bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanism of Antiviral Drug Resistance of Vaccinia Virus: Identification of Residues in the Viral DNA Polymerase Conferring Differential Resistance to Antipoxvirus Drugs
Authors: Gammon Don B. , Snoeck Robert , Fiten Pierre , Krečmerová Marcela , Holý Antonín , De Clercq Erik , Opdenakker Ghislain , Evans David H. , Andrei Graciela
Published: October 2008

The acyclic nucleoside phosphonate (ANP) family of drugs shows promise as therapeutics for treating poxvirus infections. However, it has been questioned whether the utility of these compounds could be compromised through the intentional genetic modification of viral sequences by bioterrorists or the selection of drug resistance viruses during the course of antiviral therapy. To address these concerns, vaccinia virus (strain Lederle) was passaged 40 times in medium containing an escalating dose of (S)-1-[3-hydroxy-2-(phosphonomethoxypropyl)-2,6-diaminopurine [(S)-HPMPDAP], which selected for mutant viruses exhibiting a ∼15-fold-increased resistance to the drug. (S)-HPMPDAP-resistant viruses were generated because this compound was shown to be one of the most highly selective and effective ANPs for the treatment of poxvirus infections. DNA sequence analysis revealed that these viruses encoded mutations in the E9L (DNA polymerase) gene, and marker rescue studies showed that the phenotype was produced by a combination of two (A684V and S851Y) substitution mutations. The effects of these mutations on drug resistance were tested against various ANPs, both separately and collectively, and compared withE9LA314T and A684V mutations previously isolated using selection for resistance to cidofovir, i.e., (S)-1-[3-hydroxy-2-(phosphonomethoxypropyl)cytosine]. These studies demonstrated a complex pattern of resistance, although as a general rule, the double-mutant viruses exhibited greater resistance to the deoxyadenosine than to deoxycytidine nucleotide analogs. The S851Y mutant virus exhibited a low level of resistance to dCMP analogues but high-level resistance to dAMP analogues and to 6-[3-hydroxy-2-(phosphonomethoxy)propoxy]-2,4-diaminopyrimidine, which is considered to mimic the purine ring system. Notably, (S)-9-[3-hydroxy-2-(phosphonomethoxy)propyl]-3-deazaadenine retained marked activity against most of these mutant viruses. In vitro studies showed that the A684V mutation partially suppressed a virus growth defect and mutator phenotype created by the S851Y mutation, but all of the mutant viruses still exhibited a variable degree of reduced virulence in a mouse intranasal challenge model. Infections caused by these drug-resistant viruses in mice were still treatable with higher concentrations of the ANPs. These studies have identified a novel mechanism for the development of mutator DNA polymerases and provide further evidence that antipoxviral therapeutic strategies would not readily be undermined by selection for resistance to ANP drugs.
Immunomic Analysis of the Repertoire of T-Cell Specificities for Influenza A Virus in Humans
Authors: Assarsson Erika , Bui Huynh-Hoa , Sidney John , Zhang Qing , Glenn Jean , Oseroff Carla , Mbawuike Innocent N. , Alexander Jeff , Newman Mark J. , Grey Howard , Sette Alessandro
Published: October 2008

Continuing antigenic drift allows influenza viruses to escape antibody-mediated recognition, and as a consequence, the vaccine currently in use needs to be altered annually. Highly conserved epitopes recognized by effector T cells may represent an alternative approach for the generation of a more universal influenza virus vaccine. Relatively few highly conserved epitopes are currently known in humans, and relatively few epitopes have been identified from proteins other than hemagglutinin and nucleoprotein. This prompted us to perform a study aimed at identifying a set of human T-cell epitopes that would provide broad coverage against different virus strains and subtypes. To provide coverage across different ethnicities, seven different HLA supertypes were considered. More than 4,000 peptides were selected from a panel of 23 influenza A virus strains based on predicted high-affinity binding to HLA class I or class II and high conservancy levels. Peripheral blood mononuclear cells from 44 healthy human blood donors were tested for reactivity against HLA-matched peptides by using gamma interferon enzyme-linked immunospot assays. Interestingly, we found that PB1 was the major target for both CD4+and CD8+T-cell responses. The 54 nonredundant epitopes (38 class I and 16 class II) identified herein provided high coverage among different ethnicities, were conserved in the majority of the strains analyzed, and were consistently recognized in multiple individuals. These results enable further functional studies of T-cell responses during influenza virus infection and provide a potential base for the development of a universal influenza vaccine.
Herpes Simplex Virus ICP0 Promotes both Histone Removal and Acetylation on Viral DNA during Lytic Infection
Authors: Cliffe Anna R. , Knipe David M.
Published: October 2008

During lytic infection, the genome of herpes simplex virus 1 (HSV-1) is associated with limited levels of histones but does not form a regular repeating nucleosomal structure. However, the previous observation that chromatin remodeling factors are recruited into viral replication compartments indicates that chromatin remodeling plays a role in HSV-1 gene expression and DNA replication. In this study we demonstrate the presence of histone H3 on HSV-1 DNA early in infection at levels equivalent to those found on a cellular gene. The proportion of viral DNA associated with histone H3 decreases at later times postinfection, independently of either viral DNA replication or transcription. We demonstrate that an immediate-early protein, infected cell protein 0 (ICP0), is required for both a reduction in the proportion of HSV-1 DNA associating with histone H3 and an increase in histone acetylation. This study provides evidence that ICP0 directly alters the chromatin structure of the HSV-1 genome during lytic infection, and this system will serve as a useful model for the reduction of histone load in higher eukaryotes.
Bovine-Like Coronaviruses Isolated from Four Species of Captive Wild Ruminants Are Homologous to Bovine Coronaviruses, Based on Complete Genomic Sequences
Authors: Alekseev Konstantin P. , Vlasova Anastasia N. , Jung Kwonil , Hasoksuz Mustafa , Zhang Xinsheng , Halpin Rebecca , Wang Shiliang , Ghedin Elodie , Spiro David , Saif Linda J.
Published: October 2008

We sequenced and analyzed the full-length genomes of four coronaviruses (CoVs), each from a distinct wild-ruminant species in Ohio: sambar deer (Cervus unicolor), a waterbuck (Kobus ellipsiprymnus), a sable antelope (Hippotragus niger), and a white-tailed deer (Odocoileus virginianus). The fecal samples from the sambar deer, the waterbuck, and the white-tailed deer were collected during winter dysentery outbreaks and sporadic diarrhea cases in 1993 and 1994 (H. Tsunemitsu, Z. R. el-Kanawati, D. R. Smith, H. H. Reed, and L. J. Saif, J. Clin. Microbiol. 33:3264-3269, 1995). A fecal sample from a sable antelope was collected in 2003 from an Ohio wild-animal habitat during the same outbreak when a bovine-like CoV from a giraffe (GiCoV) was isolated (M. Hasoksuz, K. Alekseev, A. Vlasova, X. Zhang, D. Spiro, R. Halpin, S. Wang, E. Ghedin, and L. J. Saif, J. Virol. 81:4981-4990, 2007). For two of the CoVs (sambar deer and waterbuck), complete genomes from both the cell culture-adapted and gnotobiotic-calf-passaged strains were also sequenced and analyzed. Phylogenetically, wild-ruminant CoVs belong to group 2a CoVs, with the closest relatedness to recent bovine CoV (BCoV) strains. High nucleotide identities (99.4 to 99.6%) among the wild-ruminant strains and recent BCoV strains (BCoV-LUN and BCoV-ENT, isolated in 1998) further confirm the close relatedness. Comparative genetic analysis of CoVs of captive wild ruminants with BCoV strains suggests that no specific genomic markers are present that allow discrimination between the bovine strains and bovine-like CoVs from captive wild ruminants; furthermore, no specific genetic markers were identified that defined cell cultured or calf-passaged strains or the host origin of strains. The results of this study confirm prior reports of biologic and antigenic similarities between bovine and wild-ruminant CoVs and suggest that cattle may be reservoirs for CoVs that infect captive wild ruminants or vice versa and that these CoVs may represent host range variants of an ancestral CoV.
The Secreted Form of Respiratory Syncytial Virus G Glycoprotein Helps the Virus Evade Antibody-Mediated Restriction of Replication by Acting as an Antigen Decoy and through Effects on Fc Receptor-Bearing Leukocytes
Authors: Bukreyev Alexander , Yang Lijuan , Fricke Jens , Cheng Lily , Ward Jerrold M. , Murphy Brian R. , Collins Peter L.
Published: October 2008

Respiratory syncytial virus (RSV) readily infects and reinfects during infancy and throughout life, despite maternal antibodies and immunity from prior infection and without the need for significant antigenic change. RSV has two neutralization antigens, the F and G virion glycoproteins. G is expressed in both membrane-bound (mG) and secreted (sG) forms. We investigated whether sG might act as a decoy for neutralizing antibodies by comparing the in vitro neutralization of wild-type (wt) RSV versus recombinant mG RSV expressing only mG. wt RSV indeed was less susceptible than mG RSV to monovalent G-specific and polyvalent RSV-specific antibodies, whereas susceptibility to F-specific antibodies was equivalent. This difference disappeared when the virus preparations were purified to remove sG. Thus, sG appears to function as a neutralization decoy. We evaluated this effect in vivo in mice by comparing the effects of passively transferred antibodies on the pulmonary replication of wt RSV versus mG RSV. Again, wt RSV was less sensitive than mG RSV to G-specific and RSV-specific antibodies; however, a similar difference was also observed with F-specific antibodies. This confirmed that sG helps wt RSV evade the antibody-dependent restriction of replication but indicated that in mice, it is not acting primarily as a decoy for G-specific antibodies, perhaps because sG is produced in insufficient quantities in this poorly permissive animal. Rather, we found that the greater sensitivity of mG versus wt RSV to the antiviral effect of passively transferred RSV antibodies required the presence of inflammatory cells in the lung and was Fcγ receptor dependent. Thus, sG helps RSV escape the antibody-dependent restriction of replication via effects as an antigen decoy and as a modulator of leukocytes bearing Fcγ receptors.
Chlorovirus-Mediated Membrane Depolarization ofChlorellaAlters Secondary Active Transport of Solutes
Authors: Agarkova Irina , Dunigan David , Gurnon James , Greiner Timo , Barres Julia , Thiel Gerhard , Van Etten James L.
Published: October 2008

Paramecium bursariachlorella virus 1 (PBCV-1) is the prototype of a family of large, double-stranded DNA, plaque-forming viruses that infect certain eukaryotic chlorella-like green algae from the genusChlorovirus. PBCV-1 infection results in rapid host membrane depolarization and potassium ion release. One interesting feature of certain chloroviruses is that they code for functional potassium ion-selective channel proteins (Kcv) that are considered responsible for the host membrane depolarization and, as a consequence, the efflux of potassium ions. This report examines the relationship between cellular depolarization and solute uptake. Annotation of the virus hostChlorellastrain NC64A genome revealed 482 putative transporter-encoding genes; 224 are secondary active transporters. Solute uptake experiments using seven radioactive compounds revealed that virus infection alters the transport of all the solutes. However, the degree of inhibition varied depending on the solute. Experiments with nystatin, a drug known to depolarize cell membranes, produced changes in solute uptake that are similar but not identical to those that occurred during virus infection. Therefore, these studies indicate that chlorovirus infection causes a rapid and sustained depolarization of the host plasma membrane and that this depolarization leads to the inhibition of secondary active transporters that changes solute uptake.
Varicella-Zoster Virus IE62 Protein Utilizes the Human Mediator Complex in Promoter Activation
Authors: Yang Min , Hay John , Ruyechan William T.
Published: October 2008

The varicella-zoster virus (VZV) major transactivator, IE62, is involved in the expression of all kinetic classes of VZV genes and can also activate cellular promoters, promoters from heterologous viruses, and artificial promoters containing only TATA elements. A key component of the mechanism of IE62 transactivation is an acidic activation domain comprising the N-terminal 86 amino acids of IE62. However, the cellular target of this N-terminal acidic activation is unknown. In the work presented here, we show that the IE62 activation domain targets the human Mediator complex via the Med25 (ARC92) subunit and that this interaction appears to be fundamental for transactivation by the IE62 activation domain. In contrast, the Med23 subunit (Sur2/TRAP150β/DRIP130/CRSP130) of the Mediator complex is not essential for IE62-mediated activation. Further, the IE62 activation domain appears to selectively interact with a form of the Mediator complex lacking CDK8. Chromatin immunoprecipitation experiments showed that IE62 stimulates recruitment of Mediator to an IE62-responsive model promoter. Finally, immunofluorescence microscopy of VZV-infected cells demonstrated intranuclear translocation of the Mediator complex to viral replication compartments. These studies suggest that Mediator is an essential component for efficient VZV gene expression.
Initial B-Cell Responses to Transmitted Human Immunodeficiency Virus Type 1: Virion-Binding Immunoglobulin M (IgM) and IgG Antibodies Followed by Plasma Anti-gp41 Antibodies with Ineffective Control of Initial Viremia
Authors: Tomaras Georgia D. , Yates Nicole L. , Liu Pinghuang , Qin Li , Fouda Genevieve G. , Chavez Leslie L. , Decamp Allan C. , Parks Robert J. , Ashley Vicki C. , Lucas Judith T. , Cohen Myron , Eron Joseph , Hicks Charles B. , Liao Hua-Xin , Self Steven G. , Landucci Gary , Forthal Donald N. , Weinhold Kent J. , Keele Brandon F. , Hahn Beatrice H. , Greenberg Michael L. , Morris Lynn , Karim Salim S. Abdool , Blattner William A. , Montefiori David C. , Shaw George M. , Perelson Alan S. , Haynes Barton F.
Published: October 2008

A window of opportunity for immune responses to extinguish human immunodeficiency virus type 1 (HIV-1) exists from the moment of transmission through establishment of the latent pool of HIV-1-infected cells. A critical time to study the initial immune responses to the transmitted/founder virus is the eclipse phase of HIV-1 infection (time from transmission to the first appearance of plasma virus), but, to date, this period has been logistically difficult to analyze. To probe B-cell responses immediately following HIV-1 transmission, we have determined envelope-specific antibody responses to autologous and consensus Envs in plasma donors from the United States for whom frequent plasma samples were available at time points immediately before, during, and after HIV-1 plasma viral load (VL) ramp-up in acute infection, and we have modeled the antibody effect on the kinetics of plasma viremia. The first detectable B-cell response was in the form of immune complexes 8 days after plasma virus detection, whereas the first free plasma anti-HIV-1 antibody was to gp41 and appeared 13 days after the appearance of plasma virus. In contrast, envelope gp120-specific antibodies were delayed an additional 14 days. Mathematical modeling of the earliest viral dynamics was performed to determine the impact of antibody on HIV replication in vivo as assessed by plasma VL. Including the initial anti-gp41 immunoglobulin G (IgG), IgM, or both responses in the model did not significantly impact the early dynamics of plasma VL. These results demonstrate that the first IgM and IgG antibodies induced by transmitted HIV-1 are capable of binding virions but have little impact on acute-phase viremia at the timing and magnitude that they occur in natural infection.
Sequence Conservation and Differential Expression of Marek's Disease Virus MicroRNAs
Authors: Morgan Robin , Anderson Amy , Bernberg Erin , Kamboj Sachin , Huang Emily , Lagasse Grace , Isaacs Grace , Parcells Mark , Meyers Blake C. , Green Pamela J. , Burnside Joan
Published: October 2008

Marek's disease virus (MDV), a herpesvirus that causes a lymphoproliferative disorder in chickens, encodes a number of microRNAs derived primarily from two locations in the MDV genome. One cluster of microRNA genes flanks the
meq
oncogene, and a second cluster is found within the latency-associated transcript (LAT) region. The sequences of MDV microRNAs from a collection of field and reference strains with various levels of virulence were compared and found to be highly conserved. However, microRNAs from the
meq
cluster were detected at higher levels in lymphomas caused by a form of the virus designated very virulent plus (vv+; strain 615K, also known as T. King) than in those caused by a less virulent (very virulent [vv]) form (RB1B). For example, levels of mdv1-miR-M4, which shares a seed sequence with miR-155, a microRNA implicated in B-cell lymphoma, were threefold higher and levels of mdv1-miR-M2*/3p were more than sixfold higher in vv+ MDV-induced tumors than in vv MDV-induced tumors. In contrast, levels of the microRNAs from the LAT cluster were equivalent in tumors produced by vv and vv+ strains. Additionally, mdv1-miR-M4 is the MDV microRNA most highly expressed in tumors, where it accounts for 72% of all MDV microRNAs, as determined by deep sequencing. These data suggest that the
meq
cluster microRNAs play an important role in the pathogenicity of MDV.
Human Immunodeficiency Virus Type 1 Superinfection Occurs despite Relatively Robust Neutralizing Antibody Responses
Authors: Blish Catherine A. , Dogan Ozge C. , Derby Nina R. , Nguyen Minh-An , Chohan Bhavna , Richardson Barbra A. , Overbaugh Julie
Published: October 2008

Superinfection by a second human immunodeficiency virus type 1 (HIV-1) strain indicates that gaps in protective immunity occur during natural infection. To define the role of HIV-1-specific neutralizing antibodies (NAbs) in this setting, we examined NAb responses in 6 women who became superinfected between ∼1 to 5 years following initial infection compared to 18 women with similar risk factors who did not. Although superinfected individuals had less NAb breadth than matched controls at ∼1 year postinfection, no significant differences in the breadth or potency of NAb responses were observed just prior to the second infection. In fact, four of the six subjects had relatively broad and potent NAb responses prior to infection by the second strain. To more specifically examine the specificity of the NAbs against the superinfecting virus, these variants were cloned from five of the six individuals. The superinfecting variants did not appear to be inherently neutralization resistant, as measured against a pool of plasma from unrelated HIV-infected individuals. Moreover, the superinfected individuals were able to mount autologous NAb responses to these variants following reinfection. In addition, most superinfected individuals had NAbs that could neutralize their second viral strains prior to their reinfection, suggesting that the level of NAbs elicited during natural infection was not sufficient to block infection. These data indicate that preventing infection by vaccination will likely require broader and more potent NAb responses than those found in HIV-1-infected individuals.
VP26 of White Spot Syndrome Virus Functions as a Linker Protein between the Envelope and Nucleocapsid of Virions by Binding with VP51
Authors: Wan Qiang , Xu Limei , Yang Feng
Published: October 2008

The envelopment of the nucleocapsid is an important step in white spot syndrome virus (WSSV) assembly. Previous studies showed that VP26, a major envelope protein of WSSV, can interact with viral nucleocapsid. In this study, using the biotin label transfer technique, we found that the biotin label was transferred from Bio-rVP26 to the viral capsid protein VP51 or from Bio-MBP-VP51 to VP26. Far-Western analyses provided further evidence for direct interaction between VP26 and VP51. Therefore, we conclude that VP26 functions as a matrix-like linker protein between the viral envelope and nucleocapsid, which suggests that VP26 is a key factor in the envelopment of WSSV virion.
Pangnirtung water reservoir: geotechnical aspects
Authors: Smith L. B. , Notenboom W. G. , Campbell M. , Cheema S. , Smyth T.
Published: October 2008

This paper outlines the geotechnical aspects associated with the design and construction of an earthworks water reservoir excavated in ice-rich permafrost in the community of Pangnirtung, N.W.T. The reservoir was constructed by blasting, excavating, and placing frozen silty sand to form the reservoir berms during the winter. The work involved the excavation of about 140 000 m3 of material. The paper outlines the major geotechnical concerns identified during design and the measures used to deal with them. Observations made during subsequent construction of the reservoir are presented. Key words: permafrost, excavation, construction, water reservoirs, blasting.
Long-term settlement of model rock-socketed piers
Authors: Horvath Robert G. , Chae K-J.
Published: October 2008

Very little information is available concerning the long-term settlement behaviour of drilled pier foundations socketed into rock. This paper summarizes the results of laboratory investigations of the long-term settlement (creep) behaviour of model socketed pier foundations. The testing program included seven model piers constructed with different materials and different load-support conditions. The primary models were two small-diameter concrete piers constructed in soft shale. For all models tested the results indicated similarly shaped time–displacement curves, having two distinct regions. The initial portion of the curves represents a region of primary creep and the remaining portion represents a zone of secondary creep having a much lower rate of displacement. A comparison of short-term (1 day, which is a normal maximum duration of a full-scale load test) and long-term (200 days) settlements for the model piers showed an 84–245% increase in settlements. In addition, some information concerning load transfer with time in the model piers and available data from loading tests on large-scale socketed piers are included. Key words: socketed pier foundations, long-term settlement, creep model tests, soft rock.
Reliability analysis of foundation stability for gravity platforms in the North Sea
Authors: Wu Tien H. , Kjekstad Oddvar , Lee In-Mo , Lacasse Suzanne
Published: October 2008

The uncertainties encountered in the evaluation of foundation stability for four offshore gravity structures in the North Sea are reviewed. The uncertainties include those about the load, the material type, the material strength, and the analytical method. The means and coefficients of variations of these are used as inputs to compute the mean and coefficient of variation of the safety factor and the reliability index. The latter are used to assess the effect of various options in site exploration and strength measurement on foundation reliability. Key words: foundation, gravity platforms, offshore structures, probability, reliability, shear strength, site investigation, stability.
Rigid–plastic limit analysis of discontinuous media by a finite element method
Authors: Tamura T. , Pak R. Y. S.
Published: October 2008

This paper describes the formulation of a finite element method by which a limit analysis of a rigid–plastic medium with discontinuities can be performed. The Drucker–Prager criterion is adopted to describe the yielding of the medium, while the Mohr–Coulomb law is used to model the interface of the discontinuous velocity fields. Both associated and nonassociated flow rules are considered in the constitutive characterization. Results are presented to illustrate the influence of discontinuities on the bearing capacity of a surface foundation. Key words: bearing capacity, constitutive law, dilatancy, discontinuity, limit, plasticity, finite element analysis.
Capacité portante de pieux isolés dans les argiles sensibles: étude de cas par la méthode pénétrométrique
Authors: Roy Marius , Tanguay Luc
Published: October 2008

The penetrometer test has been used to determine the bearing capacity of driven and jacked-in single piles in sensitive clays. The cases presented in this paper were carried out on two sites with steel, concrete, and wooden piles. The bearing capacities calculated on the basis of the results of penetrometer tests show that this approach has a good potential and at the same time is simple and fast. It has been possible to obtain a calibration by a comparison with the loading tests carried out on each of the piles. Taking into account the low strength of some of our clays, experience has to be gained in order to adapt the lateral unit friction curves to our clays. This approach also has the advantage of allowing the determination of the bearing capacity of wooden piles and of taking into account the conical effect when determining the lateral friction component. Key words: penetrometer test, piles, bearing capacity, cohesive soils, point resistance, lateral friction, steel, concrete, wood. [Journal translation]
Pullout capacity of slab anchors in sand
Authors: Frydman S. , Shaham I.
Published: October 2008

The pullout capacity of slab anchors in homogeneous sand depends on several factors including the type and density of the sand, and the depth, size, inclination, and shape of the slab. Although numerous publications have reported results of pullout tests on small models and prototypes, the investigations described have generally been limited to a study of the effects of one or two of the above factors, and no attempt has been made to develop an integrated approach to the problem. This paper presents such an approach by reanalyzing the results of published experimental data as well as those of a series of pullout tests performed on prototype slabs placed at various inclinations and depths in a dense sand profile. A simple theoretical expression is found to reasonably predict the pullout capacity of a continuous, horizontal slab as a function of depth-to-width ratio. Factors to account for shape, and inclination, are then established leading to expressions for the estimation of pullout capacity of any slab anchor. Key words: anchors, field tests, model tests, pullout capacity, sand, slabs, plates.
Analysis of flexible drains in Changi reclamation
Authors: Karunaratne G. P. , Tan S. A. , Lee S. L. , Choa V.
Published: October 2008

Vertical drains and surcharge were used to accelerate the consolidation of soft marine clay under the second runway at the Changi Airport site. To study this problem further, the consolidation of a strip of layered clay deposit under a large reclamation is analysed as a two-dimensional problem in accordance with Biot's theory using the finite difference method. The soil with vertical drains is replaced with an equivalent soil having an enhanced vertical hydraulic conductivity obtained by equating the surface settlement of the real soil with that of the equivalent soil. The soil modulus and the hydraulic conductivity of the real soil are varied with the prevailing effective stress in the soil. The operating soil parameters determined by back analysing the field observations in a pilot test were then utilized to predict the behaviour of the main works. Soil displacement at any point in the plane of strain could be determined within a reasonable accuracy. As the equivalent soil is obtained by equating the average degree of consolidation, pore pressures cannot be predicted accurately within the drain area. However, the trend of pore pressure variation across the test site is implied by the analysis. The trend showed that pore pressures outside the drain area are found to influence the settlement and pore pressure inside the drain area, causing retardation in the consolidation of the drain area. Key words: Biot's analysis, consolidation, flexible drains, numerical analysis, soft clay.
Modélisation thermo-hydro-mécanique d'un sol par méthode mixte
Authors: Saix C. , Jouanna P.
Published: October 2008

Applications for the thermic exploitation of the subsoil are numerous and diversified. The knowledge of hydric and thermic phenomena may be considered to be satisfactory in many cases, but it is not so when mechanical phenomena are coupled with hydric and thermic phenomena. In order to arrive at the thermo-hydro-mechanical phenomena in unsaturated soils, it is proposed to approach the problem by a "modelling by mixed method." This modelling is based on the iterative use of a mathematical model and a physical local model. The first step of iteration allows access, by means of the mathematical modes, to the evolution of the thermic and hydraulic state variables in the hypothesis of a soil with a solid nondeformable skeleton. The second step of iteration consists in transferring this evolution of the state variables on a sample of soil placed in a "thermic triaxial" and measuring the resulting evolution of the mechanical variables. This "modelling by mixed method" is validated by the study of a silty soil fill used for storing heat in unsaturated soils. Key words: unsaturated soils, thermo-hydro-mechanical, modelling, mixed method, triaxial, consolidation. [Journal translation]
The Pandemonium Creek rock avalanche, British Columbia
Authors: Evans S. G. , Clague John J. , Woodsworth G. J. , Hungr O.
Published: October 2008

In 1959, a rock spur became detached from the headwall of a cirque near Pandemonium Creek in the southern Coast Mountains of British Columbia. Approximately 5 × 106 m3 of blocky, gneissic quartz diorite debris travelled 9.0 km along a highly irregular path, descending a vertical distance of 2 km to the valley of South Atnarko River. The high mobility of the rock avalanche is manifested by superelevation in valley bends, two run-ups, and two right-angle changes in flow direction. This mobility is due, in part, to (1) peculiarities in the path of the landslide (lateral moraines, for example, funnelled and accelerated the debris) and (2) travel over a glacier below the detachment zone. Although most of the debris came to rest on the upper part of a fan at the mouth of Pandemonium Creek, one lobe traversed the fan and entered Knot Lakes, where it generated displacement waves that destroyed trees along the shore.Run-up and superelevation data indicate that the debris was moving between 81 and 100 m/s as it entered the run-up zone at Pandemonium Creek and 21–38 m/s in Pandemonium valley to the east. These velocities were analysed by applying the dynamic model of H.J. Körner (Rock Mechanics, 1976, 8: 225–256) to the path of the landslide. The analysis suggests that the rock avalanche had two phases: a very rapid initial phase from detachment to the beginning of the run-up, and, following sudden energy losses at the run-up, a second phase involving much lower velocities.The Pandemonium Creek landslide is similar in many respects to much larger, highly mobile rock avalanches in other parts of the world, for example, Huascarán (Peru) and Little Tahoma Peak (Washington, U.S.A.). Although much less common than rockfalls and debris flows, rock avalanches are capable of far greater damage. This is a consequence of their size and the fact that they travel great distances at high velocities. The potential exists for other highly mobile landslides of the Pandemonium Creek type in the mountains of western Canada, highlighting the need for caution in the future development of this region. Key words: rock avalanche, dynamic analysis, mobile landslides, evaluation, run-up, superelevation, mountains.
Influence of placement method on the in situ density of hydraulic sand fills
Authors: Sladen J. A. , Hewitt K. J.
Published: October 2008

The range of densities achievable by hydraulic placement of sand straddles the boundary between values giving acceptable potential performance and those giving unacceptable potential performance. This has led to concerns over the safety of structures using hydraulic fills, such as the artificial drilling islands in the Canadian Beaufort Sea. Liquefaction failures of hydraulically placed sand have occurred at four or more of these islands. Until recently, the factors affecting in situ density were little understood. Data obtained from several artificial islands are presented and these are used to demonstrate the overwhelming influence of method of placement on in situ density. The possible reasons for this influence and the implications for design are discussed. Recommendations are made for research that, together with conclusions drawn in the paper, should allow hydraulic fills to be used with more confidence in the future. Key words: sand, hydraulic fill, liquefaction, cone penetration test.
Use of a tilting table to determine the basic friction angle of hard rock samples
Authors: Bruce I. G. , Cruden D. M. , Eaton T. M.
Published: October 2008

A tilting table can be used to determine the basic friction angle of a rock. Dolostone and quartzite sliders with natural and sanded surfaces move at similar angles on sanded plates of dolostone and quartzite. Friction angles measured from conventional direct shear tests on the same specimen are similar.When the natural or sanded sliders are tilted on polished plates, lower friction angles result: about 12° for quartzite and 16° for dolostone. The dolostone sliders leave a loose powder on the polished plates. If the powder is accumulated over successive slides, tilt angles for sliding increase to 30°. Friction angles on polished plates approach a minimum, the mineral friction angle, [Formula: see text], which represents the friction between the minerals making up the rock surfaces. The basic friction angle, [Formula: see text], is the sum of [Formula: see text] and the surface roughness produced by sanding.Tests of a new tilting table design suggest that basic friction angles should be determined with naturally surfaced sliders on plates wet lapped with No. 80 grit. Vibrations from the electric motor driving the table reduce measured friction angles by about 1°. Sliding angles increase up to 2° in very humid conditions. Key words: friction, rocks, tilting table, roughness, humidity, dolostone, quartzite, limestone.
Strength of frozen sand containing tetrahydrofuran hydrate
Authors: Parameswaran V. R. , Paradis M. , Handa Y. P.
Published: October 2008

Cylindrical samples of frozen sand containing tetrahydrofuran hydrate were tested under uniaxial compression at 267 K and strain rates between 10−6 and 10−3 s−1. In the low strain rate region the compressive strength of the samples was higher than that of frozen sand containing ice. For example, at 267 K and a strain rate of 10−6 s−1 the peak stress for the frozen sand containing hydrate was about 16 MPa, whereas the corresponding value for the frozen sand containing ice was only 10.5 MPa. The strain rate dependence of stress for the frozen sand containing hydrate was much smaller than that of frozen sand containing ice, so that at higher strain rates the compressive strengths of the two materials become almost the same. Key words: tetrahydrofuran hydrate, frozen sand, mechanical properties, compressive strength, creep behavior.
Use of thermal conductivity sensors to measure matric suction in the laboratory
Authors: Sattler Pamela , Fredlund D. G.
Published: October 2008

The measurement of soil suction is pivotal to the application of soil mechanics principles in geotechnical engineering practice related to unsaturated soils. Volume change, shear strength, and seepage analyses all require an understanding of the matric suction in the soil. This note summarizes the use of thermal conductivity sensors to measure matric suction in the laboratory. The thermal conductivity sensor is described along with its mode of operation. A brief description is given of the procedure for calibrating thermal conductivity sensors using a pressure plate apparatus. The measurement of matric suction can be performed in the laboratory on Shelby tube samples. The laboratory measurements of matric suction can be adjusted for the effect of overburden pressure in the field. The required equilibration time for suction measurements is discussed along with details of the test procedure. The applications of the measured suction values to design are briefly discussed.Key words: matric suction, negative pore-water pressure, thermal conductivity sensor, laboratory, undisturbed samples.
Utilization of compacted coal tailings as a structural fill
Authors: Indraratna B. , Gasson I. , Chowdhury R.N.
Published: October 2008

Detailed laboratory investigations were conducted on coal tailings produced at Westcliff Colliery, New South Wales, Australia. Geotechnical tests were conducted to determine the particle-size distribution, mineralogy, compaction characteristics, compressive strength (California bearing ratio), shear resistance, and collapse potential. The tests show that compacted tailings have good potential as effective fill for embankments, tailings dams, mine access roads, and pavements. Large-scale utilization of these tailings for rehabilitation of subsidence-affected areas and mine backfill is particularly encouraging. It is demonstrated that this waste material can be efficiently compacted to produce acceptable engineering properties over a wide range of water contents. Although the behaviour of one specific type of tailings cannot be generalized to the diverse composition of other coal tailings, the results of this study assist in the interpretation of geotechnical data associated with nonconventional fill. The use of geotextiles in the stabilization of tailings is presented. The effect of moisture content and the number of geotextile layers on the shear strength parameters is investigated, and the influence of geotextiles on the failure modes of triaxial specimens is also discussed. Key words : California bearing ratio, coal tailings, compaction, geotextiles, structural fill, triaxial testing.
On uncertainty evaluation of contaminant migration through clayey barriers
Authors: Honjo Yusuke , Thavaraj Thuraisamy
Published: October 2008

This paper presents a methodology to estimate parameters and to make predictions with quantified uncertainty for an advective–diffusive transport of nonreactive species and low-concentration reactive species through saturated porous media. The methodology is put in the framework of inverse and forward analyses. The maximum-likelihood method (or the weighted least square method) is employed in the inverse analysis, whereas the first-order second-moment method is used in the forward analysis. The methodology facilitates the quantification of uncertainty in the estimated parameters as well as in the predictions. A case study consisting of sets of laboratory tests and field data taken from the literature is used to demonstrate the capability of the proposed methodologies. It is generally recognized that the advective–diffusive transport of contaminants is a rather uncertain process in prediction; therefore the methodology proposed in this study should be useful for practising geotechnical engineers. Key words : statistical analysis, contaminant migration, diffusion, clay barrier, inverse analysis, waste disposal.
Modeling the performance of the Molikpaq
Authors: Altaee Ameir , Fellenius Bengt H.
Published: October 2008

A nonlinear, two-dimensional (plane-strain), monotonic and cyclic undrained finite element analysis is carried out to investigate the stability of the Molikpaq offshore structure at the Amauligak I-65 site in the Canadian Beaufort Sea. The stress–strain–strength response of the hydraulically placed sand is modeled using bounding-surface elastoplastic constitutive relations. The behavior of the sand in the field as well as in the laboratory is simulated by the constitutive relations using a single set of nine parameters. The Molikpaq structure was analyzed for up to 100 cycles of lateral cyclic ice loading in the interval 3–5 MN/m. The pore-water pressures computed at three different locations agree well with piezometer measurements made in the actual structure. The results of the study demonstrate the importance of analyzing the stability of the structure for cyclic loading rather than relying on conclusions derived from static analysis. Key words : analysis, cyclic loading, Molikpaq, sand fill retention, offshore structure.
Ultimate pullout resistance of single vertical anchors
Authors: Ghaly Ashraf , Hanna Adel
Published: October 2008

An investigation into the performance of single vertical screw anchors installed in sands is presented. Models were developed employing the limit equilibrium method of analysis to predict the uplift capacity of anchors installed into shallow, transition, and deep depths. An experimentally observed log-spiral rupture surface was used in the theoretical analysis. Shear stresses were calculated on the surface of rupture using Kötter's differential equation. Weight and shear factors for shallow and deep anchors are established to simplify the calculation of the uplift capacity from the theories developed. These factors are presented in simple graphs as functions of the angle of shearing resistance of the sand and the relative depth ratio of the anchor. The effect of sand overconsolidation resulting from the application of mechanical compaction was introduced by incorporating the overconsolidation ratio in the uplift capacity calculations. Comparisons between the theoretical values and the experimental results of the present investigation as well as field results reported in the literature showed good agreement. Key words : anchors, failure mechanism, limit equilibrium, overconsolidation ratio, theoretical analysis, uplift capacity.
Accelerated physical modelling of radioactive waste migration in soil
Authors: Zimmie T.F. , Mahmud M.B. , De A.
Published: October 2008

A 100 g-tonne geotechnical centrifuge was used to study the long-term migration of a contaminant and radioactive tracer through a saturated soil medium. The use of the centrifuge simulates the acceleration of traveltime in the prototype, which is N times larger than the model, by N2, where N is the desired g level. For a 5 h run at 60 g, the test modelled a migration time of about 2 years for a prototype 60 times larger than the small-scale model tested. Iodine 131 (I-131), used as the tracer, was injected onto the surface of the soil, and was allowed to migrate with a constant head of water through the saturated soil. End window Geiger–Mueller (G–M) tubes were used to measure the count rate of the radioactive tracer flowing through the soil. The time from the peak response of one G–M tube to the other denotes the traveltime between the two points in the flow domain. The results obtained using the radioactive tracer are in good agreement with the test performed on the same model setup using potassium permanganate as a tracer and with numerical flow net modelling. Radioactive tracers can be useful in the study of nonradioactive contaminants as well, offering a nonintrusive (nondestructive) method of measuring contaminant migration. Key words : contaminant transport, centrifuge modelling, radioactive waste, nondestructive measurement, waste disposal.
The effect of sample disturbance on laboratory properties of Lac du Bonnet granite
Authors: Martin C. Derek , Stimpson Brian
Published: October 2008

Laboratory properties of Lac du Bonnet granite samples collected at depths ranging from near-surface to 1000 m were established. The laboratory properties indicated that either the in situ properties were changing with depth or the samples were changing with depth. Comparison of P-wave velocities in the samples and in situ confirmed the latter, i.e., sample disturbance was affecting the laboratory properties. The strength of the damaged samples indicated that sample disturbance affected the cohesion of the material, not the frictional properties, and that the cohesion loss cannot be accounted for, by applying a confining stress. Sample disturbance started to affect the laboratory properties of Lac du Bonnet granite when the maximum far-field in situ stress exceeded about 10% of the unconfined compression strength. Key words : sample disturbance, core discing, cohesion, brittle rocks, damage, microcracks, stress-dependent Young's modulus.
Construction and characterization of a spray-ice pad, Tuktoyaktuk, Northwest Territories
Authors: Instanes Arne , Sego David C. , Addo Kofi
Published: October 2008

During the winter of 1990–1991, a field research program was undertaken to investigate the in situ properties of spray ice, since information on the mechanical and physical properties of undisturbed field-produced spray ice is scarce. The main objective of this research was to retrieve undisturbed field samples for laboratory characterization and to make field measurements to assist in studying the formation processes and physical properties after formation. For this purpose, a spray-ice pad was constructed in the freshwater Tuktoyaktuk Harbour, Northwest Territories, Canada. The 4.3 m thick pad was partly grounded in water depths of 3–6 m and had a maximum freeboard of 2.2 m. The spray-ice pad was constructed using a mobile spray-ice system placed on the first-year ice sheet. The ice production efficiency of the system was measured and found to give an ice content higher than 50%. A total of 11.8 m of cores of nonsaturated undisturbed spray ice were retrieved from three locations on the pad and transported to a cold room facility for density, shear wave velocity, and mechanical behavior testing. In addition, surface wave testing of the in situ spray ice and first-year ice was performed. This paper describes the field study and the methodologies employed to carry out this research. Key words : spray ice, construction, sampling, density, Rayleigh wave velocity.
Effective stress response of clay to undrained cyclic loading
Authors: Zergoun M. , Vaid Y.P.
Published: October 2008

The effective stress response of a natural marine clay to slow undrained symmetrical cyclic reversal in shear stress is presented. The effects of cyclic principal stress difference amplitude, cyclic principal effective stress ratio amplitude, initial direction of loading, and step increase in cyclic stress level on the clay stress–strain response are studied under stress conditions of the triaxial test. Characteristic behaviour patterns are identified in terms of effective stresses. Key words : clay, cyclic loading, effective stress, hysteretic work, loading direction, step loading.
Influence of fines on the collapse of loose sands
Authors: Pitman T.D. , Robertson P.K. , Sego D.C.
Published: October 2008

A study has been carried out to investigate the influence of fines and gradation on the skeletal collapse behaviour of loosely prepared sand samples. Loose sand samples, formed by moist tamping and consolidated to the same effective stress level, were prepared with varying percentages of both plastic and non-plastic fines (< 74 μm) and non-plastic fine sand (> 74 μm). Samples were isotropically consolidated and subjected to monotonic undrained triaxial compression. Results indicate that increased percentages of fines (< 74 μm) have a pronounced effect on the monotonic undrained behaviour at large strains (> 0.5%). This change is represented by a decreased strain softening behaviour and a shifting of the steady-state line. Variation of the gradation of the host sand appears to have little effect on the monotonic undrained behaviour. A supplemental study, involving use of the scanning electron microscope, was carried out to evaluate the findings of the test program in terms of sand fabric. Key words : collapse, monotonic undrained behaviour, scanning electron microscope, fabric.