摘要:

The modelling of flow through saturated/unsaturated soils has become routine in geotechnical and geo-environmental engineering. The analysis requires that the coefficient of permeability for an unsaturated soil be defined. The coefficient of permeability can be estimated based on currently available procedures. However, each procedure has limitations and consequently cares should be taken in the selection of a proper procedure. The coefficient of permeability of asaturatedsoil is a function of void ratio. The coefficient of permeability of anunsaturatedsoil of constant volume, is a function of the degree of saturation. However, soil is deformable and both the degree of saturation and the void-ratio influence the coefficient of permeability of a compressible, unsaturated soil. In this paper, the literature pertaining to the coefficient of permeability function for anunsaturatedsoil of constant volume and the coefficient of permeability for a deformablesaturatedsoil are reviewed. A new coefficient of permeability function for a deformableunsaturatedporous medium is then developed. A series of triaxial permeameter tests on unsaturated silty sand are described and the results from the experimental program are analyzed using the general form of the newly developed permeability function. The results show good agreement between the experimental data and the proposed model for a deformable unsaturated porous medium.Key words: unsaturated soil, coefficient of permeability, permeability function, soil-water characteristic curve, triaxial permeameter, deformable porous medium.

ISSN:0008-3674    

DOI:10.1139/t98-010

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The development of a specially designed triaxial permeameter for the measurement of the coefficient of permeability of deformable unsaturated soils is presented in this paper. The triaxial permeameter makes it possible to directly measure the coefficient of permeability at various combinations of net normal stresses and matric suction values. The volume change of the soil specimen during the permeability measurement can also be monitored. The performance of the permeameter is demonstrated for a group of tests conducted on slurried specimens of a silty sand.Key words: unsaturated soil, coefficient of permeability, triaxial permeameter, volume change.

ISSN:0008-3674    

DOI:10.1139/t98-011

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

An extensive program of centrifuge tests was undertaken to study the effect of slopes onP-Ycurves in dry sand. The paper concerns the method developed in a previous series of centrifuge tests to experimentally determineP-Ycurves. Bending-moment curves are fitted by local quintic spline functions through a crossed validation method and then differentiatedtwice. These experimentalP-Ycurves are validated by back analysis. The program of tests on piles near slopes is given. It includes studies of the effect of distance to the slope, slope angle, and soil properties. Sample preparation method, model piles, and the lateral-loading device are described. Deflection versus load curves, bending-moment curves, and derivedP-Ycurves for piles close to slopes are compared to horizontal-ground response. The coefficients that can apply to theP-Yreaction curves of the reference piles (a single pile in horizontal ground) are proposed for use in practice.Key words: pile, slope effets, models, centrifuge, bending moment,P-Yreaction curves.

ISSN:0008-3674    

DOI:10.1139/t98-016

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Soil liquefaction is a major concern for structures constructed with or on sandy soils. This paper describes the phenomena of soil liquefaction, reviews suitable definitions, and provides an update on methods to evaluate cyclic liquefaction using the cone penetration test (CPT). A method is described to estimate grain characteristics directly from the CPT and to incorporate this into one of the methods for evaluating resistance to cyclic loading. A worked example is also provided, illustrating how the continuous nature of the CPT can provide a good evaluation of cyclic liquefaction potential, on an overall profile basis. This paper forms part of the final submission by the authors to the proceedings of the 1996 National Center for Earthquake Engineering Research workshop on evaluation of liquefaction resistance of soils.Key words: cyclic liquefaction, sandy soils, cone penetration test

ISSN:0008-3674    

DOI:10.1139/t98-017

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The Al Hoceima region presents several instability features. Some zones remain relatively stable, but others are subject to signs of instability factors or to active slides. The aim of this study is to establish the different instabilities mapping and to define, in hierarchic order, their potential risk. This work was conducted by selecting all factors influencing stability : geological, hydrogeological, and geotechnical parameters, thus we develop a zoning procedure that permits us to quantify thepotential hazards.This study shows that major potential hazards zones are essentially caused by the presence of weak cohesive layers (clay) interbedded within other, mostly stronger, formations in addition to the steep slopes, the intense fracturing, and the presence of a high piezometric surface.Finally, our results are proved by comparison to others obtained from the ZERMOS and P.E.R. cartography modes.Key words: Rif-Maroc, lithologie, évaluation, instabilité, cartographi

ISSN:0008-3674    

DOI:10.1139/t98-019

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

A fine-grained nonplastic till was compacted in the laboratory in three types of rigid wall permeameters, having a volume of 0.4, 1.5, and 25 dm3, respectively, and, was thereafter exposed to a maximum of 18 freezing and thawing cycles. The permeabilities in the vertical direction of saturated samples were measured in unfrozen soil as well as in thawed soil. The results show that the permeabilities changed after freezing and thawing. The magnitude of the changes in this study were in the range 0.02-10 times after freeze/thaw compared with the unfrozen soil. Soil exhibited volume changes subsequent to freeze/thaw. The volume typically decreased for an initially loose soil and increased for a dense soil. Independent of whether the initial soil structure was loose or dense, a constant "residual" void ratio,eres, was obtained after 1-3 cycles. For the soil investigated, the residual void ratio ranged from 0.31 to 0.40.Key words: till, fine-grained, non plastic, permeability, freeze/thaw, residual void ratio.

ISSN:0008-3674    

DOI:10.1139/t98-015

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The excitation of specimens in multiple modes enhances the characterization of granular materials. The purpose of this paper is to present the equipment modification and test procedure and data reduction for flexural excitation in a standard torsional-resonant column device. Typical results for dry and wet sand specimens are also presented. A salient advantage of the modified device is that it permits testing shear stiffness (torsional excitation) and longitudinal stiffness (flexural excitation) at frequencies which are relevant to high-resolution seismics and near-surface studies (approx. 50-200 Hz). High attenuation in flexural mode is measured in saturated and partially saturated specimens; local flow is suspected as a prevailing loss mechanism. Velocity and damping ratios are complementary indicators of saturation conditions prevailing in the specimen.Key words: mechanical waves, resonant column, velocity, attenuation, sands, modal testing.

ISSN:0008-3674    

DOI:10.1139/t98-012

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

An analytical model of electroosmosis-enhanced preloading consolidation via vertical drains is developed for the design of the combined preloading and electroosmotic consolidation of clay soils. The excess pore pressure and average degree of consolidation are computed and examined for the effects of surcharge load, electric field intensity, treatment time, spatial configuration of electrodes, drainage path, and soil properties. The model is evaluated using the results of a well-known electroosmotic consolidation field test reported in the literature.Key words: consolidation, electroosmosis, surcharge preloading, vertical drains, soil improvement, soft clays.

ISSN:0008-3674    

DOI:10.1139/t98-018

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

It has been reported that conventional methods of analysis could not adequately describe all aspects of the behaviour of a geotextile-reinforced test embankment constructed to failure on a soft clayey silt with some organics at Sackville, New Brunswick (Canada). This paper presents the results of an analysis of the Sackville embankment using a fully coupled elasto-viscoplastic constitutive model with an elliptical cap yield surface. The importance of modelling the rate sensitive characteristics of the Sackville foundation soil is demonstrated. A comparison of calculated and measured behaviour of the Sackville test embankment demonstrates that the single elasto-viscoplastic yield surface model adequately described much of the measured time-dependent behaviour of the Sackville test embankment including post construction increases in pore pressure, deformation and reinforcement strain.Key words: Embankment; soft soil; geosynthetic; reinforcement; analysis; field case, viscoplasticity

ISSN:0008-3674    

DOI:10.1139/t98-021

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The influence of grain crushing under high stress levels is introduced in the elasto-plastic constitutive law (Hujeux'smodel) using additional variables that change with the physical and mechanical properties of the grains. These variables aredefined as functions of the amount of dissipated plastic work, which is proposed as a parameter for describing the materialyield. The results of computer simulations along oedometric and triaxial paths indicate a very good agreement between theexperimental curves and the numerical solutions. The proposed modifications are therefore validated.Key words: correlation, grain crushing, constitutive law, modelization, plastic work.[Journal translation]

ISSN:0008-3674    

DOI:10.1139/t97-083

出版商:NRC Research Press    

年代:1998

数据来源: NRC