bluuebunny/crossref_metadata_2025 huggingface dataset:
The kinematic behaviour of drag anchors in sand
Authors: Neubecker S R , Randolph M F
Published: April 2011

The kinematic behaviour of drag achors during embedment in sand is examined in this paper. A series of centrifuge model anchor tests has been performed in silica and calcareous sands in which both force and kinematic data were obtained during the course of anchor embedment. In this paper, the kinematic data have been examined to determine general rules for the kinematic behaviour of a drag anchor during embedment. These rules provide an essential step towards a theoretical simulation of a complete anchor embedment history and hence a predictive tool for the ultimate holding capacity of a drag anchor.

Key words: drag anchor, kinematics, sand, limit equilibrium, ultimate holding capacity.
On the estimation of frost loads
Authors: Rajani B , Zhan C
Published: April 2011

Frost load is an important loading condition to consider for the design of buried pipes. Though frost loads can be much greater than earth loads, it is not presently possible to estimate frost loads except using heuristic arguments. This paper describes the development of simplified methods to estimate frost load. Important variables are identified that can explain how the effects of frost loading can be mitigated. Sensitivity analyses are presented to highlight the importance of the different variables involved in the simplified methods. Frost loads measured in a field case study are compared with calculated frost loads in trenches with clay and sand backfills.

Key words: frost load, frost depth, buried pipe, trench backfills, trench width.
Measurement of hydraulic conductivity in oil sand tailings slurries
Authors: Suthaker Nagula N , Scott J Don
Published: April 2011

Fine tails, the resulting fine waste from oil sand processing, undergoes large-strain consolidation in tailings ponds. Its consolidation behaviour must be analyzed using a large-strain consolidation theory, which requires the determination of the relationship between the void ratio and hydraulic conductivity. Conventional measurement techniques are not suitable for fine tails, and a special slurry consolidometer, with a clamping device to prevent seepage-induced consolidation, was designed to determine the hydraulic conductivity of the fine tails and nonsegregating fine tails  sand slurries. The hydraulic conductivity of slurries is not constant but decreases with time to a steady-state value. Hydraulic conductivity is also influenced by the hydraulic gradient and bitumen content. It is shown that a low hydraulic gradient, less than 0.2, is necessary to counteract the effect of the bitumen and to represent tailings pond conditions. The hydraulic conductivity of fine tails  sand mixes is controlled by the fines void ratio, hence, fines content. The hydraulic conductivity of chemically amended nonsegregating tailings can be lower than that of fine tails. However, acidlime or acid  fly ash amended nonsegregating tailings have similar hydraulic conductivity values in terms of fines void ratio. The hydraulic conductivity of nonsegregating tailings appears to be governed by fines content and by the nature of the fines aggregation caused by the chemical additive.

Key words: tailings, slurries, hydraulic conductivity, slurry consolidometer, nonsegregating tailings, oil sands.
Uplift behaviour of cylindrical anchors in sand
Authors: Hsu S T , Liao H J
Published: April 2011

A series of laboratory model tests and numerical analyses has been carried out to study the behaviour of vertically embedded cylindrical anchors in sand. Due to the cylindrical shape of the anchor, both the shaft friction and the end resistance have substantial contribution to the pullout capacity. But shaft friction and end resistance do not reach peak values at the same anchor displacement. As a result, analyzing the anchorage behaviour of cylindrical anchors is complicated. The pullout behaviour of the anchor is significantly influenced by the embedded depth. There exists a critical depth (about seven to eight times the anchor diameter D) which differentiates the behaviour of a deeply embedded cylindrical anchor from that of an anchor with shallow embedment. The complete load-displacement relationships for shallow and deep anchors can be simulated by the numerical analysis proposed herein. A minimum horizontal spacing of 10D is needed between neighbouring cylindrical anchors to be free of interference.Key words: cylindrical anchor, uplift behaviour, laboratory model test, numerical analysis, sand.
Model for the simulation of swelling-pressure measurements on expansive soils
Authors: Shuai Fangsheng , Fredlund D G
Published: April 2011

Numerous laboratory swelling tests have been reported for the measurement of swelling pressure and the amount of swell of an expansive soil. These test methods generally involve the use of a conventional one-dimensional oedometer apparatus. Few attempts, however, have been made to formulate a theoretical framework to simulate the testing procedures or to visualize the different stress paths followed when using the various methods. The simulation of the oedometer tests on expansive soils is required to fully understand the prediction of heave. The correct measurement of swelling pressure is required for an accurate prediction of heave. It is further anticipated that some information on unsaturated soils property functions may be approximated from the back-analysis of the data. A theoretical model is proposed to describe the pore-water pressures with time and depth in a specimen as well as the volume changes during various oedometer swell tests. The model is formulated based on equilibrium considerations, constitutive equations for an unsaturated soil, and the continuity requirement for the pore fluid phases. The transient water flow process is coupled with the soil volume change process. The model can be used to describe the volume-change behaviour, pore-water pressure, and vertical total stress development in an unsaturated soil during an oedometer test performed by any one of several test procedures. The model has been put into a finite element formulation using the Galerkin technique. All the parameters required to run the model can be obtained by performing independent, common laboratory tests. The proposed model was used to simulate the results from free-swell, constant-volume, constant water content, and loaded-swell oedometer tests. Computed values of volume change, vertical total stress, and pore-water pressure are in good agreement with measured values.Key words: unsaturated soil, expansive soil, swelling pressure, theoretical simulation, constant-volume oedometer test, free-swell oedometer test, loaded-swell oedometer test.
In situ shear tests of soil blocks with roots
Authors: Wu Tien H , Watson Alex
Published: April 2011

In situ shear tests were performed on soil blocks that contained roots to study the contribution of roots to the shear strength in a case where the shear deformation is not constrained to a thin zone. The shearing resistance of the soil-root system, the tensile force in selected roots, and the deformation of the soil block were measured. The roots were exposed after the test and their positions were determined and used to estimate the initial positions. The root force and the shearing resistance of the soil-root system were estimated with known solutions and compared with measured root force and shearing resistance. None of the roots that passed through the shear zone failed in tension at the maximum displacement. As a consequence, the root resistance is much less than that found in a case where the failure surface is restricted to the boundary between a weak soil and a firm base and where roots are anchored in the firm base and fail in tension. Simplified procedures for estimating root forces are suggested for the case of a thick shear zone.Key words: in situ test, roots, shear strength, slope stability, soil reinforcement, soilroot interaction.
Foundation design aspects of the Confederation Bridge
Authors: Becker Dennis E , Burwash WJ (Bill) , Montgomery RA (Bob) , Liu Y (Bill)
Published: April 2011

The Confederation Bridge is a 12.9 km long multi-span bridge spanning the Northumberland Strait to connect the provinces of Prince Edward Island and New Brunswick on the east coast of Canada. It is the longest continuous marine span bridge over ice-covered water in the world. The bridge is a design, build, operate, and transfer facility with the Government of Canada being the ultimate owner. Construction started in October 1993, and the bridge officially opened, on schedule, to traffic on June 1, 1997. The combination of deep water, high lateral and eccentric loads, complex geology and variable strength bedrock, and short construction window due to ice and bad weather introduced many foundation engineering challenges. This paper summarizes and discusses the geotechnical aspects of foundation design and construction monitoring services for the bridge. The geological setting and geotechnical conditions, the loading conditions and design criteria, specialized geotechnical analyses, foundation design, and construction quality assurance - quality control issues are described and discussed.Key words: Confederation Bridge, Northumberland Strait, foundation design, quality assurance, ring footing, drilled shafts.
Vacuum preloading consolidation of reclaimed land: a case study
Authors: Shang J Q , Tang M , Miao Z
Published: April 2011

This case study presents the design, operation, and results of a soil improvement project using the vacuum preloading method on 480 000 m2 of reclaimed land in Xingang Port, Tianjing, China. The areas treated with vacuum ranged from 5000 to 30 000 m2. The effects of soil improvement are demonstrated through the average consolidation settlement of 2.0 m and increases in undrained shear strengths by a factor of two to four or more. The study shows that the vacuum method is an effective tool for the consolidation of very soft, highly compressive clayey soils over a large area. The technique is especially feasible in cases where there is a lack of surcharge loading fills, extremely low shear strength, soft ground adjacent to critical slopes, and access to a power supply.Key words: vacuum preloading consolidation, soil improvement, soft clays, land reclamation, prefabricated vertical drains.
Weathering-induced fissuring and hydraulic conductivity in a natural plastic clay
Authors: Yuen K , Graham J , Janzen P
Published: April 2011

Flexible-wall (triaxial) permeability tests have examined how laboratory-induced weathering affects the hydraulic conductivities of "undisturbed" specimens of a high-plastic expansive natural clay. After freezing-thawing or drying-wetting, hydraulic conductivities were on average about one order of magnitude higher than unweathered values. Reductions of hydraulic conductivity occurred in some specimens that were dried and then rewetted before permeation. The generally small changes in hydraulic conductivity are attributed to the expansive nature of the clay which allows swelling and reorientation of soil aggregates on thawing or rewetting. The changes may also have been influenced by the confining pressures of 35 kPa used in the tests. Hydraulic conductivities measured by oedometer were smaller than those in triaxial tests and varied strongly with pressure level.Key words: hydraulic conductivity, clay, plastic, weathering, desiccation, freezing.
Determination of the reactivity of clay-fluid systems using liquid limit data
Authors: Fam M A , Dusseault M B
Published: April 2011

The reactivity coefficient, defined as lambda = rhowGsSatheta (rhow is the mass density of water, Gs is the specific gravity, Sa is the specific surface, and theta is the double-layer thickness), has been proposed as a parameter to assess the sensitivity of a clay-fluid system to changes in physical and chemical properties of the pore fluid. In this study, the liquid limit of a clay-fluid mixture, wL, is shown to be related to the reactivity coefficient. Double-layer theory is applied to determine the void ratio at the liquid limit, which is assumed to occur at a stress close to 10 kPa. Liquid limit data were measured for a bentonite clay at different pore-fluid concentrations; other data were collected from the literature. Both measured and collected data followed the proposed simple expression, suggesting that there is a unique relationship between wL and lambda, at least for the three-layer sheet minerals (or for clays with wL > 50). The proposed expression can be used as a simple approach to determine the sensitivity of clay-fluid systems. A parametric study based on the lambda-wL relationship is presented to study the effects of temperature and pore-fluid concentration on the liquid limit.Key words: clay, specific surface, pore fluid, ion concentration, double layer.
Laboratory testing on an unsaturated soil: equipment, procedures, and first experimental results
Authors: Rampino C , Mancuso C , Vinale F
Published: April 2011

This paper describes two new apparatuses recently developed at the Università di Napoli Federico II (Italy) in order to test soils under unsaturated conditions. The related experimental procedures and the first results obtained on a dynamically compacted silty sand are also discussed. The devices mentioned are a Bishop and Wesley stress-path cell and a Wissa oedometer, modified to control matric suction and to measure all the stress-strain variables relevant to unsaturated soil mechanics. Specific experimental procedures were established to perform tests under general conditions and were carefully verified during several tests. Using the triaxial cell, isotropic and anisotropic compression stages were carried out under constant suction levels of 0, 100, 200, and 300 kPa. Furthermore, two deviator stages were performed following different stress paths and water drainage conditions. Using the oedometer, an additional suction level (400 kPa) was investigated during compression tests driven up to 5 MPa of vertical net stress (sigmav- ua). This research is a part of a major project in progress at the Dipartimento di Ingegneria Geotecnica of Naples; it is aimed at the experimental analysis of the behaviour of several dynamically compacted soils and at the numerical modelling of boundary problems related to earth structures.Key words: unsaturated soils, equipment layout, silty sand, matric suction.
Runout of dry granular avalanches
Authors: Davies T R , McSaveney M J
Published: April 2011

Laboratory experiments on granular avalanching of dry sands and gravels reveal a consistent pattern of runout distance varying with fall height, fall slope, and volume of material for volumes ranging from 0.1 to 1000 L. Data from the South Ashburton rock avalanche deposit show that its runout behaviour differs only slightly from that of the laboratory avalanches, extending the range of this behaviour to granular avalanches with volumes of about 100 000 m3. By contrast, data from much larger rock avalanches (> 107m3) depart significantly from the trends of the laboratory data; some factor not present in the laboratory, such as rock fragmentation or the presence of an erodible substrate, must influence the behaviour of these larger events. Travel angles as low as 13° in the laboratory tests result from grain flow mechanisms with normal friction coefficients; they are not associated only with large-volume events and do not necessarily indicate unusual material mobility at any scale.
Effects of sample disturbance on the stress-induced microfracturing characteristics of brittle rock
Authors: Eberhardt E , Stead D , Stimpson B
Published: April 2011

The effects of sampling disturbance on the laboratory-derived mechanical properties of brittle rock were measured on cored samples of Lac du Bonnet granite taken from three different in situ stress domains at the Underground Research Laboratory of Atomic Energy of Canada Limited. A variety of independent measurements and scanning electron microscope observations demonstrate that stress-induced sampling disturbance increased with increasing in situ stresses. The degree of damage was reflected in laboratory measurements of acoustic velocity and elastic stiffness. Examination of the stress-induced microfracturing characteristics during uniaxial compression of the samples revealed that the degree of sampling disturbance had only minor effects on the stress levels at which new cracks were generated (i.e., the crack initiation stress threshold). Crack-coalescence and crack-damage thresholds, on the other hand, significantly decreased with increased sampling disturbance. The presence of numerous stress-relief cracks in the samples retrieved from the highest in situ stress domains was seen to weaken the rock by providing an increased number of planes of weakness for active cracks to propagate along. A 36% strength decrease was seen in samples retrieved from the highest in situ stress domain (sigma1 - sigma3 approximate 40 MPa) as compared with those taken from the lowest in situ stress domain (sigma1 - sigma3 approximate 10 MPa).Key words: sample disturbance, brittle fracture, crack initiation, crack propagation, material properties, rock failure.
Genetic algorithm search for critical slip surface in multiple-wedge stability analysis
Authors: Goh Anthony TC
Published: April 2011

Most procedures for determining the critical slip surface in slope-stability analysis rely on traditional nonlinear optimization techniques. The main shortcoming of these techniques is the uncertainty as to robustness of the algorithms to locate the global minimum factor of safety rather than the local minimum factor of safety for complicated and nonhomogeneous geological subsoil conditions. This paper describes the incorporation of a genetic algorithm methodology for determining the critical slip surface in multiple-wedge stability analysis. This search strategy is becoming increasingly popular in engineering optimization problems because it has been shown in a wide variety of problems to be suitably robust for the search not to become trapped in local optima. Three examples are presented to demonstrate the effectiveness of the genetic algorithm approach. The search strategy was found to be sufficiently robust to handle layered soils with weak, thin layers, and as efficient and accurate as the conventional pattern search method.Key words: critical slip surface, factor of safety, genetic algorithms, optimization, slope stability, wedge analysis.
Contaminant transport through an unsaturated soil liner beneath a landfill
Authors: Fityus S G , Smith Daniel W , Booker J R
Published: April 2011

Contaminant transport through soil is often modelled mathematically by means of the dispersion-advection equation. When investigating contaminant migration beneath a landfill, a common assumption is that the soil is saturated; however, it is well known that the soil beneath many landfills is only partially saturated. In this paper, steady-state unsaturated moisture distributions are employed in the dispersion-advection equation to find transient contaminant distributions beneath a landfill. A finite layer formulation is used to simplify the contaminant mass transport equation and account for heterogeneous soil profiles. Various assumptions concerning the flow regime beneath the landfill and the functional relation between volumetric water content and the diffusion coefficient in the transport equation are made to highlight differences between contaminant transport through saturated and unsaturated soils. It is found that diffusive contaminant mass transfer through a partially saturated soil liner is comparatively insensitive to variation of the volumetric moisture content at the top of the soil liner alone. However, accounting for the dependence of the diffusion coefficient on the volumetric moisture content of the soil does have a significant effect on diffusive mass transfer through a partially saturated soil liner. Though it is difficult to measure the dependence of the diffusion coefficient on the volumetric moisture content of the soil experimentally, this information appears necessary for a rational analysis of contaminant transport through partially saturated soils.Key words: landfill, contaminant transport, unsaturated soil.
Axial response of piles in electrically treated clay
Authors: Abdel-Meguid M , El Naggar M H , Shang J Q
Published: April 2011

Improvement of the shear strength of soft clayey soils around steel pipe piles using high-voltage electrokinetics is investigated in the present study. The experimental setup of a large-scale testing facility is described. Four model piles were installed in two identical cylinders filled with simulated marine sediment. Five electrically insulated electrodes were installed close to the piles to apply a high-voltage electric field in the test cylinder. Negative direct current voltages of -20, -30, and -10 kV were applied in three phases, respectively, for 33 days in the treatment cylinder. Axial compression and pullout pile load tests were performed and the results were compared for both cylinders after each phase of treatment. The pile response is presented in terms of the experimental load deflection curves. It is observed that the axial capacity was increased 30, 29, and 8% after the first, second, and third treatment phases, respectively. The pullout capacity was increased due to the treatment by 11, 23, and 12% after the first, second, and third treatment phases, respectively. Further development of this technique may provide potential solutions for the improvement of soft marine clays, and ultimately it could be applied in the field to rehabilitate existing offshore foundations.Key words: electrokinetics, piles, marine clays, soil improvement, bearing capacity, axial loading.
Pore-water pressure response during undrained isotropic load changes in layered soils
Authors: Eigenbrod K D , Wurmnest W H
Published: April 2011

Low pore-water pressure responses observed during undrained isotropic loading of thinly interbedded varved clay specimens were related to internal pore-water pressure equalization and internal shearing between soft clay seams and stiff silt layers of the varved clay. Both processes were analyzed in two separate models: a finite element analysis of the layered soil specimen with different elastic properties for each layer showed that shear stresses can develop along the layer interfaces during undrained isotropic loading. However, because the shear stresses are small and restricted to a narrow zone close to the surface of the cylindrical specimen, it appeared that the effect of shearing on the overall pore-water responses is negligible. The analysis of the pore-water pressures during undrained, isotropic loading demonstrated that hydraulic gradients between the two layers will develop. As a result, pore water will drain from the clay into the silt, leading to consolidation of the clay and swelling of the silt seams. The stabilized pore-water pressures should be the same as the pore-water pressures measured for the overall specimen, if the effect of internal shearing is negligible. Comparison of the computed with the measured overall pore-water pressure responses during testing for Skempton's pore-pressure coefficient B indicated reasonable agreement.Key words: Skempton's pore-pressure coefficient B, pore-water pressure response, varved clays, internal shearing, internal pore-water pressure equalization.
Application and validation of a numerical model of flow through embankment dams with fractures: comparisons with experimental data
Authors: Billstein Mats , Svensson Urban , Johansson Nils
Published: April 2011

The focus of this paper is on the development and validation of a numerical model of flow through simplified embankment dams with fractures. Two laboratory experiments were conducted to provide data for validation of the numerical model, one dealing with steady flow in a Hele-Shaw cell and one with steady flow through a bed of packed glass beads. A horizontal fracture, extending from the upstream boundary to a point within the embankment, was used in both experiments, and it was shown to have a significant influence on the discharge, pressure distribution, height of the seepage face, and free surface profile. Comparisons between numerically determined and experimentally measured results were carried out with respect to the discharge, pressure distribution, height of the seepage face, and free surface profile. In the experiments it is shown that a fracture increases the discharge and that the discharge increases more when a fracture is located far away from the free surface profile than when it is located close to the free surface profile. The height of the seepage face above the tailwater is strongly dependent upon the length of the fracture. The influence on the free surface profile is greater when a fracture is close to the free surface profile than when it is far away from the free surface profile. These effects are also found in the numerical simulations. It is thus concluded that the agreement is generally satisfactory between the experimental and numerical results.Key words: numerical model, embankment dam, fracture, experimental data, discharge.
A consolidation model for a creeping clay
Authors: Stolle DFE , Vermeer P A , Bonnier P G
Published: April 2011

A nonlinear theory of consolidation is presented which takes into account secondary compression. The theory is incorporated into a weak form of equilibrium that is suitable for a finite element procedure. The model is used to interpret Crawford's experimental data on Leda clay. Limitations of the model are discussed, and a few thoughts on the effects of temperature on the evaluation of model parameters are briefly presented.Key words: secondary compression, creep, one-dimensional consolidation, modelling.
A generalized relationship to estimate thermal resistivity of soils
Authors: Gangadhara Rao MVBB , Singh D N
Published: April 2011

Soil thermal resistivity plays an important role in the design and laying of high-voltage buried power cables, oil and gas pipelines, nuclear waste disposal facilities, ground-modification techniques employing heating and freezing, etc. For these situations, it is important to estimate the resistance offered by the soil mass in dissipating the heat generated. Several investigators have tried to develop mathematical and theoretical models to estimate soil thermal resistivity. However, these models are not always capable of predicting thermal resistivity of soils. This is mainly due to the fact that thermal resistivity of soil is a complex phenomenon that depends upon various parameters, viz. type of the soil, particle-size distribution, compaction characteristics, etc. As such, none of the relationships available in the literature are suitable for estimating the thermal resistivity of all soils. This paper deals with the details of fabrication of a "laboratory thermal probe" which has been used to evaluate thermal resistivity of various soils. A relationship has been proposed to estimate thermal resistivity of soils depending upon the moulding moisture content and density of the soils.Key words: thermal resistivity, laboratory thermal probe, black cotton soil, fly ash, sands, silty sand.
Influence of clay mineralogy and pore-medium chemistry on clay sediment formation
Authors: Sridharan A , Prakash K
Published: April 2011

The responses of the two common clay minerals in soils, namely kaolinite and montmorillonite, to varying physicochemical factors are quite drastic and opposite. The effect of variation in the physicochemical factors is phenomenal at very high water contents of the sediments, as the electrical forces of attraction and repulsion play a decisive role in controlling the structure of the sediment formed. This note discusses through detailed illustrations the effect of dielectric constant and electrolyte concentration as well as the effect of valency and hydrated size of the exchangeable cations on the sediment volume of clayey soils as governed by the clay mineralogy. Key words: clays, kaolinite, montmorillonite, pore-medium contamination, sediment formation.
Reconsideration of case histories for estimating undrained shear strength in sandy soils
Authors: (Fear) Wride C E , McRoberts E C , Robertson P K
Published: April 2011

When sandy soils respond in a strain-softening manner to undrained loading, an estimation of the resulting undrained shear strength (Su) is required to determine the potential for flow liquefaction at a given site. One of the most commonly used methods for estimating the undrained strength of liquefied sand is an empirical standard penetration test (SPT) based chart (originally proposed by H.B. Seed), which was developed using a number of case histories. The original interpretations of these case histories are viewed by many workers and regulatory agencies as the most authoritative measure of the liquefied strength of sand. Consequently, in comparison, other less conservative methods are generally held in an unfavourable light. This paper reexamines the original database of case histories in view of some more recent concepts regarding soil liquefaction. The objectives of this paper are to explore and reassess the issues involved in the original assessment and to offer alternative views of the case records. The conclusions presented here indicate that alternative explanations of the liquefied strength of sand are not inconsistent with the original case histories. Key words: sandy soils, soil liquefaction, undrained strength, standard penetration test (SPT).
A fragmentation-spreading model for long-runout rock avalanches
Authors: Davies T R , McSaveney M J , Hodgson K A
Published: April 2011

Based on the observation that deposits of large rock avalanches consist predominantly of intensely fragmented rock debris, it is proposed that the processes of rock fragmentation are significant causes of the peculiar distribution of mass in these deposits, and of the correspondingly long runout. Rock fragmentation produces high-velocity fragments moving in all directions, resulting in an isotropic dispersive stress within the translating rock mass. A longitudinal dispersive force consequently acts in the direction of reducing mass depth and tends to cause the rear part of the avalanche to decelerate and halt and the front part to accelerate. The result is greater longitudinal spreading of the travelling mass compared with nonfragmenting granular avalanches. The longer runout results from this additional fragmentation-induced spreading.
Properties and behaviour of Hong Kong marine deposits with different clay contents
Authors: Yin Jian-Hua
Published: April 2011

Large-scale marine reclamation has taken place on soft Hong Kong marine deposits (HKMD). More and more reclamation is to be undertaken due to the rapid development of infrastructures and housing projects. Properties and behavioural parameters (e.g., consolidation parameters) of HKMD are required for the design of reclamation or foundations on HKMD. The behaviour of HKMD is affected by clay content and other factors. This paper presents results dealing with the (i) composition (content of clay, silt, and sand), (ii) index properties, (iii) behaviour during oedometer consolidation, and (iv) strength and deformation behaviour in triaxial compression for HKMD deposits with different clay contents. Correlations of the behavioural parameters with clay content and index properties are obtained, presented, and discussed. The correlations and parameter values obtained in the present study follow the same trend as those published in the literature. Limitations on the application of these correlations are pointed out.
Observed and calculated load-settlement relationship in a sandy gravel
Authors: Rodríguez-Roa Fernando
Published: April 2011

The purpose of this research was to obtain a better understanding of the nonlinear stress-strain behavior of the typical gravel of Santiago, Chile, due to the increasing needs for construction of high-rise buildings, multilevel underground constructions, and new subway lines to be built under historical city landmarks. A finite-element computer program to perform incremental stress-strain analyses of soils was developed on the basis of a modified version of the hyperbolic elastic model. The changes herein proposed to this well-known constitutive model were based on triaxial tests carried out on 150 mm diameter specimens of compacted sandy gravels which involved various stress paths. A comparison was performed between the observed and calculated load-settlement relationship in a plate-load test that included unloading-reloading cycles. From the good agreement obtained it is concluded that the modified version of the hyperbolic model proposed represents reasonably well the behavior of the Santiago gravel.Key words: constitutive relations, finite-element model, laboratory tests, field tests, soil properties, case history.
Full-scale field tests on directly embedded steel pole foundations
Authors: Haldar Asim , Yenumula VSN Prasad , Chari T R
Published: April 2011

The results of eight full-scale tests on directly embedded steel pole foundations are presented. Fully instrumented poles were tested to measure the various design parameters. Different types of backfills such as sand, in situ gravelly sand, crushed stone, and flowable material were used. Various parameters were measured, including applied moment, ground line deflection-rotation, rotation of the pole below the ground level, soil pressures, and bending moments in the poles. The behaviour of these foundations was explained through ultimate capacity and moment-rotation characteristics. Based on these test results, it was found that the capacity of the directly embedded pole foundation depends primarily on the compaction levels of backfill and the embedment length of the pole. Flowable backfill material, which does not require any compaction, was found to be most effective and promising. Even when the backfill was loose, the lateral capacity significantly increased by the addition of a baseplate or by installing the pole with an additional embedment depth. Various theories developed for laterally loaded rigid piles were used to predict the moment-rotation behaviour and the ultimate capacity of the directly embedded pole foundation with different types of backfill material. Results from the analytical investigations were compared with those obtained from the full-scale load tests. Comparisons show that the ultimate capacities predicted by the models ranged from 0.30 to 2.20 times the measured capacities.Key words: backfill, compaction, full-scale tests, laterally loaded rigid piles, transmission steel poles, ultimate moment.
Compressibility effect in evaluating the pore-size distribution of kaolin clay using mercury intrusion porosimetry
Authors: Penumadu Dayakar , Dean John
Published: April 2011

The objective of the present research is to quantitatively evaluate the compression that can occur during the evaluation of pore-size distribution of cohesive soil using mercury intrusion porosimetry (MIP). A new experimental procedure was developed that can be routinely used to evaluate the corrections associated with the compressibility for porous solid samples using MIP. The approach used in this study involves performing mercury intrusion tests on dehydrated kaolin samples using freeze-dried and oven-dried techniques, and on identical samples confined by low-porosity latex membranes. Corrections for latex intrusion and issues related to dehydration of samples are addressed. The measured contact angle of mercury with kaolin clay using the sessile drop technique was used in the data reduction. Repeatable test results were obtained throughout the testing program. The procedure for obtaining volume-change behavior under isotropic conditions for a large range of pressures using the mercury porosimeter is also presented for oven-dried samples. Scanning electron micrographs for intruded and compressed specimens are presented along with a discussion on the observed hysteresis in MIP test data. The test results for kaolin samples show substantive initial compression before the occurrence of actual intrusion. This resulted in errors associated with the interpretation of pore sizes with diameters in the range of 0.4-200 µm.Key words: mercury intrusion, clay, compression, correction, pore-size distribution, high pressure.
Modelling subsidence in the Hanoi City area, Vietnam
Authors: Thu Trinh M , Fredlund Delwyn G
Published: April 2011

A study of land subsidence due to groundwater pumping in the city of Hanoi, Vietnam, was conducted by collecting and analyzing data on the geology, hydrology, soil properties, and observed settlements. The city of Hanoi is underlain by sediments consisting of organic and inorganic clays, silt, peat, sand, and gravel. The pumping of groundwater causes consolidation of compressible aquitard layers. The water demand for the city of Hanoi is increasing with time. The present total rate of water pumping is 450 000 m3/day, and there is a proposal to increase the rate to 751 000 m3/day by the year 2010. This research program involved the modelling of seepage related to pumping along with a stress-deformation analysis. The effect of surface infiltration was also modelled. The settlements computed for parts of the city of Hanoi were compared with measurements of settlement in the city area. The simulation results appear to be in fairly good agreement with the measurement results. The study showed that subsidence due to groundwater pumping is a serious problem in the city of Hanoi. It is important to continue to measure settlements and compute possible deformations associated with actual rates of pumping.Key words: subsidence, settlement, groundwater pumping, stress-deformation modelling, seepage modelling.
Shear modulus and damping ratio characteristics of gravelly deposits
Authors: Lin Shang-Yuh , Lin Ping Sien , Luo Hong-Su , Juang C Hsein
Published: April 2011

In this paper, the results of an experimental investigation of dynamic characteristics of gravelly cobble deposits, such as shear modulus (G) and damping ratio (D), are presented. The gravelly cobble deposits are very common in the Taichung metropolitan area of Taiwan where there is an urgent need to determine G and D for dynamic analysis and design of structures. The test program includes measurements of shear wave velocity by the downhole method and large-scale dynamic triaxial tests and resonant-column tests. Special consideration is given to preparing samples of gravelly cobble deposits for laboratory tests. The "equal-weight replacement method" to scale down the real gravelly deposits to cell diameters is used for the preparation of samples. This method is found to be satisfactory, as consistent and reasonable results are obtained. The results of the present study show that the shear modulus - shear strain (G-γ) relationship for this gravelly deposit does not follow exactly those reported in the literature. The deviation of this G-γ relationship from those reported in the literature is investigated and explained.Key words: shear modulus, damping ratio, downhole, shear wave velocity, gravel.
Interaction of hydroxyphenyl alkyl ketones with β-cyclodextrin
Authors: Veglia Alicia Viviana , de Rossi Rita Hoyos
Published: April 2011

Binding constants of β-cyclodextrin with six hydroxyphenyl alkyl ketones having a general structure Z-Ph-CO-(CH2)nCH3 (Z = o-OH or p-OH and n = 0, 1, or 3) were measured at 25°C by UV-vis spectrophotometry. In all cases the formation of 1:1 host-guest complexes was established. NMR chemically induced shifts indicated mixed complexation modes. Equilibrium constants are around 200 M-1 for some of the compounds and for the others around 1000 M-1. It is suggested that complexes with different geometries coexist in the solution with predominance of those with the aryl group (KSCD [Formula: see text] 200 M-1) or alkyl group (KSCD [Formula: see text] 1000 M-1) inside the cavity.Key words: inclusion complex, β-cyclodextrin, hydroxyphenyl alkyl ketones, association constants, UV-vis spectrophotometry.
Benzooxirene, naphthooxirenes, and anthraceneoxirenes: the stabilization of the oxirene system by bond fixation in acenes. A comparison of ab initio and DFT in the investigation of annelated oxirenes
Authors: Lewars E
Published: April 2011

The effect on the stabilities of benzoannelated oxirenes (oxacyclopropenes) of variations in the C-C bond electron density (as measured by Löwdin bond order) was studied computationally. Benzo[b]oxirene (4ox), naphtho[2,3-b]oxirene (5ox), naphtho[1,2-b]oxirene (6ox), anthro[2,3-b]oxirene (7ox), and anthro[1,2-b]oxirene (8ox) were investigated using the DFT pBP/DN* method as implemented in the program Spartan. This method was chosen because with 4ox it gave results similar to those from the much slower QCISD(T)/6-31G*//MP2(full)/6-31G* and MP4SDTQ/6-31G*//MP2(full)/6-31G* methods. The calculated barriers to oxirene ring opening for the "linear" 4ox, 5ox, and 7ox (bond orders 1.35, 1.24, and 1.20, respectively) were 23.6, 39.9, and 46.6 kJ mol-1, in contrast to the "angular" 6ox and 8ox (bond orders 1.50 and 1.59, respectively), with barriers of ca. 0 kJ mol-1. The high-barrier vs. low-barrier series corresponds to the stabilities expected from the resonance structures of the oxirenes or their formal precursor acenes. Empirically, the ring-opening barriers were linearly related to the oxirene bond orders, and extrapolation to tetracene using this relationship gave a barrier of ca. 50 kJ mol-1, which seems to be the limiting barrier in the linear series. In several cases the oxirene isomerized to a ketene without going through an oxo carbene (ketocarbene). Benzoannelation is only the second kind of substitution (after dimethyl substitution) that has been indicated, computationally, to be able to stabilize oxirenes.Key words: oxirenes, ketocarbenes, benzooxirenes, AM1, ab initio, DFT.
The solid-state structures of (-)-scopolamine free base, (-)-scopolamine methobromide, (-)-scopolamine hydrobromide trihydrate, and of the pseudopolymorphic forms of (-)-scopolamine hydrochloride anhydrate and 1.66hydrate
Authors: Glaser Robert , Shiftan Dror , Drouin Marc
Published: April 2011

(-)-Scopolamine hydrochloride anhydrate gives crystals belonging to the orthorhombic space group P212121 and at 293(2) K: a = 7.097(2), b = 10.686(2), c = 22.623(2) Å, V = 1715.7(6) Å3, Z = 4, R(F) = 0.039, and Rw(F) = 0.053. (-)-Scopolamine hydrochloride 1.66hydrate yields crystals belonging to the tetragonal space group P43212 and at 293(2) K: a = b = 11.843(6), c = 26.211(4) Å, V = 3676(3) Å3, Z = 8, R(F) = 0.047, and Rw(F2) = 0.135. (-)-Scopolamine methobromide affords crystals belonging to the orthorhombic space group P212121 and at 293(2) K: a = 7.0403(8), b = 10.926(2), c = 23.364(5) Å, V = 1797.2(6) Å3, Z = 4, R(F) = 0.039, and Rw(F) = 0.052. The two hydrochloride pseudopolymorphs were isostructural to the corresponding two hydrobromide analogues. Both hydrohalide hydrated crystals have a water molecule occupying a general position of symmetry, and another water molecule occupying a special position of C2-rotation symmetry. The hydrated hydrochloride salt also had an additional 0.322(17) partial occupancy water molecule (absent in the hydrobromide sesquihydrate) occupying another special position of C2-rotation symmetry, i.e., the extra water molecule occupied the special position in statistically ca. one-third of the unit-cells to give a total hydrate stoichiometry of 1.66 molecules of water. While the two hydrohalide anhydrates exhibited extended tropate ester conformations (phenyl-ring antiperiplanar to oxirane moiety) vs. compact conformations (phenyl-ring near the scopine underside) for the two hydrated hydrohalides, all four displayed other common structural features: axial N-methyl stereochemistry, antiperiplanar methylol oxygen/aromatic C(ipso) relationships, and phenyl-ring eclipsing of the C(alpha)-H bond. The CPMAS 13C NMR spectrum of (-)-scopolamine hydrobromide "trihydrate" shows it to be a conglomerate of (-)-scopolamine hydrobromide sesquihydrate plus two or more hydrated species (three ca. equal intensity carbonyl signals at 5.0 kHz spin-rate). High-speed rotor spinning (e.g., ca. 10 kHz and higher) causes a temperature-induced phase-transition to yield only the sesquihydrate form. The same transformation was noted with a 18 K rotor-temperature increase and an invariant 5.0 kHz spin-rate. The sesquihydrate spectrum remained after spin-rate decrease to 5.0 kHz, but the three component mixture 5.0 kHz spectrum was regenerated after three weeks sample storage within the capped rotor. The (-)-scopolamine free base crystalline melt CPMAS spectrum also shows a mixture of at least three hydrated species.Key words: stereochemistry, X-ray crystallography, solid-state NMR, CPMAS, anticholinergic.
Electrocatalytic hydrogenation of lignin models at Raney nickel and palladium-based electrodes
Authors: Cyr André , Chiltz Florence , Jeanson Paul , Martel Anna , Brossard Louis , Lessard Jean , Ménard Hugues
Published: April 2011

The electrocatalytic hydrogenation (ECH) of β-O-4 lignin model compounds has been carried out at constant current at Raney nickel and palladium-based cathodes in aqueous sodium hydroxide solution at temperatures ranging from 25 to 75°C. It was found that the hydrogenolysis of phenolic β-arylethyl-aryl ethers with one β-O-4 linkage takes place at both types of electrodes to give a mixture of phenolic compounds. The ECH of 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)-1-ethanol (model 1) at Raney nickel gives guaiacol (9), acetovanillone (11b), alpha-methylvanillyl alcohol (12b), and products derived from their further hydrogenation. The β-O-4 bond is more difficult to cleave upon replacing one hydrogen of the methylene group of 1 by a hydroxymethyl group (see 2). However, model 4 with two β-O-4 linkages obtained by the introduction of an α-methylvanillyl group at the phenolic position of 1 is hydrogenolysed at the same rate as 1 at Raney nickel. Only the C-O aryl bond attached to the hydroxyethylphenol moiety is cleaved. At palladium, the hydrogenolysis of 1 requires only half of the theoretical amount of electricity due to the generation of chemisorbed hydrogen by dehydrogenation of 1 followed by hydrogenolysis of the resulting ketone. A general reaction scheme is proposed for the ECH of model 1.Key words: Lignins, lignin models, electrocatalytic hydrogenation, Raney nickel electrodes, palladium electrodes.