Train-induced Ground Vibrations Research Articles

Discrete mass modeling for dynamic response of buildings in the vicinity of railway tracks due to train-induced ground vibrations

Annoying vibration waves generated by passing trains highlight the necessity for the assessment of the eff ects of railways on their environment. Dynamics of structures close to railway tracks is amongst such important issues. Contrary to the past studies, this article proposes a modeling method that is totally based on the idea of discrete masses. It considers three major parts as the accomplices causing undesirable oscillations including the track, the ground bed, and the structure in the vicinity of the track. The ground bed is considered as an elastic half space subdivided into discrete masses. It facilitates modeling for the track systems that may include any deliberate discontinuity, such as voids and trenches, in the ground bed that supports the railway track. Such discontinuities arise from engineering perception and are useful in controlling the spread of noise and vibrations. A MATLAB based computer program is written to solve the motion equations in the timedomain. The proposed method provides flexibility in modeling. Variety of track loading and wave propagation scenarios can be simulated without the need to rebuild the model. This method can be practically used when seeking remedies for controlling the levels of unwanted vibrations in the structures.

Emission of Train-Induced Ground Vibration - Prediction of Axle-Load Spectra and its Experimental Verification

Train passages induce forces on the track, train-induced vibrations propagate through the soil and excite neighbouring buildings. The emission, which is the first part of the prediction of vibrations near railway lines, is presented by focusing on the dynamic axle loads. The calculation of the axle loads is based on the vehicle-track-soil interaction. This interaction calculus utilises the dynamic stiffness of the vehicle (the inertia of the wheelset) and the dynamic stiffness of the track-soil system. Based on various time consuming finite-element boundary-element calculations, an approximate track-soil model has been established. The vehicle-track-soil analysis yields several transfer functions between the various geometric or stiffness irregularities and the axle loads of the train. Geometric irregularities of the vehicle (the wheels) and the track (rail surface and track alignment) are the simplest components. Geometric irregularities of the subsoil (trackbed irregularities) have to be transferred to effective irregularities at rail level. The bending stiffness of the track is filtering out the short-wavelength contribution. Stiffness irregularities occur due to random variations in the ballast or the subsoil, which must also be transferred to effective track irregularities, and due to the discrete rail support on sleepers. All necessary transfer functions for the prediction of axle-load spectra are presented as general formula and as specific graphs for differing vehicle and track parameters. The prediction method is applied to a ballast track and a slab track and compared with corresponding axle-box measurements. Moreover, ground vibration measurements at numerous sites are exploited for the axle-load spectra and the validation of the prediction method. All theoretical and experimental results confirm that the dynamic axle-load spectra have an approximate value of 1 kN per third of octave and increase with train speed, track stiffness and around the vehicle-track resonance.

Measurements on the Vehicle-Track Interaction and the Excitation of Railway-Induced Ground Vibration

Two railway measurement campaigns have been performed in Germany and Switzerland which yield insight in the vehicle-track-soil interaction. The campaign in Germany has included simultaneous measurement of vehicle, track, and soil vibrations during train runs with 16, 25, 40, 63, 80, 100, 125, 140, 160 km/h, and impulse measurements of the passenger car, three track sections and the soil. Two ballast tracks, one on the soil surface and one on a concrete bridge, have been investigated as well as a slab track in a tunnel. Ten different sites in Switzerland have been measured for soil properties and train-induced ground vibrations, which allow to determine the excitation forces of the railway traffic. New axle-box measurements at some of the Swiss sites have been analysed to get further experimental evidence. All these measurements have been evaluated to characterize the excitation processes. Relations between vehicle vibration and ground vibration can be observed. The vehicle vibrations, namely the accelerations of the wheelsets, yield the dynamic forces due to the passage over the irregularities of the vehicle and the track. The ground vibrations are correlated to these dynamic forces to a certain extent. Some mid-frequency ground vibration amplitudes, however, are higher than expected from the dynamic excitation forces. The experimental observations can be explained by an irregular response to the passage of the static loads, that means the passage of the static loads over an irregular ballast or soil. This correct understanding of the excitation processes is important for the prediction as well as for the mitigation of railway induced ground vibrations.

A Laboratory Test on the Vibration Mitigation Efficiency of Floating Ladder Tracks

With the rapid development of railway systems, increasingly more environmental concerns are focused on railway vibrations. The track solution with the mass-spring-damping principle can be the most effective and economical option to control train-induced ground vibrations. The effect of track vibration mitigation is usually described by insertion loss (IL). IL can typically be obtained by impulse tests in laboratories. To investigate the influences of preloads on IL, a dynamic laboratory experiment was performed on a floating ladder track. Two conditions were considered, a ladder sleeper with and without under sleeper pads (USPs). A modal test was performed, and then, an automatic falling weight system was used for the vibration reduction test. A preloaded car with a deadweight of 2.4 tons was employed. Different concrete masses, with a maximum of 5.4 tons of total weight were applied on the car. Ground vibrations and IL were analysed under these different preloaded weights. The results show that the first natural frequency of the floating ladder track was 33 Hz. When the preload was applied, the ground vibration and IL around the natural frequency were largely influenced. In addition, the values of IL in different frequencies had different sensitivities to the preloads.

Using elastic bridge bearings to reduce train-induced ground vibrations: An experimental and numerical study

In order to investigate the influences of elastic bearings on ground vibrations induced by trains traversing a bridge, a numerical model was established based on the combination of train/track/bridge and pier/pile/soil subsystems. The elastic bearings in the train/track/bridge subsystem were simulated by a spring-dashpot element. The two subsystems were linked by the bearing reaction forces, and the whole model was calculated in the time domain. The numerically computed ground vibrations were compared with measured ones to validate the model. On this basis, the influences of elastic bearings on train, bridge and ground responses were discussed. Results show that the dynamic responses of the train are hardly affected, while the dynamic responses at the pier top and on the ground are clearly attenuated in the frequency band above 40Hz. Some increments in the frequency range 8–30Hz can be observed around the eigenfrequency of the main girder-elastic bearing system. The laws of bearing stiffness influences on ground vibrations were similar for different stiffnesses of the elastic bearings. Within a distance of 15m from the bridge, elastic bearings with stiffnesses of 2400, 2000 and 1600MN/m can reduce ground vibrations. However, at locations more than 22.5m from the bridge, ground vibrations may be close to or even a little larger than those of the rigid bearing case. When the elastic bearing has a stiffness of 1200MN/m, ground vibrations are clearly decreased at all locations.

Vibrations of soil and foundation due to railway, blast and impact loading

The vibrations of soil and foundations are demonstrated for different types of loading. Train-induced ground vibrations are studied in a measurement cam­paign where a test train has run with regularly varied speeds. The measured train-induced soil vibration at 2 to 100 m distance from the track is compared with the wave propagation due to hammer excitation and with the theoretical wave field. The strong influence of the soil and the train speed on the amplitudes and frequencies of the vibration has been analysed for passages of the locomotive and the carriages. - The generation of ground vibration by strong explosions has been studied on a large testing area with sandy soil. The propagating waves were measured in a regular grid of measuring points in 10 to 1000 m. Therefore, the dominance of certain waves at certain distances and the changes of compressio­nal waves and Rayleigh waves could clearly be observed. The results are compa­red with impulse hammer measurements in the range of 5 to 50 m. - A drop test facility has been built on the testing area of the Federal Institute of Materials Research and Testing (BAM). Heavy masses (containers) of up to 200 t can be dropped from 10 m height on a big reinforced concrete foundation. The founda­tion was instrumented by accelerometers, strain gauges and pressure cells to give information about the loading condition and by geophones to measure the vibra­tion of the surrounding soil and building. Both excitation processes, the release of the mass and the impact, produce high vibration amplitudes. On a smaller drop foundation, the influence of the drop height and the target stiffness has been studied more systematically.

Realistic axle-load spectra from ground vibrations measured near railway lines

Train-induced ground vibrations are generated by static and dynamic axle loads which can be calculated by vehicle-track-soil models and the vehicle and track irregularities. A fast prediction method has been developed which uses approximate transfer functions of layered soils. In the present contribution, this prediction method is used for the inverse calculation of the axle-load spectra from the measured ground vibration. The layered soils of some measuring sites show very differing ground vibration spectra in the amplitude range of 0.0001–1.0 mm/s as a consequence of the soft layer and stiff half-space, differing layer frequencies, as well as the far- and near-field measuring points. The back-calculation, however, yields axle-load spectra within a single order of magnitude around 1 kN. Axle-box measurements confirm the amplitude level of the axle loads. This standard axle-load spectrum can be used for a basic prediction at a new site. The separation of train and site-specific components allows a better evaluation of railway vibrations, for example, of different trains and different tracks. By eliminating the effects of differing soil characteristics, an important mid-frequency component has been found which lies between 8 and 32 Hz depending on the train speed. The origin of this dominant mid-frequency component is discussed using advanced prediction methods like moving constant loads, scattered axle impulses and axle-sequence spectra.

Experimental investigation into ground vibrations induced by very high speed trains on a non-ballasted track

A field measurement of ground vibration was performed on the Beijing−Shanghai high-speed railway in China. In this paper, the experimental results of vertical ground vibration accelerations induced by very high speed trains running over a non-ballasted track on embankment with speeds from 300 to 410km/h are reported and analyzed in detail for the first time. Characteristics of ground vibration accelerations in both time and frequency domains are analyzed based on the test data. It is shown that the periodic exciting action of high-speed train bogies can be identified in time histories of vertical accelerations of the ground within the range of 50m from the track centerline. The first dominant sensitive frequency of the ground vibration acceleration results from the wheelbase of the bogie, and the center distance of two neighboring cars plays an important role in the significant frequencies of the ground vibration acceleration. Variations of time–response peak value and frequency-weighted vertical acceleration level of ground vibration in relation with train speed as well as the distance from the track centerline are also investigated. Results show that the time-domain peak value of ground vibration acceleration exhibits an approximately linear upward tendency with the increase of train speed. With the increasing distance from the track centerline, the frequency-weighted vertical acceleration level of the ground vibration attenuates more slowly than the time-domain peak value of the ground vibration acceleration does. Severe impact of high-speed railway ground vibration on human body comfort on the ground occurs at the speed of 380–400km/h. The results given in the paper are also valuable for validating the numerical prediction of train induced ground vibrations.

Excitation of ground vibration due to the passage of trains over a track with trackbed irregularities and a varying support stiffness

Train-induced ground vibration can be excited by wheel and track irregularities and by two kinds of irregularities of the soil, by geometric irregularities or by the spatially varying soil stiffness. For both types of irregularities, the effective track irregularity on top of the track is calculated in wavenumber domain and with wavenumber integrals. For a general multi-beam track model, the wavenumber integrals are solved numerically. The irregularities of the soil are filtered by the track when transferred from the bottom to the top of the track. The high-wavenumber irregularities are strongly reduced due to the bending stiffness of the track and the compliance of the support. In addition, soft track elements reduce directly the stiffness variation of the support. Therefore, the mitigation effect of elastic track elements for these excitation components seems to be important. For under-sleeper pads and slab tracks, calculation and measurements are presented including additional excitation components and the dynamic vehicle–track interaction, and the relevance of the excitation mechanisms is discussed based on the dynamic forces which are acting on the ground. Due to the restricted amplitudes, the parametric excitation by the stiffness variation seems to be less important than the geometric irregularities. The calculations yield the correct trends of the measurements and many details of the measured ballast, slab, and under-sleeper-pad tracks.

A Comparative Study on Road Traffic and Metro Train Induced Ground Vibration at CMTI for Establishment of Nano Technology Facilities

Nanotechnology offers enormous potential for discovering new fundamental science, for creating new materials with unique and important properties, and for developing new technology. Nanotechnology deals with particles and system with dimensions of approximately 1 to 100 nanometers. Some aspects of nanomanufacturing technology facilities like nanofabrication, nanometrology requires extremely stable environment with very stringent limits of ground vibration. The ground vibrations induced due to road and rail traffic can affect the nanotechnology research activities, due to disturbances caused by the road and rail traffic induced ground vibrations on the nanotechnology processes and the measurements. The paper presents the study of road traffic and metro train induced ground vibration for establishment of nanomanufacturing technology facilities at CMTI. The road traffic and the metro train induced ground vibration were monitored inside the CMTI campus at surface level to identify the magnitude of ground vibration. The road traffic and the metro train induced ground vibrations are compared in comparison with the CMTI Nanotechnology Lab specifications. The metro train induced ground vibration levels are more in comparison to the road traffic induced ground vibration. The metro train induced ground vibration level exceeds the CMTI Nanotechnology Laboratory ground vibration specifications.

Reduction of Train-induced Vibrations by using Barriers

The problem of the ground-borne vibration caused by high speed trains has received considerable attention in recent years, due to the effects of vibration on buildings, in terms of physical damage and on population, in terms of discomfort. The problem has become more significant with the increase of speed and weight of trains, which results in heavier loads on the tracks. Therefore, there is the necessity to find a method, which allows investigating the propagation of vibration waves in the soil. This study aims to study the train-induced ground vibration and the mitigation effects of barriers using a Finite Element Method (FEM) model. Two different types of barriers were evaluated considering their stiffness and a benchmark model without mitigation measures was also analyzed to evaluate the effectiveness of the considered barriers. The results of the proposed elaborations have been finalized to the assessment of the incidence of the barrier on the vibration state induced from the passage of a high speed trains and the following conclusions can be made: concrete seems to provide a significative reduction of the vibration. The proposed method can be successfully applied to a preliminary analysis of the influence of different types of barriers on the dynamic properties of vibration waves in the soil.

Performance Analysis of Multiple Trenches in Train-Induced Wave Mitigation

The trains passing on the railway tracks produce excessive vibrations normally propagating in the form of Rayleigh waves. Application of multiple trenches in train-induced ground vibration mitigation is studied in this paper. Ground is modeled employing the finite element method (FEM) and the train loading is simulated by series of successive moving loads. Validity of the FE model is then verified using the available experimental data in the literature. A comprehensive parametric study is then carried out and dynamic performance of the trenches is evaluated in range of high-speed operations. Effects of different parameters including the train speed and trench configurations and locations, on the vibration mitigation levels(VML) are investigated.

The Use and Validation of Measured, Theoretical, and Approximate Point-Load Solutions for the Prediction of Train\cbox{-}Induced Vibration in Homogeneous and Inhomogeneous Soils

The layered soil is calculated in the frequency wavenumber domain and the solutions for fixed or moving point or track loads follow as wavenumber integrals. The resulting point load solutions can be approximated by simple formula. Measurements yield the specific soil parameters for the theoretical or approximate solutions, but they can also directly provide the point-load solution (the transfer function of that site). A prediction method for the train-induced ground vibration has been developed, based on one of these site-specific transfer functions. The ground vibrations strongly depend on the regular and irregular inhomogeneity of the soil. The regular layering of the soil yields a cut-on and a resonance phenomenon, while the irregular inhomogeneity seems to be important for high-speed trains. The attenuations with the distance of the ground vibration, due to point-like excitations such as vibrator, hammer, or train-track excitations, were investigated and compared. All theoretical results were compared with measurements at conventional and high-speed railway lines, validating the approximate prediction method.

Force and ground vibration reduction of railway tracks with elastic elements

The reduction of train-induced ground vibration by elastic elements such as rail pads and sleeper pads has been analyzed by a combined finite-element boundary-element method. The dynamic compliance of the track, the transfer function of the total force on the ground and the ground vibration ratios have been calculated for a variety of isolated and un-isolated track systems. It has been found that the soil force transfer, which describes the excitation force of the soil, is an appropriate quantity to predict the reduction of the ground vibration and the effectiveness of isolated tracks. All force transfer functions of isolated tracks display a vehicle–track resonance where the wheelset on the compliant track is excited by wheel and track irregularities. At higher frequencies, considerable reductions of the amplitudes are observed as the benefit of the resilient element. The influence of the stiffness of the rail or sleeper pads, the ballast and the soil, and the mass of the sleeper and the wheelset on the resonance frequency and the reduction has been investigated. Sleeper pads are advantageous due to the higher mass that is elastically supported compared to the rail-pad track system. The combination of elastic rail and sleeper pads has been found to be disadvantageous, as the second resonance occurs in the frequency range of intended reduction.

Mitigation of Ground Vibration Generated by High-Speed Trains on Saturated Poroelastic Ground with Under-Sleeper Pads

Train-induced track and ground vibrations accelerate the deterioration of track, cause nuisance to nearby residents, and even damage adjacent structures. Past research has shown that under-sleeper pads (USPs) are effective at improving track performance and insulating ground vibrations generated by moving trains. The present study was the first to investigate the effectiveness of USP at reducing train-induced ground vibrations at both subcritical and supercritical train speeds (critical speed is defined as the Rayleigh wave speed of the ground surface) and was the first to study the effectiveness of USP at reducing ground vibrations with a two-phase poroelastic soil model. A vehicle-track-ground model containing a fully saturated poroelastic half-space was established, and the whole system was solved by a semianalytical method using Fourier transforms and Fourier series. The differences in the performance of the USPs on saturated poroelastic ground and single-phase elastic ground were examined. It was found that the USPs effectively reduced free-field ground vibrations at subcritical train speeds, but the USP insulation effectiveness was minimized at supercritical train speeds. USPs might also reduce excess pore water pressure in the ground during the passage of a train.

The Dividing Frequency Bands Prediction Method Based on Bornitz Model for Train-Induced Environmental Vibration and its Application

The frequency component of ground vibration induced by train is complex. The propagating attenuation characteristics of ground vibration are dependent on frequency. A new prediction method based on Bornitz model for predicting the train-induced ground vibration is presented in this paper. This approach divides the frequency component into many small frequency bands according to one-third-octave. Then it predicts the vibration acceleration level VAL of each frequency bands based on Bornitz model respectively. Finally, the predicted value of Z-vibration level VLZ is computed by the predicted value of VAL and the corresponding frequency-weighting value C. The traininduced ground vibration was measured and predicted in Chengdu-Dujiangyan railway. The results of comparing the predicted value of VLZ with the measured value show that the prediction value of VLZ is 3.8dB less than the measured value in the prediction point of 25m away from the railway, where the vibration strength occur rebound. In other five prediction points the ground vibration predicted value are 1.3~3.1dB more than measured value. This study shows that using the prediction method presented in this paper for predicting train-induced ground vibration has good accuracy on the whole.

Investigating the Optimized Open V-Shaped Trench Performance in Reduction of Train-Induced Ground Vibrations

An effective strategy in reducing train-induced vibrations on neighboring structures is to use open trenches on both sides of the railway lines. This paper investigates the effect of the trench’s shape on its performance. For this purpose, a V-shaped trench was first modeled using finite-element code, and its efficiency was confirmed in reducing the induced vibrations caused by passing the MD36 passenger bogie in comparison with a rectangular-shaped trench. In this regard, results indicate that the maximum values of the amplitude reduction ratio (Ar) for the ground displacement before the V-shaped trench for train speeds of 80 and 120 km/h were 1.17 and 1.28, respectively, which were less than the value of 2 obtained for the rectangular trench. In the final stage, an optimization algorithm was used to present the procedure of calculating optimized shape of the proposed V-shaped trench for various train speeds.

Non-linear 2-D FE modeling for prediction of screening performance of thin-walled trench barriers in mitigation of train-induced ground vibrations

The installation of the trench-type barriers can be commonly used in civil engineering applications for isolation of the foundations and structures from the soft ground transmitted vibrations induced by high-speed surface railway traffic. The aim of this study is to primarily deal with the numerical modeling and computation of the structural response to train-induced ground-borne vibrations. This paper concentrates on the non-linear 2-D finite element model that fully takes into account the effect of local plastic deformation of the soil behavior on the dynamic response of vibrating coupled soil–structure system. Elementary viscous artificial boundaries simulating the process of wave transmission along the truncated interface of the semi-infinite space are implemented in the time domain along with Newmark’s integration. This computational model combined with simulation of the passing train load considers completely the dynamic soil–structure interaction and directly predicts the mitigation effect on the structural vibrations of the thin-walled isolation measures. Comprehensive parametric investigations for both passive and active screen cases have been accomplished to reveal the influence of its infill material on the isolation efficiency. The respective response spectra of the calculated ground surface motions produced under different train speeds are presented before and after construction of an isolation barrier. The important findings in engineering practice are outlined.

Ground-borne vibrations due to dynamic loadings from moving trains in subway tunnels

In this study, ground vibrations due to dynamic loadings from trains moving in subway tunnels were investigated using a 2.5D finite element model of an underground tunnel and surrounding soil interactions. In our model, wave propagation in the infinitely extended ground is dealt with using a simple, yet efficient gradually damped artificial boundary. Based on the assumption of invariant geometry and material distribution in the tunnel’s direction, the Fourier transform of the spatial dimension in this direction is applied to represent the waves in terms of the wave-number. Finite element discretization is employed in the cross-section perpendicular to the tunnel direction and the governing equations are solved for every discrete wave-number. The 3D ground responses are calculated from the wave-number expansion by employing the inverse Fourier transform. The accuracy of the proposed analysis method is verified by a semi-analytical solution of a rectangular load moving inside a soil stratum. A case study of subway train induced ground vibration is presented and the dependency of wave attenuation at the ground surface on the vibration frequency of the moving load is discussed.

Effects of the trench geometry on vibration mitigation level in high-speed railway tracks

Train-induced ground vibration is numerically analyzed using the finite element method (FEM) in this paper. Varieties of open trenches including partial and full length systems with different geometries are employed as the vibration mitigation strategies. Ground is modeled by multiple soil layers and the train load pattern is simulated by series of successive moving loads. A parametric study is then carried out after verification of the numerical model. Effects of different parameters including the trench type, size and geometry and the train speed on the vibration mitigation level are investigated. The operational speeds are set to be in vicinity of the Rayleigh wave propa- gation velocity. Two types of active and passive trenches are considered with three different geometries consisting of rectangular, trian- gular (wedge) and circular cross sections.