摘要:

Repeated load drained tests on Leda clay, as related to subgrade performance, are reported. A threshold stress divided the performance into failing and stable specimens. For the stable specimens the resilient modulus attained equilibrium at about 105cycles but varied with stress level. Permanent strains continued even at low stresses.

ISSN:0008-3674    

DOI:10.1139/t79-001

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

This paper describes a triaxial-vane apparatus constructed at the Division of Building Research, National Research Council of Canada, Ottawa. A series of tests was conducted on a soft marine clay from South Gloucester, Ontario. Various consolidation pressures were used to study the effect of pressure on vane strength. The test results show that the vane strength is relatively insensitive to a change in vertical consolidation pressure only, but increases steadily with increase in the all-around or horizontal consolidation pressure. This phenomenon is explained using an analysis that incorporates strength anisotropy. The practical implications resulting from this study are also discussed.

ISSN:0008-3674    

DOI:10.1139/t79-002

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The stability of slopes before and after removal of forest cover was investigated. Porewater pressures and shear strengths were measured and the soil properties were determined by laboratory andin situtests. A model of the soil–root system was developed to evaluate the contribution of tree roots to shear strength. The computed safety factors are in general agreement with observed behaviors of the slopes. Decay of tree roots subsequent to logging was found to cause a reduction in the shear strength of the soil–root system.

ISSN:0008-3674    

DOI:10.1139/t79-003

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Rate effects on one-dimensional compressibility and undrained shear strength of a heavily overconsolidated naturally cemented clay have been studied. It is shown that in constant rate-of-strain consolidation tests the compressibility increases and the apparent preconsolidation pressure decreases with progressive decrease in rate of strain. Also a decrease in undrained strength is shown to occur with slower rates of strain in constant rate-of-strain shear and with increased time of sustained loading in creep tests. Undrained strengths from the two types of shear tests have been correlated.

ISSN:0008-3674    

DOI:10.1139/t79-004

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Field measurements indicate that piles are sometimes bent during driving. This paper reports on the results of an experimental study, at laboratory scale, of the behaviour of bent single piles when subjected to vertical loads. Varying degrees of bend were adopted for both friction and end bearing piles. The test piles, which were embedded in a cohesionless soil, were instrumented to measure the distributions of axial load, bending moment, and transverse shear along the pile shaft.The behaviour of bent piles was found to be far more complex than that of straight piles. For both the friction and end bearing piles, the response of the piles was governed by the degree of bend and the magnitudes of the moments and shears were significant at all levels of the applied load. An important feature in the pile response was the large residual moments and shears locked in the pile on unloading. The implications of the observed pile behaviour in relation to practice are discussed. A review of the reported cases of pile bending is also presented.

ISSN:0008-3674    

DOI:10.1139/t79-005

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Four aquifer tests were completed at a site near Forestburg, Alberta, in order to determine aquifer parameters of a coal seam and thus aid in the evaluation of an underground gasification experiment and assess the effects of gasification on the groundwater regime.Analysis of the two pre-gasification aquifer tests indicated that the coal seam was a confined aquifer with small aquifer parameters and a strongly anisotropic hydraulic conductivity that appeared unrelated to known regional fracturing directions. The effect of this anisotropy on controlling directions of gasification was not established.The first post-gasification aquifer test indicated that the groundwater regime of the coal seam had been changed in various ways. Regionally, a general increase in hydraulic conductivity and a more pronounced anisotropy were observed. On a smaller scale, storage coefficients in the gasified block were greatly increased due to a change in the physical character of the coal. Subsequent excavation that exposed the gasified block confirmed these observations.The second post-gasification aquifer test indicated that fracturing in the coal seam was not consistent and that in undisturbed coal seams the direction of regional major fracturing and the major axis of anisotropy do, in fact, coincide.

ISSN:0008-3674    

DOI:10.1139/t79-006

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Preliminary results of laboratory studies on the behaviour of model piles of wood, concrete, and steel, having different surface finishes, embedded in artificially frozen sand and subject to constant loads, are reported in this paper. The displacement rate, was found to vary with the applied stressf, according to a steady state creep equation of the type, as found for other viscoelastic materials such as metals at high temperature. The value of the exponentnvaried between 6.7 and 9.1 for various types of piles.The results agreed favourably with field data obtained from pile pull-out tests carried out at Gillam and Thompson, Manitoba. The value ofnfrom Gillam and Thompson tests, 8.05 and 7.5, respectively, were within the range of the present experimental values. Comparison with pile pull-out tests carried out in ice, and theoretical predictions for ice showed that the value of the exponentnwas much larger for frozen soil than for ice. The bearing capacity at a particular displacement rate was also found to be almost an order of magnitude larger in frozen soil than in ice.

ISSN:0008-3674    

DOI:10.1139/t79-007

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Sulphur-bound soils and a lightweight aggregate sulphur concrete have been studied for potential use as structural frost insulating base materials in roadway construction. Sulphur-bound materials show rapid strength gain and sulphur has a low thermal conductivity (0.27 W/(m ∙ K)). Laboratory studies have shown, however, that, unless specially treated, sulphur-bound soil that contains significant swelling clay disintegrates in water. The laboratory studies were more favourable for the lightweight aggregate sulphur concrete and this material was used as a base course in two test sections of roadway. The test sections and a control section instrumented with thermocouples to measure temperatures to depths of 1.52 m were monitored for 6 winter months. A Dynaflect deflection apparatus was used for structural assessment. It was found that both frost penetration and the length of the subgrade freezing period were reduced and that the structural integrity of the pavement system was improved when lightweight aggregate sulphur concrete was introduced into the base course of the roadwa

ISSN:0008-3674    

DOI:10.1139/t79-008

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Undisturbed oil sand is very dense and has a relatively highin situshear strength. However, there is gas present within the oil sand, which causes it to swell once confining pressures are removed, and this results in a significant reduction in the strength of the material. Consequently, this swelling behaviour is a major concern in the design of tunnels in oil sand.Saline Creek Tunnel, located immediately south of the town of Fort McMurray, Alberta, is the first permanent tunnel constructed in the Athabasca Oil Sand. The finished diameter of the tunnel is 4.4 m and the tunnel is about 107 m long of which approximately 73 m is entirely within medium to rich oil sand. The maximum depth of overburden above the tunnel crown is 27.5 m.This paper documents the geotechnical investigation and design of the tunnel. The method of construction and the temporary and permanent tunnel support systems are described. Detailed observations on the behaviour of the oil sand around the tunnel opening during construction are also presented.

ISSN:0008-3674    

DOI:10.1139/t79-009

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Uniaxial compression tests were performed on sedimentary rocks of five different geological formations at various sites in southern Ontario. The deformation behaviour is analysed in terms of the cross-anisotropic elastic theory and typical sets of five independent parameters for each rock unit have been obtained. It is shown that some of the rock types are significantly anisotropic both in deformation and strength behaviour. The practical relevance of the results in the analysis and design of underground structures in these rocks is discussed.

ISSN:0008-3674    

DOI:10.1139/t79-010

出版商:NRC Research Press    

年代:1979

数据来源: NRC