摘要:

Marine geotechnical engineering in Canada is over one hundred years old, having started with overwater drilling and testing for bridges and nearshore structures. Its growth has been sporadic, with not much attention being directed to the geotechnical properties of marine soils until the late 1970's when design of artificial islands made up of large caissons started to develop. For about the last 15 years, marine geotechnical engineering has been driven by the oil and gas industry. Most of the action has been in the Beaufort Sea, where complex site conditions have necessitated detailed geotechnical field drilling, sampling programs, andin situtesting. Very little geotechnical engineering research work or site investigation has been carried out off the east coast except for the Hibernia site on the Grand Banks. In the coming years we can expect to see dramatic changes in site investigation methods. The use of robotics and expert systems coupled with innovative geophysical techniques could dramatically change our methods of site characterization and measurement of geotechnical properties.Key words: marine geotechnical engineering, Beaufort Sea, Grand Banks, Scotian Shelf,in situtesting, geophysical – geotechnical relationship, future trends.

ISSN:0008-3674    

DOI:10.1139/t88-023

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Results of an investigation of the response of footings on sand, under eccentric and inclined loads, are presented. Apparatus was constructed that could simultaneously apply loads to footings at any eccentricity and inclination, without imposing restraints on the footing displacements. The experimental results are interpreted, compared with published data, and a method for predicting vertical and horizontal displacements and rotations of loaded footings on sand developed. At low load levels the analysis generates the elastic half-space solution, which is then augmented to provide the complete nonlinear response of the footing. In addition, interaction diagrams between the vertical loads, horizontal loads, and moments that cause failure of the footing are presented.Key words: footing, sands, eccentric loading, inclined loading, displacement, rotation, bearing capacity.

ISSN:0008-3674    

DOI:10.1139/t88-024

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The geotechnical engineering profession is quite familiar with stiff fissured and jointed clays where discontinuities are found on a macroscopic scale. However, there has not been, until recently, a systematic investigation of the crack propagation phenomena involved in the failures of such clays. This paper presents the first phase of an investigation whose aim is to understand, describe, and quantify the mechanisms involved in crack propagation. The experimental investigation indicates that, in a mode II type of fracture, a well-defined damage zone propagates in front of the crack. In this zone, the structure of the clay is shown to be substantially altered. The damage is quantitatively characterized and a thermodynamic approach to the analysis of crack and damage propagation is suggested.Key words: stiff clay, fracture, crack layer, damage zone, strip densification.

ISSN:0008-3674    

DOI:10.1139/t88-025

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The results of full-scale pile load tests, field monitoring, and laboratory tests on undisturbed soil samples have been used to compare soil parameters determined fromin situtests and in the laboratory for pile design in granular deposits. These results indicate a close agreement between the field- and laboratory-determined rebound or recompression index of oil sand. Also, a good agreement is indicated between field-measured and calculated pile head settlements. However, the measured average skin friction along the pile shaft in sandy till is about 20% more than the calculated values obtained from empirical and finite element analytical work using laboratory- and field-determined soil parameters. Theoreticalt–zcurves provided a good approximation of the field behaviour for the pile shaft resistance.Key words: drilled piles, belled piles, oil sand, skin friction, rebound, settlement, load test.

ISSN:0008-3674    

DOI:10.1139/t88-026

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

This paper proposes a general compressive strength criterion for anisotropic rock materials under multiaxial states of stress. The proposed criterion is a generalization of the Von Mises' criterion for yielding of ductile metals, which has also been used previously as a strength criterion for brittle fracture in the spirit of both being limits of linear elastic behavior. The presently proposed criterion takes into consideration the effects of the confining pressure, the various stress components, and the material anisotropy on rock material failure in a multiaxial stress state. To verify the applicability of the proposed criterion, it has been used to construct the failure envelopes for several types of rock materials. Consequently, the constructed failure envelopes and the corresponding experimental results have been compared. In all cases, a close agreement with the experimental results has been achieved. This result demonstrates the versatility and applicability of the proposed strength criterion in representing the compressive strength behavior of anisotropic rock materials under complex multiaxial states of stress.Key words: strength, rock materials, anisotropy.

ISSN:0008-3674    

DOI:10.1139/t88-027

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Footings placed at shallow depth in bridge approach embankments can be used to reduce the cost and to improve the performance of bridge supports. The embankments frequently terminate in slopes dropping to underpass level, and the footings therefore have lower capacity than that for footings on level ground. The needed design procedures have not been well validated.The paper describes a new solution using the method of stress characteristics for footing capacity in cohesionless slopes. The soil is assumed to havec = 0, = constant, γ > 0. Particular attention is paid to modelling the asymmetric nonfailing zone immediately beneath the footing. Solutions for various slope angles and friction angles have been obtained for footings placed at the crest of the slope withD/B = H/B = 0, and forH/B = 0.5, 1.0, and 2.0;D/B = 0.5 and 1.0. The theoretical bearing capacities are compared with experimental values from two series of laboratory tests.Key words: bearing capacity, footings, failure, bridge abutments, slopes, sand, cohesionless, stress characteristics.

ISSN:0008-3674    

DOI:10.1139/t88-028

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The pressuremeter has the potential to measure the creep parameters of icein situ, that is to say, in the field, in ice at its natural temperature and natural stress environment, and in ice that has not been disturbed by sampling and handling. To prove that the pressuremeter can in fact be used to measure creep properties, a series of pressuremeter tests were run in the laboratory in poly crystalline ice at −2°C. It was found that (1) the particular pressuremeter used maintained an ability to measure creep deformation accurately over a period of 7 weeks, (2) the test results agree for the most part with the findings of other investigators who have used uniaxial compression tests, and (3) the pressuremeter brings into question at least one of the more common assumptions regarding primary creep.Key words: ice, freshwater, creep, pressuremeter.

ISSN:0008-3674    

DOI:10.1139/t88-029

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Specimens of potash rock from the Rocanville mine of the Potash Corporation of Saskatchewan were subjected to uniaxial compression tests and to time-dependent creep tests under static, uniaxial loading.During the first cycle of loading, the main sources of the measured strain are compaction and dilation at grain boundaries and consolidation of the clay phase. The crystals of halite and sylvite deform elastically at low stress and in a brittle manner at high stress. There is little, if any, evidence for constant-volume plastic deformation at any level of uniaxial stress.The stress–strain curve can be divided into three parts, each representing a different dominant deformational process: a low-stress quasi-elastic, an intermediate-stress ductile, and a high-stress brittle mechanism. The three parts are separated by the yield point (1–8 MPa) and the crack initiation point (10–13 MPa). The strength of the Rocanville potash specimens ranged between 15 and 18 MPa.The deformation of potash rock is strongly time dependent. There is evidence for the existence of all three stages of creep: transient, steady-state, and tertiary. There is very little interrelationship between the axial and lateral creep strains; the volumetric strain is negative at low stress and positive (dilatant) at high stress, but rarely, if ever, constant.Key words: creep, dilatant, ductile, elastic, fracture, microfracture, plastic, potash, salt.

ISSN:0008-3674    

DOI:10.1139/t88-030

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

This work stems from field studies of convergence within gate roads leading to three longwall coal faces with different strata and mining conditions. The influence of production on the stability of these roads is illustrated. Empirical time-dependent equations are developed to express and predict the behaviour of the roadways. The particular contribution of the roadway floor and sides to the total closure of the gate roads has also been investigated. The mode of deformation and failure, observed by scanning electron microscopy within the immediate vicinity of underground gate roads, is also described. The application of this analysis is in the planning of production panels in soft tabular deposits, the dimensioning of gate roads, and the stability and performance prediction of such roadways and their supports.Key words: soft mine floors, longwall mining, gate road stability, coal roads, soft underclay floors.

ISSN:0008-3674    

DOI:10.1139/t88-031

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Modelling the flow of brine through potash tailings requires that the saturated and unsaturated hydraulic properties of the tailings be established; in particular, the relationships of fluid content and permeability to matric suction are required. Thein situand laboratory testing techniques used for determining these properties are described and the results are presented.Numerical modelling techniques for the flow of brine through potash tailings are demonstrated by performing a computer simulation of an open-trench infiltration test conducted at the Lanigan Division Potash Mine in Saskatchewan. The responses of the field instrumentation during the infiltration test were compared with the results of the simulation. The simulation utilizes the measured fluid content versus suction curves and the calculated permeability versus suction curves as input parameters. Good agreement was observed between the measured and simulated field responses. The effects of varying the hydraulic properties of the tailings are examined to arrive at a better understanding of the flow mechanism involved.Key words: saturated–unsaturated, seepage, finite element modelling, brine, potash, tailings, infiltration.

ISSN:0008-3674    

DOI:10.1139/t88-032

出版商:NRC Research Press    

年代:1988

数据来源: NRC