bluuebunny/crossref_metadata_2025 huggingface dataset:
Necrotizing pneumonia and sepsis due to Clostridium perfringens: a case report
Authors: Palmacci Cristina , Antocicco Manuela , Bonomo Lorenzo , Maggi Fabio , Cocchi Alberto , Onder Graziano
Published: February 2009

Clostridia are uncommon causes of pleuropulmonary infection. Clostridial species infecting the pleuropulmonary structures characteristically cause a necrotizing pneumonia with involvement of the pleura. Most cases have iatrogenic causes usually due to invasive procedures into the pleural cavity, such as thoracentesis or thoracotomy, or penetrating chest injuries. Rarely clostridia pleuropulmonary infections are not related to these factors. The clinical course of pleuropulmonary clostridial infections can be very variable, but they may be rapid and fatal. We report a rare case of necrotizing pneumonia and sepsis due to Clostridium perfringens not related to iatrogenic causes or injuries in an 82 years old woman.
Hyperglycaemia results from beta-cell dysfunction in critically ill children with respiratory and cardiovascular failure: a prospective observational study
Authors: Preissig Catherine M , Rigby Mark R
Published: February 2009

Introduction

Hyperglycaemia is common in critical illness and associated with poor outcome. Glycaemic control using insulin may decrease morbidity and mortality. Many questions remain about the cause of critical illness hyperglycaemia (CIH). Our objective was to investigate the endocrinological basis of paediatric CIH.

Methods

C-peptide and blood glucose (BG) levels were assessed in 41 children aged 2 to 18 years old who were admitted to our paediatric intensive care unit (PICU). Patients who developed CIH, defined as persistent BG above 7.7 mmol/L, were treated with insulin infusion to achieve BG levels between 4.4 and 7.7 mmol/L. C-peptide levels were compared with respect to CIH development and degree of organ failure in all patients. Respiratory and cardiovascular failure were defined as need for mechanical ventilation and need for vasoactive infusions, respectively. Clinical and laboratory parameters, including c-peptide levels, were assessed.

Results

Of 41 children enrolled, 18 had respiratory failure only, 11 had both respiratory and cardiovascular failure, and 12 had neither respiratory or cardiovascular failure. Nine patients with respiratory failure only, 10 with both respiratory and cardiovascular failure, and none with no respiratory or cardiovascular failure developed CIH. Patients with CIH and respiratory and cardiovascular failure (n = 10) had very low c-peptide levels (4.4 ng/mL) despite significantly elevated mean BG levels (10.8 mmol/L), while those with CIH and respiratory failure only had very high c-peptide levels (11.5 ng/mL) with mean BG of 9.9 mmol/L. Low endogenous insulin production in those with respiratory and cardiovascular failure was associated with rapid onset of CIH, illness severity, higher insulin requirement and longer mechanical ventilation days, PICU length of stay and CIH duration.

Conclusions

Primary beta-cell dysfunction as defined by low endogenous c-peptide production appears to be prevalent in critically ill children with both respiratory and cardiovascular failure who develop CIH, whereas elevated insulin resistance appears to be the prominent cause of CIH in children with respiratory failure only. Our finding that beta-cell dysfunction is present in a subset of critically ill children with CIH challenges the assertion from adult studies that CIH is primarily the result of elevated insulin resistance.
The role of Dpp and Wg in compensatory proliferation and in the formation of hyperplastic overgrowths caused by apoptotic cells in theDrosophilawing disc
Authors: Pérez-Garijo Ainhoa , Shlevkov Evgeny , Morata Ginés
Published: February 2009

Non-lethal stress treatments (X-radiation or heat shock) administered to Drosophila imaginal discs induce massive apoptosis, which may eliminate more that 50% of the cells. Yet the discs are able to recover to form final structures of normal size and pattern. Thus, the surviving cells have to undergo additional proliferation to compensate for the cell loss. The finding that apoptotic cells ectopically express dpp and wgsuggested that ectopic Dpp/Wg signalling might be responsible for compensatory proliferation. We have tested this hypothesis by analysing the response to irradiation-induced apoptosis of disc compartments that are mutant for dpp, for wg, or for both. We find that there is compensatory proliferation in these compartments, indicating that the ectopic Dpp/Wg signalling generated by apoptotic cells is not involved. However, we demonstrate that this ectopic Dpp/Wg signalling is responsible for the hyperplastic overgrowths that appear when apoptotic (`undead') cells are kept alive with the caspase inhibitor P35. We also show that the ectopic Dpp/Wg signalling and the overgrowths caused by undead cells are due to a non-apoptotic function of the JNK pathway. We propose that the compensatory growth is simply a homeostatic response of wing compartments, which resume growth after massive cellular loss until they reach the final correct size. The ectopic Dpp/Wg signalling associated with apoptosis is inconsequential in compartments with normal apoptotic cells, which die soon after the stress event. In compartments containing undead cells, the adventitious Dpp/Wg signalling results in hyperplastic overgrowths.
Lesch-Nyhan disease: from mechanism to model and back again
Authors: Jinnah H. A.
Published: February 2009

Lesch-Nyhan disease (LND) is a rare inherited disorder caused by mutations in the gene encoding hypoxanthine-guanine phosphoribosyltransferase (HPRT). LND is characterized by overproduction of uric acid, leading to gouty arthritis and nephrolithiasis. Affected patients also have characteristic neurological and behavioral anomalies. Multiple cell models have been developed to study the molecular and metabolic aspects of LND, and several animal models have been developed to elucidate the basis for the neurobehavioral syndrome. The models have different strengths and weaknesses rendering them suitable for studying different aspects of the disease. The extensive modeling efforts in LND have questioned the concept that an ‘ideal’ disease model is one that replicates all of its features because the pathogenesis of different elements of the disease involves different mechanisms. Instead, the modeling efforts have suggested a more fruitful approach that involves developing specific models, each tailored for addressing specific experimental questions.
The cell cycle and beyond: an interview with Paul Nurse
Authors: Smith Jim
Published: February 2009

Sir Paul Nurse is a recipient of the 2001 Nobel Prize in Medicine for his work on one of the key regulators of the cell cycle, CDK (cyclin-dependent kinase). In this interview with Jim Smith, he discusses his choice of model organism, scientific leadership and the early influences on his career.
Courting change
Authors: Siegel Vivian
Published: February 2009

In scientific communication, the long tail has not yet appeared. Why not?
Assessment of post-traumatic stress disorder in veterans by videoconferencing and by face-to-face methods
Authors: Porcari Carole E , Amdur Richard L , Koch Ellen I , Richard David CS , Favorite Todd , Martis Brian , Liberzon Israel
Published: February 2009

We compared videoconferencing and face-to-face (FTF) assessments for veterans seeking a mental health evaluation for post-traumatic stress disorder (PTSD). The Clinician-Administered PTSD Scale (CAPS) interview was used in 20 male veterans. There were significant correlations (ranging from 0.74 to 0.92) between the CAPS administered FTF and by videoconferencing on all three subscales, as well as on the total severity score. The confidence intervals for the CAPS scores indicated statistical equivalence between administration FTF and by videoconferencing. The sensitivity of videoconferencing was 0.94 and the specificity was 0.33, compared with FTF assessment. The total and subscale scores suggested that there was a moderate working alliance with both methods. The patients indicated general satisfaction with the videoconferencing method. Most of them indicated that they would prefer to see a clinician FTF, but would utilize videoconferencing if there were distance barriers to services. Overall, the results of the present study support the use of videoconferencing in the assessment of PTSD.
A university extension course in leprosy: telemedicine in the Amazon for primary healthcare
Authors: Paixão Maurício Pedreira , Miot Hélio Amante , de Souza Pedro Elias , Haddad Ana Estela , Wen Chao Lung
Published: February 2009

There is a high prevalence of leprosy in the Amazon region of Brazil. We have developed a distance education course in leprosy for training staff of the Family Health Teams (FHTs). The course was made available through a web portal. Tele-educational resources were mediated by professors and coordinators, and included the use of theoretical content available through the web, discussion lists, Internet chat, activity diaries, 3-D video animations (Virtual Human on Leprosy), classes in video streaming and case simulation. Sixty-five FHT staff members were enrolled. All of them completed the course and 47 participants received a certificate at the end of the course. At the end of the course, 48 course-evaluation questionnaires were answered. A total of 47 participants (98%) considered the course as excellent. The results demonstrate the feasibility of an interactive, tele-education model as an educational resource for staff in isolated regions. Improvements in diagnostic skills should increase diagnostic suspicion of leprosy and may contribute to early detection.
Follow-up data for patients managed by store and forward telemedicine in developing countries
Authors: Wootton Richard , Menzies John , Ferguson Paula
Published: February 2009

There is very little published information about the outcomes of patients treated by telemedicine in developing countries. Over a two-year period, seven medical students from five universities spent their electives at a hospital in Papua New Guinea. They assisted with the review of a total of 44 e-referrals made by local doctors; the referrals resulted in 61 queries in a wide range of specialties. The major categories of these queries were internal medicine, paediatrics and surgery. Follow-up data were obtained in 22 of the 44 cases (50%) after a median period of 13 weeks (interquartile range 3-19). The cases were reviewed by an independent doctor. Telemedicine was considered to have assisted with the diagnosis in all cases (median score 5 on a five-point scale from 1 = not helpful at all to 5 = very good/excellent). The advice to the referring doctor for further action was considered helpful in all except one case (median score 5 on the same scale). The outcome for the patient was considered to be good in 15 of the cases (median score 4 on the same scale). Medical students were able to facilitate e-referrals by relieving the pressure on the local doctor to undertake the necessary clerical and technical work. The students reported a rewarding elective experience. The follow-up data showed that low-cost telemedicine can provide useful advice in a low resource setting.
Biomedical and Biotechnology Licensing Issues after MedImmune
Authors: Olson Bradley J.
Published: February 2009

The U.S. Supreme Court's opinion in
Percussion and Cone Methods of Determining the Liquid Limit of Soils: Controlling Mechanisms
Authors: Sridharan A , Prakash K
Published: February 2009

The mechanisms controlling the liquid limit of montmorillonitic and kaolinitic soils are different. The observation that the liquid limits obtained by both the conventional percussion method and the cone penetration method differ quite appreciably from each other at low and high plasticity ranges indicates that the mechanisms dominating the two testing procedures are different. The analysis of the results obtained from the present experimental investigation, and the results available in the literature prove that the viscous shear resistance primarily controls the percussion method of testing, and that the frictional shear resistance dominates the cone method of testing. Since the viscous shear resistance is primarily due to the double-layer held water, which is characteristic of montmorillonitic soils, and the liquid limit of montmorillonitic soil is primarily governed by the diffuse double layer thickness, the percussion method is well suited to montmorillonitic soils. Likewise, as the interparticle frictional resistance is due to the mode of particle arrangement in addition to mineral frictional characteristics, and the same primarily controls the liquid limit of kaolinitic soils, the cone method suits kaolinitic soils better.
The Influence of Biofilm on the Mechanical Behavior of Sand
Authors: Perkins SW , Gyr P , James G
Published: February 2009

The growth of microbes on the surface of an object results in the formation of a biofilm, which in sand can lead to a reduction of hydraulic conductivity and can be used for groundwater containment and remediation. Sample preparation and testing techniques for triaxial and oedometer experiments were devised for the purpose of examining the influence of biofilm on the stress-strain-time properties of Ottawa sand. Results have shown that biofilm has a negligible influence on the strength and stiffness of the sand but increases time-dependent creep deformation. An elasto-viscoplastic constitutive model was calibrated for biofilm and non-biofilm sand and implemented into a finite-element code for the purpose of predicting creep deformation of a slope and a foundation resting on level ground. Numerical simulations showed that additional creep behavior of the biofilm sand had a negligible influence on the behavior of these geotechnical engineering facilities.
Dynamic Properties of Granulated Rubber/Sand Mixtures
Authors: Feng Z-Y , Sutter KG
Published: February 2009

Processed waste tires mixed with soils are applicable in lightweight fills for slopes, retaining walls, and embankments that may be subjected to seismic loads. Rubber's high damping capacity permits consideration of granulated rubber/soil mixtures as part of a damping system to reduce vibration. The dynamic properties of granulated rubber/soil mixtures are essential for the design of such systems. This research investigates the shear modulus and damping ratio of granulated rubber/sand mixtures using a torsional resonant column. Specimens were constructed using different percentages of granulated tire rubber and Ottawa sand at several different percentages. The maximum shear modulus and minimum damping ratio are presented with the percentage of granulated rubber. It is shown that reference strain can be used to normalize the shear modulus into a less scattered band for granulated rubber/sand mixtures. The normalized shear modulus reduction for 50% granulated rubber (by volumme) is close to a typical saturated cohesive soil. Empirical estimation of maximum shear modulus of soil/rubber mixtures can be achieved by treating the volume of rubber as voids.
A New Device for Measuring Permeability Under High Gradients and Sinusoidal Gradients
Authors: Khalifa M-AOA , Wahyudi I , Thomas P
Published: February 2009

This paper presents the design and testing procedures for a new type of permeameter that combines the methods of a constant-head permeameter for large hydraulic gradients (used to simulate hydraulic gradients in centrifuged geotechnical models) and a sinusoidal head permeameter (used to simulate internal flow in soils due to waves). The flow of permeant through a granular soil specimen is forced by a pump with a control servovalve used to regulate the flow rate according to the desired signal. The measurement instruments, which consist of temperature sensors, differential pressure transducers, flowmeters, and an electrical controller, are linked to a microcomputer and a data acquisition and control system that permits full automation of the tests.

Steady flow tests, carried out on fine sands with high hydraulic gradients, show that the flow is governed by Forchheimer's law. The analysis of the transient flow tests, carried out on fine sands, has shown that the classical Darcy's law is not valid when the material is subjected to a flow simulating a wave; a generalization of Darcy's law for this type of flow is proposed here.
Empirical Performance Classification for Cohesive Embankment Soils
Authors: White DJ , Bergeson KL
Published: February 2009

In response to recent evidence of poor highway embankment quality caused in part by improper soil identification and placement during construction, field-testing and laboratory analysis were conducted to develop a simple performance-based soil classification system that can be conducted in a field laboratory. Development of the Empirical Performance Classification (EPC) system is based on swell potential and frost susceptibility relationships of soils derived from liquid limit, plasticity index, and fines content (≤ 75 µm). From these parameters the EPC system is used to classify soils into one of three categories: select, suitable, or unsuitable. This paper presents the background for the development of this system and procedures for its use. A field trial in Iowa indicates that Iowa Department of Transportation field personnel can effectively use the EPC system to classify soils in the field and to link design with construction activities better. Increased field soil classification is expected to improve long-term performance of cohesive earth embankments.
Utilization of an Industrial Waste in Calcareous Expansive Clay Stabilization
Authors: Nalbantoglu Z , Gucbilmez E
Published: February 2009

The calcareous expansive soil in Cyprus has caused serious damage to structures. High-quality Soma fly ash admixture has shown tremendous potential as an economical method for the stabilization of the soil. Fly ash and lime-fly ash admixtures reduce the water absorption capacity and compressibility of the treated soils. Unlike some of the previously published research, an increase in hydraulic conductivity of the treated soils was obtained with an increase in percent fly ash and curing time. X-ray diffractograms indicate that pozzolanic reactions cause an alteration in the mineralogy of the treated soils, and new mineral formations with more stable silt-sand-like structures are produced. In the present study, an attempt has been made to use cation exchange capacity (CEC) values to substantiate the findings that, with increasing percentage of fly ash and curing time, soils become more granular in nature and show higher hydraulic conductivity values.
Evaluation of a Modified Soluble Sulfate Determination Method for Fine-Grained Cohesive Soils
Authors: Puppala AJ , Viyanant C , Kruzic AP , Perrin L
Published: February 2009

Soluble sulfate measurement in subgrade soils is an integral part of geotechnical investigations due primarily to sulfate-induced heave distress problems experienced by certain chemically treated sulfate soils. Sulfate measurements will assist engineers in the selection of appropriate soil stabilization methods in construction projects. There are no ASTM test methods that provide sulfate measurements in soils. Current methods including the University of Texas at Arlington (UTA) method, which are based on gravimetric procedures, often provide test results with high standard deviations. A modified UTA method, which was developed by addressing the limitations of the earlier methods, is presented in this paper. This procedure is evaluated for reproducible and reliable sulfate measurements in three artificial soils and one natural soil. The modified procedure provided reproducible sulfate measurements for all soils with coefficients of variations (COV) less than 10%. These results matched with ion chromatography measurements, which indicate that the modified method provided reliable measurements.
On the Identification of Critical State Lines for Sands
Authors: Klotz EU , Coop MR
Published: February 2009

New methods of geotechnical design in sands are often based on a state parameter type of approach, requiring the in situ state of the soil to be quantified relative to its critical state line. One difficulty in the application of these methods is then the correct identification of the location of this line, particularly at lower stress levels where sands strain soften and strains tend to localize within the sample. This paper examines the shearing behavior of two sands of diverse mineralogy by means of triaxial testing. The approach adopted has been to use existing techniques and apparatus that might reasonably be implemented in general practice. Recommendations are made as to the type of apparatus and test that should be used, and the corrections necessary to the data in order to identify as accurately as possible the critical states.
The Quality of Continuous Soil Samples
Authors: Long M
Published: February 2009

The quality of continuous soil samples from four typical Irish soft ground strata is studied. It was found that the MOSTAP® continuous specimens have lower initial moisture content and higher bulk density than block or tube samples. Test data from MOSTAP® samples underestimate 1D yield stress ratio, compression in the normally consolidated range and creep. Triaxial tests on the MOSTAP® specimens show erratic results. For the clays studied, they give lower undrained strength, a higher strain to failure, and a larger small strain stiffness than block samples. MOSTAP® specimen quality, however, improves with reducing soil sensitivity and increasing soil strength. These results are caused by the MOSTAP® sampler having an inferior cutting head geometry, leading to increased destructuring of the soils. In silt materials, the sampler penetration is partially drained, leading to densification of material, the effects being greatest for the MOSTAP® sampler. Recommendations are given for possible improvements to the sampler.
A Critical Assessment of the Moist Tamping Technique
Authors: Frost JD , Park J-Y
Published: February 2009

Current field sampling techniques are not readily able to produce high-quality undisturbed granular soil specimens for laboratory testing at an affordable cost. Accordingly, numerous specimen reconstitution methods have been developed for use in the laboratory. Among these methods, moist tamping has the advantage that it is relatively easy to control the global specimen density achieved, even for loose specimens, although unfortunately the method has also been qualitatively shown to yield less uniform specimens. This paper describes the findings of a study that critically assessed the moist tamping method by measuring the forces applied during the tamping process and investigated the uniformity of specimens prepared with the method by quantitatively analyzing both X-ray and optical images.
A Comparative Study of Suction-Induced Seepage Consolidation Versus Centrifuge Consolidation
Authors: Robinson RG , Tan TS , Lee FH
Published: February 2009

The time required for the preparation of a normally consolidated clay sample, by self-weight consolidation in the centrifuge, is often very long and the process may take up to several days. To save centrifuge time, a hydraulic consolidation method of preparation of normally consolidated clay beds, using seepage forces, is often used prior to final consolidation in the centrifuge. At present, the required hydraulic gradient is usually generated by high-pressure water at the top of the clay bed. This method tends to cause hydraulic fracturing at comers when rectangular containers are used. A simple method of using vacuum suction to induce seepage forces to clay samples is proposed and discussed in this paper. Experience with this method shows practically no incidence of hydraulic fracturing. Comparison of the variation of water content and shear strength with depth of samples prepared by the present method and those prepared exclusively by self-weight consolidation in the centrifuge lends support to the validity and effectiveness of the proposed method. The method can be used to prepare clay samples for prototype depth less than about 17 m. A procedure for estimating the final height, water content, and shear strength profiles of the soil model prepared is also presented.
Laboratory and Field Shear Wave Measurement at a Reclaimed Site in West Taiwan
Authors: Chien L-K , Oh Y-N
Published: February 2009

Land reclamation using hydraulic sand fills is a method adopted widely in West Taiwan. In this paper, the influence of fines content, void ratio, and effective confining pressure on the measurement of shear wave velocity of reclaimed soil obtained from the reclaimed soil in the Yun-Lin area of West Taiwan is discussed. A “critical s-wave void ratio” (ef.c.) is defined. As shown in the results, for critical s-wave void ratio (ef.c.) with 10% of fines content, there exists a maximum shear wave velocity. As the fines content exceeds 10%, the shear wave velocity decreases. Based on the laboratory and in-situ test, a modification factor (M) is defined. From the results, the modifications factor (M) increases as the soil depth increases. The results presented can be a reference for soil property evaluation in land reclamation and coastal area.
Oxygen Diffusion Coefficient of Soils at High Degrees of Saturation
Authors: Shelp Lin M , Yanful EK
Published: February 2009

The oxygen diffusion coefficient is an essential parameter for design of soil covers over mine waste. This study presents a method for measuring the oxygen diffusion coefficient of soils at high degrees of saturation. The method eliminates measurement errors caused by soil microbial activity, high humidity, and stagnant air in laboratory diffusion cells. Results show that microbial activity is an important factor that causes errors in O2 measurements. Sterilization of soil, utilization of a silica gel-membrane system with oxygen sensors, and minimal stirring in the cell headspace greatly reduce the variability in O2 diffusion coefficient measurements. The variations in estimated O2 diffusion coefficients for the same soil at the same degree of saturation were ±31% about the mean for clayey soil samples and ±10% about the mean for silty soil samples.
Model Studies on Geocell Supported Embankments Constructed Over a Soft Clay Foundation
Authors: Krishnaswamy NR , Rajagopal K , Madhavi Latha G
Published: February 2009

This paper describes the results of laboratory model tests on geocell-supported earth embankments constructed over a soft clay foundation. The soft clay foundation was prepared in a large test tank to a depth of 600 mm. A single geocell layer was formed on this clay foundation with different thicknesses, and embankments were constructed above this layer. Four different types of geogrids were used for the formation of the geocell layer. The embankments were subjected to uniform surcharge pressure on the crest until failure. The vertical and horizontal deformations and the strains developed within the geocell layer were measured during the test. The influence of various parameters such as tensile stiffness of geogrids used to fabricate the geocell material, height, and pocket-size of the geocell layer, length of the geocell layer, and type of fill material inside the geocell on the behavior of the embankments was investigated through a series of laboratory tests.
Evaluation and Application of the Transient-Pulse Technique for Determining the Hydraulic Properties of Low-Permeability Rocks—Part 1: Theoretical Evaluation
Authors: Zhang M , Takahashi M , Morin RH , Esaki T
Published: February 2009

The transient-pulse technique is a well-established laboratory method for determining the permeability of hydraulically tight rocks. Although graphical solutions to this test make it possible to evaluate both the permeability and the specific storage of a rock specimen, the attendant procedures are relatively complicated. Often, the expression introduced by Brace et al. (1968) is typically used to interpret the experimental results and arrive at a value for permeability only. In Part 1 of this study, the general solution for the transient-pulse test is extended to consider quantitatively the transient distributions of hydraulic head and hydraulic gradient within the specimen and to examine the validity of using the solution presented by Brace et al. (1968) under these conditions. Based on a series of parametric studies, some theoretical and practical considerations related to the design of a transient-pulse test are also provided. In Part 2, a relatively convenient and general approach to calculating the specific storage of a specimen from a transient-pulse test is presented and its efficiency is demonstrated through the application of this approach to experimental investigations.
Evaluation and Application of the Transient-Pulse Technique for Determining the Hydraulic Properties of Low-Permeability Rocks—Part 2: Experimental Application
Authors: Zhang M , Takahashi M , Morin RH , Esaki T
Published: February 2009

In Part 1 of this study, the general solution to the transient-pulse test (Hsieh et al. 1981) was extended to evaluate quantitatively the transient variations in hydraulic head and the corresponding distributions of hydraulic gradient within a test specimen. In addition, the conditions and the validity of using the expression proposed by Brace et al. (1968) to compute the low permeability of a rock specimen from a transient-pulse test were examined. Some theoretical considerations related to the optimal design of a transient-pulse test were also discussed. Part 2 presents a relatively general and convenient approach for determining not only the hydraulic conductivity and specific storage of a specimen directly from a transient-pulse test, but also the compressive storage of the fluid reservoirs. The accuracy and efficiency of this method are demonstrated through (1) the comparison of the compressibility of the fluid-reservoir (permeating) system back-calculated from the transient-pulse tests with the value obtained from calibration tests, and (2) its application to a series of experimental studies designed to investigate the effects of confining pressure on the hydraulic properties of Shirahama sandstone and Inada granite, two rock types available widely in Japan.
A New Technique for Simulation of Tunnel Excavation in a Centrifuge
Authors: Sharma JS , Bolton MD , Boyle RE
Published: February 2009

A new technique is presented for the simulation in a centrifuge of the excavation and lining of a model tunnel. It involves the use of a polystyrene foam core that is placed tightly inside the tunnel lining and that can be dissolved using an organic solvent. This technique is an improvement over other contemporary methods of modeling tunnel construction, such as reduction of air pressure supporting the tunnel lining or gradually draining zinc chloride solution (or some other heavy liquid) from within the lining. The stiffness of the filled tunnel can, approximately, be made to simulate the parent soil. The stiffness of the lining is correctly left in place when the foam core has been dissolved. Since there is no air or fluid pressure involved, there is also no need to seal the ends of the tunnel segment. Results from the first few trials of this technique in a 2 m diameter drum centrifuge are presented. These results demonstrate the usefulness of the technique in modeling progressive collapse of a tunnel and show ample promise of its use in the modeling of the construction of a tunnel using the NATM (New Austrian Tunneling Method).
Simultaneous Measurement of Surface Wave Dispersion and Attenuation Curves
Authors: Rix GJ , Lai CG , Foti S
Published: February 2009

In existing surface wave test procedures, experimental dispersion and attenuation curves are determined separately (i.e., uncoupled) using different source-receiver configurations and different interpretation methods. A new procedure based on displacement transfer functions is proposed in which dispersion and attenuation data are derived simultaneously (i.e., coupled) from a single set of measurements using the same source-receiver array. The new approach is motivated by the recognition that in dissipative media, Rayleigh phase velocity and attenuation are not independent as a result of material dispersion. Therefore, a coupled analysis of dispersion and attenuation is a more robust, fundamentally correct approach. The new approach is also more consistent with coupled inversion techniques to obtain the shear wave velocity and shear damping ratio profiles. The proposed approach is illustrated using data measured at a site in Atlanta, Georgia.
Influence of Peripheral Velocity on Vane Shear Strength of an Artificial Clay
Authors: Biscontin G , Pestana JM
Published: February 2009

Shearing rate is among the most important factors affecting the undrained shear strength of clays. In particular, for seismic or storm-wave loading conditions, the shearing rate is much higher than that used in many common laboratory or field tests. The testing program described here evaluates the effect of peripheral velocity on the undrained strength inferred from the shear vane test. The study was conducted on a lightly cemented bentonite-kaolinite mixture manufactured in the laboratory, which possesses many characteristics similar to those of natural materials. Results show that the shear strength increases with increasing peripheral velocity, while the residual shear strength seems to be nearly independent of rotation rate.
Determining the Maximum Density of Sands by Pluviation
Authors: Cresswell A , Barton ME , Brown R
Published: February 2009

Experiments have been carried out to find the maximum dry density taken up by sands during pluviation. These experiments were facilitated by use of a flow divider that permitted very low depositional intensities. It was found that the maximum dry density occurred at an optimum pluviation time. Careful observation of the pluviating sand reveals that compaction takes place within an “energetic layer” of 3 to 4 grains in thickness and that maximum dry density requires the full and continuous development of this layer. Further experiments were conducted to compare simple pouring without diffuser meshes with pluviation: it is shown that at very slow rates of pour, pouring gives the same density as pluviation.
Mechanical Behavior of a Pulverized Fly Ash Grouted Sand
Authors: Markou IN , Atmatzidis DK
Published: February 2009

A laboratory investigation was conducted in order to develop a new grout based on pulverized fly ash. Pulverization of a selected Greek fly ash yielded a gradation with D15 = 1.3 µm, D50 = 6 µm, and D85 = 20 µm and Blaine specific surface approximately equal to 8300 cm2/g. Suspensions of this pulverized fly ash, improved with additives, have comparable properties to ordinary and microfine cement suspensions. Suspensions were injected into clean sands. Permeability, UU, and CU-PP triaxial compression tests were conducted on the grouted specimens. The coefficient of permeability of the sands is reduced by 4 to 7 orders of magnitude. Grouting increases the stiffness and reduces the deformability of the sands. The Mohr-Coulomb failure criterion represents adequately the behavior of the grouted sands, yielding cohesion values ranging from 290 to 450 kPa and angle of internal friction values up to 5° higher than those of the clean sands. The shear strength parameters vary with axial strain, attaining their final values well before failure.
The Use Of Embedded Stress Cells For Monitoring Pavement Performance
Authors: Gonçalves PF , Ceratti JAP , Damiani Bica AV
Published: February 2009

This paper discusses factors that influence the performance of stress cells embedded in pavement test sections. Accelerated testing of two instrumented flexible pavement sections was carried out using a linear traffic simulator. Interesting data were obtained from stress cells embedded in the clayey subgrade. For both sections, the vertical stress inside this layer was shown to increase with axle load repetition. It also appeared to correlate well with the corresponding increase of surface rutting. The interpretation of these data required a previous investigation of stress cell performance using both laboratory and in situ calibration tests. Details of pavement testing and cell calibration procedures are also described in this paper.
Consolidation and Permeability of Transparent Amorphous Silica
Authors: Liu J , Iskander MG , Sadek S
Published: February 2009

The consolidation and permeability of transparent amorphous silica are studied in this paper. Transparency is achieved by matching the refractive indices of the amorphous silica particles and the pore fluid. The fundamental premise of this research is that transparent synthetic soils made of amorphous silica can be used in model tests to study three-dimensional deformation and flow problems, using nonintrusive optical visualization techniques, if amorphous silica can be produced with geotechnical properties similar to natural soils. The amorphous silicas studied in this paper exhibit consolidation behavior similar to that of organic clays and peat. The permeability of the material falls within the range typically reported for clays and peats.
Design Criteria for Geotomographic Field Studies
Authors: Fernandez A , Santamarina JC
Published: February 2009

The tomographic inversion of boundary measurements permits determining the spatial distribution of a material property within a soil mass. The most common geotomographic setup for wave-based measurements (mechanical or electromagnetic) consists of two arrays of transducers, one with sources and the other with receivers. The separation between the arrays and the number of sources and receivers have to be determined for every new field condition in order to satisfy resolution requirements in view of physical processes and mathematical constraints. The adequate design of a geotomographic study maximizes the amount of information gathered in the field, renders the maximum possible resolution within the physical constrains associated with field conditions and the available instruments, and prevents unnecessary measurement duplication.
Absorption Water Content and Liquid Limit of Soils
Authors: Sridharan A , Nagaraj HB
Published: February 2009

Consistency limits are extensively used in geotechnical engineering practice. Besides the consistency limits, the plasticity index, liquidity index, and consistency index have been used to correlate with engineering properties. The test procedures that have been developed to determine liquid limit are based on the strength criterion, and the liquid limit corresponds to a shearing resistance of 1.7 to 2.0 kPa. However, the mechanisms controlling the test procedures do not simulate the mechanisms controlling the water-holding capacity of soils that the liquid limit is supposed to represent. In this paper an attempt has been made to devise a test procedure, known as the absorption test, which simulates the mechanisms controlling the water holding-capacity of soils. The equilibrium water content reached by the dry soil pats starting at shrinkage limit void ratio is found to have a good correlation with the conventional liquid limit obtained from the cone penetrometer method.
Unsaturated Hydraulic Conductivity of Mine Tailings Under Wetting and Drying Conditions
Authors: Rassam DW , Williams DJ
Published: February 2009

The unsaturated hydraulic conductivity of a soil-like material required in flow models is usually quantified with the aid of predictive models. In this study, an optimum set of input parameters for Campbell's hydraulic conductivity function was estimated. The resulting hydraulic conductivity relationship was compared to that obtained using the van Genuchten model. A flow cell was developed in which transient water contents and matric suctions were monitored while the soil underwent drying and wetting cycles. A one-dimensional numerical model was used to simulate the experimental flow problem for a wide range of input parameters. The sum of the square of the differences (SSD) between the observed and simulated water contents was calculated. The parameters corresponding to the minimum SSD were used to establish three hydraulic conductivity relationships for drying, wetting, and redrying conditions. For wetting conditions, the relative hydraulic conductivity function calibrated against the estimated optimum saturated hydraulic conductivity compared well with the measured unsaturated hydraulic conductivity. A lower-saturated hydraulic conductivity was required to calibrate the hydraulic conductivity function for drying conditions.
A Complex Permittivity Measurement System for Undisturbed/Compacted Soils
Authors: Shang JQ , Rowe RK , Umana JA , Scholte JW
Published: February 2009

The design and calibration of a complex permittivity measurement device for undisturbed and compacted soils is presented. The system consists of an automatic network analyzer, a sample holder, coaxial cables, and software to process data. The design of the sample holder and the limitations and sources of errors in the measurement system are discussed. The complex permittivities of two natural clayey soils were measured over the frequency range of 0.3 MHz to 1.3 GHz. For the soils tested, the dielectric constants and volumetric water contents showed a linear trend that was independent of the soil type. It was found that when performing the complex permittivity measurements the soil specimen length should be kept constant and as short as possible while ensuring that the sample is representative of the in-situ soil fabric and grain-size distribution.
Determination of the Plasticity Index from Flow Index
Authors: Sridharan A , Nagaraj HB , Prakash K
Published: February 2009

The flow index (If), which is the slope of the water content versus log10 (number of blows) plot in the percussion cup method or the slope of the water content versus log10 (depth of penetration) plot of the cone penetration method of determining the liquid limit of soils is a measure of soil plasticity. Hence, the plasticity index of a soil that represents the soil plasticity can be correlated with the flow index.

Analysis of test data pertaining to soils of widely varying plasticity characteristics and geological origin indicates that there is an excellent correlation between the plasticity index and the flow index, particularly in the cone penetration method. In this paper, a simple equation has been suggested to obtain the plasticity index of a soil from the flow index, thereby eliminating the dependence of the plasticity index determination on the time-consuming and unrefined plastic limit test.
Development of a Stress/Suction-Controlled True Triaxial Testing Device for Unsaturated Soils
Authors: Hoyos LR , Macari EJ
Published: February 2009

A servo-controlled, true triaxial (cubical) testing apparatus has been modified to test 10-cm cubical specimens of unsaturated soil under suction-controlled conditions and for a wide range of stress paths. The equipment is a mixed-boundary type of device, with the specimen seated on top of a saturated high-air-entry disk and between five flexible membranes on the remaining sides of the cube. This paper describes the development of the device, including details of main apparatus components, specimen preparation, step-by-step assembling procedure, and the corresponding validation of its suitability for testing unsaturated soils. The device features two independent pore-air pressure and pore-water pressure control/monitoring systems. Matric suction states in the specimens are induced and maintained constant during testing by using the axis-translation technique. A companion paper (Macari and Hoyos Jr. 2001) presents the results from a comprehensive experimental study of the stress-strain response of a recompacted silty sand following simple-to-complex stress paths under suction-controlled conditions.
A Flat Dilatometer to Operate in Glacial Tills
Authors: Akbar A , Clarke BG
Published: February 2009

The Marchetti flat dilatometer is a simple to operate in-situ testing device that was designed for use in clays, silts, and sands. A new dilatometer has been developed for use in a greater variety of soil types, in particular glacial tills. This probe is more robust than the Marchetti dilatometer because it uses a rigid piston instead of a flexible membrane to load the soil. The new dilatometer is also a research dilatometer incorporating a displacement transducer and pressure transducer. This allows an applied pressure displacement curve to be produced. Tests have been carried out at several sites to compare results from the two dilatometers, check the robustness of the new dilatometer, and produce data to establish new correlations.
Determining Hydraulic Conductivity of Soil-Bentonite Using the API Filter Press
Authors: Filz GM , Henry LB , Heslin GM , Davidson RR
Published: February 2009

The American Petroleum Institute (API) filter press is commonly used to measure the hydraulic conductivity of soil-bentonite, both during mix design and as a part of construction quality assurance and quality control. However, interpretation of the test results is complicated by the fact that, during the test, the soil-bentonite specimen is consolidated by seepage forces, which produce a variation in effective consolidation stress from the top of the specimen to the bottom. This paper presents the results of a laboratory investigation undertaken to illustrate that seepage consolidation theory provides a logical way to interpret filter press test results. A description of seepage consolidation theory, which relates stress, compressibility, and hydraulic conductivity in soil consolidated by seepage forces, is presented. Following this is a description of the laboratory testing program that involved comparing the hydraulic conductivity of two soil-bentonite mixes, as measured in rigid wall consolidometer permeameter cells, a flexible wall permeameter, and an API filter press. Using seepage consolidation theory to interpret the filter press tests produces hydraulic conductivities consistent with those obtained from the other tests. The filter press test results are used to illustrate a method for estimating the hydraulic conductivity of soil-bentonite in a cutoff wall by taking backfill consolidation pressures into account.
A Laser Technique to Quantify the Size, Porosity, and Density of Clay Clusters During Sedimentation
Authors: Likos WJ , Lu N
Published: February 2009

A technique is developed for measuring the size, porosity, and density of clay clusters (flocs) and the distributions of these fundamental quantities during sedimentation. A laser-particle counter is used to detect cluster size and size distribution. Cluster velocities are computed by taking measurements at successive time intervals. By comparing the initial cluster size distribution with the measured distribution as sedimentation proceeds, a unique relationship between cluster size and settling velocity can be established. By applying a settling model for porous spheres, a unique relationship between cluster diameter and porosity is then established. Cluster density is calculated using fundamental mass-volume relationships. The technique and its working principles are illustrated via two sets of experiments, one for kaolinite clusters in distilled water and another for kaolinite clusters in 0.5 M NaCl. Consistent with double-layer theory, the results show that the porosity of clusters in distilled water is higher than the porosity of clusters in NaCl solution. The results also show that power-law relationships, which state that cluster porosity increases with cluster size, may not be valid for clusters very close to the primary particle size.