摘要:

The derivation of design global ice loads for wide vertical caisson-type arctic exploration structures is presented. Correction factors are applied to global ice-load data measured during ice–structure interactions to create a set of design criteria for two typical exploration structures: circular (100 m diameter) and rectangular (160 × 50 m). Return periods for the proposed deterministic design ice loads for these two structures are then determined for typical ice conditions encountered in the Harrison Bay shear zone area in 20–30 m of water.Key words: exploration structures, global design ice loads, risk, probability of exceedence, return periods.

ISSN:0008-3674    

DOI:10.1139/t90-085

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

One-dimensional constant end plate temperature (step freezing) tests were conducted on a saturated clayey silt at various pore-water salinities to establish the relationship between solute rejection and freezing conditions. The rate of cooling, a parameter that is a function of both frost penetration rate and temperature gradient in the frozen soil near the frost front, is the main factor controlling solute partitioning between the solid (ice) and liquid phases. It was also established that there is a threshold rate of cooling of 3 °C/day above which no solutes are rejected from the ice matrix. For rates of cooling smaller than 0.1 °C/day, which incidentally corresponds to most of the field freezing conditions, more than 90% of the solutes are rejected from the pore ice.Key words: freezing, clayey silt, saline, solute, exclusion, rate of cooling.

ISSN:0008-3674    

DOI:10.1139/t90-086

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

A solution for radial expansion of cylindrical cavities in sandy soils is presented. This solution is based on a rigid–plastic model that is not perfectly plastic and is valid even for large deformations (finite strains). Its application to the pressuremeter test is made by using the principle of similitude between cylindrical cavities together with a numerical–graphical technique for solving Palmer's equation, already published by the author. Two examples are presented. The computations are made by the ANABELA II program. It is found that this solution makes it possible to obtain the curve of the friction angles mobilized at each step of the test deformation. The importance of knowing the volumetric deformations associated with the shear is demonstrated as well as the differences in the curves of the angles of friction that are mobilized when finite or infinitesimal strains are used. Finally, the value of the friction angle mobilized at the critical voids ratio is discussed. An attempt is made to compute its value using the theory presented.Key words: radial expansion, cylindrical cavities, sandy soils, rigid-plastic model, not perfectly plastic model, finite strains, infinitesimal strains, mobilized friction angles, volumetric deformations, friction angle mobilized at critical voids ratio.

ISSN:0008-3674    

DOI:10.1139/t90-087

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

A method for determining the freezing index and the minimum soil temperature at depth is presented. Data are based on published soil records from several weather stations in northern Canada.Key words: ground freezing, permafrost, frost, soil temperatures.

ISSN:0008-3674    

DOI:10.1139/t90-088

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Stress and temperature changes in oil sand masses associated within situoil recovery schemes can give rise to stability and deformation problems. An analytical method is derived to analyze such problems and is incorporated in a finite-element formulation. A step-temperature approach, as used in thermal elasticity, is not appropriate to analyze the temperature-induced effects, unless the time steps are made very small. A better formulation is presented here, which involves introducing additional terms in the stress–strain relation and in the flow-continuity equation, to account for temperature-induced effects. The new approach reduces the fluctuations predicted by the step-temperature approach and leads to more realistic results. The finite-element formulation involves nonlinear variations of stress–strain response, compressibility, and flow and is performed in an incremental manner. The developed formulation has been verified by comparing the finite-element program results with both closed-form solutions and laboratory data. The program has been applied to predict the responses associated with an oil recovery scheme. Such analyses are important in the rational design of oil recovery schemes in oil sands.Key words: oil sand, thermal consolidation, thermal analysis, nonlinearity, finite element, oil recovery scheme.

ISSN:0008-3674    

DOI:10.1139/t90-089

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Several theories have been proposed to correlate the permeability (hydraulic conductivity) with the pore-size distribution of soils, and it seemed interesting to determine if these theories could be applied to natural clays. For this purpose permeability and mercury-intrusion porosimetry tests were performed on a Champlain Sea clay for both intact and remoulded conditions after compression of the specimens to strains varying from 0 to 42%. The results show that for either intact or remoulded soil conditions, there is a relationship between the pore-size parameters and the permeability of the clay. However, there is no unique relationship for both intact and remoulded clays and for the silt and clay considered in previous studies. Consequently, mercury-intrusion porosimetry alone cannot be used to evaluate the permeability of soils in general.Key words: permeability, clays, mercury-intrusion porosimetry, fabric.

ISSN:0008-3674    

DOI:10.1139/t90-090

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The influence of soil organics on the development of soil structure and behaviour of soils is the motivation for this study. Xanthan and dextran, two soil polysaccharides, were examined in relation to their influence on the development of the structure of kaolinite–polysaccharide systems and also on resultant physicochemical properties. The kaolinite–polysaccharide soils were formed in suspensions under anaerobic and low redox potential conditions to simulate environmental conditions that exist in subsurface soils. Information on the rheology of the kaolinite–polysaccharide system, zeta potential, aggregate size, settling properties, and specific surface area were obtained. Both polysaccharides were shown to develop aggregate groups (floes) which participated to a greater or lesser extent in the overall rheological properties of the kaolinite–polysaccharide complexes. The ability of the polysaccharides to develop flocs is seen as a factor to be considered in studies of soil permeability and transport processes in soil. Together with information from infrared spectroscopy and scanning electron microscopy, and in combination with the results obtained from the physicochemical tests, models of interaction between kaolinite and both polysaccharides are proposed.Key words: soil organics, polysaccharides, kaolinite, rheology, floes, xanthan, dextran, soil structure, zeta potential, kaolinite–polysaccharide system, differential viscosity, Bingham yield stress.

ISSN:0008-3674    

DOI:10.1139/t90-091

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Mitigation of the hazards posed by debris flows requires an understanding of the mechanisms leading to their initiation. The objectives of this study were to evaluate and document the hydrologic response of a potential debris-flow source area to major rainstorms and to evaluate whether traditional models of hillslope hydrology can account for the observed response. A field site in an area of previous debris-flow activity was instrumented and monitored for two winter seasons. Hydrologic responses for a wide variety of antecedent conditions were recorded, including two storm events that produced well-defined positive pore-pressure pulses at the site and initiated numerous debris flows in the immediate vicinity of the site. The observed hydrologic response was highly dependent on antecedent moisture conditions which can be characterized by soil matric suction measurements. The pressure-head pulses observed had a magnitude of approximately 50 cm of water, were transient, traveled downslope, and exhibited some spatial variability. Traditional models of hillslope hydrology do not fully account for the positive pore-pressure pulses observed high on the hillslope.Key words: debris flow, hillslope hydrology, pore pressure, antecedent moisture, tensiometer, piezometer, field investigation.

ISSN:0008-3674    

DOI:10.1139/t90-092

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Theoretical expressions, in terms of elastic and thermal properties of multiphase soil systems, have been derived for the change in pore fluid pressure under undrained conditions and the change in soil stress under drained conditions. A methodology is proposed for linking these equations to Biot's generalized coupled flow and deformation formulations in a form suitable for finite-element implementation. The thermoconsolidation numerical model developed for this study employs a modified form of the hyperbolic stress-strain relationship that can account for the shear-induced volume change (dilation) effects. The numerical model is verified under drained conditions and then applied to simulate three triaxial experiments that previously had been performed on good-quality Athabasca oil sand samples. The analyzed tests include drained compression at room temperature, drained compression at an elevated temperature, and an undrained heating under anisotropic stress conditions. The numerical simulations were in remarkable agreement with the observed response under drained and undrained conditions, and the results indicated that the dilative effectsplây a crucial rolein satisfactorily modelling the response of oil sands, particularly under undrained conditions. The application of the numerical model in analyzing the laboratory tests provides a means for determining some of the soil parameters that would otherwise be difficult to measure.Key words: finite elements, numerical modelling, undrained heating, drained heating, thermal consolidation, oil sand, stiffness properties, thermal properties.

ISSN:0008-3674    

DOI:10.1139/t90-093

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Stiffness constants and flexibility coefficients of single piles and interaction factors are presented to facilitate the analysis of pile groups subjected to static vertical loads. A continuous transition from friction to end-bearing piles is accounted for. A new type of interaction factor, established from subgroups of five piles, is introduced for end-bearing piles. This interaction factor allows for the stiffening effect of the piles occurring between the two reference piles. This feature improves the accuracy of group analysis for end-bearing piles. Numerical results for axially loaded single piles and pile groups are presented for a wide range of pile and soil parameters. The results are applicable toboth rigid and flexible caps.Key words: piles, pile group, settlement, interaction

ISSN:0008-3674    

DOI:10.1139/t90-094

出版商:NRC Research Press    

年代:1990

数据来源: NRC