Ground-borne Vibration Research Articles

Reliability of FTA general vibration assessment model in prediction of subway induced ground borne vibrations

One of the main factors in the design of subways is the level of subway-induced vibrations. The ground borne vibrations are usually estimated by prediction models among which the FTA (Federal Transportation Association) general vibration assessment model is the most popular one. Although FTA approach/model is vastly used in the design and operation of underground railway systems, its reliability has not been sufficiently evaluated in the available literatures. This is addressed in this research. For this purpose, a comprehensive experimental investigation (both in the time and frequency domains) was conducted in three newly constructed subway lines in the Iranian underground railway (subway) network. The track and soil characteristics as well as ground borne vibrations were measured. The reliability and accuracy of the FTA model was assessed through comparisons of the experimental results obtained here with the FTA predictions. Contrary to the current belief, considerable underestimations of subway ground borne vibrations in the FTA model predictions were shown in this research. The results obtained indicate up to 20 dB differences between the experimental results and those of FTA predictions. Based on the field measurements obtained here and the theoretical background, the FTA model was improved/optimized, leading to increase the reliability of FTA model predictions in subway systems.

Assessing subway network ground borne noise and vibration using transfer function from tunnel wall to soil surface measured by muck train operation

During the operation of urban subway rail transit system, ground vibrations are generated that transmitted through the ground and cause vibrations in nearby buildings. The operation of these systems can be characterized as a linear source that generates vibrations transmitted through the ground. These ground borne vibrations are a consequence of local defects on the train wheels and/or onto the rail track. The transmission of vibrations from subway rail transit systems in a neighboring building is mostly described by the transfer function (TF) of vibration diffusion from the tunnel wall or invert towards the soil surface at the façade of the protected heritage or residential building. A methodology is proposed in order to determine the TF of vibration diffusion inside the given geological media demonstrating the vibration attenuation values in 1/3 octave band analysis. The tunnel boring with the usage of TBM requires the existence of a muck train to remove the excavation materials. This paper presents the metrological methodology of the relevant measurement campaign and analyses the findings in several sections of the tunnel using the TBM's muck train implementing simultaneous vibration recordings both in tunnel wall and the soil surface. This metrological approach is significant ensuring a high accurate estimation of the expected ground borne noise and vibration at the façade of sensitive receptors during operation and evaluate the need of implementation of mitigation measures, such as floating slabs (FS) where mandatory.

Periodic track model for the prediction of railway induced vibration due to parametric excitation

Abstract Railway induced ground-borne vibration in urban areas has become a major environmental problem with large societal impact. Accurate computational models for the prediction of railway induced vibration generally require extensive modeling effort and computation time. To increase the computational efficiency, a large number of track models assume a simplified track structure in the longitudinal direction, therefore being unable to account for parametric excitation due to transition zones, hanging sleepers or spatially varying track or subgrade characteristics. This paper presents a track modeling approach based on a wave analysis technique for multi-coupled periodic structures that allows to efficiently model a track with varying characteristics in the longitudinal direction and, therefore, to predict railway induced vibration due to parametric excitation. The track is modeled by a finite number of track sections with different properties, while each section consists of periodic cells with the same properties. A case study is presented investigating a track with a transition zone between ballasted and slab track. The train-track interaction forces are computed, as well as the vibration of the sleepers, the slab and in the free field. The influence of the train direction and train speed is evaluated.

Reduction of ground-borne vibrations from rail lines on viaducts by means of elastic anti-vibration mats

In this paper, the effectiveness of elastic anti-vibration mats in reducing ground-borne vibrations from rail viaducts is investigated by means of theoretical analysis and is validated by the results of field tests. A two-step procedure is adopted for analyzing the vehicle-track-bridge-soil coupling system. In the first step, the train-track-bridge-pier subsystem is considered, and the bridge-bearing reaction force is solved. In the second step, the pier-pile-soil subsystem is considered, and the ground vibration solution is obtained by applying the negative bridge-bearing reaction force to the pier top on a pier-pile-soil model. The accuracy of the presented model is then verified in comparison with in-situ measurement results. On the basis of this comparison, a parametric study on the impact of anti-vibration mats on ground-borne vibrations was investigated theoretically, and the effectiveness of elastic anti-vibration mats with the suggested optimal parameters was further validated by field tests. The results show that when the stiffness of the elastic anti-vibration mats is 1.5 MPa/m, ground vibration decreases significantly and the vertical rail displacement agrees with high-speed railway regulations.

Annoyance in Response to Vibrations from Railways.

Rail transport is a key stepping stone in the EU’s transport policy and is pinpointed for investment and growth over the coming decades. This expanding infrastructure implies increased exposure to environmental stressors, such as noise and ground-borne vibrations. Little is known about the health impacts of exposure to these vibrations. The aim of this paper is to examine the association between annoyance from rail vibrations and the distance of residential dwelling from the railway. It reports the first results of a large epidemiological study, EpiVib, which was designed to investigate the long-term health effects of exposure to rail vibrations. The first part of this study examines a self-reported questionnaire. In total, 6894 individuals aged between 18 and 80 living within 1 km of a railway in west Sweden participated. Results presented here examine the association between distance to the railway and annoyance from vibrations and are stratified by train type. A positive association between closer distance and increased annoyance is seen. After adjustment for important modifiers, results showed that vibrations from freight trains and maintenance operations are reported to be moderately and highly annoying at distances of up to 400 m from the railway and diesel up to 300 m. Vibration from passenger and fast trains are significantly annoying up to 200 m from the track. Vibration from freight trains and maintenance operations were considered highly annoying up to 300 m from the track, diesel up to 400 m. Vibration from passenger and fast trains are not reported to be highly annoying after adjustment. Heavier, slower moving locomotives, in the form of diesel and freight trains, appear to be the source of annoyance at distances further from the railway compared to passenger and fast trains. This has implications in terms of property, transport, and infrastructure planning.

Scoping assessment of free-field vibrations due to railway traffic

The number of railway lines both operational and under construction is growing rapidly, leading to an increase in the number of buildings adversely affected by ground-borne vibration (e.g. shaking and indoor noise). Post-construction mitigation measures are expensive, thus driving the need for early stage prediction, during project planning/development phases. To achieve this, scoping models (i.e. desktop studies) are used to assess long stretches of track quickly, in absence of detailed design information. This paper presents a new, highly customisable scoping model, which can analyse the effect of detailed changes to train, track and soil on ground vibration levels. The methodology considers soil stiffness and the combination of both the dynamic and static forces generated due to train passage. It has low computational cost and can predict free-field vibration levels in accordance with the most common international standards. The model uses the direct stiffness method to compute the soil Green's function, and a novel two-and-a-half dimensional (2.5D) finite element strategy for train-track interaction. The soil Green's function is modulated using a neural network (NN) procedure to remove the need for the time consuming computation of track-soil coupling. This modulation factor combined with the new train-track approach results in a large reduction in computational time. The proposed model is validated by comparing track receptance, free-field mobility and soil vibration with both field experiments and a more comprehensive 2.5D combined finite element-boundary element (FEM-BEM) model. A sensitivity analysis is undertaken and it is shown that track type, soil properties and train speed have a dominant effect on ground vibration levels. Finally, the possibility of using average shear wave velocity introduced for seismic site response analysis to predict vibration levels is investigated and shown to be reasonable for certain smooth stratigraphy's.

Use of in-filled trenches to screen ground vibration due to impact pile driving: experimental and numerical study

Vibration generated by pile driving can cause discomfort to occupants of nearby buildings and disturb the activities carried out in the buildings. The transmitted vibration will depend on both the source and the transmitting medium (soil), while the acceptable levels of vibration will depend on the receiver characteristics. Existing structures in which some sensitive processes are ongoing such as hospitals and laboratories can easily be affected due to the received vibration. Introducing a trench into the path of wave propagation has become one of the solutions. There is however little experimental data available on the effects of trenches to screen such ground borne vibration, especially that caused by pile driving. This paper describes a series of experiments conducted to investigate the characteristics of impact pile induced vibrations and the effect of coal bottom ash filled trenches to screen this vibration. In addition to experimental testing, numerical simulations are also carried out using validated model to examine the effects of in-fill material, impact load, soil characteristics and distance from the source to the trench on the vibration screening ability. The results of the field experiments and the numerical study are analysed and interpreted to provide guidelines for future research and design.

A multidimensional valuation of the human perception of construction vibration

Previous studies have shown that annoyance due to vibration does not simply depend on the magnitude of vibration exposure. However, only little is known about the important features that contribute the human perception of vibration. This paper presents a study investigating seated subjects’ perception of construction induced groundborne vibration in the vertical direction with the method of multidimensional scaling. The investigation was conducted using a paired comparison subjective test. Sixteen subjects were asked about their perception of the annoyance and similarity of sixty-six pairs of vibration stimuli. Through non-metric multidimensional scaling analysis, it is presented that the perception of construction vibration activities are dependent on up to three perceptual dimensions: duration of the signal, vibration energy in the 31.5 Hz of ⅓ octave band, and the centre of mass of the frequency spectrum of the signals. A regression model was built from the relationship between the annoyance ratings and the objective descriptors revealed through the multidimensional scaling analysis. This model was found to describe 79% of the variance in the measured perceived annoyance ratings data with p-level < 0.01.

Efficiency of Open and Infill Trenches in Mitigating Ground-Borne Vibrations

AbstractIn the present-day context, man-made sources of ground-borne vibration are rising at a very rapid rate due to increasing construction work, blasting activities, and rapidly expanding rail a...

Engineered metabarrier as shield from longitudinal waves: band gap properties and optimization mechanisms

Phononic crystals that prevent the propagation of waves in a band gap have been widely applied in wave propagation control. In this paper, we propose the use of a metabarrier, based on a locally resonant phononic crystal mechanism, as a floating-slab track bearing to shield the infrastructure in a floating-slab track system from longitudinal waves from the slab, thereby improving mitigation of ground-borne vibrations. The locally resonant band gap properties of the metabarrier were studied based on the finite element method, and the shielding performance was verified by the transmission spectrum. Simplified models for band gap boundary frequencies were built according to the wave modes. Furthermore, a 3D half-track model was built to investigate the overall vibration mitigation performance of the floating-slab track with the metabarrier. An optimization mechanism for the band gap boundary frequencies is proposed. As the low-frequency ground-borne vibrations induced by subways carry the most energy, multi-objective genetic algorithm optimization was conducted to obtain a lower and wider band gap for a better shielding performance. The results show that the retained vibration isolation performance of the low natural frequency, the shielding performance of the band gap, and the controllability of band gap boundary frequencies all contribute to an improvement in overall vibration mitigation performance. The vertical static stiffness of the metabarrier was close to that of the existing bearing of the floating-slab track. An optimized locally resonant band gap from 50 to 113 Hz was generated using the optimization mechanism.

Theoretical investigation into the formation mechanism and mitigation measures of short pitch rail corrugation in resilient tracks of metros

Severe rail corrugation occurs at both the curved and tangent tracks of the metro in Shanghai, where resilient rail fasteners are used to reduce ground-borne vibration by isolating the transmission of track vibration to the infrastructure. The wavelength of corrugation is about 25–30 mm. It could be assumed that this short pitch rail corrugation is caused by the pinned–pinned resonance. However, rail fasteners with low stiffness were believed to be able to suppress the pinned–pinned resonance thereby resulting in corrugation. To investigate the formation mechanism of this specific rail corrugation, a multiple wheel–rail interaction model is used to calculate the wheel–rail dynamic forces caused due to the multiple wheel–rail interactions, which are considered to play a major role in the formation of corrugation. Then the influences on wear and corrugation growth are analyzed in terms of both amplitude and phase of the wheel–rail dynamic forces. By combining the properties of multiple wheel–rail interactions with their influences on wear and corrugation, the growth rates of rail corrugation at different wavelengths (frequencies) are studied to obtain the characteristic wavelength (frequency), at which the highest corrugation growth rate appears. The obtained characteristic wavelength is in good agreement with observation in the practice of Shanghai metro. It is found that the wave reflection from the wheels on the rail is responsible for the short pitch rail corrugation in the resilient tracks. Finally, tuned rail dampers are applied in the multiple wheel–rail interaction models to investigate their effects on rail corrugation growth. The simulation results show that use of tuned rail dampers is effective in suppressing the short pitch rail corrugation occurring at resilient tracks.

Dynamic Analysis of an Office Building due to Vibration from Road Construction Activities

Construction activities are widely known as one of the predominant sources of man-made vibrations that able to create nuisance towards any adjacent building, and this includes the road construction operations. Few studies conclude the construction-induced vibration may be harmful directly and indirectly towards the neighbouring building. This lead to the awareness of study the building vibration response of concrete masonry load bearing system and its vibrational performance towards the road construction activities. This study will simulate multi-storey office building of Sekolah Menengah Kebangsaan (SMK) Bandar Enstek at Negeri Sembilan by using finite element vibration analyses. The excitation of transient loads from ground borne vibrations which triggered by the road construction activities are modelled into the building. The vibration response was recorded during in-situ ambient vibration test by using Laser Doppler Vibrometer (LDV), which specifically performed on four different locations. The finite element simulation process was developed in the commercial FEA software ABAQUS. Then, the experimental data was processed and evaluated in MATLAB ModalV to assess the vibration criteria of the floor in building. As a result, the vibration level of floor in building is fall under VC-E curve which was under the maximum permissible level for office building (VC-ISO). The vibration level on floor is acceptable within the limit that have been referred.

A 2.5D finite element and boundary element model for the ground vibration from trains in tunnels and validation using measurement data

A numerical model is presented for the ground-borne vibration produced by trains running in tunnels. The model makes use of the assumption that the geometry and material properties are invariant in the axial direction. It is based on the so-called two-and-a-half dimensional (2.5D) coupled Finite Element and Boundary Element methodology, in which a two-dimensional cross-section is discretised into finite elements and boundary elements and the third dimension is represented by a Fourier transform over wavenumbers. The model is applied to a particular case of a metro line built with a cast-iron tunnel lining. An equivalent continuous model of the tunnel is developed to allow it to be readily implemented in the 2.5D framework. The tunnel structure and the track are modelled using solid and beam finite elements while the ground is modelled using boundary elements. The 2.5D track-tunnel-ground model is coupled with a train consisting of several vehicles, which are represented by multi-body models. The response caused by the passage of a train is calculated as the sum of the dynamic component, excited by the combined rail and wheel roughness, and the quasi-static component, induced by the constant moving axle loads. Field measurements have been carried out to provide experimental validation of the model. These include measurements of the vibration of the rail, the tunnel invert and the tunnel wall. In addition, simultaneous measurements were made on the ground surface above the tunnel. Rail roughness and track characterisation measurements were also made. The prediction results are compared with measured vibration obtained during train passages, with good agreement.

Groundborne vibration attenuation by particulate dampers to reduce building vibration at sonic frequencies

Particulate medium can act as efficient damper for building vibrations. Mechanical properties of particulate material and their size distributions determine their vibration absorption characteristics. Unconsolidated particulate damper of uniform size is shown to have bandpass filter behavior for mechanical vibrations that are transmitted through them. The dampers absorption spectrum also shows bandgap structure where mechanical vibration in each frequency range is strongly absorbed. We use samples of uniform size spherical particulates that are subjected to mechanical vibrations in the audible frequency range to determine their absorption characteristics as a function of particle size, frequency, intensity, and direction of propagation. The effects of particle sizes and layer thickness on vibration absorption are determined. The goal is to determine the required absorption characteristics as a function of particle size distribution, that is required to mitigate building vibrations.

The influence of pore-fluid in the soil on ground vibrations from a tunnel embedded in a layered half-space

A computationally efficient semi-analytical solution for ground-borne vibrations from underground railways is proposed and used to investigate the influence of hydraulic boundary conditions at the scattering surfaces and the moving ground water table on ground vibrations. The arrangement of a dry soil layer with varying thickness resting on a saturated poroelastic half-space, which includes a circular tunnel subject to a harmonic load at the tunnel invert, creates the scenario of a moving water table for research purposes in this paper. The tunnel is modelled as a hollow cylinder, which is made of viscoelastic material and buried in the half-space below the ground water table. The wave field in the dry soil layer consists of up-going and down-going waves while the wave field in the tunnel wall consists of outgoing and regular cylindrical waves. The complete solution for the saturated half-space with a cylindrical hole is composed of down-going plane waves and outgoing cylindrical waves. By adopting traction-free boundary conditions on the ground surface and continuity conditions at the interfaces of the two soil layers and of the tunnel and the surrounding soil, a set of algebraic equations can be obtained and solved in the transformed domain. Numerical results show that the moving ground water table can cause an uncertainty of up to 20 dB for surface vibrations.

The effect of ground borne vibrations from high speed train on overhead line equipment (OHLE) structure considering soil-structure interaction

At present, railway infrastructure experiences harsh environments and aggressive loading conditions from increased traffic and load demands. Ground borne vibration has become one of these environmental challenges. Overhead line equipment (OHLE) provides electric power to the train and is, for one or two tracks, normally supported by cantilever masts. A cantilever mast, which is made of H-section steel, is slender and has a poor dynamic behaviour by nature. It can be seen from the literature that ground borne vibrations cause annoyance to people in surrounding areas especially in buildings. Nonetheless, mast structures, which are located nearest and alongside the railway track, have not been fully studied in terms of their dynamic behaviour. This paper presents the effects of ground borne vibrations generated by high speed trains on cantilever masts and contact wire located alongside railway tracks. Ground borne vibration velocities at various train speeds, from 100 km/h to 300 km/h, are considered based on the consideration of semi-empirical models for predicting low frequency vibration on ground. A three-dimensional mast structure with varying soil stiffness is made using a finite element model. The displacement measured is located at the end of cantilever mast which is the position of contact wire. The construction tolerance of contact stagger is used as an allowable movement of contact wire in transverse direction. The results show that the effect of vibration velocity from train on the transverse direction of mast structure is greater than that on the longitudinal direction. Moreover, the results obtained indicate that the ground bourn vibrations caused by high speed train are not strong enough to cause damage to the contact wire. The outcome of this study will help engineers improve the design standard of cantilever mast considering the effect of ground borne vibration as preliminary parameter for construction tolerances.

Suppression of Ground Borne Vibration Induced by High-Speed Lines

Vibration of high-speed lines leads to annoyance of public and lowering real estate values near the railway lines. This hinders the development of railway infrastructures in urbanised areas. This paper investigates the vibration response of an isolated rail embankment system and modifies the component to better attenuate ground vibration. Mainly velocity response is used to compare the responses and the applied force is of 20 kN at excitation frequencies of 5.6 Hz and 8.3 Hz. Focus was made on ground-borne vibration and between the frequency range of 0 and 250 Hz. 3D Numerical model was made using SolidWork software and frequency response was produced using Harmonic Analysis module from ANSYS Workbench software. For analytical modelling MATLAB was used along with Simulink to verify the mathematical model. This paper also compares the vibration velocity decibels (VdB) of analytical two-degree of freedom model mathematical model with literature data. Harmonic excitation is used on the track to simulate the moving load of train. The results showed that modified analytical model gives the velocity response of 75 VdB at the maximum peak. Changes brought to the mass and spacing of the sleeper and to the thickness and the corresponding stiffness for the ballast does not result in significant vibration response. Limitations of two-degree analytical model is suspected to be the cause of this inactivity. But resonance vibration can be reduced with the aid of damping coefficient of rail pad. Statistical analysis methods t-test and ANOVA single factor test was used verify the values with 95% confidence.

The influence of uncertain local subsoil conditions on the response of buildings to ground vibration

This paper examines the influence of imperfect knowledge of the local subsoil conditions on the prediction of building response to ground-borne vibration. The focus is on problems of environmental ground vibration in the wide frequency range between 1 Hz and 80 Hz. A probabilistic finite element-perfectly matched layers model is developed for the analysis of the dynamic soil-structure interaction problem where the shear modulus of the soil is modeled as a conditional random field. A subdomain formulation is employed to impose loading by an incident wave field in the model. The uncertainty on the subsoil properties is propagated to the response of a building by means of Monte Carlo simulation. A case study is considered to investigate the influence of the spatial correlation length of the random field representing the shear modulus of the subsoil, and the foundation type of the building. The structural response uncertainty varies over frequency bands but as a general trend increases with frequency. The foundation type of the building is a crucial parameter determining the structural response and the associated uncertainty bounds.

A track model for railway-induced ground vibration resulting from a transition zone

Accurate computational models are required to predict the ground-borne vibration caused by railway traffic. Since these models generally require substantial computational effort, much research is focused on developing computationally efficient methods by either exploiting the regularity of the problem geometry in the direction along the track or by assuming a simplified track structure. This paper presents a track modeling approach based on a wave analysis technique for multi-coupled periodic structures. The track and part of the soil are modeled with finite elements, while a perfectly matched layer absorbs waves that travel in the semi-infinite soil. A case study that investigates a track with a transition zone between the ballasted and the slab track is presented. The track model is verified by comparing it with a periodic track model by using the Floquet transform. The train–track interaction force and the free field vibration are computed for transition zones with gradual and sudden increase in stiffness, respectively. It is found that, at higher train speeds, it is more important to have a more gradual increase in stiffness in the transition zone.

Infrasound blade pass frequency transmissibility measurements inside homes near wind turbines

Penetration of wind turbine blade pass frequencies are compared at different homes and various rooms show how levels change with wind direction and wind speed. Rooms facing turbines exhibited higher penetration compared to basement rooms, indicating air borne transfer paths vs. ground borne vibration. Construction characteristics of different homes are also compared using transmissibility calculations. Older homes exhibited higher transmissibility while newer airtight homes, under certain conditions, had lower transmissibility.