摘要:

The purposes of the paper are to examine the deepening of valleys in clay deposits of Eastern Canada and in particular to look at the changes in the groundwater regime and slope stability conditions during valley formation. Field observations and laboratory testing indicate that the rate of valley deepening in Champlain clay deposits is of the order of only a few millimetres a year, owing to the low erodibility of the intact clay. The clay banks are, however, more erodible, owing to alteration and fissuration.The stratigraphy of Eastern Canadian clay deposits can be simplified by considering it to be a stratum of low permeabilityconfined between two boundary layers of relatively high permeability, which are the till layer at the base and a weathered crust or coarse-grained layer at the top. As the valley bottom get closer to the bottom till layer, the groundwater regime, and consequently the stability conditions, are modified. During the process of valley formation, the groundwater regime passes through astage where the conditions are rather detrimental to slope stability as it evolves toward conditions that enhance bank stability. Those changes in stability conditions happen over geological time more rapidly or less, depending on clay erodibility.Key words: soft clay, valley formation, slope stability, groundwater, erosion, erodibility.

ISSN:0008-3674    

DOI:10.1139/t86-039

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Soil investigation programs established the presence of locally loose to medium dense noncohesive foundation materials at three major industrial project sites. It was neccessary to densify these materials to ensure that unacceptable differential settlements did not occur between separate foundations and to reduce the potential for liquefaction of the looser zones in the event of seismic disturbance. Horizontal ground accelerations of 0.05, 0.1, and 0.3 gwere used in the respective seismic analyses for the three sites. Four different techniques for in-place compaction were employed to densify the loose to medium dense soils: vibro and impact compaction, compaction piling, and deep blasting.Site descriptions and soil parameters measured are presented. A short explanation of design considerations and production work procedures is followed by a detailed comparison of the improvements obtained, measured in terms of standard or static cone penetration resistance and true relative density. Problems encountered and phenomena observed during performance of the work are described, such as the time-dependent strength increase in disturbed sands.Key words: compaction piling, deep blasting, impact compaction, vibrocompaction, foundation, penetration tests.

ISSN:0008-3674    

DOI:10.1139/t86-040

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The lateral soil pressures, tip load, and displacements of instrumented single rigid model piles in homogeneous loose sand and soft clay under vertical eccentric and central inclined loads have been investigated. A comparison of the test results with theoretical pressure distributions and displacements of the pile for the working load range has been made. Reasonable agreement has been found between the observed and predicted displacements and suggested nondimensionalp–ycurves. The analyses are also compared with the results of some field case records.Key words: displacements, clay, eccentric load, horizontal load, lateral soil pressure, instrumentation, model test, pile, sand.

ISSN:0008-3674    

DOI:10.1139/t86-041

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The equations of statical equilibrium and the failure criterion for the soil are insufficient to render a slope stability analysis determinate. Generally, the problem is resolved by making assumptions regarding the interslice forces. Calculated safety factors generally do not vary widely as a result of different assumptions. However, difficulties are sometimes associated with the convergence of the nonlinear solution when assumptions deviate excessively from realisticin situstress conditions.This paper presents the results of an elastic analysis for the computation of interslice normal and shear forces acting within a soil mass. The directions of the resultant interslice forces were computed using a two-dimensional, finite element analysis with constant strain elements. Simpson's method of integration was used to develop a function,f(x), describing the directions of the resultant interslice forces. The function was found to be bell-shaped with the peak occurring approximately at mid-slope (i.e., halfway between the crest and the toe). A generalized empirical function has been proposed. The equation takes the form of an extended error function in which the constantscandnare functions of the slope inclination, and theK-constant is a function of the slope inclination and the depth of the slip surface. Slope analyses using the proposed function show a line of thrust near the one-third point. No problems have been observed with convergence of the solution.Key words: slope stability, safety factor, method of slices, interslice forces, finite elements, interslice force functions, clay, slopes.

ISSN:0008-3674    

DOI:10.1139/t86-042

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The results of a recentin situtesting program to establish standard penetration test – cone penetration test (SPT–CPT) correlation for the windblown calcareous desert sands of Kuwait are presented and analyzed. The program consisted of auger borings and static cone tests at five sites along a 35 km long corridor. The resulting correlation was employed for prediction of the allowable soil pressure of footings at seven sites in Kuwait where load tests were carried out on square concrete footings placed at a depth of 1 m below ground surface. A comparison of the measured to the predicted soil pressures using the Schmertmann method indicated very close agreement. The average ratio of measured to predicted soil pressure is 93% for the seven test sites. Recommendations are made for further testing to determine the long-term settlement components due to creep and cyclic loading.Key words: load tests, sands, footings, allowable pressure, settlement, field tests, borings, cone penetration tests.

ISSN:0008-3674    

DOI:10.1139/t86-043

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Erosion of alluvial stream banks is of scientific and economic significance. The principal focus of this investigation was stream bank erosion caused by piping of sand seams, which leads to collapse of overlying strata. Analyses were performed to determine which parameters of the riverbank system are most important in controlling the amount and rate at which piping occurs. Among the failure mechanisms studied were wedge failure of large masses and surficial shearing (slabbing failure) of bank faces. Analyses showed that the most important factors governing piping were permeability and capillary suction in sand seams, slope of sand seams, and water in tension cracks behind the bank face. Flood hydrograph parameters (height of rise and duration of event) were less important, though significant. Whereas unit weight, cohesion, angle of internal friction, and water in tension cracks influenced wedge failures, only unit weight and cohesion directly influenced slabbing failures; however, those parameters influencing piping indirectly also influenced slabbing failures. Results of the analyses agreed closely with field observations.Key words: alluvial stream bank, erosion, sand seam, slope stability, piping, tension cracks, slabbing.

ISSN:0008-3674    

DOI:10.1139/t86-044

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

An experimental and theoretical study was conducted to assess the maximum tensile forces mobilized in a reinforced earth retaining wall, subjected to a vertical surcharge strip load or the combined action of vertical and horizontal surcharge strip loads. A simple design method for determining the maximum magnitude of the tensile force and its distribution with depth of the reinforced earth backfill was developed. The design method takes into consideration the ability of the reinforced earth wall system to retain its internl equilibrium by stress transfer from overstressed regions to those regions where the reinforcing elements have not yet reached their full frictional or strength capacity. The effect of the magnitude and location of the strip load on this phenomenon of stress transfer is shown. Favourable comparisons were obtained between the results given by the proposed design method and those from model tests.Key words: reinforced earth, vertical and horizontal surcharge strip load, reinforcing elements, internal stability, stress transfer.

ISSN:0008-3674    

DOI:10.1139/t86-045

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The prediction of stress changes and deformations arising from ground heating requires the coupled solution of the heat transfer and consolidation equations. Heat consolidation as a class of problems is distinct from other thermally induced consolidation problems involving processes such as frost heave and thaw consolidation in that it involves heating to elevated temperatures well above normal ground temperatures. Two of the important parameters required in analyses of heat consolidation problems are thermal expansion coefficients and a coefficient of thermal pore pressure generation.Relationships describing thermal expansion behaviour and thermal pore pressure generation in oil sands are presented. Both drained and undrained thermal expansion coefficients for Athabasca oil sand were determined by means of heating experiments in the temperature range 20–300 °C. The thermal pore pressure generation coefficient was evaluated in undrained heating experiments under constant total confining stresses and under constant effective confining stresses. The equipment and experimental methods developed during this study are appropriate for determination of thermal expansion and pore pressure generation properties of oil sands and other unconsolidated geologic materials.Key words: thermal expansion, oil sand, tar sand, thermal pore pressure generation, heat consolidation, thermal consolidation, coefficient of thermal expansion, thermal stresses, ground heating, thermally enhanced oil recovery, thermoelasticity, undrained heating.

ISSN:0008-3674    

DOI:10.1139/t86-046

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The ice lensing phenomenon in layered soils, a condition that simulates the process of ice growth in varved soils, has been studied experimentally. Under the limited conditions of layer thicknesses, soils used, freezing rates, and moisture conditions, ice lenses formed at the face of the fine-textured (clay) layer when it was encountered by the freezing plane. Only minor heaving occurred in the coarse-textured (silt) layer when its thickness was increased.Key words: frost action, ice lensing, frost heaving, varved soils, layered soils.

ISSN:0008-3674    

DOI:10.1139/t86-047

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The 6 m diameter, 30 g-tonne geotechnical centrifuge at Queen's University is described. Results from eight model tests, carried out on plain cemented sand samples representing mine backfills, are presented. These data show that the stable prototype backfill heights obtained from centrifuge tests exceed the failure heights predicted from unconfined compression testing by factors averaging about 1.8. This factor is explained by a combination of geometrical and behavioural effects. Still photographs of typical backfill failures in the centrifuge are included and these indicate that unacceptable ore dilution and recovery costs would be associated with the prototype failures in plain cemented tailings backfills.Key words: geotechnical centrifuge, mine backfill, model tests, cemented sand.

ISSN:0008-3674    

DOI:10.1139/t86-048

出版商:NRC Research Press    

年代:1986

数据来源: NRC