bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic structure, migration, and patterns of allelic richness among coho salmon (Oncorhynchus kisutch) populations of the Oregon coast
Authors: Johnson Marc A. , Banks Michael A.
Published: June 2008

Genotypic data from eight microsatellite loci are used to infer population structure, effective population size, migration rates, and patterns of allelic richness among wild and hatchery populations of Oregon coastal coho salmon ( Oncorhynchus kisutch ). Corroborating the results of a previous study, we found relatively weak genetic structure among coho from different river basins, although some geographically and ecologically defined clades are supported. Contemporary migration rates among basins appear to be high and asymmetrical. Hatchery populations tended to resemble the wild populations from which they were founded, but presented significantly lower levels of allelic richness. Allelic richness was also low in Oregon coastal lake populations and peaked in the central region of the evolutionarily significant unit among wild river populations. We suggest that the observed patterns may reflect both current source–sink dynamics and post-Pleistocene colonization events.
Accounting for biological and physical sources of acoustic backscatter improves estimates of zooplankton biomass
Authors: Warren Joseph D. , Wiebe Peter H.
Published: June 2008

To convert measurements of backscattered acoustic energy to estimates of abundance and taxonomic information about the zooplankton community, all of the scattering processes in the water column need to be identified and their scattering contributions quantified. Zooplankton populations in the eastern edge of Wilkinson Basin in the Gulf of Maine in the Northwest Atlantic were surveyed in October 1997. Net tow samples at different depths, temperature and salinity profiles, and multiple frequency acoustic backscatter measurements from the upper 200 m of the water column were collected. Zooplankton samples were identified, enumerated, and measured. Temperature and salinity profiles were used to estimate the amount of turbulent microstructure in the water column. These data sets were used with theoretical acoustic scattering models to calculate the contributions of both biological and physical scatterers to the overall measured scattering level. The output of these predictions shows that the dominant source of acoustic backscatter varies with depth and acoustic frequency in this region. By quantifying the contributions from multiple scattering sources, acoustic backscatter becomes a better measure of net-collected zooplankton biomass.
Long-term shifts in the species composition of a coastal fish community
Authors: Collie Jeremy S. , Wood Anthony D. , Jeffries H. Perry
Published: June 2008

To study decadal shifts in a coastal nekton community, we analyzed data on 25 fish and invertebrate species collected from 1959 to 2005 by the University of Rhode Island, Graduate School of Oceanography (Narragansett, Rhode Island, USA). This weekly trawl survey samples two locations: inside Narragansett Bay and in Rhode Island Sound. Over four decades, the community has shifted progressively from vertebrates to invertebrates and, especially since 1980, from benthic to pelagic species. Demersal species that declined include winter flounder ( Pseudopleuronectes americanus ), silver hake ( Merluccius bilinearis ), and red hake ( Urophycis chuss ); meanwhile warm-water fish (butterfish, Peprilus triacanthus ; scup, Stenotomus chrysops ) and invertebrates (lobster, crab, squid) increased with time. Total numbers reached a maximum in the 1990s, while mean body size decreased. Taxonomic diversity increased over time, as the community shifted from fish to invertebrates of several phyla. The shifts in species composition correlate most strongly with spring–summer sea surface temperature, which increased 1.6 °C over the 47-year time series. Species composition was also correlated with the winter North Atlantic Oscillation index and chlorophyll concentration, which has declined since the 1970s. Triggered primarily by rising temperatures, these decadal changes have altered the trophic structure of the nekton community, resulting in a shift from benthic to pelagic consumers.
An improved method for predicting the accuracy of genetic stock identification
Authors: Anderson Eric C. , Waples Robin S. , Kalinowski Steven T.
Published: June 2008

Estimating the accuracy of genetic stock identification (GSI) that can be expected given a previously collected baseline requires simulation. The conventional method involves repeatedly simulating mixtures by resampling from the baseline, simulating new baselines by resampling from the baseline, and analyzing the simulated mixtures with the simulated baselines. We show that this overestimates the predicted accuracy of GSI. The bias is profound for closely related populations and increases as more genetic data (loci and (or) alleles) are added to the analysis. We develop a new method based on leave-one-out cross validation and show that it yields essentially unbiased estimates of GSI accuracy. Applying both our method and the conventional method to a coastwide baseline of 166 Chinook salmon ( Oncorhynchus tshawytscha ) populations shows that the conventional method provides severely biased predictions of accuracy for some individual populations. The bias for reporting units (aggregations of closely related populations) is moderate, but still present.
Incorporating environmental variability in stock assessment: predicting recruitment, spawner biomass, and landings of sprat (Sprattus sprattus) in the Baltic Sea
Authors: MacKenzie Brian R. , Horbowy Jan , Köster Fritz W.
Published: June 2008

Temperature has a significant positive impact on recruitment of sprat, Sprattus sprattus, in the Baltic Sea. Here we evaluate whether an existing recruitment model for the year classes 1973–1999 can forecast recruitment for five new year classes. The coefficient of variation (CV) of predictions was 5%, and four of five new year classes were within 95% confidence limits of predictions made by the earlier model. We then assimilated climatic, oceanographic, and recruitment linkages and their uncertainty into the standard International Council for the Exploration of the Sea (ICES) assessment procedure to predict key advisory-related variables such as spawning stock biomass (SSB) and landings. These linkages enable a forecast of recruitment earlier than the annual assessment meeting. Forecasts made using the North Atlantic Oscillation to predict the 2006 year class showed that spawner biomass would be 15% lower than spawner biomass calculated using the ICES standard methodology. The difference in perception of future biomass does not affect the advice for the stock because the spawning stock biomass is greater than the critical biomass limit (SSB > BPA). However, when this is not the case or when it is desirable to broaden the ecosystem basis for fisheries management, incorporation of knowledge of recruitment processes may be beneficial.
Uncertainties in population dynamics and outcomes of regulations in sockeye salmon (Oncorhynchus nerka) fisheries: implications for management
Authors: Holt Carrie A. , Peterman Randall M.
Published: June 2008

Fisheries managers usually have multiple options available but are often unclear on how to choose among them owing to uncertainties in biological and management components of fisheries systems. We evaluated the performance of current and possible future assessment and management practices for sockeye salmon ( Oncorhynchus nerka ) in British Columbia and Alaska by using a computer model that included major biological and management components and their associated uncertainties (interannual variability in recruitment, age-at-maturity, and sex ratio, as well as uncertainty in observations of spawner abundances, forecasts of recruitment, and outcomes from implementing management regulations). One option for management practices that we evaluated was designed to make the forecasting model more realistic by accounting for long-term trends in age-at-maturity. A second option was designed to reduce deviations between management targets and actual or “realized” harvest levels. We found that compared with practices that ignore those sources of uncertainty, the second option produced annual catches that were higher, on average, and less variable over time while maintaining recruitment above critical conservation levels. Contrary to our expectations, the first modification did not result in comparable benefits. Our results demonstrate the value of using simulation models to evaluate potential modifications to Pacific salmon management practices.
Quantifying invasion pathways: fish introductions from the aquarium trade
Authors: Gertzen Erin , Familiar Oriana , Leung Brian
Published: June 2008

Introduced species can cause economic and environmental harm. Researchers have developed risk assessment models for exotic species based on biological characteristics. However, few have quantified propagule pressure despite its relevance for establishment. Both are needed to identify invasion risk. We focused on fishes introduced via the aquarium trade, because this pathway transports thousands of species throughout the world. We developed an approach to estimate propagule pressure by (i) identifying and quantifying aquarium fishes sold, (ii) determining fish owner behavior and disposal practices, and (iii) quantifying uncertainty. We used the St. Lawrence Seaway as our model system. Only one nonestablished species ( Tanichthys albonubes , 117 per year) had the propagule pressure and environmental tolerances to likely invade this region. However, overall, more than 10 000 fishes were released annually from Montréal (Quebec, Canada) alone. The implication of the observed propagule pressures is that the aquarium trade should be a very important pathway in other warmer habitats and should be explicitly assessed. Knowledge of the numbers introduced of each species will be useful for population models to estimate the probability of establishment.
Salmon carcasses as a marine-derived resource for benthic macroinvertebrates in a developing postglacial stream, Alaska
Authors: Monaghan Kieran A. , Milner Alexander M.
Published: June 2008

Streams formed in Glacier Bay, southeast Alaska, following glacial recession rapidly support populations of spawning salmon. Using both observational and experimental approaches, we examined the importance of pink salmon ( Oncorhynchus gorbuscha ) carcasses for benthic macroinvertebrate communities, approximately 10 years after salmon first colonized Wolf Point Creek, a first-order, lake-fed stream. Macroinvertebrate abundance on carcasses naturally accumulating in the stream channel was low, dominated by chironomids ( Eukiefferiella spp.). Macroinvertebrate drift was significantly lower from artificial experimental channels containing salmon flesh (P < 0.001) compared with channels without. However, the density and community structure of macroinvertebrates colonizing rock baskets in channels was not significantly different between treatments. In a separate experiment, colonization of substrate trays with salmon and control (inert) fillets were associated with differences in community structure; simuliids dominated control fillets, and chironomids dominated fish fillets, while underlying stone substrate was colonized by a more diverse community including Ephemeroptera, Plecoptera, and Trichoptera taxa (EPT). Excluding simuliids, abundance was significantly higher on fish compared with control fillets (P < 0.001). These data suggest that scales and mucus prevent the direct consumption of flesh from whole carcasses, highlighting the role predators–scavengers in facilitating flesh consumption by benthic macroinvertebrates.
Estimating walleye (Sander vitreus) density, gear catchability, and mortality using three fishery-independent data sets for Oneida Lake, New York
Authors: Irwin Brian J. , Treska Theodore J. , Rudstam Lars G. , Sullivan Patrick J. , Jackson James R. , VanDeValk Anthony J. , Forney John L.
Published: June 2008

We used three long-term data sets (gill nets, trawls, and adult population estimates) for walleye ( Sander vitreus ) to simultaneously estimate density, gear catchabilities, and mortality using an age-structured, nonlinear model. Model constraints included a fixed natural mortality rate and age- and gear-specific but time-invariant catchabilities. Trawl catchability decreased with age, whereas gillnet catchability increased towards a maximum by age-4. A sensitivity analysis was conducted to investigate how the information content of the different data sets influenced parameter estimates. Estimated catchability values were relatively robust to changes in data weighting. Estimated gillnet catchability values were fairly consistent with those derived from more conventional methods. An additional mortality term was added to reflect double-crested cormorant ( Phalacrocorax auritus ) predation, and vulnerabilities associated with angling and cormorants were calculated using independent length frequency information. Estimated subadult mortality increased and the influence of fishing mortality slightly decreased during recent years when double-crested cormorants were abundant and more restrictive size limits were in place. Walleye density in Oneida Lake (New York, USA) in the last decade is estimated to be approximately half of that before 1990.
Can bottom trawling disturbance increase food production for a commercial fish species?
Authors: Hiddink Jan Geert , Rijnsdorp Adriaan D. , Piet Gerjan
Published: June 2008

Fishery closures and marine protected areas are increasingly being used as tools to achieve sustainable fisheries. The “plaice box”, a gear restriction area in the North Sea that was established to reduce the bycatch of undersized plaice ( Pleuronectes platessa ), is considered ineffective because there has been a shift in the distribution of juvenile plaice to the waters that remained open to bottom trawlers. Here we examine the hypothesis that bottom trawling benefits the small benthic invertebrates that form the food source for plaice and that the plaice box had a negative impact on food production for plaice. A size-based model of benthic communities indicates that the production of prey was low without trawling and maximal in areas that are trawled once to twice a year. Therefore, bottom disturbance may improve the feeding conditions for species that feed on small invertebrates. As plaice aggregate at the locations with the highest benthic biomass, this may explain the observed redistribution to areas outside the plaice box. We conclude that the plaice box may not have been the most appropriate measure to protect plaice from discarding and that the species’ ecology should be considered when choosing the most appropriate management measure to achieve an objective.
Evaluation of the human health threat associated with the hepatotoxin microcystin in the muscle and liver tissues of yellow perch (Perca flavescens)
Authors: Wilson Alan E. , Gossiaux Duane C. , Höök Tomas O. , Berry John P. , Landrum Peter F. , Dyble Julianne , Guildford Stephanie J.
Published: June 2008

During the summer of 2006, the western basin of Lake Erie experienced a bloom of the toxigenic cyanobacterium Microcystis aeruginosa . Across 11 sites, intracellular, particulate-bound microcystin levels in the seston increased to levels that exceeded World Health Organization guidelines for drinking water exposure (1 µg toxin·L–1). In contrast, toxin concentrations in yellow perch ( Perca flavescens ) muscle tissue (n = 68) declined from June to August, were negatively related to algal toxin levels, and never exceeded a conservative chronic exposure concentration estimated using proposed United States Environmental Protection Agency (US EPA) guidelines. Microcystin concentrations in yellow perch liver exceeded US EPA chronic exposure guidelines, were on average 125 times higher than muscle toxin concentrations per unit dry weight, and varied little throughout the summer. With current guidelines, humans do not appear to be at risk when consuming the muscle tissue of Lake Erie yellow perch collected during large-scale cyanobacterial blooms. However, this study highlights the need for a better understanding of the trophic transfer of cyanobacterial toxins through aquatic food webs in diverse ecosystems with an emphasis on understanding if these compounds could accumulate sufficiently to affect human health.
The effects of barotrauma on the catch-and-release survival of southern California nearshore and shelf rockfish (Scorpaenidae, Sebastes spp.)
Authors: Jarvis Erica T. , Lowe Christopher G.
Published: June 2008

Two experiments were used to assess the effects of barotrauma on initial capture survival and short-term postrecompression survival of line-caught (range 18–225 m) southern California rockfish ( Sebastes spp.). Occurrence of external and internal signs of barotrauma was characterized across all species. Despite species-specific differences in the extent of barotrauma observed, initial capture survival of rockfish held in a live well for a 10-min period following capture was 68% overall (19 species, n = 168). Overall 2-day survival of rockfish following recompression in cages was also 68% (17 species, n = 257). Short-term survival varied across species (range 36% to 82%), as did the occurrence of external signs of barotrauma. The degree of external signs of barotrauma was not a significant predictor of initial capture survival or short-term survival. The most significant predictor of short-term survival was surface holding time, with short-term survival increasing with decreasing surface holding time. These results suggest that rapid recompression of rockfish can significantly decrease discard mortality and could potentially enhance rockfish conservation.
Sandeel (Ammodytes marinus) larval transport patterns in the North Sea from an individual-based hydrodynamic egg and larval model
Authors: Christensen Asbjørn , Jensen Henrik , Mosegaard Henrik , St. John Mike , Schrum Corinna
Published: June 2008

We have calculated a time series of larval transport indices for the central and southern North Sea covering 1970–2004, using a combined three-dimensional hydrodynamic and individual-based modelling framework for studying sandeel ( Ammodytes marinus ) eggs, larval transport, and growth. The egg phase is modelled by a stochastic, nonlinear degree-day model describing the extended hatch period. The larval growth model is parameterized by individually back-tracking the local physical environment of larval survivors from their catch location and catch time. Using a detailed map of sandeel habitats in the North Sea, the importance of hydrography for early life stages of sandeel to their recruitment success is explored. We find that the sandeel larval transport patterns in the North Sea are relatively robust toward uncertainties in biological parameters, when mortality aspects are included. We find only weak spatiotemporal correlations between elements of the transport indices in the time series, mainly positive correlation between retention terms for the same year. The transport connectivity of sandeel habitats in the North Sea and the dynamical properties of the North Sea transport system are also analyzed, and we introduce novel a scheme to quantify direct and indirect connectivity on equal footings in terms of an interbank transit time scale.
The shear strength of unsaturated soils
Authors: Fredlund D. G. , Morgenstern N. R. , Widger R. A.
Published: June 2008

The shear strength of an unsaturated soil is written in terms of two independent stress state variables. One form of the shear strength equation is[Formula: see text]The transition from a saturated soil to an unsaturated soil is readily visible. A second form of the shear strength equation is[Formula: see text]Here the independent roles of changes in total stress σ and changes in pore-water pressure uw are easily visualized.Published research literature provides limited data. However, the data substantiate that the shear strength can be described by a planar surface of the forms proposed. A procedure is also outlined to evaluate the pertinent shear strength parameters from laboratory test results.
Soil disturbance from pile driving in sensitive clay
Authors: Bozozuk M. , Fellenius B. H. , Samson L.
Published: June 2008

Soil disturbance due to the driving of two groups of 116 concrete piles each in sensitive marine clay was studied on a construction project in eastern Canada. Pore-water pressures, heave, and lateral movement of soil and piles, and tests of strength, compressibility, and consistency limits of the soil were observed prior to and up to 3 months after pile driving whereas observations of pore-water pressures were continued for an additional 5 months. Driving of the piles had little effect on the compressibility and consistency limits of the marine clay, but the in situ shear strength and cone penetration resistance were reduced by about 15 and 30%, respectively. Soil heave within the group of piles decreased linearly with depth from a maximum of 450 mm (18 in.) at the ground surface to about zero at the pile tips, and in volume amounted to approximately 55% of the soil displaced by the piles. The vertical heave outside the pile group was confined to a horizontal distance of 12 m (39 pile diameters). During pile driving, the lateral movement of previously driven piles was as much as 175 mm (7 in.). Horizontal soil movements measured by inclinometers varied up to 125 mm (5 in.). Pore-water pressures generated during piling exceeded the total overburden pressure by 35–40%. The excess pore pressures dissipated in about 8 months after the piling was completed.
The geology and geotechnical properties of till and related deposits in the Edmonton, Alberta, area
Authors: May R. W. , Thomson S.
Published: June 2008

Deposits of the Quaternary Period in the Edmonton area consist of a lower and an upper till, in places separated stratigraphically by a sand, with lacustrine clays, silts, and sands overlying this sequence. Detailed field investigations suggest the possible existence of complexities that have not been fully integrated into an understanding of the Quaternary history of the Edmonton area.The lower till is a moderately stony sandy silt till. In places the upper portion has been reworked or sheared by the ice that deposited the upper till producing a thin zone of slightly lower strength. The upper till is a moderately stony sand till. Regionally it appears to be quite variable lithologically and contains inclusions of sand and gravel; therefore it is more reasonable to think in terms of an upper till unit composed of till and genetically related material. In some localities this upper unit is one single bed of till; in other places, however, it is a layered sequence of paratills, sands, and silts resulting probably from deposition in standing water. The lenses of sand and gravel associated with this unit have caused problems in tunnelling operations and other construction as they contain water, which can cause flooding when encountered during excavation. The paratills known from the examination of outcrops consist of sequences of interbedded till-like material and sands. These sequences are probably the result of turbidite deposition in an ice-marginal lake. These materials would resemble till when encountered in drilling operations.Problems associated with the Quaternary deposits of the Edmonton area include borehole interpretation to develop site stratigraphy, and the determination of geotechnical properties of the deposits and an assessment of their local variation over a specific site. Also of concern are the joints and fractures in the deposits, which affect slope stability and permeability of the soil mass.An understanding of the Quaternary history and the intrinsic variability of the deposits formed predominantly under the influence of ice is necessary for an understanding of potential sources of variability in geotechnical properties. Interaction between the geologist and the geotechnical engineer can only enhance their mutual comprehension of potential problems and their solutions.
Regional distribution of in situ horizontal stresses in rocks of Southern Ontario
Authors: Lo K. Y.
Published: June 2008

Some structures built in different rock formations in Southern Ontario have been subjected to various degrees of distress. These case histories include heaves of quarry bottoms, buckling of concrete lining of canal floors, cracking of concrete lining of tunnels at the springline, and long term movement of the walls of unsupported excavations.Inference from these case histories, together with direct measurements of in situ stresses, indicate that high horizontal stresses exist in the Silurian and Ordovician rocks. The magnitude of the maximum stress in the horizontal plane varies from 6–14 MPa depending on the depth and rock type.Excavations in rock relieve the in situ stresses. The stress relief serves as an initiating mechanism for time-dependent deformation to occur leading to the process loosely termed as 'rock squeeze'. It appears, therefore, that due consideration must be given to this prevalent phenomenon for the design of underground structures in rock in this region.
Shear strength of soft fissured clays
Authors: Rivard P. J. , Lu Y.
Published: June 2008

Case histories of failure of water-retaining structures on highly plastic clay indicate that the intact strength of the clay does not reliably predict the stability condition. A study of the foundation conditions revealed the presence of structural discontinuities such as nugget and blocky structure, joints, fissures, and slickensides. A re-analysis of the failures, using the normally consolidated strength of the soft highly plastic clay, as suggested by Skempton and Hutchinson for stiff fissured clays, gives a more reliable prediction of the in situ stability condition.
Geotechnical characteristics of compacted clays for earth embankments in the Prairie provinces
Authors: Rivard P. J. , Goodwin T. E.
Published: June 2008

The geotechnical characteristics of compacted soils used by the Prairie Farm Rehabilitation Administration in earth embankments were correlated with easily obtained soil properties.Relationships were established between Standard Proctor maximum density and optimum water content versus liquid limit for clay soils. In addition, a relationship was established to determine the Standard Proctor maximum dry density and optimum water content using the results from the one-point Proctor test for clay, and sand and silt soils.Effective shear strength parameters and consolidation characteristics of compacted samples were related to liquid limit, water content, and dry density. The results of field and laboratory measurements of pore pressure were used to relate the pore pressure coefficients U/σ3 and U/σ1 to the deviation of water content from optimum water content and applied stress. A relationship was established between embankment compression and embankment height using field measurements of embankment settlement.The data suggest that similar geotechnical characteristics will be obtained for laboratory and field compacted alluvial and glacial soils when they are placed with Standard Proctor compactive effort at similar water contents, densities, and liquid limit. In this paper 'alluvial clay' is used to describe clays deposited in lacustrine or fluvial environments and 'glacial clay' is used to describe clays deposited by a glacier.
Creep behaviour of an undisturbed lightly overconsolidated clay
Authors: Tavenas F. , Leroueil S. , Rochelle P. La , Roy M.
Published: June 2008

To fill an important gap in the knowledge of creep phenomena, the creep behaviour of the intact, overconsolidated Saint-Alban clay has been investigated by means of drained and undrained triaxial tests as well as of odometer tests.Creep deformations can be broken into volumetric and shear components. The development with time of both volumetric and shear strains can be represented by means of the phenomenological equation proposed by Singh and Mitchell in 1968. However, the stress function in that equation must be defined separately for each strain component and by reference to the limit state of the clay.A general model of the time dependent behaviour of clays might be obtained by combining the concepts of limit state and isotaches, as implied in the YLIGHT model proposed by Tavenas and Leroueil in 1977 but the effect of overconsolidation on the shape of the isotaches requires further investigation.
A technique for measuring radial deformation during repeated load triaxial testing
Authors: Cole David M.
Published: June 2008

A system of non-contacting displacement transducers has been used to record radial deformation in repeated load triaxial tests. Operating principle, system capabilities, and installation technique are discussed. Results of tests on clay and silt subgrade materials are presented and Poisson's ratio is calculated directly from test data.
Load bearing slurry trench wall supported by glacial till
Authors: Rosenberg Peter , Journeaux Noel L.
Published: June 2008

The University of Quebec Campus expansion in downtown Montreal occupies three city blocks. The complex consists of interconnected buildings varying from 3 to 10 stories in height with two basements. The internal columns of the superstructure are founded on footings and caissons. The peripheral walls are carried on a slurry trench excavated, tremie concreted wall, which also served as the earth retaining structure during construction. There are no records available on soil supported slurry walls in Canada although it is a common system in Europe.The slurry trench tremie concrete wall could have been extended to bedrock and the loads carried on rock; however, the amount of increased wall area was significant. Support in the till would result in large savings; however, this required the determination of the bearing capacity and compression characteristics of the till.Tests were carried out to determine concrete-to-till friction, both with and without bentonite slurry on the till-to-concrete surface contact. In addition, the end bearing capacity of the till was obtained by plate load tests.This paper gives the results of the tests carried out, compares them to similar results reported in the literature, and gives the design solution adopted.
Two-dimensional pollutant migration in soils of finite depth
Authors: Rowe R. Kerry , Booker John R.
Published: June 2008

A technique for analyzing two-dimensional migration of contaminant from a landfill into a homogeneous clayey layer is described. The analysis takes acount of the fact that the concentration of contaminant in the landfill will decrease as contaminant is transported into the soil. The analysis also allows for advective–dispersive transport within a permeable stratum (aquifer), which underlies the homogeneous layer. Consideration is given to chemical retardation arising from sorption/desorption of contaminant in the clayey layer. Some of the more important effects arising from the use of a 2-D analysis are illustrated by means of a limited parametric study. It is shown that the diffusion of contaminant from the aquifer into the clayey layer will substantially reduce the concentrations of contaminant in the groundwater away from the landfill. It is also shown that there is a critical velocity in the aquifer at which the maximum concentration at a point occurs. At greater or lesser velocities, significantly smaller concentrations may result. Thus design for limiting velocities is not necessarily conservative. Finally, the results of the 2-D analysis are compared with those from a 1-D analysis and the applicability of 1-D solutions is discussed. Key words: contaminant migration, analysis, soil, diffusion, advection, pollutant.
Rock engineering for construction of Science North, Sudbury, Ontario
Authors: Franklin John A. , Pearson David
Published: June 2008

This paper presents a case study of rock engineering investigations, design, and construction work for the new Science North museum in Sudbury, Ontario. While the rock work is not particularly innovative, the building construction involved singular geotechnical requirements and problems.The building sits astride a major regional fault, which has a mapped length of 56 km, a throw of over 600 m, and a shear zone 30 m wide. Inclined drilling was used to locate and characterize the shears within this zone. The paper describes the site investigation and assesses the fault's history of movement and the potential for future fault activity.Architectural requirements included excavation of a "cavern" and entrance tunnel with exposed rock faces that were to appear rough yet remain stable. Given the sheared rock, the excavation required careful blasting. No shotcrete, mesh, or other visible forms of support were permitted. Instead, the rock was stabilized by "invisible" fully resin-bonded dowels. Anchors with a working load of 500 kN each were used to pretension the piers to the rock and stabilize the rock faces beneath pier foundations. The paper describes the methods used to assess foundation bearing capacity and rock cut stability, to design the anchoring system, and to inspect and scale the footings, the tunnel, and the open-cut rock faces. Key words: rocks, foundations, blasting, site investigation, anchoring, bolting, slope stability, scaling, faults.
Pore pressure response analysis for earthquakes
Authors: Chugh Ashok K. , Thun J. Lawrence Von
Published: June 2008

Modifications and extensions made to the computer programs APOLLO and GADFLEA for studying the generation and dissipation of pore water pressure in soil deposits under earthquake loading are presented. The revised versions of these computer programs permit a fuller use of the analytically estimated site-specific earthquake response of soil deposits. These changes do not, however, alter the basic formulation of the problem and the solution strategies implemented in the computer programs APOLLO and GADFLEA. It is argued that the dynamic pore pressure response results obtained through these programs when used iteratively with the total stress ground response analysis should yield results close to the true effective stress ground response analysis for earthquake loading. Key words: pore pressure, earthquakes, soil dynamics, analysis, effective stress, computer programs, liquefaction.
Geologic control on soil composition and properties, Lake Ojibway clay plain, Matagami, Quebec
Authors: Quigley R. M. , Sethi A. J. , Boonsinsuk P. , Sheeran D. E. , Yong R. N.
Published: June 2008

Varved clays deposited in proglacial Lake Ojibway at Matagami, Quebec, were derived from two source areas: carbonate-deficient, Precambrian crystalline igneous rocks from New Quebec to the east and carbonate-rich Palaeozoic rocks from the James Bay lowlands in Ontario to the west. About 50% of the 12–15 m thick clay section consists of varved clays containing less than 3% carbonate, reflecting the New Quebec source. The remaining 50% of the section consists of two pulses of carbonate-enriched varves (15–30% carbonate) derived from rock flour in two glacial advances known as Cochrane I and Cochrane II, which advanced to within 20 km of Matagami.The clays are preconsolidated at the site by a combination of desiccation, groundwater level drawdown, and bonding, in such a way that σp′ is almost constant at 70 kPa at depths from 3.5 to 10 m.High in situ water contents correlate with thinner, low-carbonate, distal varves of high activity. The est correlations are obtained for relative activity, Ac(rel), defined as plasticity index ÷ specific surface area (Ip ÷ SS). Carbonate seems to have effectively neutralized smectite in the Cochrane proximal varves, rendering the distal varves (of New Quebec source) the most active clays at the site. Key words: varved clay, activity, carbonate, turbidity currents, glacial geology.
Erosivity of natural intact structured clay: Evaluation
Authors: Lefebvre Guy , Rohan Karol , Douville Serge
Published: June 2008

Previous studies on erodibility of cohesive soil are briefly reviewed and it is concluded that experimental observations have been mainly concerned with remolded and reconsolidated or weathered clays. The structure effect, which is considered important in the behaviour of natural intact clay, especially for Eastern Canadian clays, has not up to now been really considered in the evaluation of clay erodibility. This paper proposes a new laboratory technique for the study of the erodibility of natural intact clays and presents results of a testing program on three Canadian clays. The results indicate that Canadian structured clays are very resistant to erosion if intact and unweathered. Erosion is not taking place at the clay particle level but rather by the pulling out of larger elements composed of sand or silt grains or of clay aggregates. The pulling out of clay aggregates appears related to defects in the clay matrix, such as microfissures or planes of weakness associated with bedding. Key words: erosivity, intact clay, rate of erosion, tractive force, erosivity test, microstructure, macrostructure.
Rock slope movements in the Canadian Cordillera
Authors: Cruden D. M.
Published: June 2008

Some recent work on natural rock slope movements in the Cordillera is reviewed. Climate, geology, and seismicity combine to produce rockslides in the Mackenzies and Rockies; slower, more complex bedrock flows in the Omineca Belt; spreads and flows within the volcanics of the Intermontane Belt; and rockslides, falls, debris flows and earthflows in the Coastal and Insular Belts.Major rockslides occur on overdip slopes in sedimentary, metamorphic, and volcanic successions. Natural causes of the slides include erosion of the toes and lateral margins of the rock slopes, destruction of cohesion along discontinuities by physical weathering and solution, high pore-water pressures, and seismicity. Some of the rockslides from the Mackenzies and from the young volcanoes in the Coast Plutonic Complex have shown travel distances that are extremely high for their volumes.While no regional mapping of landslide risk has been carried out in the Cordillera, some regional mapping of landslides has been undertaken, usually as part of a surficial geology mapping program. Detailed studies of hazards have sometimes followed settlement rather than preceded it, though some useful maps of particular hazards have been produced. In two cases, landslide hazard has caused the relocation of communities. Key words: landslides, rockslides, spreads, flows, rockfalls, natural hazards, Cordillera, Rockies.
The liquefaction of sands, a collapse surface approach
Authors: Sladen J. A. , D'Hollander R. D. , Krahn J.
Published: June 2008

Recent large-scale slides occurring during the hydraulic placement of an artificial island berm in the Beaufort Sea resulted from the liquefaction of the berm sand. Subsequent laboratory tests and back analyses have led to advancements in the understanding of the liquefaction potential of sand. Analyses of undrained triaxial tests, undertaken to measure steady state parameters, suggest that there is a "collapse surface" in three-dimensional void ratio – shear stress – normal stress space. A necessary condition for liquefaction is that the soil state lie on this surface. This collapse surface concept is fundamentally an extension of the steady state concepts proposed by others, and in many respects follows the principles of critical state soil mechanics. Replotted published tests support the concept. Parameters used to describe the position of the surface are termed collapse parameters. These can be converted into parameters analogous to Mohr–Coulomb failure parameters and can therefore be used in conventional limit equilibrium stability analyses. Utilizing these parameters overcomes limitations inherent in previously proposed undrained steady state analysis methods. These concepts also provide a basis for a rational explanation of the Beaufort Sea hydraulic fill slides. Key words: liquefaction, sand, hydraulic fill, slope stability, steady state testing.
Back analysis of the Nerlerk berm liquefaction slides
Authors: Sladen J. A. , D'Hollander R. D. , Krahn J. , Mitchell D. E.
Published: June 2008

Five liquefaction slides occurred in 1983 during the construction of a hydraulically placed subsea sand berm designed to form part of a bottom-founded, offshore, hydrocarbon exploration platform at Nerlerk in the Canadian Beaufort Sea. These slides were triggered by simple static loading arising from the sand placement itself. Failures started at locally oversteepened side slopes and retrogressed to form bowl-shaped crests. The slide material came to rest beyond the berm at very flat slopes. Stability back analyses reveal that effective stress strength parameters consistent with limiting equilibrium are within the range of the collapse surface parameters determined from triaxial laboratory tests. This finding lends credibility to the collapse surface concepts introduced in another study. Back calculations show that the berm state prior to failure was much looser than the steady state, with the potential for a large strength loss. According to back calculations, the berm density was lower than that inferred from cone penetration tests. Key words: liquefaction, sand, hydraulic fill, slope stability, cone penetration testing.
Uplift capacity of circular plate anchors in layered soil
Authors: Stewart William
Published: June 2008

For anchors embedded in cohesive soil, the uplift capacity remains almost constant when the ratio of anchor embedment depth to anchor diameter (D/B) increases above about 4.5. The uplift capacity of anchors in cohesionless soil increases as D/B increases and the increase is greater with increased density of the cohesionless soil. Then, given that an anchor is embedded in cohesive soil, it may be possible to increase the uplift capacity of the anchor by placing a cohesionless overlay on the clay layer.The purpose of the model tests reported in this note was to investigate the effectiveness of placement of a cohesionless layer over a clay seabed in increasing the uplift capacity of a shallow anchor buried in the clay (D/B < 2.0). The sand overburden did increase the uplift capacity, but to obtain a substantial increase in capacity, a very large anchor displacement is required. In fact, the anchor had to displace through almost the entire clay layer before it mobilized the frictional resistance of the sand overlay. Key words: circular anchor, uplift, layered system.
Multiple loading method for field testing drilled piers
Authors: Horvath R. G.
Published: June 2008

A multiple loading testing method is suggested, which permits testing a single drilled pier foundation under three different conditions of load support. The pier may be tested under conditions of combined shaft and end-bearing resistance, end-bearing resistance only, and shaft resistance only. The advantages of this multiple loading test method include observation of the load-transfer and displacement behaviours of the pier under these three different support conditions and verification of the values obtained for the components of load support, i.e., shaft and end-bearing resistance, all from a single test pier.A special base load cell capable of performing a different function during each cycle of loading is required. A suitable load cell, consisting of a series of Freyssi flatjacks, and the method of operation are described.A multiple loading test procedure was used successfully as part of a field investigation program on full-scale pier sockets in weak shale. Data on the load-displacement behaviour of the pier tested using the multiple loading method are reported. Information concerning piers tested using conventional single loading methods are provided for comparison.The multiple loading test results were in good agreement with results obtained from conventional testing methods. Thus the multiple loading test method provides an economical means of obtaining a large amount of design information for drilled pier foundation systems, using a single test pier. Key words: field load test, multiple loading, drilled piers and caissons, shaft resistance, end-bearing resistance, combined shaft and end-bearing resistances, base load cell, shale.
Electrical freezing potentials and corrosion rates in clay sludge
Authors: Hanley Thos. O'D.
Published: June 2008

Electrical potentials and corrosive effects have been studied during the freezing of Regina clay, bentonite, and kaolin, natural or monoionic (treated with K+, Ca++, or Fe+++ions). A model is proposed for this effect in clay sludge. Freezing changed the corrosivity of the sludge samples, sometimes increasing the corrosion rate in the unfrozen portion by twofold or more. Key words: electrical freezing potentials, clay sludges, corrosion, freezing soils.
Characterizing spatial variability of a clay by geostatistics
Authors: Chiasson Paul , Lafleur Jean , Soulié Michel , Law K. Tim
Published: June 2008

This paper presents a characterization of the variability of a lightly overconsolidated and highly sensitive clay deposit located near Saint-Hilaire, 50 km east of Montréal. The geotechnical investigation consisted of in situ and laboratory tests. The variability of the in situ test results is the subject of this paper. The working hypothesis assumes that piezocone and vane test results may be modelled by a random function. This is done on the basis of a geostatistical approach. In situ vane and piezocone tests are found to increase with depth following a linear trend. This is a nonstationary problem and inference of the autocorrelation function must be made through the estimation of a generalized covariance. Results for both types of tests give the same shape of generalized covariance. Measurements made with both testing devices yield the same 2 m autocorrelation distance but the standard deviations are different. The standard deviations for the piezocone cone resistance, pore pressure behind the cone tip, and sleeve friction are 74, 34, and 2.1 kPa, respectively. Vane measurements have a standard deviation of 4.9 kPa. Results are also presented for the estimation of the vertical linear trend and for the statistical distributions of fluctuations. Key words : sensitive clay, spatial variability, stochastic representation, geostatistics, piezocone testing, vane testing.
Evaluation of jetting insertion for the self-boring pressuremeter
Authors: Benoît Jean , Atwood Michael J. , Findlay R. Craig , Hilliard Brian D.
Published: June 2008

The primary objectives of the self-boring pressuremeter (SPBM) test are to measure, in situ, the horizontal stress and the stress–strain characteristics of soils and soft rocks. This cylindrical probe tunnels itself into the ground with a minimum disturbance. Conventionally, the advance has been performed using a cutter system housed inside a cutting shoe. Although proven effective, this method is slow and cumbersome. In response to these drawbacks, a jetting insertion method was introduced and designed to allow a faster rate of insertion using a system that is less equipment intensive and easily adapted to conventional drill rigs. To avoid similar potential inconsistencies encountered in earlier SBPM testing with the cutting method, a series of laboratory simulation tests and in situ self-boring pressuremeter tests were carried out in two soft clay deposits to assess the jetting method. The following key insertion parameters were studied: jetting nozzle type, drilling fluid velocity, jetting nozzle position, rate of advance, and jetting flushing system. The results of this study indicate that, as with the cutting method, the jetting method can be used in soft to medium clays to advance the self-boring pressuremeter with minimum disturbance. Key words : self-boring pressuremeter, soft clay, horizontal stress, jetting, cutting.