Semnan University Press Journal of Transportation Infrastructure Engineering 2423-5350 3 3 2017 11 22 Numerical Study of the Effect of Reinforcing Subgrade on Behavior of Reinforced Test Sections by FEM Numerical Study of the Effect of Reinforcing Subgrade on Behavior of Reinforced Test Sections by FEM 23 36 2739 10.22075/jtie.2017.1703.1161 FA Abdolhosein Haddad Associate Professor, Faculty of Civil Engineering, Semnan University, Semnan, I. R. Iran. Hamed Khakpourmoghaddam MSc. Student, Faculty of Civil Engineering, Semnan University, Semnan, I. R. Iran. Journal Article 2016 10 26 One of the appropriate methods to improve the roadway, built on the weak subgrade, is using geosynthetic reinforcement that is highly regarded. Few field and laboratory tests have been planned and conducted under the real traffic loading to investigate the behavior of reinforced subgrade and achieve suitable design methodology. However, due to such limitations as high costs of laboratory or field tests, their implementation is limited. Numerical simulation methods can help to study the performance of such reinforced roads and evaluate the effect of important parameters. In this research, three-dimensional finite element method (FEM) was used to investigate the behavior of the geosynthetic reinforced roads under traffic loads, and the results were validated with field data. Results of the numerical modeling and field studies showed that the numerical model can predict the behavior of a geogrid-reinforced system and there was a good agreement between the results of field studies and modeling responses. Results of the  numerical study also showed that the settlement of reinforced road is strongly influenced by the mechanical properties of reinforcement, including the stifness of the geogrid. Reduction of geogrid stifness by 50%, increased the surface settlement by about 61%. Also, effect of the stiffness of subgrade and base layer in reinforced test section on the surface settlement was 50% less than the unreinforced test section. Results showed TBR increase by 26.11 times due to the reinforcement of the test section with a strong reinforcing agent.  One of the appropriate methods to improve the roadway, built on the weak subgrade, is using geosynthetic reinforcement that is highly regarded. Few field and laboratory tests have been planned and conducted under the real traffic loading to investigate the behavior of reinforced subgrade and achieve suitable design methodology. However, due to such limitations as high costs of laboratory or field tests, their implementation is limited. Numerical simulation methods can help to study the performance of such reinforced roads and evaluate the effect of important parameters. In this research, three-dimensional finite element method (FEM) was used to investigate the behavior of the geosynthetic reinforced roads under traffic loads, and the results were validated with field data. Results of the numerical modeling and field studies showed that the numerical model can predict the behavior of a geogrid-reinforced system and there was a good agreement between the results of field studies and modeling responses. Results of the  numerical study also showed that the settlement of reinforced road is strongly influenced by the mechanical properties of reinforcement, including the stifness of the geogrid. Reduction of geogrid stifness by 50%, increased the surface settlement by about 61%. Also, effect of the stiffness of subgrade and base layer in reinforced test section on the surface settlement was 50% less than the unreinforced test section. Results showed TBR increase by 26.11 times due to the reinforcement of the test section with a strong reinforcing agent.  https://jtie.semnan.ac.ir/article_2739_a476a8a6b462cc1e0db38fa54ba2bed2.pdf