摘要:

A laboratory study has been conducted to investigate the dynamic behaviour of Champlain Sea clay from two locations in the Ottawa River valley region. The test program includes cyclic triaxial tests and resonant-column tests. The soil samples were consolidated at a range of pressures before the dynamic shear in order to cover the dynamic behaviour under both the overconsolidated and the normally consolidated states. An energy concept is introduced to interpret the test results. Mathematical relationships have been established for describing the various aspects of dynamic behaviour. These aspects include excess pore pressure, dynamic strength, dynamic shear modulus, and plastic strain. The study shows that the energy concept provides a promising way to analyze dynamic soil behaviour.Key words: energy, dynamic behaviour, clay, cyclic test, earthquake, excess pore pressure, shear modulus, strength.

ISSN:0008-3674    

DOI:10.1139/t92-011

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

Anchor forces, ground temperatures, and piezometric pressures were measured at a retaining wall in northwestern Ontario over a period of 2 years. The anchor forces were measured with strain gauges attached in pairs directly to the anchor rods. This method appeared practical in the field for time periods of less than 2 years as long as the strain gauges were carefully protected against moisture. The anchor forces increased from an average of 5 kN initially up to values of 50 kN during the winter periods and dropped during the summer periods back to the same values measured initially. The anchor forces were largely independent of pore-water pressure variations behind the wall. Rapid drawdown conditions, however, which were experienced during the second summer, were reflected in a load increase that was equivalent to the associated unloading effect in front of the wall. The pore-water pressures behind the wall were not noticeably affected by rapid drawdown, possibly due to the restraining effect of the anchors and the high rigidity of the low sheet pile wall. Ground temperatures at or below the groundwater table never dropped below 0 °C thus restricting the depth of frost penetration.Key words: anchor loads, freezing pressure, retaining walls, pore-water pressures, ground temperatures, field measurements.

ISSN:0008-3674    

DOI:10.1139/t92-012

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

Nine case records of slope failure during the Saguenay earthquake are documented, including five in granular embankments, two in natural slopes in granular material with small embankments at the top, and two in sensitive clay. The bedrock motion during the earthquake is well documented; each failure is related to the most probable bedrock motion at the site (0.05 to 0.15 g). For the seven cases of failure in granular slopes, the reserve of stability under static conditions was relatively low before the earthquake, and only a small additional undrained loading was necessary to develop failure. Two slope failures occurred in extrasensitive clay deposits containing no visible lens or layer of silt or sand. Silty or sandy materials have been identified only at the clay–till contact. It is believed that in at least one of the sites a portion of the failure surface developed at the inclined clay–till contact.Key words: slope failure, earthquake, sensitive clays, embankment fill, stability, granular material.

ISSN:0008-3674    

DOI:10.1139/t92-013

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

This study deals with the freeze and thaw effects on the mechanical behaviour of the clayey subgrades exposed by cuts for the placement of road foundations. Twelve cut sites have been analysed in cooperation with the ministère des Transports du Québec. As damages were observed after the first winter on some of the sites, whereas none were apparent on other sites, it was possible to define the factors that may lead to such damages. In particular, the field study confirms the laboratory results showing that criteria based on liquidity index are sufficient to characterize the change of mechanical behaviour of the clayey soils subjected to one freeze–thaw cycle.Key words: clay, liquidity index, freeze-thaw, bearing capacity of roads, heaving, cut. [Translated by the Journal]

ISSN:0008-3674    

DOI:10.1139/t92-014

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

Tests in the field and full-scale experience with arctic structures show that the crushing of ice is accompanied by large fluctuations in load. Field experiments show that, in addition to variations of load in time, significant spatial variations across the contact surface also occur. The deformation is observed to take place in a thin layer of damaged ice, which appears near the structure or indenter surface. It is important to model the deformation and strength of ice in this zone. Various aspects of modelling are discussed in the paper, in particular, measures of damage and the relation to the deformation of ice. The relevance of various components of deformation (elastic, viscous, delayed elastic) is outlined, and two mathematical formulations for the deformation are discussed. The behaviour was investigated by a series of tests at constant strain rate as well as tests in which the strain response to stress of damaged and undamaged ice was measured. The creep rate in damaged ice is shown to be significantly enhanced, even for short-term loading. Comparisons of theory and experiment are given for constant strain-rate tests. The models have been calibrated to the experimental data described in the paper. It is a matter for future research to generalize the models to all damage levels and stress states.Key words: creep, damage, deformation, ice, microcracking, visco-elasticity.

ISSN:0008-3674    

DOI:10.1139/t92-015

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

Although the Fraser River delta front supports coastal structures including ports, a lighthouse, jetties, submarine power cables, and sewage pipelines, the stability of the delta front is little understood. Five large-scale mass-wasting events at the mouth of the Main Channel near Sand Heads have been detected by comparing successive bathymetric surveys conducted by Public Works Canada between 1970 and 1986. These events can involve the downslope movement of more than 1 × 106 m3of silty sand and the landward retrogression of the delta-front crest of up to 350 m or more. Morphologic and sedimentologic evidence suggests that these events are slope failures which result from the liquefaction of silty sand. Rapid deposition at the river mouth is likely a prerequisite for failure, although interstitial gas, tidal currents, waves, and earthquakes also may contribute to failure. These results have important implications for the foundation stability of the Sand Heads Lighthouse and future coastal structures in the area.Key words: bathymetry, mass wasting, liquefaction, hazard, Fraser River delta.

ISSN:0008-3674    

DOI:10.1139/t92-016

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

The value of the secant shear modulus (G) of sand measured in cyclic tests reduces as the amplitude of cycling increases. As a first approximation, it is assumed that the curve joining the extreme points of stress–strain (τ–γ) loops of different amplitudes (a so-called "backbone curve") is hyperbolic. The shear strength (τmax) of sand is directly proportional to the mean effective confining pressure (p′), whereas the maximum shear modulus (G0) is proportional to (p′)n, withnbeing between 0.4 and 0.5. Based on these assumptions, it is shown that at the same shear strain level, differentG/G0values should be expected at differentp′ values. One of the features of a hyperbolic τ–γ curve is that there is a unique linear relationship betweenG/G0and normalized shear stress level (defined as τ/τmax), independent ofp′. Therefore, considering the normalized shear stress level rather than the shear strain level may be a more logical and unifying way of examining the variation inG/G0.Key words: shear modulus, hyperbolic stress–strain curve, pressuremeter test.

ISSN:0008-3674    

DOI:10.1139/t92-017

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

Different reasonable probability distributions can be assigned for the coefficient of consolidation,C. But if no more than the first few probability moments of the excess pore pressure and of the degree of consolidation which are functions ofCare of concern, it is advantageous to use a simpler, distribution-free method for matching probability moments ofC. In this note, the method of discretization of probability is used to analyze one-dimensional consolidation. The solutions, influenced by the probability moments of third, fourth, and fifth order ofC, are presented.Key words: probability, discretization, coefficient of consolidation, excess pore pressure, degree of consolidation, moments, random variable.

ISSN:0008-3674    

DOI:10.1139/t92-018

出版商:NRC Research Press    

年代:1992

数据来源: NRC

ISSN:0008-3674    

DOI:10.1139/t92-019

出版商:NRC Research Press    

年代:1992

数据来源: NRC

ISSN:0008-3674    

DOI:10.1139/t92-020

出版商:NRC Research Press    

年代:1992

数据来源: NRC