bluuebunny/crossref_metadata_2025 huggingface dataset:
Knowledge-based advisory system for flexible pavement routine maintenance
Authors: Hanna Paulette B. , Hanna Awad S. , Papagiannakis Thomas A.
Published: January 2010

One of the most pressing problems facing Canada is the condition of roadway infrastructure. Making good maintenance decisions requires years of practical experience and judgement. Expert systems have great potential for solving pavement maintenance problems that usually require significant human expertise for solution. Expert systems, also known as knowledge-based systems, have been used as a means for conveying pavement maintenance knowledge gained through research and field experience to individuals responsible for maintaining asphalt pavements. An expert system is defined as an interactive computer program which documents judgement, experience, intuition, and other information in order to provide knowledgeable advice.This paper describes the development of PMAS, a pavement maintenance advisory system, which can assist highway engineers in planning effective flexible or asphalt concrete pavement maintenance strategies. The system uses two alternative commercial expert system shells. The system questions the user in a multiple-choice format in everyday English and (or) by using pictures. The user responds by selecting one or more of the choices provided by the system. At the end of the consultation session, the system displays the most appropriate maintenance strategy along with its life expectancy. PMAS facilitates the decision-making process and could serve as a consultant for field engineers. Key words: expert system, knowledge-based system, pavement maintenance.
Reliability analyses of activated sludge systems in attaining effluent standards
Authors: Sharma Mukesh , Hall W. B. , McBean E. A.
Published: January 2010

A design-point method, or advanced first-order second-moment technique, is used for reliability-based analyses of activated sludge processes in meeting specified effluent standards. Three non-normal random variables, namely flow, influent biochemical oxygen demand (BOD), and influent suspended solids (SS) concentrations, are utilized in evaluating the performance of the activated sludge system. Two types of failure to attain specified effluent standards are considered, namely BOD failure and SS failure. The reliability of activated sludge system is studied with respect to the volume of the aeration tank using design-point method. Key words: reliability analyses, BOD, activated sludge.
Least impact algorithm for resource allocation
Authors: Moselhi Osama , Lorterapong Pasit
Published: January 2010

A new heuristic-based resource-scheduling algorithm called the least impact model is developed. Unlike available heuristic models, the least impact model allocates resources to a set or a group of activities simultaneously rather than sequentially to individual activities, so as to minimize the negative impact on the remaining total float calculated from a project CPM-type network. A new parameter called future float is introduced as an indicator for assigning scheduling priorities to the sets of activities being considered. Activity sets are generated by first considering all possible combinations of current activities experiencing resource conflict and then narrowing them down to those feasible, which in turn are assigned priorities for allocation of resources based on the least negative impact on the duration of the project. Two examples are worked out to illustrate the use and capabilities of the present model. The results indicate that the least impact model is capable of producing better solutions than those generated from the commonly used total float and the recently proposed current float techniques. Key words: planning and scheduling, resource allocation, resource-constraints scheduling, heuristic scheduling.
Modelling the behaviour of oil spills in natural waters
Authors: Luk G. K. , Kuan H. F.
Published: January 2010

This paper is a state-of-the-art review of the formulations for the different processes responsible for the transport and mixing of petroleum oil spilled in natural waters. Processes accounting for the transfer and loss of the surface oil, such as initial spreading, evaporation, dissolution, emulsification, dispersion, photo-oxidation, and sedimentation, are included. Based on the findings, a dynamic mathematical model describing the fate of spilled oil was developed. To reflect field observations, the surface oil composition in the model is allowed to vary with time as a result of weathering. Initial results for model testing are presented. Key words: oil spill, mathematical model, fate model, weathering processes.
Simulation modelling for the sizing of solid waste receiving facilities
Authors: Arey M. Jimi , Baetz Brian W.
Published: January 2010

Solid waste receiving facilities such as recycling centres, transfer stations, incinerators, and landfills may experience significant traffic congestion and waste storage buildup problems due to the random arrival patterns of waste delivery vehicles. The provision of an increased number of service channels and increased waste storage area will reduce the congestion and buildup problems and the associated costs, but will also incur increased capital and operating costs. A simulation modelling approach for evaluating system performance is described in this paper, and the modelling approach is applied to representative Canadian waste receiving facilities. A minimum cost approach is implemented to determine the preferred number of service channels for one application example. The sizing methodology developed should be useful to waste management engineers and planners for both the design of planned solid waste receiving facilities and the operational analysis of existing facilities for a range of projected conditions. Key words: waste management, facility sizing, simulation modelling.
A knowledge-based framework for construction methods selection
Authors: Russell Alan D. , Al-Hammad Ibrahim
Published: January 2010

This paper describes the ingredients of a knowledge-based framework for selection of construction methods. They include an operational definition of construction method, a conceptual model of the decision-making process, an explanation of how project context and construction methods may be represented for methods selection and analysis purposes, the range of criteria that need to be considered, and a representation of construction expertise. These ingredients are illustrated using a prototype expert system, called CMSA (Construction Methods Selection Assistant), to select a shoring system for cut-and-cover tunnelling. Key words: construction methods, decision-making, expert system, prototype.
Frost damage to clay brick in a loadbearing masonry building
Authors: Maurenbrecher A. H. P. , Suter G. T.
Published: January 2010

Frost damage in the exterior, loadbearing, clay brick walls of two 5-storey apartment buildings could have seriously affected their loadbearing capacity if left unchecked. A coating applied to the exterior had not stopped further damage from occurring. This paper describes the work to determine the cause of the damage. The work included a condition survey, tests on the brick, and monitoring temperature and moisture levels in a section of the wall. Bricks on an easterly exposure suffered the most damage. The cause was traced to poor quality bricks combined with water infiltration mainly from rain. Remedial measures included cladding the exterior of the brickwork with an insulated siding and replacing severely damaged bricks. Key words: building, masonry, loadbearing, frost resistance, clay brick, moisture, exterior insulation.
Dynamic response of bridges under travelling loads
Authors: Humar J. L. , Kashif A. M.
Published: January 2010

In spite of a number of analytical and experimental investigations on the dynamic response of bridges to moving vehicle loads, the controlling parameters that govern the response have not been clearly identified. This has, in turn, inhibited the development of rational design procedures. Based on an analytical investigation of the response of a simplified beam model traversed by a moving mass, the present study identifies the governing parameters. The results clearly show why attempts to correlate the response to a single parameter, either the span length or the fundamental frequency, are unsuccessful. Simple design procedures are developed based on relationships between the speed ratio, the weight ratio, and the dynamic amplification factors; and a set of design curves are provided. Key words: dynamic response of bridges, vehicle–bridge interaction, moving force model, moving sprung mass model, dynamic amplification factor.
Structural characteristics of wood composite I-beams
Authors: Clinch Robert W.
Published: January 2010

In this study, wood composite I-beams consisting of F11 slash pine flanges and either hardboard or particleboard webs were fabricated and evaluated for flexural stiffness. Prior to fabrication, both the web and flange materials were evaluated for flexural stiffness. The mean modulus of elasticity of the flange material was 16 900 MPa, while that for the particleboard and hardboard was 4250 and 4450 MPa respectively. The mean effective modulus of elasticity for the particleboard-webbed beams was 16 300 MPa and for the hardboard-webbed beams was 16 400 MPa. The implications of the findings are discussed. Key words: wood composites, I-beams, characterization.
Selection of design flood frequencies for hydraulic structures
Authors: Smith C. D.
Published: January 2010

The first step required in the design sequence for a hydraulic structure is selection of the design discharge. The size and cost of the structure will be directly related to the magnitude of this value. If the selected discharge is too large, the structure will be uneconomic; if it is too small, it will be unsafe. The optimum design corresponds to the point where the cost of the structure and the cost of exceeding the design discharge is a minimum. Ideally, the optimizing process should be carried out for each structure. For practical reasons it is not always possible to do this. In such cases, design flood frequencies are used which have apparently been satisfactory for similar structures in the past. Some typical flood frequency values for various structures are given in this paper, along with the rationale for differences in values for different kinds of structures. Key words: design floods, frequency, economics, hydraulic structures.
Forecasting construction cost escalation
Authors: Blair Andrew N. , Lye Leonard M. , Campbell W. J.
Published: January 2010

Escalation can account for a substantial part of construction costs. Therefore forecasts of the amount of escalation are required for budgetary and bidding purposes. This paper examines methods for forecasting construction escalation using statistical time series methods. Time series of construction cost indices are used as a proxy of construction cost escalation. The application of time series methods, their limitations, and their effect on the risk of cost escalation are demonstrated and evaluated. The analytical methods available are only useful in forecasting for short construction projects in stable conditions. This is because none of the methods can forecast escalation caused by unpredictable occurrences such as outbreak of war or certain government action. Construction cost escalation remains a risk to be borne by either the contractor or the owner, or both, depending on the terms of the contract; any logical approach to minimize the risk is worthwhile. Key words: construction cost escalation, cost indices, time series forecasting, exponential smoothing. Box–Jenkins methods, dynamic regression, Statistics Canada.
High cycle (fatigue) resistance of reinforced concrete beams with lap splices
Authors: Rezansoff Telvin , Zacaruk James A. , Afseth Jeffrey G.
Published: January 2010

Full-scale specimens were tested so that lap spliced bottom bars were subjected to cyclic tension loading. The major variable was the degree of transverse confining reinforcement (stirrups) provided along the lap. Lap splices were confined either with the maximum transverse reinforcement deemed to be effective for static loading, permitting the use of shorter lap splice lengths, or with stirrups spaced at approximately one half the effective depth of the beam, requiring the use of a longer lap length. Failure in all specimens with heavier stirrups (shorter laps) occurred with fatiguing of the reinforcing steel, showing fatigue resistances that were comparable with the results for continuous bars tested in flexure. With the lighter (nominal) stirrups, fatigue loading usually produced a splice failure, where the confining concrete split away from the lap in a typical bond failure after fewer load cycles. For comparable bond resistance under static loading, the beams with the heavier stirrup confinement along a shorter lap length were superior under fatigue loading. As previously shown with low cycle, high intensity reversal (seismic) loading, the current study shows that it is prudent to provide a high degree of transverse reinforcing confinement to lap splices that are subjected to fatigue loading. Key words: concrete, reinforcement, lap splices, fatigue, bond, beams, confinement, stirrups, tension.
Seismic response of concentrically braced dual steel frames
Authors: Jain A. K. , Redwood R. G. , Lu Feng
Published: January 2010

Concentrically braced steel frames are one of the most commonly used structural systems because of their structural efficiency, simplicity to analyze and design, and ease of construction and repair. Canadian design codes provide specifications for their design under seismic loading based on the large amount of knowledge related to their seismic response accumulated over the past two decades. This paper examines the impact of a dual system with a moment resisting frame acting in parallel with the concentrically braced frame. Four different frames were designed in accordance with the National Building Code of Canada and CSA-S16.1-M89, and their inelastic responses are studied under the action of both monotonically increasing load and seismic load. The relative strengths and stiffnesses of the frames comprising the dual systems were varied. The ductility demands on members, and overall building deflections and storey drifts, were examined under the action of ten earthquake records. It is concluded that improved performance such as reduced ductility demand and improved uniformity of the distribution of yield throughout the structure can be achieved. However, the stiffness and strength in the moment resisting frame necessary to provide marked improvement must be a significant proportion of those of the braced frame. Key words: structural engineering, earthquakes, inelastic analysis, concentric bracing, dual system, steel, buckling.
Flexural behaviour of concrete beams pretensioned with aramid fibre reinforced plastic tendons
Authors: McKay K. S. , Erki M. A.
Published: January 2010

The durability of reinforced concrete structures has become an increasing concern as our infrastructure ages. In particular is the deterioration of steel reinforcements when used in concrete structures exposed to severe corrosive environments. This paper investigates the feasibility of using noncorroding aramid fibre reinforced plastic (AFRP) tendons as a substitute for steel strand in pretensioned concrete applications. Three AFRP pretensioned beams, 150 × 300 × 2100 mm, were tested under static and cyclic loading. These results indicate that load capacities of the beams were not affected by the cyclic loading. Ultimate strengths were generally greater than predicted, primarily as a result of the ability of the AFRP rods to develop greater tensile stresses than expected. Key words: prestressed concrete, nonmetallic tendons, aramid fibres, advanced composite materials.
Correction of residual strain for coupons that curve on sectioning
Authors: Lu Yue Qing , Kennedy D. J. Laurie
Published: January 2010

When coupons are cut from cross sections to determine the relaxation of residual strains by the method of sectioning, they frequently curve due to variations in the longitudinal residual stresses through the thickness. Relaxation strains measured on the chord will be in error. A method is presented to correct the errors using gauge holes drilled through the specimen to allow strains to be determined on both sides. Key words: correction, coupons, curve, residual, sectioning, strains, stresses.
An innovative lamp-post design of 1916 — a fine example of urban heritage in Ottawa
Authors: Collins John B.
Published: January 2010

In 1916, the Ottawa Improvement Commission, now the National Capital Commission, installed a concrete lamp-post to provide electric lighting along the Federal Driveway as part of its mandate to landscape and maintain parks and parkways in the capital. The design is highly significant both for its innovative use of materials and for its visual impact on the landscape. The lamp-post today is a heritage landmark, representative of urban reform introduced in the early 20th century under the influence of the City Beautiful movement. Key words: City Beautiful; urban design; street lighting; park furniture; Ottawa Improvement Commission; Lincoln Park, Chicago; Prairie School architecture.
A materially nonlinear finite element model for the analysis of curved reinforced concrete box-girder bridges
Authors: Ng S. F. , Cheung M. S. , Zhao J. Q.
Published: January 2010

A layered finite element model with material nonlinearity is developed to trace the nonlinear response of horizontally curved reinforced concrete box-girder bridges. Concrete is treated as an orthotropic nonlinear material and reinforcement is modeled as an elastoplastic strain-hardening material. Due to the fact that the flanges and webs of the structure are much different both in configuration and in the state of stresses, two types of facet shell elements, namely, the triangular generalized conforming element and the rectangular nonconforming element, are adopted to model them separately. A numerical example of a multi-cell box-girder bridge is given and the results are compared favourably with the experimental results previously obtained. Key words: finite element method, curved box-girder bridges, reinforced concrete, nonlinear analysis.
A technique for selecting the Box–Cox transformation in flood frequency analysis
Authors: Lye Leonard M.
Published: January 2010

In hydrology, the Box–Cox power normal transformation has been found to perform well in a number of at-site and regional flood frequency studies. In this paper, an alternative to the maximum likelihood method of finding the Box–Cox transformation parameter, λ, is suggested. The proposed method is based on finding the λ that maximizes the correlation coefficient in the probability plot correlation coefficient test for normality. The proposed method of finding λ was tested on maximum daily discharge data from all over Canada and was found to give almost identical results to that obtained by the method of maximum likelihood. The main advantage of the proposed method is that finding the appropriate transformation and objectively testing whether the transformed data are normally distributed can be done in one step. In other methods, at least two steps are required. In addition, the proposed method makes use of techniques that are familiar to the hydrologist, namely, the probability plot and correlation analysis. Key words: flood frequency analysis, Box–Cox transformation, probability plotting, maximum likelihood method, Blom's plotting position, probability plot correlation coefficient test, correlation analysis, normal distribution.
Spatially varied flow over rockfill embankments
Authors: Kells J. A.
Published: January 2010

A procedure for determining the flow conditions through and over a simple, rockfill embankment having a horizontal top surface is presented. In this situation, the free surface flow regime can be characterized as spatially varied and the seepage flow regime as non-Darcian. Included in the paper are a review of spatially varied flow theory and analysis, a brief description of the numerical method used to conduct the non-Darcy seepage analysis, a few comments with respect to the determination of the flow properties of the model rockfill, and a discussion of the application of the analysis procedure to a model rockfill embankment. Two flow conditions were tested. The one flow condition was for partial overtopping of the embankment, while the other involved complete overtopping. The spatially varied flow analysis was carried out using a spreadsheet, and it included the incorportion of Hinds' method for control point location. A modified version of a Darcian finite element seepage program was used for the seepage analysis. The computed results are compared with those obtained from a physical model. As shown in the paper, the results are generally supportive of the proposed modeling procedure. Key words: control point, non-Darcy seepage, numerical model, physical model, porous media, rockfill, spatially varied flow.
Factored moment resistance of composite bridge girders with singly symmetric non-compact steel sections
Authors: Picard A. , Beaulieu D.
Published: January 2010

According to standards CAN/CSA-S6-88 and OHBDC (1983), a fully plastic stress distribution or a linear stress distribution at first yielding of the steel section should be used to determine the factored bending resistance of a composite section made of a non-compact steel section, depending upon the depth of the compression portion of the web. In this paper, an elastoplastic analysis is presented and is illustrated by an example. Comments on some clauses from the S6 Standard are also presented. Key words: bridges, composite beams, elastoplastic analysis.
Least cost scheduling for repetitive projects
Authors: Moselhi Osama , El-Rayes Khaled
Published: January 2010

Dynamic programming has been utilized to optimize scheduling of repetitive projects. The optimization criterion of existing techniques, however, is limited to minimizing the project duration and does not account for the impact of such optimization on the project cost. While the minimization of the project duration may reduce the project indirect costs, it does not guarantee a minimum total cost for the project. In practice, minimizing the overall cost of a project is frequently regarded to be more important than minimizing its duration. The objective of this paper is to present a flexible model that incorporates cost in the optimization process. In addition, the model is capable of considering the weather impact and the learning curve effect in the optimization process, simulating two important factors affecting productivity on this class of projects. The model utilizes dynamic programming and performs the solution in two stages: first, a forward path to identify local minimum conditions; and then a backward path to ensure a global minimum state. A numerical example from the literature is analyzed in order to demonstrate the use of the model, test its validity, and illustrate the significance of incorporating cost, weather impact, and the learning curve effect in the optimization process. Key words: planning and scheduling, repetitive projects, linear scheduling, cost optimization, dynamic programming, learning curve effect, weather impact.
Buckling of built-up compression members in the plane of the connectors
Authors: Temple Murray C. , Elmahdy Ghada
Published: January 2010

An examination of the requirements for the design of built-up compression members in the North American and European standards and specifications reveals a great variation in the allowable maximum slenderness ratio for an individual main member, and also in the determination of an equivalent slenderness ratio. The requirements of the Canadian standard with regard to the determination of the maximum allowable slenderness ratio of a main member between points of connection can be a bit confusing.This research involved a study of model built-up members that buckled about an axis perpendicular to the plane of the connectors. Twenty-four tests were conducted on model built-up members. The theoretical analysis consisted of a finite element analysis of the model built-up struts. In addition, an equivalent slenderness ratio was calculated by several methods. These equivalent slenderness ratios were then used in conjunction with the requirements of the Canadian standard to calculate a compressive resistance, which was compared with the experimental failure load.From this research on built-up members that buckle about an axis perpendicular to the plane of the connectors it was found that at least two connectors should be used, that the slenderness ratio of the main member between points of connection has a significant effect on the compressive resistance, and that Timoshenko's equivalent slenderness ratio when used in conjunction with the Canadian standard gives results that are in the best agreement with the experimental results. Key words: battens, built-up members, compressive loads, connectors, equivalent slenderness ratio.
Radial spreading of oil under and over broken ice: an experimental study
Authors: Yapa Poojitha D. , Belaskas David P.
Published: January 2010

The mechanism of oil spreading in the presence of solid ice covers had been investigated in several studies. There are good laboratory data and some field data available for the case of solid ice covers. There are, however, little data available on the subject of oil spreading in the presence of broken ice covers. The lack of data and the complexity of dealing with many different types of broken ice covers are the main reasons for the poor understanding of the oil spreading mechanism in broken ice covers. In this paper, a laboratory study is presented to investigate the behaviour of oil spreading when spilled under a broken ice cover. The experiments included different ice cover thicknesses, artificial and real ice, oils of different viscosities, and a variety of discharge and volume conditions.Laboratory observations indicate that the behaviour of oil spilled under a fragmented ice cover depends on the type of ice cover. While oil may penetrate completely through one type of cover, it may not penetrate at all in another type. In covers that allow the oil to penetrate through, initially oil spreads under the ice, with simultaneous migration through the ice cover. When the oil reaches the water surface, it starts to spread rapidly, outpacing the spreading underneath. The spreading of oil under the ice was dominated by the buoyancy and viscous forces, while oil spreading on the water surface near the top of the ice cover was dominated by interfacial and viscous forces. This paper advances the fundamental understanding of the mechanism. The data from this study can be used to develop future mathematical models on this subject. Key words: oil spreading, oil slicks, oil under ice, constant discharge, constant volume, brash ice.
Surveying instrument makers of Central Canada
Authors: Brooks Randall C. , Daniels William J.
Published: January 2010

This paper describes the impetus for the development of a trade in surveying instruments in Central Canada in the 19th and early 20th centuries and compares it with the nautical instrument trade in our developing nation. The careers of several of the known makers are considered and some of the extant instruments made by them are briefly described. The question of the extent that they were makers is also considered. Key words: surveying, instruments, makers, history, Canada, Ontario, Québec, 19th–20th century.
Combined wind and ice loading on antenna towers
Authors: Wahba Yohanna M.F. , Madugula Murty K.S. , Monforton Gerard R.
Published: January 2010

The present study contains an analysis of the recorded and predicted values of ice accretion for the meteorological stations in Canada; also, the value of the wind pressure associated with the maximum ice accretion is studied. The values were compared with those specified in CAN/CSA S37-M86. Changes to the ice map of Canada are proposed based on the climatic data analyzed, and this map is compared with the one specified in the 1991 edition of the Ontario Highway Bridge Design Code. Also, some modifications to the method of calculating radial ice thickness are recommended to include the size of the member. Key words: antenna towers, environmental loads, guyed towers, ice loads, self-supporting towers.
Development of an airborne millimeter-wave FM-CW radar for mapping river ice
Authors: Yankielun Norbert E. , Ferrick Michael G. , Weyrick Patricia B.
Published: January 2010

Analyses of a river's freezeup ice cover stability and its breakup rely on detailed knowledge of the cover's thickness and the variability of that thickness. A high-resolution, millimeter wave (26.5- to 40-GHz) frequency modulated-continuous wave radar with real-time data acquisition and digital signal processing and display capability was deployed from a low-flying (3–10 m) helicopter to continuously acquire, process, and display data during an ice thickness profiling survey of a 24-km study reach. A nominal sheet ice thickness of 50 cm, occasional areas of new ice sheet as thin as 5 cm, open leads, and massive ice accumulations of the order of 5 m thick were encountered. Radar profiling data agreed with ground truth from borehole measurements of the sheet ice, and provided a more detailed view of the ice conditions than that obtained from a low altitude video survey. The radar system provided rapid, safe, and accurate data acquisition, allowing detailed mapping of the ice conditions throughout the reach. Key words: airborne, FM-CW radar, high-resolution radar, ice profiling, millimeter waves, radar remote sensing, river ice.
LONG DURATION ECHOES FROM AURORA, METEORS, AND IONOSPHERIC BACK-SCATTER
Authors: McKinley D. W. R. , Millman Peter M.
Published: January 2010

In the course of the Ottawa meteor program some unusual echoes have been detected on 33 Mc. Echoes from the aurora are discussed and correlated with visual observations. Two mechanisms of radio reflections from the aurora have been proposed but the data here presented are insufficient to favor one over the other. On Aug. 4, 1948, six extremely long duration meteor echoes were observed which may have been due to abnormal ionospheric conditions. From time to time since August, 1948, a weak semipermanent echo has been recorded, usually appearing at a range of about 80 km., and enduring up to an hour. It is suggested that this echo is due to back-scatter from the same sources in the lower E-region that are presumed to be responsible for long-range very high frequency propagation.
AN EXPERIMENTAL STUDY OF A DIVERGENT NUCLEAR REACTOR
Authors: Bayly J. G.
Published: January 2010

Experimental measurements of the relaxation times of a nuclear reactor were compared with the theoretical relaxation times in the range 1.6 to 186 sec. The work was done with the Chalk River Zero Energy Experimental Pile, ZEEP, in 1947, and showed that agreement within the experimental error could be obtained if the theoretical model used to represent the reactor was of the age-velocity type with a correction for the effect of the reflector.
CROSS SECTION FOR THE REACTION Be9(γ, p)Li8
Authors: Haslam R. N. H. , Katz L. , Crosby E. H. , Summers-Gill R. G. , Cameron A. G. W.
Published: January 2010

The reaction Be9(γ, p)Li8has been investigated by detecting the 0.88 sec. Li8 β-activity, by the use of a cycling apparatus which allows intermittent operation of the betatron, counting taking place during the periods of no X-ray yield. The cross section for the reaction has a peak value of 2.72 mbarns at 22.2 Mev., a half-width of 4.7 Mev., and the integrated cross section to 26 Mev. is 0.013 Mev-barns.
THE ULTRAVIOLET ABSORPTION OF SILVER BROMIDE
Authors: Allen J. R.
Published: January 2010

The photoelectric absorption process in solid insulators is discussed and contrasted with that for free atoms and ions. It is suggested that in substances of high dielectric constant the resultant screening of the field of the remaining positive hole due to the polarization of the material results in a reduction of the absorption coefficient at the spectral edge, and produces a maximum at higher energies. This effect is illustrated by a calculation of the ultraviolet absorption coefficient of silver bromide using as a model a bromine ion in a hole in a uniform dielectric. The calculated absorption coefficient is found to rise from the edge to a maximum at a wave length of about 850 Å.
THE PHOTONEUTRON CROSS SECTIONS OF Rb87, Zr90, AND Mo92
Authors: Katz L. , Baker R. G. , Montalbetti R.
Published: January 2010

The photoneutron cross sections of the 50-neutron isotopes Rb87, Zr90, and Mo92 have been measured as a function of photon energy. These cross sections exhibit the peaked shape characteristic of photonuclear reactions. Peak values of 0.23, 0.27, and 0.14 barn at 17.5, 18.0, and 18.7 Mev. respectively were found for these nuclei. The widths of all the curves at half maximum were about 6 Mev. In the case of zirconium and molybdenum the cross sections to the isomeric and ground states of the residual nuclei have been determined separately. The ratio of the cross sections, σ ground/σ isomeric, has been examined as a function of photon energy and is discussed in the light of the elementary analysis previously presented.
LA REGRESSION DE L'IMAGE LATENTE DUE AUX PARTICULES CHARGEES
Authors: Demers Par Pierre , Lapalme Jacques , Thouvenin Jacques
Published: January 2010

not available
Ninth Laurits Bjerrum Memorial Lecture: "Small is beautiful"—the stiffness of soils at small strains
Authors: Burland J. B.
Published: January 2010

The purpose of this lecture is to show how field measurements of displacement around foundations and excavations combined with numerical analysis and recent developments in laboratory techniques have together brought about improvements in the understanding of the stiffness properties of a wide range of soils at the low levels of strain often encountered in practice. Key words: excavations, foundations, weak rock, stiff clay, field measurements, strain, yield, laboratory instrumentation, in situ testing.
Physical isomorphism in the mechanical behaviour of soils
Authors: Feda Jaroslav
Published: January 2010

The validity of Buckingham's theorem for a group of soils indicates that the behaviour complies with the condition of physical similitude. Buckingham's dimensionless arguments can be generalized using the conception of dimensionless "criterial" functions, of stress-strain diagram for example; behaviour in harmony with these functions is called physically isomorphous behaviour.By analysing some experimental findings, the author shows that typical for isomorphous behaviour are logarithmic curves (e.g., curve of compression or primary creep) and linear Mohr's envelopes.Two deformation mechanisms are discriminated, that of sliding deformation and that of cataclastic deformation. Only the domination of the first one produces physical isomorphism. Microrheological analysis shows, in a rather qualitative way, that physical isomorphism results from the monotonous strain, stress, and time hardening of the structure of the soils in question. Such structural changes are typical for soft to medium clays and loose sands and for many soils in the range of high pressures. These soils manifest, consequently, physically isomorphous behaviour.The importance of the principle of physical isomorphism is illustrated by its application to creep (Saito–Uezawa relation), to primary consolidation of specimens with varying drainage paths, and to the interpretation of the ratio Ccε/Cαε of compression index to secondary compression index. Key words: model laws, soil structure, compression, creep, shear strength.
Design requirement for ice forces
Authors: Wong T. T. , Sego D. C.
Published: January 2010

The procedure of obtaining design ice loads on arctic structures using the American Petroleum Institute (API) Bulletin 2N is first outlined. Then a summary of ice forces measured in the Beaufort Sea and in the laboratory is given, followed by an examination of the physical principles underlying ice–structure interaction. The current trend of advocating a lower design ice pressure is noted and argued against. It is felt that the indentation formula presented in API Bulletin 2N may be capable of providing a simple, reasonable estimate for the design ice pressure provided a modified definition of strain rate is used. Key words: ice pressure, ice forces, indentation, arctic offshore structures.
Application of electric polarization to contaminant detection in soils
Authors: Yong Raymond N. , Hoppe Edward J.
Published: January 2010

Preliminary experiments indicate the feasibility of constructing for field use a contaminant-detection instrumentation based on dielectric measurements. This study applies the technique of time-domain reflectometry to assess characteristic "signatures" of some selected contaminants and soil–contaminant mixtures. The results imply that a proper differentiation between various signatures can be attained, allowing an assessment in regard to soil–contaminant status. The proposed technique is similar in principle to the induced-polarization method applied in mineral exploration. Key words: electric polarization, contaminant transport, dielectrics, induced polarization, nonpolar liquids, time-domain reflectometry, relaxation, contaminant–soil interaction.
Mechanisms of osmotic flow and volume change in clay soils
Authors: Barbour S. L. , Fredlund D. G.
Published: January 2010

The mechanical behavior of compressible clay soils may be strongly influenced by physicochemical effects when concentrated pore fluids are introduced to the soil. Conceptual models have been used to explain the influence of pore fluid chemistry on the mechanical behavior of clays in a qualitative way. In this paper an alternate macroscopic description of the osmotic volume change behavior of a clay soil undergoing changes in pore fluid chemistry is provided.Theoretical descriptions of two potential mechanisms of osmotic volume change (osmotic consolidation and osmotically induced consolidation) are presented. Osmotic consolidation occurs as a result of a change in the electrostatic repulsive-minus-attractive stresses, R — A, between clay particles. Osmotically induced consolidation occurs because of fluid flow out of the clay in response to osmotic gradients.A numerical simulation is used to demonstrate the characteristic behavior of a clay soil undergoing either of these volume change processes. The results of a laboratory testing program on two clay soils exposed to concentrated NaCl solutions are used to illustrate that the dominant mechanism of osmotic volume change in surficial clay soils is osmotic consolidation. Key words: physicochemical, osmosis, volume change, NaCl salt, montmorillonite, clay, stress state variables, R – A.
Piezocone testing in underconsolidated clay
Authors: Tanaka Yasuo , Sakagami Toshihiko
Published: January 2010

This paper describes the results of piezocone testing that was carried out in underconsolidated soft marine clay in Osaka Bay. The obtained profiles of the tip resistance and the pore-water pressure were quite different from those for clay strata of normally consolidated state. It was apparent that a different approach is needed to interpret the test results for underconsolidated clay. The dissipation tests with the piezocone were performed at different elevations and indicated the excess pore-water pressures remaining in the stratum.The depth profile of excess pore pressure of underconsolidated clay is of special importance to the understanding of the degree of consolidation of the stratum. An effort was made in this paper to assess the excess pore pressures remaining in the clay based on the piezocone data obtained during penetration. An examination was made of available piezocone data of similar marine clays, of both normally consolidated and underconsolidated states. Based on this, a method was proposed for predicting the profile of pore-water pressure in underconsolidated clay using the piezocone data obtained during penetration. Key words: piezocone, field test, underconsolidated clay, excess pore-water pressure, interpretation.
In situ determination of creep properties of sea ice with the pressuremeter
Authors: Murat J. R. , Ladanyi B. , Huneault P.
Published: January 2010

A series of pressuremeter creep and relaxation tests was carried out in the spring of 1987 in a sea-ice cover at Igloolik, Northwest Territories, for the purpose of testing some new procedures for in situ determination of creep properties of sea ice. Compared with a similar field study carried out 9 years earlier, the present investigation included some clear improvements, not only in the instrumentation and data acquisition system but also in the data interpretation and processing. In particular, it is shown that consistent values of creep parameters can be obtained only if proper consideration is made of the amount of stress redistribution taking place before and during each new load application. Key words: in situ testing, pressuremeter, sea ice, creep properties, stress redistribution.
Effects of installation of piezometers and wells on groundwater characteristics and measurements
Authors: Chapuis Robert P. , Sabourin Louis
Published: January 2010

The results of a variable-head permeability test can be used to check whether a piezometer or sampling well has been successfully sealed in the soil and to detect hydraulic short circuits and possible cross-contamination between aquifers. An improper seal is a well-known cause of hydraulic short circuit. In some instances, also, although the tubing has been sealed over its full length, the water level in the pipe is not representative of the actual piezometric head. An example shows that the values of hydraulic conductivity determined using several test methods varied in a 1:6 ratio before detection of a piezometric error. The resulting correction reduced the variation in k to ± 12%. The causes of hydraulic short circuits have been investigated using computer simulations. It has been concluded that large errors recorded in the field are due to internal erosion of natural soils around the casing during drilling operations or development. The hydraulic damage to soils is documented. An analytical solution has been written for a simple case of hydraulic short circuit. Its theoretical predictions confirm the validity of the computer simulation. In light of experience, recommendations are proposed to reduce hydraulic damage, therefore improving the reliability of piezometric measurements and representativeness of groundwater samples. Key words: permeability, field test, piezometer, sealing, drilling, water level.
Centrifuge modelling of heat-generating waste disposal
Authors: Poorooshasb F. , James R. G.
Published: January 2010

A set of experiments, conducted on the Cambridge geotechnical centrifuge and which model the free-fall option for the subseabed disposal of heat-generating waste, is reported. The results reported relate to the morphological effects of model penetration (depth of penetration, deformation patterns, and closure) as well as to the pore pressure changes associated with this penetration. Results regarding the effect of heat emission (from the model penetrators) upon the surrounding soil are also presented. These results are discussed and compared with theoretical analyses and field tests, and conclusions are presented regarding both the processes attendant upon penetration and heating and the relevance of the modelling to the prototype event. Key words: centrifuge modelling, heat-generating waste disposal, projectile penetration.
Hibernia geotechnical investigation and site characterization
Authors: Thompson G. R. , Long L. G.
Published: January 2010

A detailed offshore site investigation was conducted in the Hibernia field in 1983 to provide engineering data for the preliminary design of a gravity base structure (GBS) for use as an oil production platform. Reliable information regarding the strength and variability of near-surface soils was needed to verify that the foundation would be capable of resisting large environmental design loads, including those induced by iceberg impacts and storm waves. This paper presents an overview of the geotechnical equipment and methods that were successfully used to complete the investigation, major results of the field and laboratory program, and an interpretation of soil strength parameters needed for analysis of GBS stability under the design loads. Results are presented that confirm that the preshear density and effective confining pressure, or "state," of underlying sand elements are major factors that must be considered when establishing design parameters for GBS structures. It is demonstrated that consideration of state changes resulting from GBS installation is important in the analysis of granular soil resistance under both drained and undrained loading conditions. Failure to account for this effect could lead to an unconservative design. Key words: Hibernia, offshore site investigation, CPT, sand strength, state parameter.
Postfailure analysis: Tramping Lake causeway, Saskatchewan, Canada
Authors: Labossiere J. L. , Sauer E. K. , Christiansen E. A.
Published: January 2010

A traffic causeway placed on the sediments of saline Tramping Lake failed during construction in the summer of 1982. Vertical subsidence has continued until present (1988). The failure mechanism was controlled by sedimentary structure and artesian groundwater conditions. The shear zone is in a soft, near normally consolidated lacustrine sandy silt unit 22 m thick. The lake basin contains lacustrine, deltaic, and fluvial deposits of postglacial origin. Artesian conditions in the Upper Cretaceous Judith River Formation and postglacial fluvial sand and gravel dominate the hydrogeology at the site. The failure took place along a composite slip surface when excess pore-water pressures developed during loading [Formula: see text]. The estimated effective friction angle from triaxial tests and back calculation was 27° assuming c′ = 0. However, a parametric analysis showed that at very high pore-water pressures the effective friction angle required for equilibrium is very sensitive to small variations in ru. The calculated cohesion at [Formula: see text] required for equilibrium was 3.9 kPa, whereas the remolded vane strength measured in the field was 5.0 kPa. Key words: Foundation failure, artesian, saline environment, groundwater discharge, silty clays, postglacial fluvial and lacustrine deposits.
Effect of backfill properties and surface treatment on the capacity of adfreeze pipe piles
Authors: Sego D. C. , Smith L. B.
Published: January 2010

This note presents the results of a limited number of laboratory-scale pile load tests to establish those modifications to current pile construction procedures that would be most effective in increasing pile capacity. The results indicate that the properties of the backfill (ice content, salinity, and size of annulus) have a significant influence on short-term pile capacity, while the properties of the native soil are less important. The results demonstrate that the pile capacity can be maximized through the use of nonsaline sand backfill. In saline soils, the shear strength at the backfill - native soil interface may govern the design, and must be evaluated together with the adfreeze strength at the pile-backfill interface. The results also demonstrate that the roughness of the outside surface of the pile has a significant influence on adfreeze strength. Sandblasting the pile surface doubled the adfreeze strength at the pipe-backfill interface. This effect appears to be due to increased surface roughness rather than to the removal of paint from the pile surface. Key words: adfreeze strength, backfill, permafrost, piles, pile surface treatment, salinity.