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Ashayeri I.,Razi University | Kamalian M.,International Institute of Earthquake Engineering and Seismology | Jafari M.K.,International Institute of Earthquake Engineering and Seismology | Biglari M.,Razi University | Mirmohammad Sadeghi M.,Isfahan Higher Education And Research Institute IHEARI
International Journal of Civil Engineering

This paper presents time domain fundamental solutions for the extended Biot's dynamic formulations of two-dimensional (2D) unsaturated poroelasticity. Unsaturated porous media is considered as a porous media in which the voids are saturated with two immiscible fluids, i.e. liquid and gas. At first, the corresponding explicit Laplace transform domain fundamental solution is obtained in terms of skeleton displacements, as well as liquid and gas pressures. Subsequently, the closed-form time domain fundamental solutions are derived by analytical inversion of the Laplace transform domain solutions. Finally, a set of numerical results are presented which verifies the accuracy of the analytically inversed transient fundamental solution and demonstrates some salient features of the elastic waves in unsaturated media. Source

Mirmohammad Sadeghi M.,Isfahan Higher Education And Research Institute IHEARI | Hassan Beigi F.,Islamic Azad University at Najafabad
Geotextiles and Geomembranes

Experimental investigations and modeling of linear elasticity of fiber-reinforced clayey sand under cyclic loading unloading are conducted in this paper. Experimental studies are focused on four aspects. First, a series of cyclic triaxial tests, with different confining pressures and deviator stress ratios up to 150 cycles, are performed. Impacts of fiber content, cell pressure, deviator stress ratio and loading unloading repetition that affect dynamic behavior of the composite material are discussed. It is shown that shear modulus decreases with increasing deviator stress ratio at high confining pressure and the rate of loss of shear modulus found to be much lower for fiber reinforced specimens. Other results show that increase of shear modulus with loading repetition is more pronounced at higher deviator stress ratios. Second, the optimum fiber content is experimented under cyclic loading unloading and is expressed as a power function of deviatoric stress ratio. It is shown that optimum fiber content is not constant and it is affected by deviator stress ratio. Third, a function is introduced to describe the linear stress-strain curve under cyclic loading unloading using equivalent linear analysis. The shear modulus G is expressed as a function of fiber content, confining pressure, deviatoric stress ratio and loading repetition. Finally constitutive coefficients of the model parameters are calibrated by the results of cyclic triaxial shear tests and using the linear regression. © 2014 Elsevier Ltd. Source

Moradi Z.,University of Isfahan | Jahanshah F.,Isfahan Higher Education And Research Institute IHEARI | Jahanshah F.,University of Isfahan | Fallah H.R.,University of Isfahan | And 3 more authors.
Applied Physics B: Lasers and Optics

We designed and fabricated the transmission quarter-wave plate phase retarder at 1064 nm using optical nanometric thin films of silicon oxide and titanium oxide. Final design consists of 32 layers. Transmissions of polarizations are equal and ≥99 % and their phase difference is 90°. System consists of two 16 layers systems that coated with the same condition on BK7 glass substrates then attached together with optical glue. Electron beam evaporation method was used for depositing materials. Photo spectrometer was used for measuring transmission spectrum of system. Transmission of polarizations was ≥95 % and equal. A polarimeter was used for testing systems. Polarization of beam was circular. © 2016, Springer-Verlag Berlin Heidelberg. Source

Sotoudehfar A.R.,Islamic Azad University at Najafabad | Mirmohammad sadeghi M.,Isfahan Higher Education And Research Institute IHEARI | Mokhtari E.,Islamic Azad University at Najafabad | Shafiei F.,University of Isfahan
Geomicrobiology Journal

Soil improvement is one of the major concerns in civil engineering. Therefore, a variety of approaches have been employed for different soil types. The loose granular soils and sediments have always imposed challenges due to their low strength and bearing capacity as well as presenting difficulties in drilling and excavation. Biomediated soil improvement, i.e., utilizing some bacteria to precipitate calcite on soil particles, has recently been introduced as a novel link of biotechnology and civil engineering to improve the problematic soils. Biogrout as a branch of biomediated soil improvement is based upon microbial calcium carbonate precipitation (MICP). In the present study, the Taguchi method with the aim of optimizing the process was utilized to design the experiments (DOE). A standard L9 orthogonal array with four parameters comprising bacterial cell concentration, molar concentration ratio of nutrient solution, curing time, and flow rate, each assigned to three levels, was selected. In this regard, soil samples were stabilized in sandy soil columns. Two-phase injections were conducted by injecting the bacterium Sporosarcina pasteurii PTCC 1642 in the first phase and nutrient in the second phase. Specimens were subjected to an unconfined compressive strength (UCS) test. ANOVA pointed out how effectual each parameter was. The most effective parameter was curing time, which accounted for 45.97% of the overall variance of the experimental data followed by bacterial cell concentration (22.01%), nutrient strength (19.98%), and flow rate (12.04%). Predicted UCS values for the optimum condition were validated in a confirmation test. Indeed, the UCS of the soil increased from 85 kPa in the control sample to 930 kPa for the optimally treated specimen. It was concluded that rather than curing time, the other parameters are almost equally influential in the applied injection procedure. © 2015 Taylor & Francis Group, LLC. Source

Mirmohammad sadeghi M.,Isfahan Higher Education And Research Institute IHEARI | Modarresnia A.R.,University of Tehran | Shafiei F.,Isfahan Higher Education And Research Institute IHEARI
Geomicrobiology Journal

The effects of experimental parameters including soil type, curing duration, inoculum size, and biomass and nutrients concentration on soil strengthening due to calcite precipitation by Sporosarcina pasteurii PTCC 1645 were investigated. The laboratory-scale mixing experiments on remolded samples were designed by the Taguchi method. Soil type proved to be the most incorporating factor, followed by curing time and nutrient concentration. The main effect and the interactions of the parameters were presented and the optimal conditions were obtained. This suggests the importance of local conditions including soil type on any future large-scale, in situ application. © 2015, Copyright © Taylor & Francis Group, LLC. Source

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