Field testing and analysis of high speed rail vibrations
- a Heriot-Watt University, Institute for Infrastructure & Environment, Edinburgh, UK
- b Department of Theoretical Mechanics, Dynamics and Vibrations, University of Mons, 31 Boulevard Dolez, B-7000 Mons, Belgium
- c University of Porto, Faculty of Engineering, Porto, Portugal.
- d University of Edinburgh, Institute for Infrastructure and Environment, School of Engineering, AGB Building, The Kings Buildings, Edinburgh, UK
- Received 20 May 2014, Revised 29 August 2014, Accepted 31 August 2014, Available online 26 September 2014
Highlights
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Experimental datasets (vibration time histories) made freely available for download.
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Field experiments performed on 3 high speed rail lines: grade, embankment, cutting.
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Multi-channel analysis of surface waves used to characterise each site.
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Cuttings produce highest vibration levels and embankments produce lowest.
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Horizontal vibrations can be more dominant than vertical vibrations (large offsets).
Abstract
This paper outlines an experimental analysis of ground-borne vibration levels generated by high speed rail lines on various earthwork profiles (at-grade, embankment, cutting and overpass). It also serves to provide access to a dataset of experimental measurements, freely available for download by other researchers working in the area of railway vibration (e.g. for further investigation and/or the validation of vibration prediction models).
First, the work outlines experimental investigations undertaken on the Belgian high speed rail network to investigate the vibration propagation characteristics of three different embankment conditions. The sites consist of a 5.5 m high embankment, an at-grade section and a 7.2 m deep cutting. The soil material properties of each site are determined using a ‘Multichannel Analysis of Surface Waves’ technique and verified using refraction analysis. It is shown that all sites have relatively similar material properties thus enabling a generalised comparison.
Vibration levels are measured in three directions, up to 100 m from the track due to three different train types (Eurostar, TGV and Thalys) and then analysed statistically. It is found that contrary to commonly accepted theory, vertical vibrations are not always the most dominant, and that horizontal vibrations should also be considered, particularly at larger offsets. It is also found that the embankment earthworks profile produced the lowest vibration levels and the cutting produced the highest. Furthermore, a low (positive) correlation between train speed and vibration levels was found. A selection of the results can be downloaded from www.davidpconnolly.com.
Keywords
- High speed rail;
- Railway;
- Vibration prediction;
- Ground borne vibration;
- Download data;
- Embankment;
- Cutting;
- Environmental impact assessment;
- EIA;
- Ground-borne noise;
- Experimental testing;
- MASW;
- In-situ testing
1. Introduction
The rapid uptake of high speed rail has been in-part due to its superior economic, social and environmental benefits [6] in comparison to other modes of transport. On-going research into aerodynamics, construction materials and motor technology has allowed for the development of lightweight trains capable of reaching increasingly higher speeds. Japan holds the world record for the fastest high speed rail velocity of 581 km/h which is close to the speed experienced by a typical commercial jet.
One negative environmental side effect of high speed rail is the elevated levels of ground-borne vibration generated [7]. These vibrations are generated at the wheel/rail interface and arise from the train weight (quasi-static excitation), from changes in support stiffness (e.g. regularly spaced sleepers) and irregularities in the wheel/rail geometry (dynamic excitation) [50] and [12]. Additionally, vibration amplitude levels may be elevated if the train speed becomes comparable with the natural Rayleigh wave speed in the supporting soil [17], [21], [24], [37] and [43], or if the excitation frequency is close to a track natural frequency [23].
These vibrations can cause significant negative effects such as personal distress in communities residing close to the lines. Therefore it is important to predict vibration levels before the line is constructed [11] and [13]. A vast body of prediction models has been proposed for investigating vibration levels on at-grade track sections [3], [15], [26], [36], [37], [40], [47] and [51] and underground lines [1], [27], [29], [30], [42], [45] and [52]. Despite this, research related to railway vibrations under different earthwork profile conditions is scarce.
An advantage of an experimental study over a numerical one is that a reduced number of modelling assumptions are required. For example, [20] presented an analytical model for the investigation of vibrations due to an embankment and it was shown that the embankment was a source of high frequency vibration. Despite this, the embankment was assumed to have vertical sides and the train excitation was uncoupled from a simplified track model. Another approach was presented by [8] who used a 3D finite element (FE) modelling approach to analyse vibrations within embankments with varying stiffness. It was shown that stiff embankments provided superior vibration performance in comparison to soft ones. A drawback of the FE approach is that assumptions must be made concerning the distribution of soil properties, and high frequency content can be difficult to simulate.
To overcome some of the limitations associated with numerical analysis [18], [25], [31] and [32], performed experimental analysis on at-grade railway tracks to analyse the characteristics of railway vibration. Despite this, few investigations have been undertaken into embankment vibration. One of the few studies used accelerometers to record ground movement on the rail, sleeper and an embankment made from compacted gravel [39]. It was found that the dominant frequencies within the embankment were between 40 and 70 Hz, with the spectrum reducing in frequency with distance from the embankment shoulder. Unfortunately the results were not compared to non-embankment data.
To the authors’ knowledge, there is no published literature related to the experimental analysis of vibration from railway cuttings. Therefore this paper attempts to compare the vibration levels generated by cuttings, embankments and at-grade track sections, via field experiments [10] and [33]. First, experimental investigations are performed at three Belgian test sites. Vibration levels are recorded in all three component directions and vertical vibrations are recorded up to a distance of 100 m from the track. All sites are found to consist of similar soil characteristics as determined through Multichannel Analysis of Surface Waves (MASW) testing, thus allowing for a general comparison between vibration characteristics. In addition to earthwork profile conditions, the effect of train type, horizontal vibration and abutment presence are investigated. A key aim of this paper is to provide a series of vibration records that researchers can use for further investigation and for the validation of numerical prediction models.
2. Test site details
2.1. General
2.1.1. Site 1—At-grade
Site 1 consisted of an at-grade railway section (Fig. 1 and Fig. 2) 4 km south of the town of Leuze-en-Hainaut. The track was a classically ballast track composed of ballast, subballast and subgrade layers, with thicknesses 0.3, 0.2 and 0.5 m, respectively. The rails were continuously welded UIC 60 rails with a mass of 60 kg/m3 and fixed to the prestressed concrete sleepers (300 kg monoblock) via Pandrol clips (Fig. 3). The rails were also supported by railpads with thickness 0.01 m. The irregularity of the rails (for all test sites) was assumed to be very low because grinding had been performed eight days before testing. It was also assumed that the standard of track geometry was high and identical across all test sites.
