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Slope stability of an unsaturated embankment with and without natural pore water salinity subjected to rainfall infiltration

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岩土力学 2022年第8期43卷 2136-2148页

作者： sadeghi hamed KOLAHDOOZ Ali AHMADI Mohammad-Mehdi Department of Civil Engineering Sharif University of TechnologyTehran ***Iran

Natural soils contain a certain amount of salt in the form of dissolved ions or electrically charged atoms,originated from the long-term erosion by acidic *** dissolved salt poses an extra osmotic water potential being normally neglected in laboratory measurements and numerical ***,ignorance of salinity may result in overestimation of stability,and the design may not be as conservative as ***,this research aims to first experimentally examine the influence of pore water salinity on water retention curve and saturated permeability of natural dispersive loess under saline and desalinated ***,the measured parameters are used for stability analyses of a railway embankment in an area subjected to regional rainfall ***,a numerical parametric study is carried out to explore the significance of different rainfall schemes,construction patterns,and anisotropic permeability on the factor of *** reveal that desalinization suppresses the water retention capability,which in turn results in a tremendous declination of unsaturated hydraulic *** the natural saline embankment,rainfall can hardly infiltrate into the desalinated embankment due to the lower ***,the factor of safety for natural saline conditions drops notably,while only marginal changes occur in the case of the desalinated embankment.

关键词： slope stability water salinity osmotic potential dispersive loess rainfall patterns

Effects of solar radiation and fine roots on suction of Amorpha fruticose-vegetated soil

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Journal of Mountain Science 2023年第6期20卷 1790-1804页

作者： GUO Han-qing CHEN Xiao-qing SONG Dong-ri MU Qing-yi sadeghi hamed JIANG Hao LV Ming Laboratory of Mountain Hazards and Earth Surface Process/Institute of Mountain Hazards and Environment Chinese Academy of SciencesChengdu 610299China University of Chinese Academy of Sciences Beijing 100049China Department of Civil Engineering Xi'an Jiaotong UniversityXi'an 710049China Department of Civil Engineering Sharif University of TechnologyTehran ***Iran

The thickness of shallow landslides is generally less than 2 m,which is of the same order of magnitude as the growth range of vegetation *** roots can improve the stability of shallow soil through mechanical and hydraulic ***,the landslide process is closely related to the plant roots growing on the slope *** roots play a dominant role in the regulation of soil suction through solar radiation induced ***,little is known about the correlation between cumulative solar radiation and soil ***,the specific effects of fine roots on the suction distribution are not clear in most previous *** this study,a vegetated soil of a drought-tolerant and water-tolerant shrub,namely Amorpha fruticose,was *** suction and volumetric water content of bare and vegetated soils were monitored under natural conditions for 4 *** results demonstrate that there is a nearly linear relationship between cumulative solar radiation and suction ranging from zero to 100 *** the modeling of the soil-plant-atmosphere interactions,this relationship could serve a significant role in calculating the root water uptake under given solar radiation *** addition,higher suctions were observed at the lower layer of the vegetated soil than those at the middle layer,which is different from the results of vegetated soil from previous *** is due to the fact that the root area index(RAI)of fine roots at the lower layer is twice that of the middle ***,the higher concentration of fine roots at the lower layer of vegetated soil sample resembles the root distribution of shrub near the soil-bedrock interface on shallow bedrock *** fine roots would increase soil suction through transpiration,and hence reduce the permeability and increase shear strength of ***,these new findings serve as a preliminary step on the evaluation of the stability of this common ty

关键词： Field monitoring Fine roots Solar radiation Suction Shallow bedrock landslide

Evaluation of plant growth and spacing effects on bioengineered slopes subjected to rainfall

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Biogeotechnics

Biogeotechnics 2024年第2期2卷 19-27页

作者： Farshad Yazdani hamed sadeghi Pouya AliPanahi Mostafa Gholami Anthony Kwan Leung Department of Civil Engineering Sharif University of TechnologyAzadi Ave.TehranIran Department of Civil and Environmental Engineering The Hong Kong University of Science and TechnologyHong KongChina

Shallow landslides can be mitigated through the hydro-mechanical reinforcement provided by vegetation. Several critical parameters, such as plant spacing and plant age, play a significant role in influencing bioengineered slope stability facilitated by vegetation. However, the coupling of these effects on the stability of vegetated slope has been ignored. The objective of this study is to investigate the hydro-mechanical impact of vegetation growth and spacing on the stability of bioengineered slopes based on the predictions of a calibrated numerical model against field measurements. The impact of vegetation is investigated, with specific attention given to different plant spacing and growth stages, utilizing Schefflera arboricola. In the context of rainfall, it was observed that younger vegetation demonstrated more effective matric suction retention and recovery up to 25 kPa compared to the aged vegetation. Vegetation was revealed to substantially enhance the factor of safety up to 0.3 compared to the bare slope. Plant growth and reducing plant spacing increased the impact of root systems on both hydraulic and mechanical stability, primarily attributable to the influence of root cohesion rather than transpiration rates. The results revealed that the mechanical contribution to the factor of safety enhancement was raised from one-third to two-thirds because of the vegetation-induced cohesion within the growing rooted zone.

关键词： Bioengineered slopes Shallow landslide Plant age Plant spacing Slope stability

Local seismic culture in Iranian vernacular architecture: evidence from Yazd earthen architecture

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Built Heritage 2022年第2期6卷 1-23页

作者： hamed Azizi‑Bondarabadi Neda Haji sadeghi Department of Civil Engineering Yazd UniversityYazdIran Department of Art and Architecture Yazd UniversityYazdIran

Iran,located in one of the most earthquake-prone regions of the world,has experienced a very large number of destructive earthquakes that brought about considerable loss of human life and economic *** coun‑try possesses a vast number of monumental and vernacular built heritages that are constantly threatened by earth‑*** vernacular techniques for dwellings comply with the needs,comfort,utility,and functionality of people,it is expected that endemic earthquake-resistant techniques make an essential contribution to Iranian vernacular archi‑*** city of Yazd presents a unique and rich vernacular for earthen construction within Iranian architectural heritage,which has resulted in the recognition of the historic fabric of the city as a World Heritage Site since *** the importance of exploring diferent local seismic cultures worldwide,this paper introduces an essential part of Iranian local seismic culture by recognising and classifying the vernacular earthquake-resistant techniques used in the earthen architecture of the city of *** techniques were collected by surveying the historic fabric,using data available in the literature,and interviewing traditional builders and local ***,the seismic infuence of each technique was evaluated using examples from the performance of adobe constructions during the 2003 Bam earthquake.

关键词： Local seismic culture Vernacular earthen architecture adobe Yazd Iran

Flow and natural convection heat transfer characteristics of non-Newtonian nanofluid flow bounded by two infinite vertical flat plates in presence of magnetic field and thermal radiation using Galerkin method

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Journal of Central South University 2019年第5期26卷 1294-1305页

作者： Peyman MAGHSOUDI Gholamreza SHAHRIARI hamed RASAM Sadegh sadeghi School of Engineering University of TehranTehran ***Iran School of Engineering Iran University of Science and TechnologyTehran ***Iran

The main goal of this paper is to investigate natural convective heat transfer and flow characteristics of non-Newtonian nanofluid streaming between two infinite vertical flat plates in the presence of magnetic field and thermal ***,a similarity transformation is used to convert momentum and energy conservation equations in partial differential forms into non-linear ordinary differential equations (ODE) applying meaningful boundary *** order to obtain the non-linear ODEs analytically,Galerkin method (GM) is ***,the ODEs are also solved by a reliable numerical *** order to test the accuracy,precision and reliability of the analytical method,results of the analytical analysis are compared with the numerical *** respect to the comparisons,fairly good compatibilities with insignificant errors are ***,the impacts of effective parameters including magnetic and radiation parameters and nanofluid volume fraction on the velocity,skin friction coefficient and Nusselt number distributions are comprehensively *** on the results,it is revealed that with increasing the role of magnetic force,velocity profile,skin friction coefficient and thermal performance *** parameter has insignificant influence on velocity profile while it obviously has augmentative and decreasing effects on skin friction and Nusselt number,respectively.

关键词： non-Newtonian flow nanofluid flow Galerkin method magnetic field radiation

Surface metal-matrix composites based on AZ91 magnesium alloy via friction stir processing:A review

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International Journal of Minerals,Metallurgy and Materials 2023年第7期30卷 1278-1296页

作者： hamed Mirzadeh School of Metallurgy and Materials Engineering College of EngineeringUniversity of TehranTehranIran

This monograph presents an overview of friction stir processing(FSP)of surface metal-matrix composites(MMCs)using the AZ91 magnesium *** reported results in relation to various reinforcing particles,including silicon carbide(SiC),alumina(Al_(2)O_(3)),quartz(SiO_(2)),boron carbide(B_(4)C),titanium carbide(TiC),carbon fiber,hydroxyapatite(HA),in-situ formed phases,and hybrid reinforcements are ***91 composite fabricating methods based on FSP are explained,including groove filling(grooving),drilled hole filling,sandwich method,stir casting followed by FSP,and formation of in-situ *** effects of introducing second-phase particles and FSP process parameters(e.g.,tool rotation rate,traverse speed,and the number of passes)on the microstructural modification,grain refinement,homogeneity in the distribution of particles,inhibition of grain growth,mechanical properties,strength–ductility trade-off,wear/tribological behavior,and corrosion resistance are ***,useful suggestions for future work are proposed,including focusing on the superplasticity and superplastic forming,metal additive manufacturing processes based on friction stir engineering(such as additive friction stir deposition),direct FSP,stationary shoulder FSP,correlation of the dynamic recrystallization(DRX)grain size with the Zener–Hollomon parameter similar to hot deformation studies,process parameters(such as the particle volume fraction and external cooling),and common reinforcing phases such as zirconia(ZrO_(2))and carbon nanotubes(CNTs).

关键词： surface composites magnesium alloys friction stir processing severe plastic deformation thermomechanical processing

Minimum Reservoir Water Level in Hydropower Dams

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Chinese Journal of Mechanical Engineering 2017年第4期30卷 1017-1024页

作者： hamed Sarkardeh Department of Civil Engineering Hakim Sabzevari UniversitySabzevarIran

Vortex formation over the intakes is an unde- sirable phenomenon within the water withdrawal process from a dam reservoir. Calculating the minimum operating water level in power intakes by empirical equations is not a safe way and sometimes contains some errors. Therefore, current method to calculate the critical submergence of a power intake is construction of a scaled physical model in parallel with numerical model. In this research some pro- posed empirical relations for prediction of submergence depth in power intakes were validated with experimental data of different physical and numerical models of power intakes. Results showed that, equations which involved the geometry of intake have better correspondence with the experimental and numerical data.

关键词： Power intake. Vortex Critical submergence Physical and numerical models Empirical equations

Microstructural evolution and mechanical properties of friction stir-welded C71000 copper–nickel alloy and 304 austenitic stainless steel

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International Journal of Minerals,Metallurgy and Materials 2018年第11期25卷 1294-1303页

作者： hamed Jamshidi Aval Department of Materials and Industrial Engineering Babol Noshirvani University of Technology

Dissimilar joints comprised of copper–nickel and steel alloys are a challenge for manufacturers in modern industries, as these metals are not thermomechanically or chemically well matched. The present study investigated the effects of tool rotational speed and linear speed on the microstructure and mechanical properties of friction stir-welded C71000 copper–nickel and 340 stainless steel alloys using a tungsten carbide tool with a cylindrical pin. The results indicated that a rotational-to-linear speed ratio of 12.5 r/mm did not cause any macro defects, whereas some tunneling defects and longitudinal cracks were found at other ratios that were lower and higher. Furthermore, chromium carbide was formed on the grain boundaries of the 304 stainless steel near the shoulder zone and inside the joint zone, directing carbon and chromium penetration toward the grain boundaries. Tensile strength and elongation percentages were 84% and 65% of the corresponding values in the copper–nickel base metal, respectively.

关键词： dissimilar friction stir welding copper–nickel alloy austenitic stainless steel microstructure mechanical properties

Optimal State Estimation and Fault Diagnosis for a Class of Nonlinear Systems

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IEEE/CAA Journal of Automatica Sinica 2020年第2期7卷 517-526页

作者： hamed Kazemi Alireza Yazdizadeh Department of Electrical Engineering Shahid Beheshti UniversityTehran ***Iran

This study proposes a scheme for state estimation and,consequently,fault diagnosis in nonlinear ***,an optimal nonlinear observer is designed for nonlinear systems subject to an actuator or plant *** utilizing Lyapunov's direct method,the observer is proved to be optimal with respect to a performance function,including the magnitude of the observer gain and the convergence *** observer gain is obtained by using approximation of Hamilton-Jacobi-Bellman(HJB)*** approximation is determined via an online trained neural network(NN).Next a class of affine nonlinear systems is considered which is subject to unknown disturbances in addition to fault *** this case,for each fault the original system is transformed to a new form in which the proposed optimal observer can be applied for state estimation and fault detection and isolation(FDI).Simulation results of a singlelink flexible joint robot(SLFJR)electric drive system show the effectiveness of the proposed methodology.

关键词： Differential geometry fault detection and isolation(FDI) fault diagnosis neural network(NN) nonlinear observer and filter design optimal state estimation