摘要:

A major experiment - the tunnel sealing experiment, related to the disposal of heat generating radioactive wastes in geological formations and supported by government organizations from Japan, France, U.S.A., and Canada, is being carried out at the Underground Research Laboratory of Atomic Energy of Canada Limited in Manitoba, Canada. Through a systematic process, the results from the experiment will be used to validate numerical models for the early age behaviour of high mass concrete bulkheads. A numerical model, based on the CESAR-LCPC finite element code equipped with the modules TEXO and MEXO, has been developed and used to predict the behaviour of a concrete bulkhead which will be built as part of the experiment. The TEXO-based component of the model which describes temperature changes has been validated. A maximum temperature rise in the concrete of 19°C is calculated. This will occur about 4 days after the concrete is cast. The temperature rise is low. This arises from the use of a specially developed low cement content concrete. Despite uncertainties in the MEXO-based model, which is used to describe the chemo-mechanical behaviour of the system, results indicate that it is unlikely that the concrete will crack, but a gap of 0.5 mm or more will develop between the bulkhead and the rock. Water leakage around the bulkhead through this gap could be significant and measures to seal this gap are advised. The modelling results recorded here will be tested against measurements made in the experiment. Thus, the numerical model will be formally validated and bounds to its use will be defined.Key words: concrete, bulkhead, sealing, early age behaviour, heat of hydration, autogenous shrinkage, underground repository, modelling

ISSN:0315-1468    

DOI:10.1139/l99-055

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

There is a need to rapidly survey plumes of suspended sediment and to determine the quantity and transport of disturbed material that might arise from industrial and remedial activities in lakes and harbours. The example of sand capping of contaminated bottom sediments is used to illustrate the methodology. Capping of contaminated bottom sediments is one strategy for immobilizing contaminants. In a pilot-scale project, a 0.34 m thick cap of clean sand was deposited over a one hectare area in Hamilton Harbour. The objective of this study was to determine if in-place sediments could be disturbed by the capping operation. In the first of three approaches, the suspended sediment plumes created during the capping operation were monitored for evidence of suspension of bottom materials with underwater acoustic and optical profilers and other moored instruments. In-lake calibration of the instrumentation was based on the collection of over 300 grab samples. Three-dimensional rendering of a dense network of acoustic backscatter profiles revealed that there was no evidence that bottom sediment was resuspended. The density current flowing downslope close to the bottom caused by the capping material was examined and found too weak to erode bottom sediments. Finally, a quantitative estimation of the amount of sediment suspended in the plumes indicated little evidence for resuspension of in-place sediments. The methodology developed could also be applied to estimate the concentration and quantities of contaminants in sediments suspended by other remedial activities such as dredging.Key words: suspended sediment plumes, underwater acoustics, optical measurements, sediment remediation, harbours, lakes.

ISSN:0315-1468    

DOI:10.1139/l99-059

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The two-dimensional local scour occurring downstream from a submerged sluice gate for various tailwater depths was studied using a video imaging technique and a laser-Doppler anemometer. The flow field was found to be dynamic (i.e., varied with time). Previously reported equilibrium scour profiles for similar test conditions were not attained even after 96 h of laboratory testing. The scaling laws suggested in the literature were found to be unsuitable. New scaling laws are presented for the condition when a stable equilibrium state has not yet been attained. Velocity profiles are presented at various stations during digging and refilling conditions.Key words: local scour, time scale, video imaging, scour profile, velocity profile, sluice gate, cohesionless material, tailwater effect.

ISSN:0315-1468    

DOI:10.1139/l99-061

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The present article deals with the problem of leaks in drinking water distribution networks. Because of monetary losses related to those leaks, and of the current municipal context, it is important to reduce them to an acceptable level. Several techniques allow efficient elimination of leaks. However, when municipalities wish to set up a program for leak elimination on their networks, these techniques can turn out to be expensive. This research aims at developing a new technique which allows municipal managers to target the most problematic sectors or pipe reaches. Unlike the other techniques, this one is based on the study of pressure drops caused by leaks. This new leak detection approach presents a certain advantage by providing municipalities with a general idea on the leak problem which affects their networks as a whole. The proposed technique allows the identification of sectors or pipes affected with leak problems so that it is possible to identify more precisely which ones request a more extensive auscultation through other existing techniques. The costs related to the use of these techniques might be reduced as a result of an efficient preliminary diagnosis.Key words: pipe, detection, water, leak, infrastructure, tracking, pressure, network.[Journal translation]

ISSN:0315-1468    

DOI:10.1139/l99-075

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Field performance testing of a low-head hydroelectric turbine is essential to evaluate the efficiency and economics of an operation. For low-head hydroelectric turbines, it is difficult to accurately measure the discharge through a unit. Transit-time velocity measurement technology has recently been used to develop, in a laboratory setting, a unique traversing acoustic discharge meter for low-head hydroelectric applications. This technology was recently combined with Gauss-Legendre quadrature integration as an alternative method of measuring the flow through a low-head hydroelectric turbine. However, laboratory testing of this technology has only dealt with undisturbed or ideal flow conditions. Additional physical modeling has been performed to compare the relative accuracy of the continuous traversing acoustic discharge meter with that of a multilevel Gauss-Legendre quadrature integration in disturbed or nonideal flow conditions. The data indicate that while Gauss-Legendre quadrature may provide more accurate estimates in ideal flow conditions, the continuous traversing acoustic discharge meter is better suited to disturbed flow condition because it can better resolve an intricate velocity profile. The accuracy of this instrumentation is sensitive to relatively large scale vorticity rotating in the plane of the acoustic transducers, although accuracies within 2% are still attainable, which is better than the conventional velocity-area method.Key words: acoustic discharge measurement, disturbed flow, turbine, performance testing.

ISSN:0315-1468    

DOI:10.1139/l99-066

出版商:NRC Research Press    

年代:2000

数据来源: NRC