bluuebunny/crossref_metadata_2025 huggingface dataset:
Down-drag on Piles in Clay due to Negative Skin Friction
Authors: Fellenius Bengt H.
Published: May 2008

In Part I of this report the results are given from 43 months of measurements of forces and bending moments on two instrumented precast piles driven through 40 m (130 ft) of soft clay and 15 m (50 ft) into underlying silt and sand. The force in the piles increased due to negative skin friction. After the first 5 months a force of nearly 40 tons was observed at the bottom of the clay layer. During this time the reconsolidation of the clay after the driving took place. The force due to the reconsolidation effect amounted to about 30 tons, while the rest was due mainly to negative skin friction caused by a small regional settlement. The latter force increased linearly with time by about 15 tons per year. Seventeen months after the driving the pile heads were loaded with 44 tons and one year later another 36 tons were added. The load on the pile head eliminated the negative skin friction, which however started to return with the continued regional settlements.In Part II of the report general design formulae for piles considering negative skin friction are given. The formulae should be used to check that the permanent and transient working loads, which have been chosen according to ordinary design rules, are not too large when negative skin friction develops.When settlements due to negative skin friction are not acceptable, the negative friction can be reduced by applying a thin coat of bitumen to the piles. References are made to investigations concerning reduction of skin friction, and practical difficulties are pointed out.
Analysis and Performance of a Braced Cut in Sand with Large Deformations
Authors: Scott J. D. , Wilson N. E. , Bauer Gunther E.
Published: May 2008

The paper is divided into two parts. The first part deals with the systematic program of measurements undertaken on an open braced cut in dense sand at the Greenway Pollution Control Centre in London, Ontario. In the second part, the experimental data are analyzed and a new solution is presented based on Dubrova's analysis, which related qualitatively and quantitatively the active earth pressure distribution to the mode of deformation of a retaining structure.The roughly L-shaped excavation measured 68 × 42 ft (20.7 × 12.8 m) for the longest leg, the other leg was 30 × 23 ft (9.1 × 7.0 m). The temporary bracing system consisted of interlocking steel sheet piles (Larssen IIIN), and wales and struts from wide-flanged steel sections. The maximum depth of the cut was 50 ft (15.2 m) below ground elevation of 722 ft (220.1 m). The soil consisted of fine uniform dense sand having a relative density varying from medium to very dense. The natural water level was approximately 20 ft (6.1 m) below the ground surface prior to construction.The instrumentation program was carried out during the 6-month construction period (January–June 1964) and consisted of measuring: (1) The strut loads with a mechanical strain indicator (Whitmore gauge) over 8 in. (20.3 cm) gauge lengths, (2) The deformation of the north wall in a horizontal and a vertical plane, (3) The water levels and water pressures from borehole and standpipe observations, and (4) The active and passive earth pressures over the cut with 'Geonor vibrating-wire pressure transducers mounted flush on two adjacent sheet piles of the north wall.Field and laboratory tests supplied the necessary soil data.Comprehensive measurements of this kind in deep cuts in sand, prior to this London investigation, had only been made in Berlin, Munich, and New York. But at London, for the first time the actual distribution of earth pressures in sand were measured on a full-scale braced wall.The analysis of the experimental data showed that the earth pressure distribution can be approximated by the extended Dubrova’s solution. The agreement between the total active earth pressure obtained from the pressure cells and the corresponding Coulomb values varied from excellent (upper bound) to good (lower bound).An experimental relationship between the horizontal soil strain and the variation of K-values over the depth of the cut was established.The different theories for predicting Ko-values do not seem to apply to over consolidated dense sand deposits. The experimental Ko-values, rather, agree with other published experimental values for similar soils.The strut load readings were somewhat erratic, not necessarily corresponding to the excavation progress. The total strut loads were lower than the corresponding forces from the earth pressure cells or the corresponding Coulomb values.
The Bearing Capacity of Rigid Piles Under Inclined Loads in Sand. I: Vertical Piles
Authors: Meyerhof G. G. , Ranjan Gopal
Published: May 2008

The bearing capacity of rigid vertical and batter piles under inclined loads in sand has been determined for model piles of different depth/diameter ratios. The first part of this paper deals with vertical piles and the second part will consider batter piles. The results of loading tests on free standing and piled foundations under inclinations of load varying from vertical to horizontal are analyzed. On the basis of plastic theory, a new approach for analysis of rigid vertical piles under horizontal loads is developed by extending Brinch Hansen's method; and previous methods of analysis by Meyerhof are extended to estimate the bearing capacity of vertical piles under inclined loads in sand. Loads on vertical piles are found to be in reasonable agreement with the proposed theories.
Design and Performance of an Expressway Constructed Over Peat by Preloading
Authors: Samson Laval , Rochelle Pierre La
Published: May 2008

This paper presents the complete record of the laboratory investigations and field observations made in conjunction with the construction of expressway embankments built by preloading over a muskeg. The peat deposit, located on the north shore of the Saint-Laurent River, was initially 10–19 ft (3.0–5.8 m) thick and is underlain by sand. Settlements of the highway fills ranging from 5 to 11 ft (1.5 to 3.3 m) were measured during construction.Laboratory and field tests were performed before and during construction. Field vane tests made at the end of the preloading stage indicated a considerable gain in the shear strength as a result of consolidation. Compressibility characteristics of the peat measured in the laboratory are compared with the field behavior.Periodical field level observations were taken during the 4 years after the removal of the temporary surcharge and have shown that the highway embankments heaved 2–3 in. (5.0–7.5 cm) over a period of 12 months at a gradually decreasing rate. The rebound was followed by long-term secondary settlements totaling 0.5–1.5 in. (1.3–3.8 cm) over the following 3 years of observations. Analysis of the settlement records shows that preloading has been beneficial in reducing the coefficient of secondary compression of the peat. Preloading was simulated in the laboratory by means of oedometer tests on peat samples; both the laboratory results and the field observations revealed a remarkable agreement between the duration of the surcharge stage and the time for rebound to be complete after removal of the surcharge.
Coupled Horizontal and Rocking Vibration of Embedded Footings
Authors: Beredugo Y. O. , Novak M.
Published: May 2008

The prediction of the coupled response to horizontal forces is of major importance for the design of footings exposed to dynamic effects. The theory of surface footings greatly overestimates the real response and neglects the fact that the footings are founded beneath the surface of the ground, i.e. partly embedded. This latter factor considerably affects the footing vibrations in that it reduces the resonant amplitudes and increases the resonant frequencies.An approximate analytical solution was developed in this paper and the theoretical response curves were compared with field experiments. Closed form formulas were obtained that are simple enough to be directly used in design. The approximate analytical solution is better able to predict the coupled response of embedded footings than that of surface footings. The response is usually dominated by the first resonant peak with the second resonant peak entirely suppressed. The derived formulas for equivalent stiffnesses and damping coefficients due to soil can be introduced into the solution of any structure.
Passive Pressure Coefficients for Sand
Authors: Shields Donald H. , Tolunay Zeki A.
Published: May 2008

Values of Kp for a horizontal bed of sand acting against a vertical wall have been computed using Terzaghi's logarithmic spiral method. The results compare favorably with other theories.
Thomas Roy and his “Remarks on road-making” (1841)
Authors: Legget Robert F.
Published: May 2008

Thomas Roy was a civil engineer and geologist who lived in Toronto from 1834 to 1842; he was probably Canada's first geotechnical engineer. In 1835 he carried out the survey for what would have been Canada's first railway if it had then been constructed. He acted as City Engineer for the fledgling city. Nothing is yet known of his life before 1834 but the search continues. In 1837 he presented to the Geological Society of London a paper on the former, raised water levels of the Great Lakes, based on his field observations while surveying. In 1841 he wrote and had published a remarkable little book on road making, in some ways far ahead of its time; significant extracts are herein presented. Key words: road building, archival, geology.
Prediction of load-carrying capacity of driven piles
Authors: Chow Y. K. , Karunaratne G. P. , Wong K. Y. , Lee S. L.
Published: May 2008

Two methods are presented to estimate the load-carrying capacity of driven piles. These methods use a new wave equation model that incorporates the loss of energy to the soil mass through radiation damping of the soil. Conventional soil parameters are used in this new model. Both methods use the load-test result of a test pile to estimate the soil parameters at the site by set matching. These soil parameters are then used to predict the load-carrying capacity of similar piles at the site in subsequent analyses from set measurements. The two methods are demonstrated by the prediction of the load-carrying capacity of 21 piles at four sites. Key words: load-carrying capacity, pile foundations, pile driving, soil setup, wave equation model.
Normalized behavior of offshore clay under uniform cyclic loading
Authors: Vucetic Mladen
Published: May 2008

A method for characterization of normally consolidated and overconsolidated clay subjected to undrained constant shear strain amplitude cyclic loading is presented and verified. The method is based on laboratory evidence that shows that clays exhibiting static normalized behavior with respect to the vertical consolidation stress, i.e., along the lines of the SHANSEP method, also exhibit a similar cyclic normalized behavior. The method is illustrated by cyclic results obtained on an offshore clay for the range of overconsolidation ratio (OCR) from 1 to 4, and is verified by predicting the initial backbone curve, cyclic stiffness degradation, and pore pressure variation for the same clay for OCR = 1.4. The predicted behavior for OCR = 1.4 successfully describes the corresponding laboratory results. Also, very consistent relationships between cyclic shear strain and other cyclic parameters obtained by means of cyclic strain-controlled testing in this and other similar studies confirm that the cyclic shear strain is probably the most fundamental parameter governing the undrained cyclic behavior of clay. Key words: clay, laboratory test, model, ocean soil, overconsolidation, soil dynamics, repeated loading, simple shear test.
Laboratory determination of diffusion and distribution coefficients of contaminants using undisturbed clayey soil
Authors: Rowe R. Kerry , Caers Chris J. , Barone Frank
Published: May 2008

This paper describes a technique for determining the diffusion coefficient and the distribution coefficient for contaminants using saturated, intact (undisturbed) clayey soil samples. The technique is illustrated with reference to a number of laboratory tests involving advective-diffusive migration of potential contaminants through an intact clayey soil from Sarnia, Ontario. An important aspect of the proposed technique is that the mass of contaminant in the system is kept constant and so significant decrease in source leachate concentration occurs during each test. A simple theoretical model is used to analyze this case and it is shown that this phenomenon can be used to deduce both the diffusion coefficient and the distribution/partitioning coefficient from a single test. Parameters are deduced for a number of salt solutions passing through the clay from the Sarnia area. On the basis of these tests it is suggested that for the Sarnia soil and advective velocities up to the maximum examined (0.035 m/a), mechanical dispersion does not measurably affect the magnitude of the "coefficient of hydrodynamic dispersion" (i.e., there is no significant dispersion). It is also suggested that the effective porosity corresponds to that deduced from the water content of the soil. Key words: contaminant migration, soil, laboratory study, experimental, analysis, diffusion, advection, clays, groundwater.
Performance of a raft foundation supporting a multistorey structure
Authors: Landva A. O. , Valsangkar A. J. , Alkins J. C. , Charalambous P. D.
Published: May 2008

A nine-storey structure was recently constructed on a raft founded on a 30 m thick layer of clayey silt at Fredericton, New Brunswick. Detailed soil investigations included conventional borings and self-boring pressuremeter, field vane, and flat dilatometer tests performed at the site. In addition to the field testing, undisturbed samples were obtained and tested in the laboratory to determine the compressibility and shear strength characteristics. To compare the performance of the foundation with the design assumptions, instrumentation consisting of piezometers, contact pressure load cells, and settlement points was installed. The instrumentation was monitored at regular intervals during the construction stage and at 6 month intervals following the completion of the building. This report presents (i) the results of the field and laboratory testing, (ii) the results of the field monitoring, and (iii) the results of a finite element computer analysis of the foundation-soil interaction. Key words: raft foundation, instrumentation, clayey silt, compressibility, soil tests, soil–structure interaction.
Deformability and consolidation characteristics of soft Bangkok clay using screw plate tests
Authors: Bergado D. T. , Chong K. C. , Daria P. A. M. , Alfaro M. C.
Published: May 2008

This study centred on the performance of the screw plate test (SPLT) to determine the deformability and consolidation characteristics of soft Bangkok clay. For comparison, a series of stress-path-controlled triaxial consolidation tests (tri) were carried out on good quality samples of Bangkok clay taken from the same testing sites and imposed with the same loading conditions as the screw plate tests. Undrained and drained moduli and coefficients of consolidation were obtained from the stress-path-controlled triaxial consolidation tests and were compared with the corresponding values of the screw plate test. In addition, the ultimate bearing capacity was derived from the pressure–deformation relationships of the screw plate test results. A graphical method was used to compute the coefficient of consolidation from the screw plate tests and from stress-path-controlled triaxial consolidation test results. The compressibility data were also obtained from conventional oedometer tests (oed). Both cv (SPLT)/cv (tri) and cv (SPLT)/cv(oed) ratios compared favorably with the cv (field)/cv (laboratory) ratio obtained from past investigations. The data from pressure–settlement–time relationships of the screw plate tests were used to successfully predict values that compared favorably with the measured values at each stress level. The pressure–deformation–time relationship from stress-path-controlled triaxial consolidation tests were also evaluated, and they indicated behaviour similar to that of the screw plate test results. Soil parameters obtained from screw plate tests were subsequently used to predict the settlement of two test embankments, giving fairly close agreement with the observed values. Key words: soft clay, settlement, deformation, consolidation, screw plate test, triaxial test, embankment, prediction, stress path.
Permeability anisotropy of natural clays as a function of strain
Authors: Leroueil Serge , Bouclin G. , Tavenas F. , Bergeron L. , Rochelle P. La
Published: May 2008

Seven series of tests have been performed on specimens from five natural soft clay sites to determine the variation of the vertical and horizontal permeabilities when the soil is unidimensionally compressed. The results show that the permeability anisotropy does not increase significantly with compression up to strains of 25% for marine clays. In varved clays, mostly because the clay laminae are more compressible than the silty laminae, the anisotropy increases with vertical compression. Key words: permeability, clay, anisotropy, laboratory, compression.
Simulation of groundwater flow in complex multiaquifer systems: Performance of a quasi three-dimensional technique in the steady-state case
Authors: Rudolph D. L. , Sudicky E. A.
Published: May 2008

The ability of the classical quasi three-dimensional formulation to describe steady-state groundwater flow problems in complex multiaquifer environments is examined. In the present formulation, discontinuities in the aquifer and aquitard units can be accommodated along with partial or complete aquifer dewatering and confined or unconfined flow conditions. Some of the main assumptions underlying classical quasi three-dimensional schemes are scrutinized, including the requirement of a two orders of magnitude permeability contrast between aquifers and aquitards. Performance of the numerical scheme is studied through a series of test problems by comparing with results obtained from a conventional finite element model. A high degree of accuracy and flexibility is achieved with the extended quasi three-dimensional technique, yet the numerical efficiency inherent in the classical formulation is maintained. By dividing an aquifer into a series of horizontal sublayers, vertical resolution of the flow field can be achieved without resorting to a numerically intensive fully three-dimensional scheme. Because it is possible to compute a three-dimensional representation of the hydraulic head distribution in individual aquifers with the quasi three-dimensional formulation, even in the absence of layers of contrasting hydraulic conductivity, the technique provides a viable alternative to the much more complex fully three-dimensional schemes for a wide variety of groundwater flow problems. Key words: groundwater flow, multiaquifer, complex stratigraphy, numerical analysis, quasi three-dimensional, steady state.
Characterizing in situ stress domains at the AECL Underground Research Laboratory
Authors: Martin C. D.
Published: May 2008

The Underground Research Laboratory access shaft was excavated from the surface to about the 185 m depth in jointed pink granite. Below this depth to the 443 m depth the shaft was excavated in massive grey granite. The grey granite is essentially unjointed, except for a major low-dipping thrust fault and associated minor splays. Overcoring, hydraulic fracturing, convergence measurements, microseismic monitoring, and observations of shaft-wall failure and core discing indicate that unusually high in situ stresses can be associated with large volumes of massive, unjointed granite at fairly shallow depth. The database of in situ stress measurements collected at the Underground Research Laboratory indicates that major geological features, such as thrust faults, can act as boundaries for in situ stress domains and that both the magnitude and direction of the in situ stress state can change when these geological features are traversed. Key words: in situ stress, anisotropy, stress domains, thrust faults, overcoring, hydraulic fracturing, convergence measurements, excavation damage zones.
Laboratory modelling of field permeability tests in cased boreholes
Authors: Chapuis Robert P. , Soulié Michel , Sayegh Georges
Published: May 2008

Field permeability tests in cased boreholes have been modelled in a sand tank with controlled and measured hydraulic conditions. The testing program included "end of the casing" and "Lefranc" tests, as described in Canadian standards 2501-135 and 2501-130, for field permeability tests in a casing driven in a granular soil (valid for 10−5 < K < 10−2 cm/s approximately). The theoretical solutions for these tests require a list of assumptions that may be difficult to satisfy under field conditions. The method for detecting the common error in the assumed piezometric level gave in all cases a local piezometric level equal to that determined independently by a set of 22 piezometers. In accordance with the theoretical solutions, the K values given by the tests do not depend on the controlled upward or downward seepage in the sand tank. The average K value given by such field tests is strongly influenced by the preparation of the injection zone, which includes a natural soil in a more or less disturbed condition adjacent to an injection aperture or lantern of poorly known geometry and condition, so losses in hydraulic heads there may be different from those assumed in theory. From a practical point of view, all drilling operations have a major impact on the results and must be strictly controlled to have a reasonable estimate of the K value. Key words: permeability, field, borehole, model tests, piezometric level.
Remarks on the stability of temporary cuts
Authors: Leroueil S. , Rochelle P. La , Tavenas F. , Roy M.
Published: May 2008

A re-analysis of the observations and data related to the stability of excavations in clays gives a new insight into the problem. It is shown that for clays with a liquidity index greater than 0.4, the short-term stability can be estimated on the basis of the undrained shear strength without applying any correction factor; it is also shown that the long-term stability is lower than the short-term stability by an amount that depends on the overconsolidation ratio of the clay. Finally, experience proving that pore-pressure equilibration is highly variable and difficult to predict, it is recommended to systematically instrument excavations with piezometers. Key words: clay, short-term stability, long-term stability, excavations, pore pressures, overconsolidation ratio.
The effects of electroosmotic field treatment on the soil properties of a soft sensitive clay
Authors: Lo K. Y. , Ho K. S.
Published: May 2008

A field test was undertaken to assess the effectiveness of the electroosmotic strengthening of the soft sensitive (Champlain Sea) clay in the Gloucester Test Fill site by using specially designed copper electrodes to improve treatment efficiency. Tube samples, 127 mm in diameter, were recovered before and after field treatment for detailed laboratory tests. Isotropically consolidated undrained triaxial tests with pore-pressure measurements were performed. It was found that the failure envelope after treatment was significantly higher than the initial envelope, indicating that the strength in terms of effective stresses increased. Consolidation tests showed that, as a result of treatment, the preconsolidation pressure increased from 53 to 98 kPa. The soft clay is virtually "overconsolidated" by the process. Additional effects of electroosmosis on the properties of the soft clay are the increase in plasticity, carbonate content, and salinity and the decrease in sensitivity. There is, therefore, a general improvement in soil properties after treatment, both in terms of total and effective stresses. Key words: electroosmosis, soft sensitive clay, failure envelope, sensitivity, preconsolidation pressure, pH value.
Use of drainage wicks for an embankment on slickensided clay
Authors: Kack G. J. , Harris M. C. , Chatterji P. K. , Proudfoot D. W. , Trowsdale D. R. , Thomas R. R.
Published: May 2008

The 650-ha cooling pond for the Genesee thermal power plant near Edmonton required more than 15 km of earth-containment dyke up to 25 m high to be constructed on a high plastic clay foundation. Other embankment construction activity at the Genesee site indicated that there was very little dissipation of construction pore pressure in the foundation clay and that embankment heights of more than 6 m would require stabilization measures. The high portions of the cooling-pond dyke were built in three stages between 1982 and 1986. An extensive instrumentation monitoring program was established to control the rate of fill placement during construction. Counterbalancing earth berms were used to stabilize most of the high sections of dyke. During the later stages of dyke construction, lack of dissipation of high excess pore pressure in the foundation clay indicated that the sole use of counterbalancing berms might not provide sufficient stabilization. Prefabricated drainage wicks were used as an additional measure to lower the foundation pore pressures under the counterbalancing berms in these critical areas. Spacing of the wick drains was determined by applying Hansbo's wick-drain theory and from data collected from a wick-drain test section. Additional piezometers were installed prior to wick installation to assess the effectiveness of the wicks. Over 14 000 wick drains were installed at spacings of 2.5–2.75 m to a maximum depth of 26 m below the top of the berm. The installation procedures are discussed, along with difficulties of installation. The wicks were very effective in lowering the foundation pore pressures and improving dyke stability. Instrument monitoring data used to assess the wick-drain performance and to control the rate of construction during dyke completion are presented and discussed. Key words: drainage wick, high plastic clay, pore pressure, dissipation, deep, fill, dyke, instrumentation, monitoring.
Effective stress paths and pore-pressure responses during undrained shear along the bedding planes of varved Fort William Clay
Authors: Eigenbrod K. D. , Burak J. B.
Published: May 2008

Previous studies of the varved sensitive clays from the Thunder Bay area indicated that the geotechnical properties were influenced by their layered structure. When sheared along the bedding planes, double strength envelopes were apparent, with strength parameters depending on the stress levels applied. Thus, a series of consolidated isotropical undrained triaxial tests with pore-pressure measurements was carried out on specimens with the varves inclined to the vertical axis. A number of unusual results were observed: (i) low B-values for presumably saturated samples; (ii) failure of the specimens along the clay seams at stress levels above precompression load, exhibiting highly compressive behaviour and considerable cohesion; (iii) failure of the specimens in the silt seams at stress levels below the precompression load, exhibiting dilatancy and a lower cohesion than in the normally consolidated range; (iv) slightly anisotropic elastic deformation behaviour almost up to failure for testing in the precompression range; however, strongly anisotropic, largely nonelastic behaviour in the normally consolidated stress range, indicating larger stiffnesses vertically than horizontally. The stress paths in the normally consolidated stress range suggested also that consolidation of the clay seams occurred during undrained shear owing to internal dissipation of pore pressures into dilating silt seams. Key words: varved sensitive cemented clay, pore-pressure response, undrained shear, internal pore-pressure dissipation, anisotropic elastic behaviour, critical-state conditions.
Reliability analysis of drilled piers in expansive soils
Authors: Ferregut Carlos , Picornell Miguel
Published: May 2008

Heavy structures in areas with expansive soils are commonly founded on piers resting beneath the surface active zone. During construction, the piers remain essentially unloaded and are exposed to potentially high tensile stresses that can split the pier unless the pier has been adequately reinforced. In this context, uncertainties arise relative to (i) the parameters governing the load transfer from the soil to the pier, (ii) the potential heave to be expected in a "free field" condition, when the soil movements are not restricted by the pier, and (iii) the estimation of the pier capacity to resist the induced stresses. Probabilistic models to handle and to quantify these uncertain parameters are constructed and then used to compute the probability of exceeding two potential limit states: (i) vertical pier head displacement and (ii) maximum tensile stress in a cross section of the pier. The displacements are used to assess the serviceability performance of the pier, and the maximum tensile stresses are used to estimate the reliability of the pier. Key words: piers, expansive soil, reliability, probability, foundations.
Ice rubble attenuation of ice loads on arctic offshore structures
Authors: Wong T. T. , Morgenstern N. R. , Segoz D. C.
Published: May 2008

A state of the art survey of ice rubble mechanics is first presented. This survey covers ice rubble morphology, laboratory testing of ice rubble, the study of the load transmission capability of existing rubble fields, and field measurements in ice rubble surrounding offshore structures. Then, the implementation of a new plasticity model for normally consolidated broken ice into an existing finite element stress analysis code is described. The resulting program is validated using triaxial test data. Using this model, a two-dimensional parametric study on ice force transmission through a grounded ice rubble field is performed. The study shows that, in addition to the mechanical properties of ice rubble, the island or berm geometry may significantly affect the ice load. Key words: constitutive model, finite element analysis, ice load, ice rubble, offshore structure, plasticity.
Centrifuge modelling of ice and brittle materials
Authors: Palmer Andrew
Published: May 2008

Centrifuge modelling of a system that deforms by repeated fracture is analysed. If the governing crack length during repeated fracture is a material property, classical centrifuge modelling continues to apply. If, on the other hand, the cracks and ice fragments scale with the system as a whole, a different scaling rule follows: the acceleration imposed in the centrifuge should be the 3/2 power of the linear scale factor. Though at first sight surprising, this rule is consistent with field observations. Key words: ice, centrifuge modelling, fracture.
Freezing and thawing indices in northern Canada
Authors: McCormick G.
Published: May 2008

A method for determining the return period of values for thawing and freezing indices is presented. Data are based on published temperature records from 48 weather stations in northern Canada. Key words: freezing, thawing, permafrost.
Workshop on Stress Partitioning in Engineered Clay Barriers, Duke University, Durham, NC., U.S.A., May 29–31, 1992: Overview
Authors: Gray Malcolm N.
Published: May 2008

The accompanying text introduces a series of papers on various aspects of the use of bentonites for the storage and disposal of nuclear fuel waste. The papers were initially presented by a group of international researchers at a workshop on "Stress partitioning on engineered clay barriers" held at Duke University, Durham, N.C., in May 1991. The papers provide an excellent overview of current research on the properties and behaviour of dense, clay-rich bentonitic barriers. Key words : bentonites, nuclear fuel waste, workshop.
The effective stress concept in saturated sand–clay buffer
Authors: Graham J. , Oswell J. M. , Gray M. N.
Published: May 2008

Uncertainty has existed about the applicability of the effective stress concept to dense, compacted, plastic clays. To examine this, a series of tests has been performed on mixtures of sand and bentonite. Specimens were made by combining equal weights of the dry components with water and compacting the mixture to 85 or 95% ASTM Modified maximum dry density. The tests investigated the proposition that the behaviour of the mixture can be expressed in terms of effective stresses defined as the tensor difference between externally applied total stresses and pore-water pressures measured outside the cell. The proposition cannot be examined directly, but must be studied through a series of corollaries, that is, statements of behaviour that would be expected if the proposition were true. The testing considered the behaviour of specimens in consolidation and shear. Effective consolidation pressures were from 0.3 to 3.0 MPa, with back pressures from 0.2 to 7.0 MPa. Within acceptable bounds of experimental error, the tests show that effective stresss can be used to describe consolidation and shear behaviour. However, because part of the effective stress in the clay is derived from net interparticle repulsive (unit) forces seated in diffuse double layers around aggregations of bentonite particles, the applicability of the concept has at this stage been restricted to conditions of constant volume (or possibly constant straining rate), constant chemistry, and constant temperature. Key words : clay, plastic clay, expansive clay, bentonite, effective stress, triaxial, swelling pressure, swelling equilibrium.
Stress and pore pressure in saturated clay subjected to heat from radioactive waste: a numerical simulation
Authors: Ma Chenmin , Hueckel Tomasz
Published: May 2008

Some effects of temperature increase due to the emplacement of radioactive waste on the mechanical and hydraulic behavior of saturated clays are studied numerically. A mass-transfer model is adopted which simulates a possible degeneration of adsorbed water into bulk water at temperatures up to 150 °C. In contrast with a previous paper by the authors the heat output decreases with time to realistically simulate the effect of nuclear waste. Numerical results show that in the vicinity of the line heat source, a much lower value of excess pore pressure and faster propagation of the excess pore-pressure front are obtained because of the substantial increase in permeability arising from the adsorbed water degeneration at elevated temperatures. Moreover, the adsorbed water degeneration accelerates the water flow around the heat source. It is also concluded that over a long term the thermally induced degeneration of absorbed water into bulk water mitigates the possibility of thermal failure of clays surrounding the heat source. Key words : heating, adsorbed water, bulk water, adsorbed water degeneration (mass transfer), permeability, specific discharge, pore pressure.
Water uptake and swelling properties of unsaturated bentonite buffer materials
Authors: Kanno T. , Wakamatsu H.
Published: May 2008

The water diffusivity and the development of swelling pressure are investigated in buffer materials to be used for the geologic disposal of high-level radioactive waste during the stage of unsaturated water uptake. Highly compacted blocks of Japanese Na bentonite and a bentonite-sand mixture are used as the buffer material. The water diffusivity of the blocks has turned out to be approximately equal to that of Wyoming bentonite MX-80. Assuming that the local swelling pressure in a small element of a confined bentonite mass is proportional to the degree of saturation of the local area, an elastic model with an apparent Young's modulus is developed for the first step. According to this model, the swelling pressure of the bentonite mass as a whole is proportional to the avarage degree of saturation of the mass. For the development of the swelling pressure in the blocks, the calculated curve by this model is in good agreement with the experimental results except during the early parts of the process. Key words : bentonite, water uptake, water diffusivity, swelling pressure, elastic model, radioactive waste disposal.
Initiation of static instability in the submarine Nerlerk berm
Authors: Lade Poul V.
Published: May 2008

According to stability postulates by other authors, soils that exhibit nonassociated flow may become unstable when exposed to certain stress paths inside the failure surface. Several series of conventional triaxial tests on fully saturated specimens have been performed to study the regions of stable and unstable behavior. For saturated specimens that tend to compress, undrained conditions lead to effective stress paths directed within the region of potential instability, and instability is observed, provided the yield surface opens up in the outward direction of the hydrostatic axis. Thus, instability occurs inside the failure surface. Instability is not synonymous with failure, although both lead to catastrophic events. The location of the region of potential instability and its determination are discussed. The submarine Nerlerk berm, which suffered six slides during its construction, is analyzed using a newly developed method of instability analysis. It is shown that conventional slope stability methods do not capture the mechanics of instability and subsequent liquefaction. The proposed analysis method is based on the location of the region of potential instability and the stress state in the ground. In addition, a trigger mechanism is required to initiate the instability. These topics are discussed with reference to the slides in the Nerlerk berm. Key words : instability, nonassociated flow, plastic properties, sand, shear strength, submarine slope.
A general limit equilibrium model for three-dimensional slope stability analysis
Authors: Lam L. , Fredlund D.G.
Published: May 2008

A generalized model for three-dimensional analysis, using the method of columns, is presented. The model is an extension of the two-dimensional general limit equilibrium formulation. Intercolumn force functions of arbitrary shape can be specified to simulate various directions for the intercolumn resultant forces. A unique feature of the model involves the use of a geostatistical procedure (i.e., the Kriging technique) in modelling the geometry of the slope, the stratigraphy, the potential slip surface, and the pore-water pressure conditions. The technique simplifies the data-input procedure and expedites the column discretization and the factor of safety computations. The shape of the intercolumn force functions was investigated for several slope geometries using a three-dimensional finite element stress analysis. The significance of the intercolumn force functions in three-dimensional stability analyses was also studied. The model was utilized to study a case history involving an open-pit mining failure. The results indicate that the model is able to provide a more realistic simulation of the case history than was possible using a conventional two-dimensional model. Key words : stability analysis, general limit equilibrium, three-dimensional, method of columns, factor of safety.
Behaviour of loose sand under simultaneous increase in stress ratio and principal stress rotation
Authors: Wijewickreme Dharmapriya , Vaid Yoginder P.
Published: May 2008

The drained behaviour of loose sands under simultaneous increase in stress ratio and principal stress rotation is investigated. The hollow cylinder torsional device, which permits independent control of four stress parameters, namely effective mean normal stress [Formula: see text], stress ratio R, intermediate principal stress parameter b, and the inclination ασ of the major principal effective stress [Formula: see text] to the vertical, is adopted as the testing device. Drained tests carried out on saturated sand indicate that deformations under increasing R and ασ are path independent, if the final stress state is within the approximate bounds of R < 2 and ασ < 45°. With increasing stress ratio R and (or) principal stress rotation, deformations gradually become path dependent. Once loaded to a stress state within the domain R < 2 and ασ < 45°, the strain response under subsequent principal stress rotation is shown to be independent of the previous loading history. It is demonstrated that the strain response under any general increasing R − ασ path in the domain of R < 2 and ασ < 45° can be predicted using the results of a limited number of tests characterizing that domain. Strain increment direction αΔε is shown to be approximately coincident with and totally governed by the stress increment direction αΔσ, when the stress increment direction αΔσ is preferentially inclined towards the vertical deposition direction. Key words : sand behaviour, hollow cylinder torsional device, principal stress rotation, stress-path testing.
Suivi de l'injection au moyen de l'émission acoustique
Authors: Rhazi Jamal , Ballivy Gérard
Published: May 2008

The injection of grout in the microfissures of concrete dams in operation is very tricky because of the high pressures required to penetrate the slightly opened fissures. These conditions of grouting may result in the propagation of the fissures and contribute to the loss of stability of the mass. The technique using acoustical emission to follow the injection in real time has been evaluated. Water injection tests have been carried out on large dimensions (2.64 m × 1.42 m × 0.40 m) fissured concrete slabs instrumented with pressure, load, and displacement transducers. According to a study comparing two types of acoustical emission transducers, the low-frequency transducers would be more appropriate for this type of application. Moreover, the detected acoustical signals are not due to a constant pressure flow, but to the accelerations and decelerations of the grout, and to the mechanisms resulting from the variations of pressure and flow of the fluid (opening and closure of the fissure). Thus these observations confirm that the acoustical emission may be an interesting means to control the injections and, in particular, to determine the process of grout flow. Key words : concrete, fissure, injection, water test, pressure, acoustical emission. [Journal translation]
Investigations of high uplift pressures beneath a concrete dam
Authors: Hanna Alfred W. , Plewes Howard D. , Wong Raymond , Seyers William C.
Published: May 2008

Deficiency investigations were undertaken at Hugh Keenleyside Dam, near Castlegar, British Columbia, to identify the nature and sources of foundation defects responsible for high uplift pressures under a section of the concrete dam. Several techniques employed in the investigations proved particularly useful in delineating the defects. These were temperature surveys and chemical analysis of flows from pressure instruments and foundation drains, air-injection tests, foundation coring and installation of additional piezometers. A comprehensive program of pressure response testing of cells, piezometers, and drains was also carried out to establish the interconnections within the rock foundation. Detailed assessments of construction records to assemble relevant geological and foundation conditions, foundation excavation, preparation, and treatment aspects, and particular structural foundations were vital in discerning the cause for the high uplift pressures. Piping of a relatively thin, upstream, impervious till blanket (required for the earthfill dam) on blast-induced, highly fractured rock extending under the structure was found to be the defect responsible for reservoir leakage and high uplift pressures. Key words : uplift pressures, concrete dam, foundation drains, piezometers, uplift cells, temperature survey.
The landslide dam on the Saddle River near Rycroft, Alberta
Authors: Cruden D.M. , Keegan T.R. , Thomson S.
Published: May 2008

Alberta's largest historic landslide dammed the Saddle River near Rycroft, Alberta, and thrust the bed of the river upward against the opposite valley wall forming a type 6 landslide dam. The Rycroft landslide occurred within a day or two of 17 June 1990 on the north wall of the Saddle River, 12 km northeast of Rycroft, Alberta. The triggers for the landslide are considered to be the lateral and vertical erosion of the river as a result of a severe rainstorm and the ensuing flood. The slide scarp arcs for 1 km through a cultivated field. The loss of farmed land was 13 h (32 acres); a further 10 h (25 acres) may be lost by retrogression of the scarp. The toe heaved the riverbed upward as much as 20 m and thrust it laterally 60 m to be compressed against the opposite valley wall. About 40 Mm3 of ground moved. The rupture surface dipped steeply through postglacial lake clay and till, curved abruptly to pass on a subhorizontal surface through preglacial clay, then curved upward under the riverbed. This preglacial clay is a new factor in landslide assessment in northwestern Alberta. Key words : landslide, landslide dam, Interior Plains, preglacial clays.
Rock topples in the highway cut west of Clairvaux Creek, Jasper, Alberta
Authors: Cruden D.M. , Hu Xian-Qin , Lu Zhongyou
Published: May 2008

The topples exposed in the road cut along Highway 16, 17 km west of Jasper, Alberta, were caused by slope steepening by both glaciation and excavation. The toppling of layers that underdip the cut slope was initiated by water pressure, ice pressure, and loose materials in the cracks of rock masses with large block ratios. Toppling formed well-exposed sliding surfaces on steep slopes and rupture surfaces on shallower slopes. Key words : rock slopes, rock cuts, Rockies, toppling, sliding, underdip slopes.
Vertical bearing capacity factors for circular and strip footings on Mohr–Coulomb soil
Authors: Bolton M.D. , Lau C.K.
Published: May 2008

The method of characteristics is used to establish consistent factors for the vertical bearing capacity of circular and strip footings on soil which satisfies a linear [Formula: see text] Mohr–Coulomb strength criterion. This method of solution avoids the assumption of arbitrary slip surfaces, and produces zones within which equilibrium and plastic yield are simultaneously satisfied for given boundary stresses. Although similar solutions have previously been published for circular footings, their application has been hindered by errors and confusions over terminology. These are resolved, and the method of solution is explained. It is confirmed that Terzaghi's approach to the superposition of bearing terms containing Nq, Nγ, and Nc is both safe and sufficiently accurate for circular footings, as for strip footings. The values to be adopted are tabulated as functions of [Formula: see text]. Differences between the factors applicable to circular and strip footings far exceed the allowances of the empirical shape factors in common use. Some new shape factors are suggested that better represent the relationship between the limiting equilibrium of circular and strip foundations. Some current shape factors attempt to allow simultaneously for the differences in equilibrium solutions and the differences in axisymmetric (triaxial) and plane strain soil parameters. This cannot succeed, since the relationship between strength parameters depends strongly on relative density. The new bearing factors facilitate a more rational approach in which soil parameters appropriate to the geometry can first be determined and then used to find appropriate bearing capacity factors. Key words : bearing capacity, axisymmetry, method of characteristics, footings, plane strain.