شبیه سازی عددی اثر مسلح سازی بستر راه با ژئوگرید در آزمایش میدانی

One of the appropriate methods to improve the roadway that is built on the weak subgrade is use of geosynthetic reinforcement that was already highly regarded. Geogrid and geotextiles are commonly used as reinforcements in pavement and unpaved systems. Geogrid is a net-like geosynthetic with apertures of sufficient size to allow interlocking with surrounding unbound materials such as soil, rock, and aggregate, and functions primarily as reinforcement. Geogrids also provide restraint to the aggregate and minimize lateral spreading of the base course aggregate when subjected to vehicular loads. Many field and laboratory test conducted to investigate the behavior of reinforced subgrade and achieve to the suitable design methodology has been implemented. Through both laboratory and field studies, it has been shown that the inclusion of geogrids at the interface between the base course and subgrade in unpaved road can improve the performance road by extending the service life or reducing unpaved structural thickness with equivalent performance.However, due to limitations such as high cost of laboratory or field test, evaluate the performance of reinforced roads under traffic loads by numerical simulation methods have been developed. Numerical analysis helps researcher predict performance of road via simulation and also Numerical analysis are capable that with simulation of paved and unpaved road, develop the parametric studies for complex structures such as reinforced subgrade. Finite element method (FEM), discrete element method (DEM), and finite difference method (FDM) are three types of numerical analysis commonly used by civil engineers.In this study, the finite element method (FEM) is used to investigate the behavior of the geosynthetic reinforced roads. Therefore, the three-dimensional model in ABAQUS that has several advantages compared to the two-dimensional model conducted and the results of the 3d numerical study with field tests results in Montana university - Bazmn, is compared, then the effect of reinforcing mechanical properties, elastic module of base layer and reinforced substrate on settlement was evaluated. The performance of the test sections has been evaluated from measurements of rut depth and the results showed that the simulation by finite element method, according to the assumptions used in three-dimensional modeling includes the quasi-static loading and frictional interaction parameters in terms of the contact surfaces, have a good agreement with the results of field test. The effect of geogrid reinforcement was shown to reduce surface deformation, improve stress distribution on subgrade layer, and reduce strain induced at the bottom of the base layer due to lateral spread. FEM results indicated that geogrid reinforcement can provide lateral confinement at the bottom of the base layer by improving interface shear resistance and increasing mean stress at the bottom of the base layer. The numerical study results also show that the settlement of reinforced road strongly influenced by the mechanical properties of reinforcement.With reduce the elastic module of geogrid(50%) the surface settlement about 61 percent increased and also effect the stiffness of subgrade and base layer in reinforced test section on the surface settlement compared to unreinforced test section about 50% reduced. In general, geogrid with higher tensile modulus enhanced the reinforcement effects.