Wave barriers are a common mitigation measure when dealing with environmentally induced vibrations. These wave barriers generally consist of stiff vertical walls buried in the soil to impede waves on their path from the source to the receiver. The geometries of the wave barriers that are used in practice are very simple. More complex geometries have not often been considered as it is difficult to estimate which changes would increase the effectiveness.

In literature, topology optimization was explored as a method to design wave barriers. This method was applied while modelling the soil as a homogeneous elastic half-space. The resulting wave barriers showed a significant increase in the achieved vibration reduction. However, the designs were often very complex and hard to manufacture. In this thesis the method was improved by introducing a layered soil and by ensuring the manufacturability of the designed wave barriers.

The improved method was then applied to multiple situations in order to investigate aspects of wave barrier design and effectiveness. Optimization of a wave barrier for a two-layered soil model showed the significance of implementing a layered soil model. The interface between two layers resulted in reflections that could diminish the effectiveness of a wave barrier if not accounted for. The optimization algorithm responded to these reflections by placing material in the path of waves that would otherwise reflect back to the surface.

A wave barrier optimized for a three-layered soil model that consisted of a softer layer embedded in a stiff layer and a stiff half-space showed a different approach to reflections. The wave barrier appeared to use the softer layer as a waveguide in order to reduce the energy at the surface.

The manufacturability was increased by adding constraints. This resulted in wave barriers with a more manufacturable design at the cost of a decrease in vibration reduction. In three of the four cases, the optimized wave barrier still performed significantly better than the reference wave barrier. In one case, the final design reverted back to the reference wave barrier when the manufacturability conditions were applied.

The goals set at the start of the thesis were largely accomplished. The model was able to more accurately reflect soil profiles found in practice by using a layered soil model and the topology optimization algorithm resulted in wave barriers that are relatively easy to manufacture while still showing a significant improvement over the standard reference wave barriers. The possible use of
soft embedded layers as waveguides was discovered during the optimization. Future research into this possibility could prove valuable. Some concerns are posited with regards to the reliability of the wave barriers. In some cases, the optimized wave barrier appeared to abuse the idealized representation of the interface between layers. An initial investigation showed that in those cases,
the effectiveness of the wave barrier was sensitive to changes of the interface depth. Further investigation would be required to determine the sensitivity of the designed wave barriers to other parameters related to the idealized representations of the interfaces.

In this thesis a parametric finite element model has been developed to predict the printability of concrete structures of arbitrary geometries. The model can be used to effectively explore design and process parameters to optimize printed objects. In addition, the model can be used to improve the reliability of the printing process, reduce the number of failures during production and enhance the production capabilities of complex geometries. A comprehensive experimental programme was designed in which uniaxial compression tests have been performed to determine the development of the mechanical properties of the concrete during the printing process. A novel method was created by which test samples could be extracted directly from printed concrete in order to incorporate the influence of the full printing process on the properties of the concrete. Moreover, from both literature and the valuable experience in printing of Bruil it was known that the temperature of the concrete mix can have a major influence on the mechanical properties of concrete. Therefore, the performance of the concrete under elevated temperatures was included in the research too. On top of that, printing experiments were conducted in which two geometries were printed multiple times to characterize the reliability of the printing process, and to verify the finite element models with.

The hyperloop system is a new transportation mode, which consists a magnetic levitating capsule-like hyperloop pod and a vacuum tube. Due to small air hindrance, the hyperloop pod is conceived to have a maximum speed of 333 m/s. If such a hyperloop system is to be built underground in soft soils, the hyperloop speed can easily reach the wave propagation speeds in the soil. Strong wave radiation is expected when the hyperloop is travelling at wave propagation speeds, which are called the critical speeds.

The first objective is to analyse the dynamic influence from the hyperloop. A linear elastic half-space with an infinitely long concrete tunnel buried at a certain depth has been modeled. The excitation of the system is a hyperloop modeled as a moving constant load acting at the tunnel invert. In this thesis, a so-called indirect boundary element method (BEM) is applied. Indirect boundary integrals are formed which rely on the fundamental solutions for the interior medium, the two-and-a-half dimensional Green's functions. These 2.5D Green's functions are essentially the steady state solutions of the half-space subjected to a spatially varying line load. The space is assumed to be infinitely long and invariant in the direction parallel to the axis of the tunnel.

Before implementing the BEM model, two improvements have been made to the 2.5D Green's functions: a better convergence of the Green's function surface-related terms and a better satisfaction of stress-free boundary conditions at the free surface. The accuracy and correctness of the boundary element model using the improved Green's functions have been verified by intensive case studies. Firstly, the scattering of 3D harmonic seismic P waves by a cavity and a tunnel in a linear elastic half-space is analysed. Results are validated by comparing to those from literature. Secondly, the BEM model is employed for the moving load problem. The embedded concrete tunnel is modeled using the Donnell's theory for thin shells. A coupled form of the indirect boundary integrals is formulated. Using the same model parameters, the results obtained by the BEM are in good agreements with those from literature. Moreover, a parametric study has been conducted to study the effect of moving load velocity, tunnel depth and thickness of concrete lining on the dynamic response.

As a second objective of the current thesis work, the BEM model is compared with a finite element method (FEM) based model, developed by Movares B.V. The models are compared in both accuracy and computational efficiency. In the FEM model, the moving load is considered as a series of consecutive short pulses. The contributions from all the pulses are synthesized using a convolution. Furthermore, since the space is invariant in the direction parallel to the tunnel axis, it is possible to apply just one stationary impulse load in the finite element model. Using this method, a constant moving load and a moving load with acceleration are modeled. The FEM results are found to have close agreements with those by the BEM. Besides the Rayleigh wave speed in the soil, a second critical velocity which is related to the wave propagation in the tunnel is found. Furthermore, the case where a hyperloop runs constantly at the Rayleigh wave speed is more crucial than the case where the hyperloop accelerates and passes the Rayleigh wave speed.