bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristics of Hydrostatically Extruded Zr-2.5Nb Alloy
Authors: Jie Z , Zhenhe L , Wenxian H , Yunxia Z , Jiaqi D , Yan L , Tieqi Y
Published: December 2008

Hydrostatic extrusion is a new production technology. Zr-2.5Nb alloy tubes cold hydrostatically extruded possess excellent mechanical properties similar to heat-treated tubes and better than cold-worked tubes. Examination by transmission electron microscope shows that the alloy is of a uniform cell substructure containing the (α + β) phases, which is one of important factors improving properties of the alloy.

The study of texture, stress, and reorientation of the hydride shows that hydrostatically extruded tubes with basal plane normals in the radial direction have obviously higher hydride reorientation threshold stress than tubes with basal plane normals in the circumferential direction.

Moreover, investigation of fracture toughness reveals that hydride distributed perpendicular to the crack propagation direction restrains further propagation of the crack. It is favorable for preserving the fracture resistance of the material.
Pressure Tube Development for CANDU Reactors
Authors: Fleck RG , Price EG , Cheadle BA
Published: December 2008

A development program is described in which reactor grade Zr-2.5Nb pressure tubes were produced with properties comparable to current reactor tubes but which are expected to show lower in-reactor creep and growth. Lower creep and growth rates would mean smaller axial elongations of tubes in service.

Evaluation of the tubes showed that they met the specification requirements and compared favorably with tubes produced by the current route. Early in-reactor creep tests suggest that the development tubes will exhibit similar diametral creep behavior to current tubes. In-reactor growth tests have not yet reached steady-state behavior. The properties and possible reasons for the behavior are reported and discussed.
A Study on the Nonelastic Behavior of Zircaloy Fuel Cladding
Authors: Suzuki H , Okubo T
Published: December 2008

Load relaxation tests, creep and abrupt stress change tests, and tension tests were performed on unirradiated, annealed Zircaloy-2 and stress-relieved Zircaloy-4 at temperatures ranging from 473 to 648 K. Experimental results were analyzed by using a unified phenomenological constitutive model originally proposed by Hart. All the parameters included in the model were determined. Using the parameters, the model was employed to integrate numerically along the loading conditions under which experiments were performed. The model showed reasonable accuracy and was demonstrated to be applicable for describing nonelastic deformation of Zircaloy cladding.
Application of Alternating-Current Impedance Measurements to Characterize Zirconium Alloy Oxidation Films
Authors: Rosecrans PM
Published: December 2008

In an effort to understand observed differences in high-temperature steam corrosion resistance, high-frequency (>500 Hz) a-c impedance measurements have been used to monitor the permeability of oxidation films formed on Zircaloy-2 and Zircaloy-4 specimens exposed to high-temperature steam. Differences in oxidation resistance are related to differences in oxidation film permeability and ultimately to film characteristics. When these results are added to the existing data base established for zirconium alloy oxidation films using the high-frequency impedance technique, improved understanding of the role of bulk corrodent access to the metal-oxide interface during oxidation becomes possible. In addition, differences in film character resulting from differences in oxidation environment become apparent upon review of the existing data base. Such differences may have practical application in selecting material preconditioning procedures and suggest explanations for some oxide film memory effects reported in the literature.
Estimation of Conservatism of Present Embrittlement Criteria for Zircaloy Fuel Cladding Under LOCA
Authors: Furuta T , Uetsuka H , Kawasaki S
Published: December 2008

To estimate the degree of conservatism of the present embrittlement criteria, the following examinations have been conducted. Zircaloy-4 tubes were oxidized at temperatures ranging from 1173 to 1573 K, and then compressed at 373 K to determine the embrittlement due to oxygen absorption. The simulated Zircaloy-clad fuel rods were burst and oxidized in steam at temperatures within the range 1200 to 1500 K. The segment sectioned from each burst cladding was also compressed to determine the effect of hydrogen absorption on cladding embrittlement. The results obtained from these experiments have revealed that the additional embrittlement due to hydrogen absorption is found to be significant in burst cladding.

The simulated Zircaloy clad fuel rods were burst and exposed to steam at isothermal temperatures ranging from 1173 to 1573 K and then bottom-flooded at the oxidation temperature or 773 K with water, after the specimen was restrained at the end of exposure time. The specimens were also bottom-flooded under a nonrestrained condition to determine the effect of restraining stress on thermal-shock-failure characteristics. The presence of restraining stress limits the permissible oxidation condition to lower temperature and shorter exposure time. Even the estimated thermal-shock-failure boundary under a restrained condition is located above the 15% oxidation line which is adopted by the present criteria.
Out-of-Pile Experiments on the High-Temperature Behavior of Zircaloy-4 Clad Fuel Rods
Authors: Hagen S
Published: December 2008

Out-of-pile experiments have been performed to investigate the escalation in temperature of Zircaloy-clad fuel rods during heatup in steam due to the exothermal Zircaloy steam reaction. In these tests single Zircaloy/uranium dioxide (UO2) fuel rod simulators surrounded with a Zircaloy shroud—simulating the Zircaloy of neighboring rods—were heated inside a fiber ceramic insulation. The initial heating rates were varied from 0.3 to 2.5 K/s.

In every test an escalation of the temperature rise rate was observed. The maximum measured surface temperature was about 2200°C. The temperature decreased after the maximum had been reached without decreasing the input electric power. The temperature decreases were due to inherent processes including the runoff of molten Zircaloy. The escalation process was influenced by the temperature behavior of the shroud, which was itself affected by the insulation and steam cooling.

Damage to the fuel rods increased with increasing heatup rate. For slow heatup rates nearly no interaction between the oxidized cladding and UO2 was observed, while for fast heatup rates the entire annular pellet was dissolved by molten Zircaloy.
Fuel Rod Deformation in LOCA and Severe Core Damage Accidents
Authors: Burman DL , Davis DD , Hochreiter LE , Lutz RD
Published: December 2008

The use of standard creep rate correlations and a burst criterion based on local true stress to evaluate Zircaloy cladding ballooning and burst strain is discussed. Burst strains calculated by this means are shown to follow the trends observed in tubing burst tests. Calculation of the ballooning strains for the Three Mile Island-2 fuel rods, ignoring the effects of oxidation, are discussed.
Physical and Chemical Phenomena Associated with the Dissolution of Solid UO2 by Molten Zircaloy-4
Authors: Hofmann P , Kerwin-Peck D , Nikolopoulos P
Published: December 2008

Laboratory experiments were performed in the temperature range 1800 to 2000°C in inert gas to study the chemical interaction between solid uranium dioxide (UO2) and liquid Zircaloy-4, and the wettability of UO2 by molten Zircaloy as functions of time and Zircaloy oxygen concentration. The experiments were interrupted after various reaction times to determine the extent of the chemical interaction and of the UO2 dissolution. The results show that the dissolution of UO2 by molten Zircaloy is primarily a chemical process, and that the extent of the interaction depends on the wettability of UO2 by molten Zircaloy. The wettability, however, depends strongly on the oxygen content of the Zircaloy and therefore on the time of UO2/Zircaloy contact. The wettability improves with increasing oxygen content. Zircaloy reduces UO2 to form a homogeneous [uranium, zirconium, oxygen (U,Zr,O)] melt at low oxygen concentrations or a heterogeneous (U,Zr,O) melt which contains (U,Zr)O2 particles at high oxygen concentrations. During cooling, the (U,Zr,O) melt decomposes into a (U,Zr) alloy with high uranium content and oxygen-stabilized α-Zr(O).

The amount of fuel which can be liquefied by molten cladding depends on the initial oxygen content of the melt. Oxygen-free liquid Zircaloy can dissolve considerably more UO2 than Zircaloy rich in oxygen.

The significance of these experiments is that UO2 fuel can be “liquefied” by molten Zircaloy far below the melting point of UO2.
Elastic-Plastic Properties of Submerged Arc Weld Metal
Authors: Van Der Sluys WA , Emanuelson RH , Futato RJ
Published: December 2008

The results of a study conducted over a number of years to characterize the elastic-plastic fracture properties of submerged arc weld metal are presented in this paper. The fracture properties of four different weldments were investigated at temperatures ranging from 24 to 288°C (75 to 550°F). Tests were conducted using both the conventional multiple-specimen JIc procedure as well as an automated single-specimen unloading compliance technique capable of generating the material JI-R curve.

Test results obtained using the two different procedures are compared. The comparison indicates that while both test techniques generate comparable J-Δa data for a given test condition, JIc values from the respective sets of data can differ. This is attributed largely to the sparsity of data generated by the multiple-specimen technique and the nonlinearity of the JI-R curves as revealed by the single-specimen technique.

Welding procedure was found to have a significant effect on measured toughness. A wide range of fracture behavior was observed. The welding parameters responsible for the observed behavior are discussed. The applicability of the current JIc and JI-R curve test procedures over the wide range of crack growth behavior observed is discussed.
On the Determination of Elastic-Plastic Fracture Material Parameters: A Comparison of Different Test Methods
Authors: Hollstein T , Blauel JG , Voss B
Published: December 2008

J-initiation values and J-resistance curves are the most promising candidates for the characterization of fracture resistance of materials used in the transition and upper shelf toughness region. Though their use for prediction of initiation of crack growth and of ductile tearing instability was successfully demonstrated in evaluations of large-scale tests, there still remain several problems concerning the determination of initiation values and generation of J-resistance curves. This paper reports on results of investigations conducted on different materials with different specimen types. It covers the comparison of different methods for initiation detection and J-resistance curve determination and the influence of side grooves and specimen dimensions. For both the measurement of J-initiation values Ji and J resistance JR, the DC potential drop technique, the partial unloading compliance technique, and the multiple specimen interrupted loading procedure were used on compact specimens with dimensions ranging from B = 12 5 to 100 mm. The tests were carried out in a temperature range of 25 to 600°C (77 to 1112°F). The generated J-resistance curves agree very well, but slightly different values of crack initiation were determined. The definition of initiation of crack growth is discussed.
The Use of the Partial Unloading Compliance Method for the Determination of JI-R Curves and JIc
Authors: Voss B , Mayville RA
Published: December 2008

A computerized testing system was developed and utilized to determine JI-R curves and JIc by the partial unloading compliance method according to the ASTM Test for JIc, a Measure of Fracture Toughness (E 813) and the tentative test procedure for determining the plane strain JI-R curve. Based on testing experience with different materials in the temperature range from −196 to > 300°C some problems of the standard procedure concerning, for example, mechanical loading, data evaluation, and validity requirements, are discussed and some alternatives are proposed.
Some Observations on J-R Curves
Authors: Gibson GP , Druce SG
Published: December 2008

The effect of specimen size and geometry on the onset of ductile tearing (Ji, δi) and the initial slope of J(dJ/da) and crack opening displacement dδ/da resistance curves has been investigated for a carbon-manganese steel. The results indicate that in plane sided specimens a thickness in excess of that specified in ASTM Test for JIc, a Measure of Fracture Toughness (E 813) is required to achieve a lower bound, or plane strain, Ji value. However, the resultant decrease in Ji is relatively small. Side-grooving was found to be very effective in promoting plane strain conditions in subsized specimens. The initial tearing resistance was found to be markedly influenced by specimen thickness and degree of side-grooving, and the results indicate that achieving plane strain conditions in the proximity of the crack tip does not ensure a unique J-R curve in side-grooved specimens.

JIc values obtained using ASTM E 813 were found to overestimate the “true” Ji values for a carbon-managanese steel and a pressure vessel steel. This arises from the linear representation of the R curve and the assumed blunting line behavior A power law equation was found to give a statistically better fit to the J-Δa data, particularly in high toughness materials. The need for an engineering or working definition of ductile crack initiation for structural assessment has been acknowledged, and an alternative to the ASTM E 813 procedure suggested, based on the J value at 0.2 mm of crack extension.
J-Integral Values of Steels Tested Under Constant Load
Authors: Fujita T , Kagawa H , Yoshitake A , Urabe N
Published: December 2008

A stable to unstable transition phenomenon of cracking under constant load was studied. The transition phenomenon was mainly caused by initiation and growth of the ductile crack. When this fracture process was examined by means of J-integral resistance (J-R) curves, the ductile crack growth under constant load seemed to agree with the J-R curve that had been determined by the conventional multiple-specimen method. If Jg is defined as the minimum J value that causes the unstable ductile fracture under the constant load, Jg exists between Ji (corresponding to the ductile crack initiation) and Jm (corresponding to the maximum load point in displacement control test). Thus the Jg might be one of the parameters to define the unstable ductile fracture under the constant load condition, though the effect of specimen geometry on Jg is recognized.
Comparison of Potential Drop and Unloading Compliance Methods in Determining Ductile Crack Extension
Authors: Wallin K , Saario T , Auerkari P , Saarelma H , Torronen K
Published: December 2008

Two different methods, the unloading compliance and the AC-potential drop method have been applied simultaneously for crack length measurement during ductile crack extension in J-R curve determinations. The materials used in the comparison of the two test methods were a pressure vessel steel A533B C1.1 (Unified Numbering System [UNI] K12539), a comparable weldment, and a carbon-manganese steel OX522D weld. Specimen geometries used were 25-mm compact tension (ITCT) and 15-mm three-point bend (3PB), respectively.

The two methods applied give consistent results for the amount of crack extension. However, the location of the potential minimum is dependent upon material, specimen geometry, temperature, frequency and current. This leads to the conclusion that the ACPD method fails to indicate the initiation of ductile crack extension correctly. Reasons for this are discussed.
A DC Potential Drop Procedure for Crack Initiation and R-Curve Measurements During Ductile Fracture Tests
Authors: Bakker A
Published: December 2008

This paper describes the use of a direct current (DC) potential drop technique, a single-specimen technique for the detection of crack growth initiation and subsequent crack growth. From an analysis of the potential drop signal, where the measured signal is divided into parts originating from real physical crack growth and fictitious crack growth caused by deformation of the specimen, a procedure is described to derive both crack initiation and crack growth from the test records of a single specimen. This procedure is then applied to a series of three-point bend (SENB) specimens and the results are compared with the multiple-specimen technique according to the ASTM Test for JIc, a Measure of Fracture Toughness (E 813). The agreement between the results of both methods is satisfactory. Finally, some possible refinements and further improvements of the method are discussed.
Ultimate Strength Flexural Theory for Reinforced Brick Masonry
Authors: Matthys JH , Chanprichar B
Published: December 2008

The results of a two-phase experimental research program to develop an ultimate flexural strength theory for reinforced brick masonry is reported. Twenty beam-column specimens and corresponding prisms were tested to determine the flexural compressive stress distribution for high and low strength brick masonry constructed with Type S portland cement lime mortar with loading both parallel and perpendicular to the bed joints. This data established the parameters for defining an ultimate compressive stress block for brick masonry. Reinforced brick masonry beam tests (still in progress) have determined the applicability of the developed theory to reinforced flexural elements. Results show that (1) the ultimate compressive stress-strain relationship for brick masonry under flexural loading and axial loading are different; (2) there is a correlation between the ultimate flexural compressive strain and prism strength; and (3) an ultimate strength theory reasonably predicts the capacity of reinforced brick masonry beams.
Guidelines for Temporary Masonry Wall Support Systems
Authors: Carr RI , Woods RD , Heslip JA
Published: December 2008

Masonry walls are vulnerable to high winds until supported by the completed structure. A common method of temporary support consists of inclined braces restrained at the ground with stakes. Adequate information on the capacity of stakes in this system could not be found in the literature, so research was conducted on the horizontal capacity of stakes in soil. Three stakes were studied: 3.8 by 3.8 cm (2 by 2 in.) and 3.8 by 8.9 cm (2 by 4 in.) wood stakes, and No. 6 reinforcing bars. Each stake was tested at two embedments, 30 cm (12 in.) and 45 cm (18 in.), and at three inclinations to the horizontal, 90°, 60°, and 45°. Stakes were tested in sand, silt, and clay at three consistencies. Loads were applied with a hand-cranked screw mechanism with a proving ring to measure load. Displacement and rotation were measured with two dial gages. A total of 139 tests were performed, and load deflection curves were analyzed at ground level displacements of 3.2 mm (⅛ in.) and 6.4 mm (¼ in.). Equations based on the theory of subgrade reaction for the soils and rigid behavior of the stakes were formulated to match measured data. For most soils, the stake capacity was found to be insufficient to support reasonable lengths of tall masonry walls in a modest wind, 56 km/h (35 mph); consequently, stakes are not recommended as the horizontal support element for tall masonry walls.
Direct Modeling of Concrete Block Masonry Under Axial Compression
Authors: Hamid AA , Abboud BE , Harris HG
Published: December 2008

A better understanding of the complex behavior of masonry structures is necessary to embrace the more appropriate concept of ultimate strength design. Due to the prohibitive cost of full scale testing of masonry systems, a more economical method utilizing direct modeling techniques is proposed. It is the objective of this study to evaluate the use of direct modeling of ungrouted and grouted concrete block masonry under axial compression. A total of 49 quarter-scale block prisms were tested under axial compression. Correlations between model results and available prototype tests are performed. The study includes the effects of mortar strength, grout strength, height-to-thickness ratio, number of courses, and bond type on prism compressive strength. Excellent correlations were obtained for mode of failure and moduli of elasticity. It is concluded that direct modeling is feasible and is capable of predicting the behavior of masonry. Deviations from prototype strength results were observed which are attributed to size effect of aggregate and imperfections in geometry of the model blocks.
Slurry Cutoff Walls: Applications in the Control of Hazardous Wastes
Authors: Ryan CR
Published: December 2008

Slurry cutoff walls are nonstructural barriers constructed to intercept and impede the flow of fluids underground. There are two basic types of slurry cutoff walls, soil-bentonite (SB) and cement-bentonite (CB). Depending on the nature of the project, either method may have some technical or economic advantage over the other. In both cases, a narrow trench is excavated into the ground using a backhoe or other more specialized equipment. The trench is prevented from collapsing by keeping it full at all times with bentonite slurry similar to drilling mud. In the case of SB walls, the trench is subsequently backfilled with a mixture of soil and bentonite slurry that forms the permanent impervious cutoff wall. With the CB method, cement is added to the slurry, which later sets up, forming the permanent seepage barrier.

Slurry cutoff walls are being used in an increasing variety of applications to provide a barrier to the lateral underground flow of various fluids. Principal applications are site dewatering, underground pollution control, and seepage barriers under dams. In this paper, case studies are used to provide examples of recent applications in the control of leaching hazardous wastes.

Projects cited include:

1. Containment of oil seeping through a reservoir abutment.

2. Cleanup of a polychlorinated biphenyl (PCB) contaminated site.

3. Containment of leachates and methane gas migration from a sanitary landfill site.

4. Cleanup of a site with spilled phenols.

All of the examples were selected because of the unusual conditions under which they were constructed or because of the dramatic evidence of results.
Thin Slurry Cutoff Walls Installed by the Vibrated Beam Method
Authors: Leonards GA , Schmednecht F , Chameau J-L , Diamond S
Published: December 2008

In recent years, thin slurry walls installed by vibrating a beam into the ground and injecting a suitable slurry as it is withdrawn have been used successfully and economically in a variety of applications, most notably as (a) permanent seepage cutoffs either in new or existing dams or levees, (b) a means of temporarily controlling groundwater during construction, and (c) a device for containment of toxic wastes.

This paper describes the equipment and construction techniques for installing the cut-off, and details of various types of slurries suitable for different applications are given. The results of field investigations undertaken to assess the permeability and continuity of vertical and battered (inclined) slurry walls are presented.
Evaluation of Two Methods for Constructing Vertical Cutoff Walls at Waste Containment Sites
Authors: Jepsen CP , Place M
Published: December 2008

This paper compares two methods of constructing vertical cutoff walls when considered in the context of controlling the migration of waste materials. It will be argued that the conventional slurry trench method has significant advantages over the vibratory beam injection (VBI) method. The discussion will compare the quality control of each method, relating its importance to the central issue of cutoff wall continuity. Important issues to be discussed in conjunction with quality control considerations include geometry, wall thickness, Darcy's equation, wall composition, and chemical resistance.
Influence of Inorganic Permeants upon the Permeability of Bentonite
Authors: Alther G , Evans JC , Fang H-Y , Witmer K
Published: December 2008

A total of 16 inorganic aqueous solutions were utilized as permeants to determine their effects upon the permeability of both contaminant resistant (polymerized) bentonite and untreated bentonite. It was found that, of the aqueous solutions tested, those with potassium (K+) cations or chloride (Cl−) anions or both induced the largest permeability increases with increasing electrolyte concentration. Conversely, solutions with sodium (Na+) cations or carbonate (CO−3) anions had the least impact upon the permeability of bentonite. It was also observed that doubly charged cations (+2) have a greater initial effect on the permeability than do singly charged cations (+1). Furthermore, a “saturation limit” was in evidence for +2 cations, indicating that beyond certain concentrations the further addition of the soluble salts had only limited additional impact upon the permeability.

For selected bentonite-contaminant combinations, slurry cracking pattern tests were conducted. A correlation between the permeability changes and the results of the cracking pattern tests was demonstrated.

Based upon the findings of this study, it is concluded that the character of the solute anions, as well as the primary cations, affect the permeability of bentonite clays. Further, the Gouy-Chapman model of diffuse double layer was found to be generally consistent with the test data.
Effects of Various Liquids on Clay Soil: Bentonite Slurry Mixtures
Authors: Anderson DC , Crawley W , Zabcik JD
Published: December 2008

Slurry-wall backfill materials were placed in double-ring permeameters to evaluate their permeability to water, xylene, and methanol. Permeability determinations were made using double-ring permeameters because these devices separate flow that occurs near the sidewalls from flow occurring through the central portion of the specimens. The use of double-ring devices appears to overcome some of the limitations of fixed-wall and flexible-wall permeameters. Fixed-wall devices may have sidewall flow, and flexible-wall devices may be inappropriate for testing soft specimens such as a slurry mixture.

Permeability tests on materials that are to contain waste leachates are typically done using water [0.01 N calcium sulfate (CaSO4)] as the permeant liquid. The results of this study show that permeability values determined with water may be misleading. Low permeabilities were obtained with water, but both xylene and methanol caused large permeability increases in the soil-slurry mixtures.
Permeability Testing on Clayey Soil and Silty Sand-Bentonite Mixture Using Acid Liquor
Authors: Gipson AH
Published: December 2008

A laboratory permeability testing program was designed and performed to evaluate the effect of an acid liquor on two alternative materials planned for use in a compacted soil lining to minimize seepage loses from a phosphogypsum storage area. The alternative materials considered for use in the compacted soil lining included (1) on-site natural clayey soils and (2) on-site silty sands mixed with commercial bentonite (Volclay saline seal, No. 100). The acid liquor has a pH of 2.2 and is high in calcium, calcium oxides, sodium, chloride, and sulphate. The test results indicated that the acid liquor permeant resulted in lower permeabilities of the clayey soils than with tap water permeant. The tests on the commercial bentonite-silty sand mixtures with acid liquor permeant indicated that the permeability increased with time.
Procedure and Equipment Factors Affecting Permeability Testing of a Bentonite-Sand Liner Material
Authors: Edil TB , Erickson AE
Published: December 2008

This paper presents the findings of an investigation regarding the effects of procedural and equipmental factors on the laboratory measurement of permeability of a bentonite-sand liner. In the experimental program, permeability tests were performed on compacted specimens of a bentonite-sand mixture to study the effect of (1) permeameter type (rigid- versus flexible-wall permeameters), (2) back pressure application, and (3) hydraulic gradient magnitude on the measured permeabilities. The liner material used in the tests was a mixture of 90% P20–R30 Ottawa sand and 10% bentonite clay. Water was used to prepare the specimens and as the permeant. Specimens were prepared by compaction at moisture contents exceeding optimum using the standard proctor method. A pressure of 380 kPa was used in the tests involving back pressure. The low and high hydraulic gradients used were nominally 29 and 290, respectively. Prior to the termination of a test, a red indicator was passed through the permeameters under the high gradient. The specimens were dissected and inspected after the test for the identification of flow areas and channels.

The test results indicated that specimens continue to hydrate during permeation. Unless wetter specimens are used, this continuing hydration interferes with the inflow-outflow balance, depriving the tester of an important check for leaks. Differential hydration throughout the specimen results in different soil structures and zones of flow. For instance, most of the flow may take place in an annular area surrounding a less hydrated core in the center. Since the total cross-sectional area is used in computing the coefficient of permeability, the values may be underestimated. Back pressure, often used to enhance saturation during testing, appears to have a detrimental effect when applied in the rigid-wall permeameters by increasing the potential for formation of channels and side flow. Test results are affected by hydraulic gradient in different ways depending on the type of permeameter. While gradients as high as 360 did not induce piping in the gap-graded liner material tested, the application of very high gradients to accelerate testing is not desirable for a number of other effects observed.
The Effect of Organic Fluids on the Pore Size Distribution of Compacted Kaolinite
Authors: Acar YB , Olivieri I , Field SD
Published: December 2008

This paper determines that permeating organic fluids through compacted kaolinite does not significantly change the distribution of different pore sizes. The mercury intrusion method was used to quantify the pore size and frequency distribution of specimens before and after permeation with nitrobenzene, acetone, phenol, and benzene. Porosity quantification parameters obtained from available hydraulic conductivity models were then correlated with experimental values of absolute permeability. Acetone and phenol resulted in changes of absolute hydraulic conductivity within one order of magnitude, that of 0.01 N calcium sulfate (CaSO4) solution, while benzene and nitrobenzene led to a decrease of two orders of magnitude. Mercury intrusion tests on all specimens indicated that the size and distribution of pores within the 0.008 to 10 μm range were not significantly changed. The conclusion is that changes in hydraulic conductivity of compacted kaolinite are not due to a redistribution of pore sizes due to changes in forces of interaction. The results suggest that the decrease in hydraulic conductivity with benzene and nitrobenzene are due to the low solubility of these chemicals in water.
The Design and Testing of a Compacted Clay Barrier Layer to Limit Percolation Through Landfill Covers
Authors: Mundell JA , Bailey B
Published: December 2008

The design and testing of a compacted clay barrier layer to restrict vertical percolation through landfill covers is discussed. General relationships between compaction water content, dry unit weight, and permeability related to changes in soil fabric due to varying compaction conditions are reviewed. Laboratory testing programs to evaluate the degree of imperviousness capable of being achieved in the field for a given soil type are outlined, and a case study of the design and testing of a compacted clay barrier over a landfill is presented. Based on the results of the laboratory testing program prior to construction, it was determined that a design permeability of from 1 to 5 × 10−8 cm/s could be achieved by controlling the minimum dry unit weight to greater than 95% of the standard Proctor dry density and the compaction water content to greater than 1% wet of the line of optimums. Results of laboratory permeability testing on undisturbed ring and block samples taken from the landfill barrier layer indicated that an average permeability of 2 × 10−8 cm/s had been achieved.
Permeability of Fly Ash and Fly Ash-Sand Mixtures
Authors: Vesperman KD , Edil TB , Berthouex PM
Published: December 2008

In an experimental program aimed at evaluating the potential of fly ash for use in liners, permeability tests were performed on two pozzolanic fly ashes from western U.S. coal sources compacted at varying densities and mixed in varying percentages with a quartz sand. Permeability testing was performed in a falling head, flexible membrane, triaxial cell permeameter. A back pressure of 380 kPa and a hydraulic gradient of 10 to 20 were applied to the permeability specimens.

The two pozzolanic fly ashes exhibit different degrees of “self-cementation,” which causes a dramatic influence on the resulting permeability values. The highly self-cementing fly ash exhibits nearly a full three orders of magnitude lower permeability than the less self-cementing fly ash. Increasing density, while not as important as the coal source, decreases permeability in both types of fly ash on the order of about half a magnitude. Moisture content is also an important factor since it controls the extent of cementation as well as compaction density. Increasing percentages of fly ash in the mixtures decreases the permeability up to a limiting value when the volume of fly ash and water added exceeds the available pore space between the sand grains; for instance, the mixture of 40% self-cementing fly ash and 60% sand exhibits essentially the same permeability as the 100% fly ash specimen.

The study indicates that the addition of pozzolanic fly ash to an otherwise highly permeable soil results in a dramatic reduction in permeability. The “self-cementing” fly ash exhibits 103 to 104 folds of permeability reduction with final permeabilities of less than 10−6 mm/s and seems quite suitable for liner applications.
Root-Mean-Square Vertical Acceleration as a Summary Roughness Statistic
Authors: Hudson WR , Halbach D , Zaniewski JP , Moser L
Published: December 2008

Much has been done in recent years to relate various roughness statistics to rider comfort in terms of a serviceability index (developed by Carey and Irick). Much less has been done on correct evaluation of a true profile in terms of summary statistics for field comparison of vehicle operating costs and user comfort. Important work in this area has been done by Gillespie and Sayers at the University of Michigan, and additional work has been done by Hudson, Williamson, and McKenzie at the University of Texas. Work has also been done in Brazil by Queiroz and others. At least two statistics have been offered for summarizing roughness information:

(a) the average rectified velocity, by Gillespie and Sayers, and

(b) the root-mean-square vertical acceleration, by Hudson et al.

The purpose of this paper is to examine and compare these statistics with particular emphasis on their potential effects on rider comfort and their use as standard calibration statistics for response-type road roughness meters.

A complete parameter study is reported comparing these two statistics. The results of the study will be helpful in selecting useful analytical techniques for routine applications.
Development, Implementation, and Application of the Reference Quarter-Car Simulation
Authors: Sayers M
Published: December 2008

An analysis of longitudinal road profile called the reference quarter-car simulation (RQCS), described in National Cooperative Highway Research Program (NCHRP) Report 228, has been applied in a number of research projects and was recently selected as the basis for an international roughness index to be used in World Bank projects. Calibration guidelines are provided for agencies without profilometers so that they can calibrate response-type road roughness measuring systems to the reference. Relationships are shown between the RQCS and subjective panel ratings, dynamic pavement loading from heavy trucks, and the ride quality of passenger cars and heavy trucks. The RQCS is compared and contrasted with alternative summary roughness statistics also used to process profiles. Potential future developments in analyzing longitudinal profiles are discussed, in light of the present trend away from response-type systems and towards profile-measuring instruments for determining road roughness.
Simulation of Road Meters by Separate Analysis of Accelerometer and Height Sensor Data
Authors: Watugala GK , Hayhoe GF
Published: December 2008

A procedure is described for obtaining road meter roughness index measurements directly from profilometer transducer outputs, eliminating the intermediate step of double integrating the profilometer accelerometer signals. (Double integration of accelerometer signals is the major data processing task of inertial profilometers.) Simulation of a linear car model is performed with two separate sets of equations of motion. The first set of equations, which accepts height sensor data, is identical in form to the equations used in simulations where the pavement profile is the input data. The second set is a transformation of the first, arranged to accept accelerometer data. Vehicle responses to the two components of pavement profile are added together and the roughness index is then calculated in the normal way. In the case of road meters that use relative displacement (or velocity) to calculate the roughness index, the two sets of equations can be combined into one set with the input changed to a combination of height sensor and accelerometer signals. The procedure is tested using sinusoidal and random signals that correspond to various elevation profile curves. A comparison is also made with results from the normal procedure of using the elevation profile for the simulation. Results from the testing confirm that the proposed procedure is valid and that explicit computation of the elevation profile is not necessary when the roughness index is measured with a profilometer.
Aquatic Macrophyton Field Collection Methods and Laboratory Analyses
Authors: Raschke RL , Rusanowski PC
Published: December 2008

Field sampling methodology ranging from regional surveys to meristic measurements are presented for use by applied biologists faced with problems of measuring macrophyte response to environmental changes. A discussion of sampling gear recommended for use with the quadrat method is included. Treatment of plants for the purpose of identification and weight analysis is addressed, especially the problem of treating carbonate encrustations.
First-Order Error Analysis for Aquatic Plant Production Estimates
Authors: Carpenter SR
Published: December 2008

Variance estimates are rarely reported or rigorously determined for net primary production by higher aquatic plants, yet the variance must be known before production estimates can be compared conclusively. First-order error analysis is used here to derive formulae for estimating the variance of annual net production determined by demographic methods. Demographic methods determine net production of even-aged cohorts by analyzing curves of survivorship versus plant mass (Allen curves). Allen curves may be interpolated linearly or logarithmically. Calculation formulae for both alternatives are derived and compared in a common framework. Logarithmic interpolation is more consistent with observed thinning dynamics of even-aged plant stands.
The Osborne Submersed Aquatic Plant Sampler for Obtaining Biomass Measurements
Authors: Osborne JA
Published: December 2008

The Osborne submersed aquatic plant sampler was designed to obtain biomass samples from the water column and sediment of lakes and streams. The sampler, which is operated by winch and cable from a apontoon boat, is easily operated to obtain a sufficient number of samples within a limited time frame (one day) for applying statistical methods. Mean biomass estimates (kilograms per metre squared), percent frequency of occurrence, seasonal biomass trends, and seasonal or annual mean biomass distribution of submersed aquatic vegetation can be calculated from data collected with the sampler. The sampler has been used in aquatic plant studies to determine the distribution, ecology, and effect of control methodologies for submersed plant species. Several study lakes may be visited per sampling day because of the ease of transporting the sampler.
Relationships Between Aquatic Macrophytes and the Chemical and Physical Composition of the Substrate in Kahle Lake, Clarion-Venango Counties, Pennsylvania
Authors: McKenna KA
Published: December 2008

Excessive growth of Najas flexilis in Kahle Lake creates a threat to the natural aging process of the eight year old impoundment. An overwinter drawdown was performed in 1977, but was ineffective in controlling N. flexilis. The intent of this research was to investigate edaphic factors that may influence aquatic macrophyte establishment and abundance within the littoral zone of Kahle Lake.

Sampling areas were selected such that three sites were established in locations of abundant plant cover and three sites in locations of minimal plant growth. The variables measured included substrate particle size fractions, percentage organic matter, exchangeable cations, and aquatic macrophyte standing crop. Knowledge of significant habitat characteristics is pertinent to the application of control techniques designed to minimize plant infestation.

Plant and substrate samples were processed and data analyzed to determine variations between sampling sites. Nonparametric testing showed that mean percent gravel differed significantly between areas of abundant and minimal plant growth. Mean percent organic matter within the substrate did not differ among sites. Correlation analysis indicated that aquatic macrophyte standing crop and percent fine sand were significantly associated.
Mapping—Surface or Ground Surveys
Authors: Raschke RL
Published: December 2008

Preparation of vegetation maps from ground surveys as the first step in a field study is discussed. Depending upon the degree of accuracy required, various types of equipment are suggested for use in a mapping survey. Details are presented on station or point selections with a discussion of procedures and calculation of angles and distances using an illustrated example. Additional information is presented about kinds of information, explanatory material, and symbols used in constructing vegetation maps.
Realism and Replicability of Lentic Freshwater Microcosms
Authors: Levy D , Lockett G , Oldfather J , Rees J , Saegebarth E , Schneider R , Harte J
Published: December 2008

Microcosms designed to simulate the pelagic epilimnion of a lentic freshwater body were compared with the natural system from which they were derived. Emphasis was placed on determining the influence of water agitation on microcosm realism and replicability. In two experiments, excellent tracking of the natural system for 4 to 6 weeks and excellent replication among microcosms was observed; the dominant phytoplankton and zooplankton taxa in the microcosms were not statistically distinguishable from those measured in the natural systems. In a third experiment, the dominant taxa in the 50-L microscosms could be statistically distinguished from the variables in the natural system. In all three experiments, correlations between the taxonomic variables and the chemical variables, when present in the natural system, were observed in the microcosms.
Comparison of Laboratory Microcosms and Field Responses to Copper
Authors: Harrass MC , Taub FB
Published: December 2008

As a biological model, a Standardized Aquatic Microcosm has demonstrated trophic interactions and community recovery after pesticide treatment. Daphnia magna were temporarily eliminated by treatment with 0.5 mg/L copper, leading to changes in algal and rotifer densities. Algae were severely affected by treatment with 2.0 mg/L copper, demonstrating altered dominance and productivity. Recovery of treated communities after inactivation or isolation of active toxicant was demonstrated by populations attaining densities equivalent to control communities. Comparison with published studies of natural communities treated with copper indicates that similar trophic interactions have often been demonstrated, although field studies suggested that responses are quite variable.
Experimental Ponds for Evaluating Bioassay Predictions
Authors: deNoyelles F , Kettle WD
Published: December 2008

Experimental pond studies were used to demonstrate a means of assessing the accuracy of laboratory and in situ bioassays predicting the effects of chemical stress on phytoplankton. A short-term batch bioassay using changing carbon uptake in photosynthesis predicted an immediate (first 24 h) effect of the herbicide atrazine on the phytoplankton communities in experimental ponds. After addition of atrazine to the ponds, the same decreases in carbon uptake were observed, but the appearance of resistant species that soon occurred could not be predicted with the short-term exposure used in such a bioassay. From another experimental pond study a longer-term continuous flow bioassay using changing species composition predicted an effect of increased nutrient and altered pH conditions over a 20-day exposure. With these same perturbations applied to experimental ponds, the same series of responses were observed. Comparison of responses in the experimental ponds with those in the bioassays was also used to demonstrate the general limits of applicability for each bioassay.
A Framework for the Complementary Use of Mathematical Models and Microcosms in Environmental Assessment
Authors: Porcella DB , Chen CW , Kawaratani RK , Harte J , Levy D , Rees J , Lockett G
Published: December 2008

A framework was developed for the complementary use of mathematical models and microcosms in environmental assessment. A part of the framework was the use of microcosm data to define important ecological processes, including the mathematical functions and their rate coefficients, for inclusion in the mathematical model. As a case study, a mathematical model developed previously for the ecological assessment of power plant impacts was adapted to simulate the experimental conditions of a microcosm. Results indicated that ammonium absorption from the air was an important process for the microcosms but was not included in the simulation model. In most environmental situations, this is not an important process for simulation. The rate coefficients, compiled from the literature and used in the model to date, were generally applicable to the microcosms. Use of the mathematical model to anticipate results of microcosm experiments can help optimize the sample collection and analysis program necessary to meet the experimental design.