摘要:

The distribution of avalanche runout varies in space and time for individual avalanche paths and from mountain range to mountain range. In this paper, such variations are considered based on the assumption (supported by data worldwide) that the spatial distribution of extreme avalanche runout follows a Gumbel distribution and that the arrival rate of avalanches can be modelled as a Poisson process. The input required is a set of extreme avalanche runout distances for the mountain range and a knowledge of avalanche frequency at the beginning of the runout zone for the path in question. Such information allows theoretical estimation of the effective return period as a function of position, which is very important in zoning applications. In addition, general expressions are derived to relate Gumbel parameters for different mountain ranges to a frequency index to explore general frequency implications from one mountain range to another. The estimated Gumbel parameters imply consistent relationships for expected avalanche frequency and terrain from one mountain range to another.Key words: snow avalanches, runout distances, return period, frequency, terrain.

ISSN:0008-3674    

DOI:10.1139/t99-081

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

An analytical solution is developed to determine the active lateral earth pressure distribution on a retaining structure when it consists of a cohesive backfill (internal friction angle φ > 0, cohesionc> 0) with an inclined ground surface. The solution derived encompasses both Bell's equation (for cohesive or cohesionless backfill with a horizontal ground surface) and Rankine's solution (for cohesionless backfill with an inclined ground surface). The orientation of the failure surface is also determined. Results indicate that, unlike the soil-wall scenarios of Bell and Rankine where the failure planes are parallel with a fixed orientation independent of the overburden pressure, for sloping cohesive backfill (φ > 0,c> 0) the slope of the failure surface is a function of the overburden pressure and becomes shallower with depth, thus forming a curvilinear failure surface. The solution developed can also be used to check the sustainability of a slope. The analytical solution can be programmed conveniently in a computer.Key words: retaining structure, active earth pressure, cohesive backfill.

ISSN:0008-3674    

DOI:10.1139/t99-091

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Direct measurements of the initial shear strength and yielding anisotropy of a dense,K0-consolidated silt are described and interpreted within a bounding-surface framework. The experiments were performed using the Imperial College large hollow cylinder apparatus, in which samples were sheared undrained with a range of orientations, &agr;, of the major principal stress, &sgr;1, following initialK0consolidation. The interpretation is aided by data from oedometer and triaxial stress path tests. Strongly anisotropic stiffness, yielding, undrained strength, and mobilized angle of shearing resistance, φ', characteristics are revealed. The effects of drained and undrained stress changes applied to the samples afterK0consolidation are also described.Key words: anisotropy, hollow cylinder,K0consolidation, silt, bounding surface.

ISSN:0008-3674    

DOI:10.1139/t99-094

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Acid mine drainage can be curbed or reduced significantly by covering tailings sites with an oxygen barrier. In this study, the ability of pulp and paper residues, more specifically deinking residues, to function as such a barrier was investigated. Field data from two sites show that O2diffusion through the barriers can be greatly reduced. To better understand how oxygen migrates through deinking residues and to develop prediction tools for future design with deinking residues, one-dimensional effective diffusion coefficients (De) were determined by fitting laboratory experimental curves (O2concentration versus time data) to curves obtained from computer simulations. The results obtained confirmed the behaviour observed in soil covers: the effective diffusion coefficients are highly dependent on the degree of saturation (Sr) of the compacted material. TheDevalues obtained in this study compare well with those published in the literature for several materials compacted at similar Sr. TheDevalues varied from 8.3 × 10-9m2/s (Sr approximately 91%) to 9.7 × 10-7m2/s (Sr approximately 76%). The O2consumption by biodegradation appears to be an important factor in the reduction of the O2flux that can reach the bottom of the barrier.Key words: oxygen diffusion, pulp and paper residues, barrier, acid mine drainag

ISSN:0008-3674    

DOI:10.1139/t99-093

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

This paper reports the results of a geotechnical investigation and a 3 year monitoring program of clay deposits in Montréal Island, on which are founded five typical residential buildings. The sites were provided with foundation wall elevation pins, ground movement plates, deep settlement points, piezometers and shallow water level gauges, aluminium tubes for the measurement of volumetric weights and water contents, and irrigation systems. Data recorded show that for the relatively dry summer of 1991 ground and foundation settlements were more pronounced on the nonirrigated sites.Key words: shallow foundations, clay deposits, performance, urban environment, monitoring

ISSN:0008-3674    

DOI:10.1139/t99-082

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

This paper describes large-size direct shear tests on soil-geotextile interfaces. Medium-grained, uniform sand and three varieties of woven and nonwoven geotextiles manufactured with different techniques are utilized to investigate the soil-geotextile interface friction coefficient (f*). Tests were carried out using an apparatus specifically designed for interface testing, and results were compared with those obtained from the conventional direct shear equipment. The results obtained from this study indicated that the determination of peak interface behaviour was not a trivial matter, as the results were significantly affected by the boundary and testing conditions of the testing apparatus. The residual interface behaviour was investigated by multiple reversal direct shear tests. Since the use of multiple reversal direct shear tests on the proposed apparatus can impose a high degree of shear displacement and stress uniformity on the soil-geotextile interface, a more reliable definition of the residual interface friction can be obtained. The results indicate that woven-nonwoven geotextile interfaces exhibit a significant postpeak strength loss after a number of shear cycles. In the case of woven geotextiles, this is attributed to the opening up of the filaments associated with the physical damage caused during shear, whereas for nonwoven geotextiles it is due to the pulling out or tearing of filaments.Key words: geotextile, direct shear test, interface friction coefficient, peak shear strength, residual shear strength.

ISSN:0008-3674    

DOI:10.1139/t99-124

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

This paper describes an experimental study on the fracture toughnessKIICof pure frozen soil and the behaviour of the interface between frozen soil and concrete. A four-point bending device is used in the test. Experimental results indicate that water content and temperature are the main factors affecting fracture toughness. Within the range of the experiment, loading rate has a very slight effect on fracture toughness. Some formulae are suggested to evaluate the fracture behaviour of frozen soil.Key words: frozen soil, fracture mechanics, fracture toughness, interface.

ISSN:0008-3674    

DOI:10.1139/t99-059

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Sampling using horizontal directional drilling allows the collection of soil samples from suspected zones located beneath structures and other surface-subsurface obstacles. However, current horizontal sampling techniques are time consuming and thus expensive. This paper describes the design and testing of a new multiple-port sampler for collection of soil samples from directionally drilled boreholes. The device uses a new methodology for horizontal sampling to improve cost-effectiveness and sample quality.Key words: horizontal directional drilling, horizontal wells, design, remediation, site characterization, sampling.

ISSN:0008-3674    

DOI:10.1139/t99-097

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

As our understanding of soils has been steadily improving, the characteristics of its variability can now be highlighted. This has practically changed our geotechnicalmodusoperandifrom strictly deterministic models to semiprobabilistic or even strictly probabilistic models. The latter are still to be regarded as experimental and cannot, for the time being, be used routinely in practical working applications. However, the ongoing, continued research and study of these methods combine to develop their worth and bring out any drawbacks. This paper proposes a possible application of probabilistic methods to the study of shallow foundations reliability with respect to their bearing capacity. The study concerns a foundation on a soil characterized by effective cohesionc' and friction angle φ', considering possible values of correlation coefficients between them and taking into account the effects of vertical fluctuation scale. The results show that higher reliability indexes are found when correlations betweenc' and φ' are negative and when the fluctuation scale has a minimum value.Key words: reliability, bearing capacity, shallow foundations, friction angle, cohesion.

ISSN:0008-3674    

DOI:10.1139/t99-096

出版商:NRC Research Press    

年代:2000

数据来源: NRC

ISSN:0008-3674    

DOI:10.1139/t99-102

出版商:NRC Research Press    

年代:2000

数据来源: NRC