Abstract: Based on the generalized formulation of two dimensional Biot′s theory of consolidation, the effect of geotextile and prefabricated vertical drains (PVDs) using in soft soil foundation was studied with nonlinear finite element method. The dissipation of excess pore pressure, vertical settlement and lateral displacement of foundation were contrasted between foundations with and without PVDs. It is found that the vertical settlements become lager, the lateral displacements become less and the bulges at the toe of embankment become less at the same time of consolidation when PVDs are used. And the stability of embankment improved for the bearing capacity of soil enhanced with excess pore pressure dissipated fast. Meanwhile, the axial force of geotextile become less when PVDs are used. Those changes showed that the design of foundation can be optimized by shortening the time of consolidation when PVDs are used.
Abstract: In order to analyze the characteristic of lateral displacement of soft soil foundation under embankment, a typical embankment is studied systemically with nonlinear finite element method, and the location of maximal lateral displacement and its measuring method is also discussed. It is pointed that lateral displacement would be reduced possibly at consolidation stage with strong dry crust and thick soft soil layer, which happened synchronously with vertical settlement increased rapidly. This phenomena could not be measured conveniently with inclinometer pipe, for there are many shortcomings within this technique, although which has been used in engineering widely. It is also shown that the location of the maximal lateral displacement is changeable at different construction stages, which more likely lies in the vertical surface between the toe and the middle of slope of embankment. In order to get the maximal lateral displacement reasonably, it is suggested that the inclinometer pipes should be placed in that area of embankment.
Abstract: The ZSM-5 zeolites of various SiO2/Al2O3 ratios were synthesized without using any template agent. X-ray diffraction (XRD), transmission electron microscope (TEM), temperature- programmed desorption of ammonia (NH3-TPD) and Fourier transform infrared spectroscopy (FT-IR) techniques were employed to analyze the natures of the as-synthesized zeolite. The results show that the as-synthesized non-templated ZSM-5 zeolite is very pure. Meanwhile, Lewis acid sites and Bronsted acid sites are all presented in the as-synthesized non-templated HZSM-5 zeolite. The number of acid sites decreases almost linearly with the increasing of SiO2/Al2O3 ratio of the zeolite. In addition, the reaction of propylene oligomerization was carried out over the as-synthesized non-templated HZSM-5 zeolite to evaluate the catalytic properties. The results show that the catalytic activity of propylene oligomerization decreases with the increasing of SiO2/Al2O3 ratio.
Abstract: A MoS2/TiO2 composite was synthesized and its photocatalytic activity for the degradation of methylene blue was evaluated. The results showed that the nano-MoS2/TiO2 composite presented excellent photocatalytic properties in the degradation reaction of methylene blue, which was ascribed to the good absorption of nano-MoS2/TiO2 in the visible light region. The decoloration rate of methylene blue solution was influenced by the dosage of nano-MoS2/TiO2 and the initial concentration of methylene blue. However, both the pH value and the degradation temperature had negligible effects on the decoloration rate of methylene blue. Moreover, the nano-MoS2/TiO2 composite as the degradation catalyst of methylene blue was of good regeneration properties.
Abstract: The leaching tests of heavy metals in industrial sewage sludge were carried out under different pH of extractant by the solid waste extraction procedure for leaching toxicity (GB5086.2-1997) of China on the base of the contents and fractions of Zn, Cu, Pb, Cr, Mn and Ni elements. The results showed that the sludge was with higher levels of Mn and Zn, followed by Cu and Ni, while the higher toxicity of Pb and Cr was lower. The fractions of different elements in the sewage sludge had very different forms. The potential migration and biological toxicity were a concern for the active forms of Zn, Mn, Ni, Cr because their active proportions were more than 50%. The pH of extraction solutions had an important impact on the leaching of heavy metals in sewage sludge. The largest concentrations of Zn, Mn, Ni, Cu were appeared when the pH of extractant was about 7, but that of Fe had a greater fluctuation at the same pH. The concentrations of heavy metals had very different at different pH values, which may be related with the process of adsorption/desorption, complexation/dissociation, the dissolution/precipitation/co-precipitation and other chemical reactions in the extractant process.
Abstract: The improvement of expansive soil with chemical medicine has been concerned by geotechnical engineers. The cation modifier is used to improve the expansive soil in embankment engineering of an express highway in Yunnan province. The modified test results indicate that the hydrophilic nature and swelling-shrinkage properties of samples are changed drastically. The free swelling ratio decrease and the particle size gradation, strength characteristics and hydrological properties of the treated expansive soil are improved by a wide range. The clay content decreases, but the silt content increases. The void ratio decreases sharply, but the fabric becomes more compact. The change of dry density with water content changing is less, but the water stability of modified soil is improved. The indexes are satisfied with the project requests and the engineering cost reduces.
Abstract: Sludge from the textile dyeing industries was solidified and stabilized using cement, fly ash（PFA）and cinder as the solidifying agents, and the optimum conditions of sludge solidification/stabilization were analyzed. The mechanical property of solidified sludge block was evaluated by compressive strength test, at the same time， the chemical oxygen demand (COD） and heavy metal concentration of the leaching from the cured block were tested as well. With the dosage of cement, PFA and cinder, 0.15kg/kg, 0.02kg/kg and 0.08kg/kg respectively, and curing time was 6ds, the compressive strength of the solidified sludge block reached 330kPa.Results showed that addition of cement and cinder had good effects on the compressed strength of sludge block, cement, PFA and cinder enhanced the solidification and stabilization of organic and heavy metal in the sludge. Under the above conditions, COD of the leaching from the sludge solidification block was 488mg/L, and the heavy metal concentrations had reached the related national standards. After 6ds of curing time, water ratio of the solidified block was maintained at 40%~45%, which met the prescribed standards of landfill.
Abstract: This study focused on the change of bacterial communities from a new denitrificatin technology where corncob was used as carbon source and the only physical support for microorganisms, under different dissolved oxygen (DO) conditions. The polymerase chain reaction (PCR) and denaturting gradient gel electrophoresis (DGGE) technique was used for extracting DNA from biofilm samples which collected from corncobs. The sequences of several 16S rDNA DGGE fragments were determined, and the dominant bacterial species that were present in each sample were proposed after comparing the results with data of the NCBI Gene Bank. The results indicated that PCR-DGGE technique was successfully used in this study. Clear relationship was found between DO condition and dominant bacterial communities during the experiment. Facultative anaerobic microorganism such as Bacteroidetes and Clostridium were found as dominant bacteria when DO was lower than 1mg/L. And aerobic microorganism such as Bacillus became the dominant bacteria when DO in the water was high than 2mg/L. These bacterial species mentioned above are all main types of denitrifying bacteria reported in other researches. And the results are helpful to explain the phenomenon why high nitrate removal efficiency was always found when DO condition changed. In addition, the results provided some valuable references for studing bacterial communities under different DO conditions.
Abstract: This paper studies the effects of proportion of emulsion asphalt and cement, sand gradation and sand-to-cement ratio on 28d strength of CA mortar solidified body according to compressive strength. Results show that compressive strength of CA mortar evidently decreases with increase of quality ratio of emulsion asphalt and cement, and increases with sand gradation attenuated. 28d compressive strength of CA mortar obviously reduces when the sand-cement ratio is above 1.4. Mechanical performance and intensity capability of CA motor solidified body are determined by microstructure of solidified body and content of free asphalt, encapsulation and cementation state of microstructure.
Abstract: Cu-doped TiO2 photocatalysts were synthesized by a homogeneous hydrolysis and low temperature crystallization method using tetrabutyl titanate as the titanium source and cupric acetate as the doping agent. The phase structure, composition and morphology of the product were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS) and Brunauer-Emmett-Teller surface area analysis (BET). The XRD results confirmed that the crystalline phase of all prepared samples was anatase-type TiO2. SEM results showed that the Cu-doped TiO2 were composed of spherical particles with particle diameter smaller than 20 nm. Furthermore, the photocatalytic activity of the Cu-doped TiO2 catalysts were evaluated based on the photocatalytic degradation of methyl orange (MO) in aqueous solution. The results showed that Cu-doped TiO2 had the higher visible-light-induced catalytic activity than the commercial P25 TiO2 powder. The copper content in Cu-doped TiO2 had obvious effect on the visible-light-induced catalytic activity, and the degradation rate of MO could reach 33.7% using Cu-doped TiO2 with a doping level of 1.0 mol% Cu as a photocatalyst under the visible light irradiation for 3 hours.