摘要:

A laboratory investigation into the deformation behaviour of a rockfill material undergoing anisotropic compression at different stress ratios is described. The extent to which elastic parameters derived from one-dimensional compression can predict the behaviour of the rockfill at other stress ratios is considered. Stress paths encountered in embankments of cohesionless fill are examined and the relevance of elastic parameters derived from one-dimensional compression tests in analysing the deformations of such embankments is assessed.

ISSN:0008-3674    

DOI:10.1139/t76-023

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Earth slopes are generally designed in an environment characterized by numerous uncertainties, stemming from limited sampling efforts on soil strata with variable soil properties, amplified further by the discrepancy betweenin situand laboratory measured soil strengths. Additional uncertainties are also introduced from various simplifying assumptions and idealizations that are necessary for a practical mathematical analysis of stability.The uncertainties involved in the short-term stability of soil slopes have been evaluated from an extensive literature survey. A procedure for developing design of earth slopes based on a permissible risk is formulated whereby experience, published research results, experimental test data and judgement can be consistently incorporated in the evaluation of uncertainties and reliability of a given design. An example of slope design is presented to illustrate the proposed risk-based design method.

ISSN:0008-3674    

DOI:10.1139/t76-024

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Sustained growth in urban development in southern Ontario has led to an increased activity in tunnelling in rocks. These sedimentary rocks are bedded and anisotropic in behaviour,In situhorizontal stresses considerably higher than the vertical overburden pressure exist in these rock formations. The combination of these two factors, together with the difficulties encountered in recent tunnelling projects, necessitates a reappraisal of current design concepts.Theoretical studies show that, because of these two factors, high stress concentration occurs at the crown and invert, causing failure in the weaker layers of the bedded rocks. In addition, the pattern and sense of movement are reversed when compared to 'normal' conditions ofin situstress state.Field observations made in three tunnels are described. The instability at the roof and floor and the observed pattern of radial displacements are consistent with the approach employed.Some requirements for temporary support under these conditions are outlined. Available field data on the timedependent deformation of these openings are presented and the consequent influence on the choice of permanent lining is discussed.

ISSN:0008-3674    

DOI:10.1139/t76-025

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Large wharf gravity retaining walls are often constructed in areas of Canada where seismic activity of a level that has damaged marine structures in other countries can be anticipated. From a geotechnical viewpoint, much of this damage is related to the liquefaction of sands and silts in foundations or backfills. It is critical that zones of potential liquefaction be detected, and this may require more extensive field and laboratory testing than for static designs. Simplified procedures for evaluating the liquefaction potential of sands and silts are presented, and some guidelines for sensitive clays are discussed. Since hydraulic fill is often used, remedial measures and specifications to avoid liquefaction of backfills are described. These include densification of the soil and provision of materials outside the gradation range that is most susceptible to liquefaction. While tsunamis arrive after the strong shaking, they can be the source of significant damage in areas where they might occur. Conservative earth pressure parameters are given for areas exposed to tsunamis, and these may be employed for initial assessment of potential problems from offshore earthquakes. The various geotechnical aspects considered must be closely related to other design factors such as seismic exposure, earth pressures, and allowable short-term safety factors.

ISSN:0008-3674    

DOI:10.1139/t76-026

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Geological events dating back to the early Paleozoic (500 million years) have produced marked bedrock conditions in the Montreal area. The geological features are sometimes of importance to the execution and the cost of engineering works.Boreholes provide samples and data on the subsurface conditions, but cannot yield as much information as an open excavation. Detailed surveys of exposed cuts supplement the results of preliminary borings and confirm or modify their conclusions. These could sometimes mean appreciable savings on the construction cost or warnings of foundation designs not suited to actual site conditions. [Traduit par la revue]

ISSN:0008-3674    

DOI:10.1139/t76-027

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The geotechnical map of a region comprises several documents including the map of surficial deposits, depth of overburden, natural slopes and hazards, bedrock contours and geology, synthesis and land use. The land use map reproduces the other documents and shows the areas appropriate for development as a function of the soil bearing capacity, ground and slope stability, ease of excavation, etc.The maps are prepared from available information such as reports, maps, and field data obtained from borings, penetration and vane tests, and geophysical surveys. [Journal translation]

ISSN:0008-3674    

DOI:10.1139/t76-028

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Volume change constitutive relations for unsaturated soils are proposed from a semi-empirical standpoint. One equation describes the deformation of the soil structure and a second equation defines the volume of water present in the element. Each equation can be viewed as a three-dimensional surface with two independent stress state variables forming the abscissas.Uniqueness is tested by measuring volume changes resulting from stress changes in two orthogonal directions and comparing predicted and measured volume changes resulting from a stress change in a third direction. Samples of undisturbed Regina Clay and compacted kaolin showed good agreement between the predicted and measured volume changes for monotonic deformation of the soil structure. The agreement was not as close for the water phase. The variation was attributed to difficulties in measuring water volume changes over a long period of time. The laboratory results indicate that the proposed constitutive equations are of the appropriate form for use in engineering practice.

ISSN:0008-3674    

DOI:10.1139/t76-029

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

It is common for the rate of seepage through a tailings embankment to be estimated on the basis of a conventional flow net analysis assuming steady seepage conditions. Moreover an impervious seal is generally recommended against the upstream face of the dam to minimize seepage flow through the sand embankment. This study shows that, due to rapid rates of placing, slimes can exist in an under-consolidated state. Field measurements are cited in support of the theory and the implications of under-consolidated slimes in the pond are discussed in detail. Procedures to analyse the utility of an upstream seal are also discussed and design examples reflecting actual operating conditions are given.

ISSN:0008-3674    

DOI:10.1139/t76-030

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The sedimentation behaviour of thick dispersions of mineral grains and water, a process that can be called hindered settling, is of some interest in geotechnical practice. This study draws attention to the existence of the phenomenon, investigates the laws governing the settling behaviour of dispersions and provides experimental verification of the theory.

ISSN:0008-3674    

DOI:10.1139/t76-031

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The strain increment resulting from an increment of stress applied to a particulate medium has been expressed in terms of its elastic and plastic components. The concepts of strain-hardening plasticity have been employed to develop an incremental stress–strain relation, based on a non-associated flow rule. The parameters appearing in the relation have been found using results of three-dimensional shear tests on sands and glass-microspheres. It is suggested that relations of the type developed in the paper could be beneficially incorporated into a finite-element program.

ISSN:0008-3674    

DOI:10.1139/t76-032

出版商:NRC Research Press    

年代:1976

数据来源: NRC