摘要:

Field and associated laboratory experiences with closed-system freezing in earth embankment dams and canals are presented. This type of freezing can cause a redistribution of soil density and moisture, which needs to be considered in the design of soil structures used as water barriers in cold regions. Frost-depth measurements made during the winter of 1978–1979 on two earth dams during interruption of their construction and on the Teton Dam remnant in the State of Idaho, U.S.A., are shown, along with associated soil conditions, air-freezing indexes, and insulating effects of snow and, for one dam, a loose soil cover. Some trends of density and moisture changes near the embankment surfaces were established. Keeping in mind known effects of freezing on soils, the paper raises questions about possible changes in soil density and shrinkage of embankments in contact with bedrock abutments that might adversely affect the safety of earth dams.Key words: dams (earth), canals, frost action, frost protection, soil density, soil moisture, soil shrinkage, soil tests, Teton Dam.

ISSN:0008-3674    

DOI:10.1139/t86-001

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

A yield equation for isotropic, homogeneous, geotechnical materials has been developed and applied to the work-softening and work-hardening behaviour of granular rocks. The development of this yield equation was based on a comparison of the work done and the energy dissipated within a sample undergoing yield in triaxial compression. The formulation takes into account friction and dilatancy and also an experimental observation leading to the derivation of a nonassociated flow rule. The analysis of extensive experimental data indicates that the flow rule is consistent for work-softening and -hardening behaviour, and validates the application of the incremental theory of plasticity to the irrecoverable strain behaviour of rocks in which the predominant mode of deformation is cataclastic. The yield equation, which is expressed in terms of readily indentifiable material parameters, predicts yield strength or strength at a given value of plastic strain invariant, and relates stress and strain increments at yield.Key words: rocks, yield, plastic strain, work softening, work hardening, energy, dilatancy, nonassociated flow.

ISSN:0008-3674    

DOI:10.1139/t86-002

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

A set of clay shales associated with coal measure strata has been examined to determine the mechanisms that lead to slaking on immersion in water. The two main mechanisms for the slaking of small unconfined samples are (a) compression of entrapped air and (b) osmotic swelling of expansive clay minerals if the dominant exchangeable cation is sodium. In the absence of osmotic swelling, pore-air compression can induce slaking in clay shales of bulk densities less than 2.27 Mg/m3. Osmotic swelling of clay shales occurs in samples with bulk densities less than about 2.45 Mg/m3, but slaking by this mechanism occurs only for samples with densities less than 2.34 Mg/m3. Dispersion of clay from clay shales develops only after slaking commences, and the extent of dispersion depends on the nature of the interparticle bonds.Key words: clay shales, clays, coal measure rocks, slaking, dispersion, porosity, density.

ISSN:0008-3674    

DOI:10.1139/t86-003

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Extensivein situtesting and undisturbed sampling were carried out near two steel piles to determine the long-term state of a clay in which these piles had been driven 7 years before. Results show that this material exhibits a rigidity that varies with the distance from the pile. The average rigidity in the zone of study is representative of a slightly destructured clay. The shear strength of this clay is, in most cases, equal to the shear strength of the intact material except in the zone located at depth greater than 3.5 m and within 30 cm of the pile wall, where lower shear strength values were consistently monitored. It is believed that reconsolidation after driving took place in this last case under relatively low stresses.Key words: piles, clays, ageing, destruction, reconsolidation, shear strength, rigidity, limit state.

ISSN:0008-3674    

DOI:10.1139/t86-004

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

A numerical method for the calculation of the distribution of displacements for tunnelling in clays has been developed. The method employs an orthotropic elastic – perfectly plastic soil model that takes into account various sources of ground loss and soil–lining interaction. Both undrained and drained analyses have been carried out and the results are compared with the measured soil displacements of two instrumented arrays at the Thunder Bay tunnel. It is shown that the range of maximum settlements, the shape of the settlement troughs, and the pore pressure change, as well as the magnitude and direction of spatial displacements obtained from the analyses, compare reasonably well with the results of field measurements for both short- and long-term conditions.Key words: tunnelling, clays, anisotropy, elastic–plastic displacements, settlement trough, Thunder Bay tunnel.

ISSN:0008-3674    

DOI:10.1139/t86-005

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Data representing the seasonal variation of thermal conductivity of the ground at depths within the seasonally active freezing/thawing zone are presented for a number of different soil conditions at four sites across Canada. An inexpensive probe apparatus suitable for routine field measurements is described.In all the cases examined, significant seasonal variations were confined to the first few decimetres. In addition to distinct seasonal differences associated with phase change, quite large changes occurred during the period when the soil was thawed in those cases where seasonal drying was possible. Below the seasonally active zone, thawed soil conductivities did not differ greatly among the three nonpermafrost sites in spite of soil composition ranging from marine clay to sandy silt. The data suggest that, even within a given soil layer, quite significant differences in thermal conductivity may be encountered in engineering structures such as embankments, presumably because of differences in drainage conditions.Key words: thermal conductivity, field measurements, phase relationships, drying, permafrost, clay, silt, peat.

ISSN:0008-3674    

DOI:10.1139/t86-006

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The town of Regina Beach is constructed on landslides along the Last Mountain Lake valley, a glacial meltwater channel in south-central Saskatchewan, Canada. The landslides are retrogressive in nature and are seated in bentonitic clay shale of the Bearpaw Formation. A study was conducted at Regina Beach to determine the sensitivity of the slopes to changes in slope geometry as a result of regrading, or groundwater changes. Back-calculated shear strength was compared with values from the laboratory and from other landslides in Cretaceous bedrock shales. Modest changes in grading of the toe areas would result in significant reductions in the local stability and future movements of upslope portions of the landslide. Development should minimize the amount of grading. Increased slope movement due to breaks in watermains was observed and measured. This correlated well with analysis. Development in landslide areas must assume that differential vertical and horizontal movements will occur. Proper site reconnaissance should identify optimum locations for buildings and services such that the risk of rupture or damage is minimized.Key words: landslide, retrogressive, back analysis, residual shear strength, Bearpaw Formation, inclinometer, slope movement.

ISSN:0008-3674    

DOI:10.1139/t86-007

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The U.S. Geological Survey used a recently developed heat-pulse flowmeter to measure very slow borehole axial water velocities in granitic rock at a site near Lac du Bonnet, Manitoba, Canada. The flowmeter was used with other geophysical measurements to locate and identify hydraulically conducting fractures contributing to the very slow vertical water flow in the two boreholes selected for study. The heat-pulse flowmeter has no moving parts and operates on the tag–trace principle. It is an improved version of the flowmeter developed by the Water Research Centre in England in 1975. The U.S. Geological Survey's heat-pulse flowmeter has a flow-measuring range in water of 0.06–6 m/min, and can resolve velocity differences as slow as 0.01 m/min. This is an order of magnitude slower than the stall speed of spinner flowmeters. The flowmeter is 1.16 m long and 44 mm in diameter. It was calibrated in columns of 76 and 152 mm diameter, to correspond to the boreholes studied. The heat-pulse flowmeter system is evaluated, and problems peculiar to the measurement of very slow axial water velocities in boreholes are discussed.Key words: flowmeter, borehole flow, low flow, borehole geophysics.

ISSN:0008-3674    

DOI:10.1139/t86-008

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

Experience at investigated damsites along the South Saskatchewan River in the 1950's showed the importance of interrelated studies in site investigation, geology, and airphoto interpretation. As a result of this work, landforms along the dam abutments were identified as landslide masses rather than hummocky morainal materials. The engineering implications were significant. Advanced techniques of remote sensing offer further opportunities for clarifying the role of geology in new areas of activity being undertaken by geotechnical engineers.Key words: riverbanks, damsite geology, geomorphology, airphoto interpretation, remote sensing.

ISSN:0008-3674    

DOI:10.1139/t86-009

出版商:NRC Research Press    

年代:1986

数据来源: NRC

摘要:

The methods developed to predict the action of eroding fluid on cohesive soils lead to contradictory predictions. Most of them are questionable since they ignore the physicochemical parameters that seem to control the erosion process. In order to study the scour resistance of intact or remolded cohesive soils, a rotating cylinder technique allowing for the control of essential parameters was recently improved by the authors. Intact or remolded samples can be used. The water quality is controlled in order to respect thein situphysicochemical conditions. The shear stress transmitted by water to the clay surface is directly and accurately derived. The dry weight of eroded material per unit time and unit area, for given conditions, is also directly and adequately measured. The influence of water quality, or of any treatment of the clay, may be quantitatively analyzed.Key words: erosion, scour, clay, rotating cylinder, viscometry, physical chemistry, river channels.

ISSN:0008-3674    

DOI:10.1139/t86-010

出版商:NRC Research Press    

年代:1986

数据来源: NRC