摘要:

The effect of stress path on the steady state line of a liquefiable sand is investigated. Results from undrained triaxial compression and extension tests on water-deposited sands show that the steady state line of a given sand, though unique in the effective stress space, is not so in the void ratio – effective stress space. The sand is contractive over a much larger range of void ratios in extension than in compression. While a single steady state line emerges for compression loading, extension loading yields several lines, each characteristic to a given deposition void ratio. All these extension lines lie to the left of the compression line in void ratio – effective stress space. Thus at a given void ratio, steady state strength is smaller in extension than in compression, the difference increasing as the sand becomes looser. The implications of the results are discussed in relation to practical design.Key words: sand, liquefaction, steady state, stress path.

ISSN:0008-3674    

DOI:10.1139/t90-001

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

When a dense granular material with a viscoplastic matrix, such as ice, is submitted to uniaxial or triaxial compression, it is considered that one portion of its observed strength is due to the internal confinement resulting from tensile stresses generated in the matrix when it tends to oppose the dilation. Recently, a conceptual model of compression strength behaviour of such dilatant materials was developed by the senior author. This paper presents the model and describes an experimental study intended to check its validity. For this purpose, a series of triaxial compression tests on both frozen and unfrozen sand at carefully controlled densities was performed. The test results give a clear support to the theoretical predictions of the contribution of dilatancy hardening to the strength of a dense frozen sand.Key words: frozen sand, compression strength, triaxial compression tests, pore ice, cavitation, dilatancy hardening, conceptual model.

ISSN:0008-3674    

DOI:10.1139/t90-002

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The lateral soil pressures, bending moments, pile displacements at ground surface, and bearing capacity of instrumented vertical single flexible model piles in homogeneous loose sand and soft clay under central inclined loads have been investigated. The results of these load tests are compared with theoretical estimates based on the concept of an effective embedment depth of equivalent rigid piles. Reasonable agreement has been found between the observed and predicted behaviour of flexible piles. The analyses are also compared with the results of some field case records.Key words: bending moments, clay, displacements, inclined loads, instrumentation, lateral soil pressure, model test, pile, sand.

ISSN:0008-3674    

DOI:10.1139/t90-003

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

A systematic analysis of the undrained stress–strain behavior of clay under irregular cyclic simple shear loading is presented. Seven specimens of an offshore clay consolidated to overconsolidation ratios of 1, 2, and 4 were subjected to different combinations of variable and nonsymmetric cyclic amplitudes using the Norwegian Geotechnical Institute (NGI) direct simple shear device. The test results show that (1) the behavior under such loads is influenced by several different factors, (2) among these factors the loading history and cyclic stiffness degradation are predominant, and (3) the irregular cyclic loading stress–strain curves can be described quite well by five rules that incorporate only these two factors. Four out of these five rules are the extensions of two original and two extended Masing rules to the behaviour of cyclically degrading clay. The fifth rule is new. The effects of the S-shaping of the stress–strain curves and the rate of loading on the applicability of the rules are also discussed. The stress–strain curves are presented in the normalized form with respect to the vertical effective consolidation stress. In this form they show quantitatively the same trends, indicating that such normalization is applicable to irregular cyclic loading.Key words: clay, earthquake loading, laboratory test, ocean soil, overconsolidation, simple shear test, soil dynamics, strain rate effect, repeated loading.

ISSN:0008-3674    

DOI:10.1139/t90-004

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Soil–bentonite mixes are frequently used as impervious blankets in waste disposal projects. Numerous results of laboratory permeability tests are presented for sands containing up to 33% bentonite. These results seem difficult to analyze because different testing methods have been used in which it is not easy to control certain parameters, such as hydration period, degree of saturation, and swelling under low confining pressure. Hydraulic conductivity, however, can be obtained by using empirical equations that take into account the bentonite content, porosity, and degree of saturation of the sand alone when tested at its optimum modified Proctor value in a permeameter. This preliminary evaluation helps to select the soil to be tested. Then, the laboratory test results can be used to predict thein situhydraulic performance after due consideration of the variabilities in natural sand and bentonite content.Key words: liner, soil, bentonite, permeability, laboratory, field.

ISSN:0008-3674    

DOI:10.1139/t90-005

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

An investigation was conducted to demonstrate the applicability of cylindrical piezocone and flat piezoblade tests for providing reliable estimates of the coefficient of consolidation in clays. Coefficients of consolidation were calculated from piezocone dissipation tests for different degrees of consolidation using theoretical time factors to provide a comparison with laboratory oedometer tests. Three techniques were developed to calculate the coefficient of consolidation from piezoblade dissipation tests. Results fromin situpore pressure dissipation tests were compared with laboratory oedometer tests performed on undisturbed samples oriented in both the vertical and horizontal directions, to provide reference values ofcvandch. The results of investigations conducted at several clay sites are presented.Key words:in situtests, piezocone, piezoblade, coefficient of consolidation, oedometer test, clays.

ISSN:0008-3674    

DOI:10.1139/t90-006

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

It is hypothesized that a normalized shear stress – strain curve for granular materials can be obtained by accounting fully for the effects of volume change. In this sense, volume change behavior is a factor that controls the shear stress – strain behavior of a granular material. This hypothesis is applied to Rowe's stress-dilatancy theory to include slip, rolling, rearrangement, and crushing strains, and a theoretical normalizing relation is obtained. The relation is demonstrated to be reasonably correct for the published test data utilized in this study. Differing fabrics of a granular material at the same void ratio can be corrected for by the normalizing relation. The hypothesis is also applied to simple shear behavior and an empirical normalizing relation is obtained.On the basis of the success of the normalizing relation, it is suggested that the volume change rate at 4% axial strain may be, in relation to shear behavior, a more appropriate characterizing parameter than void ratio. However, owing to the long-standing use and acceptance of void ratio, the concept of a reference void ratio, determined by specific sample preparation and testing procedures, is introduced as a characterizing parameter for granular materials.Key words: volume change, dilatancy, normalization, fabric, stress, strain, deformation, sand, granular material.

ISSN:0008-3674    

DOI:10.1139/t90-007

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Direct measurement of gas pressure within unsaturated offshore soils is very difficult because the gas occurs in the form of large, discrete bubbles. However, consideration of the soil structure and analysis of a continuum model for the soil suggest two independent sets of limits for the gas bubble pressure. Surface tension effects limit the difference between gas pressure and pore-water pressure, while cavity expansion and contraction considerations limit the difference between gas pressure and mean total stress. If the gas pressure lies within these limits, it should remain almost unaffected by changes to the total stress or pore-water pressure. These suggestions are supported by results from an oedometer test on a reconstituted soil sample containing large bubbles of methane gas.Key words: bubbles, cavity expansion, gas, oedometer tests, offshore geotechnics, pore pressure, surface tension, unsaturated.

ISSN:0008-3674    

DOI:10.1139/t90-008

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The expression for the modulus of compressibility has been established on the basis of rheological experiments in an oedometer that measured the swelling pressure and the vapor pressure of the adsorbed liquid phase of a swelling clay hydrated by water injections under different applied loads.Key words: swelling rheology, soil compressibility, unsaturated swelling clay, oncodynamics, swelling pressure. [Journal translation]

ISSN:0008-3674    

DOI:10.1139/t90-009

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

A 300 m deep monitoring well was completed to the Detroit River Group of formations in Sarnia, Ontario, to evaluate the potential near-surface impacts resulting from previous deep injection of industrial waste. Detailed logging, testing, and sampling were performed to evaluate the vertical distribution of industrial waste and to determine hydraulic conductivity and hydraulic head in the disposal horizon and in the confining formations. Results of hydraulic testing indicate the hydraulic conductivity of the disposal formation is 2 × 10−9to 2 × 10−7 m/s and that of most of the confining shale and limestone formations is less than 1 × 10−10 m/s. Analyses of groundwater samples and results from other studies show that industrial waste, characterized by elevated phenol concentrations, is present in a 10 m horizon in the Lucas dolomite disposal formation at 192 m depth. Waste is also likely present within 2–3 m thick, high-permeability limestone layers at 74 and 123 m depth in the confining units of the Hamilton Group. Because of the generally low vertical hydraulic conductivity of the confining formations, waste in the permeable limestone layers was likely introduced via poorly constructed disposal wells, cavern storage wells, or abandoned oil and gas wells. The hydraulic conductivity and hydraulic head data indicate the high pressures resulting from injection into the disposal formation have dissipated. The head within the zone of residual contamination in the disposal formation is now 8 m below the level of the St. Clair River. The hydraulic data and chemical composition of the injected waste show that the discharges of tarry liquids on the bottom of the St. Clair River in 1984 and 1985 were not caused by upward migration of injected waste.Key words: deep-well disposal, pressurized waste injection, industrial waste, Sarnia.

ISSN:0008-3674    

DOI:10.1139/t90-010

出版商:NRC Research Press    

年代:1990

数据来源: NRC