Seismic railway alignment optimisation integrating probabilistic fault-crossing risk assessment

When designing railways in earthquake-prone regions, it is generally difficult to bypass all the active fault zones in the study area. Therefore, the fault-crossing risk is a crucial factor that should be considered during the early railway alignment design stage. However, little attention has been paid to this topic in the literature. To this end, a probabilistic fault-crossing risk assessment model and a methodology for seismic railway alignment optimisation are proposed in this paper. First, a Probabilistic Fault-Crossing Risk Analysis (PFCRA) model, which combines three probabilistic analysis modules for fault displacement hazard, railway structural fragility and infrastructure monetary loss, is constructed particularly for fault-crossing railway planning and design. Then, this PFCRA model is integrated with a previous least-cost model to construct a cost-risk Net Present Value (NPV) model for railway alignment optimisation. To solve this NPV model, a particle swarm algorithm is improved with a tailored Monte Carlo simulation to estimate and optimise the construction costs and possible fault-crossing risks concurrently for railway alignments. Lastly, a representative real-world railway example is employed as the case study for the developed method based on four groups of testing experiments.