bluuebunny/crossref_metadata_2025 huggingface dataset:
Full-Scale Test on an Aged Cast Duplex Stainless Steel Lateral Connection: Results and Analysis
Authors: Le Delliou Patrick , Bezdikian Georges , Ould Pascal , Safa Nathalie
Published: July 2008

Some components (elbows, pump casings and lateral connections) of the primary loop of French PWRs are made of static cast duplex stainless steels. This kind of steel may age even at relatively low temperatures (in the temperature range of PWR service conditions), depending on the material composition. An important consequence of this ageing process is the decrease in the ductility and fracture toughness of the material. It is feared that an embrittlement, associated with the occurrence of casting defects, may increase the risk of failure. Therefore, an extensive programme has been launched by EDF in co-operation with Framatome ANP, in order to determine acceptability criteria for operating cast stainless steel components. This programme relies on a large R&D effort, involving metallurgical studies, large-scale experiments, development of specific finite element tools and J-estimation schemes, and research of methods to assess the ageing state of in-service components. This paper presents the main characteristics and results of an experiment conducted on an aged cast 45 degree lateral connection. This connection contained a machined notch at the acute corner and was tested under internal pressure. The chemical composition was chosen to obtain a fast thermal ageing and low fracture toughness properties. During the test, the defect initiated and grew subsequently by ductile tearing. The test showed that it was possible to obtain a significant amount of stable crack growth (about 2.5 mm) despite the low toughness properties of the aged material. The pressure reached at the end of the test was about twice the in-service pressure. A detailed fracture mechanics analysis, based on finite element calculations, was performed. These calculations fairly simulated the overall behaviour of the tested structure, gave a conservative prediction of the crack initiation pressure and well predicted the crack size associated with the maximum pressure. These tests and their detailed analyses contribute to validate and justify the methodology used in the integrity assessment of in-service cast duplex stainless steel components.
FSI Based on Bidirectional Coupling of High Order Solids to a Lattice-Boltzmann Method
Authors: Kollmannsberger Stefan , Scholz Dominik , Du¨ster Alexander , Rank Ernst
Published: July 2008

Currently, a joint effort is made by German research groups to establish a benchmark for a bidirectional Fluid-Structure-Interaction problem: a geometrically non-linear vibrating structure being agitated by a laminar flow of an incompressible Newtonian fluid. Among other approaches, a partitioned solution procedure has been developed in this framework using a high order FEM code for the structural side of the solution coupled to a Lattice-Boltzmann solver discretizing the fluid. The explicit coupling of these two completely different types of discretizations gives promising results also in terms of an efficient calculation. This paper briefly introduces the benchmark, presents the procedure used and gives some results obtained by the application of the method.
Residual Stress Improvement in Multi-Layer Welding of Austenitic Stainless Steel Plates by Using Water-Shower Cooling During Welding Process
Authors: Yanagida Nobuyoshi , Koide Hiroo
Published: July 2008

To reduce tensile residual stress in a welded region, we have developed a new cooling method that applies a water-shower behind the welding torch. When this method is applied to multi-layer welding of austenitic stainless steel plates, cooling conditions mainly determine how much the residual stress can be reduced. To determine the conditions, we first used FEM to evaluate the effects of water-shower cooling and interpass temperature on the residual stress. In addition, we found effective conditions for reducing tensile residual stress. To verify the validity of the conditions, three plates were welded with or without water shower cooling. Residual stresses of the plates were measured experimentally. It was found that tensile residual stresses occurred on the surface of the welds and that they were reduced when the water-shower was applied at the last pass. These measurement results agree well with the FEM analyses. It can therefore be concluded that water-shower cooling during the last welding pass is appropriate for reducing tensile residual stress in austenitic stainless steel at a multi-pass weld.
Simulation of Fatigue Crack Growth in a Detonation Tube
Authors: Mirzaei Majid , Salavatian Mehdi , Biglari Hasan
Published: July 2008

Internal gaseous detonation in cylindrical tubes can cause pressure loadings that move at high speeds. The resulting flexural waves in the tube wall can lead to high strains, which may exceed the equivalent static strains by up to a factor of 4. This paper starts with a brief review of an analytical model for the transient dynamic response of cylindrical tubes with finite length to internal detonation loading. The formulation of this analytical model considers the effects of transverse shear and rotary inertia and also accounts for the effects of reflected waves. The strain history obtained from this model is used to predict the cyclic growth of a hypothetical preexisting crack in a detonation tube using the AFGROW software. The second part of the paper describes the numerical investigation of the whole process. A simulated detonation loading is applied and the resulting fatigue crack growth is modeled using the FRANC3D software and its boundary element solver. The results indicate that realistic fatigue life predictions for tubes subjected to internal detonation require the consideration of the entire spectrum of strain and stress fluctuations, including the reflected flexural waves.
Elasto-Plastic FEM Stress Analysis of Pipe Flange Connections Under Internal Pressure
Authors: Sawa Toshiyuki , Nagata Satoshi , Ogata Naofumi
Published: July 2008

This paper deals with the stress analysis of a pipe flange connection with a spiral wound gasket using the elasto-plastic finite element method taking account the hysteresis and the non-linearity in the stress-strain curve of the spiral wound gasket, when an internal pressure is applied to the pipe flange connections with the different nominal diameters from 2 to 20. The effects of the nominal diameter of the pipe flange on the contact stress distributions at the interfaces are examined. Leakage tests of the pipe flange connections with 3 and 20 nominal diameters were conducted and measurement of the axial bolt force was also performed. The results by the finite element analysis are fairly consistent with the experimental results concerning the variation in the axial bolt force. By using the contact stress distributions and the results of the leakage test, the new gasket constants are evaluated. As a result, it is found that the variations in the contact stress distributions are substantial due to the flange rotation in the pipe flange connections with the larger nominal diameter. In addition, a method to determine the bolt preload for a given tightness parameter is demonstrated.
Fatigue Growth Behaviour for Surface Crack in Welded Joints Under Combined Tension and Bending Stresses
Authors: Zhao Jian-Ping , Huang Wen-Long
Published: July 2008

The fatigue growth behaviour for surface crack in welded joints under combined tension and bending stresses is studied by fatigue crack growth tests of 16MnR steel in bow specimens. In this present paper the Newman-Raju empirical equation was used for the stress intensity factor of a surface crack. The experimental results show that the Paris’ relationship between crack growth rate and stress intensity factor range under tension and bending fatigue stresses is still valid, and the relationship between the Paris’ coefficients Ca and Cc can be represented as Cc = (0.89)mCa.
Parametic Investigation on Limit Pressure of In-Service Welding Pipes
Authors: Xue Xiaolong , Zhu Jiagui , Sang Zhifu , Widera G. E. O.
Published: July 2008

In-service welding is the key operation of hot tapping which allows establishing a branch connection to a live pipeline. As there is no need to halt transportation, it can avoid large economic losses and serious air pollution. However, the operation is made much more difficult than normal welding by the pressure, temperature and flowing of contents. Firstly, the local high temperature causes a loss of material strength during in-service welding. Burn-through may occur if the region with elevated temperature can not support the stress it suffered. Secondly, the flowing media create a large heat loss through the pipe-wall, resulting in accelerated cooling of the weld, which increases hardness of HAZ and possibility of HAZ cracking. In this paper, temperature distribution of in-service welding under variable parameters onto SS304 pipeline with tap water flowing in the pipes were simulated by FEM. Temperature dependent material properties and effects of convection and radiation were considered. Internal heat generation and amplitude loading were used to simulate the moving heat source. The effect of the flowing of internal media was regarded as forced convection. Based on the results of temperature field, RSF and limit pressure of the pipe can be obtained and burn-through can be predicted. It can be concluded that the limit pressure decrease with the increasing of heat input. RSF increases with the increasing of pipe-wall thickness. While the thickness increases to an extent, RSF show little increase. RSF and limit pressure of the pipe increase with the increasing of flow rate. There is a range that the increase changes greatly. While in-service welding, the range should be adequately considered to determine operating condition optimally. According to the results, the maximum of heat input and minimum of pipe-wall thickness can be obtained.
Inelastic Stress Analysis of Pressurized Rectangular Passage With Multiple Internal Fins
Authors: Tu Shan-Tung , Zhou Guo-Yan
Published: July 2008

Compact process equipment has found wide applications in various industries for purpose of process intensification. The further miniaturization of the process equipment has led to the development of micro chemomechanical systems for high tech applications. The equipment is generally composed of a number of prolate passages of multiple internal fin elements subjected to internal pressures. To ensure the reliability and durability of the structures at high temperature, their strength should be appropriately designed. However, the inelastic stress analysis of the structure is highly complicated and time-consuming by general finite element methods if multiple plate-fin elements or channel plates are involved. In the present paper, the support fins are simplified as an inelastic foundation. The small deformation thin plate bending theory is introduced to analyze the deflection and stress distribution in the pressurized rectangular passage. Analytical expressions are derived for a single-layer prolate passage with multiple support fins. A comparison of the analytical results with the FE simulation verifies the feasibility and accuracy of the method.
Activity of the Small Modified Amino Acid α-Hydroxy Glycineamide on In Vitro and In Vivo Human Immunodeficiency Virus Type 1 Capsid Assembly and Infectivity
Authors: Abdurahman Samir , Végvári Ákos , Youssefi Masoud , Levi Michael , Höglund Stefan , Andersson Elin , Horal Peter , Svennerholm Bo , Balzarini Jan , Vahlne Anders
Published: July 2008

Upon maturation of the human immunodeficiency virus type 1 (HIV-1) virion, proteolytic cleavage of the Gag precursor protein by the viral protease is followed by morphological changes of the capsid protein p24, which will ultimately transform the virus core from an immature spherical to a mature conical structure. Virion infectivity is critically dependent on the optimal semistability of the capsid cone structure. We have reported earlier that glycineamide (G-NH2), when added to the culture medium of infected cells, inhibits HIV-1 replication and that HIV-1 particles with aberrant core structures were formed. Here we show that it is not G-NH2itself but a metabolite thereof, α-hydroxy-glycineamide (α-HGA), that is responsible for the antiviral activity. We show that α-HGA inhibits the replication of clinical HIV-1 isolates with acquired resistance to reverse transcriptase and protease inhibitors but has no effect on the replication of any of 10 different RNA and DNA viruses. α-HGA affected the ability of the HIV-1 capsid protein to assemble into tubular or core structures in vitro and in vivo, probably by binding to the hinge region between the N- and C-terminal domains of the HIV-1 capsid protein as indicated by matrix-assisted laser desorption ionization-mass spectrometry results. As an antiviral compound, α-HGA has an unusually simple structure, a pronounced antiviral specificity, and a novel mechanism of antiviral action. As such, it might prove to be a lead compound for a new class of anti-HIV substances.
Selection and Persistence of CTX-M-Producing
Escherichia coli
in the Intestinal Flora of Pigs Treated with Amoxicillin, Ceftiofur, or Cefquinome
Authors: Cavaco L. M. , Abatih E. , Aarestrup F. M. , Guardabassi L.
Published: July 2008

Extended-spectrum β-lactamases (ESBLs), mainly of the CTX-M family, have been associated with
Escherichia coli
strains of animal origin in Europe. An in vivo experiment was performed to study the effects of veterinary β-lactam drugs on the selection and persistence of ESBL-producing
E. coli
in the intestinal flora of pigs. Twenty pigs were randomly allocated into three treatment groups and one control group. All pigs were inoculated intragastrically with 10
10
CFU of a nalidixic acid (NAL)-resistant mutant derived from a CTX-M-1-producing
E. coli
strain of pig origin. Treatment with amoxicillin, ceftiofur, or cefquinome according to the instructions on the product label was initiated immediately after bacterial inoculation. Feces were collected from the rectum before inoculation and on days 4, 8, 15, 22, and 25 after the start of treatment. The total and resistant coliforms were counted on MacConkey agar with and without cefotaxime (CTX). Furthermore, MacConkey agar with CTX and NAL was used to count the number of CFU of the inoculated strain. Significantly higher counts of CTX-resistant coliforms were observed in the three treatment groups than in the control group for up to 22 days after the discontinuation of treatment. Ceftiofur and cefquinome exerted larger selective effects than amoxicillin, and the effects persisted beyond the withdrawal times recommended for these cephalosporins. The inoculated strain was detected in only nine animals on day 25. The increase in the number of CTX-resistant coliforms was mainly due to the proliferation of indigenous CTX-M-producing strains and the possible emergence of strains that acquired CTX-M genes by horizontal transfer. The study provides evidence that the cephalosporins used in pig production select for CTX-M-producing
E. coli
strains. Their use in animals should be carefully considered in view of the critical importance of cephalosporins and the zoonotic potential of ESBL-producing bacteria.
Plasmid-Mediated Quinolone Resistance Pump QepA2 in an
Escherichia coli
Isolate from France
Authors: Cattoir Vincent , Poirel Laurent , Nordmann Patrice
Published: July 2008

One hundred twenty-one extended-spectrum β-lactamse-producing enterobacterial clinical isolates were screened for the
qepA
gene. A single CTX-M-15-positive
Escherichia coli
isolate (0.8%) that produced the putative pump QepA2 was identified. This
qepA2
gene was located onto a 90-kb mobilizable plasmid that conferred reduced susceptibility to hydrophilic fluoroquinolones.
Genomic Analysis Reveals a Point Mutation in the Two-Component Sensor Gene
graS
That Leads to Intermediate Vancomycin Resistance in Clinical
Staphylococcus aureus
Authors: Howden Benjamin P. , Stinear Timothy P. , Allen David L. , Johnson Paul D. R. , Ward Peter B. , Davies John K.
Published: July 2008

Methicillin-resistant
Staphylococcus aureus
(MRSA), once restricted to hospitals, is spreading rapidly through the wider community. Resistance to vancomycin, the principal drug used to treat MRSA infections, has only recently emerged, is mainly low level, and characteristically appears during vancomycin therapy (vancomycin-intermediate
S. aureus
[VISA] and hetero-resistant VISA). This phenomenon suggests the adaptation of MRSA through mutation, although defining the mutations leading to resistance in clinical isolates has been difficult. We studied a vancomycin-susceptible clinical MRSA isolate (MIC of 1 μg/ml) and compared it with an isogenic blood culture isolate from the same patient, despite 42 days of vancomycin treatment (MIC of 4 μg/ml). A whole-genome sequencing approach allowed the nearly complete assembly of the genome sequences of the two isolates and revealed only six nucleotide substitutions in the VISA strain compared with the parent strain. One mutation occurred in
graS
, encoding a putative two-component regulatory sensor, leading to a change from a polar to a nonpolar amino acid (T136I) in the conserved histidine region of the predicted protein. Replacing the
graS
allele of the vancomycin-susceptible parent strain with the
graS
allele from the VISA derivative resulted in increased vancomycin resistance at a level between those of the vancomycin-susceptible
S. aureus
and VISA clinical isolates, confirming a role for
graRS
in VISA. Our study suggests that MRSA is able to develop clinically significant vancomycin resistance via a single point mutation, and the two-component regulatory system
graRS
is a key mediator of this resistance. However, additional mutations are likely required to express the full VISA phenotype.
Human Mast Cell Activation byStaphylococcus aureus: Interleukin-8 and Tumor Necrosis Factor Alpha Release and the Role of Toll-Like Receptor 2 and CD48 Molecules
Authors: Rocha-de-Souza Claudio M. , Berent-Maoz Beata , Mankuta David , Moses Allon E. , Levi-Schaffer Francesca
Published: July 2008

The ability ofStaphylococcus aureusto invade and survive within host cells is believed to contribute to its propensity to cause persistent and metastatic infections. In addition,S. aureusinfections often are associated with atopic diseases such as dermatitis, rhinitis, and asthma. Mast cells, the key cells of allergic diseases, have a pivotal role in innate immunity and have the capacity of phagocytosis, and they can destroy some pathogenic bacteria. However, little is known about the ability of some other bacteria to survive and overcome mast cell phagocytosis. Therefore, we were interested in evaluating the interplay between mast cells andS. aureus. In this study, we show that human cord blood-derived mast cells (CBMC) can be infected by pathogenicS. aureus.S. aureusdisplayed a high adherence to mast cells as well as invasive and survival abilities within them. However, when infections were performed in the presence of cytochalasin D or when CBMC were preincubated with anti-Toll-like receptor 2 (TLR2) or anti-CD48 antibodies, the invasiveness and the inflammatory response were abrogated, respectively. Furthermore, we observed an increase of TLR2 and CD48 molecules on CBMC afterS. aureusinfection. The infection of CBMC withS. aureusalso caused the release of tumor necrosis factor alpha (TNF-α) and interleukin-8 (IL-8). Both live and killedS. aureusorganisms were found to trigger TNF-α and IL-8 release by CBMC in a time-dependent manner. Cumulatively, these findings suggest thatS. aureusinternalizes and survives in mast cells. This may play an important role in infections and in atopic diseases associated withS. aureus.
A Tripartite Efflux Pump Involved in Gastrointestinal Colonization by
Klebsiella pneumoniae
Confers a Tolerance Response to Inorganic Acid
Authors: Coudeyras Sophie , Nakusi Laurence , Charbonnel Nicolas , Forestier Christiane
Published: July 2008

The colonization of the gastrointestinal tract of patients by the opportunistic gram-negative bacillus
Klebsiella pneumoniae
generally occurs prior to the development of nosocomial infections. Mutant strain C-81 was isolated owing to its reduced capacity to colonize the digestive tract in a murine model following transposon mutagenesis (N. Maroncle, D. Balestrino, C. Rich, and C. Forestier, Infect. Immun. 70:4729-4734, 2002). Nucleotide sequence analysis showed that the transposon had inserted into the first open reading frame,
eefA
, of a three-gene locus (
eefABC
) whose homologue encodes a tripartite efflux pump in
Enterobacter aerogenes
(M. Masi, J. M. Pages, C. Villard, and E. Pradel, J. Bacteriol. 187:3894-3897, 2005), and this operon includes an additional short (183-bp) potential open reading frame,
eefX
, upstream of
eefA
. In vivo assays showed that a Δ
eefA
isogenic mutant strain normally colonized the gastrointestinal tract in single-strain tests but was significantly impaired in competition against wild-type strain LM21. Although the cecum was the compartment with the highest number of CFU, the Δ
eefA
mutant also was detected in the stomach in numbers smaller than those of the wild-type strain. The expression of this potential efflux pump could not be linked to any antimicrobial drug resistance phenotype, but it conferred on the bacteria an acid tolerance response to inorganic acid. The expression of the
eef
promoter region, measured via a
lacZ
reporter construction, was slightly induced by an acidic environment and also by hyperosmolarity but not by the presence of bile salts. These results suggest that an efflux pump can confer measurable ecological benefits on
K. pneumoniae
in an environment with high competition potential.
The Antifungal Vaccine Derived from the Recombinant N Terminus of Als3p Protects Mice against the BacteriumStaphylococcus aureus
Authors: Spellberg Brad , Ibrahim Ashraf S. , Yeaman Michael R. , Lin Lin , Fu Yue , Avanesian Valentina , Bayer Arnold S. , Filler Scott G. , Lipke Peter , Otoo Henry , Edwards John E.
Published: July 2008

Vaccination with the recombinant N terminus of the candidal adhesin Als3p (rAls3p-N) protects mice from lethal candidemia. Candidal Als3p also is structurally similar to the microbial surface components recognizing adhesive matrix molecule adhesin, clumping factor, fromStaphylococcus aureus.To determine the potential for cross-kingdom vaccination, we immunized mice with rAls3p-N or negative control proteins and challenged them via the tail vein withS. aureusor other gram-positive or gram-negative pathogens. The rAls3p-N vaccine, but neither tetanus toxoid nor a related Als protein (Als5p), improved the survival of vaccinated mice subsequently infected with multiple clinical isolates ofS. aureus, including methicillin-resistant strains. The rAls3p-N vaccine was effective againstS. aureuswhen combined with aluminum hydroxide adjuvant. However, the vaccine did not improve the survival of mice infected with other bacterial pathogens. Vaccinated, infected mice mounted moderated type 1 immune responses. T lymphocyte-deficient mice were more susceptible toS. aureusinfection, but B lymphocyte-deficient mice were not. Furthermore, T but not B lymphocytes from vaccinated mice mediated protection in adoptive transfer studies. The passive transfer of immune serum was not protective. These data provide the foundation for cross-kingdom vaccine development againstS. aureusandCandida, which collectively cause 200,000 bloodstream infections resulting in ≥40,000 to 50,000 deaths annually in the United States alone.
Cytolethal Distending Toxin Induces Caspase-Dependent and -Independent Cell Death in MOLT-4 Cells
Authors: Ohara Masaru , Hayashi Tomonori , Kusunoki Yoichiro , Nakachi Kei , Fujiwara Tamaki , Komatsuzawa Hitoshi , Sugai Motoyuki
Published: July 2008

Cytolethal distending toxin (CDT) induces apoptosis using the caspase-dependent classical pathway in the majority of human leukemic T cells (MOLT-4). However, we found the process to cell death is only partially inhibited by pretreatment of the cells with a general caspase inhibitor, z-VAD-fmk. Flow cytometric analysis using annexin V and propidium iodide showed that a 48-h CDT treatment decreased the living cell population by 35% even in the presence of z-VAD-fmk. z-VAD-fmk completely inhibited caspase activity in 24 h CDT-intoxicated cells. Further, CDT with z-VAD-fmk treatment clearly increased the cell population that had a low level of intracellular reactive oxygen. This is a characteristic opposite to that of caspase-dependent apoptosis. Overexpression of
bcl2
almost completely inhibited cell death using CDT treatment in the presence of z-VAD-fmk. The data suggest there are at least two different pathways used in CDT-induced cell death: conventional caspase-dependent (early) apoptotic cell death and caspase-independent (late) death. Both occur via the mitochondrial membrane disruption pathway.
Triaxial Extension Tests on Hollow Cylinder Sand Specimens
Authors: Jamal A. K.
Published: July 2008

Triaxial extension tests were carried out on hollow cylinder sand specimens of identical external geometry under identical test boundary conditions. For reference, solid cylinder sand specimens were tested under identical boundary conditions. The radial width of the hollow cylinders was varied and the test parameters of specimen strength and deformation were found to vary systematically with the specimen radial width. The hollow cylinder extension strengths were significantly lower than the corresponding solid cylinder strengths. In the extreme case, a difference in shearing angle values of 11° was found. However, the behavior of these specimens was found to be quite consistent, when allowance was made for energy spent in volume dilatation and approximately constant frictional strengths were obtained, independent of specimen configuration. The differing modes of behavior of the hollow cylinder sand specimens is considered to be an inherent property of the specimen configuration and this finding has important implications for the interpretation of the conventional extension test.Method of test specimen fabrication and the test procedures are described as well as the hollow cylinder apparatus and an internal load transducer which was used for the measurement of the axial load in these experiments.
Settlement Performance of the Burlington Bay Skyway
Authors: Matich M. A. J. , Stermac A. G.
Published: July 2008

The Burlington Bay Skyway is founded on a deep baymouth bar which is believed to be about 10 000 years old and to be normally loaded with respect to present ground level. Beneath the northern half of the bar there is a considerable depth of clay, which is also believed to be normally loaded under the weight of the bar. Bedrock occurs directly beneath the southern half.The skyway is symmetrical about Burlington channel, which is approximately centrally located along the length of the bar. Foundations include 74 piers and the abutments. Two main piers are carried on steel H-piles acting in friction, while 20 other piers on the north side are founded on short timber piles. All other piers, and the abutments, are founded on spread footings. The superstructure is of steel construction incorporating plate girder and rolled steel beam spans with continuity in units of three and four spans, respectively. Computations carried out during design indicated that differential settlements could exceed tolerable limits for continuous spans. Provision for shimming was therefore made, and settlement observations taken to provide the necessary control.The results of the settlement readings are presented primarily as a case history, along with a number of unusual features in the foundation subsoil arising out of its origin as a deep bar deposit.
The Geotechnical Design of the Townline Road–Rail Tunnel
Authors: Conlon Robert J. , Tanner Roy G. , Coldwell Keith L.
Published: July 2008

The Townline road–rail tunnel is being constructed beneath the relocation of the Welland canal to the east of the city of Welland. Construction is by opencut and cut-and-cover through up to 80 ft (24 m) of lacustrine clays and clay tills. The lower stratified zone in the lacustrine clays has a minimum shear strength parallel to the bedding in some critical layers. Slope stability studies involved detailed sampling and testing, including block samples and 5-in.(13-cm) tube samples, and correlations with previous landslides in the area. These studies demonstrate that the mechanism of landslides in this stratigraphy involves a long flat portion of failure surface in the lower stratified zone, and that the shear strength available along this portion of the failure surface is consistent with the minimum shear strengths measured parallel to the bedding. Slopes as flat as 8.5:1 are required in areas which combine the deepest cuts and deepest overburden deposits.The concrete tunnel structure is being founded on bedrock consisting of a gypsiferous dolomite containing thick layers and lenses of essentially pure gypsum. Within the upper broken zone of the bedrock and some thin pervious lenses of sand and gravel immediately overlying the bedrock is an aquifer zone which is a major source of groundwater. Prior to construction, the piezometric level in this aquifer was approximately at the ground surface. The groundwater level in the aquifer zone had to be drawn down during construction and must be controlled throughout the life of the structure to provide for the stability of the overburden slopes. At the same time, the gypsum beneath the tunnel structure will be maintained intact by a drainage scheme which essentially isolates the rock beneath the structure from future groundwater flow, thereby precluding any significant solutioning of the gypsum.
The Drained Strength of Granular Material
Authors: Barden L. , Proctor D. C.
Published: July 2008

Using the stress dilatancy relation R = DK, the drained strength of granular material is separated into its dilatant and frictional components. The factors influencing the value of 1 ≤ D ≤ 2 and Kμ ≤ K ≤ Kev are assessed theoretically, and experimental confirmation is provided from tests mainly on River Welland sand. These tests include five different sample geometries, and cell pressures up to 1000 p.s.i. (70.3 kg/cm2). The failure criterion is seen to be contained between two limiting types of behavior relevant to dense and loose assemblies. The main ambiguity exists in the case of axisymmetric extension when the strength is seen to be influenced by the sample boundary conditions.
The Microstructure of Dispersed and Flocculated Samples of Kaolinite, Illite, and Montmorillonite
Authors: Sides Geoffrey , Barden Laing
Published: July 2008

Samples of kaolinite, illite, and montmorillonite were consolidated from slurries containing chemical dispersant and flocculating agents. The resulting microstructures of the six clays so produced have been studied in the scanning electron microscope, following a preliminary investigation of the problems of sample disturbance during preparation for electron microscopy. It was seen that dispersed and salt-flocculated structures were formed in the illite clays as a result of their high colloidal activity, but that the inactive kaolinite was relatively insensitive to structural effects. The structures of these artificial clays are compatible with the limited results published on undisturbed natural clays. The small size of the montmorillonite particles led to difficulties in the preparation and scanning operations and no conclusions can be drawn for this clay.
The Influence of Structural Rigidity on the Foundation Loads of the CN Tower, Edmonton
Authors: DeJong J. , Morgenstern N. R.
Published: July 2008

Detailed observation on settlements during construction of the CN Tower in Edmonton has afforded the opportunity of calculating the influence of the settlements on the distribution of foundation loads for an actual three-dimensional frame structure. These calculations have been carried out using the computer program ICES-STRUDL II. It is shown that in performing a soil–structure interaction analysis, the variation in structural rigidity with story height cannot be ignored when settlements occur during the construction period. Moreover, the distortions of a real structural frame due to small differential settlements can generate reactions of appreciable magnitude. As much as 39.4% of the basic load action on a footing beneath the CN Tower has been generated by a local maximum differential settlement which never exceeded 1.4 cm.
Variation in Undrained Shearing Strength by Semiconfined Tests
Authors: DeLory F. A. , Lai H-W.
Published: July 2008

The undrained shearing strength of Welland clay is determined over a range of sample orientation of 180° by the use of semiconfined compression tests that limit failure to one direction, but allow failure on any plane in that direction. It is shown that the undrained shearing strength is very nearly symmetrical about i = 90° and that the Bjerrum-Kenney hypothesis of greatest resistance to shearing stress in the direction of greatest shearing stress during consolidation is nearly so for Welland clay, but the two are slightly out of phase. For the soil tested, semiconfined tests yield undrained shearing strengths about 20% greater than unconfined compression tests.
The Effect of Sampling on the Undrained Soil Properties of a Leda Soil
Authors: Raymond Gerald P. , Townsend David L. , Lojkasek Miroslav J
Published: July 2008

The comparison of consolidated undrained triaxial results on sensitive Leda clay sampled by six different sampling methods is presented. The results indicate that the failure index, represented by the axial stress difference as a fraction of the axial failure stress difference against strain plots, are widely different at very low consolidation pressures, but are similar and approximate to the results from block samples as the consolidation pressure is increased. The pore pressure coefficient A appears to be independent of the sampling method and remains remarkably consistent throughout any test (up to failure) except where the confining pressure is very low or above the preconsolidation pressure.Routine commercial sampling methods (including laboratory preparation) using 50-mm diameter samples were found to partially destroy the cementation bonds, causing a decrease in strength at low confining pressures and an unsafe increase in strength at medium confining pressures. This trend is decreased by better sampling.
Hydrologic Characteristics and Response of Fractured Till and Clay Confining a Shallow Aquifer
Authors: Grisak G. E. , Cherry J. A.
Published: July 2008

Fractures in glacial till and glaciolacustrine clay were observed in excavations up to 20 ft (6.1 m) in depth and in drill cores at the Whiteshell Nuclear Research Establishment (WNRE) in southeastern Manitoba. The fractures are characteristically coated with carbonate and oxide precipitates, which indicate groundwater movement through the fractures. The fractures impart an effective bulk hydraulic conductivity to the clay–loam till and lacustrine clay, as evidenced by tritium tracer experiments and piezometer responses in the till and clay to pumping of an underlying sandy aquifer.The intergranular hydraulic conductivity of clay–loam till and glaciolacustrine clay in the Interior Plains, as determined from laboratory consolidation test data, is in the range of 2 × 10−10 to 9 × 10−11 ft s−1 (6 × 10−9 to 2.7 × 10−9 cm s−1). The bulk hydraulic conductivity of the fractured clay–loam till at WNRE, as determined from finite-element mathematical modeling, is about 6 × 10−9 ft s−1 (1.8 × 10−7 cm s−1). The model value represents the effective hydraulic conductivity imparted to the till by the fractures.Seven pumping tests, ranging in duration from 8.75 to 120 h were conducted on the sandy aquifer and drawdown data in the aquifer were analyzed to obtain the hydraulic conductivity and storativity of the aquifers.A 32 day pumping test on the aquifer showed that many of the piezometers in the till and clay respond quickly and strongly to the aquifer drawdown, while others show no noticeable response. The responding piezometers intersect open fractures whereas the others do not. Analysis of the piezometer drawdowns during the long-term pumping test using the Neuman and Witherspoon ‘ratio’ method indicates that the rapid piezometer drawdowns in the confining layers can be accounted for by assigning specific storativity values in the range of 1 × 10−5 to 5 × 10−6 ft−1 (3 × 10−5 to 1.5 × 10−5 m−1) to the clay–loam till and lacustrine clay. These values are typical of fractured rock. If intergranular specific storage values are used, the calculated piezometer drawdowns are very small or negligible.
Pore Water Expulsion during Freezing
Authors: McRoberts Edward C , Morgenstern Norbert R.
Published: July 2008

When a freezing front advances through a saturated soil water may either be expelled or attracted to the freezing front depending upon soil type, stress level, and rate of freezing. Experimental evidence is considered which shows that coarse-grained sandy soils expel water under most conditions while fine grained soils can be made to expel water only at higher overburden pressures. A solution for the excess pore pressures that can be generated due to impeded drainage by pore water expulsion in an open system is presented.
New Method for Measurement of Lateral Earth Pressure in Cohesive Soils
Authors: Massarsch K. Rainer
Published: July 2008

A new method is described by which the total lateral stress in cohesive soils can be measured. When used in combination with pore pressure measurements, the lateral effective stress, the stress change, and the coefficient of lateral earth pressure at rest, K0, can be calculated. The basic concept of the earth pressure cell and its installation, as described in this report, are simple.
Large Scale Laboratory Direct Shear Tests on Ice
Authors: Roggensack W. D.
Published: July 2008

This paper presents the results of a series of large scale direct shear tests performed on lake ice. Test specimens were oriented with the principal stresses acting in the plane of the ice sheet, approximately normal to the long axes of the columnar crystals. Sample dimensions were large in comparison with mean crystal diameter, reducing the possibility of deviations introduced by size effects. Although a number of assumptions are made concerning stress conditions at failure, results for uniform, artificially ‘seeded’ test pond ice indicate a failure mechanism that is frictional and consistent with triaxial test data reported elsewhere. Post-peak shear resulted in the formation of a distinct failure zone that also displayed a frictional response. The direct shear test described is robust and simple, does not require elaborate sample preparation, and may present an alternative method of strength determination for ice mechanics problems where the shear box configuration duplicates field stress conditions and constraints.
Snow Creep: Its Engineering Problems and Some Techniques and Results of Its Investigation
Authors: Mathews W. H. , Mackay J. R.
Published: July 2008

Investigations have been undertaken on aspects of the slow creep of the snow pack on mountain slopes in southern British Columbia. Studied particularly were (1) the rate of slip of the basal layer of snow on its substratum, (2) the pressures applied by the creeping snow pack on some stationary obstacles, and (3) the regional and the year-to-year variations of such pressures. Simple, relatively inexpensive equipment and methods have been developed to explore these problems. These indicate, for example, basal creep velocities up to 90 cm/winter season on very steep slopes, and pressures in the order of 0.5 kg/cm2 under extreme conditions. These studies lead to guidelines for future site investigations of areas subject to snow creep.
An Analysis of the Performance of a Warm-oil Pipeline in Permafrost, Inuvik, N.W.T.
Authors: Morgenstern Norbert R. , Nixon John F.
Published: July 2008

The data collected at a warm-oil test pipeline at Inuvik. N.W.T. are analyzed making use of the theory of thaw–consolidation proposed by Morgenstern and Nixon. The observed pore pressures, settlements, and rate of melting in the thawing permafrost foundation have been compared with their corresponding theoretical predictions. Bearing in mind the natural variability of ice-rich permafrost deposits, the agreement between prediction and observation is extremely encouraging. As the data collected at this test facility form the only completely documented case history of a thawing foundation in permafrost published to date, this comparison between theory and actual performance is valuable in establishing a level of confidence in the application of the theory of thaw–consolidation.
Terrain Evaluation of the Dempster Highway across the Eagle Plain and along the Richardson Mountains, Yukon Territory
Authors: Richardson Neil W. , Sauer E. Karl
Published: July 2008

A detailed terrain classification was carried out as part of a study on the Dempster Highway from Mile 166 to Mile 290.5, the Yukon–Northwest Territories Border. The objective was to establish a rational basis for field testing and subsurface exploration programs in the future and the evaluation of the potential effects upon the physical environment of the construction of highways and other transportation facilities in the Arctic, on terrain composed of sedimentary rocks which have not been glaciated. Terrain units were established on the basis of geology, vegetation, topography, and patterned ground. The subsurface sediments were mapped mainly as outcrops of weathered shale and sandstone. The sandstone was found to be the most stable foundation and borrow material. The shale was found to be mainly clay with high ice contents near the surface, and was observed to be very unstable when thawed. A number of plant communities, which differed significantly from a geotechnical point of view, were identified.
Thermal Conductivity of Some Ice-rich Permafrost Soils
Authors: Slusarchuk W. A. , Watson G. H.
Published: July 2008

Values are presented for the thermal conductivity of frozen and thawed ice rich permafrost soils from Inuvik, Northwest Territories, measured under field and laboratory conditions with a cylindrical heat source. Samples were shipped to Ottawa, Canada, in the frozen condition at temperatures ranging from –5 to –70 °C. It was found that temperature of shipping and repositioning of the probe between measurements had no statistically significant effect on results. The dependence of thermal conductivity on bulk unit weight and dry unit weight is given for both frozen and thawed samples. Measured thermal conductivities were found to be in good agreement with other values obtained for similar soils and corresponding unit weight and water content.
Strength Parameters for Permanent Slopes in Champlain Sea Clays
Authors: Mitchell R. J.
Published: July 2008

From consideration of the stress paths and boundary conditions generally applicable to earth slope stability problems it is concluded that long term slope stability analyses should not be based solely on strength data obtained from strain controlled drained triaxial tests (C.I.D. or C.A.D. tests). In particular it is shown that the brittle, time dependent, and anisotropic strength data obtained from such tests on Champlain Sea clay may not be relevant to slope stability problems. Appropriate sampling and testing procedures, design factors of safety, and the possibility of progressive failure are discussed with reference to documented field observations.
Quelques caractéristiques géotechniques des dépôts d'argile de la baie James: les coulées d'argile de Fort Rupert, Québec
Authors: Ballivy G. , Loiselle A. A. , Pouliot G.
Published: July 2008

The marine and lacustrine clay deposits of the James Bay area in Northwestern Quebec are described as a function of their origin, modes of deposition, and identifying characteristics. The stratigraphic and geotechnical parameters of the Fort Rupert marine clays are given in view of elaborating on case histories of regional slides. Based on these parameters and on the results of a laboratory experiment on four samples, the effect of pore pressure buildup on the triggering of a slide and on the progressive development of failure is described.
Improving Low Temperature Compaction of a Granular Soil
Authors: Alkire B. D. , Haas W. M. , Kaderabek T. J.
Published: July 2008

The dry density of a silty sand compacted at temperatures below 0 °C can be improved by using calcium chloride as an additive. Compaction tests at −7 °C were used to determine the effect of low amounts of calcium chloride on the moisture–density relationship of the test soil. Tests at 20 °C were conducted to provide a frame of reference for comparing the results obtained at the below freezing temperature. The results from the experimental work are analyzed by modeling the pore fluid as a simple eutectic system using the concepts of phase equilibria. The amount of ice in the pore fluid is shown to have a significant effect on the dry density of a soil compacted at temperatures below 0 °C.
First Canadian Geotechnical Colloquium: Foundation design approaches in permafrost areas
Authors: Nixon J. F.
Published: July 2008

The design of foundations in permafrost areas for large structures involves a knowledge of the thermal and mechanical properties of frozen soil. Recent creep data for frozen soils and ice are reviewed and some secondary (steady) creep relationships are established. A design approach for pile foundations in ice-rich permafrost is proposed and compared with available field case histories. The theory is found to provide reasonable predictions of pile settlements under load. It is suggested that the limitation of long-term pile settlements will control the design loadings.The thermal aspects of ventilated pad foundations are discussed and design curves are given for required pad and insulation thickness and ventilation capacity. Case histories indicate that in order to obtain the necessary ventilation capacity, forced air ventilation using electric fans is required for most practical situations.A settlement analysis for spread footings on permafrost is established and influence factors for settlement rate are given. Again it is apparent that allowable footing loads will be controlled by limiting long-term settlements, rather than by consideration of soil shear strength alone. Field data on the creep response of a tunnel in Fairbanks provide good correlation with theoretical predictions.
A limit equilibrium analysis of progressive failure in the stability of slopes
Authors: Law K. Tim , Lumb Peter
Published: July 2008

A limit equilibrium method of analysis is proposed for the study of progressive failure in slope stability under a long-term condition. Based on effective stresses, the formulation of the method is derived from consideration of force and moment equilibrium within the soil mass above a prospective slip surface. By dividing the soil mass into a number of vertical slices, recognition of local failure can be made. Once local failure takes place, post-peak strength is assumed to be operative. This then initiates a redistribution of interslice forces and leads to some further local failure. Thus realistic available strengths along the slip surface can be evaluated. This permits the definition of a final safety factor, which is expressed in terms of the actual available reserve of strength. The proposed method has been applied to three well documented case records and encouraging results have been obtained. Based on the assumption that post-peak strengths are given by a friction angle equal to the peak value and a zero cohesion, stability charts have been prepared for design purposes.