Geocell performance in stabilising railway ballast over soft clay subgrade

A three-dimensional finite element model is developed to investigate the effects of geocell inclusion within a railway ballast overlying typical soft clays found in the coastal regions. A cyclic train wheel load with an appropriate dynamic amplification factor was considered to realistically model operational train speeds on a narrow-gauge network. The effect of the geocell placement depth within the ballast/subballast zone, geocell stiffness, geocell shape and ballast shear strength was studied. Track and subgrade settlement, stresses, as well as lateral ballast stability were monitored and reported. Contrary to some previous studies, the track response is more realistically captured, providing a proper indication of maintenance issues. Geocells are found to increase track performance by reducing track settlement by as much as 73%, with a substantial reduction of subgrade settlement (maximum 35% reduction) and transmitted stresses (maximum 71% reduction). Track resilience, measured as long-term settlement and stress amplitudes, was found to improve with geocells. Triangular geocells showed a superior performance in reducing track settlement and stresses, while the rhomboidal shape reduced lateral spreading the most. Geocell deformation was examined to explain the different observations. The geocell placement depth influences the lateral ballast spreading, subgrade stresses and geocell strains.