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Документ Formation of water-impermeable crust on sand surface using biocement(2011) Stabnikov, Victor; Naemi, Maryam; Ivanov, Volodymyr M.; Chu, JianThis paper examines the feasibility of using calcium-based biocement to form an impermeable crust on top of a sand layer. The biocement used was a mixture of calcium salt, urea, and bacterial suspension, which hydrolyzed urea with production of carbonate and an increase of the pH level. Applying 0.6 g of Ca per cm2 of sand surface, the permeability of the biocemented sand can be reduced from 10−4 m/s to 1.6•10−7 m/s (or 14 mm/day) due to formation of the crust on sand surface. The rupture modulus (maximum bending stress) of the crust was 35.9 MPa, which is comparable with that of limestone. The formation of a water-impermeable and high strength crust layer on sand surface could be useful for the construction of aquaculture ponds in sand, stabilization of the sand dunes, dust fixation in the desert areas, and sealing of the channels and reservoirs in sandy soil.Документ Development of microbial geotechnology in Singapore(2011) Chu, Jian; Ivanov, Volodymyr M.; He, Jia; Li, Bing; Naemi, Maryam; Stabnikov, VictorBoth nature processes and laboratory studies have shown that microorganisms can be used to improve the engineering properties of soil. As such, it is possible to develop methods that utilize the microbial process to treat soil in a way similar to that of cement. When more knowledge is accumulated through research findings and technology development, a new branch of geotechnical engineering – the Microbial Geotechnology can be established. The Microbial Geotechnology can have the following three applications: (a) biocementation to increase the strength of soil, (b) bioclogging to reduce the permeability of soil, and (c) biogas to increase the liquefaction resistance of sandy soil. Some types of microorganisms or bioprocesses that may contribute to the biocementation, bioclogging or biogas effects are identified and discussed. Some experimental data are presented to show that the permeability of sand can be reduced by four orders of magnitude and the strength of sand can be increased to a substantial value after the soil has been treated using bacteria. However, the whole study still stays at the laboratory stage and much more efforts are required to turn this scientific idea into viable technologiesДокумент Biocement: green building-and energy-saving material(2012) Chu, Jian; Ivanov, Volodymyr M.; Stabnikov, Victor; He, Jia; Li, Bing; Naemi, MaryamCement and chemical grouts have often been used for soil strengthening. However, high cost, energy consumption, and harm to environment restrict their applications. Biocement could be a new green building- material and energy-saving material. Biocement is a mixture of enzymes or microbial biomass with inorganic chemicals, which can be produced from cheap raw materials. Supply of biocementing solution to the porous soil or mixing of dry biocement with clayey soil initiate biocementation of soil due to specific enzymatic activity. Different microorganisms and enzymes can be used for production of biocement.