bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bioavailability of Trace Metals in Natural Waters
Authors: O'Donnel JR , Kaplan BM , Allen HE 
Published: December 2008

Current data on the toxicity of metals to aquatic organisms show effect levels over many orders of magnitude of total metal concentrations. Thus it appears that the bioavailability of metals is not related to this parameter. Only a fraction of the metal present is related to the amount “seen” by the organism. From solution, toxicity is a function of the concentration of the free metal ion and some hydrolyzed species. From sediments, metal availability is not well understood, although recent work has indicated that metal bound in specific sediment compartments or phases may be the toxic form.
Bioavailability can be predicted from knowledge of the speciation of metal in an aqueous system. Currently, two approaches are used to study speciation in solution and sediment: fractionation and titration.
This paper examines the relation between water quality and the availability of metals to organisms. The chemistry and measurement of metal species should be used as the basis for reviewing bioassay results. Further research needs to be conducted to elucidate the portion of sediment-bound metal which is bioavailable. Problems in the interpretation of bioassay results for natural waters arise from the addition of metal in excess of the capacity of organic ligands for complexation and in not allowing reactions to attain equilibrium.
Use of Statistical Information to Improve Compatibility Between the Various Components of the Water Quality Based Approach
Authors: Jaworski NA , Mount DI 
Published: December 2008

During the past two decades, implementation procedures in wastewater management often resulted in a large margin of safety being incorporated into the use of water quality criteria for the protection of aquatic life and its uses. Wasteload allocation design conditions, such as the use of seven-day, ten-year low flow, gave assurances of instream concentrations well below the water quality criteria a large percentage of time. Present-day economic conditions and the increasing cost of advanced wastewater treatment are necessitating a re-examination of how water quality criteria are being used in the water quality based approach for establishing effluent limitations.
The relationships between water quality criteria and other components of the water quality based approach are identified. The need for a better defined and more consistent use of statistical information is suggested not only in the development of water quality criteria but also for the entire water quality based approach. Intensity, duration, and frequency of occurrence (return period) appear to be three common statistical parameters of the six-step water quality based approach. Research is identified which, if successful, would allow water quality managers better insight in determining pollutant exposures that more adequately simulate receiving water conditions resulting from variable stream flows, wastewater discharge rates, and pollutant concentrations.
Analysis of Interlaminar Stresses in Thick Composite Laminates With and Without Edge Delamination
Authors: Whitcomb JD , Raju IS 
Published: December 2008

The effect of laminate thickness on the interlaminar stresses in rectangular quasi-isotropic laminates under uniform axial strain was studied. Laminates from 8-ply to infinitely thick were analyzed. Thick laminates were synthesized by stacking (45/0/−45/90) ply groups, rather than grouping like plies. Laminates with and without delaminations were studied.
In laminates without delaminations, the free-edge interlaminar normal stress distribution in the outer ply groups was insensitive to total laminate thickness. The interlaminar normal stress distribution for the interior ply groups was nearly the same as for an infinitely thick laminate. In contrast, the free-edge interlaminar shear stress distribution was nearly the same for inner and outer ply groups and was insensitive to laminate thickness. In laminates with delaminations, those delaminations near the top and bottom surfaces of a thick laminate have much larger total strain-energy-release rates (GT) and Mode I-to-total (GI/GT) ratios than delaminations deep in the interior. Therefore delaminations can be expected to grow more easily near the surfaces of a laminate than in the interior. This is consistent with experimental results reported in the literature. Also, near surface delaminations in thin laminates tend to have larger strain-energy release rates than corresponding near surface delaminations in thick laminates.
Delamination Growth in a Notched Graphite/Epoxy Laminate Under Compression Fatigue Loading
Authors: Mohlin T , Blom AF , Carlsson LA , Gustavsson AI 
Published: December 2008

This paper is concerned with the propagation of delamination in a graphite/epoxy composite laminate with an unloaded circular hole subjected to compression fatigue loading. Experimental and theoretical aspects of the problem are investigated.
In the experimental phase, coupon specimens were fatigue loaded in pure compression. The tests were performed at different constant-load amplitudes in ambient and humid environments at room temperature.
To monitor delamination growth, the specimens were removed from the testing machine after certain numbers of load cycles and were nondestructively inspected using a tetrabromoethane (TBE)-enhanced X-ray technique. In this way a measure of the delamination shape and area as a function of applied load level and number of cycles was obtained. Fatigue damage in terms of modulus degradation was also monitored. In the case of specimens which suffered severe damage, the residual compression strength was measured.
A three-dimensional finite-element analysis was used in conjunction with the experimental results to characterize the delamination crack growth in dry specimens. Results of this analysis enabled a power-law relationship between the strain energy release rate and the crack growth rate to be established.
Fatigue Thresholds of Delamination Crack Growth in Orthotropic Graphite/Epoxy Laminates
Authors: Gustafson C-G , Jilkèn L , Gradin PA 
Published: December 2008

During manufacturing of fiber composite structures, cracks of small sizes are introduced during layup and drilling, and in the making of cutouts. The component itself sometimes has sites that are prone to delaminations, such as the junction of the web and the flange of a beam. Under cyclic loading these interlaminar defects can grow.
One key for designing fiber composite structures that will not exhibit delamination crack growth is to make sure that the actual or anticipated interlaminar flaws produce strain-energy release rates below the fatigue threshold value Gth for the actual laminate and actual combination of opening mode and shearing mode energy release rates, GI and GII, respectively.
Four types of delamination crack growth experiments were carried out to experimentally determine the critical curve inside which no cyclic crack growth will take place in the GI and GII planes. Pure Mode I crack growth and near pure forward shearing mode crack growth experiments were performed, as were experiments that possess a combination of the first two modes of crack growth. The laminates used in this investigation were (0/90), T300/914C layups. In the experimental work a unique automatic load reduction system was used, allowing for the determination of the threshold state with a constant stress ratio maintained during the load reduction.
For all but one case, GIth and GIIth were determined numerically, using a two-dimensional finite-element method program, by employing a relaxation procedure. Finally, the results from the experiments are presented in the GIth and GIIth planes.
Role of Delamination and Damage Development on the Strength of Thick Notched Laminates
Authors: Harris CE , Morris DH 
Published: December 2008

A large, comprehensive program is being conducted at Virginia Tech to study the effect of laminate thickness on the fracture strength of notched laminated composites. Part of this program has been the study of the characteristics and development of subcritical crack-tip damage prior to failure. The study has concentrated on the centercracked tension specimen geometry. Subcritical crack-tip damage has been studied using enhanced X-ray radiography and the laminate deply technique.
This paper examines the role that delamination plays in affecting the fracture of [0/±45/90]ns and [0/±45]ns laminates at various values of n. The study has found that delaminations do occur in thin laminates (n = 1) and affect the strength of the laminate. However, in thick laminates such as [0/±45/90]15s and [0/±45]20s, there is sufficient constraint to prevent delaminations from occurring in the interior region of the specimen. The final fracture surface is uniform in the interior and self-similar (collinear with the original starter notch), with “shear-lip” type damage in the form of delaminations and matrix cracking in the first several plies at the surface. These differences in the type of fracture of the thin and thick laminates greatly affect the fracture strength.
Effects of Sustained Shear Stresses on the Cyclic Degradation of Clay
Authors: Goulois AM , Whitman RV , Hoeg K 
Published: December 2008

The soils surrounding any of the anchorage piles of a tension leg platform (TLP) will be subjected to average (sustained) shear stresses τave of significant magnitude, in addition to the cyclic shear stresses τc associated with fluctuations of environmental loading. In order to investigate their combined effect on the displacement behavior of such a foundation, ten cyclic direct simple shear (DSS) tests were run with constant values of both τave and τc, as were two tests with variable τc. All the conditions of the 1975 Norwegian Geotechnical Institute (NGI) program (Andersen 1976 and Andersen et al, 1980) were followed (Plastic Drammen Clay, Geonor DSS device, and so forth) in order to capitalize upon, and increase, that data base.
The results of the investigation are presented in the form of “three-dimensional strain contour diagrams,” which improve our ability to interpolate, and even extrapolate, the data over a wide range of stress conditions. Furthermore, a procedure is proposed that permits a satisfactory estimation of the clay behavior under the variable cyclic loading imposed.
Integrated Testing and Properties of a Gulf of Mexico Clay
Authors: Saada AS , Macky TA 
Published: December 2008

In testing undisturbed soil samples taken in a hostile environment one is often faced with the problem of having to obtain many properties from a limited number of specimens. This difficulty can be partly overcome by designing compatible equipment, so that a sample can be tested in a nondestructive way at very small strains in one type of machine, then transferred to another one and subjected to larger static and dynamic stresses and strains. In this investigation, the specimens were first placed under fast cyclic loading axially and torsionally in the resonant column cell. Then they were transferred with their caps in place to another cell where they were subjected to slower cyclic loading under increasingly larger stress amplitudes. The results of the tests that were conducted on a Gulf of Mexico clay are given and analyzed. Shear moduli, damping ratios, and frequency responses obtained in a resonant column at very small strains are examined together with ratios obtained at large strains to give a complete picture of the dynamic behavior of this clay.
Data discussed in the light of the Ramberg-Osgood-Masing criterion show that such a criterion overestimates the damping and that it is impossible to describe the behavior of this clay over the whole spectrum of strain with just one set of parameters. It is recommended that parameters in the zone of interest always be obtained.
Response of Silts to Wave Loads: Experimental Study
Authors: Clukey EC , Kulhawy FH , Liu PL-F 
Published: December 2008

The response of a nonplastic silt subjected to water waves was investigated in a laboratory wave tank facility. The deposit was created by slurrying the silt into a sediment bay, and pore-water pressure transducers were placed at various depths within the deposit to measure the dynamic response under wave loading.
Tests were run under varying hydrodynamic conditions. At higher wave heights, the pore-water pressures rose continuously and resulted in liquefaction of the silt. Intermediate wave heights caused observable deformations, while low wave heights generated positive pore-water pressures that appeared to reach steady state nonfailure conditions in a few minutes.
The results from the testing suggest that normally consolidated silty marine sediments at low overburden stresses can liquefy at substantially lower cyclic stress ratios than currently available data for sands would indicate. This observation suggests further that utilization of data for sands could lead to unrealistic design practices in offshore regions of silty material.
The Use of the Point Load Index in Weak Carbonate Rocks
Authors: Abbs AF 
Published: December 2008

There has been increasing use of the point load index as a measure of rock strength since its introduction in 1972. The test results have been correlated to in the uniaxial compressive strength σf of the rock. The correlations between the rates of point load index Is and the uniaxial strength σf for conventional strong rocks are σf/Is = 16 to 24. The small size of the equipment and the simplicity of the test have led to its use on site on many offshore projects.
Recent experience with weak porous carbonate rocks from offshore areas of the Middle East have proven that the relationship for these materials is much closer to σf/Is = 3.7 with actual field correlations varying from 2.7 to 8.8. Moreover, statistical studies of a large number of point load test data show that this test is poorly suited to weak carbonate rocks.
Comparison of Analytical Methods for the Determination of Total and Free Cyanide in Solid Waste
Authors: Barsotti LR , Palmer TA 
Published: December 2008

Historically, standard reflux distillation methods have been used to determine the total cyanide in aqueous systems. This paper compares such a method with an automated total cyanide method and demonstrates good recovery and precision by both methods. The automated method has the advantages of speed and convenience, as well as being less labor-intensive.
Free cyanide, identified as the sum of hydrocyanic acid and cyanide ion in aqueous solution, is determined by a microdiffusion and a modified Roberts-Jackson method. A comparison of results obtained by both methods showed free cyanide was only about 2% of the total cyanide in an aqueous sample. Total cyanide methods are useful for screening the cyanide content of samples, but free cyanide methods increase the information available and improve the understanding about the kinds of cyanide compounds in a sample. Even greater selectivity of analytical methods for cyanide compounds in waste is desirable and a challenge to analytical chemists.
A Toxicity Reduction Test System to Assist in Predicting Land Treatability of Hazardous Organic Wastes
Authors: Matthews JE , Bulich AA 
Published: December 2008

Migration of toxic organics contained in the water-soluble fraction (WSF) of land-applied hazardous wastes poses the most serious threat to groundwater resources. Wastes containing toxic organics that are potentially leachable must be applied to the land at a rate that will allow attenuation of such constituents before their migration from the treatment zone can occur.
A toxicity reduction (TR) test system is being proposed that will serve to determine whether and to what extent attenuation of WSF organic constituents, including both parent compounds and intermediate transformation products, will occur in a well-managed land treatment system.
The test system employs reduction of acute toxicity exerted by WSF organics over time as the measurement criteria. Four sample sets of selected waste-soil combinations are prepared in duplicate for extraction with deionized water (DW) at 14-day intervals during a 42-day experimental period. Acute toxicity of each DW extract is determined by using a bacterial bioluminescence assay. Dose-response curves for each loading rate and subsequent time interval are compared with those of previous sample sets. The waste is predicted to be a candidate for land treatment if a significant reduction of acute toxicity exists during the experiment period at any of the loading rates tested. The maximum acceptable initial loading rate (MAIL) for waste application is predicted from these data. The predicted MAIL rate is the highest rate tested in which toxicity reduction for the waste-soil DW extract progresses steadily during the experimental period with the Day-42 EC50 approaching or exceeding 100 percent. (The EC50 is defined as the effective concentration of the DW extract that causes a 50% decrease in bacterial light output.) The higher the EC50 the lower the toxic effect; therefore, a 42-day EC50 approaching 100% signifies toxicity reduction in a waste-soil DW extract.
The TR procedure currently is being used by the EPA's Hazardous Waste Land Treatment Research Program to assist in evaluating land treatability potential for a variety of organic hazardous wastes. The most extensive use of the procedure to date has involved evaluation of land treatability for oily wastes from different sources within a refinery: i.e., lagoon bottom sludge, API separator sludge, slop oil emulsion solids, and dissolved air flotation unit skimmings. Additional evaluation tests have been conducted by using wastes from the wood preserving and paint industries. Results from these evaluation tests indicate the potential usefulness of the TR procedure as one of the initial tests conducted in a laboratory screening test sequence for predicting the land treatability potential of organic hazardous wastes.
Spatial Variation of Characteristics in the Zone of Incorporation at an Industrial Waste Land Treatment Site
Authors: Loehr RC , Martin JH , Neuhauser EF 
Published: December 2008

The spatial variation in the characteristics of the zone of incorporation (ZOI) at an industrial waste land treatment site can be significant even when efforts are taken to achieve uniform distribution and incorporation. A single grab sample can be inappropriate for determining average ZOI characteristics.
The results of this study provide guidance in determining the number of samples necessary to provide reliable estimates of ZOI characteristics. The spatial variation at land treatment sites is a function of site-specific factors such as soil characteristics and methods of waste application and incorporation. A determination of specific site spatial variation is recommended as a prerequisite for developing an appropriate sampling program at land treatment sites.
Lateral-Load Tests on 25.4-mm (1-in.) Diameter Piles in Very Soft Clay in Side-by-Side and In-Line Groups
Authors: Cox WR , Dixon DA , Murphy BS 
Published: December 2008

Studies were made to investigate efficiencies of pile groups under lateral loading. The loading was in one direction at slow displacement rates approaching static conditions. The test piles were 25.4-mm (1-in.) diameter tubes open-ended, with penetrations of two, four, six, or eight diameters. Tests were made on single piles and on three- and five-pile groups with clear spacings of 0.5, 1, 2, 3, and 5 diameters in side-by-side or in-line arrangements. The tests were run in a very soft clay with a moisture content of 59% and a shear strength of 2 kPa (42 psf).
Summaries are given of efficiencies of 20 combinations of pile numbers, penetrations, arrangements, and clear spacings. Efficiencies are given for individual piles in a pile group as well as for the entire group. Distances from the soil surface to the load resultant on individual piles and to the load resultant on the total group are also given.
Suggested Procedure for Conducting Dynamic Lateral-Load Tests on Piles
Authors: Gle DR , Woods RD 
Published: December 2008

There are several analytical procedures available to predict the soil-pile interaction parameters required for the analysis of a pile-supported foundation subjected to vibratory forces. A procedure for performing a dynamic lateral field test on a single pile is presented. Results of this test are used to verify the adequacy of the assumptions made for the analytic solution and to judge the appropriateness of the soil-pile interaction parameters.
Dynamic lateral-load tests were conducted on eleven steel-pipe piles at three sites in southeastern Michigan. The piles were 324 and 356 mm (12.75 and 14 in.) in diameter, had lengths from 15 to 49 m (50 to 160 ft) long, and were embedded in both cohesive and cohesionless soils. The procedure consisted of attaching a steel-plate mass, vibratory oscillator, and vibration monitoring instrumentation to the head of each pile. The oscillator was then used to drive the soil-pile-mass system at selected force levels through frequencies from 5 to 55 Hz. The dynamic response was recorded on a strip-chart recorder for later evaluation. The data are presented in figures showing frequency versus response amplitude for each oscillator force level.
The soil-pile-mass system was also set into free vibration using the plucking technique. Results of the steady-state vibration testing are compared with the plucking test results on the same pile.
Conventional soil boring and testing methods were used to determine the subsurface soil profile and static soil properties. Dynamic soil properties adjacent to the tested piles were determined using the seismic cross hole and SH refraction (horizontal polarization of the shear wave) techniques.
Because of the way piles are inserted into the soil, the assumed boundary conditions between the soil and pile used in the analytical solutions seldom match the field conditions. This dynamic testing procedure enables the geotechnical engineer to make a judgment as to the adequacy of the assumptions in the analytical model and to make suitable corrections to match the field-observed results.