摘要:

Optimization studies of an energy production project or complex consist in determining the economic general dimensioning of the works during the prefeasibility or the feasibility stage of the studies. As these first studies are part of the iterative system planning process, they should include very exhaustive sensitivity analyses on the accuracy of all technical and economic parameters, although (and even because) so much data is uncertain during this phase.After a review of the mathematics of discounting and of the decision-making economic criteria, a nomographic approach is presented that allows the optimum dimensions of the project to be determined as a function of any combination of the following parameters: imposed discount rate, total investment cost, variations in cash flow pattern, delay in commissioning date, life expectancy of the works, monetary value of energy and power, system load growth, seasonal pattern of energy demand, effect of secondary energy, long-term average river flow, and effect of regulation on downstream developments.

ISSN:0315-1468    

DOI:10.1139/l86-020

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

As more engineering works are constructed in the upper sections of tidal estuaries in northern regions, it is imperative that engineers become aware of the primary processes related to ice formation, degradation, and breakup in such environments. Since the tidal behaviour can be estimated from astronomical considerations, it is possible to make reasonable estimates concerning the timing and the relative significance of the ice buildup in a particular estuary. A classification system for the ice regime of well-mixed estuaries with a large tidal range is presented. Five distinct zones within the estuary are identified by considering the primary ice-related processes in such estuaries. The worst case for the formation of significant ice accumulations in these estuaries is considered to be that associated with a sequence of freezing temperatures occurring when the difference between the neap tide and the subsequent spring tide is greatest. During this period, significant vertical ice walls can form in a few days. The ice walls that form in the upper portion of the estuaries of the Memramcook River and the Petitcodiac River can reach a height of about 5 m. As the vertical ice walls are formed they significantly reduce the normal trapezoidal cross section, which has side slopes in the order of 1.0V:3.5H, to a rectangular cross section having about the same bottom width.Key words: ice, estuaries, processes, ice walls, classification system, Bay of Fundy, engineering works.

ISSN:0315-1468    

DOI:10.1139/l86-021

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

As a continuation of an ongoing project, measurements of environmental conditions and ice cover responses were made around Adams Island over the winter of 1983/1984. These included current, tide, speed and direction of wind, air temperature, and thickness, temperature, and salinity of the ice. Wind profiles were measured over the ice surface; from these, drag coefficients of 0.001–0.005 were calculated. Horizontal movement rates of the ice cover varied from 20 to 300 mm/day. No direct correlation was found between ice cover movement and the wind and current measurements.In situice pressures measured around the island averaged 250 kPa.Key words: ice pressures, environmental forces, ice behaviour, field instrumentation.

ISSN:0315-1468    

DOI:10.1139/l86-022

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Computer modeling techniques are used for predicting soil losses from overland flow and subsequent suspended sediment yield from large watersheds. The model LAVSED-I (LAVal SEDidentological model No. 1) is based on the universal soil-loss equation of Wischmeier and Smith and the equation of Kiline and Richardson. The model subdivides the watershed into square units varying in size from 0.3 to 3000 km2and the computational procedure is subdivided in four components: precipitation, physical characteristics of watersheds, erosion/sedimentation, and land use. This paper describes the operational development and the application of the model to a prototype-scale watershed. A map for the annual soil loss is presented for the Chaudière watershed (area = 5830 km2). Results of mapping compared with the sediment yield observed are shown in the paper.

ISSN:0315-1468    

DOI:10.1139/l86-023

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The model LAVSED-II (LAVal SEDimentological model number II) has been developed to evaluate the suspended load in northern streams that results from rainfall and snowmelt erosion on upslope areas. The most important parameters are (1) the physical characteristics involved in soil erosion processes and (2) the climatic parameters on a month-to-month basis. Two fundamental relationships are obtained from the governing physical processes and empirical relationships describing snowmelt and sediment transport. The model has been applied to four large watersheds, tributaries of the St. Lawrence River. The computed sediment yield compares very well with the measured suspended load (mostly wash load) in the rivers. The magnitude of the peak during spring is particularly well predicted. The computed sediment yield is shown to be very sensitive to meteorological data. In the case of ungaged watersheds, the model can be applied to estimate the sediment yield.

ISSN:0315-1468    

DOI:10.1139/l86-024

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

This paper deals with the bearing capacity of sea ice covers taking into consideration the nonhomogeneity of the material, which is primarily due to variations in temperature and salinity across the thickness. The study is limited to the evaluation of short-term loads that would cause cracking in the ice cover. The general method for evaluation of such loads is fully developed and simplified formulae are proposed for a given surface temperature and ice thickness.Key words: bearing capacity, sea ice.

ISSN:0315-1468    

DOI:10.1139/l86-025

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The strength of wood falls with time under load, and in current design codes the short-term strength of wood is reduced by about 40% to account for duration of load effects. This figure is based on tests made on small bending specimens. In this paper are described tests made on wooden torque tubes to investigate the effect of duration of load on shear strength. A control sample was tested to establish a curve for short-term strength, and four groups of 80 specimens each were then tested under various levels of constant long-term load. Stress ratio at failure was estimated by assuming that the short-term strength of each group could be represented by the control curve, and that under long-term loading specimens would fail in the order of their short-term strength. In each group the stress ratio at failure fell with time under load, and this reduction appears to be related to that predicted by a viscoelastic plastic model. It is concluded that the Madison curve presently used to predict duration of load effects may be conservative at normal levels of applied stress.Key words: wood, shear, long-term loading, duration of load.

ISSN:0315-1468    

DOI:10.1139/l86-026

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The proposed model calculates the concentrations of dissolved solids in rivers at any point within a watershed, using the components of a conceptual hydrological model (CEQUEAU). For this purpose, the watershed is divided grid-wise into parcels for each of which a daily mass balance is computed. This mass balance takes into account the dissolved solids loads associated with the three inflows considered by the hydrological model, namely surface runoff, interflow, and base flow, as well as the loads associated with municipal and industrial point sources. The model has been applied to the Sainte-Anne River, Québec (total watershed area: 2700 km2) and the calculated values show satisfactory agreement with the observed concentrations at two sampling points (Chute Panet: 1550 km2watershed area; La Pérade: 2700 km2watershed area).Key words: modelling, river, dissolved solids, runoff, interflow, base flow.

ISSN:0315-1468    

DOI:10.1139/l86-027

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

This paper discusses within the context of the Grand River system operation the application of the three performance criteria introduced earlier by T. Hashimoto, D. P. Loucks, and J. R. Stedinger. These criteria evaluate the performance characteristic in respect to system failure, system recovery, and system vulnerability with regard to extreme (costly) failures for alternative operational policies. System robustness, also discussed by Hashimoto and co-workers, is used to measure the economic flexibility of system operation to adapt to uncertainties of future demand. The primary objective of the presentation made herein is to establish the role of these criteria in a decision-making process in the operation of the system.

ISSN:0315-1468    

DOI:10.1139/l86-028

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The research reported here is a continuation of work reported earlier in which it was concluded that the use of expansive cement concrete increased the side resistance of drilled shafts (bored piles) in stiff clay by as much as 50% over that in normal concrete shafts and reduced the settlement by about 50%. The conclusions were based on tests conducted at a concrete age of about 2 months. A year and a half later, the three shafts (one made with normal concrete and two made with expansive concrete) were tested again and the same comparatively better behavior of expansive concrete shafts was observed. The base capacities of all the shafts increased over this period owing to the consolidation of soil caused by residual base stresses following the initial tests. The shafts were later extracted for visual observation and coring. The compression tests on concrete cores obtained from various depths along the shafts indicated that expansive concrete behaves as a sound structural material in the long term. The gains in strength and stiffness of expansive concrete over normal concrete over a period of 2 years were found to be significant.Key words: base bearing capacity, bored pile, cement (expansive), concrete (structural), drilled shaft, expansion, frictional capacity, long-term behavior, settlement.

ISSN:0315-1468    

DOI:10.1139/l86-029

出版商:NRC Research Press    

年代:1986

数据来源: NRC