摘要:

The Canadian Standards Association standard S471 "General requirements, design criteria, environment, and loads, Part 1 of the CSA code for the design, construction and installation of fixed offshore structures" contains an appendix "Wave and current loads." To compliment this appendix, the present paper provides a more detailed survey of this topic with a review of the recent literature and recommendations of hydrodynamic data needed in offshore design. In addition, hydrodynamic considerations in the calculation of earthquake and ice loads are mentioned.Key words: currents, current forces, hydrodynamics, ocean engineering, offshore structures, waves, wave forces.

ISSN:0315-1468    

DOI:10.1139/l88-125

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Laboratory studies were conducted to develop a model for the overall decay of total residual chlorine (TRC) under various conditions in the natural streams. This model assumes that a portion of the initial chlorine concentration is used to satisfy the immediate chlorine demand and the remainder is subject to gradual decay.The important parameters influencing the gradual decay of TRC, after mixing in the rivers, were found to be photolysis, evaporation, free radical oxidation, temperature, and turbulence. The decay rate is catalyzed by ultraviolet light and increases significantly as the ratio of area to volume of the container increases. The average level of turbulence in streams is found to approximately double the decay rate obtained under quiescent conditions.Key words: residual chlorine, natural streams, decay, evaporation, photolysis, turbulence, temperature effect, municipal effluents.

ISSN:0315-1468    

DOI:10.1139/l88-126

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The containment of brine in shallow ponds is one of the most serious problems facing waste-management engineers today. Brine waste is produced in many mining and processing operations. It is characterized by high salt concentrations which may seriously contaminate groundwater if not successfully contained. However, brine reacts chemically with clays used in liner construction. As brine permeates the liner, physicochemical interactions between the clay and brine lead to a reduction in volume of the liner. This shrinkage may cause cracking of the liner and the creation of a highly fractured permeable macrostructure.Numerous techniques have been tried to find an effective and economical method of containing brine. Some of these techniques have involved the use of soil, concrete, asphalt, and synthetic liners. However, all of these techniques have major deficiencies in either cost or effectiveness. This paper presents a case study of the first attempt to solve the volume change problem by designing and constructing a sand–bentonite liner prehydrated with brine. The design was based on the results of a triaxial permeability testing program. The results of the testing program and monitoring of the liner since construction indicate that brine prehydration of sand–bentonite liners is an effective technique for use in brine containment.Key words: bentonite, brine, liner, prehydration, containment, waste management, physicochemical effects, clays.

ISSN:0315-1468    

DOI:10.1139/l88-127

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Because no analytical solution exists for transient mixing of contaminants in the transverse mixing zone of streams, numerical solutions must be used in pertinent engineering applications. Few numerical algorithms have been devehloped for this problem and the relatively simple explicit ones are subject to serious numerical "diffusion." It is suggested herein that such effects can be minimized using an irregular space grid such that the length of each element is exactly equal to the time step times the local flow velocity. Using also the well-known streamtube concept, a simple explicit algorithm is obtained and verified by means of three laboratory and one field test. Two of these tests include concentration data that are both transient and within the transverse mixing zone, which afford a more complete algorithm testing than has been done in the past. Possible improvements for increased accuracy, efficiency, and generalized natural stream application are discussed.Key words: advection, algorithm, channel, diffusion, dispersion, explicit, mixing, numerical, numerical diffusion, river, streamtube, test, transient, transverse.

ISSN:0315-1468    

DOI:10.1139/l88-128

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The results of a study on the effect of edge beam geometry on the static live-load load distribution characteristics of single-span slab and slab-on-girder bridge superstructures are presented. Using a grillage analysis, the influence of various forms of edge stiffening on longitudinal bending moment and vertical deflection at midspan was investigated. Two load cases utilizing the Ontario Highway Bridge Design truck were considered. Of particular interest is the load case of a single vehicle in a travelled lane, as edge beam deflection under this condition is governed by a serviceability limit state design requirement of the Ontario Highway Bridge Design Code.For the bridge geometry and loadings considered, all types of edge stiffening significantly affect edge beam bending moment and deflection at midspan; the effect generally increases as the span decreases. Edge beam bending moment increases as the stiffness of the edge beam is increased. Considering the change in edge beam stiffness, edge beam deflection decreases even though the bending moment carried by the edge beam increases. The results of the grillage analysis agree well with an interpretation of the simplified method of analysis of the Ontario Highway Bridge Design Code. When the deflection criterion is affecting a bridge design, it would be beneficial to account for the edge stiffening.Key words: load distribution, edge stiffening, edge beams, bridge deck analysis, grillage analysis.

ISSN:0315-1468    

DOI:10.1139/l88-129

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Applications of seepage meters in lakes with slight bottom sediments in fractured rock basins have not been reported. A study of the hydrogeology of Long Lake, at Halifax, Nova Scotia, used seepage meters in this situation. Fifteen meters were installed in the 1.7 km2lake — seven in a line extending from the shore, the remaining eight on the lake periphery. Seepage measurements were made monthly over 1 year. Groundwater levels were measured in boreholes in the fractured granite of the watershed. A positive inflow of groundwater to the lake occurred through the year, seepage flux at the shoreline meters varied from 0.15 to 0.78 mL∙m−2∙s−1, with no consistent seasonal variations. Seepage decreased exponentially with offshore distance. A linear relationship was evident between water levels in a borehole near the shore and rate of seepage at the closest meter. Chloride applied to this borehole was reflected in elevated chloride concentrations in seepage collected by the meter.Key words: seepage meter, groundwater – lake system, fractured rock trac

ISSN:0315-1468    

DOI:10.1139/l88-130

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

CASTOR is a major project which involves the development and the integration of the software of a computer aided design for hydro projects. Based on a university–industry collaboration, the project involves a number of specialties such as hydraulics, hydrology, reservoir simulation, site characterization, geotechnical engineering, structures, turbines, and computer science. The integration of all components is presented as an advantage despite the restrictions that it could create. The integration covers the basic philosophy in development strategy, the proposed design methodology for users, the sharing of utilities, and the relations with a central data base. A rigorous quality assurance plan is adapted for each module.Key words: computer aided design, hydro development projects, engineering software.

ISSN:0315-1468    

DOI:10.1139/l88-131

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Many urban beaches on fresh water lakes and rivers face closure during peak summer periods due to dangerous concentrations of fecal coliforms and other waterborne contaminants. One such example is the Lake Erie Metro Park which is located approximately 22 km (14 miles) downriver of Detroit, Michigan, and Windsor, Ontario, at the mouth of the Detroit River.N.K. Becker & Associates Ltd. was retained in 1985 to research and develop a functional design for a swim basin that will be formed by cordoning off an area of the Detroit River with a breakwater. A unique feature of this breakwater is that it is being designed to filter water from the Detroit River to the extent required for safe swimming. When it is constructed in 1988, it will be capable of accommodating approximately 1500 swimmers.Extensive hydraulic model studies were carried out at the universities of Windsor and Michigan to research and develop a functional design for this facility. The methodology used to develop the design concepts for this swim basin as well as the results of the testing program are described in this paper.Key words: fecal coliforms, swim basin, sand filter, breakwater, hydraulic model, beach, circulation, waves, water deficit, precast concrete cylinders.

ISSN:0315-1468    

DOI:10.1139/l88-132

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The design and operating procedure for a newly developed automatic oxygen uptake rate (OUR) measurement apparatus is presented. This unit, with the aid of a microcomputer, is capable of collecting a volume of sample, aerating the sample, measuring the oxygen concentration at preselected times, and calculating the oxygen uptake rate on a routine basis. The OUR unit was evaluated using three different performance testing procedures. These were (1) a calibration and general performance test, (2) a long-term performance test, and (3) a detailed comparative performance test. The results of each of these tests are presented. The value and alternative uses of routine monitoring of OUR are discussed along the possible applications such as detection of toxic compounds entering the plant and adjustment of sludge return rates to match OUR values.Key words: oxygen uptake rate, activated sludge, microcomputer, process control, oxygen consumption.

ISSN:0315-1468    

DOI:10.1139/l88-133

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

A prototype based on lamellar flocculation–settling has been developed to recover microalgae produced during the biological tertiary treatment of waste waters. The system has enabled the recovery of up to 85% of the initial suspension of algae, at a load of 17 L∙m−2∙min−1. This load corresponds to a detention time 80 times shorter than in a settling tank.Key words: lamellar settling, microalgae, flocculation. [Journal translat

ISSN:0315-1468    

DOI:10.1139/l88-134

出版商:NRC Research Press    

年代:1988

数据来源: NRC