bluuebunny/crossref_metadata_2025 huggingface dataset:
Breakout capacity of model suction anchors in soil
Authors: Wang M. C. , Demars K. R. , Nacci V. A.
Published: April 2011

The breakout capacity of eight model underwater suction anchors was investigated in a 30-in. (76-cm) wide, 72-in. (183-cm) long, and 32-in. (81-cm) deep unpressurized cast iron tank. The test soils were a medium fine sand, a silt, and a clay. A pullout rate of approximately 0.1 in./min (0.3 cm/min) was used for all tests.A breakout capacity equation for the suction anchor was developed based upon the Mohr–Coulomb failure theory. Predicted breakout capacities compare favorably with the measured values from the laboratory model study. The breakout capacity equation which is developed is therefore satisfactory for the range of conditions studied.The suction anchor possesses a high degree of mobility and would be particularly useful for short-term anchorage. Potential applications of the suction anchor include the anchorage for research submersibles, coring platforms, and certain salvage and dredging operations.
Undrained strength anisotropy in embankment stability analysis
Authors: Law K. Tim
Published: April 2011

An approximate stability analysis taking strength anisotropy into account is proposed, from which various correction curves are established. Examination of these curves shows that there is one particular constant correction factor applicable to most practical situations of embankment construction. This can be written as Sa = 0.95Cm where Sa is the available subsoil strength and Cm the mean strength from the vertical and horizontal specimens. This expression is shown to be in agreement with existing field experience.
Elastic solutions for the design and analysis of rock-socketed piles
Authors: Pells P. J. N. , Turner R. M.
Published: April 2011

This paper gives elastic solutions for the following: (i) settlement of a shear socket; (ii) settlement reduction due to recessment of a shear socket in a shaft; (iii) settlement reduction of flexible or rigid footings due to recessment in a shaft; (iv) load distribution in a rock socket; and (v) settlement of a rock socket.This paper illustrates the use of these solutions in the design of socketed piles and in the back-analysis of field tests on rock sockets.
Impact penetration of sand
Authors: Knight D. G.
Published: April 2011

This paper describes an instrumented impact penetrometer suitable for the measurement of in situ properties of soils. The velocity and depth of penetration at any instant are calculated from the deceleration record. Results are presented from a series of tests on a dry sand target for a range of impact velocities up to 12 m/s.
Yielding and rupture in a lacustrine clay
Authors: Baracos A. , Graham J. , Domaschuk L.
Published: April 2011

Recent tests have examined the properties of block samples and tube samples from depths to 12 m in Winnipeg clay. Careful trimming and a wide variety of testing procedures have permitted new insights into the behaviour of the clay that is markedly anisotropic and non-homogeneous. The effective strength envelope for "blue clay" from 6 to 12 m depth can be simplified into three straight-line sections. At low stresses, a section of the envelope has been identified having a low cohesion intercept and a high "friction" angle. This is thought to be caused by close Assuring in the clay, and controls the field behaviour in many small embankment, riverbank, and excavation problems. At in situ stress levels, the clay dilates markedly as failure is approached. Porewater pressures depend strongly on stress levels during laboratory reconsolidation. Residual strengths are low, and are influenced by the methods used during testing. Yielding has been clearly identified for shear failure of the grain structure, but is more poorly defined for increasing normal octahedral stresses. The work has emphasized the importance of selecting appropriate testing procedures and stresses for field applications.
"Where has all the judgment gone?" The fifth Laurits Bjerrum memorial lecture
Authors: Peck Ralph B.
Published: April 2011

This lecture aims at significantly reducing the probability of failure of earth dams by consciously fostering the application of engineering judgment in design and application.
Analysis of a small debris slide in coastal Alaska
Authors: Sidle R. C. , Swanston D. N.
Published: April 2011

On October 1, 1980, a moderately intense storm at Trap Bay, Alaska, triggered a small debris slide in a forested midslope depression that was instrumented to record the maximum piezometric rise. Although the return period for the storm was <2 years, 54% (3.68 cm) of the total rain fell during the final 3 h causing the soil mantle to become nearly saturated. This resulted in an average maximum pore-water pressure of 2.2 kPa at the sliding surface, causing failure. Analysis of the mechanics of the failure showed that an apparent cohesion of 2.0 kPa, probably due to rooting strength, was acting on the 43° hillslope. Calculated factors of safety for such thin, partially saturated soils are very sensitive to small changes in apparent cohesion and should be used with caution on such sites.
Injection-induced stress and fracture orientation changes
Authors: Dusseault Maurice B. , Simmons John V.
Published: April 2011

Examination of the field evidence suggests that induced vertical fractures in the cohesionless, shallow oilsand reservoirs of northeastern Alberta are unlikely to remain vertical when large volumes of hot fluids are injected into them.Numerical models are assembled taking into account the appropriate material properties, model geometries, and boundary conditions in order to simulate as closely as possible the stress response of a reservoir to induced fracturing. The results suggest that generation of horizontal fractures is extremely likely and that thermal input enhances this probability. Overstress (above overburden) may be maintained by an elastic skin effect on the fracture boundary. Continued displacement and pore pressure permeation can overcome this overstress resulting in the cyclic stress buildup–breakthrough pattern reported in the literature.The inadequacy of static geomechanical models (no fracture orientation change) is pointed out; correct simulation requires correct process comprehension.
An influence line approach to the stabilization of slopes by cuts and fills
Authors: Hutchinson J. N.
Published: April 2011

The effects on stability of concentrated downward and upward influence loads acting at successive positions between the head and toe of a landslide with a fixed failure surface are expressed in terms of influence lines for the resultant changes in the factor of safety. Of particular importance are the positions where no change in factor of safety is produced. On a slope section these are referred to as "neutral points": the traces of these in plan are termed "neutral lines." These concepts provide valuable guidance on the most effective locations and distributions of corrective cuts and fills, particularly for slides on pre-existing slip surfaces.Stabilization of slides by loading the toe is shown to be generally preferable to unloading the head. In complex slides, corrective cuts and fills are best restricted to the extreme head and toe positions, intermediate cuts or fills being avoided.The conditions are defined under which the flattening of slopes by the removal of material reduces stability. In certain cases such a flattening can occur naturally by the local collapse of the steep toe of a landslide. This can lead to an immediate reduction in its factor of safety and a consequent sudden acceleration. Keywords: Slope stabilization, corrective cuts, corrective fills, influence lines, neutral points, neutral lines, slope flattening.
Controlling sand placement during the building of artificial islands
Authors: Shields D. H. , Domaschuk L. , Corkal D. W. , McCutchon J. R.
Published: April 2011

A new way to construct artificial islands of sand is described. The method shows promise of considerable cost saving. The present high cost of island building is due to the difficulty of making underwater sand slopes steep. Simply dumping sand into the ocean results in slopes of from 12 to 15 horizontal to 1 vertical. These shallow slopes have enormous implications in terms of sand volume and cost. The sand can be tremied into place to form a steep-sided ring or bund. Handling large quantities of sand in this way is expensive. Small-scale model tests show that if the sand is mixed with certain chemicals the resulting 'cohesion' enables the sand to fall through seawater as a block, with little dispersion. Steep underwater slopes result. Low-cost, nontoxic (environmentally safe) chemicals were used in the experiment. Keywords: construction, artificial islands, sand, oceans, dredging.
Postconstruction settlement of an expressway built on peat by precompression
Authors: Samson Laval
Published: April 2011

This paper presents the analysis of 18 years of settlement observations of two expressway embankments built on a peat deposit with an initial depth of 3.0–5.8 m using the precompression technique. Observations show that upon removal of the temporary surcharge the highway embankments heaved for about 1 year by a total of 4.3–7.9 cm. This foundation movement was followed by slow-rate settlement for a few years and subsequently by additional secondary settlement occurring at a greater rate of settlement versus logarithm of time. Eighteen years after construction, settlements range from 2.7 to 11.9 cm. It is concluded that precompression has been effective in reducing postconstruction settlement by about 65% and its effectiveness on the long-term settlement was experienced for [Formula: see text] years. After that, the rate of settlement became identical to that of the normally consolidated peat. Key words: peat, precompression technique, secondary compression, long-term settlement, field observation, swelling, surcharge.
Multiple seepage faces on layered slopes and their implications for slope-stability analysis
Authors: Rulon Jennifer J. , Freeze R. Allan
Published: April 2011

This study provides an analysis of the water-table configuration and pore-pressure distribution in layered hillsides. A finite-element model was used to simulate two-dimensional, saturated–unsaturated, steady-state flow through layered slopes. A laboratory sand-tank experiment was used to verify the physical foundation of the mathematical model. It is shown that layered slopes feature multiple seepage faces, perched water tables, and wedge-shaped unsaturated zones. The pore-pressure distribution and the distribution of multiple seepage faces are strongly dependent on the position of the impeding layers and their hydraulic properties. Predictions of pore-pressure fields based on homogeneous, saturated analyses may be significantly in error when applied to problems on layered slopes. Slope-stability analyses on layered slopes that do not take into account the presence of unsaturated wedges beneath the impeding layers can lead to overdesign of the stable slope angle. Key words: groundwater conditions, unsaturated zone, layered slopes, seepage face, slope stability.
Some geotechnical characteristics of fragmented Queenston Shale
Authors: Caswell R. H. , Trak B.
Published: April 2011

This paper presents the results of an experimental study to determine the stress–strain behaviour of fragmented Queenston Shale from Russell, Ontario and to investigate how its strength properties altered when the material was subjected to repeated slaking cycles. Slaking tests showed that large (cobble-size) blocks of the material degrade rapidly to a particle size of 20 mm upon exposure to water and air. Consolidated drained tests in a large triaxial apparatus under monotonic loading conditions on specimens of fresh and slaked material were performed. They indicate that the shear strength of fragmented Queenston Shale of particle size smaller than 20 mm is not affected by slaking. Key words: Queenston Shale, compaction shale, granular material, rockfill, slaking, shear strength, consolidated drained tests.
Analysis of field performance—the Thunder Bay tunnel
Authors: Ng Robert M. C. , Lo K. Y. , Rowe R. K.
Published: April 2011

A numerical method for the calculation of the distribution of displacements for tunnelling in clays has been developed. The method employs an orthotropic elastic – perfectly plastic soil model that takes into account various sources of ground loss and soil–lining interaction. Both undrained and drained analyses have been carried out and the results are compared with the measured soil displacements of two instrumented arrays at the Thunder Bay tunnel. It is shown that the range of maximum settlements, the shape of the settlement troughs, and the pore pressure change, as well as the magnitude and direction of spatial displacements obtained from the analyses, compare reasonably well with the results of field measurements for both short- and long-term conditions. Key words: tunnelling, clays, anisotropy, elastic–plastic displacements, settlement trough, Thunder Bay tunnel.
Erosivity of intact clay: Influence of the natural structure
Authors: Lefebvre Guy , Rohan Karol , Milette Jean-Pierre
Published: April 2011

Erodibility drill hole tests have been conducted on three Eastern Canadian clays on intact structured specimens, on specimens destructured by consolidation, and on remolded and reconsolidated specimens. The intact structured clay is highly resistant to erosion; links between particles can resist high tractive stresses. The resistance to erosion is drastically decreased however when the clay is destructured by consolidation or remolding. The decrease varies from one clay to the other; after consolidation the resistance to erosion is very low for the St. Hyacinthe clay but still high for the St. Leon clay. The clays are even more erodible after remolding and reconsolidation, but important differences are still observed between the clays tested. The pore water salinity appears as a significant factor in the understanding of the different behaviour observed after destructuration of the clay by consolidation or remolding. Key words: erosivity, rate of erosion, critical tractive stress, structured clay, destructuration, consolidation, remolding, pore water salinity.
Small-strain behavior of frozen sand in triaxial compression
Authors: Andersen Glen R. , Swan Christopher W. , Ladd Charles C. , Germaine John T.
Published: April 2011

The stress–strain behavior of frozen Manchester fine sand has been measured in a high-pressure low-temperature triaxial compression testing system developed for this purpose. This system incorporates DC servomotor technology, lubricated end platens, and on-specimen axial strain devices. A parametric study has investigated the effects of changes in strain rate, confining pressure, sand density, and temperature on behavior for very small strains (0.001%) to very large (> 20%) axial strains. This paper presents constitutive behavior for strain levels up to 1%. On-specimen axial strain measurements enabled the identification of a distinct upper yield stress (knee on the stress–strain curve) and a study of the behavior in this region with a degree of precision not previously reported in the literature. The Young's modulus is independent of strain rate and temperature, increases slightly with sand density in a manner consistent with Counto's model for composite materials, and decreases slightly with confining pressure. In contrast, the upper yield stress is independent of sand density, slightly dependent on confining pressure (considered a second order effect), but is strongly dependent on strain rate and temperature in a fashion similar to that for polycrystalline ice. Key words : frozen sand, high-pressure triaxial compression, strain rate, temperature, modulus, yield stress.
Three-dimensional dynamic response analyses of Cogswell Dam
Authors: Boulanger Ross W. , Bray Jonathan D. , Merry Scott M. , Mejia Lelio H.
Published: April 2011

The recorded strong motions at Cogswell Dam during the 1987 Whittier Narrows and 1991 Sierra Madre earthquakes provide a valuable opportunity to evaluate the applicability of established engineering procedures for evaluating the dynamic response of dams with highly three-dimensional geometries. In addition, these records provide an opportunity to back-calculate the dynamic properties of rockfill materials, which cannot be easily measured in the laboratory or in situ. Peak transverse crest accelerations of 0.15 g and 0.42 g were recorded during the Whittier Narrows and Sierra Madre earthquakes, respectively. Combined with analyses of the trailing portions of these strong motion records, the field data cover a wide range of induced shear strains. Two-dimensional and three-dimensional dynamic response analyses were performed using established engineering procedures, and their results are compared with the recorded responses. Dam–canyon interaction and topographic effects appear to have influenced the seismic response of the dam significantly. Estimates of the in situ dynamic rockfill properties, including the modulus degradation relationship, are presented. Key words : rockfill, dynamic properties, embankment dams, earthquake response.
Effects of cyclic freezing and thawing on volume changes and permeabilities of soft fine-gained soils
Authors: Eigenbrod K D
Published: April 2011

Soft, fine-grained soils were exposed to cyclic one-dimensional, open-system freezing and thawing, resulting in maximum volume changes of up to 30%, depending on the initial moisture content and plasticity of the clay as well as on the rate of freezing. A linear relationship between the net volume changes subsequent to freezing and thawing and the liquidity index prior to freezing and thawing was obtained. This correlation is not unique, but depends on rate and mode of freezing. Thus, settlements from freezethaw consolidation in the field can be predicted from such tests if the rate and mode of freezing are the same as in the field. During cyclic freezing and thawing the soils became fissured and jointed, resulting for most clays in large increases in their bulk permeabilities, which increased with an increasing number of freezethaw cycles, often by more than two orders of magnitude. For some materials, however, little change in permeability occured.

Key words: cyclic freezethaw, clays, freezethaw consolidation, permeability, volume changes.
Simulation of time-dependent movements in Syncrude tailings dyke foundation
Authors: Wedage AMP , Morgenstern N R , Chan D H
Published: April 2011

Foundation movements at the Syncrude tailings dyke continued over several years in response to the construction of the dyke. Major movements have been observed in a relatively narrow layer of previously sheared clay-shale material of the Clearwater Formation. The residual strength of this highly plastic clay increases with the rate of shear. By reviewing the existing literature on the rate effects on residual strength and using data from new experiments on Clearwater Clay Shale, a general correlation between soil plasticity and rate effects is found. This rate dependence of the residual strength of Clearwater clay shale has been incorporated into a deformation analysis, which made it possible to compute time-dependent movements of the foundation soil to a satisfactory level. By using a rate-dependent plasticity model, a prediction of anticipated foundation velocities and how they decrease with time may be achieved.Key words: finite element, rate effects, residual strength, Syncrude tailings dyke, time-dependent movements.
Influence of pressure, saturation, and temperature on the behaviour of unsaturated sand-bentonite
Authors: Wiebe Bradley , Graham James , Tang Gary Xiangmin , Dixon David
Published: April 2011

Triaxial compression tests were performed on unsaturated sand-bentonite buffer at elevated temperatures and pressures. Air and water drainage lines from the specimen were generally kept closed through (i) heating, (ii) pressuring, and (iii) shearing. The tests can therefore be characterized as undrained-undrained-undrained tests. Effects of open drainage were also explored. Confining pressures ranged from 0.2 to 3.0 MPa at temperatures of 26, 65, and 100°C. Specimens were statically compacted to a constant dry density of 1.67 Mg/m3, and to degrees of saturation between 35 and 98%. Suction - water content relationships were established to determine the initial total suction before testing. Results indicate that undrained strengths increase with decreasing degree of saturation (50 <= Sr <= 100%), with increasing confining pressure, and with decreasing temperature. The normalized compression modulus E50/su does not respond monotonically to changes in saturation, pressure, and temperature. Changes in strength and stiffness have been described in relation to net mean stress and suction in shear strength - net mean stress - suction space.Key words: sand-bentonite, unsaturated, suctions, temperature, strength, stiffness, structure.
Liquefaction flowslides in Rocky Mountain coal mine waste dumps
Authors: Dawson R F , Morgenstern N R , Stokes A W
Published: April 2011

Over the past 25 years there have been a large number of long runout flowslides from Rocky Mountain coal mine waste dumps. The waste dumps are constructed as end-dumped fills with an angle of repose of 38°. Dump heights range between 100 and 400 m. The dumps are normally founded on mountain slopes that are covered with a thin veneer of granular colluvial and dense stony till materials. Conventional stability analyses carried out for these dumps using friction angles equal to the angle of repose for the waste rock and typical values ranging from 30 to 32° for the foundation materials indicate that many should be stable. The flowslides occur rapidly and display surprisingly long runouts of up to 2 km in some cases. Detailed studies of three of these events indicate that static collapse of saturated or nearly saturated sandy gravel layers within the dumps may be responsible for the initial failure and the generation of high pore pressures which result in high runout mobility.Key words: mine waste dumps, flowslide, static liquefaction, collapse mechanics.
Flexural excitation in a standard torsional-resonant column device
Authors: Cascante Giovanni , Santamarina Carlos , Yassir Najwa
Published: April 2011

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.
Evaluating cyclic liquefaction potential using the cone penetration test
Authors: Robertson P K , Wride CE (Fear)
Published: April 2011

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
The rehabilitation of a passive-ventilated slab on grade foundation using horizontal thermosyphons
Authors: McKenna J K , Biggar K W
Published: April 2011

Due to the plugging of the vents beneath a vented-slab concrete foundation of the Supply Building at Canadian Forces Station Alert on the northern tip of Ellesmere Island, excessive thermal degradation of the underlying permafrost caused unacceptable settlement of the slab. It was determined that maintenance of the existing system would be an ongoing problem and replacement of the structure would cost $3 million and 3 years to construct. To re-establish the thermal regime under the Supply Building, it was decided to use a newly developed horizontal thermosyphon system installed in the existing vents to rehabilitate the foundation. The thermosyphon installation presented some unique problems owing to the restricted access around the building and the requirement to drill horizontally beneath the building, which necessitated the fabrication of a special drill rig. In addition, the use of horizontally placed thermosyphons is a relatively new application of the existing technology. The paper briefly describes the initial problem, the development of the solution, and describes in detail the actual installation and performance of the horizontal thermosyphon system with 3 years of soil temperature data.Key words: permafrost, thermosyphon, foundation, settlement, ventilated slab, CFS Alert.
A diffusion batch method for determination of the adsorption coefficient of benzene on clay soils
Authors: Zhang Xiao , Barbour S Lee , Headley John V
Published: April 2011

The adsorption and desorption of contaminants on soil and sediment are key mechanisms governing the fate and transport of aqueous-phase hydrocarbons in groundwater. A diffusion batch method for measuring the adsorption coefficient was developed in this study. This method provides a simple and reliable procedure for assessing the adsorption of organic compounds by soil. The method relies on diffusion, rather than shaking and agitation, to bring the solid and solution into chemical equilibrium. Samples of Regina clay, prepared by a variety of methods, were tested for benzene adsorption using this test. Initial testing indicated that equilibrium was attained within 10 days from the start of the adsorption test. The measured adsorption coefficient (Kd) for samples of benzene on Regina clay prepared at various initial water contents (air-dried, liquid limit, slurried, or statically compacted) were in the range of 3.2-7.2 mL/g. A comparison of the diffusion batch method and the conventional ASTM batch method showed that the diffusion batch method has lower variability, particularly over low concentration ranges.Key words: adsorption, diffusion, batch test, adsorption coefficient, organic, benzene, clay.
Modeling soil freeze-thaw and ice effect on canal bank
Authors: Zhang Z X , Kushwaha R L
Published: April 2011

The experiments for modeling soil freeze-thaw and ice action on canal banks were conducted in a laboratory. In addition to the frost heave that was observed during the period of soil freezing, there was an abrupt increase in frost heave that occurred at the beginning of soil thawing. This phenomenon lasted for over approximately 100 hours, and the frost heave induced during this period reached as much as 22.62 mm. At the same time, peak ice pressures also occurred as the soil was thawing. It has been suggested that the frost heave during initial soil thawing may be associated with the change in energy status at the water-ice interface resulting from the buildup of internal stress in the soil during the formation of ice lenses.Key words: frozen soil, freeze-thaw cycle, frost heave, thawing settlement, canal protection.
Subgrade reaction and load-settlement characteristics of gravelly cobble deposits by plate-load tests
Authors: Lin Ping-Sien , Yang Li-Wen , Juang C Hsein
Published: April 2011

This paper presents the result of plate-load tests conducted on a gravelly cobble deposit in Taichung Basin, Taiwan. The geologic formation of the gravelly cobble deposit makes it very difficult to obtain large undisturbed samples for laboratory testing. These field tests provide an opportunity to examine the applicability of existing theories on bearing capacity and subgrade reaction in this geologic formation. The modulus of subgrade reaction is of particular importance in the local practice of designing high-rise buildings on mat foundations. The results of the plate-load tests on this soil deposit are analyzed and discussed.Key words: plate-load test, gravelly cobble deposit, modulus of subgrade reaction, bearing capacity.
Truly undrained response of granular soils with no membrane-penetration effects
Authors: Sivathayalan S , Vaid Y P
Published: April 2011

Conventional and truly undrained behaviour of granular soils is compared by direct experimental measurements. The truly undrained behaviour was determined by compensation for membrane penetration induced volume changes, using a feedback controlled water injection system. A more reliable, nondestructive, specimen-specific method is presented to measure the magnitude of membrane penetration, for use in the injection routine. This new method, unlike the existing methods, does not make any assumptions regarding either the constitutive behaviour or isotropy of sands. It is shown that the truly undrained pore pressures predicted by correcting those observed in conventional undrained tests are too large, implying incorrect linkage between membrane penetration induced volume change and volumetric constitutive behaviour of the granular material. The sand which responds in a strain-hardening manner in conventional undrained loading may, in fact, be strain softening (liquefiable) when truly undrained, a matter of serious practical concern.Key words: sand, truly undrained behaviour, liquefaction, membrane penetration.
On the long-term hydraulic gradient in the thick clayey aquitard in the Sarnia region, Ontario
Authors: Husain Muin M , Cherry John A , Fidler Scott , Frape Shaun K
Published: April 2011

Much of the southwestern part of Ontario between Lake Huron and Lake Erie has a thin freshwater aquifer overlain by an aquitard of Late Pleistocene clayey glaciolacustrine deposits and underlain by a thick Devonian shale aquitard. In a large area east of the St. Clair River, where the Quaternary aquitard is 30-50 m thick, groundwater of Pleistocene origin (identified by 18O and 2H signature) occurs in the aquifer and in the bottom part of the Quaternary aquitard. Numerous piezometer nests in the aquitard show a downward hydraulic gradient with depth. In some areas, the aquitard has downward gradients only in the upper part and upward gradient in the lower part, indicating a transient condition. The piezometer nests in the clayey aquitard also show an increase in Cl- concentration with depth. Long-term piezometer monitoring at two sites show a major shift in the aquitard hydraulic gradient since 1983 and a large rise in head in the underlying aquifer. Analyses of initial aquifer water levels, reported in well drilling records, indicate a large decline in the potentiometric surface of the aquifer between the 1940's and the 1970's followed by a recent rise in the surface in part of the region. This pattern is consistent with well drilling and water use records indicating that 7000 wells were installed in the aquifer in the three decades since 1940 and that groundwater use has greatly diminished in the past 10-15 years due to rural pipeline distribution of lake and river water. The hydraulic gradient in the aquitard is slowly adjusting to the rise in the aquifer potentiometric surface. One-dimensional solute transport modelling provides close matches to the vertical profiles of Cl- migrating upward from the aquifer since deglaciation, 15 000 - 18 000 years before present, by diffusion with little or no advection. The lack of advection indicates a near-neutral long-term hydraulic gradient. As the withdrawal rate of water from the aquifer continues to decline, it is expected that the hydraulic head in the aquitard in much of the area westward of the recharge area will continue to adjust for many decades.Key words: clay, aquitard, aquifer, water use, hydraulic gradient.
Monotonic and dilatory pore-pressure decay during piezocone tests in clay
Authors: Burns S E , Mayne P W
Published: April 2011

During a pause in cone penetration in fine-grained soils, pore-water pressure dissipation tests are performed to evaluate the coefficient of consolidation. For standard piezocones with shoulder filter elements, soft clays and silts show a monotonically decreasing response with time; however, dissipation tests performed in heavily overconsolidated silts and clays show dilatory behavior, with the pore-pressure behavior increasing from the initial measured value to a maximum, and then decreasing to hydrostatic values. This paper presents a theoretical framework which combines cavity-expansion theory and critical-state soil mechanics with an analytical solution to the radial consolidation equation. The method is able to describe the pore-pressure response curve for dissipation tests performed in soils which demonstrate either monotonically decreasing or dilatory pore-pressure behavior.Key words: cavity expansion, consolidation, piezocone, pore pressure.
Dynamic site response evaluation of the Port City of Aqaba (Jordan) employing the equivalent linear method
Authors: Fahmi Khalid J , Malkawi Abdallah I. Husein
Published: April 2011

As part of an ongoing research program to develop local seismic engineering ground motion parameters for implementation in the Jordanian Seismic Building Code, a practical contribution is made to determine the local site coefficient (S) for the Port City of Aqaba, southern Jordan. Employing probabilistic peak ground acceleration estimates using FRISK, the overall dynamic site response design spectrum is obtained through the calculated response spectrum based on selected soil-rock column profiles applying SHAKE91. The parabolic shape of the S coefficient design spectrum is given by the following relationships:S = 1.06 for Tb/ Ts<= 0.56S = -0.81 + 4.68(Tb/ Ts) -2.38(Tb/ Ts)2for 0.56 < (Tb/ Ts)<=1.43S = 1.00 for Tb/ Ts>1.43where Tband Tsare the structural and site response design periods (in seconds), respectively.Key words: dynamic, site, response, Aqaba, spectrum, design.
Shallow slope failures in clays as a result of decreased evapotranspiration subsequent to forest clearing
Authors: Eigenbrod K D , Kaluza D
Published: April 2011

In the Kaministiquia River valley near Thunder Bay, Ontario, shallow ground movements are common on the grassy slopes, whereas the forested slopes generally appear stable. These slope failures may be the result of a rise in the groundwater table due to forest clearing and a subsequent reduction in evapotranspiration. Slope movements on one of the grassy slope in the valley have been monitored and examined since 1989. An explanation as to the cause of these slope failures is presented in this paper.Key words: shallow ground movements, fractured clay, deforestation, evapotranspiration.
Design implications of analytical and laboratory studies of permanent abandonment plugs
Authors: Akgün Haluk , Daemen Jaak JK
Published: April 2011

We analyze analytically and numerically the stress distribution along the plug-rock interface and within an axially loaded plug emplaced in a borehole in rock. Experiments show that the interface strength increases with decreasing plug radius and with increasing plug length. Axial strength decreases as a power law of plug radius. An increase in the modulus ratio (ratio of plug modulus to rock modulus) increases the interface strength, until it levels off at a ratio of about 5.0. For short plugs, the tensile stresses may reach a magnitude significant to be of concern for long-term stability of the plug and of the host rock. Our studies suggest designing friction plugs with a length to radius ratio of at least 8.0. In practice, especially for short-term performance, e.g., emergency flood control or temporary diversions, a ratio of 8.0 may not be necessary or justified. For permanent abandonment plugs, it is essential to reduce the tensile stresses in the plug and in the host rock to a level that will minimize the risk of long-term deterioration. We recommend in situ experiments on larger diameter plugs to assess the validity of the proposed size effect extrapolation obtained in this study.Key words: borehole plugging (sealing), shaft seal design, plug-rock interface strength, axial strength, bond strength, cement grout.
Norman Wells pipeline settlement and uplift movements
Authors: Nixon JF (Derick) , Burgess Margo
Published: April 2011

The Norman Wells oil pipeline has been operating successfully since 1985. The pipe was designed to operate as an ambient-temperature pipeline and accommodate up to 0.8 m of thaw settlement in inorganic terrain. The pipeline has settled close to this amount in some areas, without excessive straining of the pipe. An average thaw strain for the soil back-calculated from the thaw depth and resulting thaw settlement at several sites gives average values of 16-20%. At one location (kilometre post 5.2), the pipeline has experienced uplift of 1.1 m or more. The mechanism for pipe movement is likely a combination of high axial stresses and some small initial frost heave, which triggered uplift buckling of the pipe. Low-density thawed soils contributed to this behavior. An internal profiling device (Geopig) has been run through the pipe in recent years. Analysis of the profiles indicates excellent agreement with manual surveys at the site. The pipe is experiencing about 0.3% bending strain in the uplift zone, and about 0.4% strain in a settling area immediately to the north. Pipe strain analysis using a structural model indicates that about 0.2 m of frost heave would be required to initiate uplift buckling over a critical heave length of 22-25 m.
Overall volume change, water volume change, and yield associated with an unsaturated compacted loess
Authors: Chen Zheng-Han , Fredlund D G , Gan Julian K-M
Published: April 2011

This paper presents the overall volume change, water volume change, and yield associated with an unsaturated, compacted, low-plasticity loess from China. Two types of tests were conducted using a modified triaxial apparatus, namely isotropic compression tests with controlled suction (ICT), and triaxial shrinkage tests (TST). In the triaxial shrinkage tests, the net cell pressure is controlled and suction is allowed to increase. The results show that the stress path has a significant effect on overall volume change and the water volume change. The soil parameters related to overall volume change and the water volume change for the isotropic compression tests vary significantly in the low suction range, whereas the same soil parameters related to the triaxial shrinkage tests exhibit gradual changes. The yield net mean stress for the loading-collapse yield curve increases with suction. The yield suction is not equal to the maximum suction experienced by the soil specimen for the suction increase yield locus. Based on the test data obtained from the low-plasticity loess, a modified criterion for yield associated with suction increase is proposed. The proposed modified yield criterion should be valid for loess and silts of similar densities and plasticities.
Three-dimensional consolidation of fine-grained sediments
Authors: Dewhurst David N , Cartwright Joseph A , Lonergan Lidia
Published: April 2011

Current theories of one- to three-dimensional consolidation are based on the concept of gravitational loading with concomitant expulsion of pore fluid as a result of mechanical rearrangements of particles and porosity reduction. However, the recent discovery of extensive networks of layer-bound fractures forming polygonal patterns in extremely fine grained smectitic clays and chalks suggests that current theory may not adequately explain the consolidation process in such sediments. These faults develop during shallow burial and often appear to have been active at the sediment-water interface. Radially isotropic strain suggests that the process of formation was nontectonic. Measured values of strain suggest that deformation resulted from volumetric contraction of the sediments. We argue that the formation mechanism for these fault systems is related to the colloidal properties of the constituent sediments and that, as such, stresses due to gravity may not be the only factor controlling pore-fluid expulsion during consolidation.Key words: polygonal faults, clay, smectite, shrinkage, colloidal.
Magnitude and frequency of rock falls and rock slides along the main transportation corridors of southwestern British Columbia
Authors: Hungr O , Evans S G , Hazzard J
Published: April 2011

The two main transportation corridors of southwestern British Columbia are subject to a range of rock slope movements (rock falls, rock slides, and rock avalanches) that pose significant risks to road and rail traffic travelling through the region. Volumes of these landslides range from less than 1 m3to over 4.0 × 107m3. A database of rock falls and slides was compiled for rail and highway routes in each transportation corridor using maintenance records spanning four decades. The records number approximately 3500, of which about one half includes information on volume. Magnitude - cumulative frequency (MCF) relationships were derived for each corridor. A scaled sampling procedure was used in part to reduce the effects of censoring. Both corridors yield MCF curves with significant linear segments on log-log plots at magnitudes greater than 1 m3. The form of both railway and road plots for each corridor shows similarity over several orders of magnitude. The slope of the linear segments of the curves depends on geological conditions in the corridors. Temporal histograms of the data show a trend towards reduction of rock fall frequency as a result of rock slope stabilization measures, implemented during the 1980s and 1990s. A risk analysis methodology using the slope of the magnitude-frequency relationship is outlined. The major part of the risk to life in the case examined results from rock falls in the intermediate-magnitude range (1-10 m3).Key words: rock fall, rock slide, landslide hazard, risk, magnitude-frequency, British Columbia.
Oedometric and water-retention behaviour of highly compacted unsaturated smectites
Authors: Al-Mukhtar M , Qi Y , Alcover J -F , Bergaya F
Published: April 2011

This paper summarizes the findings from an experimental program concerning the hydromechanical behavior of two smectite clays tested under high stresses. Increasing axial stress on the smectite samples under controlled relative humidity (suction) leads to collapse in the soil structure and increases the degree of saturation. Irreversible volume change is observed in samples tested under cyclic suction with constant axial load. Water-retention (adsorption and desorption) behavior of the smectite clays tested in this study is affected by particle size, initial void ratio, and confinement conditions during the tests. Laponite, which has a large specific surface area, tends to hold more water than hectorite at a given relative humidity. More water is adsorbed by samples compacted at lower axial stress.Key words: smectite clays, hydromechanical stresses, behavior, relative humidity and suction, water retention, degree of saturation.
Evaluation of geotechnical property variability
Authors: Phoon Kok-Kwang , Kulhawy Fred H
Published: April 2011

To evaluate geotechnical variability on a general basis that will facilitate the use of reliability-based design procedures, it is necessary to assess inherent soil variability, measurement error, and transformation uncertainty separately. The inherent variability and measurement error are addressed in a companion paper, and transformation uncertainty is addressed herein. A second-moment probabilistic approach is applied to combine these uncertainties consistently based on the manner in which the design soil property is derived. The design properties considered in this paper are undrained shear strength, effective stress friction angle, in situ horizontal stress coefficient, and Young's modulus. This paper concludes with specific guidelines on the typical coefficients of variation for these common design soil properties as a function of the test type and the type of correlation used.Key words: transformation uncertainty, undrained shear strength, friction angle, in situ horizontal stress coefficient, Young's modulus, geotechnical variability.
Measurement of shear-wave velocity using phase-sensitive detection techniques
Authors: Blewett J , Blewett I J , Woodward P K
Published: April 2011

The development of a phase-sensitive technique to measure the velocity of shear waves propagating through a sand sample situated inside a standard laboratory triaxial testing cell is reported. The technique shows an improvement in convenience and efficiency over conventional time-of-flight methods, facilitating real-time display of shear-wave velocity during testing. The purpose of this paper is to demonstrate the technique by determining the variation in shear-wave velocity during triaxial testing of a loose sand. Key words: shear-wave velocity, phase-sensitive detection, drained shear.
Prediction of the hydraulic conductivity of clays using the electric double layer theory
Authors: Achari Gopal , Joshi R C , Bentley L R , Chatterji S
Published: April 2011

A model to predict the hydraulic conductivity of consolidated clay, simulating clay liners compacted wet of optimum, is presented. The concept that clays exist as clusters and the electrical double layer theory are used to predict the hydraulic conductivity of clays for permeants of known composition. The model relates the physical properties of clays, such as its surface area, with the overburden pressure and the concentration of ions in the permeant. The model can be used to predict the hydraulic conductivity of bentonitic clays with monovalent as well as divalent exchangeable cations. The model is valid within the range of applicability of the Gouy-Chapman electric double layer theory. The variation in the number of clay particles per cluster with the consolidation pressure and concentration of ions in the permeant has been discussed. The model has been calibrated and verified using published experimental data. However, the model in its present form is valid only for homoionic clays and permeants with the same valency. With an increase in concentration of ions in the permeant, the precision of the model has been found to decrease. Key words: clay, clusters, hydraulic conductivity, double layer, model, permeant, concentration.