bluuebunny/crossref_metadata_2025 huggingface dataset:
Blood Oxygen Capacity Differences in Yellow Perch (Perca flavescens) from Northern Wisconsin Lakes Differing in pH
Authors: Nelson Jay A. , Magnuson John J. , Chulakasem Weerewan
Published: August 2008

Whether chronic exposure to environmental acidity reduces oxygen loading in fish is still uncertain. We evaluated this question by looking for evidence of adaptations to hypoxia in a population of yellow perch (Perca flavescens) isolated in a well-oxygenated, naturally acidic lake. Perch were sampled directly from this naturally acidic lake (pH 4.5) and two circumneutral lakes, one of which experiences low oxygen. Fish were bled rapidly via cardiac puncture. Hemoglobin, hematocrit, and erythrocyte number were determined by standard methods. Hemoglobin concentrations were highest in perch from the acid lake (6.4 g/dL) intermediate in the neutral lake with anoxic zones (5.7 g/dL) and lowest in the well-oxygenated neutral lake (4.8 g/dL). Increased hemoglobin per red cell accounted for this trend. Slightly larger hematocrits in acid lake perch (41.2 versus 36.2) were achieved through small increases in red cell number and volume. Evidence suggests that these results are part of an adaptational response different from the hematological responses of fish to acute acid exposure.
Biological Bases for Mixed-Species Fisheries: Species Co-distribution in Relation to Environmental and Biotic Variables
Authors: Murawski S. A. , Finn J. T.
Published: August 2008

Factors influencing the degree of temporal and spatial co-occurrence of seven important demersal fish species on Georges Bank (Northwest Atlantic) were analyzed. Species/age co-occurrence data from a 24-yr time series of research vessel bottom trawl surveys were evaluated in relation to temperature and depth preferences, spatial distribution, and species/age abundance trends. Co-occurrence of various species/age groups varied greatly by season and was significantly correlated with overlap in temperature/depth preference indices and annual species abundance. Although species abundance and proportion of survey tows having particular species varied widely over the time series, trends in spatial dispersion indices of particular species were not generally related to abundance. Multiple regression models incorporating temperature and depth preference overlap and species abundance as independent variables accounted for a high proportion of total variance in the transformed proportion of survey tows containing co-occurring species (mean R2 = 0.69 for age 1 + fishes, mean R2 = 0.44 for age 0). Results indicate that although the frequency of technological (bycatch) interaction among pairs of species may be highly variable depending on season, area, and year, co-occurrence among species is nonetheless relatively predictable. Minimization of the potential adverse impacts of mixed-species harvesting (i.e. failure to achieve management goals for all species simultaneously) may be accomplished by exploiting stocks individually during periods of maximum spatial separation and by using information on the determinants of species co-distribution to more accurately forecast bycatch levels.
Behaviour and Vocalizations of Two Single Sperm Whales, Physeter macrocephalus, Off Nova Scotia
Authors: Mullins Julia , Whitehead Hal , Weilgart Linda S.
Published: August 2008

During June 1986, two male sperm whales, Physeter macrocephalus, on the Scotian Shelf were tracked by listening for their clicks with a directional hydrophone for periods of 12.5 and 7 h, respectively. Each whale travelled along the edge of the shelf at about 2 kn (3.6 km/h), and one whale, on two occasions at least, dived to the ocean floor. After about 30 min underwater, the whales spent approximately 9 min at the surface breathing. When the whales were visible at the surface, they were silent, except on one occasion when "slow clicking" (mean interclick interval of 4.6 s) was heard from Whale 2. While underwater, most of the sound production consisted of "usual clicks" (mean interclick interval 0.96 and 0.69 s for the two whales) interrupted by frequent short silences (mean durations 21.06 and 27.82 s) and occasional "creaks" (with interclick intervals less than 0.2 s) and "slow clicks." No "codas" (stereotyped patterns of clicks) were heard from these two single whales. These results are consistent with the hypotheses that "usual clicks" and "creaks" are used for echolocation and "codas" for communication.
Accumulation of Mercury by Plankton and Benthic Invertebrates in Riverine Lakes of Northern Manitoba (Canada): Importance of Regionally and Seasonally Varying Environmental Factors
Authors: Jackson Togwell A.
Published: August 2008

Mercury (Hg) concentrations in plankton and benthic invertebrates from riverine lakes of northern Manitoba were generally found to be unrelated, or inversely related, to inorganic and methyl mercury levels and Hg methylation rates in their habitats but were strongly dependent on environmental factors. The relationships suggest that the uptake of Hg by these organisms was controlled largely by suspended and sedimentary Hg-binding substances such as FeOOH, MnOOH, organic matter, sulfides, and clay. The sole exception was midsummer phytoplankton, whose Hg content was a function of Hg levels in local sediments, probably because interference by suspended detritus was minimal; during the spring flood, such interference had a predominant effect. Aeration of lake water by fluvial currents probably enhances the availability of Hg to plankton by promoting decomposition of organic matter and sulfides but decreases the availability of Hg to some benthic animals by causing MnOOH precipitation. FeOOH apparently limits Hg uptake by chironomid larvae but MnOOH limits Hg uptake by oligochaetes, nematodes, and pelecypods, suggesting preferential uptake of certain forms of Hg by particular biological and mineral species. Decreases in temperature may also retard Hg uptake by benthos. Biodilution has no significant effect on Hg accumulation by benthos or plankton.
Freshwater Zooplankton Community Structure: Introduction of Large Invertebrate Predators and Large Herbivores to a Small Species Community
Authors: Vanni Michael J.
Published: August 2008

Two hypotheses have been proposed to explain the scarcity of small zooplankton species in fishless lakes, in which large zooplankton species dominate: (1) selective predation on small species by large invertebrate predators and (2) competitive suppression of small species by large herbivores. These hypotheses were tested at the Experimental Lakes Area (ELA) by introducing a large invertebrate predator, Chaoborus americanus, and a large herbivore, Daphnia catawba, both common in fishless ELA lakes, into a zooplankton community typical of ELA lakes with fish (small zooplankton species present). Chaoborus had much more of an impact than D. catawba on resident zooplankton, although both introduced species significantly reduced the abundance of some resident species. Daphnia galeata mendotae, the dominant species in the absence of introduced species, was reduced to virtual extinction by Chaoborus. The cladocerans Bosmina and Diaphanosoma, the copepods Diaptomus spp., and the rotifer Conochilus also were reduced in abundance by Chaoborus. Daphnia galeata mendotae and Bosmina were the only resident species consistently reduced in abundance by D. catawba. These results support current conceptual models that depict invertebrate predation as an important factor responsible for the relative scarcity of small zooplankton species in fishless lakes.
Potential Determinants of Stable Catch in the Brook Trout (Salvelinus fontinalis) Sport Fishery in Quebec
Authors: Godbout Lyse , Peters Robert H.
Published: August 2008

Evaluation of four existing empirical models of fish yield showed their applicability to be limited for the brook trout (Salvelinus fontinalis) sport fishery in the Laurentian shield because these models explained < 60% of the variation in catch. In at least 80% of the lakes, observed catch exceeded that predicted by two of the models. The other models overestimate catch by 100% or more in at least 25% of the lakes. As a first step to improve these models, we identify correlates of "stable catch," defined by the absence of a significant temporal trend in fishing success in lakes for which at least five consecutive years of data were available. Data available or calculable from government sources and maps were used to construct models that identified fish size, lake trophy, altitude, and pH as promising correlates. A second series of models based on our own field determinations confirmed these findings. After fishing effort had been taken into account, these variables reduced the unexplained variation by up to 50%. Although our estimates of trophy and acidity were crude, this study suggests that these indicators should be included in future models to describe and predict the yield of sport fisheries.
Inferring the Distribution of the Parameters of the von Bertalanffy Growth Model from Length Moments
Authors: Burr Robert L.
Published: August 2008

A theoretical approach is described for determining the joint distribution of the parameters of the von Bertalanffy growth model from statistical moments of length. The approach extends the work of K. J. Sainsbury, who had demonstrated that different mean parameter estimates are obtained by assuming that the von Bertalanffy equation applies to individual fish rather than to groups of fish. Sainsbury articulated the goal of studying the joint probability distributions of K and L∞ in animal populations and developed a maximum likelihood procedure for estimating the parameters of particular distributional forms describing K and L∞, which were assumed for mathematical convenience to be statistically independent. The primary goal of the present paper is to provide a framework for future research in generalizing Sainsbury's approach by considering (K, L∞) to be a random vector described by a joint probability density function and by allowing broader classes of distributions to be considered. Minimum cross-entropy (MCE) inversion, an information–theoretic methodology for approximating probability distributions, is shown to be effective in selecting a reasonable and unique joint distribution corresponding to observable length moments. Appealing features of the MCE methodology include the ability to include prior knowledge of uncertain applicability and the capacity of the resulting approximate distribution to represent potential stochastic dependencies between the von Bertalanffy parameters. Several numerical examples, using simulated and historical data, are presented to illustrate how information about the variation and covariation of L∞ and K can be inferred from a minimal set of length moments. The directions developed in this paper are far from a practical and useful methodology. The MCE inversion procedure is a "method of moments," with no statistical assessment of reliability. Further research is needed to make this promising pdf approximation scheme better suited for real fisheries problems.
Substrate Preferences of Brown Trout Fry (Salmo trutta) m Artificial Stream Channels
Authors: Heggenes Jan
Published: August 2008

Brown trout fry (Salmo trutta) of two sizes (43 and 32 mm mean total length) preferred the coarsest gravel when allowed to choose between three sizes (8–16, 20–30, and 50–70 mm) at two temperatures (12.9–18.1 and 6.0–6.9 °C) in artificial stream channels. Fry hid more in the substrate in daytime than at night and in daytime also hid more at low temperatures than at high temperatures. Increasing the average water velocity from 4 to 14 cm∙s−1 displaced the 43-mm fry slightly downstream at night. The 32-mm fry showed a weaker preference for the coarse substrate and, in general, had less pronounced diurnal substrate preferences.
Validity of an Ecotoxicological Test System: Short-Term and Long-Term Effects of Arsenate on Marine Periphyton Communities in Laboratory Systems
Authors: Blanck Hans , Wängberg Sten-Åke
Published: August 2008

Periphyton communities were established on glass substratum in the Gullmar Fjord (Sweden) and their sensitivity to arsenate was determined with short-term photosynthesis experiments. The study was done in May 1984 when phosphate levels were low. A 1-h exposure to arsenate gave IC20 (concentration required to inhibit photosynthesis by 20%) values of 0.4 μM. Communities established indoors in a flow-through aquaria system were substantially different from the fjord communities in terms of structure and biomass, although photosynthesis showed a similar sensitivity (IC20 = 0.6 μM). To explore the validity of this short-term ecotoxicological test system, we used a set of indoor, flow-through aquaria to study long-term effects (3 wk) on communities established under arsenate stress. Arsenate was added continuously at 0.1–10 μM above background levels (7 nM). Species composition as well as carbon, nitrogen, and chlorophyll a content of the communities were affected at 0.2–0.8 μM (IC20). This is in good agreement with the sensitivity of the short-term test. We conclude that inhibition of the physiological parameter photosynthesis is relevant information for the understanding of ecological events caused by arsenate stress in the periphyton communities. At least for effects of arsenate, the short-term metabolic test system can be used for valid predictions of gross changes in periphyton community structure and production. Comparison with arsenic levels in polluted coastal areas of Sweden lead to the conclusion that periphyton communities may be affected, particularly when phosphorus levels are low.
Induced Community Tolerance in Marine Periphyton established under Arsenate Stress
Authors: Blanck Hans , Wängberg Sten-Åke
Published: August 2008

Pollution-induced community tolerance (PICT) may be used to assess impact of pollutants in the environment and to identify the agents causing the impact. We have examined this possibility using marine periphyton communities. These were established under arsenate stress in indoor aquaria and their community tolerance to arsenate estimated with a short-term photosynthesis test. Arsenate concentrations above 0.1–0.3 μM induced an increased tolerance to arsenate; at severe arsenate stress the increase in tolerance was more than 17 000-fold. Our interpretation is that arsenate exerted a selection pressure on the community, leading to the replacement of sensitive species by tolerant ones which caused the overall arsenate tolerance of the community to increase. Arsenate concentrations that induced the tolerance also affected species composition and biomass accrual, suggesting that community tolerance can be used to properly indicate a disturbed community. Hence the basic requirements are met for the use of PICT as an ecotoxicological tool.
Ontogenetic Changes in the Distribution of Larval and Juvenile Yellow Perch (Perca flavescens): A Response to Prey or Predators?
Authors: Post John R. , McQueen Donald J.
Published: August 2008

Distribution of larval and juvenile yellow perch (Perca flavescens) in Lake St. George, Ontario, changed during development as follows: (1) early in development, the larvae were distributed exclusively offshore, both day and night; (2) larger larvae and juveniles migrated nearshore to offshore at dusk, returning the the nearshore zone at dawn; (3) the extent of this migration weakened as the fish grew, and they spent a greater porportion of their time nearshore and did not migrate as far at night; and (4) by the time juveniles reached approximately 30 mm total length, they were distributed exclusively in the nearshore habitat both day and night. Analysis of published reports on distribution patterns of larval and juvenile yellow perch and the European perch (Perca fluviatilis) suggests that the ontogenetic distribution patterns observed in Lake St. George are typical for the two Perca species. This regularity amongst lakes in ontogenetic distribution pattern occurred despite variation in the selective forces of prey and predator abundance in nearshore and offshore habitats. We conclude that the changes in distribution throughout early development are not in response to the proximate selective forces of prey abundance or predation risk
TWO USEFUL SEX-LINKED MUTANTS IN THE FLOUR BEETLE, TRIBOLIUM CONFUSUM
Authors: Dawson Peter S.
Published: August 2008

Two sex-linked mutations in the flour beetle, Tribolium confusum, are described. Depressed (dep), an elytral mutant, and a new allele of red (ru) are located about 3 map units apart. The ru allele is recessive to r. The acquisition of these mutants, particularly ru, should make the establishment of linkage relationships among sex-linked genes in this species considerably easier than it has been in the past.
ON THE ORIGIN OF THE GENETIC CODE
Authors: Walker G. W. R.
Published: August 2008

A detailed re-examination of the codon and the anticodon catalogues has led to the conclusion that the initiation of codons and anticodons was a coincident process with a significant doublet phase, and that a double-stranded polynucleotide was an essential feature. A model of code initiation is presented that accounts for much of the symmetry in the codon catalogue.
Rail–structure interactions for short span railway and transit bridges
Authors: Magued Mohammed H.
Published: August 2008

The longitudinal movement of a structure supporting continuously welded track relative to that track results in interactive forces (interactions) being induced in both the rails and the structure. The differential movement may arise from thermal effects, volume changes in the structure, substructure deformations, or other factors. These resulting interactions are the focus of this paper.A design tool allowing the estimation of the limiting values of these interactions is presented for use by track and structure designers.The presentation begins with a discussion of the thermal stresses and movements induced in at-grade tangent continuous welded rails (CWR). The interaction of CWR and the structure is then presented, followed by a brief overview of the behaviour of CWR with rail expansion joints. The work addresses tangent tracks and will adequately apply to curved tracks with large radii, say, in excess of 500 m. Adjustments for track curvature would be required for tighter radii. Key words: trackwork, continuous welded rail, bridges, thermal stresses, force interactions.
A reliability assessment of tubular joint specifications
Authors: Packer Jeffrey A. , Kremer John S. M.
Published: August 2008

The limit states design of structural components involves the use of resistance factors which account for the variabilities and uncertainties which exist in both load effect and element resistance. In this paper, the rational development of such resistance factors is examined for axially loaded K, T, and Y joints between steel circular hollow section members subject to predominantly static loading. The development of these factors is primarily oriented to the design of such joints in offshore structures under extreme environmental loading conditions, but onshore applications to buildings are also considered. A level II method of reliability analysis has been used for the derivation of the resistance factors. The joint strength criteria from seven prominent code and noncode design documents have been considered, and recommendations for resistance factors to be used in the design of offshore and onshore tubular joints are made. Key words: steel, offshore structures, tubes, joints, reliability analysis, structural safety.
The investigation and proposed rehabilitation of the Tsing Yi South Bridge, Hong Kong
Authors: Beard A. S. , Tung H. S. S.
Published: August 2008

The Tsing Yi South Bridge was constructed in the early 1970s to provide access between Tsing Yi Island and the mainland at Kwai Chung. It has a prestressed concrete box girder superstructure consisting of five independent units which are monolithic with their piers and have expansion joints at the mid-span shear hinges and the abutments. During routine maintenance it was found that the superstructure cantilevers were deflecting excessively, and consequently a thorough inspection and appraisal were commissioned. These included a complete visual inspection, concrete core extraction, radiographic inspection of prestressing tendons and a programme of load testing. The bridge was also reanalyzed to check its long-term performance. Subsequently, a rehabilitation scheme was designed to recover part of the deflection. This involved the introduction of additional prestress near the box girder's top flange. Key words: prestressed concrete, structural assessment, creep, shrinkage, radiographic inspection, rehabilitation, external prestressing.
Modèle de simulation de la gestion hydrologique
Authors: Llamas J. , Fernandez R. , Galvache A.
Published: August 2008

In this article, a general methodology for simulation of water resources management is suggested. The research has been conducted in three different levels: a deep analysis of the historical management procedures, the development of some alternative ways to optimal management, and the establishment of planning criteria at short, middle, and long term. The main constraints, divided into three categories according to the severity of probable losses, have been defined as a function of several expected goals: hydro power, flood control, recreational activities, etc. The model was applied with excellent results to the upper region of the St. François river basin (Québec, Canada). Key words: simulation, resources management, mathematical models, optimization.
Conception et performance d'un champ d'épandage de grandes dimensions
Authors: Chapuis Robert P.
Published: August 2008

A large disposal field (31 × 69 m) was designed in agreement with legal recommendations. A full scale test with clear water revealed that the field exfiltration rate was much lower than anticipated. This paper describes the design, the instrumentation performed with eleven piezometers, the ground-water conditions as modified by the disposal field, how the true exfiltration rates have been determined after due consideration of natural precipitations and evaporation losses, and also the method used to improve the performance. The value of the infiltration rate into the soil, initially established by percolation tests, was confirmed by permeability tests performed in the piezometers. However, the true exfiltration rate of this disposal field was only 8% of the rate predicted by the conventional, legal design. It is established that this exfiltration rate cannot be derived by simple transposition of the results of percolation tests as presently done by by-laws. Alternatively, more rigorous methods are described. For a good design, it is necessary to perform hydrogeologic studies much more detailed than those presently required by by-laws. Finally, for improving the design and service life of such disposal fields, several suggestions are made to avoid water mounds and to reduce the risk of clogging.
Frost penetration studies in glacial till on the James Bay hydroelectric complex
Authors: Paré J. J. , Lavallée J. G. , Rosenberg P.
Published: August 2008

This paper reports on observations of frost penetration into glacial till in a region of high freezing indices. The frost penetration measurements were carried out in borrow areas and in exposed dyke crests. The locations are far enough apart to be representative of regional frost penetrations. The frost susceptibility of the till is evaluated, and the effect of frost penetration on the design of freeboard and crest detail requirements for the dams and dykes is discussed. The geotechnical properties of the till are given along with the results of a series of surcharged cyclic freeze–thaw and thermal conductivity tests.The use of standard frost susceptibility criteria indicates that the till is classified as being highly frost susceptible; however, if surcharge pressure is considered and recognized as being a factor in reducing frost heave, then the till under field conditions may behave like a material of low frost susceptibility.
Emploi d'une méthode psychrométrique dans des essais triaxiaux sur un limon remanié non saturé
Authors: Verbrugge Jean-Claude
Published: August 2008

This paper summarizes the results obtained with triaxial tests made on an unsaturated loam. The originality of the tests proceeds from the use of a Peltier effect psychometric probe for the measurements of interstitial pressure. This had made it possible to study the variations of the breaking stress in terms of water content and suction of soil. The coefficient χ of Bishop at rupture was also studied in terms of those variables and of the degree of saturation. An experimental relation between χ and |s| is proposed.
The Edgerton Landslide
Authors: Thomson S. , Tweedie R. W.
Published: August 2008

In September 1974 a large landslide occurred about 48 km northeast of Wainwright, Alberta. This failure presented features of interest but preslide conditions could not be reliably determined. Immediately south of this landslide a scarp some 150 m long and 0.6 m high had formed, probably contemporaneously with the failure. Field inspection suggested that this incipient failure was a sufficiently independent feature to merit detailed investigation. The major failure was termed the North Slide and the incipient failure was termed the South Slide. Collectively these slides make up the Edgerton Landslide.The failure occurred largely in flat lying, poorly indurated interbedded sandstones, siltstones, and clay shales of late Upper Cretaceous age which are overlain in the upland areas by a thin veneer of till of Wisconsin age. In the vicinity of the landslides there are many old slump areas much subdued by erosion. Field evidence indicated that the lower part of the recent failure surface had reactivated an old failure surface, whereas the scarp area represents a first time slide.The South Slide was investigated by boreholes and test pits. Samples were obtained for laboratory testing and piezometers and tiltmeters were installed in selected boreholes.The scarp increased in height and by May 1976 it was 2.3 m high. There was no sign of a toe cropping out down the slope; however, the tiltmeters became closed off successively in a downhill direction. There is strong evidence to suggest that failure is progressing from scarp to toe.Analyses of the failure indicate residual angles of shearing resistance were being mobilized along the outer pre-sheared part of the failure surface due to old landslides. The recent slip surface comprises an inward extension of this old surface and an upward portion rising at an angle of about 55° to meet with the known scarp. Along this latter portion of the recent failure surface the soil parameters yielding the most reasonable factor of safety are a peak angle of shearing resistance and a cohesion very much less than that determined from laboratory testing.It is postulated that the failure occurred due to a gradual loss of soil strength, manifested by a virtual disappearance of cohesion, with the final triggering mechanism being a springtime rise in the pore pressure within the slide mass. Factors involved in the strength loss are suggested as including deep weathering during the Tertiary, valley rebound, and old landslide activity.
Détermination des moments et des pressions exercées sur un écran à partir de mesures inclinométriques
Authors: Boissier D. , Gielly J. , Kastner R. , Mangin J. C.
Published: August 2008

This paper presents a method, based on inclinometric and moment measurements, to determine automatically the bending moments and the differential pressures in cast-in-place or sheet pile walls. A mathematical model using the polynomial least-squares approximation is proposed with a computer program developed for that purpose.The results and conclusions are illustrated by two examples. It is clearly shown that we can get the distribution curve of moments even for very inaccurate data. In most cases, the curves of dfferential pressures are significant. However, in the case of uncertain data, measures of bending moments are essential even in limited number. [Journal translation]
A model for coupled heat and moisture transfer during soil freezing
Authors: Taylor George S. , Luthin James N.
Published: August 2008

The objective of this report is to present simulation analyses of heat and water flow during soil freezing. The analyses utilize a modified form of a model presented by Harlan. The model is tested by using experimental data reported by Dirksen and Miller and Jame and Norum. The basic elements of the model are the heat and water flow equations. An implicit finite-difference scheme is used to solve these two equations for the boundary conditions used in the experiments. The agreement between simulated and experimental results is illustrated for temperature, water, and ice contents.
Soil studies at Shipshaw, Quebec: 1941 and 1969
Authors: Legget Robert F. , LaSalle Pierre
Published: August 2008

The Saint Jean Vianney landslide has redirected attention to soil studies conducted in 1941, as part of the site investigation program for the adjacent wartime Shipshaw power project. These included early studies of Leda clay, the sensitivity of which was recognized but not fully appreciated nor understood. Buried organic matter was encountered at one dam site. The possibility of landslide action accounting for the unusual position of this material was discounted in 1941. Recent studies by LaSalle have demonstrated the existence of a massive ancient landslide adjacent to the Shipshaw site. Earth movement resulting from this old landslide could explain the organic stratum. Carbon-14 dating suggests a date for this massive landslide that agrees with historical records of the great Quebec earthquake of August 1663. This caused earth movements of a magnitude not seen in Canada since that time, confirming the possibility of these being the explanation of the unusual position of the organic deposits. References to two papers on the Shipshaw studies, published in 1945, are given. Important corrections to conclusions contained in these papers are suggested.
Ultimate bearing capacity of foundations on layered soils under inclined load
Authors: Meyerhof G. G. , Hanna A. M.
Published: August 2008

The ultimate bearing capacity of footings resting on subsoils consisting of two layers has been investigated for the cases of a dense or stiff layer overlying a weak deposit, and a loose or soft layer overlying a firm deposit. The analyses of different modes of soil failure are compared with the results of model tests on circular and strip footings on layered sand and clay soils.
Results of a program of instrumentation involving a precast segmented concrete-lined tunnel in clay
Authors: Belshaw D. J. , Palmer J. H. L.
Published: August 2008

In Thunder Bay, Ontario, a 2.16 m diameter tunnel is nearing completion in a soft to firm clay using a full-face tunnel boring machine and an unbolted precast segmented concrete lining. The lining consists of rings composed of four trapezoidal sections of unreinforced concrete, 1 m in length and 11 cm thick. Each ring is assembled within the protection of the tailpiece of the tunnel boring machine and clay grout is injected behind the ring as the machine advances by thrusting on the completed lining.Because of the uniqueness of this method of construction, an extensive field instrumentation program was undertaken to evaluate the tunnelling procedure and the performance of the completed tunnel. The first phase of instrumentation involved a 60 m length of the tunnel and included observations of ground surface deformation, soil deformation (as measured by slope indicators, magnetic extensometers, and deep settlement points), total pressure on the lining, and deformation of the lining. The information also included tunnelling procedure and weight of spoil removed as the tunnel boring machine passed through the instrumented area.These observations are presented and discussed. Some problems of instrumentation are considered, particularly as they related to the second array of instrumentation which was designed to provide detailed information on spatial deformations and pore pressure changes.
Influence of number of cycles on strain
Authors: Khosla Vijay K. , Singh Ram D.
Published: August 2008

In the past, tests conducted on sand to evaluate the field performance of machine foundations have utilized only a limited number of load cycles. Results of these tests were extrapolated to determine the permanent deformation experienced by the foundation materials over the life of the machines. An attempt has been made in this presentation to develop a complete spectrum of the variation of strain with stress level and number of loading cycles for anisotropically consolidated Ottawa sand. Up to 10 million stress cycles were applied. The axial strains show three distinct stages of strain with number of cycles.
Bearing capacity of anisotropic cohesionless soils
Authors: Meyerhof G. G.
Published: August 2008

Previous test results of the anisotropic shear strength of cohesionless soils are reviewed. The theory of the ultimate bearing capacity of shallow foundations on homogeneous isotropic soils is extended to anisotropic cohesionless soils. The proposed method of analysis is compared with the results of some load tests on anisotropic sand. An extension of this method to foundations under inclined load is briefly discussed.
Terrestrial photogrammetry for measuring pile movements
Authors: Bozozuk M. , Wijk M. C. Van , Fellenius B. H.
Published: August 2008

Terrestrial photogrammetry was used to monitor, movements of previously driven piles during the installation of 116 concrete piles in sensitive marine clay. The technique and the equipment used are described and the sources of error discussed.
Ice sheet loads on marina piles
Authors: Doud Jerry O.
Published: August 2008

Two marina piles were instrumented with steel sleeves. The steel sleeves were fixed rigidly to the top of the piles. The bottoms of the sleeves were free to freeze into the ice sheet. Two transducers were placed on each sleeve above the water level to measure the vertically acting tension and compression forces imposed on the pile by the ice sheet. The testing took place during two winters at Ontonagon, Michigan, U.S.A.It was found that the fluctuating water level in the lake can produce large cyclical loads and that the vertical loading rate that an ice sheet imposes on a marina pile can be significant.
Downslope movements at shallow depths related to cyclic pore-pressure changes
Authors: Eigenbrod K.D.
Published: August 2008

Slow, shallow ground movements in a slope near Yellowknife caused excessive tilting of timber piles that supported an engineering structure. To avoid damage to the structure, the pile foundations had to be replaced by rigid concrete piers that were designed to resist the forces of the moving soil mass. Downhill movements were rather slow and, during an initial inspection, were indicated only by soil that was pushed up against a series of piles on their uphill sides, while gaps had formed on their downhill sides. No open cracks or bulging was observed on the slope. A stability analysis indicated that the slope was not in a state of limit equilibrium. To obtain a better understanding of the creep movements in the slope and their effect on the rigid concrete piers, extensive instrumentation was carried out after the construction of the piers. This included slope indicators, piezometers, thermistors, and total-pressure cells against one of the concrete piers. In addition, a triaxial testing program was undertaken in which the effect of cyclic pore-water pressure changes on the long-term deformations of the shallow clay layer was investigated. From the data collected in the field and laboratory, it could be concluded that (i) tilting of the original timber piles was caused by downslope movements related to cyclic pore-water increases; (ii) the lateral soil movements increased almost linearly with depth from 2 m below the ground surface, with no indication of a slip surface; and (iii) the pressures exerted by the moving soil mass against the rigid concrete piers within the soil mass were equal to the passive resistance activated within the moving soil mass. Key words : soil creep, slope movements, soil pressures, pore-water pressures, freezing pressures, permafrost, cyclic loading.
Analyses for the stability of potash tailings piles
Authors: Fredlund Delwyn G. , Zhang Zai Ming , Macdonald Karen
Published: August 2008

The stability of potash tailings piles is investigated using a pore-water pressure generation and dissipation model together with a limit equilibrium analysis. It is found that a shallow toe failure mode is generally the most applicable and that the stability may be influenced by pore-water pressure migration below the pile. It is suggested that field studies would be useful in evaluating stability in the toe region of the pile. Key words : potash tailings, slope stability, pore pressure dissipation, solutioning.
Distribution of saline permafrost in the Northwest Territories, Canada
Authors: Hivon E.G. , Sego D.C.
Published: August 2008

Saline permafrost has a detrimental impact on the performance of foundations. Increased pore-water salinity decreases the strength and increases the deformation susceptibility of permafrost and foundations installed in permafrost. A data base of the distribution of saline permafrost in the Northwest Territories shows high pore-water salinities beneath coastal communities and at locations along the upper Mackenzie Valley and within the Mackenzie Delta. Salinity of inland sites is usually low. High salinities are usually associated with ice-poor materials and are linked with previous marine submergence associated with glacial events. Key words : permafrost, saline distribution, measurements, Quaternary geology.
Ultimate bearing capacity of shallow foundations on sand with geogrid reinforcement
Authors: Omar M.T. , Das B.M. , Puri V.K. , Yen S.C.
Published: August 2008

Laboratory model test results for the ultimate bearing capacity of strip and square foundations supported by sand reinforced with geogrid layers have been presented. Based on the model test results, the critical depth of reinforcement and the dimensions of the geogrid layers for mobilizing the maximum bearing-capacity ratio have been determined and compared. Key words : bearing capacity, geogrid, model test, reinforced sand, shallow foundation.
Influence of starch polysaccharide on the remoulded properties of two Indian clay samples
Authors: Rao Sudhakar M. , Sridharan A. , Shenoy M.R.
Published: August 2008

The reported presence in marine clays and the recognized role of polysaccharide as a bonding agent provided the motivation to examine the role of starch polysaccharide in the remoulded properties of nonswelling (kaolinite) and swelling (bentonite) groups of clays. The starch polysaccharide belongs to a group of naturally occurring, large-sized organic molecules (termed polymers) and is built up by extensive repetition of simple chemical units called repeat units. The results of the study indicate that the impact of the starch polysaccharide on the remoulded properties of clays is dependent on the mineralogy of the clays. On addition to bentonite clay, the immensely large number of segments (repeat units) of the starch polysaccharide create several polymer segment – clay surface bonds that cause extensive aggregation of the bentonite units layers. The aggregation of the bentonite unit layers greatly curtails the available surface area of the clay mineral for diffuse ion layer formation. The reduction in diffuse ion layer thickness markedly lowers the consistency limits and vane shear strength of the bentonite clay. On addition to kaolinite, the numerous polymer segment – clay surface bonds enhance the tendency of the kaolinite particles to flocculate. The enhanced particle flocculation is responsible apparently for a small to moderate increase in the liquid limit and remoulded undrained strength of the nonswelling clay. Key words : soil organics, polysaccharides, starch, polymers, bentonite, kaolinite, Atterberg limits, vane strength, interparticle forces.
Conventional and centrifuge model studies of the moment carrying capacity of short pier foundations in clay
Authors: King G.J.W. , Laman M.
Published: August 2008

An experimental investigation into the moment carrying capacity of short rigid pier foundations in saturated clay is described. Scale models of square piers with different breadths and depths were used in both conventional and centrifugal studies. The results show that the relationships between moment and rotation are nonlinear but do not exhibit any peak values, and that moment limits, defined by limiting angular rotations, increase with increases in pier depth and breadth. Empirical equations are derived between moment carrying capacity and pier geometry, for a range of limiting rotations, and a very close fit is demonstrated between the moment–rotation relationships obtained using these equations and the actual data obtained from the model tests. It is shown that, at the same pier rotations, the moment carrying capacities observed in the centrifugal model tests are significantly larger than those in the conventional model tests. Numerical analyses of the prototype geometries were also carried out using a three-dimensional nonlinear finite-element computer program. The results are shown to provide satisfactory agreement with the moment–rotation behaviour and working limits observed in the centrifuge model tests. Thus, even though conventional modelling is usually legitimate for determining the immediate bearing capacity of rigid foundations in saturated clay, their rotational stability is shown to be significantly affected by self-weight stresses. Some of the existing methods for designing short piers subjected to moments are examined and compared with the results from the centrifuge model tests. Key words : pier foundation, clay, moment capacity.
Simulation of creep deformation in the foundation of Tar Island Dyke
Authors: Morsy Mohammed M. , Morgenstern N.R. , Chan D.H.
Published: August 2008

Tar Island Dyke is a 92 m tailing dyke for retaining oil sand tailings and has been operated by Suncor in Fort McMurray, Alberta. Construction of the dyke began in the mid-1960's adjacent to the Athabasca river. The foundation of the dyke consists of a layer of interbedded silts and clay overlying a basal sand stratum. Stresses imposed by the dyke on the foundation clay have been causing continuing movement of the structure over 30 years. Movements of the dyke have been monitored for over 25 years and show significant creep deformation of over 1 m in the foundation clay. Pore pressure in the clay was monitored, with little pore pressure change during this period. Therefore the movement was mostly due to creep rather than consolidation. The unique feature of this case is that the loading due to the dyke has been essentially constant for over 15 years but movement has continued. An effective stress model for creep is adopted to simulate the construction of the Tar Island Dyke. The model is based on critical state soil mechanics and uses secondary consolidation and the Taylor Singh-Mitchell creep relationships. The model is able to capture the movement of the dyke and its foundation, and good agreement is obtained between the calculated and measured deformations. A sensitivity study has been carried out to study the effect of varying the creep parameters on the results of the analysis. Key words : Tar Island Dyke, creep mechanism, finite element, clay foundation, effective stress model, pore-water pressure.
Influence of inertia on falling weight deflectometer (FWD) test response
Authors: Stolle Dieter F.E. , Sedran Gabriel
Published: August 2008

This note addresses the appropriateness of adopting an elastostatic model for backcalculating in situ layer moduli from falling weight deflectometer (FWD) data. By approximating the elastodynamic displacement field using an elastostatic solution for a given load distribution, it is shown via Ritz vector analyses that elastostatic fields do not accurately represent the displacements associated with pavements subjected to FWD-type loading. Some improvement is, however, possible by including first-order corrections for inertial forces. The main conclusion stemming from the analyses is that elastostatic models should not be used to estimate in situ moduli. Key words : pavement, elastodynamic analysis, Ritz vectors, back-calculation, structural integrity.
Experimental evaluation of a test base for ship engines
Authors: Rezende Lopes Francisco de , Ribeiro Mariza Gomes
Published: August 2008

During the test and running-in of some ship engines in a heavy industry, severe vibrations, of a magnitude that impeded precision work in other areas of the industry, were observed. Vibration measurements were carried out during the test of an engine that confirmed previous suspicions that resonance occurred during the test of some engine models. These measurements led to the determination of dynamic properties of the foundation soil, which allowed the computation of the resonant frequencies of other engine models, so as to avoid these frequencies during their tests. Key words : dynamics, foundations, instrumentation, analysis.
Estimation of lateral wall movements in braced excavations using neural networks
Authors: Goh A.T.C. , Wong K.S. , Broms B.B.
Published: August 2008

The growing interest in neural networks among geotechnical engineers is due to its excellent performance in modelling nonlinear multivariate problems. This paper demonstrates that neural networks can synthesize data derived from finite element studies on braced excavations in clays and capture the nonlinear interactions between the variables in the system. The neural network was able to produce reasonably accurate wall displacement predictions after "learning" from examples derived from finite element analyses. This method has the advantage over other more conventional methods in that it can be readily retrained as additional data from finite element studies and actual field records are acquired. Key words : braced excavation, finite element analysis, neural networks, retaining walls, soft clay, wall displacement.
An experimental examination of the critical state and other similar concepts for granular soils
Authors: Chu J.
Published: August 2008

Measuring the critical state parameters of dense granular soil by drained triaxial tests is problematic, as significant nonhomogeneous deformations can develop prior to approaching a critical state. This leads to further questions on the verification of the critical state concept for granular soils. In this study a new testing method, which enables the critical state of dense sand to be measured in the homogeneous deformation region, was adopted to measure the critical state of dense sand and to examine the critical state concept. A series of experiments was carried out to measure the critical state for dense, medium dense, and loose sand. The test results show that although a unique critical state curve may exist, the critical state friction angle is not constant but stress level dependent. The other similar concepts, namely, the phase transformation state, the characteristic state, and the steady state, were also examined, and the relationships among these states were established. Key words : critical state, granular soils, stress path, stress–strain behaviour, triaxial test.