摘要:

Large negative skin friction loads were observed on a 160 ft (49 m) steel pipe test pile floating in marine clay. The test pile was driven, open-ended, on the centerline of a 30 ft (9 m) high granular approach fill on the Quebec Autoroute near Berthierville. Since the installation was made in 1966 the fill has settled 21 in. (53 cm), dragging the pile down with it. Negative skin friction acting along the upper surface of the pile was resisted by positive skin friction acting along the lower end as it penetrated the underlying clay. Under these conditions the pile compressed about(2 cm). Analysis of the axial strains indicated that a peak compressive load of 140 t developed at the inflection point between negative and positive skin friction 73 ft (22 m) below the top of the pile. Negative and positive skin friction acting on the upper surface of the pile exceeded thein situshear strength and approached the drained strength of the soil where excess pore water pressures had dissipated. At the lower end where the positive excess pore pressures were high and relative movement between the pile and the soil was large, the positive skin friction approached the remoulded strength as measured with the field vane. Skin friction was increasing, however, as positive escess pore pressures dissipated.This paper shows that skin friction loads are related to the combination of (a)in situhorizontal effective stresses, (b) horizontal stresses due to embankment loads, and (c) horizontal stresses due to differential settlement of the fill.

ISSN:0008-3674    

DOI:10.1139/t72-014

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Geotechnical considerations associated with deep excavations for the Manufacturers Life Centre in Toronto are discussed. The depth to shale bedrock and the necessity to obtain maximum access to the foundation grade resulted in selecting the use of tie backs into the overburden with or without rakers for supporting the soldier pile lagging system. Full scale load tests were carried out to prove the recommended geotechnical design parameters for the shoring system. Adhesion values obtained from full scale field tests on tie backs agreed closely with the shear strength obtained from laboratory quick triaxial tests. However a full scale loading test on an inclined raker footing gave a higher bearing value compared with conventional design procedures.

ISSN:0008-3674    

DOI:10.1139/t72-015

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Analysis of the problem of braced excavations is complicated by the large number of variables involved and by the complex interaction and behavior of the soil and the supporting materials. For this reason a parametric study was made using the finite-element method of analysis to evaluate the influences of the variables. A rather unique computer modelling technique has been used to accommodate both the large number of variables and the problem of interaction and dissimilar behavior. An example of a computer simulation of a well-instrumented braced cut in Norway is given in sufficient detail to illustrate the applicability of the program.For the parametric study a typical excavation with fully penetrating sheet-pile walls was chosen. Of the parameters concerning soil conditions,the soil deformation modulus was found to have the greatest influence. The relative influence of shear strength, of initialin situstress, of direction of mobilization of shear stress, and of soil-to-pile adhesion is also shown. All of the parameters concerning support conditions are important butpile stiffness and effective strut stiffness are the most important. The influence of prestressing and strut spacing is also shown.

ISSN:0008-3674    

DOI:10.1139/t72-016

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The oedometer consolidation properties of the clay layers of varved sediments from New Liskeard, Ontario have been presented and interpreted with reference to current ideas on soil fabric, bonding, and environment of deposition. The sensitive, brittle nature of the clays is expressed byCcvalues as high as 1.35 and "S" shaped consolidation curves. Preconsolidation above any previous possible overburden pressure is explained by bonding of a net random, flocculated fabric as measured by X-ray diffraction methods. Rates of secondary consolidation up to 4.5%/log cycle at loads close to the preconsolidation pressure reflect structural breakdown of the soil fabric within a very critical range of stress and strain.The flocculated soil structure at New Liskeard is compared with the more parallel fabric of the compositionally similar stratified glacial clays at Welland, Ontario. It is suggested that both deposits developed flocculated soil structures during deposition but that the Welland clays were deposited and loaded more rapidly so that time dependent bonding could not develop to resist compression and retain the open structure as at New Liskeard and most other slowly deposited varved clays in eastern Canada. A literature review is presented in support of these ideas.

ISSN:0008-3674    

DOI:10.1139/t72-017

出版商:NRC Research Press    

年代:1972

数据来源: NRC

ISSN:0008-3674    

DOI:10.1139/t72-018

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The paper presents a description of several uses of radiographs of soil samples that have been found valuable in a geological and geotechnical investigation of varved soil. The radiographs were taken while the soil was still in the sampling tubes, thus enabling examinations to be made of the samples before they were extruded.The uses to which the radiographs have been primarily made are to record in detail the soil stratigraphy, to make examinations of the soil structure and texture, and to help plan laboratory-test programs.Damage to 'undisturbed' samples, in the form of transverse cracks created during the sampling process, was detected by examination of the radiographs. Such features as these might not be detected in extruded samples because they are obscured by smeared soil on the surface of the sample and because cracks would tend to become closed during extrusion.A brief discussion is included of the requirements for making radiographs.

ISSN:0008-3674    

DOI:10.1139/t72-019

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

In Ottawa in 1969 a tied-back sheet pile wall was installed to provide temporary support in one side of a 12 m deep excavation through Champlain Sea deposits to shale bedrock. The wall was designed to permit as little yield as possible in order to safeguard the vital operation of an adjacent transformer building.To assess the performance of this structure, measurements of vertical movements of the surface adjacent to the wall, horizontal displacements of the wall, tendon loads and ground-water pressures were made as the excavation progressed.A series of triaxial tests was carried out in the laboratory to determine the form and magnitude of soil deformations under stress changes approximating those derived from the field measurements. Reasonable correlation is obtained when the results of these tests are used to estimate soil displacements in the field situation. The measured tendon loads are compared with those that would be expected using current design methods.

ISSN:0008-3674    

DOI:10.1139/t72-020

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Study of more than 100 post-glacial landslides of the slump variety in the plains of southern Alberta reveals that a remarkably high proportion (87%) has occurred on slopes of northerly, northeasterly, easterly, and southeasterly aspect. While lithologic and engineering properties of the Upper Cretaceous sediments and Pleistocene glacial mantle of this area undoubtedly have conditioned the geologicalbehaviorof the earth materials affected, it is here contended that microclimatic factors favoring the accumulation and retention of snow on slopes of particular exposure, or aspect, have more strongly controlled the geographicaldistributionof the observed slumps. Reasons for and consequences of microclimatic control are discussed.

ISSN:0008-3674    

DOI:10.1139/t72-021

出版商:NRC Research Press    

年代:1972

数据来源: NRC

ISSN:0008-3674    

DOI:10.1139/t72-022

出版商:NRC Research Press    

年代:1972

数据来源: NRC

ISSN:0008-3674    

DOI:10.1139/t72-023

出版商:NRC Research Press    

年代:1972

数据来源: NRC