摘要:

The results of a series of triaxial compression tests on undisturbed samples of Athabasca oil sand at elevated temperatures ranging from 20 to 200 °C are summarized. The material tested had experienced gradual unloading and depressurization as a result of erosion in the Saline Creek valley near Fort McMurray. More deeply buried oil sands are known to contain much higher concentrations of dissolved hydrocarbon gases in the pore fluids. The measured shear strength of Athabasca oil sand did not change significantly as a result of the increased temperatures that were applied. The strength of Athabasca oil sand (at 20–200 °C) was found to be greater than comparable shear strengths reported for dense Ottawa sand (at 20 °C). Although heating to 200 °C had little effect on shear strength, it is recognized that pore pressure generation during undrained heating may cause substantial reduction of the available shearing resistance, particularly in gas-rich oil sands. The experimental data were used to investigate the influence of such factors as stress path dependency, microfabric disturbance, and heating to elevated temperatures on the shear strength and stress–strain behaviour of oil sand. Curve fitting of the test data suggests that the hyperbolic model is a useful empirical technique for stress—deformation analyses in oil sands. Hyperbolic stress—strain parameters derived from the experimental results for Athabasca oil sand are presented.Key words: oil sand, Athabasca oil sand, tar sand, shear strength, stress, strain, deformation, heating, high temperature, elevated temperatures, high pressure, elevated pressure, thermal properties, drained heating, undrained heating, triaxial compression testing.

ISSN:0008-3674    

DOI:10.1139/t87-001

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The short-term and long-term behaviour of tiebacks anchored in cohesive soils are not well understood, particularly regarding basic component responses of the overall tieback system. There are shortcomings in the predictive capacity for short-term and long-term performances both in individual tiebacks and complete systems. Nevertheless, the methods currently being used to calculate the ultimate resistance to pull-out of individual or groups of tiebacks appear to be conservative.A physical-model laboratory test facility has been designed to investigate the short-term and long-term behaviour of small-scale straight-shafted tiebacks anchored in cohesive soils to provide the following: pore-water pressure measurements, tieback lock-off, measurement of total and residual tieback movement, measurement of load distribution along the tieback, and unearthing of the tieback. The laboratory tieback behaviour has been studied using both consolidated and compacted clay, to indicate the effects of stress history, loading test technique, and overburden pressure on tieback performance.Key words: clay, creep, laboratory tieback test, tieback, soil anchor, consolidation, soil–structure interaction.

ISSN:0008-3674    

DOI:10.1139/t87-002

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Most geotechnical engineers feel that the undrained shear strength measured by the field vane in the surficial weathered crust cannot be fully mobilized during the failure of an embankment built of soft clay deposits. Consequently, the vane strength in the crust is generally reduced by some arbitrary means before stability calculations are performed. This paper presents the results of an experimental program aimed at evaluating the available undrained shear strength in the crust.In situshear box and plate loading tests as well as triaxial compression and extension tests indicate that the available undrained shear strength in the crust is of the same magnitude as the vane strength measured in the intact clay immediately below the crust. This paper also proposes a method to account for the effect of the embankment confinement in the central portion of the foundation. The proposed methodology is checked by a back analysis of the failure of the Olga test embankment built at Matagami, Quebec.Key words: vane test, vane test correction, weathered crust, shear box, plate loading test, embankment stability.

ISSN:0008-3674    

DOI:10.1139/t87-003

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

This paper describes geotechnical aspects of a reservoir enlargement project located in the headwaters of the Amazon Basin, in the Andean Cordillera of central Bolivia. This reservoir serves the Corani and Santa Isabel hydroelectric stations, which harness in sequence 1409 m of head below reservoir level. The project involved raising the existing Corani dam and constructing a diversion scheme to convey water from the adjacent Malaga River watershed into the enlarged reservoir. The Corani dam was raised 5 m by adding a zoned earth–rockfill section to the existing embankment dam and constructing a concrete overflow spillway that incorporated the existing masonry structure. The Malaga diversion scheme involved construction of four intakes, 1.7 km of canals, and 12.1 km of tunnels. The tunnels were driven through a wide variety or rock types ranging from good-quality quartzites to squeezing shales. The project was completed in 1984.Key words: dam raising, tunnel, grouting, shotcrete, canal, squeezing shales, underseepage, hydropower, spillway.

ISSN:0008-3674    

DOI:10.1139/t87-004

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

During investigations for a damsite on the Sand River, Alberta, an 80 m thick silt deposit in a valley some 500 m across was encountered. The most distinctive feature of the deposit is the uniformity of the silt, with thicknesses of up to 50 m occurring as a single layer uninterrupted by seams of significantly different material. The silt unit is believed to be the result of very uniform, prolonged depositional conditions in a subglacial river. The silt consists largely of silica grains between 10 and 60 μm, and although it contains clay, in some aspects its behaviour is close to that of sand.Evidence suggests that the present valley is a tunnel valley formed by meltwaters flowing through the underside of a glacier. The implications for the engineering geology of the damsite investigated are discussed and some geotechnical properties of this unusual silt deposit are presented, particularly as they affect settlement prediction.Key words: tunnel valley, glacial silt, earth dam, settlement, airphoto interpretation.

ISSN:0008-3674    

DOI:10.1139/t87-005

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Results of laboratory and field construction and pavement performance studies have revealed that some apparently substandard or borderline—by temperature zone standards—tropical gravel materials can be used successfully for the construction of low-cost pavements in subhumid climatic zones.The geotechnical characteristics of suitable paving materials have been defined from results of studies carried out on satisfactory and poor road sections over a period of 5–6 years.Important correlations were found between the bearing strength (CBR) on the one hand and some moisture index properties as well as the products of the fines content and these index properties on the other.It is shown that the product of the fines content and some moisture index properties form a useful basis for identifying suitable materials for pavement construction in the moist subhumid climatic zone of Ghana.The paper is a contribution to the identification and characterization of nontraditional tropical and residual paving materials in relation to the environment.Key words: pavements, California bearing ratio (CBR), index properties, fines content, subhumid climate.

ISSN:0008-3674    

DOI:10.1139/t87-006

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

This paper presents a case record of the settlement observations of road approach embankment and bridge and overpass abutments built on deep, soft, compressible, deltaic deposits at Vancouver International Airport. The field data are analysed, the observed settlements are compared with calculated predictions, and conclusions are presented.Key words: road embankment, bridge abutment, settlement, observation, prediction, interpretation.

ISSN:0008-3674    

DOI:10.1139/t87-007

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Both abutments and all piers of the Petrofka bridge are on a landslide. The bridge has performed satisfactorily for 23 years, indicating the factor of safety of the Petrofka landslide is greater than unity. This stability is abnormal because landslide slopes on bedrock clays (shale) in this region are notoriously unstable. A dormant landslide is difficult to analyze because the input parameters must represent a condition of limiting equilibrium.The Petrofka landslide is 70 m high, 880 m long, 3000 m wide, and up to 100 m thick. The shear zone is in highly plastic, montmorillonitic clays in an unnamed formation of probable Tertiary age. The Upper Cretaceous Lea Park, Judith River, and Bearpaw formations and the unnamed formation underly the landslide and are restricted to a collapse structure resulting from dissolution of Devonian evaporites.A retrogressive mechanism developed as valley downcutting progressed. The pore-water pressures could be estimated from the hydraulic head in the artesian aquifer of the Judith River Formation. The hydraulic head was maintained at critical as the valley deepened until the Judith River Formation was eroded downstream. The landslide was active for only a few hundred years, between 11 500 and 11 000 years ago.The back-calculated effective angle of friction for the bedrock clay (shale) was estimated at between 5.6° and 6.5°, assumingc′ = 0, resulting in a present-day factor of safety between 1.2 and 1.3.Key words: back analysis, dormant landslide, collapse structure, artesian pressure, historical simulation, residual shear strength.

ISSN:0008-3674    

DOI:10.1139/t87-008

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Analytical elastoplastic solutions for stresses and displacements around a circular opening have been developed, using two different yield criteria and a nonassociated flow rule. The effects of dilatancy and postpeak decrease in strength are included in these solutions. It is shown that the two different yield criteria lead to practically identical results, while the dilatancy angle plays an important role in controlling radial displacement. Four case histories, one in soft fractured rock and three in a heavily overconsolidated stiff clay, are analyzed. The calculated radial displacements along the crown line are consistent with results of field measurements.Key words: tunnels, elastoplastic analysis, stress, strain, dilatancy, yield criteria, postpeak strength, nonassociated flow rule, soft rock, stiff clay.

ISSN:0008-3674    

DOI:10.1139/t87-009

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

A theoretical examination of a number of factors affecting the behaviour of drilled piers in soft rock is presented. Firstly, the fundamental difference between tests commonly used for determining the peak average side shear resistance along a socketed pier is discussed. Secondly, the effect of interface strength parameters, dilatancy, and the relative Young's modulus of the pier and rock upon the average mobilized side shear resistance is examined. Thirdly, a series of theoretical solutions are presented in the form of design charts to provide a simple means of estimating the load—deflection response of piers both before and after full slip has developed along the pier shaft. Finally, the effect of weak horizontal seams adjacent to the pier is considered.Key words: drilled shafts, piers, piles, rock, theory, settlement, displacement, analysis.

ISSN:0008-3674    

DOI:10.1139/t87-010

出版商:NRC Research Press    

年代:1987

数据来源: NRC