bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical modifications of Bacillus subtilis tryptophanyl-tRNA synthetase
Authors: Xue Hong , Xue Yilong , Doublié Sylvie , Carter, Jr. Charles W
Published: April 2011

A concerted conformational change in Bacillus subtilis tryptophanyl-tRNA synthetase (TrpRS) was evident from previous fluorescence on the quenching of the single Trp residue Trp-92 in the 4FTrp-AMP complexed enzyme. In this study, chemical modifications of the B. subtilis TrpRS were employed to further characterize this conformational change, with the single Trp residue serving as a marker for monitoring the change. Modifications of the enzyme by means of the Trp-specific agent N-bromosuccinimide (NBS) or 3-bromo-3-methyl-2-(2-nitrophenylmercapto)-3H-indole (BNPS-skatole) inactivated the enzyme in accord with the essential role of Trp-92, as identified previously by site-directed mutagenesis. ATP sensitized TrpRS toward inactivation by NBS and BNPS-skatole, which suggested a conformational change that resulted in greater accessibility of Trp-92 toward modifications. In contrast, the cognate tRNATrp substrate exerted a specific protective effect against inactivation by both of the reagents, indicating that the TrpRS-tRNATrp interaction reduces the accessibility of Trp-92 under our experimental conditions. By comparison, modification of sulfhydryl groups by means of iodoacetamide did not reduce TrpRS activity. Observations on Trp-specific modification and substrate protection effects are discussed in the context of the Bacillus stearothermophilus TrpRS crystal structure.

Key words: aminoacyl-tRNA synthetase, Bacillus subtilis, chemical modification, conformational change, transfer RNA, tryptophanyl-tRNA synthetase.
Characterization of stable RNAs from the resected intestinal tissues of individuals with either Crohn's disease or ulcerative colitis
Authors: Roy Guylaine , Mercure Stéphane , Beuvon Frédéric , Perreault Jean-Pierre
Published: April 2011

Circular RNAs reminiscent of viroids and the human hepatitis delta virus have been proposed as possible nonconventional pathogens responsible for Crohn's disease and ulcerative colitis, two inflammatory bowel diseases. Consequently, RNA was extracted from various areas of intestinal tissues from individuals with either Crohn's disease or ulcerative colitis as well as several appropriate control diseases, and analyzed by two-dimensional gel electrophoresis. No circular viroid-like RNAs (<1500 nucleotides) were detected, confirming a previous report that was limited to the investigation of small RNAs (<300 nucleotides). However, three small, unusually stable, linear RNAs were shown to be associated to both Crohn's disease and ulcerative colitis tissues: a specific 28S ribosomal RNA cleavage product characterized previously; a 5.8S ribosomal RNA conformer; and a fragment homologous to transcripts from DNA CpG islands. The two last RNAs were detected prior to visible morphological tissue alterations, suggesting that they are produced early during the inflammation and that they have value as molecular diagnostic tools for the inflammatory bowel diseases. The potential cellular mechanisms producing these RNAs and their involvement in inflammatory bowel disease are discussed.

Key words: ribosomal RNA, inflammatory bowel diseases, human intestine, inflammation, viroids.
The brain in evolution and involution
Authors: Parent André
Published: April 2011

This paper provides an overview of the phylogenetic evolution and structural organization of the basal ganglia. These large subcortical structures that form the core of the cerebral hemispheres directly participate in the control of psychomotor behavior. Neuroanatomical methods combined with transmitter localization procedures were used to study the chemical organization of the forebrain in each major group of vertebrates. The various components of the basal ganglia appear well developed in amniote vertebrates, but remain rudimentary in anamniote vertebrates. For example, a typical substantia nigra composed of numerous dopaminergic neurons that project to the striatum already exists in the brain of reptiles. Other studies in mammals show that glutamatergic cortical inputs establish distinct functional territories within the basal ganglia, and that neurons in each of these territories act upon other brain neuronal systems principally via a GABAergic disinhibitory output mechanism. The functional status of the various basal ganglia chemospecific systems was examined in animal models of neurodegenerative diseases, as well as in postmortem material from Parkinson's and Huntington's disease patients. The neurodegenerative processes at play in such conditions specifically target the most phylogenetically ancient components of the brain, including the substantia nigra and the striatum, and the marked involution of these brain structures is accompanied by severe motor and cognitive deficits. Studies of neural mechanisms involved in these akinetic and hyperkinetic disorders have led to a complete reevaluation of the current model of the functional organization of the basal ganglia in both health and disease.

Key words: brain phylogeny, basal ganglia, neurotransmitters, neurodegenerative disorders.
Myc-epitope tagged proteins detected with the 9E10 antibody in immunofluorescence and immunoprecipitation assays but not in Western blot analysis
Authors: Fan Huizhou , Villegas Cristy , Chan Arthur K , Wright Jim A
Published: April 2011

A human Myc epitope is frequently used to tag proteins for expression experiments in nonhuman cells. We used the monoclonal 9E10 antibody specific for this epitope to analyse the expression of four proteins carrying the Myc tag in cells transfected with expression vectors. While all four proteins can be detected by immunofluorescence and immunoprecipitation assays, surprisingly, only two proteins could be detected in Western blot analysis, indicating that epitope recognition by the monoclonal antibody can be blocked in some membrane-retained ectopic proteins. Other techniques such as immunofluorescence and immunoprecipitation assays can be successfully used with the 9E10 antibody to determine potential expression of Myc-tagged proteins.Key words: recombinant protein, Myc epitope, 9E10, Western blot, gene expression, immunofluorescence assay, immunoprecipitation.
Differentiation-dependent regulation of retinal dehydrogenase gene expression in the trachea
Authors: Bhat Pangala V , Bader Thomas , Nettesheim Paul , Jetten Anton M
Published: April 2011

Retinoic acid (RA), a metabolite of vitamin A, is known to be a key signaling molecule in regulating epithelial cell differentiation. We recently characterized and cloned a retinal dehydrogenase (RALDH) that catalyzes the oxidation of retinal to RA. In this study, we investigated the effects of retinoids on the level of RALDH mRNA and protein as well as RALDH activity in the trachea and cultured tracheal epithelial cells. Vitamin A deficiency induced squamous metaplasia in the tracheal epithelium and down-regulated RALDH expression. Supplementation of retinol and retinoic acid to vitamin A deficient rats restored the normal mucociliary epithelium and up-regulated the RALDH expression. In rat epithelial cells cultured in vitro, RAinhibited squamous differentiation and promoted mucociliary differentiation. Squamous differentiated cultures (RA-) expressed very low levels of RALDH mRNA, whereas mucociliary differentiated cultures (RA+) expressed high levels of RALDH mRNA. Retinal and retinol were poor inducers of mucociliary differentiation as well as RALDH expression. The RALDH expression paralleled the expression of the mucin-1 gene in mucociliary cultures. These results suggest that the expression of RALDH is dependent on the differentiation state of the airway epithelium.Key words: retinoic acid, retinal dehydrogenase, gene expression, tracheal epithelium.
Blurring the distinction between slow and intermediate chemical exchange
Authors: Bain Alex D
Published: April 2011

NMR is a vital tool for measuring the dynamics of biological macromolecules in solution. The chemical exchange observed is often divided into slow or intermediate exchange. Slow exchange affects principally the z magnetizations of the system and is observed in modified spin-lattice relaxation experiments. Intermediate exchange gives rise to broadening and coalescence in the spectrum itself. This broadened spectrum is often considered as a whole, but we have shown that it is better to regard it as a sum of transitions, with a generalized picture of the transition probability. In this paper, we give explicit expressions for the lineshape for two sites and review some of the recent applications of chemical exchange in biochemical NMR.Key words: NMR, lineshape, conformation, chemical exchange, relaxation, dynamics.
Regulation of D-glucose-6-phosphate dehydrogenase from Schizosaccharomyces pombe
Authors: Tsai C Stan , Chen Q
Published: April 2011

D-Glucose-6-phosphate dehydrogenase is a regulatory enzyme of the oxidative pentose phosphate pathway in Schizasaccharomyces pombe. The enzyme is subject to negative cooperative regulation by D-glucose-6-phosphate as characterized by the Hill coefficient of 0.68 ± 0.04. D-Glyceraldehyde-3-phosphate and D-ribulose-5-phosphate rectify the negative cooperativity as evidenced from a change in the Hill coefficients to 0.98 ± 0.05 and 1.02 ± 0.05, respectively. These pentose phosphate pathway intermediates also inhibit the enzyme competitively with respect to D-glucose-6-phosphate. Thus, D-glucose-6-phosphate dehydrogenase provides an avenue for regulating the partitioning of D-glucose between the redundant branches of the oxidative phosphate pathway in S. pombe.Key words: regulation, yeast, glucose-6-phosphate dehydrogenase.
Two-dimensional 1H and 15N NMR titration studies of hisactophilin
Authors: Hammond Michael S , Houliston R Scott , Meiering Elizabeth M
Published: April 2011

We have used two-dimensional 1H-15N heteronuclear single quantum correlation spectroscopy to measure the pH dependence of backbone amide group chemical shifts in the actin binding protein hisactophilin over the pH range 5.7-11.1. Most of the resonances can be analyzed using a simple equation involving a single apparent ionization constant, pKapp. The majority of resonances in the protein titrate with pKapp values of 5.6-7.4. The results can be rationalized in terms of titration of many histidine residues in hisactophilin. The titration data provide direct experimental support for the proposed models of the atomic basis of actin and membrane binding by hisactophilin.Key words: hisactophilin, histidine, ionization constants, nuclear magnetic resonance, NMR.
Identification of the in vivo promoters of bacteriophages S13 and ϕX174 and measurement of their relative activities
Authors: Sorensen Sven E , Barrett Jane M , Wong Alex KC , Spencer John H
Published: April 2011

Regions of bacteriophages ϕX174 and S13 that contain putative promoter sequences were amplified by the polymerase chain reaction (PCR) and cloned into the reporter vector pKO-1. Assays of galactokinase activity revealed in vivo promoter activity in those constructs containing the promoter sequences with transcription initiation (+1) sites at nucleotide positions 45, 982, 1823, and 5211. These were identical in location to sequences with in vitro promoter activity and to the three known promoters PA, PB, and PD. P5211 is the location of a new, fourth, promoter. A site with a +1 position at nucleotide 4876, previously shown to initiate RNA synthesis in an in vitro run-off transcription assay, had no in vivo promoter activity. To investigate whether flanking sequences had effects on promoter activity, restriction fragments of ϕX174 and S13 that encompass the in vivo promoters were cloned into the reporter vector pKO-1. The PA and P5211 promoter constructs showed dramatic effects with increases in activity of up to 7 times that shown with the PCR-generated promoter constructs. The ϕX174 PB promoter construct had a 50% decrease in activity compared with the PCR-generated PB clone. While the data showed that in most instances promoter activity is affected by the flanking sequences in which the promoter is embedded, no general pattern correlating flanking sequences and promoter activity could be discerned. Additional evidence that the promoter sequence regions were active in vivo promoters was obtained by S1 nuclease mapping experiments. Initiation of RNA synthesis was shown at positions 45, 982, and 5211.Key words: promoters, phage S13, phage phiX174, in vivo.
Purification and kinetic characterization of 6-phosphogluconate dehydrogenase from Schizosaccharomyces pombe
Authors: Tsai C Stan , Chen Q
Published: April 2011

6-Phosphogluconate dehydrogenase is the pivotal enzyme that links the gluconate route and the oxidative phase of the pentose phosphate pathway in Schizosaccharomyces pombe. The enzyme differs from the known 6-phosphogluconate dehydrogenases of other sources in that the Schizosaccharomyces enzyme is tetrameric having a subunit mass of 38 kDa, that it requires NADP+ obligatorily for activity, and that it can be activated by divalent metal ions such as Co2+ and Mn2+. Steady-state kinetic studies were undertaken. Initial rate and product inhibition results suggest that 6-phosphogluconate dehydrogenase from Schizosaccharomyces pombe catalyzes NADP+-linked oxidative decarboxylation of 6-phosphogluconate by an equilibrium random mechanism with two independent binding sites, namely one site for the nicotinamide coenzyme, NADP+/NADPH, and another site for 6-phosphogluconate-D-ribulose-5-phosphate and for CO2. Studies of pH dependence implicated a basic residue with a pK value of 7.4 in the binding of 6-phosphogluconate and an acidic residue with a pK value of 6.7 in the cation-mediated interaction of NADP+ with the enzyme.Key words: yeast, 6-phosphogluconate dehydrogenase.
Spin-label studies of lipid-protein interactions with reconstituted band 3, the human erythrocyte chloride-bicarbonate exchanger
Authors: Taylor Andrew M , Watts Anthony
Published: April 2011

Lipid-protein interactions in reconstituted band 3 preparations were investigated by using spin-labeled lipids in conjunction with electron paramagnetic resonance (EPR) spectroscopy. Purified erythrocyte band 3 was reconstituted into egg phosphatidylcholine liposomes at high protein density with preservation predominantly of the dimeric state. Lipid-protein associations were revealed by the presence of a component in the EPR spectra that, when compared to spectra obtained from protein-free bilayers, indicated that lipid chain motions are restricted by interactions with the protein. From the fraction of the motionally restricted component obtained from the phosphatidylcholine spin-label, a value of 64 ± 14 annular lipids per band 3 dimer was obtained. This agrees with a value of 62 for the number of lipids that may be accommodated around the electron density map of a band 3 dimer. Selectivity of various spin-labeled lipids for the protein revealed that androstanol had a lower affinity for the band 3 interface, whereas a distinct preference was observed for the negatively charged lipids phosphatidylglycerol and stearic acid over phosphatidylcholine. This preference for negatively charged lipids could not be screened by 1-M salt, indicating that electrostatic lipid-protein interactions are not dominant. Estimates of annular lipid exchange rates from measured acyl chain segmental motions suggested that the rate of exchange between bilayer and boundary lipids was ~106 s-1, at least an order of magnitude slower than the rate of lipid lateral diffusion in protein-free bilayers.Key words: band 3, reconstitution, electron paramagnetic resonance, lipid-protein interactions.
A geosynthetic reinforcement solution to prevent the formation of localized sinkholes
Authors: Villard P , Gourc J P , Giraud H
Published: April 2011

To prevent the appearance of localized sinkholes under roads and railway lines in areas at risk, a research program testing a geosynthetic reinforcement solution was carried out by a group of laboratories. The aim of the reinforcement is to limit surface deformation after the appearance of a sinkhole by making the surface settlement as compatible as possible with the geometrical safety criteria of the road or railway line until earth filling and repair works can be scheduled. Full-scale tests were carried out on reinforced, instrumented road and railway structures subjected to localized collapse. At the same time, a numerical study was carried out to gain a better understanding of the mechanisms involved (arch effect, membrane effect, and collapse mechanisms). The experimental results of the full-scale tests were analyzed and compared with the results of three-dimensional finite element modeling.Key words: localized sinkhole, karstic cavity, reinforcement, geosynthetic.
Modelling glacial till under triaxial conditions using a BRICK soil model
Authors: Lehane Barry M , Simpson Brian
Published: April 2011

The paper presents some findings from recent laboratory research aimed at improving ground-movement predictions in a hard, heavily overconsolidated lodgement till. These findings are subsequently applied to a new three-dimensional version of the BRICK soil model to investigate the suitability of this model for the till. It is shown that BRICK captures the essential features of the material's behaviour under triaxial conditions and is capable, when incorporated in a finite element code, of providing realistic predictions for the settlement of shallow foundations.Key words: glacial till, stiffness, strength, BRICK model, footing settlement.
Proposition d'une loi « hybride » modélisant l'écrouissage du sel gemme
Authors: Hamami M
Published: April 2011

The work presented in this paper is part of a research program dealing with the thermomechanical behaviour of rock salt. It consists of studying the deferred behaviour by means of multi-step creep tests with changes in deviator and temperature. The test results have revealed the strain-hardening character of rock salt superposed to the influence of temperature and stress. The interpretation of the test results with the model designed by J. Lemaitre, is not completely satisfactory for the entire set of test results because Lemaitre's model is used for the modeling of the viscoplastic behaviour of materials with only one strain hardening variable. Hence, a "hybrid" model introducing a double variable for strain hardening has been proposed. The validation of this model on the creep tests is very satisfactory and confirms the existence of two variables of strain hardening for rock salt behaviour.Key words: rock salt, multi-step creep, strain hardening, J. Lemaitre model.
Using time domain reflectometry in triaxial testing
Authors: Grozic J LH , Lefebvre M E , Robertson P K , Morgenstern N R
Published: April 2011

Time domain reflectometry (TDR) can be used to determine the volumetric water content of soils. This note describes the utilization of a TDR miniprobe in triaxial testing. The TDR performance was examined with a series of tests that not only proved its reliability but also resulted in two empirical correlations. Using these correlations, the degree of saturation and volumetric water content during triaxial testing could be determined. The TDR was then put to use in a laboratory program designed to investigate the response of loose gassy sand under static and cyclic loading. Because of the TDR measurements it was possible to determine the degree of saturation and void ratio of the gassy specimens. The TDR miniprobe proved to be accurate, simple to use, and inexpensive to build.Key words: time domain reflectometry, TDR, triaxial testing, gassy, unsaturated.
Numerical analysis of kinematic response of single piles
Authors: Bentley Kevin J , Naggar M Hesham El
Published: April 2011

Recent destructive earthquakes have highlighted the need for increased research into the revamping of design codes and building regulations to prevent further catastrophic losses in terms of human life and economic assets. The present study investigated the response of single piles to kinematic seismic loading using the three-dimensional finite element program ANSYS. The objectives of this study were (i) to develop a finite element model that can accurately model the kinematic soilstructure interaction of piles, accounting for the nonlinear behaviour of the soil, discontinuity conditions at the pilesoil interface, energy dissipation, and wave propagation; and (ii) to use the developed model to evaluate the kinematic interaction effects on the pile response with respect to the input ground motion. The static performance of the model was verified against exact available solutions for benchmark problems including piles in elastic and elastoplastic soils. The geostatic stresses were accounted for and radiating boundaries were provided to replicate actual field conditions. Earthquake excitation with a low predominant frequency was applied as an accelerationtime history at the base bedrock of the finite element mesh. To evaluate the effects of the kinematic loading, the responses of both the free-field soil (with no piles) and the pile head were compared. It was found that the effect of the response of piles in elastic soil was slightly amplified in terms of accelerations and Fourier amplitudes. However, for elastoplastic soil with separation allowed, the pile head response closely resembled the free-field response to the low-frequency seismic excitation and the range of pile and soil parameters considered in this study.Key words: numerical modelling, dynamic, lateral, piles, kinematic, seismic.
Evaluating dual porosity of pelletized diatomaceous earth using bimodal soil-water characteristic curve functions
Authors: Burger Craig A , Shackelford Charles D
Published: April 2011

Soil-water characteristic curve data for specimens containing either ~1 mm or ~2 mm diameter pellets of processed diatomaceous earth are measured using a variety of methods (Tempe cell, pressure plate, filter paper, and chilled-mirror psychrometer). The measured soil-water characteristic curve data are bimodal, reflecting both the microscopic porosity region within the individual pellets, or intrapellet porosity, and the macroscopic porosity region between the pellets, or interpellet porosity. The bimodal distributions are consistent with scanning electron micrographs that show the existence of microscopic pores within each pellet, and the relatively high total porosities (0.725 and 0.764) for the coarse-grained diatomaceous earth specimens. The measured soil-water characteristic curve data are fit with modified forms of the BrooksCorey, van Genuchten, and FredlundXing soil-water characteristic curve functions to account for the bimodal shapes of the measured data. The average microscopic porosities resulting from the curve fits represent 45.0 and 47.9% of the total porosities for the two diatomaceous earth materials. These percentages of microscopic pore space are consistent with the product literature value of approximately 50% for the same materials based on mercury intrusion porosimetry. Thus, the results illustrate the application of bimodal soil-water characteristic curve functions for determining the microscopic and macroscopic portions of the total porosity of dual-porosity media, such as pelletized diatomaceous earth.Key words: bimodal soil-water characteristic curves, diatomaceous earth, dual porosity, macroporosity, microporosity, soil-water characteristic curves (SWCC), soil suction.
Active earth thrust on cantilever walls with short heel
Authors: Greco Venanzio R
Published: April 2011

This technical note presents a method to evaluate the thrusts on cantilever walls with a short heel using Coulomb's approach in terms of limit equilibrium. The proposed method permits solutions to some problems which cannot be solved using the customary method of Rankine, such as those concerning backfill with an irregular shape, subject to strips and lines of charge, or affected by pore pressure.Key words: active earth force, cantilever walls, lateral pressure, active condition.
A constitutive model for isotropic freshwater ice
Authors: Derradji-Aouat A , Evgin E
Published: April 2011

A three-dimensional constitutive model is developed to describe the stressstrain behaviour of isotropic freshwater ice. The model consists of two sets of equations. The first set deals with the behaviour of intact ice (undamaged material), and the second set accounts for the effect of damage (microcracking) on the overall stressstrain behaviour of ice. The intact-ice model (the first set of equations) is developed on the basis of the traditional viscoelasticity and viscoplasticity theories, whereas the damaged-ice model (the second set of equations) is developed using the rate theory for crack kinetics. The results of several uniaxial and triaxial tests are used to evaluate the accuracy of the model predictions. The comparisons between the predicted and measured stressstrain curves indicate that the model predicts reasonably well the strength of ice, the effect of damage, and the postpeak behaviour (including softening) of ice subjected to monotonic loading and unloadingreloading cycles.Key words: isotropic freshwater ice, constitutive model, damaged ice, crack kinetics, cyclic loading, softening.
An empirical-statistical model for debris flow travel distance
Authors: Fannin R J , Wise M P
Published: April 2011

An empirical model is presented for analysis of debris flows based on field observations of landslides from clear-cuts in the Queen Charlotte Islands, British Columbia. Given an initial failure volume, changes in event magnitude arising from entrainment and deposition along the path of movement are used to establish the point at which the cumulative flow volume diminishes to zero, and therefore the total travel distance. Hillslope morphology is used to assign three types of flow behaviour: unconfined, confined, and transition flow. Flow behaviour and slope angle determine the occurrence of entrainment or deposition in the model, for every reach of the event path. Volume change in a reach is calculated from regression analysis of the Queen Charlotte Islands field observations. Predictor variables are reach length, width (of entrainment and (or) deposition), and slope angle, together with a bend-angle function and the incoming flow volume.Key words: slope stability, debris flow, travel distance, runout, risk, clear-cut.
Permeability evaluation and its implications for consolidation analysis of an Italian soft clay deposit
Authors: Cortellazzo Giampaolo , Simonini Paolo
Published: April 2011

The present research concerns a comparative analysis of the possible methods for estimating soft silty clay permeability to be used in the analysis of consolidation. For this purpose the consolidation response of a thick and homogeneous, instrumented soft silty clay deposit, on which an embankment was constructed, is back-analyzed using the finite-element method. To model the consolidation process, permeability data are carefully determined both from laboratory and in situ piezocone tests. One-dimensional and triaxial permeability test data are compared with the results of piezocone dissipation tests, the latter interpreted using four different solutions. The effects of anisotropy on permeability characteristics influencing the consolidation rate are also discussed.Key words: consolidation, embankment, finite-element analyses, permeability, piezocone, soft silty clay.
Comparison of Observed and Calculated Ground Temperatures with Permafrost Distribution under a Northern Lake
Authors: Brown W G , Johnston G H , Brown R. J. E
Published: April 2011

Making use of limited ground temperature measurements in the neighbourhood of a small shallow lake near Inuvik, N.W.T., it was possible with the help of an electronic computer to estimate the entire thermal regime under and about the lake. The results indicated a completely unfrozen zone of roughly hour-glass shape directly under the lake. Field borings under the lake and adjacent to it supported this theoretical finding.
Identification and Performance of Swelling Soil Types
Authors: Hardy R M
Published: April 2011

Many soil types, both overconsolidated and normally consolidated, in the Prairie provinces and northwestern Canada display high swelling characteristics. Experience has shown that conventional theories of soil mechanics are inadequate to predict accurately the performance of such soils in engineering practice. The paper discusses procedures for the identification of highly swelling soils and for numerically evaluating potential swelling pressures. Modifications to current design practices are suggested and the importance of swelling pressure concepts in engineering practice are discussed.
CULVERT ELONGATIONS IN FILLS FOUNDED ON SOFT CLAYS
Authors: Hughes J. M. O.
Published: April 2011

The results of field observations of a culvert elongation under a completed stable fill are presented. The measurement of culvert elongation on this and several other stable fills, of similar dimensions, on the same foundation material, showed very large movements. This elongation appeared to take place as an 'elastic' bulging of the fill during the construction. Continuous measurements of culvert elongation are now being used to control further fills built on similar foundations. It is considered that any failure could be anticipated by an increased rate of culvert elongation.
Factors affecting the frost susceptibility characteristics of pulverized fuel ash
Authors: Sutherland H. B. , Gaskin P. N.
Published: April 2011

The results of laboratory studies of the frost susceptibility characteristics of pulverized fuel ash are presented. Four different ashes were investigated, in their plain state, and also after stabilization with ordinary Portland cement and calcitic hydrated lime. Measurements were made of frost heave, permeability, compressive and tensile strength, and heaving pressure. Frost heave was shown to decrease as the strength increased and as the permeability decreased. Values of strength and permeability were found at which the frost heave was reduced to an acceptable value, and the relative importance of strength and permeability in reducing frost heave is discussed. The heaving pressures mobilized are compared with the corresponding compressive and tensile strengths of the ashes.
The Bearing Capacity of Rigid Piles Under Inclined Loads in Sand. II: Batter Piles
Authors: Meyerhof G. G. , Ranjan Gopal
Published: April 2011

Following the previous investigation reported in the first part on vertical piles, this second part of the paper presents an analysis of the results of loading tests on rigid batter piles under inclined load in sand. The bearing capacity of axially loaded batter piles is discussed by comparing experimental results and theoretical estimates. The theory for ultimate resistance of rigid vertical piles under horizontal loads is extended to that of laterally loaded batter piles. Model test results are compared with those of theoretical estimates and good agreement is found. Methods of analysis of vertical piles under inclined loads are extended to those of rigid batter piles under inclined loads in sand and the analysis is compared with some test results.
Settlement of an Embankment Constructed on Marine Clay
Authors: Devata M. , Darch B. T.
Published: April 2011

Construction of Highway 417, located in the Ottawa Valley region of south-eastern Ontario, commenced in 1969. At one of the structure crossings along this highway, namely the Anderson Road site, a 180–196 ft (55–60 m) thick stratum of sensitive compressible marine clay exists. The approach embankments, at this site, induced a level of stress in excess of the preconsolidation pressure of the clay. It was decided to surcharge the approaches in order to accelerate the time–rate of consolidation of the foundation clay and thus minimize postconstruction maintenance. Settlement observations have been made regularly since the placement of the fills. This paper describes the site, the applied loading, the settlements observed, and the results of laboratory tests. The recorded settlements, at various locations along the south approach, have been compared with settlements computed by methods in which different stress distribution theories and drainage assumptions were used. One method gave settlement results which were in close agreement with those observed.
Geotechnical Properties of a Very Dense Glacial Till
Authors: Radhakrishna H. S. , Klym T. W.
Published: April 2011

This paper presents the results of a comparative study of both field and laboratory measurements of the geotechnical properties of a very dense glacial till. This study was carried out to determine the feasibility of founding the major structures of a thermal generating station complex on very dense till. In situ pressuremeter tests, vertical and lateral plate load tests, and in situ shear box tests were carried out. A comparative laboratory test program on soil specimens from undisturbed block samples consisted of drained and undrained triaxial compression tests including a number of K0 and stress path tests. Foundation design parameters obtained from pressuremeter tests were in good agreement with the plate load test values. Laboratory test values underestimate the strength and deformation modulus of the dense till. The factors which influence the differences in the field and laboratory values of the strength and deformation properties of the till are discussed.
A New Technique for Reduction of Excess Pore Pressures During Pile Driving
Authors: Holtz Robert D. , Boman Per
Published: April 2011

A new technique is described whereby excess pore pressures induced during pile driving in soft, varved silts and clays were economically reduced to a safe level. The technique was applied to piles at a bridge site south of Stockholm, Sweden, where a small slide had occurred during pile driving. A new paper–plastic drain was attached to the wood piles during driving, and two pulling tests indicated that the drain was undamaged under normal driving conditions. The excess pore pressure generated during the driving of some 13 test piles without drains and 48 piles with drains was measured. The data indicated at least a 50% relative reduction in excess pore pressure when the drain was used. In addition, the cost of the technique was considerably less than alternative methods for dealing with dangerous excess pore water pressures resulting from piling in similar soils. The technique has been successfully applied at two other piling sites in Sweden.
Excavation unloading effect in rock wedge stability analysis
Authors: Kalkani E. C.
Published: April 2011

The stability of a rock wedge resting on two intersecting discontinuities is examined under excavation unloading forces. The variation of the factor of safety as well as the external force required to restore a certain factor of safety is examined for a range of values of ambient stress coefficient and for a variation in the distance of a crack from the cut face of the wedge.
Soil block sampler
Authors: Domaschuk L.
Published: April 2011

This note describes a sampler used to obtain block samples from the bottom of a borehole. Soil disturbance by the sampler was investigated using a pocket penetrometer and a lab vane apparatus. Minor disturbance occurred near the edge of the sampler; the amount was comparable to that associated with Shelby tube sampling.
Bearing capacity of piles in layered soils. Part 1. Clay overlying sand
Authors: Meyerhof G. G. , Sastry V. V. R. N.
Published: April 2011

The paper summarizes investigations on jacked and driven piles in non-uniform soils consisting of clay and sand. Part 1 deals with the bearing capacity of piles penetrating through clay into sand whereas Part 2 discusses the case of piles in a sand stratum overlying clay. Preliminary tests on small model piles have been undertaken to study the effects on the point resistance of parameters such as the strength and thickness of a clay stratum, the strength ratio of soils in the two layers and the geometry of the layers. Based on these results, tests on a 76 mm diameter instrumented steel pile and a 36 mm diameter static cone penetrometer have been carried out for selected combinations of the variables involved.The test results are analysed to determine the influence of clay thickness and strength on the point resistance of piles in sand, expressed by a non-dimensional clay strength factor λ, and parameters influencing λ are discussed. The effect of layering on the shaft friction in sand and the radial stresses along the pile length are studied. The efficiency of small groups of model piles in layered soils is obtained. Field data are analysed, including scale effects, and simple design rules are suggested to estimate the bearing capacity of piles in layered soils.
Manasan Falls control structure design and construction aspects
Authors: Janzen P. , Kuluk A. G.
Published: April 2011

This paper describes the design, construction, and performance of the Manasan Falls control structure. It is located at Manasan Falls on the Burntwood River approximately 6 km (4 mi) upstream of Thompson in northern Manitoba. At this location the river is 210 m (700 ft) in width. The control structure consists of two rock- and earthfill groins creating a trapezoidal opening in the proximity of a bedrock outcrop at the falls. Its purpose is to increase the upstream water levels sufficiently to promote formation of a stable ice cover in the winter.Construction was carried out in the fall and winter of 1976, in the wet, on an overburden foundation with river flows averaging 170 m3/s (6000 cfs). Upstream of the bedrock lip of the falls, the channel floor consists of highly erodible varved silty clay. This area was protected with rockfill pavements. Two groins of about 9 m (30 ft) maximum height were constructed using random rockfill with upstream granular filter zones and seals. The ends of the groins were protected by 0.9–1.2 m (3–4 ft) nominal diameter armour rockfill.Performance to date has revealed that the groins and gap opening have provided the required stage–discharge relationships and have promoted a stable upstream ice cover in the winter. The fill materials have remained stable under flows of up to 850 m3/s (30 000 cfs) and average gap velocities exceeding 6 m/s (20 fps).
Rupture of an ice mound near Cape Dorset, N.W.T.
Authors: Frederking R. M. W.
Published: April 2011

An ice feature comprising ice blocks ranging from football size to 0.6 m cubes to 1.2 m × 3.6 m × 0.6 m slabs was observed on the surface of a frozen lake. Site investigations revealed the source of the blocks to be an ice mound that had formed along the shore of the lake. A model, supported by local meteorological, geological, and hydrological information, is proposed to explain the formation of the ice mound and its subsequent rupture.
Deformation behaviour and strength of frozen sand
Authors: Parameswaran V. R.
Published: April 2011

Uniaxial unconfined compression tests were carried out on frozen saturated Ottawa sand containing about 20% by weight of water, at temperatures between −2 and − 15°C, and at strain rates varying between 10−7 and 10−2 s−1. The compressive strength and the initial tangent modulus increased with increasing strain rate and with decreasing temperature. At −2°C, values of strength and modulus were considerably lower than those predicted by linear extrapolation of the values observed at lower temperatures, on a log–log scale. This could be due to the presence of unfrozen water in the samples at −2°C.
Plane strain – contact stress distribution beneath a rigid footing resting on a soft cohesive soil
Authors: Patrick A , Selvadurai S , Kempthorne R. Harland
Published: April 2011

This note presents an experimental study of the plane strain – contact stress distribution beneath a rigid footing resting on a compacted soft cohesive soil medium. The immediate contact stress distribution was found to be highly dependent on the magnitude of the applied stress relative to the ultimate bearing capacity of the foundation. At low levels of applied stress the contact stresses were substantially higher at regions adjacent to the footing edges. As the applied stresses were increased, the contact stresses achieved a more uniform configuration.
Regional aquifer parameters evaluated during mine depressurization in the Athabasca Oil Sands, Alberta
Authors: Hackbarth Douglas A.
Published: April 2011

Withdrawal of groundwater for depressurization of the "water sands aquifer" under a test pit in the Athabasca Oil Sands of Alberta caused declines in hydraulic heads in two observation wells located 3700 and 6600 m away. Analysis of these declines over a 6 month period by the time–drawdown method indicated transmissivity values of 68 m2/day for both wells. Pumping tests of 24 h duration had previously indicated that transmissivities at the two observation wells were 1.2 and 118 m2/day.Geological assessment of the water sands aquifer revealed that it is discontinuous between the test pit and the observation wells. Variations in lithology and heavy oil saturation as well as relief on the underlying limestone indicate that the water sands aquifer does not meet the "homogeneous and isotropic" criteria necessary for application of the Theis method of analysis. Nevertheless, the excellent fit of the time–drawdown data to the type curve and the identical values obtained for transmissivity indicate that the method can be used for pumping tests of long duration, which reflect conditions over extensive areas of the water sands aquifer.
Parametric study on the plasticity parameters in elastic–plastic analysis of underground openings
Authors: Chugh Ashok K.
Published: April 2011

Results of several analyses of two-dimensional problems, carried out to study the effects of small variations in the plasticity parameters on the solution, are presented. Also included are the results of analyses using several different material idealizations usually employed in the structural analysis of openings in geologic formations. The geometric and loading configurations considered are those commonly encountered in underground openings.
Screw plate testing of a soft clay
Authors: Patrick A , Selvadurai S , Bauer Gunther E. , Nicholas Terrance J.
Published: April 2011

The screw plate test was developed for the determination of the in situ deformability characteristics of both granular and cohesive soils. This paper examines several theoretical models that may be used to evaluate the in situ undrained deformability and shearing strength characteristics of a cohesive soil medium from results of screw plate tests. It is shown that the undrained modulus and the undrained shearing strength can be evaluated directly from the load–displacement response obtained from the screw plate test.
Influence of cyclic load input on the mechanical properties of a sensitive soil from Orleans, Ontario
Authors: Yong R. N. , Taplin D. , Wiseman G.
Published: April 2011

The importance of disturbance and remoulding to the alteration of mechanical properties of sensitive soils has been well documented in the geotechnical literature both in terms of laboratory and field behaviours. Man-made transient dynamic input such as dynamite blasting, heavy vehicles, and train movement have been suspected of being capable of causing a reduction in the in situ strength parameters of sensitive clays. A laboratory test program was undertaken to determine whether dynamic loading at peak stress levels below normal failure strength caused similar changes in the mechanical properties, and specifically to quantify the phenomena.In order to simulate highly overconsolidated conditions most of the tests were carried out under conditions of no confining pressure, although supplemental data were obtained from consolidated undrained tests. Some of the variables examined in this program were confining pressure, mean deviatoric stress, cyclic deviatoric stress, cyclic strain, number of applications, frequency, and reference strength. In order to compare the effect of dynamic input with the long-term creep phenomena, a simultaneous constant load program was undertaken.In general terms, the study indicates that under the prestated laboratory test conditions no major reduction in peak strength was found under dynamic loading, and that failure would occur at comparative stress levels under dead-load conditions, but required a greater time. In addition, examination of the sample after failure revealed that any remoulding of the sample appeared to be restricted to the area adjacent to the shear zone.
Stress path effects on the strength behaviour of a layered soil
Authors: Murthy M. Krishna , Nagaraj T. S. , Sridharan A.
Published: April 2011

An experimental investigation dealing with the influence of stress path on the shear behaviour of a layered soil prepared in the laboratory is described. Specimens trimmed in vertical and horizontal directions have been sheared under three different stress paths in compression and extension tests. Either in compression or extension, the stress–strain behaviour of the specimens with both orientations was apparently the same, although the volume change behaviour was different. The effective stress parameters C′ and [Formula: see text]′ were found to be unique and independent of the stress path and two principal orientations. However, the values of [Formula: see text]′ in extension tests were 6–7° higher than those in compression tests.
Thermal design for insulated pipes
Authors: Hwang C. T. , Seshadri R. , Krishnayya A. V. G.
Published: April 2011

A method for the preliminary design of an insulated pipeline based upon the quasi-static approximation method has been presented. The efficiency of an insulation arrangement is expressed in terms of an insulation factor. Design curves indicating the variation of thaw (freeze) depth with time have been presented for preliminary design purposes.
A one-dimensional analytical model for snow creep pressure on rigid structures
Authors: McClung David M.
Published: April 2011

An analytical model for quasi-static creep forces parallel to the slope at the center of a long rigid structure on a snow-covered slope is derived and checked by the finite element method. The formulation accounts for interruption of snow creep (internal deformation) and glide (slip of the entire snowpack over the ground). The average pressure and length of the zone of influence of the structure upslope are predicted fairly accurately for the range of parameters of interest in comparison with finite element results assuming linear creep and glide constitutive laws. The model is also compared with the equations provided by Haefeli as used in the Swiss Guidelines for Avalanche Defense.
The influence of snow cover on the ground thermal regime
Authors: Goodrich L. E.
Published: April 2011

This paper presents the results of a numerical study of the effects of snow cover on long-term, periodic, steady-state equilibrium ground temperatures. It is shown that mean annual ground temperatures decrease with depth when the soil thermal conductivity is greater in the frozen than in the unfrozen phase. For permafrost conditions the increase in mean annual ground temperatures due to seasonal snow cover is augmented significantly when soil latent heat is present. In seasonal frost cases the calculated depth of frost penetration is extremely sensitive to details of the snow cover buildup. In permafrost cases calculated mean annual temperatures are extremely sensitive to the assumptions made in treating the snow cover. In either case, because it is difficult to model snow cover accurately, the reliability of ground thermal regime computations is adversely affected. Keywords: ground thermal regime, ground temperatures, soil temperatures, numerical model, finite difference, snow cover.