摘要:

The slide which occurred at Lodalen, Oslo in 1954 was used to compare the behaviour of soil models tested in a centrifuge with a well-documented prototype event.The paper describes the centrifugal testing of three models prepared from block samples in which an attempt was made to simulate the stress history of the site. The results of these model tests are presented as an analogous prototype by the application of the simple scaling laws, which when compared with the actual prototype were found to present a realistic facsimile of the landslide.

ISSN:0008-3674    

DOI:10.1139/t78-001

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Centrifugal model tests increase total stress levels in small models made of natural or reconstituted soil, and allow direct observation of repeated failures. A novel use of a basket centrifuge is described in which slopes can be tested without end effects. When a series of models at various overconsolidation ratios was tested to failure the error in the safety factor predicted by a total stress analysis increased with the overconsolidation ratio. Other centrifuges are discussed and the advantage of large machines with balanced arms and swinging carriages are explained. Soil material behaviour discussed includes heat transfer and leaching. The paper concludes with a review of the present availability of and prospects for centrifugal model tests.

ISSN:0008-3674    

DOI:10.1139/t78-002

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Empirical and analytical methods for predicting the occurrence of liquefaction of foundation soils during an earthquake are examined and applied to the Fraser Delta area of British Columbia. The area is diked and at present has a population of about 150 000 people who reside mainly in low-rise buildings. Liquefaction of the foundation soils would cause severe damage to buildings, services, highway and railway links, and the dikes.Application of empirical methods based on blow count values indicates that liquefaction of the foundation soils could occur. Application of analytical methods indicates that liquefaction could occur in the event of an earthquake having a maximum ground surface acceleration of 0.12g(the 100 year value).The effects of various remedial measures are examined and it is shown that densification, drainage, and fill loading serve to reduce the tendency for liquefaction to occur. The presence of a low permeability layer close to the surface may cause liquefaction to occur by impeding the drainage.Construction that involves placing large sand fills with adequate drainage through the surficial low permeability layer to support low rise buildings would seem to be the least hazardous for this region.

ISSN:0008-3674    

DOI:10.1139/t78-003

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

A triaxial cell has been modified to permit measurement of volumetric strains during deformation-rate-controlled and stress-controlled triaxial tests on frozen soils. In the system described here, a volume change in the soil sample alters the level of fluid in the triaxial cell. The fluid level can be monitored during the test using a sloping tube volumeter. Theoretical accuracy with this arrangement can exceed 0.1% of the sample volume.

ISSN:0008-3674    

DOI:10.1139/t78-004

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The detailed analysis of the pore pressures generated during construction under the center lines of four test embankments on a soft sensitive clay indicates a significant departure from the classical methods of pore pressure prediction.In the early stages of loading, the clay is overconsolidated and is characterized by a highCv. As a result a significant consolidation occurs even in the very short duration of the construction. Due to this consolidation the vertical effective stresses increase rapidly until they reach the preconsolidation of the clay. At this point the clay becomes normally consolidated, and further loading occurs at constant effective vertical stress.The YLIGHT model of clay behaviour proposed by Tavenas and Leroueil may be used to fully understand this behaviour.In Part II, it will be shown that these findings apply in fact under most embankments and a prediction method will be proposed.

ISSN:0008-3674    

DOI:10.1139/t78-005

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The pore pressures observed under 30 embankments on clays of widely varying geological origin and geographical location are analysed to confirm the validity of the concepts developed from the Saint-Alban case history presented in Part I.It is shown that a significant consolidation does occur in all but one case in the early stages of embankment construction. As a result the vertical effective stress increases rapidly to a value equal toPc. For further loading on the then normally consolidated clay the pore pressure coefficientassumes a value of 1.0.The observed behaviour is interpreted by means of the YLIGHT model of clay behaviour proposed by Tavenas and Leroueil and is shown to apply directly to all clays with an overconsolidation ratio less than 2.5, and with some modifications to heavily overconsolidated clays.The consequences of this behaviour on the analysis of stability and settlements of embankments are presented.

ISSN:0008-3674    

DOI:10.1139/t78-006

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

A survey of Canadian universities and consulting engineering firms was conducted to ascertain the present status of slope stability software usage in Canada. The results indicate that most universities have access to at least one slope stability computer program. However, there is limited usage of computer programs as a teaching tool at the undergraduate or graduate level. In general, the programs are poorly documented and not distributed. Consulting engineering firms indicate that more education on the relationship between the various methods of slices, on available software and its application to practical problems would be beneficial. The most commonly used procedures are the simplified Bishop method for circular failure surfaces and the Morgenstern–Price method for noncircular failure surfaces.Several well-documented slope stability computer programs are available to the geotechnical engineer at the cost of reproduction. The source for obtaining the programs is listed in the paper. Computer programs are available for all the commonly used methods of slices and the features of each program are also summarized in the paper.

ISSN:0008-3674    

DOI:10.1139/t78-007

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The design of foundations in permafrost areas for large structures involves a knowledge of the thermal and mechanical properties of frozen soil. Recent creep data for frozen soils and ice are reviewed and some secondary (steady) creep relationships are established. A design approach for pile foundations in ice-rich permafrost is proposed and compared with available field case histories. The theory is found to provide reasonable predictions of pile settlements under load. It is suggested that the limitation of long-term pile settlements will control the design loadings.The thermal aspects of ventilated pad foundations are discussed and design curves are given for required pad and insulation thickness and ventilation capacity. Case histories indicate that in order to obtain the necessary ventilation capacity, forced air ventilation using electric fans is required for most practical situations.A settlement analysis for spread footings on permafrost is established and influence factors for settlement rate are given. Again it is apparent that allowable footing loads will be controlled by limiting long-term settlements, rather than by consideration of soil shear strength alone. Field data on the creep response of a tunnel in Fairbanks provide good correlation with theoretical predictions.

ISSN:0008-3674    

DOI:10.1139/t78-008

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

A limit equilibrium method of analysis is proposed for the study of progressive failure in slope stability under a long-term condition. Based on effective stresses, the formulation of the method is derived from consideration of force and moment equilibrium within the soil mass above a prospective slip surface. By dividing the soil mass into a number of vertical slices, recognition of local failure can be made. Once local failure takes place, post-peak strength is assumed to be operative. This then initiates a redistribution of interslice forces and leads to some further local failure. Thus realistic available strengths along the slip surface can be evaluated. This permits the definition of a final safety factor, which is expressed in terms of the actual available reserve of strength. The proposed method has been applied to three well documented case records and encouraging results have been obtained. Based on the assumption that post-peak strengths are given by a friction angle equal to the peak value and a zero cohesion, stability charts have been prepared for design purposes.

ISSN:0008-3674    

DOI:10.1139/t78-009

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The chart developed by Janbu, Bjerrum and Kjaernsli for estimating average elastic settlement of embedded foundations is examined to determine whether improvements can be made in the light of modern capabilities for stress analysis. The parameter describing the effect of a finite layer can be evaluated more accurately from recent results such as those of Giroud. The parameter describing the effect of embedment was originally taken precisely from Fox's work, but finite element analyses indicate that Fox's correction substantially overestimates the effect of embedment. A better estimate can be made by using Burland's correction or, more simply, by ignoring the effects of embedment altogether.

ISSN:0008-3674    

DOI:10.1139/t78-010

出版商:NRC Research Press    

年代:1978

数据来源: NRC