bluuebunny/crossref_metadata_2025 huggingface dataset:
The Elastic Properties of a Dense Glacial Till Deposit
Authors: Klohn Earle J
Published: April 2011

Dense, heavily preconsolidated glacial till is a relatively incompressible soil that occurs throughout most of Canada. When loaded, it undergoes very small settlement, most of which is elastic. For the average structure, these elastic compressions are too small to be of concern and are usually ignored. However, for some structures they can be critical and their magnitude must be estimated prior to construction. To make the necessary analyses requires knowledge of the elastic properties of the in situ glacial till.This paper presents the results of field and laboratory tests that were made on a dense glacial till deposit to determine its modulus of elasticity, in connection with the design and construction of a 100 ft. high combined earth and concrete dam. In the field, in situ loading tests were made against the walls of a 50 ft. deep test shaft. The modulus of elasticity was computed, using elastic equations applicable to the case of a rigid circular plate pressed against a semi-infinite elastic solid. Moreover, during construction of the project, measurements were made of the elastic rebounds and settlements that occurred under known conditions of unloading and loading. Steinbrenner’s approximate solution for computing settlement due to loads acting on the surface of an elastic layer was then used to compute the apparent modulus of elasticity. In the laboratory, unconfined compression tests and repetitive triaxial tests were made on undisturbed samples. The modulus of elasticity was estimated from the stress-strain relationships obtained.The data presented in the paper indicate that the apparent, in situ modulus of elasticity of the glacial till deposit is very high, being in the order of 150,000 lb./sq. in. Reasonable agreement exists between modulus of elasticity values computed from the in situ plate bearing tests and those computed from observed rebounds and settlements. However, modulus of elasticity values computed from unconfined compression and repetitive triaxial tests in the laboratory are apparently too small, being only a fraction of those values obtained by the field procedures. Sample disturbance is thought to be a major factor affecting laboratory test results.Grain size characteristics, density, natural water content, and strength properties of the glacial till deposit are presented in the paper. These data provide a comprehensive description of the material and permit comparison with glacial till deposits encountered at other areas.
Geotechnical Properties of Three Ontario Clays
Authors: Soderman L G , Quigley R M
Published: April 2011

Presented in this paper are the results of mineralogical and engineering tests performed on clay soils from Ottawa, New Liskeard, and Fort William, Ontario. The mineralogical tests performed include: X-ray diffraction, differential thermal analyses, potassium analyses, glycol retention, carbonate analyses, and pore fluid salinity.The clay minerals identified in the fine fractions of the soils are illite, iron, and aluminum chlorite, and variable amounts of vermiculite and a montmorillonite-like mineral. It is believed that adsorbed aluminum and iron hydroxide cations have altered the vermiculite in some cases to a more swelling clay and in some cases to a nonswelling chlorite.A borehole log for each site is presented along with a summary of routine engineering tests.
Shellmouth Dam Test Fill
Authors: Rivard P J , Kohuska A
Published: April 2011

The Shellmouth Dam on the Assiniboine River is a flood control project now being built by the federal and Manitoba governments. The upper 50 ft. of foundation at the dam site is a medium to highly plastic alluvial clay deposit containing sand layers and lenses. This is underlain by up to 100 ft. of sands and gravels to shale bedrock.This paper describes the design, construction, and instrumentation of a test fill built at the site of the proposed dam, and includes summaries of pore pressure and movement observations, settlement studies, and stability analyses.
Measured Pore Pressures used for the Control of Two-Stage Construction of an Embankment
Authors: DeLory F A , Gass A A , Wong W W
Published: April 2011

Because of soft foundation soil it was necessary to use two-stage construction for a double-track railway embankment varying in height from 21 to 33 feet. Effective stress methods of analysis were used and piezometers were installed in the foundation soil to indicate the pore pressures. Pore pressures measured during the first-stage loading indicated that the second stage could be added to complete the embankment about a year after the first stage. Measurements of pore pressures continued during the second stage loading so that a continuing check on stability could be maintained. The embankment was successfully completed.
The Fabric of Anisotropically Consolidated Sensitive Marine Clay
Authors: Quigley R M , Thompson C D
Published: April 2011

The relationship between soil fabric and the anisotropic consolidation characteristics of a sensitive, highly flocculated marine clay has been studied using x-ray diffraction techniques. Measurements of the clay particle parallelism (fabric) were performed on “undisturbed” and remoulded samples of Leda clay from Ottawa, Canada, in an attempt to determine the influence of sample disturbance on soil fabric and laboratory consolidation test results.The amplitudes of the 10 Å clay peaks of the “undisturbed” natural clays, measured in the major principal plane, increased from about 11 counts/second at low consolidation pressures to about 40 counts/second at 64 tons/sq. ft. This is interpreted as resulting from reorientation of many of the clay platelets into the plane perpendicular to the direction of the consolidation pressure. An abrupt reorientation occurred when the pre-consolidation pressure was exceeded.Remoulding the clay apparently causes a marked breakdown of the interparticle bonds as evidenced by stronger 10 Å peaks and inferred greater particle parallelism at any given consolidation pressure within the range studied. This increase in parallelism is associated with a pronounced reduction in void ratio when compared with the “undisturbed” clay.
Gradation and shear characteristics of four cohesionless soils
Authors: Skermer N. A. , Hillis S. F.
Published: April 2011

Comparison of typical results from drained triaxial tests carried out at confining pressures of 50 and 350 p.s.i. (3.52 and 24.61 kg/cm2) on four cohesionless soils are presented.The effect of gradation at constant relative density is explored, and it is concluded that there is an optimum gradation in terms of both high ultimate strength and high mobilized strength. Uniform coarse gravel is shown to have poor mobilized strength, but at confining pressures high enough to cause particle crushing the improvement in gradation and packing leads to a high ultimate strength, although large axial strains are necessarily induced. The optimum gradation is shown to be close to Fuller's curve for maximum density. The effect of increasing the confining pressure from 50 to 350 p.s.i. (3.52 to 24.61 kg/cm2) leads to a decrease in [Formula: see text] peak of 6 to 10°, but modifications for dilatancy lead to [Formula: see text] parameters that are sensibly constant for any one material.
Soil grinding mill
Authors: Young Fred D.
Published: April 2011

A laboratory soil grinding mill capable of unattended pulverizing and sieving of soils for testing purposes, has been developed by the Materials and Research Branch of the Manitoba Department of Transportation. The cylindrical aluminum mills contain one or more steel rollers which are encased in heavy rubber tubing. A screened door on the mills allows crushed soils particles to escape when they have reached the required sieve size. The mills are driven by two rollers and the ground and sieved soil is collected in a pan beneath them. The mills can be operated unattended.
The Performance of Tied-Back Sheet Piling in Clay
Authors: McRostie G. C. , Burn K. N. , Mitchell R. J.
Published: April 2011

In Ottawa in 1969 a tied-back sheet pile wall was installed to provide temporary support in one side of a 12 m deep excavation through Champlain Sea deposits to shale bedrock. The wall was designed to permit as little yield as possible in order to safeguard the vital operation of an adjacent transformer building.To assess the performance of this structure, measurements of vertical movements of the surface adjacent to the wall, horizontal displacements of the wall, tendon loads and ground-water pressures were made as the excavation progressed.A series of triaxial tests was carried out in the laboratory to determine the form and magnitude of soil deformations under stress changes approximating those derived from the field measurements. Reasonable correlation is obtained when the results of these tests are used to estimate soil displacements in the field situation. The measured tendon loads are compared with those that would be expected using current design methods.
Caractéristiques de compressibilité des argiles du complexe Nottaway – Broadback – Rupert (Baie James)
Authors: Dascal O. , Larocque G. S.
Published: April 2011

The geological and geotechnical investigations carried out in the southeast area of James Bay, have revealed the presence of two types of clay, a proglacial clay of lacustrine origin underlying a postglacial marine clay. The two deposits, which are characterized by a high sensitivity, a low shear strength and a large compressibility, belong to the normally consolidated type of clay from a geological point of view. However, the clays exhibit an important 'quasi preconsolidation' due to the delayed consolidation phenomenon.It is why the establishment of the compression characteristics of these clays has a special importance to predict their behavior under the load of the projected structures.Considering the large number of structures, the extent of the area involved and the access difficulties to the sites, the soil investigations had to be limited to the use of light equipment and the realization of simple tests, the undisturbed sampling being restricted to a few boreholes on each site.The aim of the present paper is to establish some correlations between certain, simple and easy to determine, characteristics of the clays and their compression behavior, to allow settlement evaluation.The results obtained show a very good correlation for these clays between the moisture content (W) or the initial void ratio (eo) and the compression ratio (Cc/1+eo). The analysis carried out has disclosed also that these foundations have a higher compressibility index (Cc) than some clays which had been previously tested, confirming at the same time the linear correlation between these two characteristics (W vs. Cc).The analysis carried out to establish a correlation between Pc/Po and the other physical characteristics was less fruitful probably because of the lack of precision in the evaluation of the effective overburden pressure and numerous other factors involved in the determination of the preconsolidation pressure.
Extrusion of Soft Clay Through a Retaining Wall
Authors: Broms Bengt B. , Bjerke Harald
Published: April 2011

This note describes a slide which occurred in a very soft clay during the construction of an approximately 11 m high cast-in-place reinforced concrete pile wall. Clay squeezed through the openings between three adjacent piles after the clay had been exposed for 1–3 days. An analysis indicates that the slide was caused by excessive overburden pressures at the level of the opening in relation to the low undrained shear strength of the clay.
Instrumentation Around a Warm Oil Pipeline Buried in Permafrost
Authors: Slusarchuk W. A. , Watson G. H. , Speer T. L.
Published: April 2011

A section of an uninsulated pipeline, 90 ft (27.4 m) long and 2 ft (0.61 m) in diameter, was buried in ice-rich permafrost at the Mackenzie Valley Pipe Line Research Limited Inuvik Test Facility. Oil at 160 °F (71 °C) was circulated through the pipe from July 1971 to January 1972 causing a thaw bulb to develop around it.Instrumentation was placed around the pipe to measure temperature, settlement, and pore-water pressure. Temperatures near the ground surface and at depth were measured using thermistors as the sensing element. Settlement was monitored by spiral foot gauges and by taking elevations at the ground surface and on rods welded to the pipe. Pore pressures were measured by gas-operated and Casagrande-type piezometers. Selection, fabrication, and installation of this instrumentation are discussed.
Plasticity Solutions to Stability Problems in Sand
Authors: Graham James
Published: April 2011

Plasticity solutions for failure loadings in sand have reached the stage where confidence can be expressed in the available computational procedures. However, predicted loads often do not agree particularly well with laboratory model results, and significantly over-estimate the ultimate loading on full-scale structures. If care is taken in specifying boundary conditions to conform with observations of model behavior, then good agreement is obtained between theoretical and model results. By using the curvature of the Mohr–Coulomb envelope in the analysis, it has been possible to suggest limits to the magnitude of the scale-effect in sands. These have been compared with corresponding experimental values for passive retaining walls and surface footings. Reasonable trends of behavior have been established.
A design approach for pile foundations in permafrost
Authors: Nixon John F. , McRoberts Edward C
Published: April 2011

A design philosophy for piles in ice and ice-rich permafrost is proposed, whereby the pile settlements over the design life of the structure are retained within acceptable limits.The secondary creep law for ice is reviewed and the relationships between secondary creep rate, stress, and temperature are obtained using existing creep test data from many different sources. An analysis is performed which relates the steady pile settlement rate to the pile shaft stress and the constant ground temperature.A review of the pile load test data available in the literature is carried out, and the results are compared with the theoretical predictions provided by the pile settlement analysis. Reasonable agreement is obtained between prediction and observation, and it is thought that the analysis presented here provides a conservative (safe) bound on the observed results.The analysis is extended to account for the compression of the pile shaft, varying ground temperature profiles, stress readjustment along the pile shaft, and the end bearing capacity of the pile.The analysis presented here provides a rational basis for pile design in permafrost and, in addition, explains many of the phenomena likely to be observed in the behavior of piles under sustained loading.
Consolidation under embankment-type loads
Authors: Shanker N. Babu , Sarma K. S. , Venkataratnam M.
Published: April 2011

Plane strain problems of consolidation (or poro-elasticity) can be solved using the two displacement functions defined by McNamee and Gibson with the help of a repeated integral transformation technique. The problem of a semi-infinite clay layer whose surface is subjected to an embankment-type of normal trapezoidal pressure applied along an infinite strip is treated here. The general loading pattern selected easily degenerates into a rectangular (uniformly distributed) load for which NcNamee and Gibson gave the solutions, to the triangular loads and also to the line loads. Not only the settlements, but also the pore pressures have been evaluated under these types of loads when the surface is either pervious or impervious.The nondimensional solutions presented are useful to highway and embankment engineers. There is also an example of the use of these solutions.
A mechanical model of creep of polycrystalline ice
Authors: Michel Bernard
Published: April 2011

The paper presents a two dimensional mechanical model for the deformation and creep of polycrystalline ice that takes into account the elastic and plastic deformations of each crystal.The model applies to many cases of creep so that the different types of creep curves have been defined during the transitory, permanent and accelerated phases and the corresponding creep laws have been derived. The mechanics of cracking are not analyzed in this paper.The expression for the plastic deformation in this model is based on the principle of multiplication of mobile dislocations and Glen's law for permanent creep. The corresponding mathematical expression for creep without cracking, called α creep, is shown to represent, at the lower limit, the flow of glaciers and is shown to verify a large variety of measured creep curves either in monocrystals or in polycrystalline ice.The elastic deformations in this model bring to light the important role played by delayed elasticity, which is shown by experimental data but has never been elucidated previously.
Symbols in geotechnology — on the purpose of scientific notation
Authors: Kälin M.
Published: April 2011

A program has been designed to bring about a logically consistent notation for the concepts used in geotechnology. The desirability of such a program has been demonstrated by historical and psychological arguments. The logical structure of the program is believed to be valid for science and engineering in general. The application to geotechnology resulted in a list of letter symbols, which are to represent an image of the physical understanding of the concepts entering geotechnological problems.
Significance of amorphous material relative to sensitivity in some Champlain clays
Authors: Yong R. N. , Sethi A. J. , LaRochelle P.
Published: April 2011

The sensitive-clay profile samples obtained from the St. Alban and Gatineau areas have been analysed with respect to their mineralogy, amorphous material content, pore-fluid chemistry, electrokinetic potential, and surface area. These compositional and surface properties are examined in relation to the sensitivity of Champlain clays. The importance of amorphous material in these clays is seen to be demonstrated in terms of its influence on sensitivity, viz., a high amorphous content correlates with a low sensitivity. The relevant mechanisms identified with the role of such materials are postulated to lie in electrostatic attraction, presence of micropores, and development of cementitious bonds.
Pore-pressure response beneath a ring foundation on clay
Authors: Lo K. Y. , Becker D. E.
Published: April 2011

A 9 m diameter and 22 m high concrete silo with a ring footing was instrumented and its performance monitored. The instrumentation included 12 pressure cells, 7 piezometers, 9 settlement cells, and 12 settlement pins. Continuous sampling and vane testing, together with field determination of permeability and coefficient of earth pressure at rest, were also carried out.The subsoil conditions at the site consist of a 3 m crust overlying an 18 m thick soft to firm, slightly overconsolidated clay stratum, which is underlain by bedrock.This paper presents the results of field observation in general, with particular emphasis on the pore-pressure response. It was found that, in spite of the relatively low factor of safety against bearing capacity failure and the considerable load transfer, the maximum measured excess pore pressure amounts to only 40% of the measured applied stress at the silage–soil interface. Important dissipation of pore pressure during loading occurred. The postfilling rate of dissipation of pore pressure was also rapid, due to the high field value of the coefficient of consolidation. Consistently, the total settlement observed up to date was also small.An analysis of the results is carried out for the interpretation of the favourable performance. The implication to the design of similar foundations is also discussed.
Uplift of objects by an upfreezing ice surface
Authors: Mackay J. Ross , Burrous C.
Published: April 2011

Laboratory and field experiments show that many kinds of solid objects are readily uplifted by an upfreezing ice surface and that uplift pressures can approximate the heaving pressures for soils with similar pore sizes. Uplift can be explained by ice-segregation theory. Frost heave by ice segregation against stones at the bottom of the active layer in an area of continuous permafrost is considered.
Third Canadian Geotechnical Colloquium: Ice forces on wide structures
Authors: Kry P. R.
Published: April 2011

Successful use of artificial islands as exploration drilling platforms in the southern Beaufort Sea requires an understanding of the interactions of ice sheets with wide structures. Ice forces exerted on wide structures arise from the mechanical processes inherent in particular ice failure modes as environmental stresses move an ice sheet past a structure. Four primary ice failure modes occur against wide structures: flexure, rubble formation, buckling, and crushing. The horizontal forces associated with these modes differ by more than two orders of magnitude depending on structure geometry, ice sheet properties, and ice movement rates. Structure width influences the occurrence of ice failure modes, the ice failure stresses, and the total forces that can be exerted on a structure by an ice sheet. The relative inability to clear failed ice around wide structures (compared with narrow structures) leads to rubble formation when ice movement is continuous. After consolidation, the resulting rubble field can amplify forces exerted on the structure. Increased structure width generally results in decreased expected forces per unit width of structure. For crushing, the most serious ice failure mode for island design, increased structure width generates the possibility of nonsimultaneous failure. The resulting averaging of statistical variations across the width leads to reduced expected stresses for wide compared to narrow structures.
A mechanistic theory of ice lens formation in fine-grained soils
Authors: Konrad Jean-Marie , Morgenstern Norbert R.
Published: April 2011

This study reveals that a freezing soil can be characterized by two parameters, the segregation-freezing temperature Ts and the overall permeability of the frozen fringe [Formula: see text]. During unsteady heat flow, the variation of these parameters with temperature produces rhythmic ice banding in fine-grained soils. At the onset of steady-state conditions, freezing tests conducted at a fixed warm end temperature showed that Ts was independent of the cold side step temperature. In addition, a model is presented that indicates how the overall permeability of the frozen fringe can be calculated without detailed measurements at the scale of the frozen fringe. It is also constant in the tests reported here.
Geotechnical problems related to the building of a tailings dam on sensitive varved clay
Authors: Capozio N. U. , Ouimet J. M. , Dupuis M. M.
Published: April 2011

At Noranda Mines in Matagami, Quebec, the construction of a 7-m tailings dam was begun in 1974 by hydraulically depositing mine tailings across a lake. A tailings pond was thus created upstream together with a downstream sedimentation pond regulated by a weir. The presence of longitudinal cracks along the crest of the dam was observed in 1978. This generated some doubts as to the stability of the dam which rests on a 24-m thick deposit of soft sensitive varved clay.Following a first study in 1978, the fissured area was used as a berm for yet another embankment which was built upstream of the unstable zone. In order to reevaluate the stability of the structure and the consequences of an eventual dam rupture, second and third geotechnical investigations were undertaken in 1980 and 1981. This paper presents the main conclusions of these investigations. It also includes the results of borings, in-situ vane tests, and stability analyses that were used to study the problem and made the planning of remedial measures possible.
Expansive–shrinkable soils in China
Authors: Hou Shitao
Published: April 2011

The paper describes the origin, mineralogy, and engineering behavior of the expansive–shrinkable soils of China, and presents deformation characteristics of buildings founded on these soils. The evaluation of sites on expansive–shrinkable soils is also considered. Finally, it presents two successful engineering case records of industrial and urban structures on expansive soils in China.
The causes and effects of aging in quick clays
Authors: Lessard Ghislain , Mitchell James K.
Published: April 2011

The physicochemical properties of a clay from La Baie, Quebec were found to be typical of Champlain quick clays: very low plasticity, liquidity index greater than 3, sensitivity greater than 500, and pH of about 9.5. The mineralogy is characterized by the abundance of primary or "rock flour" minerals such as feldspar, quartz, amphibole, and calcite, with illite as the principal clay mineral. The pore water chemistry consists predominantly of sodium bicarbonate. Low concentrations of sulfate, calcium, and magnesium and high alkalinity and pH are attributed, in part, to anaerobic sulfate-reduction processes taking place in situ.Quick clay samples stored in the laboratory showed signs of aging regardless of the storage procedure. The remoulded strength and the liquid limit increased with time, whereas the sensitivity, the liquidity index, and the pH decreased. The water content, plastic limit, and undisturbed strength remained practically unchanged. The pore water concentrations of calcium, magnesium, and sulfate increased by severalfold.The aging phenomenon is attributed, for the most part, to the oxidation of iron sulfide, which results in the formation of iron hydroxide and sulfuric acid. The production of acid causes the dissolution of calcium carbonate, which increases the concentration of divalent cation in the clay, thereby reducing interparticle repulsion and increasing the remoulded strength. The oxidation of organic matter, resulting in the formation of carbonic acid, also contributes to the aging by its effect on the solubility of calcium carbonate. Key words: aging, chemical reactions, physicochemical phenomena, sensitivity, time effects.
Ultimate pile capacity in layered soil under eccentric and inclined loads
Authors: Meyerhof G. G. , Purkayastha R. D.
Published: April 2011

The ultimate bearing capacity of rigid model piles and pile groups in layered soil consisting of clay overlying sand has been investigated for various combinations of eccentricity and inclination of load and with varying thicknesses of clay layer. The effect of eccentricity and inclination of the load and thickness ratios of clay layer to pile embedment in the sand on the bearing capacity can be represented by simple interaction relationships to estimate the ultimate load. The results of load tests on single model piles and freestanding pile groups are presented in the form of polar bearing capacity diagrams and are compared with the theoretical estimates. The thickness of clay layer on the sand is found to have a significant influence on the bearing capacity of single piles and pile groups. Key words: pile foundation, model test, layered soil, eccentric load, inclined load, sand, clay, analysis, bearing capacity.
Geotechnical condition of slopes at a proposed pipeline crossing, Great Bear River valley, Northwest Territories
Authors: Savigny K. W. , Morgenstern N. R.
Published: April 2011

An in situ analysis of naturally occurring creep has been carried out in ice-rich permafrost soils underlying a slope at the proposed Canadian Arctic Gas pipeline crossing of Great Bear River in the Northwest Territories. This is the second of four papers that describe the study. Field investigation and instrument installation techniques are described and geological, geotechnical, and geothermal results are presented. The data presented here are intended to facilitate clear interpretation of deformation observations in the third paper. The data are representative of ice-rich glaciolacustrine clay deposits that are widespread in the mid-Mackenzie Valley area. Key words: Mackenzie Valley, pipelines, slopes, permafrost, soils, drilling, sampling, geotechnical, geothermal.
Effect of tunnel excavation on transmissivity distributions and flow in a fracture zone
Authors: Tannant D. D. , Kaiser P. K. , Chan D. H.
Published: April 2011

During an excavation-response experiment performed at the Underground Research Laboratory (Atomic Energy of Canada Limited, Pinawa, Man.) a decrease in fracture-zone transmissivity was measured as a tunnel intersected the room 209 fracture zone. The decrease in transmissivity was greatest as the pilot and the slash faces passed the fracture zone. The transmissivities increased towards their preexcavation values as the faces proceeded past the fracture zone. This response suggested that shear stresses or displacements controlled the hydraulic behaviour of the fractures. The hydraulic response in the fracture zone was analyzed using finite element models. Predictions of shear-displacement distributions in the fracture zone as a function of face position were obtained from a three-dimensional finite element model using joint elements to represent the fracture zone. A phenomenological relationship between shear displacement and transmissivity change was used to modify the transmissivity distributions in the fracture zone based on shear displacements for different excavation stages. Seepage analyses with these transmissivities provided predictions that matched closely the field measurements obtained from the room 209 fracture zone. These results and the inability of conventional, normal stress dependent, fracture closure to predict consistently the hydraulic response support the concept of shear causing a reduction in fracture-zone transmissivity. Excavation-dependent, shear-induced reduction in transmissivity provides an alternate mechanism for interpreting and understanding the hydraulic response of disturbed fracture zones. Key words : transmissivity, shear displacement, fluid flow, fracture zone, excavation.
Determination of creep properties of frozen soils by means of the borehole stress relaxation test
Authors: Ladanyi B. , Melouki M.
Published: April 2011

The objective of this investigation was to evaluate the potential use of the borehole stress relaxation test to determine the creep and strength properties of frozen soils in situ. The paper presents the results of a series of laboratory pressuremeter relaxation tests performed in frozen sand and compares three possible interpretation methods for deducing from the test results the creep and strength parameters of frozen soils. Key words : borehole relaxation, pressuremeter, in situ testing, creep and strength properties, frozen soil.
Preliminary evaluation of the influence of surfactant injection on the mechanical behaviour of a compacted till
Authors: Cabral Alexandre R. , Lefebvre Guy , Collette Pascal
Published: April 2011

One-dimensional consolidation tests were performed with till samples compacted dry of optimum to 85% of the modified Proctor density. When the applied pressure reached 200 kPa, the samples were saturated (submerged) and then flushed with two types of surfactant solutions, under a hydraulic gradient varying from 35 to 40. Significant compression occurred during submergence and as a result of flushing with a 2% solution of an anionic surfactant. Only minor additional compression resulted from flushing with a 2% solution of a nonionic surfactant. While only preliminary conclusions could be drawn from the limited test results, this study highlighted the importance of considering, in the early stages of remediation procedure design (including the selection of the surfactant), the possible deleterious effects of surfactant injection on the mechanical properties of the soil mass, particularly when it is in a loose to moderately loose state. Key words : surfactants, adsorption, hydrocarbon remediation, compression, mechanical properties, soil behaviour.
Tunnelling in Brasília porous clay
Authors: Ortigao J AR , Kochen R , Farias M M , Assis A P
Published: April 2011

The Brasília underground transportation system comprises 6.5 km of shallow tunnel excavated in a soft red soil known as porous clay that overlies harder residual soils. The tunnel diameter is 9.6 m. Settlement observations indicated that surface settlements were two to three fold the initially predicted value, although no indication of excavation instability was observed. Settlements reached, at one section, 500 mm without failure. Another striking feature was settlement amplification between the top of the excavation and the surface by a factor that averaged 1.2 but reached up to 4. This occured because of the collapsible nature of the porous clay, which presented a considerable reduction of volume as the tunnel face advanced. This paper describes tunnel design, construction, and instrumentation; and summarizes geology and soil properties from in situ and laboratory tests. Field measurements of settlements and horizontal displacements are described and analysed. The main cause of the large settlements was collapse of the porous clay structure.

Key words: tunnelling, porous clay, settlements, collapse.
Horizontal deformation in reinforced soil walls
Authors: Rowe R Kerry , Ho S K
Published: April 2011

The results of a numerical study of the horizontal deformations of reinforced soil walls with a continuous panel facing are presented. The most important material parameters are shown to be the reinforcement stiffness density and the backfill soil friction angle. The soil-facing interface friction angle, reinforcement-soil friction angle, soil Young's modulus, and facing rigidity are less important. For backfill soil having a friction angle greater than or equal to 35°, the common practice of using a truncated reinforcement scheme with reinforcement length equal to 70% of the wall height was found to be justified. Increasing the reinforcement length did not significantly reduce deformations; however, reducing the length below about 45% of the wall height did significantly increase deformations. Equally spaced reinforcement was found to give lower deformations than a "balanced" scheme, in which the spacing of reinforcement decreases with depth to provide a more uniform distribution of force in the reinforcement layers. A comparison of the numerical results and the results from an approximate method indicates reasonable agreement and identifies situations where the approximate method is most likely to give accurate results.Key words: soil reinforcement, geosynthetics, analysis, deformations, strains, forces.
Determining the orientation of fracture planes in a weathered clay till using core samples
Authors: Harris Steven M , Thomson Neil R , Novakowski Kentner S
Published: April 2011

A method has been developed to determine fracture plane orientations in clay-rich glacial deposits from core samples obtained from inclined borings. In this method, a portion of each core sample is removed to expose vertical and horizontal surfaces which are used to map each identified fracture plane. An analytical geometry technique is used in conjunction with the mapping data to determine the pole to each fracture plane. These fracture pole data can then be presented on a lower hemisphere equal area projection diagram to indicate preferential fracture plane orientations. The utility of the developed method is demonstrated through a detailed analysis of core samples collected from a 10 m x 10 m site located near Sarnia, Ontario. The data from this investigation indicated the presence of three sets of fracture planes; however, only one of these fracture sets was determined to be statistically significant. The developed method offers an alternative to mapping fracture plane orientations on exposed surfaces of trench excavations.Key words: clay, fractures, orientation, core samples.
Development and verification of a coefficient of permeability function for a deformable unsaturated soil
Authors: Huang Shangyan , Barbour S L , Fredlund D G
Published: April 2011

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 a saturated soil is a function of void ratio. The coefficient of permeability of an unsaturated soil 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 an unsaturated soil of constant volume and the coefficient of permeability for a deformable saturated soil are reviewed. A new coefficient of permeability function for a deformable unsaturated porous 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.
Analysis of the corner effect on excavation behaviors
Authors: Ou Chang-Yu , Shiau Bor-Yuan
Published: April 2011

This paper presents three-dimensional finite-element studies on excavation problems. Large computer storage and computation time are normally required for the conventional finite-element analysis, for which the boundary should be located distant from the excavation zone so that convergence can be reached. In this paper the infinite element is incorporated into a three-dimensional finite-element computer program for minimizing the number of elements used. Research results indicate that adequate convergence for the wall deflection and ground surface settlement is obtained for infinite elements located at a distance of one wall depth. This substantially reduces the number of elements used in the analysis. Furthermore, two excavation case histories are provided to confirm the appropriateness of employing the infinite element as well as the corner effect on the deformation behavior. Based on the field observations and three-dimensional analysis of the case histories, it is found that the wall deformation at the short wall is smaller than that at the long wall. The wall deformation decreases with decreasing distance from the corner. These studies further verify the corner effect on the excavation behavior.Key words: Corner effect, Finite-element method, Deep excavation, Infinite element
Permeability and volume changes in till due to cyclic freeze/thaw
Authors: Viklander Peter
Published: April 2011

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.
The significance of rate effects in modelling the Sackville test embankment
Authors: Rowe R Kerry , Hinchberger Sean D
Published: April 2011

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
Optimization of compaction zoning in loess embankments
Authors: Zhang Limin , Yu Xueming , Hu Ting
Published: April 2011

Extensive centrifuge model tests were carried out to investigate optimum compaction density zones within loess embankments 30 and 63.8 m high. In these tests, water infiltration into the slopes and upstream storm water ponds were modelled to simulate the most unfavourable working conditions. Displacement contours in the cross sections were measured and crest settlements were monitored during the tests. Finally, the optimum compaction zoning was analysed based on the comprehensive evaluation of the total crest settlement, the postconstruction settlement, and the slope stability of the embankments. It was indicated that a properly designed high loess embankment could perform satisfactorily with the lower part compacted looser than the conventional code requirements. In terms of total crest settlement and embankment cracking, the degree of compaction K of loess fills should not be less than 0.85 for 30 m high embankments and not less than 0.90 for 63.8 m high embankments. In terms of the postconstruction settlement (<0.2-0.3 m) and construction feasibility, it is expedient to compact the lower one third to K = 0.85, and the top two thirds to K = 0.90 for 63.8 m high embankments. For 30 m high embankments, the bottom zone with K = 0.85 can make up two thirds of the height.Key words: Key words: embankment, centrifuge test, compaction, settlement, stability, loess.
Modelling the rate-sensitive characteristics of the Gloucester foundation soil
Authors: Hinchberger Sean D , Rowe R Kerry
Published: April 2011

Stages 1 (1967) and 2 (1982) of the Gloucester test embankment are studied using a fully coupled finite-element model. The rate-sensitive characteristics of the foundation soil are modelled using an elastoviscoplastic constitutive equation based on the elliptical cap yield surface and Perzyna's overstress theory of viscoplasticity. The aspect ratio of the yield surface for the Gloucester foundation soil is estimated using conventional laboratory shear and consolidation test results. Calculated and measured behaviour during consolidated isotropically undrained triaxial tests and long-term Rowe cell consolidation tests are compared and the ability of the model to describe the measured behaviour of stages 1 and 2 of the Gloucester test embankment is studied. This paper explores the implications of modelling the residual or restructured properties of the Gloucester foundation soil and demonstrates the ability of a single elastoviscoplastic yield-surface model to describe the undrained and drained response of the Gloucester foundation soil during laboratory and field loading conditions.Key words: elliptical cap, rate sensitive, elastoviscoplasticity, embankment settlements, pore pressures, field performance.
Effect of unloading duration on unconfined compressive strength
Authors: Fam M A , Dusseault M B
Published: April 2011

This note examines the effect of unloading duration on unconfined compression test results. Artificial clayey specimens were prepared using the slurry consolidation technique. Extracted specimens were loaded vertically under K0 conditions, and the load was kept constant until the end of primary consolidation. Specimens were unloaded and unconfined compression tests were carried out at different times after unloading. It is observed that the longer the unloading duration, the lower the measured unconfined strength. This behavior is attributed to the presence of negative excess pore pressure that dissipates with time, reducing the strength. Using the measured coefficient of consolidation, the degree of excess pore pressure dissipation and therefore the average mean effective stress near the failure zone can be calculated at the time of failure. Mohr circles are drawn tangential to the total shear envelope, using the calculated mean effective stresses. Reasonable agreement between predicted and measured unconfined compressive strengths has been observed, suggesting that consolidation theory can be adopted to assess the effect of unloading duration on unconfined compressive strength. Finally, engineering applications using a similar concept are briefly discussed.Key words: clays, unloading, consolidation, unconfined compression tests, triaxial tests.
Influence of stress history on the strength parameters of an unsaturated statically compacted soil
Authors: Nishimura Tomoyoshi , Hirabayashi Yasunari , Fredlund Delwyn G , Gan Julian K-M
Published: April 2011

Unsaturated soils are generally near the ground surface and are commonly overconsolidated due to environmental effects. The stress state variables for an unsaturated, in situ profile consist of the net total stress, (σ - ua), and matric suction, (ua - uw), where σ is the total stress (in three directions), ua is the pore-air pressure, and uw is the pore-water pressure. These stress state variables control the behavior of the unsaturated soil. A total stress ratio, TSR, was used in this study as a measure of the stress history. The total stress ratio is defined as the ratio of the compaction pressure to the current confining pressure. Shear tests were conducted using a modified direct shear apparatus on a statically compacted unsaturated soil subjected to various total stress ratios with controlled matric suction. The shear strength parameters (i.e., ϕ', ϕb, and c') for an unsaturated soil were measured using the modified direct shear apparatus. The total stress ratio influences the shear strength parameter ϕb of a compacted soil. The shear strength parameter ϕb decreases with matric suction regardless of the loading history. For a compacted soil with a total stress ratio of 1.0, ϕb was higher than that for the soil tested at a total stress ratio greater than 1.0, regardless of increase in matric suction, and was shown to be influenced by loading history.Key words: unsaturated soil, shear strength, stress history, compacted soil, direct shear test, matric suction.