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Along with the rapid expansion of urban rail networks comes the need for accurate predictions of railway induced vibration levels at grade and in buildings. Current computational methods for making predictions of railway induced ground vibration rely on simplifying modelling assumptions and require detailed parameter inputs, which lead to high levels of uncertainty. It is possible to mitigate against these issues using a combination of field measurements and state-of-the-art numerical methods, known as a hybrid model. In this paper, two hybrid models are developed, based on the use of separate source and propagation terms that are quantified using in situ measurements or modelling results. These models are implemented using term definitions proposed by the Federal Railroad Administration and assessed using the specific illustration of a surface railway. It is shown that the limitations of numerical and empirical methods can be addressed in a hybrid procedure without compromising prediction accuracy.

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Block walls, consisting of stacked unreinforced prefabricated concrete blocks, are commonly used for the construction of quay walls in the presence of rocky subgrades. A traditional design of block quay walls is based on manual design iterations, envisaging sufficient safety against ultimate limit states (ULS) such as sliding, overturning or loss of bearing capacity of the foundation soil. In addition, the designer should consider stability during the different construction stages of the block wall, referred to as construction constraints. This design process can be laborious, while the resulting designs comprise a large volume of concrete. In order to optimize block quay walls, we developed an automated design procedure in the framework of gradient-based optimization, accounting for the various ULS and construction constraints encountered in engineering practice. The design checks for a block quay wall are first explained in detail. This includes global ULS requirements that apply to the block wall as a whole, and internal ULS requirements to consider sliding and overturning of separate blocks. During all construction stages, the block wall has to be stable, which imposes additional construction constraints. Block walls consisting of rectangular blocks and chamfered blocks are optimized. The resulting designs obtained with the automated design procedure satisfy all design requirements, and have a realistic layout. Furthermore, the influence of the different construction stages is studied, demonstrating the practicality of the proposed automated design procedure.