摘要:

The analysis of frost-heave data on several soils confirmed that segregation potential, hence frost susceptibility, of saturated soils was best related to the average size of the fines fraction, the specific surface area of the fines fraction, and the ratio of the material's water content to its liquid limit. The influence of overburden pressure can also be accounted for by an empirical relationship between the segregation potential, the average size of the fines fraction, and the compressibility index of the soil. The segregation potential was also proportional to the relative fines content in soils where the fines do not completely fill the voids of the coarser fraction. This study led to the development of a new frost-susceptibility assessment methodology based on simple geotechnical routine soil index testing that was validated on a highway site on frost-susceptible subgrade till.Key words: frost heave, index properties, criteria, soil, segregation potential.

ISSN:0008-3674    

DOI:10.1139/t99-008

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Improvement of the shear strength of soft clayey soils around steel pipe piles using high-voltage electrokinetics is investigated in the present study. The experimental setup of a large-scale testing facility is described. Four model piles were installed in two identical cylinders filled with simulated marine sediment. Five electrically insulated electrodes were installed close to the piles to apply a high-voltage electric field in the test cylinder. Negative direct current voltages of -20, -30, and -10 kV were applied in three phases, respectively, for 33 days in the treatment cylinder. Axial compression and pullout pile load tests were performed and the results were compared for both cylinders after each phase of treatment. The pile response is presented in terms of the experimental load deflection curves. It is observed that the axial capacity was increased 30, 29, and 8% after the first, second, and third treatment phases, respectively. The pullout capacity was increased due to the treatment by 11, 23, and 12% after the first, second, and third treatment phases, respectively. Further development of this technique may provide potential solutions for the improvement of soft marine clays, and ultimately it could be applied in the field to rehabilitate existing offshore foundations.Key words: electrokinetics, piles, marine clays, soil improvement, bearing capacity, axial loading.

ISSN:0008-3674    

DOI:10.1139/t99-010

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

The diffusion and adsorption coefficients for benzene were measured for a glaciolacustrine clay using the single- and double-reservoir methods, batch tests, and organic carbon content correlations. Single- and double-reservoir diffusion test cells and experimental procedures were specifically developed for volatile organic chemicals. Analytical methods based on solvent extraction with gas chromatography - flame ionization detection and purge and trap gas chromatography - mass spectrometry were used for the analysis of aqueous benzene solutions in the 0.5 µg/L to 500 mg/L range. The measured effective diffusion coefficient was 0.01 m2/a (3.2 × 10-6cm2/s), and adsorption coefficients ranged from 0.1 to 1.0 mL/g. The diffusion cell tests indicate relatively low levels of retardation for benzene as it moves in clay soils with low organic carbon content.Key words: adsorption, diffusion, benzene, Regina clay

ISSN:0008-3674    

DOI:10.1139/t99-017

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

This paper evaluates and compares two comprehensive cone penetration test (CPT) based methods for evaluating liquefaction resistance of sandy soils. The comparison is made based on the results obtained from artificial neural network (ANN) analyses. Two methods are compared, one by Olsen and his colleagues at the Waterways Experiment Station and one by Robertson and his colleagues at the University of Alberta. ANN models are created to approximate the two CPT-based methods so that they can easily be compared using a large database. The results show that ANN models can approximate both Robertson and Olsen methods well, and that both methods are fairly accurate in predicting liquefaction resistance. The Robertson method has a success rate of 89% in predicting liquefied cases, a success rate of 76% in predicting nonliquefied cases, and an overall success rate of 84%. The success rates for the Olsen method are 68%, 89%, and 77%, respectively, in predicting liquefied cases, nonliquefied cases, and all cases. Both methods are considered accurate in predicting liquefaction resistance of sandy soils. The Robertson method is slightly more accurate than the Olsen method. The issue of the propagation of potential uncertainties in the soil parameters and solution model is also discussed.

ISSN:0008-3674    

DOI:10.1139/t99-011

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

This paper presents a series of numerical simulations for laboratory and field pullout tests. A nonlinear differential expression for interface pullout from simple equilibrium of forces and hyperbolic interface model for shear displacement variation along the length of the planar reinforcement is utilised. Finite difference numerical method and nondimensional expressions are adopted for wider application. The relative stiffness and relative displacement parameters are defined and related to the interface pullout interaction mechanism. A parametric study to develop computer-simulated interface design charts for a practical range of relative stiffness and relative bond resistance is theoretically illustrated. The pullout model is capable of simulating the responses of inextensible as well as highly extensible planar reinforcements. The model responses compared satisfactorily with the available theoretical and experimental pullout test results for steel straps, polymer strips, geotextiles, geomembranes, nylon geosynthetics, and geogrid reinforcements.Key words: geosynthetics, extensible reinforcement, numerical simulation, parametric study, pullout testing, reinforced soil.

ISSN:0008-3674    

DOI:10.1139/t99-006

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Artificial sea ice sheets have been frozen in a centrifuge using novel techniques which yield reproducible ice growth rates and result in ice sheets of uniform thickness. The upper surface of these ice sheets has been subjected to an increasing load applied over a limited area, the maximum sustained load giving the bearing capacity at high inertial acceleration. Such centrifugal modelling techniques produce ice sheets with bearing capacities in agreement with existing field and laboratory data. In particular, the influence of indentor diameter and loading rate is examined and the centrifuge data are found to behave in the same manner as existing data with respect to both of these variables. All data are compared with a number of theoretical descriptions of bearing capacity, and these comparisons are discussed with regard to their impact on the applicability of the centrifuge modelling technique on ice penetration problems.Key words: centrifugal modelling, sea ice, bearing capacity.

ISSN:0008-3674    

DOI:10.1139/t99-014

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Methane gas, found in loose deltaic deposits, can contribute to the triggering of flow liquefaction of submarine slopes. The behavior of loose gassy sand is studied in the laboratory using monotonic consolidated undrained triaxial compression tests. Samples consisted of reconstituted Ottawa sand prepared to degrees of saturation ranging from 80 to 100%. Gas contents were determined using a time domain reflectometry miniprobe with a series of calibrations relating apparent dielectric constant to degree of saturation. The results indicate that loose gassy sands can strain soften and experience flow liquefaction. If the degree of saturation is lower than the "cut-off" value, for a specific void ratio, flow liquefaction will not occur.Key words: triaxial testing, liquefaction, Ottawa sand, gassy, unsaturated.

ISSN:0008-3674    

DOI:10.1139/t99-007

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

A recent microstructural investigation of Osaka Bay clay sediments has revealed the presence of abundant microfossils, particularly in the marine layers, which appear to influence directly the microstructural framework of the sediments and eventually its geotechnical behaviour. The microfossils act as a structural component which provides a high compressibility when most of the interaggregate pore space is closed. In addition, they can introduce some bias on the measurements of physicochemical properties.Key words: microstructure, porosimetry, Atterberg's limits, compressibility, mineralogy, microfossils.

ISSN:0008-3674    

DOI:10.1139/t99-009

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Design charts for seismic pressures against rigid walls subjected to horizontal earthquake shaking are presented for both uniform and nonuniform backfills. Solutions are based on a simplified model of soil response which gives results that agree almost exactly with rigorous solutions. Peak seismic thrusts are presented for three different soil profiles. For each profile, 250 combinations of ground accelerations and distributions of soil shear moduli with depth are analysed to provide data points of peak seismic thrust ratios for the construction of design envelopes. The seismic thrust ratios for design are presented as a function of the ratio of the predominant frequency of the earthquake motion and the fundamental frequency of the wall-soil system. An approximate method is given for evaluating the latter frequency without a full analysis.Key words: rigid walls, seismic lateral pressures, design lateral pressures.

ISSN:0008-3674    

DOI:10.1139/t99-013

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Le ballast et le rail sont les composants majeurs intervenant dans la qualité de l'infrastructure ferroviaire. Or, le comportement du ballast demeure mal connu. Pour identifier une loi de tassement du ballast dans le plan vertical, un essai à échelle un tiers, intitulé « Microballast », est proposé. Pour cela, des lois de similitude décrivent le passage des grandeurs associées au modèle réel à celles du modèle réduit. Elles sont basées sur la conservation du matériau ballast et la conservation des champs de contraintes au sein de l'éprouvette. L'éprouvette de ballast est soumise à un chargement vertical reproduisant la charge appliquée sur le ballast lors du passage d'un bogie de train à grande vitesse (TGV). Les résultats de cet essai servent à établir la loi de tassement du ballast qui relie un incrément de tassement à la déflexion élastique de l'ensemble formé par le ballast et le sol sur lequel il repose. Les paramètres intervenant dans le chargement, la qualité du sol supportant le ballast et l'épaisseur de la couche de ballast sont discutés. Mots clés : voie ferrée, ballast, comportement mécani

ISSN:0008-3674    

DOI:10.1139/t99-004

出版商:NRC Research Press    

年代:1999

数据来源: NRC