چكيده به لاتين
Soil quality and improvement are some of the issues that civil engineers have always been involved with and various methods have been used for different types of soils. The importance of the issue is to the extent that countries spend a lot of money per year to implement these projects. The use of biological improvement methods for the production of calcite cement has provided a new method for land improvement for geotechnical engineers. These methods use non-pathogenic microorganisms that are naturally found in the soil environment to produce natural cement among the soil grains. There is significant potential in these methods to reduce environmental concerns, and in the not-too-distant future, these methods may be able to replace traditional methods. In this study, using microbiological technology, Sporosarcina pasteurii، bacteria were used to improve sandy soil with SP-SM classification to cause sedimentation in soil and soil aggregates after performing suitable growth conditions by performing biochemical reactions. The microorganism was also cultured in the laboratory and injected into the soil with urea and calcium chloride. In this study, the effect of parameters such as volume and method of injection, number of injections, urea and calcium chloride concentration, and processing time on the improvement results were investigated. The results show that the mechanical properties of the improved sand, including compressive strength and modulus of elasticity, increase at 28 days after injection with more cycles and at a concentration of 1 M urea and calcium chloride solution so that in a period of 28 days, Soil compressive strength reached 1782 kPa. Finally, soil structural analyzes including XRD and SEM were performed on the samples and it was observed that the activity of microorganisms had a positive effect on the production of calcite sediment and increase soil resistance. Also, in the end, an estimate of the executive costs in case of project implementation on an industrial scale was made to make the implementation of this method more tangible for the reader in practice.
