Narrow Results

Proper modeling of the dynamic behavior of the soil significantly affects the accuracy of the soil–structure interaction analysis results. Using nonlinear constitutive models has the highest accuracy in modeling soil behavior under earthquake loading. However, it is not functional for practical engineering purposes because of the high cost and complexity. The equivalent linear method also has many limitations, such as filtering out the high-frequency components of the input excitation, underestimating surface ground motion over long periods, and considerable error in high soil strain levels. The current study aims to present an accurate, simple, and low-cost method to model the nonlinear behavior of clays. This method does not meet the limitations of the traditional methods and fully considers the effect of the influential parameters. The novel central composite design technique was adopted to evaluate the effect of influential variables on the nonlinear behavior of clay and formulate the proposed method. The introduced method is applicable to various building structures, power planets, etc. Numerical analyses performed on the proposed method and nonlinear modeling confirm the accuracy, efficiency, and generality of the proposed method.

Several samples of pottery sherds owned by the Islamic Arts section of the National museum of Iran excavated in Ray, Neishabur and Kahn – the area around northeast and the central part of Iran – were analyzed in order to establish their chemical compositions. In Van de Graaff Laboratory at the AEOI, qualitative analyses of the sherds were performed using a 2 MeV proton beam. The fragments which dated back to the period between the 9^th and the 13^th centuries, were analyzed using the PIXE method. The results of the concentrations of the component elements such as Ti, Mn, Fe, Co, Ni, Cu, Zn, Ba and Pb are presented and discussed. The results confirm the effect of the iron content of clay, it's firing conditions such as firing temperature, oxidation and reduction on the color of clay. In addition the dependence of glaze color with the various elemental concentration is established.

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in 2011 caused the widespread contamination of Fukushima Prefecture by radioactive cesium. The cesium radioisotopes are considered to have remained in the soil for seven years. We investigated this situation by analyzing soil from paddy fields in the area. We investigated the structure of soil particles using scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDS) and autoradiogram (ARG). We estimated the percentage of clay in the soil based on its composition, and then obtained the radioactivity of the cesium radioisotopes for each soil particle size as a function of penetration. The cesium radioisotopes were exponentially distributed in soil containing a large proportion of clay. Hence, we confirmed that the quantity of clay in the soil is a very important factor with respect to the possibility of the resumption of agriculture in the restricted area.

Particle induced x-ray emission (PIXE) measurements were applied to analyze constituent elements in ancient earthenware (middle Jomon period) excavated at Teramae site in Fukushima prefecture. Quantitative analyses of the earthenware and clay obtained near the site show difference in contents of the constituent elements between them.

Exfoliated silicate minerals have attracted great attentions because of the dramatic improvement in properties. This paper highlights the preparation of exfoliated silicate minerals, including physical, chemical, mixed physical and chemical methods. The mechanisms by which silicates are exfoliated and the important influential factors are also summarized. Finally, the instrumental techniques to characterize the exfoliated structure and exfoliation degree are presented.

The rapid growth in the usage of polymers/polymer composites demands innovative welding techniques for joining. In this research work, Polypropylene (PPE) is chosen as the thermoplastic matrix and the filler selected is Spheri Glass 3000 (SGE) at 2.5wt.%. In this work, Friction Vibration Joining (FVJ) is used for joining PPE/SGE composites. The FVJ experiments were carried out according to Taguchi ${\text{L}}_{27}$ orthogonal array with input parameters as (i) Tool Profile (TP), (ii) Frequency of Vibrating Tool (FVT) and (iii) Feed Rate of Workpiece (FRW). The joints were analyzed mechanically (tensile strength, impact strength and shore D hardness) and metallurgically (scanning electron microscope). Analysis of Variance (ANOVA) is used for studying the significance of the input factors over output factors. The mechanical characteristics of FVJ joints were optimized by Technique for Order Preference by Similarity to Ideal Solution (TOPSIS).

We have prepared hybrid Langmuir–Blodgett (LB) films consisting of a clay single layer and a non-amphiphilic polar molecule, 2,5-bis(p-dimethylaminocinnamylidene)-cyclopentanone. LB films deposited on solid substrates were characterized by means of UV-vis absorption spectroscopy and optical second-harmonic generation (SHG) measurements.

A novel nanocomposites of modified clay in a glassy epoxy were prepared using a direct melt intercalation technique. The contents of oganoclay were varied with 0, 1, 2, and 3 wt% and N-benzylpyrazinium hexafluoroantimonate (BPH) was used for curing of epoxy matrix as a cationic latent catalyst. Dynamic mechanical analysis (DMA) measurement was performed to examine the glass transition temperature of the nanocomposites. As a result, X-ray diffraction indicated the intercalation of the epoxy chains happening inside the gallery of clay. The nanocomposites showed a higher glass transition temperature and storage modulus than those of the pristine epoxy. The mechanical interfacial properties of the nanocomposites were also investigated and the improvement in tearing energy of 160% over pristine epoxy was obtained.

Poly(butyl acrylate-co-methyl methacrylate)/clay nanocomposites were synthesized via emulsion polymerization with an emulsifier (sodium dodecyl benzene sulfonate, SDBS), an initiator (ammonium persulate, APS), acrylic acid ester monomer and Na-montmorillonite. It was found that the addition of SDBS and water widened the gap between clay layers and facilitated monomers to penetrate into clay. Through initiator, comonomers were polymerized in the montmorillonite galleries. The structure of extracted nanocomposites was confirmed by XRD, transmission electron microscopy (TEM). Their thermal property and molecule weight were investigated by differential scanning calorimetry (DSC) and gel-penetrate chromatogram (GPC).

Numerical implementation of an anisotropic constitutive model for clays (SANICLAY) is presented. Moreover, a case study in which a soil embankment is placed on a K₀-consolidated over-consolidated clay is analyzed by conducting an elastoplastic fully-coupled finite element analysis. It is shown that anisotropy has significant impact on the ground settlement caused by the placement of soil embankment and on the pore pressure generation and dissipation within the foundation soil. The simulations using SANICLAY favorably compare with the field measurements of ground settlement and pore pressure. The drawbacks of the use of an isotropic elastoplastic model (Cam Clay) are also demonstrated.

The pH-sensitive P(AA-co-NVP)/clay hydrogels were prepared with the monomers of acrylic acid (AA) and N-vinyl-2-pyrrolidone (NVP) based on γ -ray irradiation technique. The influence of pH values of buffer solutions and contents of clay and NVP on the equilibrium swelling ratio (SR) and compressive properties of the hydrogels was investigated in detail. The results of swelling property tests showed that, with the increase of clay content, the SR of hydrogels increases in the same buffer solution, and the SR of hydrogels with different contents of HTMAB-clay is higher than that of P(AA-co-NVP) hydrogels without clay. When the content of clay is 15%, the SR of P(AA-co-NVP)/clay hydrogel is 201 at pH = 9.8, which is 1.23 times of that of the P(AA-co-NVP) hydrogel (164). In addition, the SR of P(AA-co-NVP)/clay hydrogel is higher than that of PAA/clay hydrogel in the same solution. The compressive properties of the hydrogel were also examined. The results showed that the compressive properties of the P(AA-co-NVP)/clay hydrogels were improved distinctly as compared to those of the conventional hydrogels without clay. When the content of clay is 15%, the compression strength of the P(AA-co-NVP)/clay hydrogel is 23 times of that of the P(AA-co-NVP) hydrogel.

Glycolic acid was polymerized under vacuum in the presence and absence of nano sized clay. The added clay catalyzed the condensation polymerization which can be confirmed by recording FTIR spectroscopy and intrinsic viscosity (IV) values. The relative intensity of C=O/CH is increased while increasing the amount of clay. DSC showed the appearance of multiple endotherms of poly(glycolic acid). TGA showed the percentage weight residue remain above 750°C for polymer-nano composite system was 21% and hence proved the flame retardancy (char forming) nature. TEM confirmed the nano size of the clay used to catalyze the condensation reaction. The intrinsic viscosity value was increased with the increase of percentage weight of Hectorite type clay.

The typical immiscible PP/PS blend based clay nanocomposites were prepared via melt blending. The dispersion of clay was determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal stability and dynamic mechanical properties were measured by thermogravimetrical analysis (TGA) and dynamic mechanical analysis (DMA), respectively. Preferential intercalation behavior of clay in PP/PS blends was found. The dispersion of clay is significantly influenced by the polarity of PP and PS, meanwhile the location of clay can be controlled by the alternation of the polarity of PP and PS through chemical modification. The clay migrates from PS phase to PP phase with the improvement of the polarity of PP. However, when the PS is sulfonated, clay migrates back to the dispersed PS phase again. The dispersion and location of clay have profound influence on the thermal and dynamic mechanical behavior of PP/PS blends. The better the dispersion of clay in either continuous phase or disperse phase, the higher the thermal stability of the blends. Besides, samples with clay located in the continuous phase can display the best strengthening effect.

A model experiment was done to clear the formation mechanism of protective layers during combustion of polypropylene (PP)/organically modified montmorillonite (OMMT) nanocomposites. The investigation was focused on the effects of annealing temperature on the structural changes and protective layer formation. The decomposition of OMMT and degradation of PP/OMMT nanocomposites were characterized by means of thermogravimetric analysis (TGA). The structural evolution and composition change in the surface region of PP/OMMT nanocomposites during heating were monitored by means of X-ray photoelectron spectroscopy (XPS), ATR-FTIR and field emission scanning electron microscopy (FESEM). The results showed that the formation of the carbonaceous silicate barrier in the surface region of PP/OMMT nanocomposites resulted from the following three processes: (1) The formation of strong acid sites on the MMT sheets, which could promote the degradation of PP and the carbonization of its degradation products; (2) The gases and gas bubbles formed by decomposition of the surfactant and degradation of PP, which pushed the molten sample to the surface; (3) The degradation of PP and the carbonization of the degradation products, which led to accumulation of MMT sheets tightly linked by the char in the surface region.

This paper is to investigate the effect of cyclic shear direction (or phase difference) on the accumulation of excess pore water pressure during cyclic shear and on the recompression after cyclic shear. Several series of uni-directional and multi-directional cyclic simple shear tests under undrained condition were carried out for normally consolidated Kaolin. From the test results it is shown that the accumulation of pore water pressure and the post-cyclic settlement increase with the shear strain amplitude and the phase difference. The values of the shear strain amplitude at which the effect of cyclic shear direction is most significant, decrease with the increase of the number of cycles. The change of the void ratio in the recompression stage increases approximately in proportion to the logarithm of the stress reduction ratio and is not affected by the shear strain amplitude. For multi-directional cyclic shear, this change of the void ratio depends on the phase difference and the number of cycles. The cyclic recompression indices in the recompression stage were obtained for uni-directional and multi-directional cyclic shears. The cyclic shear induced settlement can be calculated by using these indices.

In order to reduce the brittleness of soil stabilized by lime only, a recent study of a newly proposed mixture of fiber wastes and lime – rice hush ash mixtures for ground improvement is described in this paper. The research was conducted to investigate the influence of the mixture of wastes fibers on the mechanical properties of the stabilized clay soil with lime-rice husk mixtures. The amount of lime and rice husk ash was used 12% by dry weight of soil specimen. The fiber content and length are 0.4% (by weight of the parent soil) and 2 mm respectively. The specimens were subjected to triaxial tests under unconsolidated – undrained condition (UU) condition which is tested after 3, 7, 14 and 21 days of curing. Stress and strain relationship shows the post-peak stress which indicating ductility behavior of the treated soil. It was found that the addition of fibers contributed significantly on the shear strength parameters of the treated soil and the shear strength increased with increasing the curing time.

Leachate from waste landfill is attracting attention due to environmental impacts related to pollution of groundwater and surface water. Typically, four groups of leachate pollutants namely dissolved organic matters, inorganic matters, heavy metals, and xenobiotic organic compounds vary in concentration during acid phase and methanogenic phase required landfill to be lined. Several types of liners consist of clay, geomembranes, geotextiles, geosynthetic clay liner, and geonet are generally used in municipal solid waste (MSW), which have to take into considerations of hydraulic conductivity, shear strength, chemical compatibility, and resistant to creep and puncture.