Evaluation of additional confinement for three-dimensional geoinclusions under general stress state

Three-dimensional cellular geoinclusions (e.g., geocells, scrap tires) offer all-around confinement to the granular infill materials, thus improving their strength and stiffness. The accurate evaluation of extra confinement offered by these geoinclusions is essential for predicting their performance in the field. The existing models to evaluate the additional confinement are based on either a plane-strain or axisymmetric stress state. However, these geoinclusions are more likely to be subjected to the three-dimensional stresses in actual practice. This note proposes a semi-empirical model to evaluate the additional confinement provided by cellular geoinclusions under the three-dimensional stress state. The proposed model is successfully validated against the experimental data. A parametric study is conducted to investigate the influence of input parameters on additional confinement. Results reveal that the simplification of the three-dimensional stress state into axisymmetric or plane-strain condition has resulted in inaccurate and unreliable results. The extra confinement offered by the geoinclusion shows substantial variation along the intermediate and minor principal stress directions depending on the intermediate principal stress, infill soil, and geoinclusion properties. The magnitude of additional confinement increases with an increase in the geoinclusion modulus. The findings are crucial for accurate assessment of the in situ performance of three-dimensional cellular geoinclusions.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Remediation of Expansive Soils Using Agricultural Waste Bagasse Ash

© 2016 The Authors. Published by Elsevier B.V. Bagasse is a fibrous material remaining after crushing sugarcane to extract its juice; and bagasse ash is produced after burning bagasse. Improper disposal of this material can create environmental problems around sugar manufacturing plants. Bagasse ash, comprising a high percentage of silica (SiO2), is considered as a sensible pozzolanic material with non-reactive behaviour and has potential to be used in road subgrade stabilisation. One of the main challenges for transportation organisations in Australia is to treat subgrades including expansive soils. Expansive soils exhibit significant movements when the moisture content changes, and hence it causes substantial damage to road pavements constructed over these type of soils. Road engineers need to employ materials having acceptable strength, relatively low price and being eco-friendly. In order to demonstrate the potential ability of bagasse ash in curtailing the adverse effects of expansive soils on roads, an array of experimental tests using bagasse ash have been conducted. In this study to activate and improve the effectiveness of bagasse ash, hydrated lime was used and mixed with black soil samples, collected from Queensland Australia. Samples were prepared using different contents of bagasse ash and hydrated lime (0%, 6%, 10%, 18% and 25% by the dry mass of soil), at a ratio of 3:1, respectively. The results of free swell ratio (FSR) test, unconfined compression strength (UCS) and California bearing ratio (CBR) tests are presented for untreated and treated samples after various curing time periods of 3, 7 and 28 days. The outcomes of these tests clearly demonstrate that stabilisation of expansive soils using bagasse ash and hydrated lime not only improves the strength, but also facilitates to cope with environmental concerns through reduction of sugar industry waste material

Performance of laterally loaded piles considering soil and interface parameters

© 2014 Techno-Press, Ltd. To investigate the soil-pile interactive performance under lateral loads, a set of laboratory model tests was conducted on remoulded test bed of soft clay and medium dense sand. Then, a simplified boundary element analysis had been carried out assuming floating pile. In case of soft clay, it has been observed that lateral loads on piles can initiate the formation of a gap, soil heave and the tension crack in the vicinity of the soil surface and the interface, whereas in medium dense sand, a semi-elliptical depression zone can develop. Comparison of test and boundary element results indicates the accuracy of the solution developed. However, in the boundary element analysis, the possible shear stresses likely to be developed at the interface are ignored in order to simplify the existing complex equations. Moreover, it is unable to capture the influence of base restraint in case of a socketed pile. To bridge up this gap and to study the influence of the initial stress state and interface parameters, a field based case-study of laterally-loaded pile in layered soil with socketed tip is explored and modelled using the finite element method. The results of the model have been verified against known field measurements from a case-study. Parametric studies have been conducted to investigate the influence of the coefficient of lateral earth pressure and the interface strength reduction factor on the results of the model

Analytical Evaluation of Ballasted Track Substructure Response under Repeated Train Loads

© 2020 American Society of Civil Engineers. The irrecoverable deformations in the substructure layers are detrimental to the track stability and demand frequent maintenance. With an escalation in axle load and traffic volume, the frequency of maintenance operations has remarkably increased. Consequently, there is an inevitable need to predict the long-term behavior of the track substructure layers. This article presents a methodology to evaluate the recoverable and irrecoverable responses of the substructure layers under the train-induced repetitive loads. The present method utilizes an integrated approach combining track loading, resiliency, and settlement models. The track substructure layers are simulated as lumped masses that are connected by springs and dashpots. The method is successfully validated against the field investigation data reported in the literature. A parametric study is conducted to investigate the influence of substructure layer properties on the track response. The results reveal that the response of each track layer is significantly influenced by the neighboring layer properties and the incorporation of multilayered track structure enables more accurate prediction of track behavior. The present analytical approach is simple, computationally efficient and may assist the practicing engineers in the safer design of the ballasted track

Diagnostic triad of pulmonary anthracofibrosis in spiral CT scan : a retrospective study

Purpose: Anthracosis, a form of pneumoconiosis commonly caused by air pollution and other environmental factors, is a new entity in respiratory disorders. Bronchoscopy and transbronchial lung biopsy (TBLB) are the gold standard of diagnosis. Herein, we evaluated the results of bronchoscopy and chest computed tomography (CT) scans of 187 anthracotic patients. Material and methods: Between April 2016 and April 2017, 187 cases (99 males, mean age 65 ± 10.2 years) who underwent flexible bronchoscopy and TBLB for various indications were considered for this study. CT examinations of these patients were reported as "blind to bronchoscopy results" by two experienced board-certified radiologists. Results: According to the results of bronchoscopy and TBLB, 100 patients were diagnosed as anthracotic. CT scans confirmed 71 of these cases as anthracosis. Sensitivity, specificity, PPV, NPV, and accuracy of hyperdense non-calcified mediastinal and hilar lymph nodes, known as "brilliant lymph nodes", compared to bronchoscopy were 55%, 92%, 89%, 64%, and 72%, respectively (CI: 95%). Also, there was a positive correlation between anthracosis and brilliant lymph nodes (p-value = 0). Analysis of hyper-attenuated lung with bronchoscopy estimated sensitivity, specificity, PPV, NPV, and accuracy gave 41%, 94%, 89%, 58%, and 65%, respectively (CI: 95%). The specificity of brilliant lymph nodes, hyper-attenuated lung, and multi-segmental atelectasis as a diagnostic "triad of anthracosis" was 100%. Conclusions: Based on our analyses, the triad of brilliant lymph nodes, hyper-attenuated lung, and multi-segmental atelectasis was identified as a reliable set of imaging findings for the diagnosis of anthracosis

Influence of Root Canal Taper on Its Cleanliness: A Scanning Electron Microscopic Study

Abstract Introduction: Taper is a factor that determines final root canal dimensions and, consequently, the dimensions of the space for the cleaning action of irrigants. Therefore, the aim of the present study was to investigate the influence of taper on root canal cleanliness. Methods: Root canals of 45 mandibular incisors were divided into 3 groups and prepared with GT rotary files to apical preparation size 30 and final taper 0.04, 0.06, and 0.08, respectively. Irrigation with 2.5% NaOCl was performed after each file. The final irrigation sequence was 10 mL 17% ethylenediaminetetraacetic acid, followed by 10 mL 2.5% NaOCl and 10 mL saline solution. The presence of debris and smear layer on root canal walls was evaluated under the scanning electron microscope with the use of a 4-category scale system. Results: The presence of debris was minimal in all groups. Statistical analysis for the presence of smear layer showed no significant differences between the groups, whereas a significant difference was detected between the apical and middle thirds of each group. Conclusions: Under the conditions of this study, root canal preparation with tapers 0.04, 0.06, or 0.08 did not affect canal cleanliness. Debris removal was almost complete for all tapers, whereas smear layer was not removed, especially from the apical part of the canals. (J Endod 2011;37:871-874

Central African Hunters Exposed to Simian Immunodeficiency Virus

HIV-seronegative Cameroonians with exposure to nonhuman primates were tested for simian immunodeficiency virus (SIV) infection. Seroreactivity was correlated with exposure risk (p<0.001). One person had strong humoral and weak cellular immune reactivity to SIVcol peptides. Humans are exposed to and possibly infected with SIV, which has major public health implications