Airborne and Ground-Borne Noise and Vibration from Urban Rail Transit Systems

The environmental effect of ground-borne vibration and noise generated by urban rail transit systems is a growing concern in urban areas. This chapter reviews, synthesizes and benchmarks new understandings related to railway vibration and associated airborne and ground-borne noise. The aim is to provide new thinking on how to predict noise and vibration levels from numerical modelling and from readily available conventional site investigation data. Recent results from some European metropoles (Brussels, Athens, etc.) are used to illustrate the dynamic effect of urban railway vehicles. It is also proved that train type and the contact conditions at the wheel/rail interface can be influential in the generation of vibration. The use of noise-mapping-based results offers an efficient and rapid way to evaluate mitigation measures in a large scale regarding the noise exposure generated to dense urban railway traffic. It is hoped that this information may provide assistance to future researchers attempting to simulate railway vehicle vibration and noise

Improving the energy efficiency of high speed rail and life cycle comparison with other modes of transport

The world energy crisis and global warming call for a reduction of energy consumption. High speed rail, increasingly viewed as an effective solution to inter-city passenger transportation challenge of the 21st century, has the significant ability of increasing passenger capacity and reducing journey time. The advent of high speed rail provided many research opportunities. So far studies have been contributed from different perspectives: economical, environmental, and technical. The main research gaps are: addressing the problem of the effects of route geometry on train energy consumption and quantifying the contributing factors towards differences in energy consumption between different types of high speed trains. In addition, this energy assessment cannot be based solely on the energy consumption in the operation phase. In the life cycle assessment of the whole railway system, the vehicle evaluation is relatively straightforward, but the infrastructure raises many difficult issues. In this thesis, an existing approach for modelling the traction energy of electric trains is developed and extended to simulate the train operation under different driving strategies. Baseline simulation is carried out to estimate the journey time and energy consumption of a High Speed 2(HS2) reference train running on the London-Birmingham proposed high speed route. The influence of route geometry and train configuration on energy consumption is investigated, based on the metric of energy consumption per passenger kilometre. Simulations are also carried out of different types of high speed rolling stock running on the proposed HS2 route, to identify the key areas of vehicle design which help to minimise the energy consumption of high speed rail travel. The life cycle assessment of railway infrastructure is carried out in four stages of a whole life cycle: production, operation, maintenance and disposal, the influence of route parameters on life cycle cost is also investigated. Finally, high speed rail is compared with competing modes of transport, i.e. the aircraft, the automobile and the conventional train, in both operational energy efficiency and whole life cycle analysis. The high speed rail transportation has great advantage over the road and air transport, giving a reduction of carbon emission by roughly 95%, among which the operation stage contributes the largest reduction.Open Acces

Proceedings of the 8th International Conference on Civil Engineering

This open access book is a collection of accepted papers from the 8th International Conference on Civil Engineering (ICCE2021). Researchers and engineers have discussed and presented around three major topics, i.e., construction and structural mechanics, building materials, and transportation and traffic. The content provide new ideas and practical experiences for both scientists and professionals

Numerical modelling of track-ground response induced by train passage

The global railway network is undergoing rapid expansion, with train vehicles becoming faster. Increases to operational train speed mean that it is more likely vehicles will induce larger dynamic effects within the supporting track and soil structure. At the same time, it is challenging to determine the type and depth of ground remediation required to reduce the track deflections. The present dissertation addresses the subject of vibrations induced by the passage of high-speed trains. The main aim of this work is to develop numerical tools that allow analysing track behaviour efficiently, investigating material non-linearity effect on the track dynamics, and also assessing the soil remediation strategies. Firstly, A semi-analytical model is proposed and designed for the dynamic analysis of track-ground vibrations induced by high speed rails. The model uses analytical expressions for the railroad track, coupled to a thin-layer element formulation for the ground. The model is validated using a combination of experimental railway field data, published numerical data and a commercial finite element package. It is shown to predict track and ground behaviour accurately for a range of train speeds. Moreover, it is used to investigate the effect of soil replacement/improvement below railway lines due to its low computational costs. Secondly, new insights are given to non-linear subgrade behaviour on high speed railway track dynamics. Built upon the proposed semi-analytical model, material non-linearity is accounted for using a ‘linear equivalent’ approach which iteratively updates the soil material properties. The model is validated using published datasets and in-situ field data. Four case studies are used to investigate the non-linear behaviour, each with contrasting subgrade characteristics. It is found that the critical velocity can shift to as low as 80% of the linear case, while rail deflections are up to 30% higher, depending on the material properties. Finally, a novel 2.5D FEM-BEM-TLM model is developed to include material non-linearity for both track structure and soil. The track structure is represented by a finite element model and the soil responses are obtained from boundary element model and thin-layer model. Material non-linearity is included using the proposed ’linear equivalent’ approach. The model is validated against the commercial FE software ABAQUS and numerical results from published literature. Two case studies are conducted to shed light upon the full material non-linearity effect on the dynamic track-ground responses from the train passage, revealing the necessity of its use, especially when high strains occur

Proceedings of the 8th International Conference on Civil Engineering

This open access book is a collection of accepted papers from the 8th International Conference on Civil Engineering (ICCE2021). Researchers and engineers have discussed and presented around three major topics, i.e., construction and structural mechanics, building materials, and transportation and traffic. The content provide new ideas and practical experiences for both scientists and professionals

Eleventh International Conference on the Bearing Capacity of Roads, Railways and Airfields

Innovations in Road, Railway and Airfield Bearing Capacity – Volume 2 comprises the second part of contributions to the 11th International Conference on Bearing Capacity of Roads, Railways and Airfields (2022). In anticipation of the event, it unveils state-of-the-art information and research on the latest policies, traffic loading measurements, in-situ measurements and condition surveys, functional testing, deflection measurement evaluation, structural performance prediction for pavements and tracks, new construction and rehabilitation design systems, frost affected areas, drainage and environmental effects, reinforcement, traditional and recycled materials, full scale testing and on case histories of road, railways and airfields. This edited work is intended for a global audience of road, railway and airfield engineers, researchers and consultants, as well as building and maintenance companies looking to further upgrade their practices in the field

Vibration from underground railways: considering piled foundations and twin tunnels

Accurate predictions of ground-borne vibration levels in the vicinity of an underground railway are greatly sought after in modern urban centers. Yet the complexity involved in simulating the underground environment means that it is necessary to make simplifying assumptions about this system. One such commonly made assumption is to ignore the effects of nearby embedded structures such as piled foundations and neighbouring tunnels. Through the formulation of computationally efficient mathematical models, this dissertation examines the dynamic behaviour of these two particular types of structures. The effect of the dynamic behaviour of these structures on the ground-borne vibration generated by an underground railway is considered. The modelling of piled foundations begins with consideration of a single pile embedded in a linear, viscoelastic halfspace. Two approaches are pursued: the modification of an existing plane-strain pile model; and the development of a fully three-dimensional model formulated in the wavenumber domain. Methods for adapting models of infinite structures to simulate finite systems using mirror-imaging techniques are described. The interaction between two neighbouring piles is considered using the method of joining subsystems, and these results are extended to formulate models for pile groups. The mathematical model is validated against existing numerical solutions and is found to be both accurate and efficient. A building model and a model for the pile cap are developed, and are attached to the piled foundation. A case study is used to illustrate a procedure for assessing the vibration performance of pile groups subject to vibration generated by an underground railway. The two-tunnel model uses the superposition of displacement fields to produce a fully coupled model of two infinitely long tunnels embedded in a homogeneous, viscoelastic fullspace. The significance of the interactions occurring between the two tunnels is quantified by calculating the insertion gains that result from the existence of a second tunnel. The results show that a high degree of inaccuracy exists in any underground-railway vibration prediction model that includes only one of the two tunnels present

Model Validation and Simulation

The Bauhaus Summer School series provides an international forum for an exchange of methods and skills related to the interaction between different disciplines of modern engineering science. The 2012 civil engineering course was held in August over two weeks at Bauhaus-Universität Weimar. The overall aim was the exchange of research and modern scientific approaches in the field of model validation and simulation between well-known experts acting as lecturers and active students. Besides these educational intentions the social and cultural component of the meeting has been in the focus. 48 graduate and doctoral students from 20 different countries and 22 lecturers from 12 countries attended this summer school. Among other aspects, this activity can be considered successful as it raised the sensitivity towards both the significance of research in civil engineering and the role of intercultural exchange. This volume summarizes and publishes some of the results: abstracts of key note papers presented by the experts and selected student research works. The overview reflects the quality of this summer school. Furthermore the individual contributions confirm that for active students this event has been a research forum and a special opportunity to learn from the experiences of the researchers in terms of methodology and strategies for research implementation in their current work

Ground borne vibrations from high speed trains

A consequence of high speed rail transportation is the generation of elevated ground borne vibrations. This thesis presents several original contributions towards the prediction of these vibrations. Firstly, a new three dimensional finite element model capable of vibration prediction was developed. Its main feature was its ability to model complex track geometries while doing so through a fully coupled vehicle-tracksoil system. Model output was compared to experimental results obtained during this thesis and also to independent data sets. It was shown to predict velocity time histories, vibration frequency spectrums and international vibration descriptors with high accuracy. An appraisal of the suitability of a finite difference time domain modelling approach for railway vibration prediction was also undertaken. This resulted in the development of a new ‘higher order’ perfectly matched layers absorbing boundary condition. This condition was found to offer higher performance in comparison to current alternative absorbing boundary conditions. Field work was then undertaken on high speed lines with varying embankment conditions in Belgium and England. Vibration data was recorded up to 100m from each track and geophysical investigations were performed to determine the underlying soil properties. The results were used for numerical model validation and also to provide new insights into the effect of various embankment conditions on vibration propagation. It was found that embankments generate higher frequency excitation in comparison to nonembankment cases and that cuttings generate higher vibration levels than noncuttings. Once validated the finite element model was used to provide new insights into the effect of train speed, embankment constituent materials and railway track type on vibration levels. It was found that the shape and magnitude of ground vibration increased rapidly as the train’s speed approached the Rayleigh wave speed of the underlying soil. It was also found that ballast, slab and metal tracks produced similar levels of vibration and that stiffer embankments reduced vibration levels at distances near and far from the track. Two vibration mitigation techniques were also explored through numerical simulation. Firstly, an analysis was undertaken to determine the ability of a new modified ballast material to actively isolate vibration within the track structure. Secondly, wave barrier geometries were investigated to optimise their performance whilst minimising cost. It was found that barrier depth was the most influential parameter, whereas width had little effect. Additionally, geometry optimisation was found to result in a 95% cost saving in comparison to a base case. Using a vast array of results generated using the previously developed finite element model, a new empirical prediction model was also developed, capable of quickly assessing vibration levels across large sections of track. Unlike currently available empirical models, it was able to account for soil properties in its calculation and could predict a variety of international vibration metrics. It was shown to offer increased prediction performance in comparison to an alternative empirical model