In recent decades, due to the increase in world population and the expansion of high-rise structures in advanced countries, the improvement of the strength and shear properties of soil has been of interest to geotechnical engineers. Various methods for improving the structure and mechanical properties, as well as increasing soil strength, can be categorized into five groups of physical, chemical, mechanical, biological, and electrical processes. In the physical process, reinforcing elements such as geosynthetics, metal strips, and polymers are used. Biological soil improvement is a novel method in which chemical and biological processes strengthen the physical and mechanical properties of the soil. Since this improvement is environmentally friendly and applicable to various types of soil, it has become a very efficient and suitable method for soil improvement projects in general. Microbially Induced Calcium Carbonate Precipitation (MICP) is one of the most recognized and best methods of biological soil improvement, in which after injecting a bacterial suspension (cement solution) into the soil, calcium carbonate precipitates are formed, resulting in significant improvements in soil properties. In this research, the performance of reinforced soil retaining wall models using layers of geosynthetic reinforcement along with biological deposition at the bottom and top of adjacent soil in a sandwich manner has been eva‎luated. The variables in this research are the number of reinforcement layers, the volume of cement solution, and the concentration of cement solution. Reinforced soil retaining walls using graded sand from the desert area and geotextiles woven with a tensile strength of 1.8 kilonewtons per meter were modeled. After identifying and designing the reinforced soil retaining wall experiments, three walls without biological stabilization were initially constructed as control samples with 3، 5 and 7 layers and loaded. Then, other models were designed and analyzed using the Taguchi Design of Experiment (TDOE) for ultimate load capacity and horizontal deformation. Based on existing records indicating improved tensile strength resistance of reinforcement elements, the use of a combined method of reinforcement and biological stabilization resulted in improved stability of the wall and reduced reinforcement components.

محمدرضا خان محمدي , محمدعلي روشن ضمير

امين ازهري , هاجر شرع اصفهاني