Effect of geosynthetic reinforced fill on the frequencycontent of earthquake zones

Destructive seismic loadings pose a great threat to the structural integrity of the soft soils underlying foundations in terms of service quality and serviceability. One of the effective means of improving soil is to make use of geosynthetic materials. Geosynthetics are commonly used as a reinforcement element in reinforced soil underlying foundations, to diminish the effects of earthquakes on structures. It is a proven fact that geosynthetics increases the bearing capacity of the soil and decreases the overall or partial settlement of soil under static loadings. The objective of the presented thesis is to understand the effect of the geosynthetic reinforcement, particularly geogrid, on the seismic behavior of the soft clayey soil underlying gravel fill, and examine the seismic performance of the geogrid reinforced soil under different ground motions. The identical prototypes of unreinforced fill and geosynthetic reinforced fill were numerically modelled using the finite element software. The focus of the study is to determine the impacts of different peak ground accelerations under different frequency of motions on the seismic performance of unreinforced and reinforced cases on the same model made up of soft clayey soil overlain by gravel. The comparison of unreinforced and reinforced cases were evaluated following numerical analyses of the average values of acceleration for the selected points and average energy values were computed with Arias Intensity. The expected result was that geogrid would absorb the energy and thus the energy at the selected points would be lessened in the reinforced case. Results show that most of the reinforced cases decreased the transmitted energy through the soil and the proposition is true for 70% of the results. However, the energy difference between the geogrid reinforced and the unreinforced cases is so minimal that gravel overlying soft clayey soil may have a greater influence than geogrid on the seismic behavior of soil.