bluuebunny/crossref_metadata_2025 huggingface dataset:
A new socket roughness factor for prediction of rock socket shaft resistance
Authors: Seidel J P , Collingwood B
Published: April 2011

Prediction of rock socket shaft resistance is a complex problem. Conventional methods for predicting the peak shaft resistance are typically empirically related to unconfined compressive strength through the results of pile load tests. It is shown by reference to international pile socket databases that the degree of confidence which can be applied to these empirical methods is relatively low. Research at Monash University has been directed at understanding and then modelling the complex mechanisms of shear transfer at the interface between the socketed piles and the surrounding rock. Important factors that affect the strength of pile sockets have been identified in laboratory and numerical studies. With a knowledge of the effect of these factors, the reasons for the large scatter around traditional empirical correlations can be deduced. A computer program called ROCKET has been developed which encompasses all aspects of the Monash University rock socket research. This program has been used to develop design charts for rock-socketed piles based on unconfined compressive strength and a nondimensional factor which has been designated the shaft resistance coefficient (SRC). Implementation of the SRC method in design requires an estimate of the likely socket roughness to be made. Very few researchers or practitioners have measured socket roughness, so there is little available guidance in selection of appropriate values. Although many socket load tests are described in the technical literature, the physical parameter which is regularly missing is the socket roughness. With a knowledge of the shaft resistance, and an estimate of all other relevant parameters, the authors have been able to back-calculate the apparent socket roughness using the SRC method. Based on the back-calculated roughness data, socket roughness guidelines for use in analysis and design of rock sockets have been proposed. Using these roughness guidelines, it is shown that the SRC method is able to predict the scatter observed in previously published international load test databases.Key words: rock socket, drilled shaft, shaft resistance, roughness, shaft resistance coefficient.
Laboratory studies on fracturing of low-permeability soils
Authors: Alfaro Marolo C , Wong Ron CK
Published: April 2011

Hydraulic and pneumatic fracturing have been used to improve the effectiveness of most in situ remediation methods for contaminated sites underlain with unfavorable low-permeability soils. This paper presents results of a laboratory experimental investigation to characterize the mechanisms related to the initiation pressure and growth of fractures stimulated from vertical and horizontal wells. The mechanisms of fracture in low-permeability soils appeared to be of a tensile failure mechanism enhanced by the generation of pore pressure as the soil around the well was being sheared due to the radial-tangential stress difference imposed by the injected pressure. The impacts of initial fracture slots on fracture orientation and initiation pressure were also investigated. The test results have demonstrated that the presence of initial fracture slots could reduce the injection pressure required to initiate fracture in the well. The initial slot, however, did not necessarily control the orientation of the propagating fracture. The effect of imposed stresses in the soil was evaluated also and was found to influence the orientation and propagation of fracture. Smaller stress contrast favored multiple deviated fractures, whereas larger stress contrast favored distinct fractures.Key words: soil fracturing, laboratory test, low-permeability soil, fracture propagation.
Snow avalanche impact pressure - vulnerability relations for use in risk assessment
Authors: Keylock Christopher J , Barbolini Massimiliano
Published: April 2011

Use of formal risk analysis to assess avalanche danger is currently limited by a lack of knowledge of how avalanche impact pressures damage structures and cause fatalities. That is, the vulnerability component of risk is poorly specified. In this paper we outline a method for deriving vulnerability values as a function of position downslope for a range of avalanche sizes. The method is based on the weighted average of vulnerability and uses an avalanche-dynamics model embedded within a statistical framework. The models seem to behave in a consistent manner. By allowing avalanche size and stopping position to vary and calculating vulnerability as a function of distance from the stopping position, vulnerability values are less approximate than the assumption of a constant vulnerability value for each individual size. When the assumptions underlying the impact pressure - vulnerability relation are perturbed, the results seem to be robust. The method outlined here should provide a way for avalanche experts to reformulate danger zones based on return period and impact pressure so that they are set within a risk framework.Key words: risk, vulnerability, snow, avalanches, impact pressure.
Nonequilibrium consolidation model for pressured shale layers
Authors: Sen Zekai
Published: April 2011

A simplified mathematical model is developed for fluid migration as a separate phase in the consolidation process due to sedimentation. The consolidation mechanism is presented and the sedimentation ratio is related to the consolidation of shales. The model is composed of simple differential equations which relate the mass balance equation to the linear fluid flow law and pressure increment. In the derivation of equations the fluid and shale compressibilities are taken into consideration. In addition, the shale porosity decrease with depth is included in the consolidation equations. These equations are converted into dimensionless standard forms, which are universally valid for any fluid migration or shale consolidation calculations. The equations are solved numerically by the finite difference method, and the results are presented as graphs referred to as type curves. These type curves are simple tools for those who do not want to be concerned with the mathematical aspects but are interested particularly in quantitative answers concerning the fluid-migration and consolidation processes.Key words: consolidation, dimensionless length, fluid migration, nonequilibrium, shale.
Consolidation modelling of soils under the test embankment at Chek Lap Kok International Airport in Hong Kong using a simplified finite element method
Authors: Zhu Guofu , Yin Jian-Hua , Graham James
Published: April 2011

This paper models consolidation of the foundation soils under a test embankment at the new Chek Lap Kok International Airport in Hong Kong. The modelling used a simplified finite element method and material parameters derived from results in the original site investigation report. Various features that need to be considered in applying the simplified method are illustrated through this case study. Good predictions of settlement results are obtained. Relatively large discrepancies in pore-water pressure predictions suggest that the nonlinear nature of hydraulic conductivity needs to be taken into account when large compressions are likely to occur. Geological conditions are shown to be a key factor in successful modelling of consolidation behaviour.Key words: consolidation, pore-water pressure, case modelling, finite element method, vertical drains, settlement.
Dual role of microcracks: toughening and degradation
Authors: Rao G M Nagaraja , Murthy C RL
Published: April 2011

One of the methods of improving the mechanical properties of ceramics is to introduce a defective structure that acts as a restraint for the propagation of cracks. In the present study a detailed investigation was carried out by introducing a defective structure in rock to determine if there is any improvement in properties similar to ceramics. Granite was chosen for the investigation, and the microcracks were introduced by a heating and cooling cycle. Uniaxial compression tests have shown that granite thermally treated to 200°C shows the highest strength, and the strength of granite treated to 400°C is comparable to that of unheated granite. Both ultrasonic images and acoustic-emission monitoring show that for thermally treated samples the stress-induced microcrack and macrocrack nucleation and their growth are retarded. The variations in mechanical properties are explained based on the concept of toughening and degradation. Uniaxial compression tests on unheated and thermally treated granite samples have clearly established the dual role of microcracks, which operate in the toughening and degradation mechanisms.Key words: thermal treatment, microcrack, inelastic strain, ultrasonic C-scan imaging, acoustic emission, toughening.
Modeling the viscoplastic behaviour of clays during consolidation: application to Berthierville clay in both laboratory and field conditions
Authors: Kim Yun Tae , Leroueil S
Published: April 2011

To analyze the effects of strain rate and viscoplastic strain on consolidation of natural clay, this paper presents a nonlinear viscoplastic model in which viscoplastic behaviour is modeled by a unique effective stress (σ'v)  viscous strain (εv)  viscous strain rate (ε·v) relationship. The proposed model can consider the effects of strain rate and viscoplastic strain on consolidation, to take into account the difference in strain rate between laboratory and field conditions, and the combined processes of generation and dissipation of pore pressure during consolidation. This model can also predict the behaviour of clay during stepwise loading, constant rate of strain, and relaxation of effective stress. The predicted values using numerical analysis are compared with measured values in laboratory tests and in situ, under an embankment built on soft clay at Berthierville, Quebec. It is possible to estimate the consolidation behaviour of natural clay with reasonable accuracy using the proposed nonlinear viscoplastic model.Key words: consolidation, soft clay, strain rate, viscoplastic, relaxation.
Mechanical improvement and vertical yield stress prediction of clayey soils from eastern Canada treated with lime or cement
Authors: Tremblay Hélène , Leroueil Serge , Locat Jacques
Published: April 2011

The method of soil stabilization is well known and has been used throughout the world for many decades to improve some soil properties. Although many researchers have studied the effect of adding a cementing agent to a soil, not many of these researchers have explored the effect of treatment on the resulting properties of high water content soils like dredged material. Also, there has been little work concerning the prediction of the mechanical changes to the soil. Therefore, this paper summarizes the results of a research project conducted to define the general mechanical behavior of high water content clayey soils from eastern Canada treated with lime or cement, in terms of compressibility. In the light of this research, the general compressibility behavior has been obtained, defined by relationships between initial void ratio, additive content, and vertical yield stress for a given inorganic or organic soil. These relationships have been normalized on the basis of the one-dimensional compression curve of the remolded and reconstituted untreated soil to give a simple method for predicting the vertical yield stress of a treated soil for any initial void ratio and its resistance to compression.Key words: stabilization, compressibility, yield stress, clayey soils, lime, cement.
The cavity expansion problem for the interpretation of cone penetration and pressuremeter tests
Authors: Cudmani R , Osinov V A
Published: April 2011

This paper presents a method of evaluation of the state of cohesionless soil from the results of cone penetration and pressuremeter tests. This method is based on the comparison of the solutions to the cylindrical and spherical cavity expansion problems obtained by the authors with experimental results available in the literature on cone penetration and pressuremeter tests in large calibration chambers. The solutions to the cavity expansion problems are obtained with the use of a constitutive equation of hypoplasticity calibrated for the same soils as in the experiments. The pressure-expansion curves from pressuremeter tests are compared with those calculated for the expansion of a cylindrical cavity. The relation between the cone resistance measured in cone penetration tests and the limit pressure calculated for a spherical or a cylindrical cavity is established through a shape factor. Soils with similar granulometric properties are found to exhibit a common shape factor as a function of the pressure-dependent relative density. Key words: cone penetration test, pressuremeter test, cavity expansion, hypoplasticity
Modified Cam-Clay modelling of temperature effects in clays
Authors: Graham J , Tanaka N , Crilly T , Alfaro M
Published: April 2011

The Cam-Clay model for isothermal mechanical behaviour of clays has been extended to take account of the effects of temperature on stressstrain behaviour. The assumptions used in constructing the new model are based on published results and on new data presented in the paper. The model allows prediction of how heating and cooling affect volume changes, pore-water pressures, and strengths for both normally consolidated and overconsolidated saturated clays. It permits modelling of observed reductions in the overconsolidation ratio with increasing temperature. The model provides accessible qualitative explanations for temperature effects that were previously difficult to understand. It will also allow easy implementation for quantitative modelling in triaxial stress fields. Results predicted by the model are compared with data collected by the authors at temperatures up to 100°C. The model does not account for changes that occur in clay minerals at higher temperatures, for example, in bentonites at temperatures higher than about 150°C.Key words: clay, triaxial, temperature, modelling, elasticplastic, Cam-Clay.
Oxidation of mine tailings from Rankin Inlet, Nunavut, at subzero temperatures
Authors: Meldrum J L , Jamieson H E , Dyke L D
Published: April 2011

Acid-generating sulphidic tailings from a NiCu mine were exposed on the shores of Hudson Bay for 30 years before burial in a drained bedrock basin. To determine if encapsulation in permafrost will maintain the tailings, and their saline pore water, in a chemically inert state, a field and experimental program was employed. Three years after burial, several boreholes were drilled to collect tailings and pore-water samples and to initiate long-term thermal monitoring. Columns charged with pyrrhotite-bearing, unsaturated tailings were studied at temperatures between +30°C and 10°C. Oxygen consumption was measured directly to determine the effect of low temperatures on oxidation rate. Results of the column experiments indicate that significant oxidation of the Rankin Inlet tailings occurs at +30°C, but at lower temperatures this rate is substantially reduced. At 10°C, unfrozen water was still present in the columns, but oxygen consumption was below the detection limit. The highest measured oxygen flux correlates with a temperature increase of 1°C, consistent with exothermic sulphide oxidation reactions. Thermal modeling and direct measurements have shown that the freezing of the tailings in Rankin Inlet is progressing. The tailings are expected to be ice-bonded approximately 15 years after burial.Key words: acid mine drainage, permafrost, tailings, reclamation, sulphides, oxidation
The variability of root cohesion as an influence on shallow landslide susceptibility in the Oregon Coast Range
Authors: Schmidt K M , Roering J J , Stock J D , Dietrich W E , Montgomery D R , Schaub T
Published: April 2011

Decades of quantitative measurement indicate that roots can mechanically reinforce shallow soils in forested landscapes. Forests, however, have variations in vegetation species and age which can dominate the local stability of landslide-initiation sites. To assess the influence of this variability on root cohesion we examined scarps of landslides triggered during large storms in February and November of 1996 in the Oregon Coast Range and hand-dug soil pits on stable ground. At 41 sites we estimated the cohesive reinforcement to soil due to roots by determining the tensile strength, species, depth, orientation, relative health, and the density of roots [Formula: see text]1 mm in diameter within a measured soil area. We found that median lateral root cohesion ranges from 6.823.2 kPa in industrial forests with significant understory and deciduous vegetation to 25.694.3 kPa in natural forests dominated by coniferous vegetation. Lateral root cohesion in clearcuts is uniformly [Formula: see text]10 kPa. Some 100-year-old industrial forests have species compositions, lateral root cohesion, and root diameters that more closely resemble 10-year-old clearcuts than natural forests. As such, the influence of root cohesion variability on landslide susceptibility cannot be determined solely from broad age classifications or extrapolated from the presence of one species of vegetation. Furthermore, the anthropogenic disturbance legacy modifies root cohesion for at least a century and should be considered when comparing contemporary landslide rates from industrial forests with geologic background rates.Key words: root strength, cohesion, landslide, debris flow, land use, anthropogenic disturbance.
Design charts for vertical drains considering construction time
Authors: Zhu Guofu , Yin Jian-Hua
Published: April 2011

This technical note presents design charts for use in determining the required drain spacing explicitly using free strain assumption. The influence of time-dependent loading is incorporated in the design charts. The design procedure is also described. When the radius of vertical drain, required degree of consolidation, time available, and pertinent geotechnical engineering properties of a soil are given, the charts can be used to design a vertical drain system without unnecessary trial and error processes.Key words: consolidation, vertical drain, design charts, time dependence, drainage.
Comparison of six surfactants in removing toluene and trichlorobenzene from a sandy soil under laboratory conditions
Authors: Lee Dal-Heui , Cody Robert D , Hoyle Blythe L
Published: April 2011

The effectiveness of four food-grade and two industrial surfactants to remove toluene or 1,2,4-trichlorobenzene added to an Iowa soil was evaluated in batch and column experiments. One of the anionic food-grade surfactants, disodium n-hexadecyl diphenyloxide disulfonate (Dowfax 8390), was more effective than the other surfactants in shaken batch experiments. The maximum recoveries of the added toluene (57%) or 1,2,4-trichlorobenzene (71%) were obtained with one surfactant wash plus two water rinses. Dowfax 8390 also yielded the highest recovery of toluene (75%) or 1,2,4-trichlorobenzene (83%) in columns of soil flushed with 1250 mL of 4% surfactant solutions. Synergism in a mixture of 2% Dowfax 8390 (anionic) and 2% T-Maz 60 (nonionic) did not occur, in contrast to enhanced recoveries exhibited by a similar mixture of the two industrial surfactants, Sandopan JA36 (anionic) and Pluronic L44 (nonionic).Key words: surfactants, toluene, 1,2,4-trichlorobenzene, recoveries, synergism.
Performance of a test embankment constructed on an organic clayey silt deposit
Authors: Rowe R Kerry , Gnanendran C T , Valsangkar A J , Landva A O
Published: April 2011

The instrumentation, construction, and field performance of a full-scale test embankment constructed on a soft compressible organic clayey silt is described. The construction sequence, the observed vertical and horizontal displacements, and the pore pressure response are presented. The embankment behaved elastically up to a thickness of about 3.65 m. The settlement and heave responses suggested that the embankment approached failure at a thickness of about 6.1 m and a corresponding net height of 5.4 m. The failure was gradual and of a viscoplastic type, and no classical-type abrupt failure was encountered during the construction of this embankment. The height to which the embankment could be constructed was lower than the 711.4 m range expected from conventional two-dimensional (2D) limit equilibrium analysis based on vane strength data. This, coupled with the pore pressure response, suggests that a combination of progressive failure and the influence of the adjacent reinforced section constructed to failure may have been significant factors affecting the performance of this embankment. Thus, the data reported in this paper can be used as a test case for developing three- dimensional (3D) analysis methods wherein the constitutive model can be truly tested for 3D conditions involving the interaction between embankment sections that are constructed under different conditions.Key words: embankment, field behaviour, stability, deformations, pore pressures.
Combined effects of reinforcement and prefabricated vertical drains on embankment performance
Authors: Li Allen Lunzhu , Rowe R Kerry
Published: April 2011

The behaviour of geosynthetic-reinforced embankments constructed over soft cohesive soils installed with prefabricated vertical drains (PVDs) is investigated by numerically examining an embankment constructed over different foundation soils. The partial consolidation during embankment construction, the consequent shear strength gain of the foundation soil, and the effect of the use of reinforcement on the mobilization of shear strength are examined. It is shown that the combined use of reinforcement and PVDs can significantly increase embankment stability and potentially allow the rapid construction of higher embankments than could be achieved with either method of soil improvement alone. Construction rate and spacing of PVDs can significantly affect the degree of consolidation at the end of construction and the stability of the embankment. For the situation examined, the effect of well resistance of typical vertical drains is insignificant. A relatively simple method for calculating the degree of consolidation and the strength gain of the foundation soil during construction is evaluated based on finite element results and is shown to be reasonably conservative. A design procedure is proposed to combine the design of reinforcement and PVDs.Key words: soft clay, prefabricated vertical drain, reinforcement, embankment stability, consolidation, strength gain.
Strain Energy and Behaviour of Overconsolidated Soils
Authors: Brooker Elmer W
Published: April 2011

Bjerrum recently presented a strain energy hypothesis which explains qualitatively the behaviour of overconsolidated clays and the phenomena of long-term slope failures in these soils. Quantitative evidence, gathered from a series of large-scale consolidation tests, is presented here which supports the strain energy hypothesis. The coefficient of earth pressure at rest was found to be a function of strain energy at a given value of OCR. It is also shown that the degree of disintegration of overconsolidated soils during a slaking test is related to strain energy. It is inferred from the results that mineralogy and the capacity of a soil to adsorb strain energy are related. The evidence suggests that certain physico-chemical properties may be quantitatively related to mechanical properties through the concept of strain energy.
Unusual Movements of Abutments Supported on End-Bearing Piles
Authors: Stewmac A G , Devata M , Selby K G
Published: April 2011

This paper presents a study of a number of unusual abutment movements that have occurred at seven underpass structures on the Macdonald-Cartier Freeway between Cornwall and the Quebec border. The locations of these structures are shown in Figure 1. The movements were of such magnitude at three of the structures that extensive repair work has been necessary.An explanation for these unusual abutment movements is presented. Remedial measures are suggested and measures are outlined to avoid the occurrence of such movements in areas where comparable subsoil and loading conditions would prevail.
DESIGN OF FOUNDATIONS ON WINNIPEG CLAYS
Authors: Baracos A.
Published: April 2011

Case histories are given to illustrate bearing capacity, settlement, and volume changing characteristics of Winnipeg clays. These clays are of glacial lake origin, highly plastic, and generally irregularly varved. I have endeavored to show by calculation the relationship between soil properties determined by tests, and the behavior of the supported structure.
Groundwater flow in eastern Ottawa
Authors: Jarrett P. M. , Eden W. J.
Published: April 2011

A mile-long line of piezometers were installed at various depths in a clay terrace system east of the City of Ottawa. Measurements indicated a significant downward piezometric gradient through the clay layer to the underlying bedrock. The downward flow of water through the clay affects both existing effective stresses and the stress history of the clay deposit.
Deep Excavations for the Manufacturers Life Centre, Toronto
Authors: Prasad G. D. , Freeman C.F. , Klajnerman D.
Published: April 2011

Geotechnical considerations associated with deep excavations for the Manufacturers Life Centre in Toronto are discussed. The depth to shale bedrock and the necessity to obtain maximum access to the foundation grade resulted in selecting the use of tie backs into the overburden with or without rakers for supporting the soldier pile lagging system. Full scale load tests were carried out to prove the recommended geotechnical design parameters for the shoring system. Adhesion values obtained from full scale field tests on tie backs agreed closely with the shear strength obtained from laboratory quick triaxial tests. However a full scale loading test on an inclined raker footing gave a higher bearing value compared with conventional design procedures.
Analytical Study of a Braced Excavation in Weak Clay
Authors: Palmer J. H. La Verne , Kenney T. Cameron
Published: April 2011

Analysis of the problem of braced excavations is complicated by the large number of variables involved and by the complex interaction and behavior of the soil and the supporting materials. For this reason a parametric study was made using the finite-element method of analysis to evaluate the influences of the variables. A rather unique computer modelling technique has been used to accommodate both the large number of variables and the problem of interaction and dissimilar behavior. An example of a computer simulation of a well-instrumented braced cut in Norway is given in sufficient detail to illustrate the applicability of the program.For the parametric study a typical excavation with fully penetrating sheet-pile walls was chosen. Of the parameters concerning soil conditions, the soil deformation modulus was found to have the greatest influence. The relative influence of shear strength, of initial in situ stress, of direction of mobilization of shear stress, and of soil-to-pile adhesion is also shown. All of the parameters concerning support conditions are important but pile stiffness and effective strut stiffness are the most important. The influence of prestressing and strut spacing is also shown.
The Prediction of Permafrost Thicknesses
Authors: Judge Alan
Published: April 2011

With a knowledge of the mean annual ground temperatures, the general lithology at a given location and a regional distribution of the geothermal flux from the earth's interior, it is possible to make reasonable estimates of the presence or absence of permafrost and its thickness. The prediction is complicated by changes of the local surface temperature in the past due to a variety of factors ranging from changes of climate to forest fires.
Excess Pore Pressures During Undrained Clay Creep
Authors: Holzer Thomas L. , Höeg Kaare , Arulanandan Kandiah
Published: April 2011

The objective of this presentation is to examine experimentally how the excess pore-water pressure is related to the mechanism for undrained creep of San Francisco Bay mud. The results are discussed in the context of creep mechanisms previously suggested in the literature and based on laboratory testing.It is found that shear strains occurring during undrained creep are directly related to a gradual but significant increase in excess pore pressure and, hence, reduction in effective stresses. The increase in magnitude of the pore pressure is, except immediately after the creep shear stress is applied, solely a function of the initial consolidation stress and consolidation period. The magnitude of the long-term build-up may be related to the amount of secondary compression which would occur during drained conditions. It increases with the organic content of the soil and decreases with the degree of remolding. The mechanism for the increase in pore-water pressure may be explained by drainage of water from micropores in the microstructure into the macrostructure.Unless one accounts for the increase in pore pressures during undrained creep, it is unlikely that one will be successful in formulating a generally valid mathematical model for stress–strain–strength–time behavior based on laboratory testing.
Sedimentation in Glenmore Reservoir, Calgary, Alberta
Authors: Hollingshead A. B. , Yaremko E. K. , Neill C. R.
Published: April 2011

Glenmore Dam on the Elbow River in the City of Calgary was constructed in 1932 in connection with Calgary's water supply. Various surveys have been conducted over the years to record the progress of sedimentation in the 23 000 acre-foot (28.4 × 106 m3) reservoir. It is estimated that in the 36 year period to 1968, nearly 10% of the original full-supply capacity was lost due to silting. The average composition of deposits is estimated as 35% sand, 50% silt and 15% clay sizes.The quantity of accumulated deposits checks reasonably with estimates of sediment load in the Elbow River, which rises in the eastern slopes of the Rocky Mountains approximately 65 miles (105 km) southwest of Calgary. An apparent average sediment yield of approximately 240 tons per square mile per year (84 tonnes/km2/year) from this 470-square-mile (1217-km2) basin is compared with yield data from other points in Western Canada and the northwestern United States.
Measured Contact Pressures Below Raft Supporting a Stiff Building
Authors: Eden W. J. , McRostie G. C. , Hall J. S.
Published: April 2011

Contact pressures between supporting clay and the foundation raft of a very stiff, 15-storey building indicate that pressures near the edge of the raft were up to three times those near the center. This condition persisted over a 2-year period. The difference in pressure is discussed in the light of the stiffness of the building. The raft design method suggested by an A.C.I. Committee in 1966 is compared with the measured performance and found to be reasonable for the raft itself but questionable for the foundation wails above the raft.
Ultimate Bearing Capacity of Footings on Sand Layer Overlying Clay
Authors: Meyerhof G. G.
Published: April 2011

The ultimate bearing capacity of footings resting on subsoils consisting of two layers has been investigated for the cases of dense sand on soft clay and loose sand on stiff clay. The analyses of different modes of soil failure are compared with the results of model tests on circular and strip footings and some field observations of foundation failures.
Réactivité de roches carbonatées aux alcalis du ciment
Authors: Durand Marc , Berard Jean
Published: April 2011

To detect their potential reactive behavior in concrete 94 carbonate rocks from twelve Montreal area quarries were studied. Expansion tests performed on 588 samples kept in various environments for a period of 4 years revealed three main types of behavior:(a) some limestones and dolomites expanded over 0.1% in alkaline solutions (1 M NaOH and 1 M KOH): they were classed as 'reactive';(b) other rocks with a high content of insolubles showed expansion in pure water; they were considered as 'swelling';(c) most rocks showed no expansion at all. They were classed as 'inert'.A compositional study showed the composition leading to a potential reactive behavior: the reactive carbonates contained between 5 and 30% insolubles, part of which consists of disseminated clay in an aphanitic matrix. The determination of pore-size distributions allowed a more precise comparison of reactive and nonreactive rocks of the same composition: the carbonates having an important volume of small pores (<1 μm) are less reactive than those possessing a closed structure. In the latter, the active clay hydrates only when the alkalis attack dolomite and provide access for water.
Theoretical Synthesis and Analysis of Strong Motion Spectra of Earthquakes
Authors: Hasegawa H. S.
Published: April 2011

A comparison of theoretical Fourier amplitude spectra of strong ground motion (FS) with the corresponding spectra of real earthquake accelerograms is useful in elucidating the physical processes that contribute significantly to the ground motion signal. At low freqencies the contribution from surface waves tends to predominate. At intermediate frequencies the joint contributions from the direct shear wave and from complex crustal reverberations are important. At high frequencies the attenuation factor and/or source mechanism effects tend to dominate, depending on type of material and distance traversed.For a specified ground motion spectra and a particular acceleration response level, there are many theoretically predicted smoothed response spectra for velocity and displacement, depending on the particular combination of earthquake magnitude and source-to-receiver distance selected. In contrast the Newmark–Hall method (for nuclear reactor facilities) predicts a single value for the velocity and displacement response level when the acceleration response level is specified; the Newmark–Hall response values for velocity and displacement are somewhat greater than the corresponding maximum theoretically predicted values. Much of this difference is likely due to the fact that, in the theoretical spectra used for comparison purposes, contributions from complex crustal reverberations and from surface waves were not included.
Measurement of soil arching above a large diameter flexible culvert
Authors: Lefebvre Guy , Laliberté Maurice , Lefebvre Liguori M. , Lafleur Jean , Fisher C. L.
Published: April 2011

The paper reports on the measurement of an arching effect over a large diameter flexible culvert. An arch shape culvert, 51 ft (15.5m) in span, was erected and covered by a 44 ft (13.4m) high embankment. An extensive instrumentation program was laid out in order to check the mobilization of an arching effect during construction by measuring displacements, earth pressures, and stresses in the steel. The instrumentation data indicated that a large portion of the load due to the weight of the soil above the structure was transferred to the adjacent area.
On quasi-static solutions for buried pipes in permafrost
Authors: Hwang C. T.
Published: April 2011

A review of the existing quasi-static methods of analysis used for predicting the thaw bulb around a buried pipe in permafrost has been made. The quasi-static solutions are compared with the results obtained by numerical techniques so that the accuracy of the approximate method can be examined. Consequently, a modification to the approximate method is suggested to improve its applicability to preliminary engineering design.
Pollutant migration from two sanitary landfill sites near Sarnia, Ontario
Authors: Goodall D. C. , Quigley R. M.
Published: April 2011

Contamination profiles below two youthful landfills founded on thick silty clay deposits near Sarnia, Ontario were obtained by squeezing pore water from Shelby tube samples and analyzing this water by absorption flame photometry for Ca++, Mg++, Na+, and K+. Pollution fronts were observed below both sites, the contaminant cation concentrations attenuating with distance to normal background values.The older landfill was about 7 years old, was founded at 5.6 m depth below the weathered crust on intact silty clays, and was characterized by a downward flow gradient from the base of the fill. Pollution (cation) migration had proceeded downwards for a distance of 30 cm compared to the calculated maximum possible advance of the seepage front of only 4 cm.The younger landfill was about 2.5 years old, was founded at 2.3 m depth within the crust on weathered and fissured soils, and was characterized by upward flow into the landfill due to heavy loads created by the large mound of waste. Pollution migration had proceeded for a distance of 50–80 cm opposite to the prevailing direction of seepage flow and is presumed to have occurred along well developed fissures in the soil.At both sites the diffuse pollution fronts are attributed to cation (chemical) diffusion which, in the early stages of both landfills, has overwhelmed seepage flow.
Design of a loading platen for testing ice and frozen soil
Authors: Law K. T.
Published: April 2011

A critical review of the problems associated with the design of an ideal platen for uniaxial loading tests is presented. A method of design based on an analytical approach is then formulated. The method permits a liberal choice of material for constructing the platen, which consists mainly of a low modulus plug confined in a metallic ring. A finite element approach has been employed to substantiate the proposed method. Practical design aspects are also discussed.
The correlation of index properties with some basic engineering properties of soils
Authors: Wroth C. P. , Wood D. M.
Published: April 2011

Experimental evidence is produced to show that it is reasonable to assign a unique strength to all soils when at their respective liquid limits, and to redefine the plastic limit as the water content at which the strength is 100 times that at the liquid limit. Combining these assumptions with ideas of critical state soil mechanics it is then possible to relate the compression index of the remoulded soil to its plasticity index, and to suggest a unique relation between remoulded strength and liquidity index, irrespective of actual values of liquid and plastic limits. Field data from the Gulf of Mexico and from the North Sea are presented in support of these relations. The predictions of strength are best for overconsolidated clays, having water contents near the plastic limit.Recently in the United Kingdom the cone penetrometer has become the recommended test for determination of the liquid limit, in preference to the Casagrande test. Having redefined the plastic limit it would be logical to use the cone penetrometer to determine this too, by using cones with different weights. Experimental data are shown to illustrate and support this proposal.
Control of artesian pressure by bleeder wells
Authors: Wade N. H. , Taylor H.
Published: April 2011

Deep test bleeder wells were installed in an artesian aquifer underlying the Bridge River No. 1 hydroelectric generating station in southern British Columbia to determine whether seasonal peak artesian pressures could be controlled.The Bridge River complex, built in the early 1950's, consists of two powerhouses located about a kilometre apart on the shore of Seton Lake, a system of power tunnels, and surface penstocks, which conduct water from the Carpenter Lake reservoir in Bridge River valley to the powerhouses. The No. 1 powerhouse is founded on consolidated deposits of clayey silt, underlain by sand and gravel. Shortly after the powerhouse was constructed, ground and powerhouse movements occurred. It was later determined that such movement was caused by high artesian pressures in the sand and gravel aquifer under the powerhouse.Attempts to install bleeder wells in 1952 were unsuccessful and an offshore fill was constructed as a toe weight, which functioned adequately until 1974 when additional ground cracking was observed. After further study and additional drilling at the site, test bleeder wells and piezometers were installed in 1976.Tests conducted to assess the effect of the bleeder wells indicated that control of excessive artesian pressures by a system of bleeder wells was feasible.
Groundwater regime associated with slope stability in Champlain clay deposits
Authors: Lafleur Jean , Lefebvre Guy
Published: April 2011

Slope stability analyses in terms of effective stresses are most often based on hypothetical conditions of pore pressure. It is generally assumed that the flow occurs parallel to the slope or even that the conditions are hydrostatic. In fact, in situ measurements tend to show that the real situation could significantly deviate from these approximations due to geologic conditions. The influence of various geometric and stratigraphic factors on the groundwater regime and on the stability of slopes was studied with the finite-element method. To illustrate the parametric study, experimental evaluations of the flow patterns are presented at four sites. The stratigraphy and permeability measurements combined with the finite-element method enabled a complete flow net to be drawn and although some hypotheses had to be formulated with regards to the underlying aquifer recharge or permeability anisotropy, reasonable agreement was found between simulated and measured piezometric heads.
Design of shallow rock-anchored foundations
Authors: Ismael Nabil F.
Published: April 2011

Full-scale uplift and lateral load tests were carried out on rock anchors and rock-anchored foundations at several sites in the Province of Ontario. Various rock types were tested, ranging from soft shale to sound limestone. The results are presented; they were analyzed and important design parameters were determined for different rock formations. Based on test results, simplified design procedures were developed for the convenience of the design engineer. Keywords: Anchors, rock, transmission lines, foundations, tests, loads, design criteria, uplift pressure.
Slope stability in residual soils in Hong Kong
Authors: Sweeney D. J. , Robertson P. K.
Published: April 2011

A large number of steep, high cut slopes in residual soils exist in Hong Kong and many failures of such slopes have occurred, almost invariably during heavy rainfall. As a result, the long-term stability of many cut slopes is now in question.A brief review of past slope design and slope failure is presented.It has been found that the effective stress shear strength envelope of the Hong Kong soils is curved, particularly at low stress levels, and angles of friction are high. Shear strength results are presented from a series of multistage, consolidated drained, triaxial tests carried out on a typical decomposed Hong Kong granite residual soil. The results of the multistage tests are reviewed to assess the applicability of this type of test to residual soils.The importance of the curved shear strength envelope is discussed in relation to the observed slope failures.
Field frost heave predictions using the segregation potential concept
Authors: Nixon John F.
Published: April 2011

The Konrad–Morgenstern theory of frost heave using the segregation potential concept is briefly outlined, and the method of predicting frost heave under field conditions is reviewed. A recent paper by Nixon et al. describes the operation and results from two circular frost heave test plates installed at the Foothills Pipe Lines test facility in Calgary. The frost heave theory using the segregation potential approach has been applied in its simplest form to predict the frost heave beneath these test plates and the agreement is found to be very good. Current geothermal modelling, coupled with the Konrad–Morgenstern theory of frost heave, appears to be capable of reasonable predictions of frost heave in fine-grained soils under practical engineering conditions.
Deficient pore pressures in an eroding soil mass
Authors: Koppula Sivajogi D. , Morgenstern Norbert R.
Published: April 2011

The pore pressure response of a semi-infinite, fully saturated soil mass of finite thickness eroded at a constant rate is examined. Using Terzaghi's classical consolidation theory, an expression is derived for the deficient pore pressure as a function of depth and time. The resulting equation is mildly nonlinear with a moving top boundary. Closed form analytical solutions are obtained for various bottom boundary conditions and are presented in nondimensional quantities. The results indicate that the development of deficient pore pressures is dependent on (i) the rate of soil removal; (ii) the swelling potential of the soil mass; (iii) the ratio of the thickness of soil layer(s) removed to its original thickness; and (iv) the nature of the bottom boundary. Substantial negative pore pressures are likely to persist in the residual mass, even close to the eroded surface, although free water is made available at the top. The plots presented in this paper will be helpful for ascertaining the erosion–swelling characteristics of a soil mass that has been or is being eroded. Examples are presented to illustrate the development and dissipation of deficient pore pressures due to swelling. Keywords: constant rate, deficient pore pressures, depth factor, dredging, erosion–swelling ratio, isochrones, Laplace transform, moving boundary, swelling.
Earthflows in the Interior Plateau, southwest British Columbia
Authors: Bovis Michael J.
Published: April 2011

Examples of large, slow-moving earthflows from the western part of the Interior Plateau zone of British Columbia are discussed, the larger examples exceeding 107 m3. The study provides a regional framework for previous, site-specific work on the geotechnical properties of earthflows in this region. Factors responsible for earthflow development are (1) low shear strength claystone, shale, and siltstone units within, principally, middle Cretaceous to Eocene sediments and volcanics; (2) steep topographic gradients at the plateau margins, plus availability of tributary valley incisions to provide lateral confinement of earthflow debris; (3) sufficient moisture surplus at the plateau level to cause seasonal fluctuations in piezometric head, both within and beneath earthflow debris. So far, work on the Holocene record of movement suggests (1) relatively modest earthflow activity during the warm, dry period of the first 3000 years or so of postglacial time; (2) a post-Mazama maximum of movement, probably correlated with the onset of cooler, moister conditions; (3) following this, a progressive decrease in the area of actively moving debris on most flows. Key words: earthflow, Holocene mass movement, earthflow morphology, slope movement.
An approximate method for estimating the stability of geotextile-reinforced embankments
Authors: Rowe R. K. , Soderman K. L.
Published: April 2011

A method of estimating the short-term stability of reinforced embankments constructed on a deposit that can be idealized as being uniform and purely cohesive is described. This approach maintains the simplicity of conventional limit equilibrium techniques while incorporating the effect of soil–geotextile interaction in terms of an allowable compatible strain for the geotextile. This allowable compatible strain may be deduced from a design chart and depends on the foundation stiffness, the embankment geometry, the depth of the deposit, and the critical height of an unreinforced embankment. The procedure is checked against finite element results and against one published case history. Key words: embankment, geotextile, analysis, limit equilibrium, finite element, soft clay, shear strength, soil reinforcement.