Finite Element Method for Improving Soft Soil Underneath a Ballast Railway Track


It is always recommended to improve the properties of the soft soil beneath the railway networks often in such cases to increase its ability in bearing different applied loads and to control the expected generated settlements. The most methods used to improve the soil is by using a ballast layers with or without reinforced single geogrid layer or a geogrid layers at different spacing. This study presents a three-dimensional finite element analysis for soft soil underneath a ballast railway track by using a finite element program (ANSYS) which considers in these days the most software using in many engineering applications and most completeness. Twenty four models were created using a nonlinear three- dimensional finite element to study the effect of ballast thickness, mechanical properties of soft soil (undrained shear strength and modulus of elasticity), geogrid layer reinforcement to improve the soft soil. The ballast, soft soil and steel plates were modeled by using 8-nodes brick element with three degree of freedom per node. While, 4-nodes Shell element with six degree of freedom per node was used to represent the geogrid layer under and between ballast. The results show that increasing the undrained shear strength (Cu) and modulus of elasticity (E) lead to decreasing the settlement of soft soil and increasing the ultimate load. Increasing ballast thickness lead to decreasing the settlement of soft soil and increasing the ultimate load, this means that modulus of elasticity and shear strength playing main role to controlling in settlement of soft soil (ultimate displacement under plate loading ) and ultimate load