bluuebunny/crossref_metadata_2025 huggingface dataset:
Extreme avalanche runout: a comparison of empirical models
Authors: McClung D M
Published: April 2011

The prediction of snow avalanche runout distances and the probability of exceeding the predicted positions is the first and most important step required before making decisions about placement of facilities or control structures in snow avalanche prone terrain. There are two main prediction methods for calculating runout distances: (1) procedures linked to the selection of friction coefficients in avalanche dynamic models, and (2) empirical, statistical prediction based on terrain parameters for a set of extreme runout distances for the mountain range in question. Within the second method there are presently two competing empirical approaches to prediction: (i) ordinary least squares regression analysis related to angles measured for the path profile in question, and (ii) extreme value prediction of runout based on a Gumbel distribution of a dimensionless terrain parameter. In this paper a comparison of the two empirical methods with emphasis on the slope steepness in the runout zone is provided. The comparison is important, since the choice of method does affect the probability of the runout position being exceeded, particularly far into the runout zone where facilities are most likely to be located. The analysis shows that comparison of the models hinges on slope steepness in the runout zone and differences in calculating exceedance probabilities from the distributions used in the analysis (Gumbel distribution and Gaussian). The method based on the dimensionless Gumbel parameter provides more conservative predictions for flat terrain in the runout zone, and the regression - least squares method is more conservative for steep terrain in the runout zone. In addition, the Gumbel method is shown to be compatible with the characteristics of runout zone slope steepness shown by field data: there is very little dependence of runout distance on runout zone slope steepness.Key words: snow avalanche, runout, empirical methods, statistical methods.
A note on Rayleigh wave velocity in saturated soils with compressible constituents
Authors: Yang Jun
Published: April 2011

The problem of Rayleigh waves in a semi-infinite saturated soil medium is reconsidered in this study, with the purpose of clarifying existing confusion and limitations of available studies. By employing Biot's general formulation, which takes into account not only the compressibility of the solid and fluid constituents but also the viscous dissipation due to fluid flow, the secular equation for Rayleigh waves is rigorously derived and the velocity of Rayleigh waves is computed for several typical types of saturated soils. The results show that the velocity of Rayleigh waves in general is independent of frequency in the frequency range actually employed in engineering practice and is only slightly less than the shear wave velocity. The results confirm that current understanding of Rayleigh wave velocity achieved based on the classical theory of elasticity is acceptable and indicate that some results in the literature are incorrect.Key words: Rayleigh wave velocity, saturated soil, porous media, wave propagation, analytical method.
Statistical assessment of soil-water characteristic curve models for geotechnical engineering
Authors: Sillers W Scott , Fredlund Delwyn G
Published: April 2011

A number of empirical equations have been proposed for the soil-water characteristic curve. A nonlinear, least squares method was used to determine best-fit parameters for several empirical equations that were best-fit to 230 water content versus soil suction data sets. In addition, two proposed correction methods to accommodate high soil suctions up to 1 000 000 kPa were applied to the various soil-water characteristic curve equations. The data sets of water content versus soil suction were arranged into one of the USDA soil classifications based on their relative amounts of sand, silt, and clay (only eight soil classifications had sufficient data for later analysis). The quality of fit for each model was compared using the Akaike Information Criterion. A series of conclusions were arrived at regarding (i) the relationship between two- and three-parameter equations, (ii) the relationship between exponential and sigmoidal type equations, and (iii) the value of correction factors for the high soil suction range.Key words: soil-water characteristic curve, unsaturated soil, soil suction, regression analysis, SWCC models, Akaike Information Criterion.
Liquefaction performance of soils at the site of a partially completed ground improvement project during the 1999 Chi-Chi earthquake in Taiwan
Authors: Lee Der-Her , Juang C Hsein , Ku Chi-Sheng
Published: April 2011

This paper examines the liquefaction performance of soils at the site of a partially completed ground improvement project at the Chang-Hwa Coastal Industrial Park during the 1999 Chi-Chi earthquake in Taiwan. The site is on land reclaimed by hydraulic filling. To meet the need of a planned construction, site characterization was carried out with standard penetration tests (SPTs) and cone penetration tests (CPTs) at 13 locations. Dynamic compaction was later performed to mitigate the potential liquefaction hazards at this site. Before completion of the ground improvement work, the site experienced a major earthquake, the Chi-Chi earthquake (magnitude Mw = 7.6). Evidence of liquefaction was observed in this earthquake in the unimproved area but not in the improved area. After the earthquake, additional site exploration was carried out using SPTs and CPTs. The data from these in situ tests carried out before and after the earthquake and in areas with and without ground improvement are analyzed and the results are reported.Key words: ground improvement, in situ tests, liquefaction, earthquake.
Earth Pressures at Rest Related to Stress History
Authors: Brooker Elmer W , Ireland Herbert O
Published: April 2011

The influence of stress history on the coefficient of earth pressure at rest of remoulded cohesive soils was studied experimentally. A one-dimensional compression test cell and auxiliary controls which enabled the measurement of radial stresses under a condition of zero lateral strain was developed for this purpose. Radial pressures were measured throughout all stages of consolidation up to a maximum axial stress of 2,200 psi and subsequent rebound to zero stresses.Five cohesive soils, the properties of which are well documented, were selected for this study. These soils were: Chicago Clay, Goose Lake Flour, Weald Clay, London Clay, and Bearpaw Shale. 'The selected soils range in plasticity from low to high and cover a range of drained angles of shearing resistance from 15.5 degrees to 27.5 degrees. For testing purposes all soils were remoulded at a liquidity index of 0.5.For a pre-consolidation load of 2,200 psi and various values of the over-consolidation ratio, it was found that the coefficient of earth pressure at rest is related to both the drained angle of shearing resistance and the plasticity index. The coefficient of earth pressure at rest during rebound was found to be a function of the stress history of the soil as defined by the pre-consolidation load and over-consolidation ratio.
Shrinkage of Soil Samples with Varying Clay Concentration
Authors: Jong E De , Warkentin B P
Published: April 2011

The influence of texture on shrinkage was studied for samples prepared in the laboratory to have varying proportions of Leda clay and glass beads. Total shrinkage and moisture content at the shrinkage limit increased linearly with the percentage of clay as long as the clay formed a continuous matrix. At lower clay concentrations shrinkage decreased rapidly. Total shrinkage per unit weight of clay in the mixtures increased with decreasing clay content, because the clay in parallel orientation around glass beads had a higher moisture content than the remainder of the clay.
Desiccation of Soil by Trees Related to Foundation Settlement
Authors: Perpich William M , Lukas Robert G , Baker, Jr. Clyde N
Published: April 2011

A number of case histories are presented in which damage to structures supported on shallow foundations in the Chicago area have occurred due to desiccation. Particular emphasis is placed on the soil properties at each site, proximity of trees and root systems, surface run-off characteristics, and climatic factors. Also included is a discussion of the process by which trees cause desiccation and of some general rules to minimize this problem, as well as a discussion of means of arresting settlements of existing structures affected by desiccation.
BEHAVIOR OF AN OVERPASS CARRIED ON FOOTINGS AND FRICTION PILES
Authors: Brzezinski L. S.
Published: April 2011

A long overpass structure with 32 piers between abutments was founded on strip footing and friction pile foundations in a deep marine clay subsoil of firm consistency. The piles were steel H-sections which were provided at the construction stage at 6 pier locations in lieu of footings because of unfavorable soil conditions exposed during excavation. A load test to failure on a single pile indicated the pile–soil adhesion to be considerably lower than the undrained shear strength of the clay.Post-construction observations indicated the settlement of the pile-supported piers to be about 50% that of the adjacent footing supported piers. The settlements of both types of foundations were small and within tolerable limits. The design approaches used for prediction of footing settlements and the group action of friction piles in bearing capacity and settlement are presented in the paper.
CONSOLIDATION OF LAYERED CLAYS
Authors: Barden Laing , Younan N. A.
Published: April 2011

The experimental behavior of remolded layered clays undergoing both one-dimensional vertical flow and three-dimensional combined vertical and radial flow is shown to be in close agreement with exact solutions formulated in terms of Terzaghi theory. The accuracy of a number of approximate solutions for layered clays is assessed, confirming the importance of the interface flow condition.
Frost heaving forces in Leda Clay
Authors: Penner E.
Published: April 2011

The frost heaving forces developed under a 1 ft (30.5 cm) diameter steel plate were measured in the field throughout one winter. The steel plate was fixed at the ground surface with a rock-anchored reaction frame. Heave gauges and thermocouples were installed at various depths to determine the position and temperature of the active heaving zone.The general trend was for the surface force to increase as the winter progressed. When the frostline approached maximum depth the force was in excess of 30 000 lb (13 608 kg). Estimates of the heaving pressure at the frostline ranged from 7 to 12 psi (0.49 to 0.84 kg/cm2) during this period.The variation of surface heaving force was closely associated with weather conditions. Warming trends resulting in a temperature increase of the frozen layer caused the forces to decline.
Thaw–Consolidation Tests on Remoulded Clays
Authors: Morgenstern Norbert R. , Smith Laurence B.
Published: April 2011

A general solution to the problem of one-dimensional thaw–consolidation has been formulated by Morgenstern and Nixon (Can. Geotech. J. 8, p. 558, 1971). In order to assess the validity of the theory it was necessary to develop a special oedometer (permode) which could impose the necessary thermal and stress boundary conditions for one-dimensional thaw–consolidation.The permode permits the measurement of settlements, temperatures at various depths on the side of the sample, and excess pore pressures at the base of the sample during thaw–consolidation.Controlled thaw–consolidation tests were carried out on three types of remoulded clays. The resulting data showed that the excess pore pressures and the degree of consolidation in a thawing soil depend primarily on the thaw–consolidation ratio. The results obtained demonstrate that the theory adequately represents the soil behavior. Applications of the theory in practice are indicated.
Rational Design Criteria for Protective Filters
Authors: Thanikachalam V. , Sakthivadivel R.
Published: April 2011

A review of the existing design criteria for protective filters indicates that for a given cohesionless base soil gradation of the filter material is not uniquely determined. From an analysis of available experimental results of filter tests, two equations are proposed for stable design of protective filters for cohesionless base soils. The proposed equations take into account the gradation of the base material and provide two points on the gradation curve of the filter material (the 10 and the 60% sizes) as upper limits. These equations may be useful for checking the maximum gradation of a filter to protect a cohesionless base soil.
Uplift Forces on Foundations in Frost Heaving Soils
Authors: Penner Edward
Published: April 2011

Field studies of uplift forces by frost heaving are described for columns of various types and sizes and for a block concrete wall. The changing ground surface heave pattern around the block wall was used to predict the maximum heaving force which compared favorably with the measured value.Unit adfreeze strengths and maximum uplift forces were highest for steel columns, followed by concrete and wood; the lowest values were for the block concrete wall. In general, unit adfreeze strengths were highest for the small diameter columns and lowest on the largest columns. Differences are ascribed to the response of the various materials to air temperatures and to the shape and size of the structure.
Downdrag Loads Developed by a Floating Ice Cover: Field Experiments
Authors: Frederking R.
Published: April 2011

The first phase of an investigation of the vertical forces developed on a structure by a floating ice cover frozen to it is described. It is the objective of this work to develop the theoretical, experimental, and field aspects of vertically acting loads required for the more efficient design of structures subject to such loads. A load frame was constructed that would apply constant upward acting loads to wooden piles frozen into an ice cover composed mainly of snow ice. Load, ice temperatures, and movement of the pile in relation to the ice were measured.The time-dependent movement of the pile in relation to the ice exhibited creep characteristics, and these results were related to shear creep for grouted rod anchors in permafrost. Results of a previous study for WF steel H-beams in ice were also considered. The steady-state creep displacement rate for wooden piles in ice, rod anchors in permafrost, and WF steel H-beams in ice exhibited a comparable dependence on the constant applied shear stress. The steady-state creep displacement rate of a 100-mm wooden pile in snow ice at −3 °C and under a constant applied shear stress of 180 kN/m2 was about 1 mm/day.
Geotechnical Implications of Pleistocene Deposits in Southern Saskatchewan
Authors: Sauer E. Karl
Published: April 2011

Significant advances in understanding Pleistocene stratigraphy have provided a new framework for geotechnical investigations in southern Saskatchewan. In Saskatchewan, three formal stratigraphic groups have been recognized in the Pleistocene based on the concept of multiple glaciation. The engineering significance of this stratigraphic framework has now been established.Some of the geotechnical problems in Saskatchewan, related to Pleistocene deposits include slope instability, problems associated with groundwater, location of gravel aggregates, and excavating and handling embankment materials. It can now be demonstrated that these problems are fundamentally related to Pleistocene stratigraphy. Examples are included to illustrate this approach.The analysis of these deposits requires special criteria to establish the true stratigraphic column in terms of reference sections. It has been shown that the reference sections can be extended over very large areas of the region. The principal investigation technique involves the use of rotary drilling and geophysical logging which has proven to be extremely effective when properly interpreted. The criteria used for establishing the stratigraphy are described and examples included. The possibility exists that this approach to investigating geotechnical problems in Pleistocene deposits may extend to other parts of Canada.
Major rock slides in the Rockies
Authors: Cruden D. M.
Published: April 2011

The Frank Slide is the best known of a number of major rock slides in the Canadian Rockies. Seven other slides of the same order of magnitude are described from the Front and Main Ranges between Jasper and the United States border.The geometry and kinematics of the slides are controlled by discontinuities in the rock slide mass. Typically, the major part of the rupture surface is parallel to bedding; the orientation of the lateral margins and the scarp of the slide may be controlled by joint sets.Sliding tends to occur on slopes where bedding dips towards valleys at angles between 30 and 40° and in thickly-bedded, massive weathering rocks such as quartzites, dolomites, and limestones. Major causes of sliding appear to be erosion at the foot and lateral margins of the slide mass.The slides may be easily identified on aerial photographs by their effect on the local vegetation and by the characteristic appearance of their debris. All the slides observed are post-glacial, their frequency seems to have been underestimated and, in places, they may impose major constraints on further development.
A survey of the Canadian strong motion seismograph network
Authors: Rogers Garry C.
Published: April 2011

At the end of 1974 there were 45 accelerographs and 75 seismoscopes deployed in Canada. The Department of Energy, Mines, and Resources and the National Research Council of Canada have installed most of the instruments but one quarter of them are privately owned. Three quarters of the instruments are located near the west coast with the next largest concentration in the St. Lawrence Valley region. There is one instrument in the Arctic. The majority have been deployed to measure ground motion in populated areas but a few have been deployed in areas of higher seismicity remote from population centers. In western Canada particular emphasis has been placed on measuring the response of different soil types and soil depths. The only major structures in the country that have been instrumented are two large dams.
The computer simulation of frost penetration beneath highways
Authors: Smith M. W. , Tvede A.
Published: April 2011

A computer simulation model which uses weather data as the time-variable surface boundary condition and employs a finite-difference solution to the heat conduction equation gives predictions of frost penetration beneath highways with a maximum error of 15%. The pattern and timing of freezing and thawing are also well reproduced. Further, the model is shown to be capable of reliable and consistent results using limited input data, already quite widely available. The simulated use of styrofoam insulation is shown to reduce maximum frost penetration by 45%, a value in good agreement with observation.
Caractéristiques géotechniques du secteur du Parc Olympique, Montréal
Authors: Ballivy Gerard , Loiselle André , Durand Marc , Poirier Michel
Published: April 2011

Under natural conditions, the western limit of the Olympic Park site along Sherbrooke Street is formed by a terrace of marine clay deposited in the Champlain Sea. This terrace has an average height of 60 ft (18 m) and overlies shallow fine grained deposits of fluvio–glacial or glacial origin, which are encountered at ground surface in the eastern part of the site. The bedrock, of Ordovician age, is part of a monoclinal structure which dips at 3° to 5° towards the northeast; bedding planes and vertical fractures form the main planes of discontinuity. The surficial part of the bedrock has been strongly disturbed by the action of glaciers during the Wisconsin glaciation: a displaced rock slab now covers the main part of the site and has greatly affected the design of the foundations for the various structures.Geotechnical investigations carried out by the City of Montreal on or near the site for earlier tunneling projects were used to establish a geotechnical map of the Olympic Park site. Based on this map, the foundation elevations for the different buildings, the type of earth supporting structures, and the geometry of cut slopes could be selected. Along Sherbrooke Street, 70 ft (21 m) deep excavations were necessary in an area where lateral movements could not be tolerated. Consequently a program for monitoring the cast-in-place diaphragm retaining wall and the slopes was carried out by the City of Montreal with the participation of the Ecole Polytechnique de Montréal.

[Journal translation]
Bearing capacity of piles in layered soils. Part 2. Sand overlying clay
Authors: Meyerhof G. G. , Sastry V. V. R. N.
Published: April 2011

The previous Part 1 of this paper deals with the bearing capacity of piles penetrating through clay into sand. In the present Part 2 the case of piles penetrating into a sand stratum overlying clay is discussed. As the pile points approach the sand–clay interface, the piles may fail by punching through the sand into the underlying clay. Test results on instrumented model piles and field data are analysed to estimate the punching resistance of piles in layered soils.
Characteristics of natural slopes in the Athabasca Oil Sands
Authors: Dusseault Maurice B. , Morgenstern Norbert R.
Published: April 2011

The Athabasca Oil Sands are largely within the McMurray Formation, which is a transgressive blanket quartz sand of Lower Cretaceous age. Millennia of erosion have resulted in extensive exposures of oil sand along river valleys in the vicinity of Fort McMurray. Study of these slopes has contributed to understanding the nature and behavior of oil sands. Oil sand slopes with active toe erosion are characteristically high and steep (up to 70 m at slopes over 50°), have an indurated outer face and display a stress–relief exfoliation joint system that controls slope recession phenomena. Bitumen does not contribute mechanically to slope stability. The major agents affecting slope morphology are the lithology, the aspect and the basal stratigraphy. Ravelling along exfoliation fractures is the major failure mode, block falls are a minor failure mode and rotational landslides have not been observed. Remolded oil sand may flow viscously, but intact oil sand displays an unusually high strength.
Shear strength of Athabasca Oil Sands
Authors: Dusseault Maurice B. , Morgenstern Norbert R.
Published: April 2011

Previously published data are inadequate to explain the high natural shear strength of oil sand. Dissolved gas comes out of solution when confining stresses are removed rapidly, and this results in an internal pressure that expands the oil sand specimens disrupting their fabric. Geophysical logs indicate that in situ densities are much higher than those determined from conventionally cored specimens.Although the behavior of slopes in oil sands suggests that the shear strength is high, the source of strength of the oil sand has not been explained. Therefore detailed oil sand strength testing was undertaken on samples obtained in a special manner. Down-hole refrigeration of cored sections resulted in relatively high-quality specimens, and these were shaped on a lathe to provide triaxial and shear-box test samples.Strength tests on dense Ottawa sand, oil sand tailings and densely recompacted oil sand were performed: standard behavior was observed throughout. A series of triaxial and shear-box tests on undisturbed oil sands demonstrated a Mohr failure envelope that is highly curved, which displays no cohesion intercept and which is extremely steep for the initial portion of the envelope. Optical and scanning electron microscope investigations have revealed a dense interpenetrative structure and a considerable degree of grain surface rugosity. These factors give rise to a very high dilation rate before failure, and the dilation rate is suppressed as normal stress increases. The suppression of dilation results in shear of grains and grain asperities, giving rise to an apparent cohesion intercept at higher normal stresses. The curvilinear failure envelopes may be conveniently expressed as power-law relationships, and this form of expression will prove useful in stability analysis.
Deformability of joints and its relation to rock foundation settlements
Authors: Hungr O. , Coates D. F.
Published: April 2011

This study explores several aspects of the 'discontinuous' approach to prediction of settlements of foundations on jointed rock. The first part presents the results of experiments with numerical and analytical solutions. It is shown that solutions of continuum elasticity cannot be used without introducing errors due to method alone, which could be serious for sensitive structures.The second part of the study describes measurements of joint stiffness on samples of natural joints in limestone and sandstone. Normal and shear stiffness coefficients were measured. It was found that the unit shear stiffness coefficient varies greatly with displacement, and an empirical relationship was derived that might be useful in analysing other rocks.
Vane testing in peat
Authors: Landva A. O.
Published: April 2011

An extensive programme of vane testing has been carried out in a peat bog at Escuminac, N.B. to assess the applicability of vane testing to peat. The variables involved in the programme were depth, size of vane, method of insertion, rate of rotation of the vane, and state of peat tested. Vane strength profiles were obtained in a 7 m thick deposit consisting of sphagnum peat (0–4 m), sphagnum carex peat (4–6 m), and carex sphagnum peat (6–7 m). Vane tests were also carried out in the sphagnum peat under anchored Plexiglas sheets to observe the mode of deformation and failure and to measure the movement of markers inserted into the face of the peat. Additional tests were carried out with field vanes in confined sphagnum peat samples in the laboratory.The observed failure surface was essentially cylindrical for all sizes of vane used, but its diameter was consistently 7–10 mm greater than that of the vane for all vane sizes. The sphagnum peat failed at true angles of rotation of between 17 and 40°, leaving a void behind each blade. At maximum torque the peat within each sector started to move monolithically.The moderately decomposed sphagnum moss peat tested is typically neither fibrous nor amorphous, although some fibres and amorphous material are generally present as a result of varying growth and degradation processes. This type of peat could be considered representative of most moss peats with respect to geotechnical behaviour. It is not, however, representative of the less common, truly fibrous sedge peats or of any purely amorphous peat deposits.Analyses of the mode of deformation of the sphagnum peat in vane shear and comparisons with modes of deformation in other types of shear have led the author to conclude that the vane test, in spite of its practical advantages, does not serve any useful purpose in the testing of peat.
Remarks on the validity of stability analyses
Authors: Tavenas F. , Trak B. , Leroueil S.
Published: April 2011

This paper presents a critical review of the analytical methods of slope stability analysis.The effective stress methods of analysis surfer from four fundamental weaknesses related to the magnitude of the effective stresses, the assumed stress path, the indiscriminate use of a Mohr–Coulomb criterion, and the definition of the factor of safety. As a result the quality of the computed factors of safety must be questioned.Practical consequences as well as alternative solutions for the analysis of stability of slopes or foundations are discussed.
The effect of groundwater flow on the stability and design of retained excavations
Authors: Kaiser P. K. , Hewitt K. J.
Published: April 2011

The groundwater flow pattern around the retaining structures of deep excavations affects the resultant water pressure, the active and passive earth pressure, and the piping and bulk heave potential. A published case history involving a hydraulic failure of a 15 m deep, temporary sheet piled excavation is analysed. The soil profile, assuming the same excavation geometry, is subsequently altered and analysed by numerical and simplified models of flow patterns. A detailed discussion of the results is used to develop generally applicable design concepts and to illustrate the limitations of simplifications. It is suggested that partial factors of safety should be applied to each load component and it is shown that the assumption of homogeneous, isotropic soil conditions may lead to unsafe designs. Furthermore, it is concluded that the hydrostatic boundary conditions, as well as the possibility of anisotropic permeability at depth and particularly below low permeability layers, must be considered in the design of deep excavations.
Development of a quasi-static piezocone apparatus
Authors: Roy Marius , Tremblay Michel , Tavenas François , Rochelle Pierre La
Published: April 2011

The European Symposium on Penetration Testing (ESOPT) held in Stockholm in 1974 has contributed to the improvement of interpretation methods and also to the standardization of the cone penetration test (CPT). In recent years, the importance of the pore pressures generated during cone penetration has led to the development of new sounding equipment to measure this parameter in addition to the usual cone penetration parameters.The apparatus developed at Université Laval consists of a conical tip equipped with a filter in order to measure pore pressure and cone resistance simultaneously during the penetration. In addition, since the conical tip is detachable, five types of tips were used in the study in order to vary easily the position of the pore pressure pick-up and to study the pattern of pore pressures generated at or behind the cone tip.The results show that the filter arrangement has a significant effect on the registered magnitude of excess pore pressure. The generated pore pressures are highest when they are measured in the failure zone of the intact clay, i.e., when the filter arrangement is located on the conical part of the tip.
Soil volume changes induced by temperature cycling
Authors: Demars K. R. , Charles R. D.
Published: April 2011

The effects of temperature cycling on the volume change behavior of soil is examined during isotropic consolidation tests in the laboratory. Tests are performed on six different natural marine samples which vary from a sand to a clay of high plasticity. Samples are subjected to a heating and cooling cycle of 25 °C at constant confining stress in both normally consolidated and overconsolidated stress ranges. Results of this investigation indicate that the permanent reduction in void ratio due to a temperature cycle of 25 °C is independent of the effective confining stress for a normally consolidated soil. This permanent void ratio reduction is shown to be a unique value for a given normally consolidated soil and is directly related to soil plasticity. For overconsolidated soil, the effect of temperature cycling on volume change behavior is shown to be a function of the magnitude of effective stress decrement or overconsolidation ratio.
The analysis and prediction of lateral instability in highly stressed, near-surface rock strata
Authors: Roorda J. , Thompson J. C. , White O. L.
Published: April 2011

The potential for lateral instability of highly stressed, near-surface sedimentary rocks such as the Paleozoic deposits of southern Ontario and western New York State is investigated analytically. The minimum magnitude of the in-situ stress required for a pressure ridge to form is easily computed once values are obtained for the stratum thickness and short-term Young's Modulus, the weight of overburden, and the residual friction with the over- and underlying material. Consideration is also given to the increased likelihood of instability associated with excavations of different widths and depths. Keywords: rock, excavations, quarries, instability, pressure ridges, mechanisms.
Locating the frozen–unfrozen interface in soils using time-domain reflectometry
Authors: Baker T. H. W. , Davis J. L. , Hayhoe H. N. , Topp G. C.
Published: April 2011

The time-domain reflectometry technique was compared with the temperature measurement method for locating the frozen–unfrozen interface in water and sandy soils. This technique depends on the high-frequency (1–1000 MHz) electrical properties of water that change significantly and abruptly between the liquid and solid phases. Parallel wire transmission lines were inserted into the soil to guide electromagnetic pulses produced by a time-domain reflectometer (TDR). The frozen–unfrozen interface produced reflections measured by the TDR which were in turn used to locate the interface as it moved along the transmission line. In the laboratory it was possible to locate the interface using the TDR to within ±0.5 cm and in the field to within ±2.4 cm. These errors were equal to those associated with the temperature measurements. Keywords: soil freezing, temperature measurements, dielectric constant, time-domain reflectometry.
Thixotropic stiffening of clay consolidated in the laboratory
Authors: Pusch Roland
Published: April 2011

Reserve strength and brittle behaviour are characteristic of many soft clays that are normally consolidated from a geological point of view. This strength and behaviour have been assumed to result from creep processes in the course of secondary consolidation. If such strengthening is associated with creep, it should also take place in structurally disturbed clay that is left to rest under undrained as well as drained conditions, and this was investigated in the present study.Samples of natural, undisturbed as well as artificially produced clays were consolidated under a pressure corresponding to twice the preconsolidation pressure, and were then left to rest under a reduced pressure and drained conditions. After various periods of rest, the samples were sheared under undrained conditions and it was observed that the strain at failure decreased and that the shear modulus increased with the time elapsed, thus proving that thixotropic stiffening exceeded the softening due to volume increase.
Comparison of snow pressure measurements and theoretical predictions
Authors: McClung David M. , Larsen Jan Otto , Hansen Svein Borg
Published: April 2011

Measurements of snow creep pressures from the centre section of a 3.4 m high and 15 m long avalanche-defence supporting structure located on a mountain in western Norway are presented. The site has a deep snow cover and an average slope angle of 25°. The measurement configuration corresponds to plane-strain conditions and the data, along with measured snowpack parameters, allow comparison with simple theoretical predictions. The analysis shows that the average pressure on the structure may be calculated fairly accurately using linear, viscous modelling for the snow deformation. The maximum pressures proved to be higher than that provided by a linear model and this is considered characteristic of nonlinear material. The implications of these results for estimates of design loads are discussed. Keywords: snow pressure, creep, measurements, viscous, plane-strain, finite element.
The observed behaviour of a geotextile-reinforced embankment constructed on peat
Authors: Rowe R. K. , MacLean M. D. , Barsvary A. K.
Published: April 2011

The design, instrumentation, and field performance of two instrumented sections of a geotextile-reinforced embankment are described. The 1–1.5 m high embankment was constructed in three stages on top of a peat deposit that extended to depths of up to 7.6 m. The peat was highly compressible with average water contents of 445% and 785% at the two instrumented sections.A polypropylene, monofilament woven fabric (Permealiner 1195) was used to reinforce the embankment over the less compressible section of the deposit. At stage I, 1.37 m of fill resulted in settlements of approximately 1 m but only 1% transverse strain in the geotextile. At stage II, a total of 3.87 m of fill had been added with total settlements of approximately 3 m and transverse geotextile strain of 21%. Stage III construction involved bringing the embankment to final grade, with a total fill and pavement thickness of 4.2 m. Settlements at stage III were relatively small.A strong, twisted, slit film, polypropylene woven fabric (Geolon 1250) was used to reinforce the more compressible section of the deposit. At stage I, 2.74 m of fill resulted in settlements of approximately 3.1 m and transverse geotextile strains of 3%. At stage II, a total of 6.1 m of fill had been added resulting in settlements of approximately 4.6 m. At stage III, the embankment was brought to grade by reducing the fill thickness and constructing the pavement. The final fill and pavement thickness was 5.7 m.It is concluded that the use of a single layer of even a very strong geotextile was insufficient to prevent large shear deformations in these deep, compressible, peat deposits. The procedures used in the design represented the state-of-the-art at that time; however, they did not provide a good indication of how the embankment would perform in the field. It is recommended that simplified limit equilibrium design procedures should be viewed with considerable caution when designing geotextile-reinforced embankments on peat. Keywords: embankment, muskeg, peat, geotextile, settlement, pore pressures, field observation, instrumentation, soil reinforcement.
Laboratory testing and in situ behaviour of peat as embankment foundation
Authors: Lefebvre G. , Langlois P. , Lupien C. , Lavallée J.-G.
Published: April 2011

Intact block samples of fibrous peat have been obtained using special equipment from two different sites in the James Bay territory in Quebec. Instrumented test fills were subsequently built at those two sites and the observed behaviour was used to check the laboratory data. The laboratory testing program has included standard 24 h incremental tests and stage creep tests where constant loads were applied for periods of about 30 d. Pore pressure and direct permeability measurements were conducted in most of the tests.The tests have been interpreted using the classical e − log p curves or the tangent modulus approach. The evaluation of compression with time under a constant load has allowed the distinction between primary and secondary consolidation. A certain lag in pore pressure response has been observed and related to incomplete saturation. The coefficient of permeability decreases rapidly with compression as indicated by direct measurements and pore pressure dissipation.The comparison with field observation shows that the 24 h incremental oedometric compression test permits a reasonable prediction of the average settlements at the end of primary consolidation provided the lateral displacement during construction is small. It also shows that the secondary compression observed in the field is about twice what was observed in the laboratory but both show a linear relation with the logarithm of time.Keywords: peat, sampling, compressibility, consolidation, secondary consolidation, permeability, laboratory tests, field behaviour.
Heave of coal shale fill
Authors: Caldwell Jack A. , Smith Adrian , Wagner Johan
Published: April 2011

Washing plant discard, predominantly laminated and micaceous carbonaceous shale, was used as fill beneath a thick concrete floor slab. This paper discusses the cause of heave of the fill and the severe cracking of the floor slab—up to 70 mm—about a year after construction.Observation of the fill and the nature of the fill indicate that the heave is caused by absorption of water (but not clay mineral swelling) and predominantly by alteration of the sulphides in the fill to sulphates.These observations are confirmed by measurement of the chemistry of fresh washing plant discard, weathered fill, and fresh discard subjected to accelerated weathering. Oedometer tests confirm the swelling of the rocks as a result of water absorption. As these processes were still occurring, further heave was anticipated; accordingly, the fill was removed.Keywords: heave, shale, sulphide alteration, weathering, clay mineral swelling.
Influence of the groundwater on the stability of a clay bank in Baie James, Québec
Authors: Rosenberg Peter , Provençal Jacques , Lefebvre Guy , Paré J.-Jacques
Published: April 2011

The Rivière Broadback in northern Québec flows westward almost parallel to latitude 51 °N to discharge into Baie James at its southern end. Near the estuary the river banks are in clay. Surveys of the landsliding activity showed that many of the slides are superficial, with depths seldom greater than about 2 m, and are usually in the clay crust.Instrumentation revealed regional groundwater pattern close to the river banks that showed areas varying from those with significant underdrainage to those with hydrostatic pressure conditions. The stability of 26 m high river slopes inclined at 27° in an area of underdrainage was investigated.Triaxial testing on undisturbed tube samples was used to obtain the postpeak parameters. Stability analyses gave a factor of safety close to one for shallow failure surfaces. With underdrainage, the factor of safety for deep failure surfaces is appreciably higher. When hydrostatic pore pressure conditions are assumed, analysis gave a factor of safety for deep failure that was reduced by about 30%.The results of the analyses emphasize the relation between the morphology of the landslide activity and the groundwater regime. With underdrainage, effective stresses increase much faster with depth and the critical failure surface is always close to the surface, as confirmed by field observations. Key words: natural slope, clay, pore pressure, field measurements, stability failure surface, failure morphology.
Early regional photointerpretation and geological studies of landslide terrain along the South Saskatchewan and Qu’Appelle River valleys
Authors: Mollard J. D.
Published: April 2011

Experience at investigated damsites along the South Saskatchewan River in the 1950's showed the importance of interrelated studies in site investigation, geology, and airphoto interpretation. As a result of this work, landforms along the dam abutments were identified as landslide masses rather than hummocky morainal materials. The engineering implications were significant. Advanced techniques of remote sensing offer further opportunities for clarifying the role of geology in new areas of activity being undertaken by geotechnical engineers. Key words: riverbanks, damsite geology, geomorphology, airphoto interpretation, remote sensing.
Foundations of the Annacis cable-stayed bridge
Authors: Bazett D. J. , McCammon N. R.
Published: April 2011

A new highway crossing of the Fraser River at Annacis Island near Vancouver, British Columbia, is currently under construction. It involves a major cable-stayed bridge with a main span of 465 m. Support for the bridge is provided by piles driven into dense overconsolidated Quaternary sediments: on the south bank they are found essentially at ground surface while on the north (Annacis Island) side they are encountered at a depth of 80–85 m overlain by sequences of weak deltaic and alluvial materials. This paper describes the geotechnical investigation for the bridge and describes the design of six foundations including those for the two main piers. The north main pier is founded on unusually deep pipe piles about 85 m long. Key words: bridge, case history, earthquake, geological investigations, liquefaction, negative skin friction, pile, settlement analysis, site investigation.
Field measurements and analysis of a large-diameter flexible culvert
Authors: Byrne P. M. , Srithar T. , Kern C. B.
Published: April 2011

This paper describes field measurements and analysis carried out on the Elkhart Creek soil–arch culvert structure in British Columbia, Canada. The structure has a span of 13.4 m, a rise of 7.3 m, and a soil cover of 9.6 m. The original structure collapsed during backfilling in October 1987. A new structure of the same design was built in the fall of 1989, and because of controversy regarding the design thrust value, it was instrumented to measure thrust and displacements in the arch. Displacements and stresses in the soil were also measured. The measured thrust values were much lower than expected and indicated that significant positive soil arching occurred, similar to that observed at the Vieux Comptoir soil–stucture in Quebec in 1975. A nonlinear finite element analysis of the soil–structure system was carried out simulating the construction procedures used, and the computed response was compared with the measurements. The computed and observed responses were in reasonable agreement in all aspects, namely thrust, displacements, and soil stresses, provided an allowance was made for slip at the bolted connections. Key words : culvert, finite element, arching, stress, displacements.
Ice lens formation at a silt–sand interface
Authors: Smith Sharon L. , Williams Peter J.
Published: April 2011

A major experiment simulating ground freezing around a buried chilled pipeline in a controlled-environment facility provided an opportunity to examine the form and orientation of ice lenses associated with a vertical interface between silt and sand. The heave of the silt decreased towards the interface and ice lenses in the silt were found to dip at an increasing angle in the same direction. Consideration of the thermal regime suggests that the direction of heat flow influences the orientation of the lenses. The interface was irregular and ice lenses at the lower part of the interface were closely aligned to it, indicating that changes in soil texture also influence ice lens orientation. Deformation of ice lenses appears to have occurred in the silt near to the interface. The arrangement of the lenses can be explained by the different thermal properties and thermodynamic behaviour of the two materials and by the mechanical "anchorage" of the sand in which there is no ice lens formation. Cycles of freezing and thawing modify soil structure and produce cumulative residual deformations which are modified by a soil interface. Key words : frost heave, ice lenses, frozen soil, vertical silt–sand interface, chilled pipeline, differential heave.
On the paucity of amorphous minerals in the sensitive postglacial marine clays
Authors: Torrance J. Kenneth
Published: April 2011

The abundance and role of amorphous minerals in the sensitive marine clays of eastern Canada has been a subject of investigation since 1974. Unfortunately, the Segalen "selective" extraction procedure (alternating HCl and NaOH), which was used in most of the experiments, is very aggressive. By attacking both oxide minerals (which were presumed to be amorphous) and crystalline phyllosilicates, its use led to major overestimates of the possible amorphous mineral content. Less aggressive "selective" extraction procedures indicate that less than 1% of the sensitive Champlain Sea sediments is oxide minerals, and Mössbauer spectroscopy has detected only crystalline iron oxides, which are probably of detrital origin. The amount of amorphous oxide minerals is at most a small fraction of 1%. Crystalline iron oxides, in the concentrations naturally present, have been demonstrated to influence the rheology of the sensitive marine clays, but it seems improbable that the very small amounts of amorphous minerals that may be present are geotechnically important. Key words : sensitive marine clays, iron oxides, amorphous minerals, selective extraction.