Topology optimization of jet-grouted overlapping columns for mitigation of train-induced ground vibrations

Train-induced ground vibrations are one of the major disadvantages of the railway transportation particularly in urban areas. These vibrations can cause discomfort to the people, malfunctioning of sensitive instruments and structural problems. Open trenches can effectively mitigate the ground vibrations; however, the construction of open trenches is limited to shallow depths due to the stability issues and unavailability of space in densely populated regions. Therefore, in-filled soft and stiff trenches can be used as an alternative for impeding the train-induced surface waves. This paper discusses the effectiveness of overlapping jet-grouted columns as stiff wave barrier walls for scattering or better yet filtering the train-induced ground vibrations. These barriers are located on the wave propagation path between the railway and the receiving points, and their optimal layout is identified using a new coupled genetic-algorithm/finite-element topology optimization methodology. It is observed that this methodology can effectively find the optimal topology of the jet-grouted barriers within the design domain. The results show that the barriers with larger heights provide better mitigation. In addition, the barriers tend to be located either in the vicinity of the track or the receiving points. To provide better judgment, the efficacy of the jet-grouted wave barriers is compared to open and in-filled trenches.