摘要:

Anin situdensification probe that employs the novel technique of simultaneous vibration and dewatering has been developed by Phoenix Engineering Ltd. to compact deep, loose, granular soils. It is believed that pumping water out of the soil during the densification process offers improved densification capability over systems operating with vibration alone. An independent study was undertaken by theIn-SituTesting Group at the University of British Columbia to evaluate the performance of the Phoenix system.A field testing programme was conducted at a site in Vancouver where hydraulic sand fill overlies a natural silt and then medium Fraser River sand. Characterization of the site and evaluation of the densification treatment process were achieved usingin situtests. Changes to soil parameters due to densification treatment were examined, taking into account the modification of stresses brought about by the vibro-drainage process. The study investigated the degree of densification achieved, the value of concurrent drainage, the zone of influence of a single compaction probe, and group effects. The study also compares the performance of the Phoenix machine with that of other vibrocompaction equipment.Key words:in situ, densification, soils, granular, probe, vibratory, drainage, compaction, R&D.

ISSN:0008-3674    

DOI:10.1139/t90-020

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

An experimental investigation of diffusive transport of a nonreactive solute (chloride) in saturated, intact Queenston Shale is described. Laboratory tests were performed by placing distilled water in contact with samples of shale having a high initial concentration of chloride in their pore water. Chloride was then permitted to diffuse out of the shale and into the distilled water reservoir for a period of up to 65 days. At the end of each test, the shale sample was sectioned to determine the variation in chloride pore-water concentration with depth through the sample. Fickian diffusion theory was then used to deduce the diffusion coefficient (D). The experimental diffusion coefficient for chloride at a temperature of 22 ± 1 °C ranged from 1.4 × 10−6to 1.6 × 10−6 cm2/s, which corresponds to a tortuosity (τ) ranging from 0.095 to 0.108. Based on pore size measurements and consideration of the ionic diameter of hydrated chloride, the "effective porosity" available for chloride diffusion is estimated to be greater than 75% of the total porosity calculated from the moisture content of the shale.Key words: diffusion, chloride, rock matrix, Queenston Shale, laboratory study.

ISSN:0008-3674    

DOI:10.1139/t90-021

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Mars Island, a man-made spray ice island, was constructed in January and February 1986, and was used as a drill platform for petroleum exploration in the Alaskan Beaufort Sea. A series of pressuremeter creep tests was run in the spray ice of Mars Island in March 1986. Individual constant-pressure tests lasted up to 5 days.It is possible to compare the creep behaviour of the spray ice as interpreted from the pressuremeter tests with the creep behaviour interpreted from the island settlement records. These comparisons are made for both primary and secondary creep on the basis of conventional power law theory. The following points are of particular interest: (1) The primary creep data can be characterized using a simple power law. The exponent of time for spray ice is similar to that for solid polycrystalline ice. The exponent of stress is different for the two kinds of ice. (2) Pressuremeter tests gave secondary creep information that correlates well with the steady-rate settlement of the island. (3) Research into the possible range of primary creep parameters for spray ice is required, given that primary creep accounted for a large portion of the settlement of Mars Island. In particular, the effect of ice density on creep rates mast be resolved. (4) The pressuremeter is potentially an excellent design control device during the manufacture of future spray ice islands. The results of constant-pressure tests of 1–2 days duration could be used to check the design assumptions pertaining to the expected consolidation of the ice mass with time.Key words: spray ice, creep, artificial islands, pressuremeter, settlement.

ISSN:0008-3674    

DOI:10.1139/t90-022

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

A simple nonlinear failure criterion is proposed for geologic materials exhibiting time-dependent softening. It is expressed in terms of maximum and minimum principal stresses, uniaxial compression strength, and three strength parameters. These strength parameters can be easily determined from conventional strength tests such as the triaxial compression test. The application of the proposed failure criterion to experimental data taken from the literature shows that there is excellent agreement.The proposed failure criterion is used to describe the effect of softening observed in materials such as overconsolidated clays and soft rocks. The effect of softening can be represented in this failure criterion through a time-dependent reduction in the strength parameters. The variation in shear strength during softening is embraced from the initial strength to the fully softened condition.Key words: failure criterion, softening, time-dependent strength reduction.

ISSN:0008-3674    

DOI:10.1139/t90-023

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Laboratory freezing tests were performed on a saturated clayey silt at various pore-water salinities and applied pressures to establish the relationships between pore-water salinity, overburden, and the amount of moisture transfer during freezing near thermal steady state conditions. The experimental data confirmed that the concept of segregation potential established for salt-free soils can be extended to saline soils. The segregation potential at the onset of the final ice lens in step-freezing tests (or near thermal steady state) should be related to the average salinity of the frozen fringe associated with the final ice lens. This pore-water salinity is different from the initial pore-water salinity as a result of solute exclusion at the ice lenses causing an enrichment as freezing proceeds. Unfortunately, it is very difficult to determine the average salinity in the frozen fringe owing to its small size. Instead, it is proposed to use the initial water salinity to develop the constitutive equations in freezing saline soils. A procedure for frost heave predictions in the field is outlined.Key words: freezing tests, clayey silt, saline water, frost heave.

ISSN:0008-3674    

DOI:10.1139/t90-024

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Soil–bentonite mixes are frequently used as impervious liners for waste disposal projects. These mixes can be controlled in the field by local permeability tests or by their global performance. The accuracy ofin situlocal tests is found to be limited after the thermal dilation of infiltrometers is considered. A method is developed to analyze the total leakage rate and to detect hydraulically induced damage and deterioration of hydraulic defects. Finally, the use of coupled hydrometer tests or X-ray diffraction tests is recommended to determine local values of bentonite content and to verify whether thein situvariability in bentonite content is similar to that provided for in the design.Key words: impervious liner, soil, bentonite, permeability, field control.

ISSN:0008-3674    

DOI:10.1139/t90-025

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Nonlinear finite element analyses were performed on a nonreinforced embankment and a polymeric reinforced embankment, with 1:1 side slopes, constructed on competent foundations. The nonreinforced and reinforced embankment analyses are compared to examine the influence of polymeric reinforcement within a soil slope. It is shown that significant reductions in the shearing, horizontal, and vertical strains within the slope occur because of the presence of the reinforcement.The finite element analysis of the reinforced embankment construction gives the magnitude and distribution of load within the reinforcement. For all embankment heights, the maximum reinforcement load did not occur in the lowest reinforcing layer but in the reinforcing layer placed 0.4Habove the foundation, whereHis the height of the slope. The displacement patterns and surface deformations of the nonreinforced and reinforced slopes are compared to show the marked reduction in slope movements resulting from the presence of the reinforcement.The location and shape of potential shear surfaces within the homogeneous reinforced slope are examined. The position of the maximum load in each reinforcing layer within the reinforced slope indicates that, for the example studied, a circular-shaped slip surface represents a probable failure mechanism within the slope.Key words: soil reinforcement, geotextiles, finite element, slope stability, geogrids, limit equilibrium, reinforced slope.

ISSN:0008-3674    

DOI:10.1139/t90-026

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

A long-term permafrost and terrain research and monitoring program along the 869 km buried oil pipeline between Norman Wells, Northwest Territories, and Zama, Alberta, has been undertaken by the Geological Survey of Canada, in cooperation with the Department of Indian and Northern Affairs Canada. The two main program components are (1) the detailed quantification of changes in the geothermal regime and geomorphic conditions at instrumented monitoring sites and (2) general observations of terrain conditions and performance along the pipeline route. Pipeline operation commenced in April 1985. Observations during the first 2.5 years of pipeline operation indicate that, as expected, the pipe thermal regime and ground thermal regime have not yet stabilized in response to construction and operation. Warming trends in both mean annual pipe temperature and mean annual right-of-way ground temperature have occurred. Surface settlement in permafrost terrain is ongoing in the pipe trench as well as on the remainder of the right-of-way. Surface erosion has occurred, particularly at stream crossings and on low-angle slopes lacking erosion control structures.Key words: pipeline, permafrost, thermal regime, thaw settlement, surface erosion, instrumentation, Norman Wells, Mackenzie Valley, Canada.

ISSN:0008-3674    

DOI:10.1139/t90-027

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Two explicit formulae for calculating the time factor for a given average degree of a combined vertical and radial consolidation have been successfully derived by manipulating some approximate and explicit forms of time factor for the vertical consolidation part and are presented in this technical note. Since these formulae have different accuracies and are meant to be complementary to each other, the regions where each is best suited have also been established.Key words: vertical consolidation, radial consolidation, sand drain, time factor, free strain, equal strain.

ISSN:0008-3674    

DOI:10.1139/t90-028

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Large-diameter steel pipe piles were driven as part of the foundations for the Alex Fraser Bridge near Vancouver, British Columbia. The piles penetrated through a normally consolidated marine clayey silt. As part of the geotechnical studies a multipoint piezometer was installed close to the pile group. A cone penetration test with pore pressure measurements (CPTU) was performed adjacent to one of the piles shortly after driving. During the CPTU through the clayey silt deposit, dissipation tests were performed to evaluate the pore pressures around the nearby pile. The CPTU results are compared with the pore pressures recorded at the multipoint piezometer, allowing for differences in radial distance from the piles. Excellent agreement was obtained between the CPTU and multipoint piezometer data, both showing large excess pore pressures around the piles. The CPTU dissipation data were also analyzed to evaluate the time required for dissipation of excess pore pressures around the piles. The upper half of the clayey silt deposit was inter bedded with thin sand and silt layers. The CPTU data showed that the thin sand layers were sufficiently large in extent to allow rapid dissipation of the pore pressures due to cone penetration but were not of sufficient extent to allow dissipation of the excess pore pressures from the much larger diameter piles.Key words:in situ, piles, pore pressures, CPT.

ISSN:0008-3674    

DOI:10.1139/t90-029

出版商:NRC Research Press    

年代:1990

数据来源: NRC