A great deal of research has been conducted on the performance of granular columns under vertical loads. However, in some situations, the movement of the soil mass can lead to lateral deformations and, as a result, shear stresses in the soil and columns. The primary objective of the present study is to numerically investigate the shear performance of soft clay soil improved with a single Ordinary granular column (OGC) in the direct shear test using a hybrid Discrete Element-Finite Difference Method (DEM-FDM). The numerical modeling method was first validated by simulating a direct shear test conducted previously on a soft clay-OGC composite in the laboratory. Afterward, an extensive parametric study was conducted to determine how various factors affect the shear strength of clay-OGC composites. According to the results, increasing the area replacement ratio from 15 to 35% can increase the peak shear strength of clay-OGC composites in the direct shear test by up to two times, depending on the level of applied normal stress. The micro-scale results also indicated that the surface roughness of soil particles in OGC has a greater effect on the shear strength of clay-OGC composites than their angularity. Furthermore, the results showed that the equivalent friction angle of clay-OGC composites should be calculated based on the residual friction angle of granular soil used in OGC.

The emerging contaminants are commonly derived from municipal, agricultural, and industrial wastewater sources and pathways. These compounds are polar and poorly biodegradable. The dynamic removal of atenolol from aqueous solutions by activated carbon in fixed bed column systems was investigated. As far as we know, this is the first study reporting the decontamination by adsorption in fixed bed of solutions containing atenolol, as model compound of b-blockers, which are pharmaceutical pollutants with a high occurrence in natural waters. The performance of fixed bed columns was described through the breakthrough curves obtained from column experiments. The Bohart-Adams, Thomas and Yoon-Nelson models were applied to predict different parameters of the column like service time (Bohart-Adams model), adsorption capacity (Thomas model) and time required for 50% breakthrough (Yoon-Nelson model). Also, the theoretical breakthrough adsorption curve has been obtained. For the last, an industrial scale adsorber was designed from characteristic parameters of the breakthrough curves obtained from experimental data.

Shear wave velocity, Vs, is a useful soil mechanical property for determining the low shear strain (γ ≈ 0. 0001%) elastic shear modulus, which is required for both static and dynamic response analyses of earth structures. It is an important geotechnical soil property for the design and analysis of geotechnical structures. It can be employed to determine the maximum or small-strain (≤ 10-3%) dynamic shear modulus (Gmax or G0) of the soil mass. Vs can be easily obtained using laboratory or in situ testing techniques. Laboratory tests can be carried out on undisturbed soil samples by simulating the field stress conditions or reconstituted soil samples from a site. However, obtaining good quality undisturbed samples of granular soil deposits is very difficult and moderately expensive. In most geotechnical investigations, the seismic properties (P-or S-wave velocity and the dynamic elastic properties) of granular soil layers from in situ tests (such as the seismic cone penetration test) cannot be determined because of the high cost of undisturbed specimens and the need for highly specialized personnel and equipment. There is increasing interest in the use of Vs to study soil particle properties (e. g. shape, elastic properties, gradation) and the soil state and fabric (e. g. void ratio, boundary stress). In the current study, the bender element and resonant column tests were conducted on sand-gravel specimens. A bender element is an electro-mechanical transducer composed of two-layers of piezoceramic plates that are cross-sectionally polarized. This allows for straightforward wave velocity measurement of soil specimens. The BE converts electrical energy to mechanical energy (movement). The resonant column device is commonly used in the laboratory to measure the low-strain properties of soil. This includes the dynamic properties (shear modulus and damping ratio) of soil specimens at strain levels of 10-6 to 5×10-3 conducted according to ASTM standards. In the RC test, Vs can be calculated using the solution of the equation for the linear vibration of a columnmass system. The RC device is the most reliable laboratory method for measurement of Vs. The aim of this research was to explain the effects on Vs of the relative density, mean effective stress, grading characteristics, consolidation stress ratio and initial fabric anisotropy produced during specimen preparation. Five gradations of gravelly and sandy material were used to study the influence of grading characteristics, consolidation stress ratio, depositional method, relative density and mean effective stress on the dynamic properties of granular soil. The pure sand was clean, uniformly-graded fine sand with a mean grain size of 0. 6 and a silt content of less than 1% that was classified as SP according to the unified soil classification system (USCS). The pure gravel was uniformly-graded soil with a maximum particle size of less than 16 mm that was classified as GP according to the USCS. The measured values from the resonant column and bender element tests also were compared. Comparison of Vs-BE and Vs-RC shows that the results obtained by both techniques were in acceptable agreement for all specimens; however, there was a slight difference between the two techniques at low values of Vs in which Vs-BE was consistently lower than the corresponding values of Vs-RC. The results of these tests were employed to develop a generalized relationship for predicting the Vs of granular soil. The Vs model was validated using experimental data from the current study and from previous studies. The results indicate that the proposed model is capable of predicting the Vs of granular soil.

This study has been conducted to investigate the effect of reinforcing on the bearing capacity of circular footing resting on granular soil. For this purpose, a total number of seven large-scale plate load tests were carried out on a circular plate with a diameter of 300 mm. In order to prepare specimens, a portable curtain rain system is used which is calibrated by 60 raining tests. In the current designed and developed experimental system, a new method is used to measure the normal pressure at footing base. In all loading experiments on soil reinforced with geogrid, only one geogrid layer is used and the effect of depth of this layer from footing base is investigated. The results showed that with provision of geogrid, the bearing capacity of circular footing increases up to 1. 56 times of unreinforced mode. In addition, it is shown that by increasing the ratio of u/DF, the slope of load-settlement curve (stiffness) decreases. For values of u/DF>0. 67, the effect of this parameter (dimensionless depth of geogrid) on bearing capacity of the footing is constant, which indicates that the reinforcing mechanism has been changed and the failure occurs at the upper soil mass (above the geogrid). Also, the results showed that with increasing of the distance from center of the footing, the value of normal pressure applied at footing base reduces.

Two of the important issues in the construction of structures located in seismic coastal areas are the study of the potential of liquefaction phenomenon in saturated sandy soils and seismic structure-foundation-soil interaction (SSFSI). Control of structure damage on the liquefiable soil and large deformations of soil due to seismic loading and, also, the other responses such as: the accelerations at top of the structure/foundation and excess pore water pressure related of this phenomenon are very important. The phenomenon of liquefaction happens due to the occurrence of an earthquake and due to the lack of sufficient opportunity for drainage of excess pore water pressure. One of the effective and useful mitigation methods to control of the liquefaction phenomenon is the usage of dense granular column (DGC) in appropriate dimensions and distances on the ground susceptible to liquefaction. The role of the DGC in controlling the liquefaction phenomenon are follow as: firstly, the DGC is made of materials that are more permeable to sandy soils and cause the excess pore water pressure to be dissipate faster, and secondly, DGC increases the stiffness of the system, which proportionally reduces the excess water pore pressure due to the dilative behavior. To reduce the risks of liquefaction, it is necessary to fully understand its consequences. These consequences depend on permanent soil displacements, structural performance, structural characteristics, foundation and structure dimensions, soil conditions of the structure site, type of loading and earthquake intensity. The presence of the structure and impact of SSFSI affects the intensity of liquefaction and static and dynamic stresses in the soil. Most prior studies (e.g., physical, numerical, or analytical models), ignore the existence of the structure or consider the effect of soil-structure interaction (SSI) on the liquefiable soil layer as an equivalent model. Hitherto, the essence and extend of these interactions are not sufficiently understood. These methods can not properly assess the damage caused by liquefaction; Therefore, these methods cannot be used in the design of structures resistant to liquefaction. Therefore, to accurately study the effect of liquefaction, a method and model is needed that can fully consider the soil, foundation, and structure so that it can be used to correctly estimate the amount of subsidence and displacement of the structure. In this study, to evaluate the seismicity and the mitigation effect of DGCs, using OpenSees finite element software, modeling of DGCs and surrounding soils without structure and models with 5, 10 and 15 storey structures were performed. The three-dimensional soil and DGCs modeled in the software are placed under different earthquakes and the effects of structural layers on the lateral displacement, excess pore water pressure, response of acceleration spectrum, drift and shear force of stories are investigated. The liquefiable soil is modelled through the pressure-dependent multi yield surface soil constitutive law (PDMY02) applied in OpenSees. The results of this study are shown the positive effect of DGC on the reduction of lateral displacement components of soil and structure, foundation subsidence and excess water pore pressure. Also, the presence of the structure on the soil and the increase of its floors have increased the mentioned components except for lateral displacement of soil.

In this study, the effect of the unreinforced and geogrid-reinforced granular blankets, end-bearing stone columns and the combination of these techniques on the behaviour of loose sand soil models have been investigated through laboratory and numerical simulations. In the models, a stone column from a large group of them with a triangular pattern was simulated in a unit cell. Since the rupture of the geosynthetic reinforcement within the reinforced granular blanket has never been experimentally investigated, a novel method of installing the geogrid reinforcement was used, allowing it to mobilize and ultimately fail under loading. The optimal thickness of the unreinforced and geogrid-reinforced blanket, the optimum layout of the reinforcement within the blanket and the changes in the stress concentration ratio of the stone column in different modelling conditions have been determined. Another objective of the present study is to discover the relationship between the failure of the geogrid layers and the characteristics of load-carrying capacity and settlement of the model tests.

This paper presents a numerical analysis of granular column collapse phenomenon using a two-dimensional smoothed particle hydrodynamics model and a local constitutive law proposed by Jop et al. This constitutive law, which is based on the viscoplastic behaviour of dense granular material flows, is characterized by an apparent viscosity depending both on the local strain rate and the local pressure. The rheological parameters are directly derived from the experiments. A simple proposed regularization method used in the viscosity relation to reproduce the stopping condition and the free surface of a granular flow where the pressure is disappeared. Pressure oscillation, as the main disadvantage of the weakly compressible SPH method, leads to an inaccurate pressure distribution. In this research, a new algorithm is proposed to remove the nonphysical oscillations by relating the divergence of velocity to the Laplacian of pressure. The simulations based on the proposed SPH algorithm satisfactorily capture the dynamics of gravity-driven granular flows observed in the experiments. The maximum thickness of a granular flowing on a rough inclined plane is obtained based on the local rheology model and compared with the experimental results. The run-out distances and the slopes of the deposits in the simulations showed a good agreement with the values found in the experiments. The results of the simulation proved that the initial column ratio played an important role in spreading the granular mass.

Objective: Toxoplasmosis, caused by an intracellular protozoan parasite, and the Toxoplasma gondii, is widespread throughout the world. In recent years, significant progress has been made in the identification of vaccine candidates which could induce a protective response. GRA7, an excretory 29 kDa Toxoplasma gondii a dense granular antigen released by infected host cells. In tachyzoite-infected cells, p29 accumulates within the parasitophorous vacuole and co-localizes with its delimiting membrane. Materials and Methods: In the present work, first genomic DNA of Toxoplasma gondii was extracted and used for amplifying of GRA7 gene as a template. Then PCR product was extracted from agarose gel and cloned into TOPO vector. The plasmid containing GRA7 gene was extracted from the transformed bacteria (TOP10 strain) and sequenced. Results: Sequence analysis of GRA7 gene cloned into TOPO vector showed only one base difference when composed with the gene bank sequence for RH strain was only one base. Conclusion: The results indicated that this clone is suitable for subcloning in Prokaryotic and Eukaryotic plasmid.

An attempt was made in the present study to evaluate the pre-and post-liquefaction behavior of the soft ground improved by granular columns (with and without a geogrid encasement) by simulating a loose soil mass reinforced with a granular column in a triaxial cell. For this purpose, a series of large-scale monotonic compressive tests and also stress-controlled cyclic triaxial tests followed by drained and undrained monotonic compression tests were carried out on the loose sand specimens including the granular column with and without geogrid encasement. The pre-cyclic behavior of specimens showed that the deformation modulus improvement due to the use of a stiffer encasement would be less noticeable in case of clogged granular columns. It was found that during a cyclic loading, the use of geogrid encasement will be effective in reducing cumulative settlements and mitigating the liquefaction potential when its tensile stiffness is large enough. Moreover, the post-cyclic behavior of specimens showed that the use of granular columns (whether encased or non-encased) decreased the dependence of the ground deformation modulus on the CSR changes so that the evaluation of the cyclic-induced ground deformation can be done completely independent of the cyclic loading magnitude. It was also found that the use of an encasement with appropriate stiffness played an important role in minimizing the loss of the strength of the ground stabilized by granular columns after experiencing cyclic loads, especially under large earthquakes and after the occurrence of possible liquefaction.

Earth slopes stabilization is one of the main issues in geotechnical engineering. The use of stone columns is one of the approaches for properly increasing the safety factor of earth slopes of the soil embankments. Furthermore, it is economically efficient and is easy in implementation. The present paper aims at an experimental comparison of the Ordinary Stone column (OSC) and Rigid Stone column (RSC) behaviors in sandy slopes. These tasks were carried out by constructing an embankment sandy slope, and then, saturating it with rain and, finally, loading increment. The experimental results of laboratory modeling have been also verified through the three-dimensional finite difference method. Laboratory modeling and numerical analyses results showed that the existence of rigid stone column in the middle of the slope (as the optimal placement location) enhances the sandy slope stability up to 1. 36 times compared with a slope reinforced by Ordinary stone columns.