摘要:

This paper describes a technique for determining the diffusion coefficient and the distribution coefficient for contaminants using saturated, intact (undisturbed) clayey soil samples. The technique is illustrated with reference to a number of laboratory tests involving advective-diffusive migration of potential contaminants through an intact clayey soil from Sarnia, Ontario. An important aspect of the proposed technique is that the mass of contaminant in the system is kept constant and so significant decrease in source leachate concentration occurs during each test. A simple theoretical model is used to analyze this case and it is shown that this phenomenon can be used to deduce both the diffusion coefficient and the distribution/partitioning coefficient from a single test. Parameters are deduced for a number of salt solutions passing through the clay from the Sarnia area. On the basis of these tests it is suggested that for the Sarnia soil and advective velocities up to the maximum examined (0.035 m/a), mechanical dispersion does not measurably affect the magnitude of the "coefficient of hydrodynamic dispersion" (i.e., there is no significant dispersion). It is also suggested that the effective porosity corresponds to that deduced from the water content of the soil.Key words: contaminant migration, soil, laboratory study, experimental, analysis, diffusion, advection, clays, groundwater.

ISSN:0008-3674    

DOI:10.1139/t88-011

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

A finite element (FE) analysis of the field test excavation in Welland Clay is performed using an anisotropic soil behavior model. This paper describes the model, FE formulation, and transient effective stress stability analysis, and compares FE results with the field measurements. The analysis reflects the postexcavation decrease in the factor of safety with time and predicts the failure of the slope along the observed failure surface. The parametric study shows that the time to failure is a function of the pore pressure boundary conditions at the excavation surface and affects the transient factor of safety.Key words: constitutive relations, excavations, finite element, plasticity models, pore pressure, soil anisotropy, stability.

ISSN:0008-3674    

DOI:10.1139/t88-012

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The implications for seismic design in Canada, of the acceleration data recorded at a number of sites in Mexico City during the September 19, 1985, earthquake, were investigated. The conditions for amplification of low-level incoming ground motions at deep sites were identified, in particular, the critical role of variation in shear modulus with shear strain. The current procedure for determining site-specific ground motions was evaluated and major sources of uncertainty in the results were identified. Criteria for selecting representative input motions for site response studies are recommended based on results of analyses of Mexico City sites. A comparative study of sites in the Fraser Delta area of British Columbia showed that offshore subduction earthquakes should be considered when developing design spectra for deep sites in the delta.Key words: earthquakes, seismic design, ground motions, shear modulus, design spectra.

ISSN:0008-3674    

DOI:10.1139/t88-013

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

A nine-storey structure was recently constructed on a raft founded on a 30 m thick layer of clayey silt at Fredericton, New Brunswick. Detailed soil investigations included conventional borings and self-boring pressuremeter, field vane, and flat dilatometer tests performed at the site. In addition to the field testing, undisturbed samples were obtained and tested in the laboratory to determine the compressibility and shear strength characteristics. To compare the performance of the foundation with the design assumptions, instrumentation consisting of piezometers, contact pressure load cells, and settlement points was installed. The instrumentation was monitored at regular intervals during the construction stage and at 6 month intervals following the completion of the building. This report presents (i) the results of the field and laboratory testing, (ii) the results of the field monitoring, and (iii) the results of a finite element computer analysis of the foundation-soil interaction.Key words: raft foundation, instrumentation, clayey silt, compressibility, soil tests, soil–structure interaction.

ISSN:0008-3674    

DOI:10.1139/t88-014

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The field vane (FV) has traditionally been utilized to obtain profiles of undrained shear strength in soft to medium clays. After some 40 years of experience with FV results, it has been suggested that empirical correction factors be applied to the FV data to account for the effects of strain rate, anisotropy, and disturbance on measured shear strengths. As an additional use of the device, the FV may be calibrated at each site to develop profiles of overconsolidation ratio (OCR) with depth. A data base of oedometer test results and FV strengths from 96 different clays has been compiled to use as a basis for this calibration.Key words: field vane, undrained strength, clay, overconsolidation ratio, preconsolidation pressure, shear strength, vane shear.

ISSN:0008-3674    

DOI:10.1139/t88-015

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The effect of interface roughness in problems of soil–structure interaction is demonstrated using a simple finite element interface model. Three examples of geotechnical interest are presented to demonstrate the approach, and comparisons are made with closed-form solutions where available. Both rough and smooth extremes of interface behaviour are analysed. The smooth interface modelling is performed without the use of specialized elements, and involves uncoupling and rotation of freedoms parallel to the proposed interface direction. It is suggested that, in view of the uncertainties often associated with interface properties, a rational approach for engineering purposes is to obtain solutions for the perfectly rough and perfectly smooth cases leading to upper and lower bounds on the full range of interface behaviour.Key words: finite elements, interfaces, soil–structure interaction, foundations, lateral loads, culverts, piles.

ISSN:0008-3674    

DOI:10.1139/t88-016

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The objective of this paper is to present a numerical analysis by finite elements of a two-dimensional nonlinear mathematical model for heat conduction with phase change in a thawing embankment in permafrost. The calculated results are compared with actual measured data, and good agreement is obtained. All calculations were carried out on a personal computer.Key words: permafrost, thawing, embankment, temperature field, numerical analysis.

ISSN:0008-3674    

DOI:10.1139/t88-017

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Well-graded tills are a common surficial material over much of the Canadian Arctic from northern Manitoba to Somerset Island. The compactibility and bearing strength of these tills when thawed appear to be controlled by groundwater flow in the active layer. Water seeping from bedrock outcrops flanked by till enters the till active layer and flows via macropores formed as ice lenses thaw. This flow appears to retard consolidation of the till. Slopes having no seepage source consolidate more rapidly. This seepage maintains the till in a state highly susceptible to liquefaction and would yield material with a moisture–density condition unsuitable for construction use.Key words: till, surficial, compactibility, bearing capacity, groundwater, seepage, freeze–thaw, liquefaction.

ISSN:0008-3674    

DOI:10.1139/t88-018

出版商:NRC Research Press    

年代:1988

数据来源: NRC

ISSN:0008-3674    

DOI:10.1139/t88-019

出版商:NRC Research Press    

年代:1988

数据来源: NRC

ISSN:0008-3674    

DOI:10.1139/t88-020

出版商:NRC Research Press    

年代:1988

数据来源: NRC