Dynamic properties of soils (shear stiffness and damping ratio) are critical for the design of structures subjected to vibrations. The dynamic properties of a benchmark standardized laboratory sand (Ottawa silica sand) were evaluated with two different resonant column devices, utilising software with different analytical approaches for the evaluation of soil properties. The dynamic properties (shear modulus and damping ratio) are evaluated as a function of the shear strain level. The results are compared to evaluate the effect of the type of equipment and the form of the data analysis on the measured dynamic properties of the samples. The results are discussed in light of the applicability of the procedures in practice, the ease of the testing methods, and the errors they introduced into analysis and design. In general, the shear wave velocities obtained from the two different devices are in good agreement. However, the damping ratios they give show considerable differences as strains increase. Dynamic properties are typically measured by curve fitting of the transfer function between the excitation and the response using the resonant column device. However, the force function generated by sinusoidal sweep or random noise excitations induce different shear strain levels at different frequencies. Consequently, the shape of the measured transfer function is distorted and differs from the theoretical transfer function for an equivalent single-degree-of-freedom system. The difference between the measured and theoretical transfer functions as well as the bias in the computed dynamic properties becomes more pronounced with the increase in shear strain. This study presents a new methodology for the evaluation of dynamic properties from an equivalent constant-strain transfer function. The soil specimen is excited simultaneously using a sinusoidal excitation (carrier signal) at the required strain level and a small amplitude, narrow band random noise. The strain level induced by the fixed sine is shown to control the resonant frequency of the specimen; whereas the random noise introduces the required frequency bandwidth to determine the transfer function and hence the dynamic properties at a constant strain level. The new methodology also shows a good potential for the evaluation of frequency effects on the dynamic properties of soils in resonant column testing.

This work focuses on developing an inversion scheme to estimate water-column sound-speed fields in three dimensions. The inversion scheme is based on a linearized perturbative technique which utilizes estimates of modal travel times. The technique is appropriate in the littoral ocean where measurements are made across range and cross-range distances greater than 10 km to ensure sufficient modal dispersion. Previous applications of then inversion technique has been limited to one or two dimensions and/or focused primarily on the seabed. Compared to past applications, the accuracy and uncertainty of the solution is improved by employing approximate equality constraints within the context of \textit{a priori} estimates of model and data covariances. The effectiveness of the constrained technique is explored through a one-dimensional example. The robustness of the technique is illustrated by introducing different types of errors into the inversion and considering the accuracy. A further examination of the technique is given by exploring a three-dimensional example. Several case studies are presented to investigate the effects of different levels of environmental variability and spatial sampling. / text

Oscillating Water Column (OWC) device is a relatively practical and convenient way that converts wave energy to a utilizable form, which is usually electricity. The OWC is kept inside a fixed truncated vertical cylinder, which is a hollow structure with one submerged open end in the water and with an air turbine at the top. The research adopts potential theory and Galerkin methods to solve the motion of the OWC. Based on the air-water interaction model, optimal OWC design for energy extraction from regular wave is explored. The hydrodynamic coefficients in scattering and radiation potential are solved using Galerkin approximation. The numerical results for the free surface elevation have been verified by a series of experiments conducted in the University of New Orleans Towing Tank. The effect of geometric parameters on the response amplitude operator (RAO) of OWC is studied and amendment of the equation for evaluating the natural frequency of the OWC is made. Using the model of air-water interaction under certain wave parameters and OWC geometric parameters, a computer program OWC Solution is developed to optimize the energy output from the system. Optimization results by the program OWC Solution lead to an effective method to design the OWC system.

The existence of small-scale gold mining in Nova Scotia between 1868 and 1942 has resulted in many high arsenic (As) tailings areas in the province, some of which are near rural/urban areas and are used for recreational activities such as dirt bike racing and all-terrain vehicle (ATV) riding. Because of the natural association of As with gold ore in the Meguma Terrane, processing of ore has resulted in As-rich mine waste that contains up to 2500 times more As than the Canadian soil quality guideline of 12 mg/kg. These high As concentrations in combination with the recreational use of these sites creates a risk of human exposure. The objective of this work was to investigate the effects of different cover options that might be used to mitigate the risk of human exposure. Four tailings samples were selected to represent the geochemical variability from two tailings areas: Montague gold mines and Goldenville. These samples were characterized and subjected to 29 weeks of column testing, in which each sample was leached with three different input solutions including synthetic rainwater (to simulate uncovered tailings exposed to natural acid rain), synthetic rainwater equilibrated with calcium carbonate (to simulate rainwater percolation through a crushed limestone cover), and a dilute organic acid solution (to simulate a vegetative cover). Results of acid base accounting (ABA) tests indicate that samples have the potential to generate acid in the future (ratio of neutralization potential to acid potential is less than 2), though surface water at the sites is currently circum-neutral. Acidic paste pH values (2.9) from a sample of As-rich hardpan indicate that a small volume of tailings at Montague are currently generating acid. Results of column testing indicate that the cover types simulated by the input solutions had less of an effect on the out-flowing leachate chemistry than did the small volume of secondary As phases in each sample (scorodite, yukonite, hydrous ferric arsenate and hydrous ferric oxides). For the majority of sample types, columns leached with an organic acid solution reported higher leachate As concentrations than were reported from columns leached with either the rainwater or carbonate-rainwater solutions. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2010-10-27 14:26:06.13

Difficulties with reproducibility of isolation yields when distilling 211At from irradiated bismuth targets led us to use a “wet chemistry” approach for that process1. The wet chemistry approach has provided 211At isolation yields of ~ 78 % after decay and Bi attenuation corrections2. However, the use of diisopropyl ether (DIPE) in the separation process has made it difficult to reach our goal of automating the 211At isolation. Therefore, we have investigated the use of column materials to simplify the isolation of 211At and remove DIPE from the process. In this investigation we evaluated the use of a strong anion exchange resin (AG1×8), a strong cation exchange resin (AG MP-50) and a polyethylene glycol (PEG)-coated resin for separation of 211At from the bismuth target material. Anion and cation resins AG1×8 and AG MP-50 were obtained from commercial sources. A PEG-coated resin was prepared by reaction of the Merrifield resin with mPEG-OH 2000 in the pres-ence of tBuOK at 80 °C for 3 days, followed by drying under vacuum. Prior to use of the PEG resin, it was soaked in H2O. Resins (400–800 mg) were loaded into polypropylene columns (Applied Separations, Inc.). Column elution studies were conducted with and without reductants (0.75M FeSO4/1M H2SO4 or Na2S2O5) to determine their effect on capture of 211At. After target dissolution in HNO3 (and in most cases subse-quent removal of HNO3 by distillation and redis-solution of solid in 8M HCl), 211At solution was loaded onto the column, then the column was washed with 2M HCl or H2O to separate the Bi, and finally was eluted with strong base to remove the 211At. Initial studies were conducted with stable iodine to determine if reductants were effective in the presence of large amounts of bismuth ions. Studies with AG1×8 used 125I to determine if that radiohalogen could be captured and recovered from the column when eluting with boric acid buffers at pH 5.3, 8.0 or 10, or H2O at pH 7. Capture and recovery of 211At was evaluated under the same conditions. Further studies with AG1×8 involved eluting with 4M H2SO4. A limited study with AG MP-50 resin used 1M HCl as eluant. Studies with PEG-coated columns used 2M HCl, 4M HCl, 8M HCl, 16 M HNO3 and 8M HNO3 as initial (capture) eluants. Strong base (0.2, 1 or 12.5 M NaOH; 15M NH4OH) and 3 or 500 mM tetrabutylammonium bromide (TBAB) were evaluated for removal of 211At from the columns tested. The efficiency for capture of 211At on the AG1×8 column was high (99%) when loading with strong acid, but decreased when using 0.1–0.2M boric acid (69–91 %) buffer. Low 211At capture efficiencies were obtained with AG MP-50 col-umns (15–29%). High 211At capture efficiencies (96–100%) were obtained with PEG-coated resins when loading with 8M HCl or 8M HNO3, irre-spective of whether reductant was in the acid solution. Four column washings (2 mL of 2M HCl each) were required to remove all Bi prior to elution of 211At. No bismuth was detected in solution from the 4th washing in any of the elutions studied. Low (< 6%) recovery of 211At from the AG1×8 columns was obtained using the conditions studied. Good (60–79%) recovery of 211At was obtained from PEG-coated resin using 15M NH4OH. Isolation of the 211At from NH4OH solution was accomplished by distillation. In an initial study 211At distilled before obtaining a dry residue. However, later studies demonstrated that addi-tion of NaOH prior to distillation kept the 211At in the distilling flask. These studies demonstrated that PEG-coated columns could be used to isolate 211At from HNO3-dissolved bismuth targets with good non-optimized (~60%) overall recovery yields. The studies are continuing with optimization of elu-tion conditions and automation of the process.

No description available.

Dynamic properties of soils (shear stiffness and damping ratio) are critical for the design of structures subjected to vibrations. The dynamic properties of a benchmark standardized laboratory sand (Ottawa silica sand) were evaluated with two different resonant column devices, utilising software with different analytical approaches for the evaluation of soil properties. The dynamic properties (shear modulus and damping ratio) are evaluated as a function of the shear strain level. The results are compared to evaluate the effect of the type of equipment and the form of the data analysis on the measured dynamic properties of the samples. The results are discussed in light of the applicability of the procedures in practice, the ease of the testing methods, and the errors they introduced into analysis and design. In general, the shear wave velocities obtained from the two different devices are in good agreement. However, the damping ratios they give show considerable differences as strains increase. Dynamic properties are typically measured by curve fitting of the transfer function between the excitation and the response using the resonant column device. However, the force function generated by sinusoidal sweep or random noise excitations induce different shear strain levels at different frequencies. Consequently, the shape of the measured transfer function is distorted and differs from the theoretical transfer function for an equivalent single-degree-of-freedom system. The difference between the measured and theoretical transfer functions as well as the bias in the computed dynamic properties becomes more pronounced with the increase in shear strain. This study presents a new methodology for the evaluation of dynamic properties from an equivalent constant-strain transfer function. The soil specimen is excited simultaneously using a sinusoidal excitation (carrier signal) at the required strain level and a small amplitude, narrow band random noise. The strain level induced by the fixed sine is shown to control the resonant frequency of the specimen; whereas the random noise introduces the required frequency bandwidth to determine the transfer function and hence the dynamic properties at a constant strain level. The new methodology also shows a good potential for the evaluation of frequency effects on the dynamic properties of soils in resonant column testing.

The potential for mobilization of SO4 and Cl from coal stockpiles and coal processing waste and refuse (waste rock) disposal areas to the receiving streams and groundwater is an environmental concern and proper management practices are necessary to minimize the impact of these discharges. In an effort to characterize the long-term environmental impact of weathering in from both a typical coal stockpile and coal waste disposal areas a series of laboratory- scale and field-scale kinetic tests were performed with the ultimate goal of improving both coal and coal waste management at coal mines in a manner that minimizes the discharge of sulfate (SO4) and chloride (Cl). Laboratory experiments demonstrated that kinetic testing is a productive method for understanding the chemistry of surface water discharges from coal stock piles. However, these tests proved to be problematic in simulating the weathering of coal refuse. In an effort to improve the kinetic tests, field test columns were constructed that eliminated this deficiency. Unfortunately, field-scale test columns were found to be difficult to construct and, due to extremes weather events, difficult to maintain for an adequate test period. In the course of the experiment elemental and mineralogical data were collected both before and after weathering of fresh, run-of-mine coal from the Springfield (No.5) coal seam and coal refuse samples from processing the Springfield (No. 5) and Herrin (No. 6) coal seams. Duplicate columns were constructed in 2008 to conduct kinetic testing of the fresh run-of-mine No. 5 coal collected at an active underground mine in Southeastern Illinois. These columns measured 15.4 cm (6-inch) diameter by 61 cm (2-ft.) tall and were leached in batch mode for 32 months (27 leach cycles) using locally-collected rainfall water at a rate consistent with climatic data. Similarly, triplicate columns were constructed in 2009 to conduct kinetic testing of fine and coarse coal collected at the cooperative mine. The coal refuse test columns also measured 15.4 cm (6-inch) diameter by 61 cm (2-ft.) tall and were leached in batch mode for 41 months (31 leach cycles). Coal refuse was emplaced into the columns using a measured amount of compaction and a controlled moisture content (15.3%) based on data from previous laboratory engineering tests (Proctor testing). Locally-collected rainfall water was again used for leaching at a rate consistent with climatic data. Three columns investigated the leaching of compacted coarse refuse (the control) and three columns investigated the leaching of compacted 80:20 blend of coarse and fine refuse. To verify the results of the laboratory-scale, kinetic tests on coal refuse six field-scale (208 L or 55 gal.) columns were constructed in 2011 which measured 57.2 cm (22.5-in.) diameter by 85.1 cm (33.5-in.) tall and were leached in batch mode for 18 months (17 leach cycles). Two columns were again investigated the leaching of compacted coarse refuse (the control), while two additional columns leached compacted 85:15 blend of fine and coarse refuse and two columns tested a 80:10:10 blend of coarse refuse, fine refuse, and ground limestone. These field-scale tests allowed the use of full-sized refuse particles and were subject to natural precipitation events. An improved geochemical data set was obtained by these experiments due to an extension of the laboratory kinetic tests from 12 to 32 months to better simulate a mine-site stockpile conditions. Similarly, kinetic tests on coal refuse were extended from 12 to 41 months to better simulate SO4 and Cl release from a coal refuse facility. Three coal refuse disposal options were investigated in these experiments: 1) compacted coarse refuse (the control), 2) a compacted blend of fine and coarse refuse and 3) a compacted blend of coarse refuse, fine refuse, and ground limestone. Trends observed during the course of this research in leachate chemistry, as well as, comparisons of refuse placement options provide important insights necessary for development of management practices which minimize SO4 and Cl in coal mine discharge. The observed temporal changes were largely due to the presence of carbonate and aluminum mineral buffering of pH; three stages were observed during the kinetic testing of the Springfield (No.5) coal (Stages 1 through 3). Conversely, only Stage 1 and Stage 2 were observed in leaching tests of coal refuse due to the greater amount of compaction, which reduced the hydraulic conductivity and slowed the weathering rate. The identification of these three stages is important because of the improvement in coal and coal refuse management and water quality treatment realized by an understanding of these geochemical trends. The stages observed in the coal column leachate are: Stage 1: Laboratory coal column leachate collected during the first 7 months of simulated weathering of the No.5 coal maintained a favorable pH (> 6.4) maintained by an excess in bicarbonate alkalinity which minimized discharge of SO4 and common coal mine drainage metal Fe. The concentrations of Na and Cl in the leachate were elevated in early leach cycles, but declined rapidly as water soluble salts were flushed from the coal columns, which was an indicator that a portion of the Cl was water soluble forms such as salts and dissolved Cl- ions in pore water and not bound to the organic structure. Stage 2: A transitional period (Stage 2) occurred during the next 3 months of simulated coal stockpile weathering (7 to 10 months). This stage marked the exhaustion of the carbonate mineral buffer and an acceleration of coal weathering. Stage 2 leachate was characterized by a rapid decrease in the leachate pH to 4.0 and an increase in concentration of SO4 and dissolved Fe. Both Na and Cl in the leachate continued to decline in Stage 2, but the release related to flushing rate and not pH. Stage 3: After 10 months of simulated coal stockpile weathering, the leachate pH continued to slowly decrease to values below 2.0. At the same time the SO4 concentration increased rapidly and Fe concentration increased by over a factor of ten. The decline in pH was believed to have been restricted by iron and possibly aluminum mineral buffering during Stage 3. The release of Na and Cl in the coal increased somewhat during Stage 3 presumably due to slaking of shale contain in the ROM coal and the subsequent increase in the exposure of the soluble portion of the Cl to weathering and flushing. Laboratory leach testing of the Springfield (No.5) Coal from Southeastern Illinois suggests that: (1) SO4 levels in coal stockpile discharge would be relatively low up to ≈7 months. This time period, therefore, should correspond to the operational limit of run-of-mine (ROM) coal storage for this case example; and (2) Elevated discharges Cl- and the Na+ counter ion occurs immediately and may require control by operational measures (dilution and/or periodic blow down from a closed loop water handling system) to minimize Cl. A favorable leachate pH of > 6.4 which typified Stage 1 was also maintained throughout the laboratory-scale experiments for all blended coal refuse and in two of three columns simulating coarse coal refuse. Lower pH conditions similar to Stage 2 in the coal study was observed in leachate from only one of three coarse refuse columns after ≈12 months of kinetic testing. In all laboratory column experiments, the concentrations of Na and Cl in the leachate were elevated in early leach cycles, but declined rapidly as water soluble salts were flushed from the coal refuse columns. However, in the field column experiments favorable pH conditions (> 6.4) were only maintained throughout the 18 month experiment in the two columns which received a relatively high amount or ground limestone addition (10%). Lower pH conditions similar to Stage 2 observed in the coal leachate tests were observed in leachate from two coarse refuse columns and one of two blended refuse columns after ≈12 months. Complementary laboratory and field kinetic testing of coal refuse also suggest that: 1) SO4 levels in simulated coal refuse disposal area can be minimized by systematic compaction and co-disposal of properly dewatered fine and coarse refuse, and 2) elevated Cl (and Na) discharges occur immediately, which may require operational measures such as dilution and/or periodic blow down from the mine’s closed loop system. In most cases all of these measures can be completed using existing facilities at minimal additional costs. This dissertation provides insights into the potential for long-term discharge of SO4 and Cl from coal processing facilities in the Southeastern part of the Illinois and the operational controls that should be considered to minimize these impacts. Additional studies are suggested to confirm the findings with different coal seams and mining regions in the Illinois basin. Some notable findings include: 1) An increased understanding of coal and coal refuse leachate geochemistry can be expected by extending kinetic testing from the normal short-term tests (<12 >months) to longer-term testing (32-41 months). By conducting long-term (>12 months) kinetic tests additional observations were possible regarding limitations on rate of release of Cl and SO4 by both carbonate mineral buffer (pH 6.4) and an mineral ferrihydrite buffer at pH ≈3.4, as well as, increases due to chemical and physical weathering (slaking) of the materials. An understanding of the bicarbonate buffer is necessary to design operational controls during mining and reclamation and to evaluate the impact of alkaline (i.e. limestone) additions. 2) Kinetic testing of coal refuse should simulate real-world placement of these materials in a disposal area. Current coal mining practices require both the placement and compaction of coarse or blended refuse, which is not duplicated in kinetic methods employed by previous investigators that conducted tests using relatively loose-packed materials. Kinetic testing of non-compacted coal refuse is inconsistent with mine safety regulations in the U.S. dictate that compaction will be required for the structural stability of the coal refuse facility. Therefore, this experiment improved on the conventional kinetic testing methodology and provides a more appropriate estimate of the weathering rates as they relate to the release of SO4 and Cl from these materials. However, due the low hydraulic conductivity of the compacted refuse blends the laboratory column leachate volumes were inadequate to conduct key alkalinity analyses when rainfall was applied at physically realistic rates. Larger volume field columns may, therefore, serve as a better alternative. 3) Limitations on the mobility of the powerful oxidant, ferric iron (Fe3+), created by compaction and the presence of alkaline materials that support the presence of a bicarbonate buffer are critical in controlling the release of SO4. 4) Increased compaction in the two coal refuse blends would be expected to restrict the hydraulic conductivity and, therefore, flushing rate of the refuse and, as a result, reduce the corresponding release of Cl. However, the reverse was observed which was due in part to the high release rate of the soluble portion of the Cl from fine-grained materials, which in this case was the <200 mesh>(<0.074mm) fine coal processing waste. Moderate additions (<5%) of fine-grained (< 1 cm) limestone provides both an increased stability of blended coal refuse due to its role as a drying and cementing agent. The environmental benefit of limestone addition to coal refuse blends is the reduction of SO4 release due to: 1) Lower infiltration of H2O and O2(g) as the result of improved compaction, and 2) Increase in the net neutralization potential which results in increased bicarbonate mineral buffering. However, it is recognized that due to the size of these facilities limestone additions at the rate suggested by this research would be costly.

The main purpose of this study is to build upon previous post buckling research by including the effects of material degradation on column strength due to temperature increase. Failure of a structure during a fire occurs in most part because of material degradation. As the temperature increases the stiffness and strength of a structural material decreases and ultimately results in failure. In this study, columns with three different types of end restraints were studied. These are: Pinned-Pinned Columns, Pinned-Fixed Columns, Fixed-Fixed Columns. For each end-restraint type three different slenderness ratios were considered: λ=50, λ=125, and λ=200. After the data was reviewed, some conclusions that can be made are Axially restricted columns with lower slenderness ratios are more affected by material degradation. This is because columns with lower slenderness ratios have a higher Tcr allowing the effects of material degradation to begin affecting the columns strength at much lower T/Tcr ratios, in some cases before the ratio even reaches 1. Axially restricted columns with a higher number of rotational end-restraints are more affected by material degradation. This can also be attributed to a higher Tcr that allows the effects of material degradation to begin affecting the columns strength at much lower T/Tcr ratios.

No description available.