bluuebunny/crossref_metadata_2025 huggingface dataset:
RCRA Laboratory Certification
Authors: Hirst RR , Stainken DM , Fischer RL , Stauber KL
Published: February 2009

The Office of Quality Assurance (OQA) within the New Jersey Department of Environmental Protection develops laboratory standards for the Department's Safe Drinking Water and NPDES (NJPDES) programs, and administers a laboratory certification program. The existing certification program was first promulgated for drinking water in 1977. Certification for water and wastewater was offered beginning in 1981. The USEPA Region II RCRA staff incorporated a work output in the FY 1986 USEPA/NJDEP RCRA Interagency Agreement which requires the Department to begin evaluating compliance and performance of analytical laboratories which report measurement data to the Agency and the Department with respect to the RCRA program. OQA made a decision to develop a laboratory certification program for waste analyses (RCRA) and to incorporate such a program into its current regulations.

The RCRA laboratory certification program, as it is currently proposed, would provide laboratories with certification in four major categories: waste characterization, inorganics, organics, and miscellaneous analyses. Laboratories will be certified by individual parameter or analysis under the categories of waste characterization, inorganics (AAS), and miscellaneous analyses. For organics analyses, laboratories will be certified for entire analytical methods rather than by individual analytes (for example, a laboratory will be certified for all parameters covered under SW-846 Method 8240 rather than by each individual analyte listed in the method). Laboratories will be requested at the time they apply for certification to designate which matrices (aqueous and/or nonaqueous) will be analyzed under their RCRA certification. The program will require, along with NJDEP's RCRA regulations, that all laboratories which submit RCRA compliance data to the Department must be certified for the applicable parameters or methods.

The new regulations will cover administrative procedures for the program, such as annual fees for certification, laboratory personnel qualifications, proficiency evaluation, on-site inspections, and enforcement. Many new administrative proposals are incorporated into the proposed regulations, including a more efficient enforcement procedure which will apply to drinking water, water/wastewater, and waste analysis certifications.

Development of the waste analysis certification program has also raised many other issues which are under review at OQA, such as development of performance evaluation samples, analytical method development and validation, method equivalency procedures, and, in the long term, establishment of laboratory performance standards and uniform quality control procedures.
Comparative Study of Preparative and Analytical Techniques for the Determination of Selenium in Water, Sediment, and Vegetation Matrices
Authors: Iskander MS , Yacoub NL , Holden AM , Smith CB , Stephens RD
Published: February 2009

In an effort to evaluate the currently available methodologies for the determination of selenium (Se) (a potentially toxic and difficult-to-measure element) in various sample matrices, different approaches to sample preparation and analysis were considered. Modification of existing methods was applied when needed and modified methodologies were assessed.

Nitric acid digestion, with and without hydrogen peroxide (H2O2) and hydrochloric acid (HCl), was considered. Total selenium in various digestates was determined by inductively coupled plasma-atomic emission spectroscopy (ICP-AES), heated graphite atomizer-atomic absorption (HGA-AA), and hydride generation-atomic absorption (HG-AA) spectrometry.

The data generated by this work showed that there is a reasonable agreement between the Se results obtained by ICP-AES and HGA-AA in the sediment and vegetation samples. The HGA-AA technique, however, is preferred for the determination of low levels of Se in water (sub ppm) due to its higher sensitivity relative to that of ICP-AES.

Several problems were encountered with the hydride generation technique (HG-AA), and its use required difficult manipulations and extreme care. Generally, Se recoveries of 77 to 108% were attained at levels of 2 and 30 ppm total Se.

This paper describes the various methods of sample preparation considered and the operating parameters of the different instrumental techniques used. A comparative discussion of these methods and techniques is also reported along with conclusions pertinent to the use of each.
Impacts and Interface of CERCLA Monitoring Requirements with Other State and Federal Programs
Authors: Stauber KL , Stainken DM , Fischer RL , Hirst RR
Published: February 2009

The New Jersey Department of Environmental Protection is responsible for implementing environmental policy and administering a regulatory structure in accordance with federal and state statutes. The Department's quality assurance program provides a mechanism which enables the Department to administer programs based on reliable monitoring and analytical data. The QA program uses several elements to control QA activities in administering the federal/state NPDES (National Pollutant Discharge Elimination System), Safe Drinking Water Act (SDWA), and RCRA (Resource Conservation and Recovery Act) programs. These elements include the use of a state laboratory certification program, specialized QA permit requirements, use of QA project plans, use of laboratory and field audits, and performance evaluation (PE) samples.
Development of a Portable Testing Procedure for Monitoring Halogenated Solvents in Waste Fuels
Authors: Tarrer AR , Perry JG , Holloway WM
Published: February 2009

In the past, used oil has provided a valuable energy source in its use as a fuel for industrial and commercial boilers. There has been recent concern, however, as to the health risks involved in burning recycled oil containing halogenated compounds. As reported in the 29 Nov. 1985 edition of the Federal Register, these health risks have prompted the EPA to impose new regulations involving the use and management of used oil. Specifically, levels for total halogen content have been set between 1000 and 4000 ppm. Above this concentration range, the oil is considered to be a hazardous waste. Since about 500 million gallons of used oil are burned each year, an inexpensive and reliable test method is needed for determining the halogen content of a used oil at the site of its generator.

In response to this need, Auburn University, under sponsorship of the EPA, has been working on the development of a field test to determine halogen concentrations in waste oils. This test is an extension of the Beilstein flame emission test and will selectively test for halogenated solvents in waste oils. The test is very inexpensive, easily performed, and agrees with the standard ASTM oxygen bomb technique within a margin of 10 to 25%.

The test is a very simple procedure requiring only hydrogen and copper wool as replenishable materials. A copper probe is first burned to remove any oxidation which may interfere with the test. The clean probe is then dipped into the oil sample and placed in the flame. Copper halides radiate light at about 436 nm; therefore, the presence of halogenated solvents is indicated by a blue-green emission. Since the intensity of the blue-green emission is a function of organic halide concentration, this concentration can be determined by measuring the flame intensity using a photocell. The organic halide content of very nonvolatile samples can be determined as low as about 70 ppm. More volatile samples require dilution with a nonvolatile oil. For most waste oils, a dilution ratio of 10:1 diluent oil to waste oil is sufficient; this results in a lower threshold detection limit of 700 ppm halide.

The testing procedure works well for most waste oils. The reproducibility is poor for oils which contain significant amounts of water or for those that are highly volatile. With experience, the test can be used to screen even these types of oil, but the results are not very quantitative.

This test has shown great promise for on-site determinations of organic halide concentrations due to solvent contamination in waste oils. Inconclusive tests are obtained for only a small percentage of oils, but even these samples can usually be screened qualitatively for the 1000-ppm limit. This test can be performed by waste oil users, dealers, and transporters as well as EPA enforcement personnel, thus making the new regulations more easily met. This test represents a simple, inexpensive, and reliable method of screening waste oils for organic halide contamination in the field.
Plasticity Induced Fatigue Crack Closure
Authors: Davidson DL
Published: February 2009

Experimental measurements of plasticity-induced crack closure related factors were made on the aluminum alloy 7091-T7E69 using high resolution microscopy techniques. Two stress intensity factors were examined at a stress ratio of 0.1. The length of open crack as a function of load magnitude and the load required to open the crack to its tip were measured. Crack opening displacements and strains were determined for partially and fully open cracks. From experimental measurements, the residual stresses in the crack wake were computed, using two different methods. Models and simulations of crack closure were examined in light of the experimental results. Interpretation of these results gives useful insights into crack closure phenomena but does not allow predictions of crack closure magnitude to be made.
The Effect of Test Frequency and Geometric Asperities on Crack Closure Mechanisms
Authors: Sheth JK , Gerberich WW
Published: February 2009

The effect of frequency, if any, on fatigue crack closure mechanisms is investigated for a series of Fe-Si alloys. Fatigue cracks were grown at 30, 3, 0.3, and 0.03 Hz. At the end of each of these, closure loads were measured using the point of deviation from linearity of the load versus crack opening displacement (COD) curve in the unloading direction. Oxide-induced closure effects were minimized by performing all experiments in nitrogen or hydrogen. An attempt was also made to isolate the effect of geometric asperities by comparing the results to those obtained from single crystal specimens, in which the cracks were grown in hydrogen gas to keep the crack surfaces as flat as possible on the {100} plane. For these specimens, closure loads of the order of 1 to 4.5 MPa · m1/2 were observed, and the closure effect was seen to arise from the longitudinal cleavage river-steps associated with fatigue crack propagation. The heights of these steps were estimated from scanning electron micrographs; they ranged from 1.5 to 7 μm. The closure loads in the polycrystalline specimens were of the order of 4.7 to 6.5 MPa · m1/2. The fracture surfaces are seen to be much rougher than in the single crystal specimens. The closure effect in these materials is shown to be largely geometry related for the single crystals, while for the polycrystals, both roughness and reverse slip are shown to be important.
The Dependence of Crack Closure on Fatigue Loading Variables
Authors: Hudak SJ , Davidson DL
Published: February 2009

Crack opening loads were measured local to the crack tip in aluminum alloy 7091 and 304 stainless steel using both optical and electron microscopy combined with the stereoimaging technique. These measurements showed that the crack peels open nonlinearly such that significant load increases are required to open the crack the last few microns from the tip. Based on measurements of the crack-tip opening load, the quantity U = ΔKeff/ΔK was found to depend on fatigue loading variables according to the simple relationship, U = 1 − Ko/Kmax = 1 − Ko(1−R)/ΔK, where Ko is a constant believed to be related to the threshold for pure Mode I fatigue crack growth. Although remote compliance measurements detect less crack closure than do the local stereoimaging measurements, these results follow a relationship similar in form to that above. Results are compared with previous measurements, as well as with analytical crack closure predictions based on the Dugdale-Barenblatt formulation. The latter underpredicts the experimental results and cannot predict their dependence on ΔK, thereby suggesting that either the model needs to be reformulated or other closure mechanisms are operative in addition to plasticity induced closure.
A Procedure for Standardizing Crack Closure Levels
Authors: Donald JK
Published: February 2009

A consistent and automated method of global crack closure measurement has been developed for the compact tension specimen. The technique uses the elastic compliance technique enabling both crack length and crack closure measurements to be automated with the aid of a digital computer data acquisition and control system. The procedure is limited to steady state fatigue crack growth rates above the near-threshold regime.
Development of Fatigue Crack Closure with the Extension of Long and Short Cracks in Aluminum Alloy 2124: A Comparison of Experimental and Numerical Results
Authors: Ritchie RO , Yu W , Holm DK , Blom AF
Published: February 2009

The development of crack closure during the extension of long and short fatigue cracks has been investigated in a 2124 aluminum alloy using both experimental and numerical procedures. Specifically, the growth rate and closure behavior of long (∼17 to 38 mm) cracks in compact C(T) specimens and through-thickness physically-short (∼50 to 40 μm) cracks in single-edge-notched SEN(B) bend specimens have been examined experimentally from threshold levels to instability (over the range ∼10−12 to 10−7 m/cycle), and results compared with those predicted numerically using an elastic-plastic finite-element analysis of fatigue crack advance in plane strain. It is shown that the numerical analysis consistently underpredicts the magnitude of crack closure for both long and short cracks, particularly at near-threshold levels; an observation attributed to the fact that the numerical procedures can only model contributions to closure from cyclic plasticity, whereas, in reality, significant additional closure arises from the wedging action of fracture surface asperities and corrosion debris. Such closure is shown to provide the predominant mechanism for rationalizing differences in the growth rate behavior between long and physically short cracks, although other factors, such as the nature of the singularity and the extent of local plasticity, are deemed potentially to be important.
Correlation Between Numerically Predicted Crack Opening Load and Measured Load History Dependent Crack Growth Threshold
Authors: Anquez L , Baudin G
Published: February 2009

The present paper deals with the application of a two-dimensional (plane stress) elastoplastic (Prager's flow rule) finite—element analysis to predict crack opening stresses during the crack growth process under cyclic loading. The main results obtained are as follows:

Crack closure is achieved at crack tip as soon as unloading begins. Under constant amplitude loading, the ratio of the opening force to the maximum force is nearly constant and in good accordance with experiment. ΔKeff is an appropriate parameter if and only if some plastic strain correlations are satisfied around crack tip. This is the case in two-level (HiLo) loadings; so it is possible to have an evident explanation of crack arrest phenomenon. Comparisons with experiments are, in this case, quite satisfactory.
Analysis of Crack Opening Behavior by Application of a Discretized Strip Yield Model
Authors: de Koning AU , Liefting G
Published: February 2009

The crack opening behavior of a fatigue crack in a centrally cracked panel was studied using a discretized version of the Dugdale and Barenblatt model. The effect of crack growth was also included. Results obtained for constant amplitude loading were in agreement with data reported in the open literature. The effect of application of single overload-underload combinations and of simple block loading programs on the crack opening behavior were analyzed. The results were compared with predictions based on an existing empirical model (CORPUS). In this way the criteria used in the CORPUS model to select significant load excursions in the applied load sequence were checked. Finally, both models were used to predict crack growth under a simplified landing gear load sequence. The predicted crack opening loads and the crack growth lives were in agreement with experimental data.
Correlation of Fatigue Crack Growth Data Obtained at Different Stress Ratios
Authors: Booth GS , Maddox SJ
Published: February 2009

Fatigue crack propagation tests have been carried out on three C-Mn structural steels at stress ratios between 0.67 and −4. Surface strain gage techniques have been used to determine crack-tip closure stress and an expression proposed to relate the proportion of the stress cycle for which the crack tip is actually open U to stress ratio. Satisfactory correlation of the crack propagation results for this range of stress ratios has been achieved by defining an effective stress intensity factor range as the proportion U of the total stress intensity range. In addition, reasonable correlation of the results was obtained on the basis of the tensile portion of the stress intensity factor range.
The Effect of Closure on the Near-Threshold Fatigue Crack Propagation Rates of a Nickel Base Superalloy
Authors: Zawada LP , Nicholas T
Published: February 2009

An experimental study of the effects of closure on the near-threshold fatigue crack growth rates in a nickel-base superalloy is presented. Fatigue crack propagation (FCP) tests were conducted on Rene' 95 at 650°C under either constant load amplitude (increasing ΔK) or under threshold load shedding (decreasing ΔK) test conditions. Particular emphasis was placed on the level of closure in the near threshold regime as a function of load history, specimen size and thickness, and environment. Test results indicated that for decreasing load threshold tests the recorded threshold levels were independent of load shedding rates. Specimen thickness was found to have no influence on FCP rates, threshold values, or closure loads, thereby eliminating plasticity induced closure as a dominant mechanism. Tests performed in vacuum produced closure values identical to those obtained in an oxidizing environment. It was concluded that the primary operating closure mechanism was roughness induced closure.
Influence of Some Mechanical Parameters on the Crack Closure Effect in Fatigue Crack Propagation in Aluminum Alloys
Authors: Clerivet A , Bathias C
Published: February 2009

In the first part of this paper a review of a previous work on crack closure mechanisms in compact tension specimens of 7175 T651 aluminum alloy is presented. Results showed that the methods of measurement are responsible for the controversy on Elber's concept. However mechanisms of closure in such a specimen are too complex to conclude on the influence of mechanical parameters on the crack closure effect. Hence, tests have been performed, on the one hand, on thin sheets in order to verify the validity of Elber's concept in plane stress conditions. On the other hand, tests were carried out using tension and bending specimens containing surface or corner flaws, where a plane strain state is predominant. These works have been conducted on a 2124 T351 aluminum alloy. The crack closure mechanism has been found to be the principal parameter that governs the propagation mechanisms whatever parameters are studied, at least when the Paris relation is verified. Parameters such as applied stress, R ratio, stress state, and load variation (overload), have been retained for this study.
Shear Strength of Masonry Piers Under Cyclic Loading
Authors: Johal LSP , Anderson ED
Published: February 2009

This paper describes a test program to evaluate shear behavior of masonry piers constructed with portland cement and masonry cement-based mortars and tested under simulated seismic loading. Both clay brick and concrete masonry block pier specimens were subjected to in-plane cyclic shear stresses. Several brands of masonry cement and portland cement were used in fabrication of 32 specimens. The pier portion of specimens was minimally reinforced for flexure and partially grouted. No shear reinforcement was provided. The specimens were loaded in a manner to eliminate any axial force in the pier cross section. Results indicate that the shear strength of masonry piers constructed with masonry cement-based mortars compared favorably with those constructed with portland cement-based mortars. Values of maximum shear stress obtained with portland cement and masonry cement-based mortars were close and within the range of scatter normally expected in experimental data. The shear strength was not influenced significantly by the use of Types M or S mortars.
Investigation of Masonry Bond and Surface Profile of Brick
Authors: Ribar JW , Dubovoy VS
Published: February 2009

The original objective of this research was to investigate the influence of masonry cements on flexural bond of mortar to clay brick units and on the water penetration of masonry assemblies fabricated using these materials. The test variables included 20 masonry cements and 11 types of brick, each representing materials produced in different areas of North America. Results of flexural bond strength tests on masonry assemblies indicated that factors other than mortar composition affected bond strength. Accordingly, an investigation was made to evaluate the effect of surface texture of clay brick units on bond strength. A surface profilometer, from which results could be quantified, was used for this work. Results suggest that surface texture of the brick is a primary factor in the development of bond strengths.
An Investigation of an Extended Plastic Life Mortar
Authors: Matthys JH , Houston JT , Dehghani A
Published: February 2009

The use of an extended plastic life mortar which can be stored for a prolonged period of time without losing its desirable properties can be beneficial to the masonry industry in several ways.

This paper presents the findings of a two-phase study related to an extended plastic life mortar (ready mix mortar) using a single brand of set-reducing additive. Phase 1 was optimization of a final mix in terms of setting characteristics and compressive strength. Mixes were made which examined the variables of dosage rates, cement content, lime content, and fly ash content. Each mix was characterized by compressive strength, air content, water retention, and plasticity. Several mix designs were generated for achieving particular strength and setting characteristics.

Phase 2 compared one of the generated extended plastic life mortars to a standard portland cement lime Type N mortar as defined in ASTM Specification for Mortar for Unit Masonry (C 270) with respect to mechanical properties. The properties examined included: compressive strength, bond strength, freeze thaw, corrosion, shrinkage, efflorescence, and compressive strength and modulus of elasticity of masonry prisms.
Experimental and Numerical Validation of a Ductile Fracture Local Criterion Based on a Simulation of Cavity Growth
Authors: Devaux J-C , Mudry F , Pineau A , Rousselier G
Published: February 2009

A local criterion based on the simulation of hole growth by plastic deformation has been evaluated. Fracture of a material volume is reached for an assumed critical value of cavity growth. This critical value is determined from notched tensile tests. When dealing with cracked geometries, a process zone is introduced at the crack tip. This zone is modeled as the first mesh element (a)c at the crack tip in a finite-element code. The size of this element, which is a material constant, is measured from a conventional compact tension (CT) test. Different tests with cracked geometries were carried out on side-grooved CT specimens of different sizes (25 and 50-mm width) and on axisymmetrically cracked tensile bars (TA) with 15, 30, and 50-mm outer diameters. In all cases the fracture was flat with no shear lips. Keeping the parameters of the fracture local criterion constant, crack initiation and crack propagation were modeled using the node release technique. The numerical procedure and results are described in detail. The model results are shown to be in good agreement with the experimental results.
Evaluation of Crack Growth Based on an Engineering Approach and Dimensional Analysis
Authors: Bernard J
Published: February 2009

Following tests carried out on compact tension [C(T)] specimens in AISI 316H steel, the engineering approach (EA) of Shih et al. and the key curve method (KC) of Ernst et al. were used to calculate, from the obtained load-displacement records, the crack extensions that took place. A method to define unambiguously the strain hardening exponent entering the EA estimation procedure is outlined. This gave satisfactory predictions of the load-displacement levels encountered in the tests. As a consequence, a calibration function, required in the KC analysis, could be elaborated. Both methods yielded final crack extensions that agree within 15% with the measured ones. The estimated values thus remain within the generally accepted maximum allowable errors.
Geometry Effects on the R-Curve
Authors: Landes JD , McCabe DE , Ernst HA
Published: February 2009

R-curves are at present recognized as the elastic-plastic fracture toughness property to be used in failure analysis. However, they are useful only if it can be shown that they are geometry independent. The objective of this study was to demonstrate this geometry independence using four specimen types—the compact, single-edge-notched tension, center-cracked tension, and double-edge-notched tension types. The material used was an A553B Class 1 steel taken from a nuclear reactor nozzle cutout. To eliminate variable constraint between geometries, the thickness of all the specimens was 2.5 mm (0.1 in.) so that plane stress was maintained throughout.

Fracture toughness was characterized in terms of modified J and the Hellmann-Schwalbetype crack-tip opening displacement. Both parameters demonstrated that the R-curve is geometry independent except for the center-cracked specimens. In that case, a slip-line deformation field peculiar to center-cracked tension specimens was identified as the cause of geometry dependence. Double-edge-notched tension specimens proved that the R-curve difference was not due to pure tension loading.

An experimental calibration was made for the single-edge-notched geometry using a series of blunt notch specimens with varying a/W. From this, J can be determined from the area under the experimental load versus displacement records. A normalizing procedure for load versus displacement was developed from this calibration which allows flow properties to be examined for any size, thickness, or a/W. The normalized load displacement curves can be used for J calibration.
Evaluating Steel Toughness Using Various Elastic-Plastic Fracture Toughness Parameters
Authors: Wilson AD , Donald JK
Published: February 2009

The elastic-plastic fracture toughness results for 185 single-specimen, unloading compliance tests from 32 plates of 13 steel grades [yield strengths 228 to 924 MPa (33 to 134 ksi)] are summarized. J-integral (JIc), crack-tip-opening displacement (CTOD), and tearing modulus (T) values are determined for each of these completely ductile behaving tests using the latest testing and evaluation procedures. Three J computational methods and two graphical evaluation techniques for JIc are investigated. The effects of these on the subsequent JIc and T values are established. Correlations between various J and CTOD based parameters are presented. In addition, correlations between J, CTOD, and T parameters and Charpy V-notch impact levels are established. The influence of the various computational and graphical methods and different elastic-plastic fracture toughness parameters upon metallurgical comparisons resulting from inclusion control in various steels is reported.
Simplified Procedures for Handling Self-Equilibrating Secondary Stresses in the Deformation Plasticity Failure Assessment Diagram Approach
Authors: JM Bloom
Published: February 2009

The most accurate procedure for handling self-equilibrating secondary stresses in the elastic-plastic region is a numerical nonlinear finite-element formulation. However, it has been shown that an excellent approximation is possible in closed form knowing only the sum of the stress-intensity factors due to all stresses and the fully plastic J-integral expression for a flawed structure under non-self-equilibrating primary loading only. For the deformation plasticity failure assessment diagram (DPFAD) approach, this concept is impractical since each thermal transient or residual stress state would require a separate DPFAD curve. A simpler, more acceptable procedure is to generate the DPFAD curve for non-self-equilibrating primary loading (which is independent of the level of applied loading) and adjust the assessment points to reflect the effects of plasticity produced by the self-equilibrating secondary stresses. Two such simpler approaches are recommended, one based on adjusting Kr, while the other approach redefines Sr, where (Kr, Sr) is the assessment point to be evaluated. Comparisons of the two simpler procedures with the more accurate closed form procedure were made, and both simpler methods were found to be only slightly nonconservative in the region of small-scale yielding to elastic-plastic fracture. For the fully plastic region, both methods are conservative. An example problem illustrating the use of both simpler methods is presented.
Prediction of Critical Crack Size in Plastically Strained Welded Panels
Authors: Sumpter JDG
Published: February 2009

Fracture toughness data for two HY80 weld metals are used to illustrate the application of Jc as a fracture analysis parameter in a form analogous to that developed in the United Kingdom for critical crack-tip opening displacement, c, testing and analysis. Jc results from dynamically tested, shallow-surface-notched, welded bend specimens are shown to correlate well with the crack size and plastic strain levels required to initiate unstable fracture in fatigue-cracked Pellini bulge explosion test panels. Jc is shown to be a clear function of crack depth for shallow cracks in bending. The use of Jc data from conventional deeply notched bend specimens results in very conservative critical crack size predictions.
An Automated Triaxial Testing System
Authors: Li XS , Chan CK , Shen CK
Published: February 2009

This paper describes a recently developed automated triaxial testing system. Loading is controlled by a closed-loop feedback scheme capable of performing stress- or strain-controlled tests in the standard triaxial environment. The system has two control channels allowing separate control of both the axial load and the chamber pressure.

Software written especially for this system can control back pressure saturation, consolidation, shear loading, cyclic loading, and a number of special loading programs. Each software package is well documented with complete notes for interactive dialogue with the computer.

The data retrieving and plotting software is capable of processing data and converting it to 20 variables commonly used in geotechnical engineering. These variables can be plotted with different combinations for display and detailed study. Typical test results for a fine sand are included to demonstrate the abilities of the system.

The system is well suited for research purposes, however it can also be used effectively in geotechnical material testing in consulting laboratories. The computer-based testing system is simple in operation, rapid in sampling, accurate in performance, and reasonable in cost.
Relationship Between Tensile and Compressive Strengths of Compacted Soils
Authors: Peters JF , Leavell DA
Published: February 2009

A direct-pull tension test was developed to study the behavior of compacted soils in total stress tension. A comprehensive series of tension and unconsolidated undrained compression tests was performed on Vicksburg silty clay; the data from these tests were supplemented with published data. Analysis of the data was based on relating the tensile strength parameter of the Griffith-Brace theory for brittle fracture to the suction-derived cohesion term of the Fredlund-Morgenstern failure law for partially saturated soils. Application of the analysis was demonstrated by relating tensile and compressive strengths to water content and void ratio.
Influence of Filter Paper and Leakage on Triaxial Testing
Authors: Leroueil S , Tavenas F , La Rochelle P , Tremblay M
Published: February 2009

A significant problem, especially in long-term tests, is leakage through the fittings and membrane. To avoid the first of these two sources of error, a cell with fittings enclosed in a back pressure chamber has been developed. To reduce leakage through the membrane, various cell fluids have been considered and tested in normal triaxial test conditions but with a dummy in place of the specimen. The results show that silicone oil minimizes the leakage.

Filter papers are used in triaxial testing to accelerate the consolidation process and the equalization of effective stresses within the specimen during shearing. The drainage capacity of five different filter papers was meaured, and their effect on the consolidation and shear processes was evaluated by comparative tests. The results show that in the overconsolidated range, the filter papers are efficient; however, due to the high coefficient of consolidation of natural clays in this range, they are not really useful. In the normally consolidated range, the efficiency of the filter drains during consolidation is considerably less than expected; contrary to what has been observed by other researchers, no effect of the filter drains on shear strength was found.
Measurement of Deformations in the Standard Triaxial Environment with a Comparison of Local Versus Global Measurements on a Fine, Fully Drained Sand
Authors: Linton PF , McVay MC , Bloomquist D
Published: February 2009

Deformation measurement devices are reviewed. Measurements obtained using linear variable differential transformers attached to the middle third of a specimen and the standard burette-piston system are compared. Results are presented for hydrostatic and standard compression tests run on a fully saturated, fully drained, poorly graded fine sand—Reid-Bedford, Unified Soils Classification System group SP. The effects of end restraints and membrane penetration are discussed in regard to the test results. In addition, a new technique is presented for measuring specimen saturation on coarse grain soils.
Triaxial Testing of Marine Sediments with High Gas Contents
Authors: Rau G , Chaney RC
Published: February 2009

Gas types, zonation present in marine sediments, the corresponding mechanism of bubble formation, and methods of performing traxial tests on gassy sediments are discussed. Gases (methane and hydrogen sulfide; methane gas predominates) may be found either in solution or in the bubble phase in the sediment. A method to estimate the amount of gas that theoretically comes out of solution is shown. The result of gas bubbles is a reduction in the bulk modulus of the pore fluid. The bulk modulus of a gas-water mixture decreases with incresing fluid pressure. Results of decreasing bulk modulus are shown to reduce the pore pressure increment per application of a load increment. Triaxial testing techniques are recommended when (1) gas is in solution, (2) gas is in the bubble phase, and (3) gas is still evolving.
Results and Interpretation of Multistage Triaxial Compression Tests
Authors: Soranzo M
Published: February 2009

The procedure for performing and interpreting multistage triaxial compression tests is described. The results obtained from unconsolidated undrained and isotropically con-solidated undrained tests on normally consolidated alluvial clay and overconsolidated colluvial gravelly clay are presented.

A direct comparison of the results of single stage and multistage compression tests, performed on homogeneous samples, indicates that the latter procedure may be applied to soil specimens that reach failure with vertical strain greater than 8 to 10%.

To demonstrate the similarity between the two procedures and to interpret the tests when only a limited percentage of strain is available for each compression stage, stress versus strain, normalized stress versus strain, normalized tangent modulus versus stress, and Kondner's hyperbolic criterion were used in the analysis.
Triaxial Testing of Weak Rocks Including the Use of Triaxial Extension Tests
Authors: Millar PJ , Murray DR
Published: February 2009

The strength parameters of New Zealand Tertiary weak rocks are found to be intermediate between soil and rock. The nonlinear strength envelopes of these materials for the range of stresses encountered in engineering structures mean that the strength parameters cannot be adequately defined using standard triaxial compression tests.

The strength properties can be established at low stress levels by the triaxial extension test which allows tensile stresses to be developed in the neck of truncated specimens. At high stress levels a high stress triaxial cell is used with confining pressures up to 15 MPa.
Determination of Undrained Shear Strength of Low Plasticity Clays
Authors: Peters JF
Published: February 2009

Difficulties posed by low plasticity soils including silty and sandy clays, silts, and sands are described. The soils considered are not cemented and generally display the dependence between consolidation state and strength necessary to apply such procedures as Stress History and Normalized Soil Engineering Properties (SHANSEP). Unfortunately, these soils are highly susceptible to sampling disturbance because of the unavoidable low effective stress that remains in specimens after sampling. Sampling disturbance obscures consolidation behavior, making it difficult to estimate the in situ overconsolidation ratio. Also, the low compressibility of these materials makes it difficult to clearly define the virgin compression curve. Improvements in interpretation procedures will come only after a sound mechanical description of sampling disturbance has been developed.
Cyclic Triaxial Strain-Controlled Testing of Liquefiable Sands
Authors: Vucetic M , Dobry R
Published: February 2009

Two series of undrained cyclic triaxial strain-controlled tests were performed on two different Imperial Valley, California, silty sands which liquefied during an earthquake in 1981. Both intact and reconstituted specimens were tested, and the testing procedures are described. The experimental data confirm that cyclic shear strain is the fundamental parameter governing pore pressure buildup, because strain-controlled tests essentially eliminate the influence of specimen fabric and sample disturbance. Also, the results indicate that the cyclic triaxial test can be used to model cyclic simple shear (similar to seismic field conditions), if the cyclic simple shear strain, γcy, is related to the cyclic triaxial axial strain, εcy, by either of two similar analytical expressions: γcy = 1.5 εcy or γcy = √3 εcy. Consequently, a unique pore pressure model is developed and recommended to simulate the seismic pore pressure buildup at the site. This model is applicable to reconstituted and intact specimens of the two sands, despite their different void ratios and nonplastic silt contents, and is valid for both cyclic triaxial and cyclic simple shear strain-controlled conditions.
Triaxial Test for Embankment Dams: Interpretation and Validity
Authors: Dendani H , Flavigny E , Fry JJ
Published: February 2009

For the construction of two large dams, several triaxial test series were executed on the embankment materials. The first material is an altered sandstone and the second a filter material. Several stress paths of loading were tested: extension test, constant mean pressure test, constant stress ratio, and conventional tests. The various causes of error in the experiments were examined: end restraint, bedding error, and membrane penetration. For a good estimation of deformation modulus, direct measurements inside the triaxial cell were developed. The general results are presented and the methods produced high quality tests. The effects of the grain size distribution were also studied: on the same material, triaxial tests with different specimen diameters were conducted for various maximum grain sizes.
New Concept of Effective Stress in Unsaturated Soil and Its Proving Test
Authors: Karube D
Published: February 2009

Triaxial compression tests, including anisotropic consolidation tests, were performed on compacted kaolin clay by an automatically controlled apparatus. Test results were analyzed in terms of suction and (σ − ua), where σ is total normal stress and ua is pore air pressure, recognizing that when soil is saturated, ua becomes equal to uw, pore water pressure.

When suction is kept constant, the relationships among the observed shear strength, stress-strain, and stress-water content change can be formulated in equations similar to those of saturated soil, in which suction can be regarded as a factor contributing to soil constants. When both suction and all-around pressure are varied, the plastic volumetric strain can be expressed by an equation in which (σ − ua) is multiplied by a function of suction. Therefore suction can be regarded as a factor contributing to soil constants in this case too. These facts mean that the suction need not be regarded as one of the principal stress components such as (σ − ua) in the stress-strain equations of unsaturated soil.
Pore-Pressure Distributions in Constant Strain-Rate Triaxial Tests
Authors: Savage WZ
Published: February 2009

A theoretical study of pore-pressure distributions in drained, constant strainrate triaxial tests, an outgrowth and extension of earlier work by Gibson, Bishop, and Henkel, has been done to determine the experimental conditions under which pore-pressure gradients, and hence, effective stress differences throughout deforming triaxial test samples, are small.

It is concluded from the analysis of drained triaxial constant strain-rate tests that it is impossible to obtain a fully drained condition. In fact, in this test the long-term spatial pore-pressure distribution becomes parabolic. Unless strain rates are sufficiently low or permeabilities are sufficiently large to minimize the effect of this parabolic pore-pressure distribution, effective stresses in the deforming sample cannot approach uniformity and any property determinations based on the assumption of uniform effective stresses will be in error. A similar conclusion was reached by Gibson. It is also concluded that volumetric strains will be largest near the undrained end of a sample drained at one end, or largest in the middle of a sample drained at both ends. This strain distribution is a consequence of the parabolic pore-pressure distribution and suggests an explanation (apart from frictional end restraints) for any post-yield barreling observed in a drained triaxial test.
Effects of Sampling Disturbance on Shear Strength of Glacial Till and Compacted Fill
Authors: Dietzler DP , Moose DA , Schuh JC
Published: February 2009

Shear strength tests employing back pressure saturation, isotropic consolidation, and pore pressure measurements in the triaxial chamber are routinely used in the evaluation of landfill sites, deep excavations, earth dams, and highway embankments. Continuous soil sampling using a 1.5-m (5-ft) long split-barrel sampler and hollow-stem augers has proved to be highly efficient in sampling predominantly cohesive soils and cohesive fills. Whereas sampling with thin-walled tubes, ASTM D 1587, has been recognized as providing essentially undisturbed samples, experience with the split-barrel continuous sampler system indicates that visually it will yield equally undisturbed samples and provide better recovery in cohesive fills and extremely hard soils.

A comparative laboratory testing program was undertaken to investigate the differences in shear strength between samples of a glacial till obtained in accordance with the ASTM Method for Thin-Walled Tube Sampling of Soils (D 1587), samples carved from blocks, and samples obtained with the continuous split-barrel sampler. These three sampling systems were used to obtain samples from the same strata of saturated glacial till. Zones of carefully monitored compacted clay fill were also sampled using the thin-walled tube sampler and the continuous split-barrel sampler. The factors affecting sample disturbance and the results of a limited testing program are discussed.
Triaxial Compressive and Extension Strength of Sand Affected by Strength Anisotropy and Sample Slenderness
Authors: Lam W-K , Tatsuoka F
Published: February 2009

Drained triaxial compressive and extension strengths of air-pluviated sand were evaluated by means of a conventional triaxial apparatus taking into account both strength anisotropy and the effects of sample slenderness, that is, height/width or diameter ratio (H/D). The initial values of H/D employed were 2.0, 1.0, 0.5, and 0.25. The direction of the major principal stress σ1′ was either normal to or parallel to the bedding plane. It was found that the triaxial extension strength is greatly influenced by H/D. Strengths in the following four stress conditions were compared: (1) triaxial compression where the σ1′ direction is normal to the bedding plane, (2) triaxial extension where one of two σ1′ directions is normal to the bedding plane while the other is parallel to the bedding plane, (3) triaxial compression where the σ1′ direction is parallel to the bedding plane, and (4) triaxial extension where both σ1′ directions are parallel to the bedding plane. It was found that while the relative strength is a complicated function of H/D, generally the strength is the largest for the second case, intermediate for the first and fourth cases, and the smallest for the third case. This result suggests that (φ) is not a simple function of b = (σ2′ − σ3′)/(σ1′ − σ3′), which represents the relative magnitude of σ2′ against σ1′ and σ3′, but the strength anisotropy and failure mode, especially in triaxial extension, should be taken into account in a combined manner.
The Influence of Filter Strip Shape on Consolidated Undrained Triaxial Extension Test Results
Authors: Mitachi T , Kohata Y , Kudoh Y
Published: February 2009

A series of consolidated undrained triaxial extension tests was performed to investigate the influence of shape of filter strips on the required time of consolidation and undrained shear behavior of clay. Remolded saturated specimens of clay with five different filter strip shapes were consolidated isotropically in the triaxial apparatus and then sheared under undrained extension by decreasing axial stress, while lateral stress was maintained constant. Based on the test results, the filter strip with spiral slit is recommended for practical use in a consolidated undrained extension test because of fast consolidation and low tensile strength.