摘要:

This paper offers a brief and incomplete retrospective of the last 25 years of research on clays in Canada, and especially on the sensitive clays. The implication of this research on the improvement of our knowledge of the behaviour of clays in general is emphasized. The development of special techniques for the study of sensitive clays, such as sampling, and the application of limit and critical states concepts to natural clays have contributed greatly to the important leap forward in our understanding of the soil masses and in the solution of practical problems: the problems of stability, of compressibility, and of consolidation are discussed. Finally, the prominent role of theCanadian Geotechnical Journalin the diffusion and even in the orientation of research in Canada is emphasized.Key words: research, clays, sensitive clays, limit state, critical state, brittleness, sampling, strength, stability, consolidation.

ISSN:0008-3674    

DOI:10.1139/t88-047

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Undrained triaxial compression tests were carried out on reconstituted and nominally undisturbed tubed samples of a lodgement till from the Vale of St. Albans in Hertfordshire, England. The soil is a matrix-dominant, chalky boulder clay of Anglian age with little discernable engineering fabric. Electron microscope observations showed the presence of crystalline calcite in tube samples.The test results were examined within the general framework of critical state soil mechanics using normalizing procedures to take account of the different states and stress histories of the samples. These analyses demonstrate the practical importance of accounting for the current state and stress history in the interpretation of soil test data.The present results form a self-consistent pattern of behaviour. Differences between reconstituted and tubed samples were found only at small strain and may be attributed to cementing in tubed samples, which is broken down during reconstitution and during relatively large straining in recompression and shearing.Key words: boulder clay, cemented soil, critical state, shear strength, soil mechanics, stiffness, till, triaxial test.

ISSN:0008-3674    

DOI:10.1139/t88-048

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The representative elementary volume of a statistically homogeneous rock mass is defined as the minimum volume beyond which any submass behaves essentially like the whole rock mass. A simple, but still general, method for the determination of the minimum volume is given on the basis of the crack tensor concept; it is concluded that the size must be at least three times larger than a typical length of joint traces.Key words: computer simulation, rock hydraulics, site investigation.

ISSN:0008-3674    

DOI:10.1139/t88-049

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Ice-created seabed pits found on the Grand Banks of Newfoundland can be analysed in terms of probable range of soil strength properties and failure mechanisms to determine the ice loads transmitted to the seabed. Almost all pits are less than 3 m deep; their existence can be explained by indentation failures caused by rolling icebergs. About 3.5% of the pits are more than 5 m deep and cannot be explained by iceberg impact. This paper presents a possible mechanism for their formation consisting of two actions: (1) the hard grounding of an iceberg, such that the keel becomes embedded in the seabed, and (2) the passive failure of the soil after the grounding event, predominantly caused by the loads associated with wave forces on the iceberg at the time of grounding or shortly thereafter. A 10 m deep pit located in the Hibernia area is analysed with respect to its configuration and soil parameters. Calculations have shown that, though waves in the Grand Banks area cause forces on the iceberg of a sufficient magnitude to create pits of the order of 10 m deep or more in the stiff Grand Banks soils, the controlling factor of pit depth is the ability of the iceberg keel to deliver these loads to the soil.Key words: iceberg pits, iceberg scour, pit formation, ice–seabed interaction.

ISSN:0008-3674    

DOI:10.1139/t88-050

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Scarborough Bluffs is a 15 km long stretch of the Lake Ontario shoreline east of downtown Toronto. This heavily urbanized area currently represents Canada's most serious erosion problem. The worst affected zone is 1.5 km long and lies along South Marine Drive where 50 m high bluffs are failing by shallow retrogressive failures of jointed glacial clays over underlying deltaic sands and clays. The erosion rate is about four times that for the coastline as a whole.Heavy rains in the Toronto area in August and September 1986 produced a spate of slope failures and mud flows. Particularly heavy storms on September 10 and 29 triggered extensive retrogressive slope failures at South Marine Drive. Hydrochemical investigations of discharge waters suggest that slope failure was caused by surface runoff on the bluff top recharging lower slope areas by infiltration through joints in the upper clay capping. Discharge of water from the lower slope is impeded by less permeable barriers in the deltaic stratigraphy at the site and by a cover of clayey slope debris. Data suggest that provision for adequate drainage of the bluff top, by interceptor drains, is a prerequisite for controlling slope behaviour in the area.Key words: slopes, erosion, groundwater, hydrochemical, recharge, drainage.

ISSN:0008-3674    

DOI:10.1139/t88-051

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Sliding of a moving soil mass along a basal surface is analyzed and viscous-type sliding laws are presented. They relate the relative sliding velocity at the base—or at an interface—to the state of stress at this surface. Examples of practical parameter determination illustrate the suitability of this approach; two landslides (in Switzerland and in France) provide the data for this purpose. A third site (La Frasse, Switzerland) serves as an example of three-dimensional analysis of creeping slopes using the proposed formulation. Comparison of computed and measured velocity distributions shows the method to be promising.Key words: landslides, creep, sliding law, time dependence, interface.

ISSN:0008-3674    

DOI:10.1139/t88-052

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

This paper first provides a brief review of the very limited data available on the size effect on strength of soils. Then it presents the results of an investigation of this effect on the drained strength of two residual soils derived from basalt. The dense basaltic soil, derived from weathering of columnar basalt, is fissured, whereas the vesicular basaltic soil, product of weathering of amygdaloidal basalt, is remarkably free of discontinuities. The results of tests on 500 mm square, 100 mm square, and 63.5 mm diameter direct shear tests, as well as on 36 mm diameter triaxial samples were obtained. The data clearly indicate the significant effect of fissures on the strength of dense basaltic soil, whereas the effect is absent in the vesicular soil. The reduction in strength with size in the former can be attributed almost totally to a loss of the cohesive component of shear strength. In the absence of tests on large-sized samples, a method is suggested to estimate the mass strength of such soils from results of tests on small-sized samples.Key words: fissures, residual soil, size effect, shear, strength, testing.

ISSN:0008-3674    

DOI:10.1139/t88-053

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

X-ray photographs of sample cores are commonly used to describe undisturbed sedimentary structures such as bedding planes, cracks, shells, etc. An improved X-ray film density method is presented; it allows for a quantitative measurement of physical parameters, for example, water content or density, provided adequate calibration and interpretation are used. The influence of the grain size, chemical composition of the materials, and the pore fluid has been investigated. A simple procedure is recommended and illustrated with an example.Key words: radiography, X ray, density, granular materials, film density method.

ISSN:0008-3674    

DOI:10.1139/t88-054

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Multistage direct shear tests have been performed on saturated and unsaturated specimens of a compacted glacial till. A conventional direct shear apparatus was modified in order to use the axis-translation technique for direct shear tests on unsaturated soils. The soil can be subjected to a wide range of matric suctions. The testing procedure and some typical results are presented. Nonlinearity in the failure envelope with respect to matric suction was observed. Suggestions are made as to how best to handle the nonlinearity from a practical engineering standpoint.Key words: shear strength, unsaturated soils, negative pore-water pressures, soil suction, direct shear.

ISSN:0008-3674    

DOI:10.1139/t88-055

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The ultimate lateral resistance and the groundline lateral deflections under working loads of freestanding single model piles and small pile groups, of various materials and different embedded lengths, subjected to horizontal load have been investigated. The test results of piles of various stiffnesses in sand and clay are compared with theoretical analyses based on the concept of an effective embedment depth in terms of the behaviour of equivalent rigid piles.Key words: clay, piles, displacements, lateral load, lateral resistance, pile stiffness, sand, ultimate load.

ISSN:0008-3674    

DOI:10.1139/t88-056

出版商:NRC Research Press    

年代:1988

数据来源: NRC