and fluoride has been discussed.

In the recent past huge amount of Fly ash and Pond ash are generated by the thermal power plants. It is a major cause of concern for the people living around the power plants. The current rate of deposition of Pond ash in India has reached 170 million tons per annum. About 90,000 acres of precious land is used for the storage of abandoned Pond ash. But current rate of utilization of ash is only about 35-40%.The unused ash leads to an ever increasing ponding area for storing ash and related environmental issues for the people around the power plants. Besides this, over the last few years, the construction of highways and roads has taken a boost. This requires a huge amount of natural soil and aggregates to excavated or to be deposited. Again this is an environmental issue and economical too. These are some issues now-a-days which motivates in development of alternative methods to overcome those environmental and also the economic issues. This leads to the reuse of suitable industrial byproducts which can fix those issues and also fulfill the specifications. Pond ash is one such byproduct. It is a non-plastic and lightweight material. During this work, the effect of moisture content, degree of compaction, synthetic fiber as a reinforcement etc. on various geotechnical properties of pond ash are studied. A series of tests such as direct shear test, CBR test, light compaction as well as heavy compaction test, Unconfined compression test are done to estimate the strength characteristics of compacted pond ash using synthetic fiber as a reinforcement as well as tests like specific gravity test, grain size distribution test by mechanical sieve analysis and hydrometer test etc. are performed to obtain some physical properties of the pond ash.These results will be very much helpful for the successful application of pond ash in different fields such as embankment construction, road base and sub-base construction, designing of retaining walls etc. as well as the disposal of pond ash in an ecofriendly manner.

The development of any country depends on increasing the industries and agriculture, which is governed by adequate power supply. In India major source of power generation is by coal based thermal power plants. Present day’s coal based thermal power industries are increasing day by day. Coal available in India is low grade coal with ash content of 30-45% in comparison to imported coal which has low ash content of 10-15%. In India, total 145 coal based thermal power plants are existed by the year of 2014-2015. Thermal power plants are major sources of ash generation. Typically these plants are produces two types of ash materials: Fly ash and Bottom ash. These two types of ash are mixed thoroughly with large quantities of water and sluiced to onsite storage ponds called ash ponds. Massive utilization of pond ash in engineering field requires thorough understanding of its geotechnical properties, especially strength characteristics. In the present study, a detailed experimental investigation was carried out on the strength and other geotechnical properties of pond ash samples mixed with different bentonite content. The main focus of the study was to evaluate the engineering properties of pond ash-bentonite mixes and assessing its suitability in various geotechnical constructions mainly the land fill liner. The Pond ash and bentonite samples are characterized and analyzed for the various geotechnical properties. The various experimental works were carried out to determine the index and engineering properties of pond ash with and without bentonite content. Index properties such as density index, plastic limit, liquid limit and engineering properties such as compaction and consolidation characteristics, shear strength were found by conducting various experiments accordingly. All the experiments were conducted by adding bentonite ranging from 5 to 30% at 5% interval to the pond ash and results were compiled in the graphical form to observe the trends in various parameters.

With the increase in the number of coal based thermal power plants in India, generation of coal ash has reached enormous proportions. India at present produces around 120 Million tonnes of Ash per annum. The power requirements of the country are rapidly increasing with increase in growth of the industrial sectors. India depends on Thermal power as its main source (around 80% of power produced is thermal power), as a result the quantity of Ash produced shall also increase. Indian coal on an average has 35 % Ash and this is one of the prime factors which shall lead to increased ash production and hence, Ash utilization problems for the country. Out of the total ash produced. Fly ash contributes to a small percentage, majority being Pond ash and bottom ash. Ash disposal involves design and installation of ash ponds, which in addition to covering quite large area at each plant site, creates aesthetic as well as hygienic environmental impacts. This has warranted the scientific and industrial community to initiate research and development work for finding avenues for the innovative use and safe disposal of the pond ash so that instead of a waste product, the pond ash could be considered as a usable by-product. Though a lot of research has been carried out for the effective utilization of pond ash like its use in construction industry etc, little literature is available on pond ash utilization particularly its use as a foundation material. One way of disposing off pond ash would be its use as a structural fill material and use as embankment material in highways. The present work aims at evaluating the response of pond ash to various compactive efforts. The compactive efforts have been varied as 595 kj/m3 to 2674 kj/m3 of sample and effect of compaction energy on MDD and OMC have been evaluated by conducting proctor compaction tests, the shear strength parameters of pond ash samples compacted to different dry densities and moisture contents. Based on experimental findings the following conclusions are drawn.  Increase in compaction energy facilitates closer packing of pond ash particles resulting in an increase in MDD  MDD of compacted samples shows a linear relationship with the amount of compaction energy.  The OMC of the samples is found to decrease with increase in compactive effort increased compaction energy forces the particles to come closer resulting in a reduced void space hence OMC is found to be 28%-39%.  It is shown in results,With increase in compaction energy from 3639 to 35554 kg-cm, MDD of pond ash increases, but at the same time OMC decreases.  shear strength tests on freshly compacted pond ash specimens at various water contents and different dry densities show that most of the shear strength is due to internal friction.  Angle of friction doesn’t change much when we applied different compactive efforts  With increase of compaction energy from 595 kj/m3 to 2674 kj/m3 per 1000 cc of compacted sample the MDD is found to change from 1.09 gm/cc and 1.27 gm/cc

At present about 130 million tonnes of ash is being produced annually from the coal based thermal power plants in India. The power requirements of the country are rapidly increasing in pace with in industrial developments. Nearly, 73% of India’s total installed power generation capacity is thermal of which coal based generation are nearly 90% (by diesel, wind, gas and steam adding about 10%). Indian coal gives 35 to 45% ash which is responsible for large volumes of pond ash. Construction of large ash disposal areas results in resettlement issues and loss of agricultural production, grazing land and habitat as well as other hand use impacts from diversion of large areas of land to waste disposal. The current practice in most of the power plants is to use large ash ponds, and nearly 75,000 acres of land is presently occupied by ash ponds sometimes in excess of 80,000 acres, which usually involves resettlement issues. Since, land holdings are typically small in size; a large ash pond development can cause hardships through loss of land-based subsistence and livelihood for literally thousands of people. Considering these factors, effective utilization of pond ash in geo-technical constructions as a replacement to conventional earth materials needs special attention. The inherent strength of the compacted pond ash mass reduces considerably due to saturation. In this context to improve and retain the strength of compacted pond ash, cementing agents like cement or lime may be very much beneficial. The stress-strain behavior of compacted pond ash mass can be modified by inclusion of fibre reinforcements. Fibre reinforcements also improve the strength characteristics of the mass. Although, the use of reinforced earth materials has been widely accepted in many areas like embankments, foundations medium, railroads, retaining walls but the utilization of pond ash in place of earth material has not drawn much attention of researchers. The present work aims at evaluating the geo-engineering properties of compacted pond ash and also the effectiveness of fibre inclusions in the strength characteristics of compacted pond ash specimens through a series of shear test, unconfined compression test and CBR test. For this purpose, a polyester fibre (Recron-3s) of 6mm and 12mm in length size is used with the pond ash, collected from Rourkela Steel Plant (RSP). The fibre content was varied as 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.75, and 1.0% of the dry weight of pond ash. The effect of fibre reinforcement on compacted density has been studies using the light and heavy compaction test. Compressive strength and shear strength behaviour of compacted samples were studied using unconfined compressive strength test and direct shear test respectively. The suitability of compacted pond ash fibre mixes as a road base and sub-base material have been studied by conducting laboratory CBR tests. The results have been interpreted in terms of stress-strain behavior, variation of failure stress, variation of failure strain, effect of degree of saturation, effect of fibre content, strength ratio, and secant modulus and strength parameters and are presented in this thesis. Based on the experimental findings the following conclusions are drawn:  The pond ash consists of grains mostly of fine sand to silt size with uniform gradation of particles. The specific gravity of particles is lower than that of the conventional earth materials.  An increase in compaction energy results in closer packing of particles resulting in an increase in dry density where as the optimum moisture content decreases.  Dry unit weight of compacted specimens is found to change from 10.90 to 12.70kN/m3 with change in compaction energy from 357 to 3488kJ/m3, whereas the OMC is found to decrease from 38.82 to 28.09%.  Both the unit cohesion and angle of internal friction increase with increase in compaction energy. A nonlinear relation between these parameters is found to exist with compaction energy.  For unreinforced compacted pond ash specimens, the value of unit cohesion increases with degree of saturation up to the OMC and thereafter the same decreases. The highest value of unit cohesion occurs at OMC for samples compacted both at standard and modified densities. However, there is a continuous decrease of angle of internal friction value with degree of saturation. Initially there is a sharp decrease which gets stabilized at moisture contents higher than OMC.  The unit undrained cohesion of reinforced specimens is found to increase with the fibre content. However, the rate of increase of unit undrained cohesion with fibre content is not linear. Initially the rate of increase is high thereafter the increase in unit cohesion is not that prominent.  For a given compacted density and fibre content, the 12mm size fibre gives higher strength than 6mm size fibres.  The highest value of unconfined compressive strength is found to be 12kPa and 29kPa at a degree of saturation of 13% and 14 % for samples compacted at standard and modified proctor density. Moisture content either higher or lower than the said value results in decrease in the compressive strength.  The failure stresses as well as initial stiffness of unreinforced samples, compacted with greater compaction energies, are higher than the samples compacted with lower compaction energy. However the failure strains are found to be lower for samples compacted with higher energies. The failure strains vary from a value of 0.75 to 1.75%, indicating brittle failures in the specimens.  An almost linear relationship is found to exist between the compaction energy and unconfined compressive strength.  The UCS value of unreinforced specimens is found to change from 1.2 to 17.0kPa with change in compaction energy from 357 to 3488kJ/m3 indicating that the strength can be modified suitably by changing the compactive effort. It revealed from the test results that a linear relationship exists between the initial tangent modulus with unconfined compressive strength and deformation modulus.  The trend observed in the CBR value with moisture content is very much similar to that observe with unconfined compressive strength value of specimens. This shows that for a given compacted dry density higher unconfined compressive strength as well as CBR value can be obtained with moulding water content much lower than the OMC value.  At low strain levels the bearing resistance is found to remain almost constant with fibre content. However at higher strain level the bearing resistance is found to increases substantially with increase in fibre content. It is observed that for a given compacted density an increase in fibre content results in decrease of initial stiffness whereas the failure strain increases.  The inclusion of fibre gives ductility to the specimens. The reduction in post peak stress of a reinforced sample is comparatively lower than the unreinforced sample. The strength parameters achieved in the present study is comparable to the good quality, similar graded conventional earth materials. Hence, it can be safely concluded that reinforced pond ash can replace the natural earth materials in geo-technical constructions.

experimental study is taken up to improve the strength of compacted pond ash. This has been achieved in two series of tests. In the first series of test the compacted pond ash beds are reinforced with either PVC net or GI nets. The size of the reinforcement as well as the position of the reinforcement was varied. The CBR value of these specimens we are found out and these are compared with that of and unreinforced pond ash bed compacted to MDD at OMC. In the second series of the tests the CBR value of river sand compacted to different relative densities and different moisture contents are evaluated. In general the CBR value of compacted sand at different moisture content are found to be higher than compacted pond ash. To find out the CBR values of compacted pond ash beds overlain by a layer of sand with different relative densities and moisture contents. The optimum thickness of sand beds has been found out such that effect of underlain pond ash beds is minimal on the CBR value based on these experimental results it is concluded that in filed the bearing capacity of ash beds can be improve either by reinforcing it with suitable gird reinforcing materials are by overlaying it with suitable thickness of stiffer material such that the effect of under laid Pond ash material is not felt.

Energy requirements for the developing countries like India in particular are met from coal-based thermal power plants. The ash generation has increased to about 131 million tonne during 2010-11and shall continue to grow. Huge amount of coal ash generation creates major problems for their disposal. Primarily, the coal ash is disposed off using either dry or wet disposal scheme. In wet disposal, the fly ash and bottom ash are transported as slurry through pipe and disposed off in pond ash. Main reason for failure of ash dyke is due to ineffective functioning of filter or internal drains. Natural river sand is used as the conventional filter material. However, the non-availability of required graded sand in and around construction site and in all seasons possesses problems to the construction of ash dykes. Coarse pond ash and bottom ash which are the waste products of thermal power plant and non-plastic in nature and available abundantly in thermal power plants may replace the conventional sand as a filtering material. In this present work coal ashes like bottom ash and course pond ash collected from NTPC, Kaniha. Coarse sand was collected from Brahmini River whereas fly ash was collected from RSP, Rourkela. Then for all the samples physical property, index properties, and geotechnical properties like grain size distribution, dry density, coefficient of permeability, crushing strength, strength parameters have been found out when samples were subjected to both dynamic and static compaction and also model test has been done to find out the filtering capabilities of these materials. It is found that coarse pond ash, bottom ash and sand used in the present study before and after meets the filter criteria as per Indian standard of practice.

In the recent past large amount of Pond ash are generated by the thermal power plants. It is a major reason of concern for the people living around the power plants. Statistical observation shows that the current rate of deposition of Pond ash in India has reached 170 million tons/annum. About 90,000 acres of precious cultivable land is used for the storage of abandoned ash. But the current rate of utilization of ash is only about 35-40%.The unused ash leads to an increasing ponding area for storing of ash and related environmental problems for the people who live around the power plants. Besides this, over the last few years, due to development the construction of skyscrapers, highways and roads has taken a boost. This requires a large amount of natural soil and aggregates to excavated or to be deposited. Hence this is a both environmental and economic issue. These are some issues now-a-days which motivates in development of alternative methods to overcome those environmental and also the economic issues which leads to the reuse of suitable industrial waste products which can fix those issues and also fulfill the specifications. During this work, the effect of moisture content, degree of compaction, dry densities etc. on various geotechnical properties of pond ash are studied. Specific gravity test, grain size distribution test by mechanical sieve analysis etc. are performed to obtain some physical properties of the pond ash. A series of tests such as light compaction as well as heavy compaction test, Direct shear test, Footing load test are done to estimate the strength characteristics of suitably compacted pond ash. The footing load test of saturated pond ash sample over lain by some thickness of sand bed is done and increase in the strength of pond ash is observed. These results will be very much helpful for the successful application of pond ash in different fields as well as the disposal of pond ash in an ecofriendly manner.

Rapid urbanization and growth in population are key reasons for a massive increase in generation of solid wastes. This is becoming a major environmental concern. Landfilling is an extensively accepted practice for disposal of solid wastes. Conventionally, clay is used as a landfill liner due to its cost-effectiveness, high stability, and self-healing ability. The lack of suitable clay at a site often triggers the use of bentonite based materials as a substitute to since it is highly colloidal in nature with expanding lattice structure having high adsorption capacity and low hydraulic conductivity. However, compacted clays with higher bentonitic contents undergo extensive changes in properties when exposed to freeze-thaw or shrink-swell cycling. The problems associated with higher volume change and developments of cracks are found to be minimized by the addition of a substantial amount of non-swelling coarser fraction. Typically, soil-bentonite, sand-bentonite, zeolite-bentonite, etc. are used as an alternative liner material for waste disposal facilities. However, the scarcity of natural soil encourages the use of alternate materials as landfill liners. In this context, the present research work focuses on assessing the suitability of pond ash-bentonite (PAB) mixture as an alternative to sand-bentonite (SB) mixture for liner material. As the coarse fraction of pond ash resembles natural sand in terms of gradation with higher interlocking and frictional properties, there is a potential for utilization of the coarser fraction of pond ash as a substitute to sand. The performance of the PAB mixtures is accessed by examining their physicochemical and hydro-mechanical properties. The physicochemical properties considered comprised of gradation, particle shape parameters, consistency limits, free swell index and cation exchange capacity, and the hydro-mechanical properties considered include unconfined compressive strength, shear strength parameters, hydraulic conductivity, compressibility and volumetric shrinkage characteristics. A comparative assessment is made between SB and PAB mixtures for a range of bentonite content varying from 0 to 30% by weight at an interval of 5% to ensure an effective substitution of sand with pond ash. The optimized bentonite contents are determined by examining the relevant properties of compacted PAB and SB mixtures as per the USEPA (1988) regulatory for liner material. Influential parameters such as clay content, molding water content, fibre content, and chemical environment on strength, durability, hydraulic and microstructural characteristics of PAB and SB mixtures have also been investigated. The experimental results reveal that the addition of bentonite to sand or pond ash significantly influences the plasticity, strength, compressibility, permeability, and volumetric shrinkage properties. At comparable conditions, compacted PAB mixtures exhibit higher unconfined viii compressive strength (UCS), cohesion, frictional angle, hydraulic conductivity, and lower volumetric shrinkage than SB mixtures. Both PAB and SB mixtures met the liner requirements as per USEPA (1988) regulatory when compacted with modified Proctor energy at a minimum bentonite content of 20% and 15% respectively. Compression index (Cc) of the mixtures is found to maintain a linear relationship with liquid limit. Empirical equations have been developed to estimate the Cc and hydraulic conductivity of bentonite-based liner material from the basic parameters of the mixtures which have been compared and validated with existing corelations and experimental datasets. The compressive strength, failure strain, unit cohesion, and frictional angle of the compacted specimens are found to increase whereas the volumetric shrinkage strains are decreased with an increase in fibre content irrespective of the molding water content. With an addition of 1% Recron-3S polypropylene fibre, the UCS values are found to increase by 2 to 3 times as compared to those of unreinforced specimen. Both unreinforced and reinforced specimens exhibit the maximum UCS value at relative water content of 90% and 80% when compacted to standard and modified Proctor density respectively. Reinforced specimens compacted at dry of optimum did not show any significant variation in hydraulic conductivity whereas specimens compacted at wet of optimum exhibit an increased value of hydraulic conductivity with fibre content. The increase in volumetric shrinkage strain with relative water content is reduced as the fibre content increases. Furthermore, alternate freeze-thaw cycles are found to have a significant influence on volume, moisture content, unit weight, UCS, and hydraulic conductivity of the compacted mixtures. The changes in these properties are found to be stabilized after 10 freeze-thaw cycles. The rate of increment in hydraulic conductivity and reduction in compressive strength of compacted SB mixes are higher than those of compacted PAB mixes. Specimens compacted at dry of optimum exhibit lower reduction in compressive strength than those compacted at wet of optimum. In contrast, specimens compacted at dry of optimum show lower increment in hydraulic conductivity than those compacted at wet of optimum. The study on the effects of chemical environment on the engineering properties of PAB and SB mixtures reveals that the consistency limits, free swell indices, and volumetric shrinkage strain are reduced whereas the hydraulic conductivity increased as the concentration of salt solutions and their permeation time is increased. The UCS values are found to increase with the permeation of lower concentration of salt solutions and the same reduces substantially with further increase of concentration. Salt solutions of polyvalent cations are found to have more impact than those of monovalent cations. PAB specimens are less vulnerable to these changes as compared to those of SB specimens. The sorption concentrations of permeating cations are found to increase substantially in the liner materials with an increase of salt concentration and their permeation time, whereas the concentrations of inherently adsorbed elements decreased. The observed variations in the said ix properties associated with the influential parameters are correlated to the shape of coarse fraction particle and the corresponding microstructural arrangements of the compacted specimens. Although, PAB mixtures experience marginally higher hydraulic conductivity than those of SB mixtures, the mixtures possess higher CEC, improved strength and lower volumetric shrinkage strain at a particular bentonite content and compactive effort. Further the engineering properties of PAB mixtures are less susceptible to adverse environmental conditions than SB mixtures. The use of pond ash as a coarse fractioned element in bentonite-based liner material will provide a greater avenue for its utilization as well as the preservation of the natural resources

碩士
國立中興大學
土木工程學系所
101
As electronic, wireless communication network, and software technology progresses, continually, people have been integrating these technologies into the development of Unmanned Surface Vehicle (USV) and as a result, creating USVs with different functionalities and forms for applications in the areas of military and science. USV has very convenient features. This study attempts to integrate these technologies into a self-made USV which can be used for measurement purposes, or more specifically, for the application of ash pond capacity measurement and hopefully finding a new alternative or assistance for traditional measurement operation through this new technology. The test result had shown that measurement accuracy and capacity calculation had all met the regulatory requirements when USV or traditional measurement operation was applied. As for comparisons of operating cost, labor, and time, USV still proved to be more advantageous than traditional measurement operation. Hence for the ash pond capacity measurement, USV is a viable alternative or assistance for traditional measurement operation.

One of the major challenges before the processing and manufacturing industries is disposal of the residual waste products. Pond ash and red mud are one of the major waste products of any aluminum industry. The pond ash and red mud sample are acquired form BALCO, Korba where they are disposed off using the Thick Slurry Disposal System, which enables quick consolidation of the slurry once disposed at the ash and red mud pond sites. The project work focuses on the suitability of pond ash and red mud obtained hereby to be used for construction of embankment. The ash and red mud samples are characterized and analyzed for the various geotechnical properties. The various experimental works include in situ density test using core cutter method, Standard Proctor density test to obtain the maximum dry density and optimum moisture content, and specific gravity test. Using the OMC and MDD results, Direct Shear Box test and Triaxial tests of the samples were carried out in 2-D and 3-D load conditions to obtain the shear strength parameters, c and Ф. The samples were also tested for their permeability characteristics using both falling head and constant head permeameter to obtain the coefficient of permeability, κ. After characterization of the ash and red mud samples for their individual geotechnical parameters, the samples were mixed in various proportions to get a mix having optimum characteristics. The samples were mixed in the proportions of 90%-10%, 80%-20%, 70%-30%, 60%-40%, 50%-50% of red mud and ash content respectively. All the above experiments were carried out on each mix to obtain an optimum mix. The results of the experiments are all compiled in graphical form to observe the trends in the various parameters. Out of the all, the optimum mix is found out taking into account the considerations for construction of an embankment. To account for the experimental findings, the samples were also observed under SEM (Scanning Electron Microscope). The magnified photographs of the particles, their arrangements and the mineralogical constitution are observed under the SEM and analyzed to validate the geotechnical parameters found from experimental procedures. From the analysis of the mineralogical data, presence of some toxic elements is observed. The above analysis and results can help in solving the problem of ash and red mud disposal and to a great extent help in increasing the economic benefit of the alumina industries.

Pond ash produced as a by-product of the coal based thermal plants whose disposal is often a major environmental and economic issue. Reinforced earth wall is preferred over conventional RCC rigid retaining wall as it is not only cost effective but also has better performances during earthquake. But it uses the natural resources sand as the fill material. In this work, a possible use of pond ash and its mixture with sand as a fill material for reinforced earth wall is investigated. The major issue about the use of pond as a fill material is the development of shear resistance or pull out capacity. In this work the shear behaviour of pond ash, sand and its mixture is studied. A polymeric reinforcement is considered and the friction between the polymeric reinforcement and the pond ash mixture is studied using a laboratory pull out test. Experiments have been conducted on a model of the pond ash mix with reinforcement. The results have been compared with the simulation using a finite element based commercial software, PLAXIS 2D.

Pond ash deposits possess high compressibility, low bearing capacity so acres of land get wasted. Improvement of load carrying capacity of ash ponds will make them suitable for residential or commercial use. Stone or compacted stone columns is a technique of soil reinforcement that is frequently implemented in soft cohesive soils to increase the bearing capacity of the foundation soil, to reduce the settlement, and to accelerate the consolidation of surrounding saturated soft soil. The stress-strain behavior of the granular column is governed mainly by the lateral confining pressure mobilized in the native soft soil to restrain bulging collapse of the granular column. The purpose of this work is to assess the suitability of reinforcing technique by stone columns to improve the load carrying capacity of pond ash deposits through several laboratory model tests. This objective is achieved in two parts. In the first stage the characterization of pond ash is made along with the evaluation of the mechanical properties like compaction characteristics under different loading conditions, evaluation of shear strength parameters using Direct shear test, Unconfined compression test, Triaxial test at different testing conditions. This is done basically to find out the inherent strength of the pond ash compacted to different densities and at different degree of saturation. In the second series of tests the shear parameters of the compacted pond ash samples reinforced with stone columns of varying area ratios and length ratios are evaluated from triaxial compression test. In addition to this stone columns having different area ratios and length ratios are introduced in compacted pond ash beds and the bearing capacity of the composite system is evaluated through a series of footing loading tests. For this a circular footing of 75mm in diameter is used.

Mine void filling is required to prevent subsequent earth stability difficulties in the form of subsidence. Stream sand and mill tailings have been commonly used since a long period as backfilling materials. On the other hand, with a strict rule prohibiting river sand mining in India, research for emerging alternative engineering materials replacing sand has gained importance. In India, power generation is mostly dependent on coal based Thermal Power Plant. Pond ash is the mixture of fly ash and bottom ash which are the by-product generated from thermal power plants after the combustion of coal. In the current study, an attempt is made to investigate the feasibility of pond ash as an alternative backfilling material. To achieve the objective, detailed geotechnical and geoenvironmental characterisation of pond ash has been carried out. To assess the strength properties of pond ash mixed with lime, cylindrical specimens were prepared for determining the unconfined compressive strength. The specimens were prepared at four compaction energy. The effect of curing on the strength characteristics of lime treated pond ash was also investigated. Based on the detailed geotechnical and geoenvironmental characterisation of pond ash, it has been found that pond ash is a lighter, silty size material. Pond ash is slightly collapsible in nature and of low compressibility. Based on lime reactivity test, pond ash is a pozzolanic material. Mostly, the heavy metals (i.e. Fe, Ni, Mg and Zn) are found to be within the permissible limit as per IS 10500 (2012). It has been observed that with an increase in compaction energy, the strength of lime treated pond ash is increased. Significant improvement in the compressive strength were obtained after 28 days of curing time. The lime-treated pond ash may be used as an alternative to sand for backfilling the mine voids.

The purpose of this work is to assess the suitability of reinforcing technique to improve the load carrying capacity of pond ash deposits through several laboratory model tests. In the 1st stage uniaxial compressive strength (UCS) tests were done on encased stone column (ESC) with varying slenderness ratio and relative density of compacted stone mass. It is found that load carrying capacity of stone column is directly proportional to the relative density (RD) of stone mass and inversely proportional to the slenderness ratio. In the 2nd series of test UCS test was conducted on ESC of slenderness ratio 2 and 3 reinforced with horizontal strip (HS) reinforcement made of galvanized iron (GI) and PVC mesh. In this case RD of stone mass and spacing between the strips (d, 0.5d, 0.25d, where d is the diameter of SC) was taken as variables. Circular GI strip placed at a spacing of 0.25d with RD 90% enhance the load carrying capacity by 11.44 times over the ESC. In the 3rd stage of experiment load test was conducted on pond ash bed reinforced with SC and ESC which is again strengthened with horizontal GI and PVC strip placed at different positions. Full encasement of SC reduces the bulging diameter and it carries more load than ordinary SC, embedded in pond ash bed. Further ESC reinforced with HS carry much higher load than the other configurations of reinforcement tried in this test. Further, the experimental results are compared with finite element analysis results using the software package PLAXIS and it is found that the ultimate load carrying capacity of stone columns for various reinforcement combinations are in good agreement with each other.

碩士
國立臺灣科技大學
營建工程系
106
Most of the bottom ash generated from the coal burning power plants in Taiwan was often hydraulically dumped to the nearby coal ash ponds located along the coastline. But the hydraulic deposited coal ash is loose and prone to liquefaction during earthquake, especially when it was dumped below the mean sea level (i.e., underwater dumping). Recently, coal ash ponds have been considered to be the site for future expansion of the power plants. So the liquefaction problem of the coal ash pond needs to be seriously dealt with. To avoid liquefaction in the coal ash pond, it is proposed to add cement in the process of hydraulic filling and make it ready for construction as soon as the filling process has completed. However, if the hydraulic filling is carried out underwater, there is a segregation problem of cement and coal ash particles. So, a layered cementash formation inside the coal ash pond is formed. In general, cement and fine particles of coal ash suspended at the upper layer; the larger size particles of coal ash with trace of cement content settled down at the bottom. A 3D finite element model (OpenSeesPL) is adopted here to assess the effects of this cement treated layer formation on reducing liquefaction potential of the coal ash pond under earthquake shaking. From the subsoil condition of the site, the coal ash which was deposited below mean sea level (GL -7.0 to -13.5m) is loose and highly liquefiable under earthquake. If cement is added during hydraulic filling process, a cement - ash formation will be formed and its liquefaction resistance will be analyzed here. It can be seen that by increasing the thickness of cement-coal ash formation, the maximum displacements at the ground surface and the interface between cemented and not cemented ash layers are decreased. Besides, there is no liquefaction occurring in the cemented coal ash layer. However, the time to reach initial liquefaction in the untreated coal ash layer is not affected by changing the thickness of cemented ash layer. In comparison, the time to reach total liquefaction depends on its location (at the upper part or lower part of the liquefiable soil) or the thickness of cemented ash layer. Finally, forming a cemented layer in the coal ash pond has proven to be an effective way to restrain the horizontal ground displacement inside the coal ash pond during earthquake.

Massive urbanization in the recent times has led a high increase in the power demands and eventually an increase in the production of pond ash generated as a waste material from thermal power plants. To decrease the environmental pollution and hazardous effects, it is imperative to utilize pond ash. But pond ash as such does not have enough strength to be used in civil engineering. So, it is advisable to improve the engineering properties of the pond ash by stabilizing it by adding other materials. In the present study effect of lime and ground granulated blast furnace slag (GGBS) on strength and hydraulic conductivity properties of pond ash are determined. Lime as stabilizing agent in different proportions (0, 3, 6, 9, 15 %) and slag as admixture are added in different proportions (0, 5, 10 and 15%) and the compaction characteristics of the resulted mixture were determined by standard proctor test, strength by Unconfined Compressive Strength test (UCS) and hydraulic conductivity by permeability test. The UCS samples were cured for 0, 3, 7, 14 and 28 days and the strength was determined. The permeability samples are cured for 0, 7, 14 and 28 days. The results showed an increment of maximum dry density and decrease in optimum moisture content with an increasing lime content, slag and curing period. The effect of lime and slag content on the strength and hydraulic properties of the pond ash samples at various curing periods are studied. The results are examined and the optimum percentages of slag required for attaining maximum strength at 3% and 15% lime at different curing periods are reported as the desired proportion for stabilization.

One of the significant difficulties before the processing and manufacturing industries is disposal of the lingering waste products. Red mud and pond ash are one of the significant waste results of any aluminum industry. The red mud sample is collected from Vedanta Aluminum Ltd., Lanjigarh and pond ash sample is collected from Rourkela Steel Plant, Rourkela. They disposed the waste material using the Thick Slurry Disposal System, which empowers fast consolidation of the slurry once disposed at the red mud and pond ash site. The undertaking work concentrates on the suitability of red mud and pond ash obtained are to be utilized for construction of dyke and filling material. Several attempts have been made in the past for using red mud as design of tailing dam and pond ash as land filling. In the present work, emphasis has been given on application of red mud and pond ash mix as construction of embankment and as filling material. In the present work, initially red mud and pond ash are examined for the different geotechnical properties. The different trial works incorporate Standard Proctor Test to acquire the maximum dry density (MDD) and optimum moisture content (OMC), specific gravity test. Utilizing the MDD and OMC results, Direct Shear Test, Triaxle Tests of the sample carried to get the shear parameters c and ?. The specimens were likewise tried for their Unconfined Compressive Strength Test and permeability characteristics utilizing both steady head and falling head permeameter to get the coefficient of permeability. After characterization of red mud and pond ash samples for their individual geotechnical properties, the samples were blended in different proportions to get a mix having optimum mix. All the above analyses were carried on every mix to acquire an optimum mix. The outcomes are gathered in graphical form to observe the patterns in the different parameters.To account the experimental findings, the samples were also observed under Scanning Electron Microscope (SEM). From the mineralogical data, presence of toxic elements is observed. The above analysis and results can help in solving the problem of red mud and ash disposal and to a great extent help in increasing the economic benefit of the alumina and thermal industries.

碩士
國立臺灣科技大學
營建工程系
102
Coal ash consists of low density, high water-absorbing, and crushable particles. Its engineering property is different from ordinary granular soil. To use the reclaimed land by coal ash as the construction site of new structures, it needs to improve the engineering property of coal ash. According to the previous research results, the grid type ground improvement method has shown its advantages in operation, efficiency, and quality compared to the sand compaction pile method. However, the topics studied in the previous research are limited to mixing ratio of binding agents, feasibility, materials, and preliminary design concept. No attempt was made to apply this method to practice because no research has been done to find out the relationship between design parameters and anti-liquefaction ability. To ensure the safety of future facilities founded on coal ash, a finite difference method and an effective stress method were used to analyze the liquefaction resistance of grid-type ground improvement in coal ash pond. In this paper, not only the property of coal ash is studied but also the geometry of grid-type improvement are discussed. This study offers a design principle for the panel wall of grid-type improvement. The cost breakdown for the pile foundation installed in grid-type ground improvement and in the sand compaction piles method is provided for the reference of designer.

Fly ash is a very fine material which is produced by burning of pulverized coal in boilers of thermal power plants. Worldwide, more than 65% of fly ash produced from coal power stations is disposed off in landfills and ash ponds. The fly ash is sent to ash ponds in the form of slurry with water since it is economical. This fly ash being finer and lighter than river sand has lower settlement rate, which can be increased by adding a suitable polymer to the ash slurry in the pond. It is desired that the rate of of settling is fast, so that the water can be easily drained out form the ash pond. If the water height is built up for a long period of time, then it will result in the building up off the hydrostatic pressure which may damage the pond and lead to leakage of fly ash-water slurry from the pond causing various industrial hazards. The objective of this report is to provide a detailed study of the settling rates of fly ash in ash pond for polymer (carboxy methyl cellulose) added, and at different concentration levels. This report also aims at suggesting the aspects to be considered while constructing an ash pond for the fly ash disposal. The turbidity of the fly ash-water slurry along with the polymer mixed to it is studied at some specific time intervals with the help of a Nephelo turbidity meter to determine the rate of decrease of turbidity of the clear liquid at the top of the fly ash-water slurry. This helps in determining the optimum concentration of polymer dosage for faster settlement of fly ash. From the experiments conducted and results obtained, it is concluded that the optimum concentration of the polymer solution to be added is 2ppm (2ml of 10-2 range polymer solution). The gravitational settling rate of the fly ash is calculated after the addition of the above concentration of the polymer. It is concluded that the settling rate of fly ash in ash pond of thermal power plants can be increased by the addition of the polymer of optimum concentration.

Vernal pools are small, seasonally filling wetlands found throughout forests of north eastern North America. Vernal pools have been proposed as potential 'hot spots' of carbon cycling. A key component of the carbon cycle within vernal pools is the decomposition of leaf litter. I tested the hypothesis that leaf litter decomposition is more rapid within vernal pools than the adjacent upland. Leaf litter mass losses from litterbags incubated in situ within vernal pools and adjacent upland habitat were measured periodically over one year and then again after two years. The experiment was carried out at 24 separate vernal pools, over two replicate years. This is a novel degree of replication in studies of decomposition in temporary wetlands. Factors influencing decomposition, such as duration of flooding, water depth, pH, temperature, and dissolved oxygen were measured. Mass loss was greater within pools than adjacent upland after 6 months, equal after 12 months, and lower within pools than adjacent upland after 24 months. This evidence suggests that vernal pools of Central Ontario are 'hot spots' of decomposition up to 6 months, but not after 12 and 24 months. In the long term, vernal pools may reduce decomposition rates, compared to adjacent uplands.

博士
國立中央大學
土木工程學系
104
Coal is the most common material used in thermal power plant, and coal ash is the end product after the power generation. The main treatment of coal ash is to hydraulically transport to the ash pound which was built near the power plant, then it become a newly reclaimed land. The new power generator, coal bunker, and wind turbines can be built on this newly land because these facilities always use pile as its foundations. Therefore the pile loading behavior in ash pound is very important for engineer to study. In this study, undisturbed samples and remolded samples are used to conduct a series of laboratories including physical, chemical, and mechanical tests to study the geotechnical properties of coal ash. The test results show that specific gravity of coal ash is 2.29 to 2.37, and complete the primary consolidation in very short time. The filed axial pile load test results in coal ash pound built in Taichung and Linkou thermal power plant show that the effect of improvement is more significant in strain softerning zone. This study designs a model pile test which can provide one way and two way cyclic loading which the highest frequency is up to 0.1Hz and at least 10000 cycles. By using this test equipment, this reserch study the relationship of pile head stiffness, axial load on pile, pile head displacement, and the load cycles. The test results show that the pile displacement will not increase at the small cyclic amplitude after high cycles. The loading type will effect the pile displacement. The cyclic amplitude and number of cycles will not effet resudial load along the pile, and the nuber of cycles will effect the resudial end bearing load of the pile.

碩士
國立臺灣科技大學
電子工程系
101
We propose and experimentally demonstrate the design of a remotely pumped WDM-PON architecture to provide 2.5-Gb/s bidirectional transmission with potential low-cost configuration. In this scheme, we use amplified spontaneous emission (ASE) light source with broad optical spectrum for downstream and upstream transmission. The ASE light source spectrum is sliced by the arrayed waveguide grating (AWG) at the central office (CO) and remote node (RN) and each spectrum slice is used to carrier the signal of a downstream or upstream channel. A reflected electro-absorption modulator (REAM) is used to encode the upstream signals and achieve colorless operation. An electro-absorption modulator (EAM) is used to encode the downstream signals. In order to achieve a transmission up to 25 km distance, a low-dispersion fiber like a larger effective area fiber (LEAF) is used to reduce the dispersion effect. Due to the low power density of ASE source and the insertion loss caused by passive components and modulation, a remotely pumped erbium-doped fiber amplifier (RP-EDFA) is employed to provide extra gain to both downstream signals and upstream signals. The RP-EDFA can compensate the propagation loss and spectral slicing loss. The experimental results show that the downstream and upstream transmission of 2.5Gb/s data rate for each 8 channels can achieve a bit error rate (BER) of lower than 10-9 over 25 km of distance.

碩士
國立臺灣科技大學
電子工程系
101
We have proposed and experimentally demonstrated a novel remotely pumped WDM-PON architecture to provide 10/1.25-Gb/s bidirectional transmission with potential low-cost configuration. In this scheme, we use amplified spontaneous emission (ASE) light source with broad optical spectrum for upstream transmission. The ASE light source spectrum is sliced by the arrayed waveguide grating (AWG) at the remote node (RN). A reflected electro-absorption modulator (REAM) is used to encode the upstream signals and achieve colorless operation. For downstream transmission a laser diode is used as the upstream light source. In order to achieve 10 Gb/s transmission data rate, we use external Mach-Zehnder modulator to carry the downstream data. The remotely pumping scheme can compensate the double-pass optical loss and enhance the signal to noise ratio. The remotely pumped architecture may give nonuniform gain for different wavelength channels. In order to provide fair performance to all the channels, a slanted gain flattening filter (GFF) was added to improve the power nonuniformity for the upstream signals.

博士
國立臺灣科技大學
電子工程系
104
We propose and demonstrate a remotely pumped WDM-PON architecture to achieve 10 Gb/s symmetrical bandwidth for bidirectional transmission. In this scheme, a wideband amplified spontaneous emission (ASE) from an optical amplifier is sliced into multiple channels by an arrayed waveguide grating (AWG) and used as multi-channel optical sources for WDM-PON system. Each channel is noise suppressed by using a gain-saturated cascaded semiconductor optical amplifer (SOA) and then modulated at 10.7 Gb/s of nonreturn-to-zero (NRZ) signals by using electrochromic absorption modulator (EAM), assuming forward error correction (FEC) with 7% overheads for improving the bit error rate (BER) of system. We also propose a redband-seeding scheme to provide uplink seeding light and use a reflected electro-absorption modulator (REAM) to encode the upstream signals. In order to achieve a transmission up to 25 km distance, we use a larger effective area fiber (LEAF) to reduce the dispersion effect. To compensate the loss by passive components and modulation, we employ a remotely pumped erbium-doped fiber amplifier (RP-EDFA) to provide extra gain for both downstream and upstream signals. The experimental results show that the downstream and upstream transmission can provide 10 Gb/s data rate over 25 km for 32 channels, which corresponds to a total capacity of 320 Gb/s, on each direction.

碩士
國立臺灣大學
光電工程學研究所
96
In this thesis, we use amplified spontaneous emission injection-locked reflective semiconductor optical amplifier directly modulated at 622 Mbit/s and 1.25 Gbit/sec with detuning injection-locked mode for quasi-color-free transmission in DWDM-PON system with channel spacing of 200 GHz. With biased current changing from 0.9 Ith to 1.4 Ith, the improvement on receiving power sensitivity for the WRC-FPLD based WDM-PON transmitter is up to 9 dB at bit-error-rate (BER) of 10-9. Increasing the injection-locked mode number from 2 to 3 within temperature variation of 6oC effectively promotes the BER from 10-8 to 10-10 at receiving power of -27 dBm associated with a decreasing power penalty of -3.2 dB. In addition, ASE power and injection-locked mode number dependent frequency chirp and bit error rate responses of a weak-resonant-cavity Fabry-Perot laser diode (WRC-FPLD) transmitter in wavelength division multiplexing passive optical network are characterized. Chirp analysis of upstream data from the 1.25Gbit/s directly modulated WRC-FPLD with two or three injection-locked modes after the 200GHz AWG filtered ASE injection-locking is determined, which reveals the peak-to-peak chirps of -0.8 and -1 GHz with corresponding negative chirp parameters of -1.6 and -2 MHz/ps for two- and three-mode lasing WRC-FPLD, respectively. Such a negative chirp further enlarges to -6.4 and -9 GHz after 25-km single-mode fiber (SMF-28) transmission. The BER of below 10-9 at receiving power below –30 dBm is obtained with mode number dependent power penalty of <0.25 dB before and after 25 km SMF-28 transmission. A chirp model involved the ASE injection induced power saturation effect is derived to explain the negatively frequency chirped WRC-FPLD, which reveals a reverse trend with increasing ASE injection power due to the power-saturation induced on/off extinction ratio reduction (from 10.5 to 8.2 dB) and rising-time broadening (from 120 to 180 ps) on WRC-FPLD transmitted data shape, which effectively reduces the peak-to-peak chirp by at least 2 GHz after 25-km SMF transmission. Furthermore, the effect of AWG filter bandwidth on the transmission performances of the amplified spontaneous emission injection-locked Fabry-Perot laser diode based 1.25 Gbit/s direct modulated DWDM-PON transmitter, in which the DWDM AWG filter with two different channel spacings of 50 and 200 GHz for effectively raising network capacities and reducing the crosstalk induced by interfered reflection are compared. By filtering the ASE source with another 200 GHz AWG filter local ONU part, the AWG induced reflection is minimized to improve the upstream data with a negative power penalty of 1.6 dB. In contrast, the use of a 50 GHz channel-spaings AWG is unable to promote a better BER, where as leading to a power penalty of 1.5 dB for the back-to-back transmission case due to the slight increasing ratio of RIN noise to signal intensity are compared to the 200 GHz AWG based system.

碩士
國立臺灣科技大學
電子工程系
100
A real time TDM-PON (Time Division Multiplexing Passive Optical Network) monitoring system is proposed in this thesis. In the proposed system, the ASE (Amplified Spontaneous Emission) which is generated by the EDFAs (Erbium Doped Fiber Amplifier) is modulated by an RF or short bit stream signal and employed as the network supervisory signal for the system. At the ONUs (Optical Network Units), two different monitoring schemes, the RF phase shifting and the digital time difference adding techniques, are used to demodulate the supervisory signals sent from the OLT (Optical Line Terminal). Through the proposed network architecture and modulation schemes, a PON network can be properly real –time monitored without using extra communication channels.

碩士
國立臺灣科技大學
電子工程系
102
We propose and demonstrate a remotely pumped WDM-PON architecture to achieve 10 Gb/s symmetrical transmission. In this scheme, a wideband amplified spontaneous emission (ASE) from an optical amplifier is sliced into multiple channels by an arrayed waveguide grating (AWG) and used as multi-channel optical sources for WDM-PON system. Each channel is noise suppressed by using a gain-saturated cascaded semiconductor optical amplifer (SOA) and then modulated at 10.7 Gb/s, assuming forward error correction (FEC) with 7% overheads. We also propose a cross-seeding scheme to provide uplink seeding light and use a reflected electro-absorption modulator (REAM) to encode the upstream signals. In order to achieve a transmission up to 25 km distance, we use a larger effective area fiber (LEAF) to reduce the dispersion effect. To compensate the loss by passive components and modulation, we employ a remotely pumped erbium-doped fiber amplifier (RP-EDFA) to provide extra gain for both downstream and upstream signals. The experimental results show that the downstream and upstream transmission can provide 10 Gb/s data rate over 25 km for 32 channels, which corresponds to a total capacity of 320 Gb/s, on each direction.