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3D finite elements analysis of vertically loaded composite piled raft

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Journal of Central South University 2013年第6期20卷 1713-1723页

作者： Reza Ziaie Moayed ehsan Izadi Mehrad Mirsepahi Civil Engineering Department Imam Khomeini International University Department of Geotechnical Engineering Science and Research Branch Islamic Azad University

In recent years,a new type of foundation named composite piled raft foundation (also called long short composite piled raft) has been *** designing shallow foundations would mean unacceptable settlement,or other environmental risks exist which could impair the structure in the future,composite piled raft foundations could be *** element method was applied to study the behavior of this type of foundation subjected to vertical *** order to determine an optimal pile arrangement pattern which yields the minimum settlement,various pile arrangements under different vertical stress levels were *** show that with increasing the vertical stress on the raft,the effectiveness of the arrangements of short and long piles become more *** addition,a new factor named "composite piled raft efficiency" (CPRE) has been defined which determines the efficiency of long short piles arrangement in a composite piled raft *** factor will increase when short piles take more axial stresses and long piles take less axial *** addition,it is found that the changes in settlements for different long short piles arrangement are in a well agreement with changes in values of CPRE ***,CPRE ratio can be used as a factor to determine the efficiency of piles arrangements in composite piled raft foundation from the view point of reducing raft settlements.

关键词： composite piled raft settlement composite piled raft efficiency long-short pile arrangement cushion

Case study of a driven pile foundation in diatomaceous soil.I:Site characterization and engineering properties

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Journal of Rock Mechanics and Geotechnical Engineering 2021年第2期13卷 431-445页

作者： Jiayao Wang ehsan Yazdani T.Matthew Evans School of Civil and Construction Engineering Oregon State UniversityCorvallisOR97331USA

Diatomaceous soils are comprised of the silica frustules of diatom microalgae that are present in marine and lacustrine environments throughout the *** to their unique origin,diatomaceous soils are typically characterized by high intraparticle porosity,complex particle shapes,and uniform mineralogy,causing them to exhibit atypical physical and engineering behaviors.A substantial deposit of diatomaceous silt was observed during site exploration for construction of the Buck Creek Bridge on OR140 near Klamath Falls,OR,USA.A comprehensive laboratory and in situ testing program indicated that the diatomaceous soil possessed“non-textbook”engineering ***,tested samples had high liquid limits(≈100%-140%)with natural water contents at or near the liquid ***,the soil is expected to be normally consolidated,yet high apparent overconsolidation ratios(OCR)(≈15-40)were observed both in oedometric consolidation tests and through cone penetration test(CPT)*** penetration test(SPT)results show a corrected standard penetration resistance consistent with a medium-dense sand(i.e.(N1)_(60)≈25).CPT results include corrected tip resistances(qt)of approximately 7-10 MPa and excess pore pressures(u_(2))of up to 4 *** CPT dissipation tests,pore water pressures(PWPs)returned to hydrostatic pressure in less than 1 *** this work,we synthesize these seemingly disparate material properties in an attempt to infer appropriate engineering properties for the diatomaceous deposit at the Buck Creek Bridge and attempt to provide insight into the underlying reasons for the observed behavior.

关键词： Diatomaceous soil Problematic soil Site characterization Laboratory testing

Field investigation on friction factor in mountainous cobble-bed and boulder-bed rivers

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International Journal of Sediment Research 2011年第2期26卷 210-221页

作者： Hossein AFZALIMEHR Jacques GALLICHAND ehsan BAGHERI Department of Water Engineering Isfahan University of Technology Departement des sols et de genie agroalimentaire Universite Laval Water Engineering Department Isfahan University of Technology

This paper presents results of the friction factor of cobble-bed and boulder-bed rivers based on 23 field measurements in three mountainous rivers in *** reveal that features of our measured velocity profiles in boulder-bed rivers in mountainous region do not present a specific shape but illustrate specific pattern in cobble-bed *** difference is attributed to scale effect of relative submergence. It is found that the relative submergence in cobble and boulders-bed rivers is the only key parameter that influences friction factor estimation and other parameters such as particle Froude number and Froude number have few impacts on flow resistance of cobble-bed and boulder-bed *** proposed relationship for estimation for the friction factor should be useful for large coarse-bed rivers.

关键词： Boulder-bed Cobble-bed Friction factor Mountainous river Relative submergence

Load eccentricity effects on behavior of circular footings reinforced with geogrid sheets

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Journal of Rock Mechanics and Geotechnical Engineering 2015年第6期7卷 691-699页

作者： ehsan Badakhshan Ali Noorzad Faculty of Civil Water & Environmental EngineeringShahid Beheshti University

In this paper, an experimental study for an eccentrically loaded circular footing, resting on a geogridreinforced sand bed, is performed. To achieve this aim, the steel model footing of 120 mm in diameterand sand in relative density of 60% are used. Also, the effects of depth of first and second geogrid layersand number of reinforcement layers （1e4） on the settlement-load response and tilt of footing undervarious load eccentricities （0 cm, 0.75 cm, 1.5 cm, 2.25 cm and 3 cm） are investigated. Test results indicatethat ultimate bearing capacity increases in comparison with unreinforced condition. It is observed thatwhen the reinforcements are placed in the optimum embedment depth （u/D ？0.42 and h/D ？0.42）, thebearing capacity ratio （BCR） increases with increasing load eccentricity to the core boundary of footing,and that with further increase of load eccentricity, the BCR decreases. Besides, the tilt of footing increaseslinearly with increasing settlement. Finally, by reinforcing the sand bed, the tilt of footing decreases at 2layers of reinforcement and then increases by increasing the number of reinforcement layers.

关键词： Model test Circular footing Eccentric load Reinforced sand Bearing capacity

Hydrodynamic Assessment of A New Nature-Based Armour Unit on Rubble Mound Breakwater for Coastal Protection

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China Ocean Engineering 2024年第3期38卷 439-452页

作者： ehsan SAFA Alireza MOJTAHEDI Abdolmajid MOHAMMADIAN Mohamad Ali Lotfollahi YAGHIN Department of Water Resources Engineering Faculty of Civil EngineeringUniversity of TabrizTabriz ***Iran Faculty of Civil Engineering University of OttawaOttawa K1H 8M5Canada

This research proposes a novel nature-based design of a new concrete armour unit for the cover layer of a rubblemoundbreakwater. Armour units are versatile with respect to shape, orientation, surface condition details, and ***, a detailed analysis is required to investigate the exact state of their hydraulic interactions and structuralresponses. In this regard, the performance results of several traditional armour units, including the Antifer cube,Tetrapod, X-block and natural stone, are considered for the first step of this study. Then, the related observed resultsare compared with those obtained for a newly designed (artificial coral) armour unit. The research methodology utilizesthe common wave flume test procedure. Furthermore, several verified numerical models in OpenFOAM code areused to gain the extra required data. The proposed armour is configured to provide an effective shore protection as anenvironmental-friendly coastal structure. Thus it is designed with a main trunk including deep grooves to imitate thetypical geometry of a coral type configuration, so as to attain desirable performance. The observed results and ananalytic hierarchy process (AHP) concept are used to compare the hydraulic performance of the studied traditionaland newly proposed (artificial coral) armour units. The results indicate that the artificial coral armour unit demonstratesacceptable performance. The widely used traditional armour units might be replaced by newer designs for betterwave energy dissipation, and more importantly, for fewer adverse effects on the marine environment.

关键词： rubble mound breakwater hydraulic interaction armour unit analytic hierarchy process numerical model

Natural coupled orbit-attitude periodic motions in the perturbed-CRTBP including radiated primary and oblate secondary

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Astrodynamics 2023年第2期7卷 229-249页

作者： Majid Bakhtiari ehsan Abbasali Siavash Sabzy Amirreza Kosari School of Advanced Technologies Iran University of Science and TechnologyNarmakTehran 16844Iran Aerospace Group Faculty of New Sciences and TechnologiesUniversity of TehranNorth Kargar StreetTehranIran

This study investigated periodic coupled orbit-attitude motions within the perturbed circular restricted three-body problem(P-CRTBP)concerning the perturbations of a radiated massive primary and an oblate *** radiated massive primary was the Sun,and each planet in the solar system could be considered an oblate *** the problem has no closed-form solution,numerical methods were ***,the general response of the problem could be non-periodic or periodic,which is significantly depended on the initial conditions of the orbit-attitude ***,the simultaneous orbit and attitude initial states correction(SOAISC)algorithm was introduced to achieve precise initial *** the other side,the conventional initial guess vector was essential as the input of the correction algorithm and increased the probability of reaching more precise initial ***,a new practical approach was developed in the form of an orbital correction algorithm to obtain the initial conditions for the periodic orbit of the *** new proposed algorithm may be distinguished from previously presented orbital correction algorithms by its ability to propagate the P-CRTBP family orbits around the Lagrangian points using only one of the periodic orbits of the unperturbed CRTBP(U-CRTBP).In addition,the Poincarémap and Floquet theory search methods were used to recognize the various initial guesses for attitude *** of these search methods was able to identify different initial guesses for attitude ***,as a new innovation,these search methods were applied as a powerful tool to select the appropriate inertia ratio for a satellite to deliver periodic responses from the coupled *** the mentioned perturbations to the U-CRTBP could lead to the more accurate modeling of the examination environment and a better understanding of a spacecraft's natural motion.A comparison between the orbit-attitude natural motions in the

关键词： oblate and radiated primary perturbed periodic orbit-attitudebehavior periodic orbit three-body problem Lagrangian points

Scenario-based Planning of Active Distribution Systems Under Uncertainties of Renewable Generation and Electricity Demand

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CSEE Journal of Power and Energy Systems 2019年第1期5卷 56-62页

作者： Ali ehsan Ming Cheng Qiang Yang College of Electrical Engineering Zhejiang UniversityChina Department of Electrical and Computer Engineering COMSATS University IslamabadSahiwal CampusPakistan

The rising penetration of intermittent renewable distributed generation leads to uncertainties in the planning of electric distribution *** considering the uncertainties pertinent to wind power generation,photovoltaic power generation and load demand,this paper proposes a scenariobased model for the planning of active distribution *** solution obtains the optimal capacities and locations of wind and photovoltaic based distributed generators in the distribution system,whilst minimizing the active and reactive power losses as well as voltage deviation.A scenario matrix is generated using the heuristic moment matching technique that captures the stochastic moments and correlation among historical wind and photovoltaic power,and electricity *** scenario matrix is then incorporated to propose a stochastic planning model that considers a multi-objective index for minimizing power losses and voltage ***,the effectiveness of the proposed planning model is confirmed using case-studies in 53-bus and IEEE 123-bus distribution systems.

关键词： Distributed generation heuristic moment matching power losses planning renewable uncertainties

Development of minimum tie line length method for determination of minimum miscible pressure in gas injection process

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Petroleum Research 2019年第2期4卷 173-180页

作者： ehsan Zareie shirazani Taraneh Jafari Behbahani Research Institute of Petroleum Industry(RIPI) TehranIran Islamic Azad University Central Tehran BranchTehranIran

Gas injection process is a very important technology in enhanced oil *** miscible pressure is one of the key parameters in gas injection *** experimental methods such as slim tube are used to measure *** methods are costly and time *** computational methods are used in order to achieve a cost-effective and reliable technique to evaluate *** this work,a new methodology has been proposed for determination of MMP using the minimum tie line length method.A real mixing cell model was developed to estimate the MMP,MME and key tie *** method is simple,robust,and faster than conventional one-dimensional simulation of slim *** new mixing cells method can accurately determine the whole key tie lines to a shift,regardless of the number of injection gas and reservoir fluid *** other methods of mixing cells,this method automatically corrects dispersion by additional contacts to achieve the low variation domain of tie line ***,the determination and implementation of the minimum miscibility enrichment are investigated.

关键词： Minimum miscible pressure Minimum miscibility enrichment Multiple mixing cells method Enhanced oil recovery Minimum tie line length method

The impact of salinity,alkalinity and nanoparticle concentration on zeta-potential of sand minerals and their implication on sand production

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Energy Geoscience 2022年第3期3卷 314-322页

作者： Abbass Kataya ehsan Khamehchi Masoud Bijani Department of Petroleum Engineering Amirkabir University of Technology(Tehran Polytechnic)TehranIran

The effect of brine salinity,cation type,pH,and produced sand on zeta potential(ZP)measurements with and without the presence of silica nanoparticles is investigated through pH measurement,static tests for sand and ZP measurements as well as Field Emission Scanning Electron Microscope(FESEM)*** important factors were investigated:composition of the injected brine,surface charge and *** influence on stability of nanoparticles in the injected brine and amount of sand segregation was determined and the analysis of the new outcomes based on rock/brine ZP measurements was *** results show that the use of silica nanoparticles with high pH helps in preventing sand production and that pH has a main effect on the surface charge of the sand particle released,affecting the ZP of the *** can be active as a coating on sand grains and prevent sand segregation during water *** cations have been found to acquire a more substantial impact on neutralizing the negative charge of the sand particles than monovalent cations at the same concentration and pH conditions at 25℃.The value of ZP becomes of higher negative value with the decrease of brine *** effectiveness of SiO_(2)nanoparticles is quite different for soft water and smart *** soft water,the nanoparticles work more effective at pH higher than 8;and for smart water,the nanoparticles perform better at pH lower than *** reduce sand production with the use of silica nanoparticles,it is highly suggested to increase pH,as pH and sand production mechanisms were observed to be inversely related.

关键词： Sand production Zeta potential Silica nanoparticle Smart water Soft water pH effect