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A critical state based thermo-elasto-plastic constitutive model for structured clays

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第6期9卷 1094-1103页

作者： amir hamidi Saeed Tourchi Fatemeh Kardooni Department of Civil Engineering School of Engineering Kharazmi University Department of Civil and Environmental Engineering Universitat Politècnica de CatalunyaBarcelona Tech

In this paper, a critical state based thermo-elasto-plastic constitutive model is developed for destructured, naturally structured and artificially structured saturated clays. The model is an extension of the previously developed thermo-mechanical model by the authors for saturated clays, considering the effects of structure on the mechanical behaviors of the soil. It is based on change in the position of normal consolidation line(NCL) in a compression plane(e-ln p′) due to the soil’s structure and variation of temperature. The present model is able to simulate the mechanical behavior of structured saturated clays in a triaxial plane at elevated temperatures lower than the boiling point of water. An attempt has been made to use the lowest possible number of parameters compared with that of Came Clay model and to ensure that these new parameters have clear physical interpretations. The sufficiency of the model was verified by the test results on artificially and naturally structured soils using thermal triaxial tests.

关键词： Thermo-mechanical constitutive model Structured clays Cam Clay Normal consolidation line Boom Clay

Thermo-mechanical constitutive modeling of unsaturated clays based on the critical state concepts

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Journal of Rock Mechanics and Geotechnical Engineering 2015年第2期7卷 193-198页

作者： Saeed Tourchi amir hamidi School of Engineering Kharazmi University

A thermo-mechanical constitutive model for unsaturated clays is constructed based on the existingmodel for saturated clays originally proposed by the authors. The saturated clays model was formulatedin the framework of critical state soil mechanics and modified Cam-clay model. The existing model hasbeen generalized to simulate the experimentally observed behavior of unsaturated clays by introducingBishop＇s stress and suction as independent stress parameters and modifying the hardening rule and yieldcriterion to take into account the role of suction. Also, according to previous studies, an increase intemperature causes a reduction in specific volume. A reduction in suction （wetting） for a given confiningstress may induce an irreversible volumetric compression （collapse）. Thus an increase in suction （drying）raises a specific volume i.e. the movement of normal consolidation line （NCL） to higher values of voidratio. However, some experimental data confirm the assumption that this reduction is dependent on thestress level of soil element. A generalized approach considering the effect of stress level on themagnitude of clays thermal dependency in compression plane is proposed in this study. The number ofmodeling parameters is kept to a minimum, and they all have clear physical interpretations, to facilitatethe usefulness of model for practical applications. A step-by-step procedure used for parameter calibrationis also described. The model is finally evaluated using a comprehensive set of experimental datafor the thermo-mechanical behavior of unsaturated soils.2015 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

关键词： Constitutive model Unsaturated clays Plasticity Cam-clay Critical state

Triaxial shear behavior of a cement-treated sand——gravel mixture

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Journal of Rock Mechanics and Geotechnical Engineering 2014年第5期6卷 455-465页

作者： Younes Amini amir hamidi School of Engineering Kharazmi University

A number of parameters,*** content,cement type,relative density,and grain size distribution,can influence the mechanical behaviors of cemented *** the present study,a series of conventional triaxial compression tests were conducted on a cemented poorly graded sandegravel mixture containing 30% gravel and 70% sand in both consolidated drained and undrained *** cement used as the cementing agent was added to the soil at 0%,1%,2%,and 3%(dry weight) of sandegravel *** were prepared at 70% relative density and tested at confining pressures of 50 kPa,100 kPa,and150 *** of the results with other studies on well graded gravely sands indicated more dilation or negative pore pressure in poorly graded *** failure envelopes determined using zero Skempton’s pore pressure coefficient (= 0) criterion were consistent with the drained *** absorption potential was higher in drained condition than undrained condition,suggesting that more energy was required to induce deformation in cemented soil under drained *** absorption increased with increase in cement content under both drained and undrained conditions.

关键词： Cementation Poorly graded soil Sand-gravel mixture Dilation Absorbed energy Failure criterion

Improvement parameters in dynamic compaction adjacent to the slopes

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Journal of Rock Mechanics and Geotechnical Engineering 2015年第2期7卷 233-236页

作者： Elham Ghanbari amir hamidi School of Engineering Kharazmi University

Dynamic compaction is a cost-effective method commonly used for improvement of sandy soils. Anumber of researchers have investigated experimentally and numerically the improvement parametersof soils using dynamic compaction, such as crater depth, improvement depth, and radial improvement,however, these parameters are not studied for improvement adjacent to the slopes or trenches. In thisresearch, four different slopes with different inclinations are modeled numerically using the finiteelement code ABAQUS, and impact loads of dynamic compaction are applied. The static factors of safetyare kept similar for all trenches and determined numerically by application of gravity loads to the slopeusing strength reduction method （SRM）. The analysis focuses on crater depth and improvement regionwhich are compared to the state of flat ground. It can be observed that compacted area adjacent to theslopes is narrower and slightly away from the slope compared to the flat state. Moreover, crater depthincreases with increase in slope inclination.2015 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

关键词： Dynamic compaction Slopes and trenches Crater depth Improvement depth

Experimental study on bearing capacity of shell strip footings near geotextile-reinforced earth slopes

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Journal of Central South University 2021年第8期28卷 2527-2543页

作者： Seyed ALI GHAFFARI Elham SATTARI amir hamidi Gholamhosein TAVAKOLI MEHRJARDI Abtin FARSHI HOMAYOUN ROOZ Department of Civil Engineering School of EngineeringKharazmi UniversityTehranIran

From a financial point of view,urbanization frequently enforces the clients to construct superstructures near the slopes,giving rise to increasing the risk of building *** conducting a series of small-scale plate load tests,this work aims to investigate the effects of installing geotextile reinforcement layers in sandy slope and reducing the apex angle of triangular shell strip *** results show considerable effect of using geotextile-reinforced layers and decreasing the apex angle on the ultimate bearing capacity of shell *** increasing foundation distance from the slope,the adverse effect of the slope is ***,as the distance decreases,the effect of reinforcement and apex angle is *** practical applications,empirical equations are also presented for determining the ultimate bearing capacity of the footings and scale effect as ***,3D numerical simulations are executed and compared with the experimental results.

关键词： slope shell strip footing geotextile-reinforced apex angle ultimate bearing capacity numerical simulation

Modeling Expected Failure Considering Repair Time and Degradation: A Rail System Case Study

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Journal of Transportation Technologies 2024年第2期14卷 236-254页

作者： Maryam hamidi Atefe Sedaghat amir Gharehgozli Ferenc Szidarovszky Department of Industrial and Systems Engineering Lamar University Beaumont TX USA Department of Systems and Operations Management California State University Northridge CA USA Department of Mathematics Corvinus University of Budapest F&#337v&#225mt&#233r 8 Budapest Hungary

The repeated failures of any equipment or systems are modeled as a renewal process. The management needs an assessment of the number of future failures to allocate the resources needed for fast repairs. Based on the idea of expectation by conditioning, special Volterra-type integral equations are derived for general types of repairs, considering the length of repair and reduced degradation of the idle object. In addition to minimal repair and failure replacement, partial repairs are also discussed when the repair results in reduction of the number of future failures or decreases the effective age of the object. Numerical integration-based algorithm and simulation study are performed to solve the resulting integral equation. Since the geometry degradation in different dimensions of a rail track and controlling and maintaining defects are of importance, a numerical example using the rail industry data is conducted. Expected number of failures of different failure type modes in rail track is calculated within a two-year interval. Results show that within a two-year period, anticipated occurrences of cross level failures, surface failures, and DPI failures are 2.4, 3.8, and 5.8, respectively.

关键词： Renewal Theory Expected Number of Failures Partial Repair Minimal Repair

Prevalence of bacterial agents isolated from clinical cases of bovine mastitis in the dry period and the determination of their antibiotic sensitivity in Tabriz,Iran

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Journal of Coastal Life Medicine 2015年第9期 701-703页

作者： Samad Mosaferi Reza Ghabouli Mehrabani Mansoor Khakpoor Nader Ghabouli Mehrabani amir Maleksabet Faezeh hamidi Department of Clinical Sciences Faculty of Veterinary MedicineTabriz BranchIslamic Azad UniversityTabrizIran Faculty of Veterinary Medicine Tabriz BranchIslamic Azad UniversityTabrizIran Department of Pathobiology Tabriz BranchIslamic Azad UniversityTabrizIran Department of Parasitology and Mycology Faculty of MedicineTabriz University of Medical SciencesTabrizIran Department of Biotechnology School of Advanced Medical Sciences and TechnologiesShiraz University of Medical SciencesShirazIran

Objective:To determine the prevalence of mastitis-causing bacteria in the dry period and its antibiotic ***:In this study,852 dry cows were examined.A total of 30 cows with clinical mastitis symptoms were detected and their milk samples were *** order to purify the bacteria,brain heart infusion and blood agar media were applied and single colonies were used for Gram staining,oxidase and catalase testing,cultivating in O-F medium to determine the genus and species of ***,antimicrobial susceptibility was tested by the agar disk diffusion ***:The prevalence of isolated bacteria was 2.46%,in which coagulase positive Staphylococcus,coagulase negative Staphylococcus,Streptococcus dysgalactiae,Streptococcus faecalis,Escherichia coli,Pseudomonas,Bacillus and yeast were(9/99)%,(6/66)%,(13/32)%,(3/33%),(6/66)%,(13/32)%,(9/99)%and(6/66)%,*** tests of antibiotic susceptibility,the most and the least sensitivity were reported to enrofloxacin and ampicillin ***:This study indicated that Streptococcus dysgalactiae is the most commonly isolated bacteria with the greatest sensitivity to enrofloxacin and tetracycline which can be used to treat mastitis in the dry period in Tabriz.

关键词： Bovine mastitis Antibiotic susceptibility Dry period Bacterial agents Tabriz

A Comparative Study of Transvaginal Sonography and Pelvic MRI in Patients with Endometrial Cancer

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Journal of Clinical and Nursing Research 2022年第2期6卷 61-67页

作者： Marjaneh Farazestanian Anahita hamidi Zohreh Yousefi Parvaneh Layegh amir Hosein Jafarian Helena Azimi Elham Abdollahi Department of Obstetrics and Gynecology Faculty of MedicineMashhad University of Medical SciencesMashhadIran Faculty of Medicine Mashhad University of Medical SciencesMashhadIran Department of Radiology Faculty of MedicineMashhad University of Medical SciencesMashhadIran Department of Pathology Faculty of MedicineMashhad University of Medical SciencesMashhadIran

Background:The most prevalent type of gynecological cancer is endometrial *** surgical staging is the most important aspect in the management of endometrial *** evaluation of myometrial invasion and appropriate management could be achieved by transvaginal sonography and pelvic ***:A total of 53 patients with endometrial cancer,who were referred to a gynecology oncology department of an academic hospital in Mashhad University of Medical Sciences from 2018 to 2020,were evaluated in this *** were collected using a questionnaire on endometrial *** the patients underwent preoperative transvaginal sonography and pelvic MRI to evaluate myometrial *** involvement of myometrium thickness and histological findings were compared between two imaging modalities,and SPSS 23.0 was used to analyze the ***:Junctional irregularity was the most prevalent finding on transvaginal *** on transvaginal sonography,myometrial invasion of less than 50%was found in 73%of patients,while invasion of more than 50%was observed in 26.31%.In 57.44%of MRIs,there was less than 50%myometrial invasion,while in 42.55%of MRIs,there was more than 50%myometrial *** both modalities,the most common finding was myometrial invasion of less than 50%.The accuracy,sensitivity,and specificity of transvaginal sonography were 0.47,0.27,and 0.75,respectively,whereas the accuracy,sensitivity,and specificity of MRI were 0.54,0.45,and 0.61,***:MRI can be the modality of choice for evaluating myometrial invasion and optimizing endometrial cancer treatment planning,as well as reducing the complications of non-indicated lymphadenectomy.

关键词： Endometrial cancer Myometrial invasion Pelvic MRI Transvaginal sonography

早期床旁运动干预在心脏手术后患者心脏康复中的应用效果

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中国临床医学 2022年第4期29卷 621-626页

作者： M.Rafi hamidi 陈轶洪弥守玲陆云涛丛硕王文硕 Hosna hamidi 杨晔 M.Salim BAHRAMAND Ali Ateel DAIFOLADI Babrak SAYEDZADA 刘欢魏来王春生复旦大学附属中山医院心血管外科上海心血管病研究所上海200032 世界卫生组织区域卫生组喀布尔1001阿富汗红新月会卫生部喀布尔1001阿富汗喀布尔amir Hajizada医院心血管外科喀布尔1001阿富汗法国母婴研究所心血管外科咯布尔1001阿富汗

目的评估早期床旁运动干预对心脏瓣膜手术后患者康复的影响。方法纳入40例心脏瓣膜疾病患者,其中20例患者[(49.05±3.728)岁]术后第3、4、5天接受床旁运动干预(3 min/d,干预组),其余20例患者[(47.95±3.214)岁]未接受床旁运动干预(对照... 详细信息

目的评估早期床旁运动干预对心脏瓣膜手术后患者康复的影响。方法纳入40例心脏瓣膜疾病患者,其中20例患者[(49.05±3.728)岁]术后第3、4、5天接受床旁运动干预(3 min/d,干预组),其余20例患者[(47.95±3.214)岁]未接受床旁运动干预(对照组)。术前进行心理教育,并通过标准化问卷简表对患者单独评估。通过指脉氧仪及6 min步行距离来评估心脏康复效果。结果干预组心脏瓣膜患者术后3 d的SpO_(2)水平高于对照组(P<0.05)。干预组术后5 d心率降至基线水平,低于对照组(P<0.05)。结论初级床旁运动(3 min/d)可以提高SpO_(2)、降低心率,进而改善患者基线状态,促进患者康复。

关键词：心脏康复成人心脏手术 6分钟步行测试床旁干预