Simulation of Suppressing Gas Formation during Deactivation of Gas-Generating Soils

Studies on simulation of suppressing gas formation during deactivation of gas-generating soils (GGS) by their chemical and biological treatment under anaerobic conditions are carried out. The chemical and gas-geochemical characteristics of GGS sampled from the wells drilled at different depths within in the construction site area (Moscow, North-Eastern Administrative Okrug) are examined. Simulation of an anaerobic gas-generating process has shown that the gas generation rate under conditions of natural occurrence (8–10°C) within the boundaries of the identified anomalous zones would be ∼215 L/(t year) in the center and ∼157 L/(t year) in the north of the site. The kinetics of organic matter degradation has revealed that the degradation rate constants of gas-forming substrates amount to 0.013 year –1 for the central zone and 0.009 year –1 for the northern zone. According to the prediction results, the main gas-generating phase will be complete within 55 years in the central zone and within 79 years in the northern one; the volume content of methane in gas production being equal to 9–12%. Simulation of chemical suppressing residual gas generation has shown that for the reduction of gas generation intensity by a factor of 10, it is sufficient to add a 45% calcium hypochlorite solution in the amount of 1% of the soil volume to the GGS massif lying in the central anomalous zone. Gas generation in soils varies from 1.6 to 35 L/(t year) after chemical treatment i.e., the process of gas generation in filled-in soils will in fact be suppressed almost completely. Simulation of a biological process of suppressing gas-generation in GGS of the northern zone caused by the presence of oil pollution made it possible to predict that the use of the certified preparation Rhoder at a dose of 1 × 10 9 CFU/mL will allow increasing sufficiently a degradation rate constant of hydrocarbons to 1.02 year –1 and reducing the time of their half-lifetime from 79 years to 0.68 years.