Investigating the effect of using softer rail-pads on ground-borne vibration from underground railways

Li Z., Ma M., Liu K., Jiang B.

Recently, the use of periodic vibration isolation barriers (PVIBs) has emerged as a significant method for attenuating environmental vibrations along the propagation path. Previous studies have indicated that periodic infilled trenches and piles can effectively isolate low-frequency surface waves. However, a considerable number of these periodic structures require full-size shipments or cast-in-place construction, thus increasing the shipment difficulty or construction period. In addition, few experimental studies have reported on the performance of PVIBs under underground excitation. To solve these problems, this study proposes a novel periodic composite rubber-concrete barrier (PCRCB) with prefabricated assembly characteristics. A laboratory test was performed, in which the calculated frequency band gap (FBG) and attenuation zones of the optimised PCRCB were validated under ground-borne and underground hammering excitations. Then, a numerical model was developed to analyse the vibration mitigation effect of the optimised PCRCB considering the metro train loads. The results of the laboratory study demonstrated that the depth of the impact load affects ground vibration attenuation. The optimised PCRCB has been proven to exhibit good vibration isolation performance. The results of the numerical study demonstrate that the vibration mitigation effect of the PCRCB on the ground surface is good under underground metro train loads. The insertion loss (IL) increases, but its value is less than 2 dB, with the ratio of burial depth to tunnel base depth increases from 1 to 2 times. Accordingly, the ratio of the burial depth to the tunnel base depth is recommended to be 1 in the vibration isolation project of an underground metro train.

Sanitate G., Talbot J.P.

As new buildings are constructed to accommodate the growing urban population, there is increasing use of sites close to both surface and underground railways. An important design consideration concerns the internal levels of perceptible vibration and re-radiated noise, which may have a negative impact on both the quality of life of occupants and the functioning of sensitive equipment. When considering this vibration serviceability, noise and vibration predictions are often made based on initial measurements of the free-field ground vibration, and by applying empirical relations available in the literature. Coupling loss, floor-to-floor and column-to-floor factors are all defined on the basis of data collected from a limited range of pre-existing buildings, and yet they are applied in practice on a wide range of soil-foundation-building systems. This paper presents the findings of a ground-borne vibration measurement campaign conducted during the construction of a 17-storey building above the Bakerloo line of the London Underground. Vibration levels are compared as the construction progresses over a two-year period, from the original brown-field site to the completion of the building, with the aim of identifying the so-called added-foundation and added-building effects. These effects, which refer to the attenuation or amplification of ground vibration levels resulting from the construction, are quantified in terms of coupling losses that are conceptually different from those found in vibration assessment procedures. Further results describing the variation in vibration levels within the completed building are compared with guideline values and their significance in a design context is discussed. • Ground-borne vibration measurements from a tall building above London Underground. • Measurements throughout construction highlight changes due to foundation and building. • Floor-to-floor measurements indicate vibration attenuation with height. • Core-to-floor measurements indicate resonant amplification. • Installation of façade highlights damping effect of non-structural elements.

Qu S., Zhao L., Yang J., Wu Z., Zhu S., Zhai W.

The construction of the underground section of the Chengdu-Zigong High-speed Railway, the fastest underground railway worldwide with a design speed of 350 km/h, has attracted extensive attention in the transportation and environment communities because it passes through many areas with vibration-sensitive equipment. In this context, an in-situ wheelset-dropping experiment is conducted in the high-speed railway tunnel to probe the vibration transfer characteristics of the tunnel-soil system. Further, an elaborate spatial dynamics model is built based on a hybrid time-frequency domain method to explore the feasibility of an engineered metabarrier for mitigating the ground vibration induced by underground high-speed trains from the perspective of numerical analysis. The bandgap characteristics of the metabarrier and the sensitivity of ground vibration attenuation rate to metabarrier depth are revealed. The results show that the horizontal vibrations cannot be ignored, the metabarrier can effectively suppress the ground vibration at 29.11–80.74 Hz, and the ground vibration attenuation rate first increases and then tends to be stable with the increasing metabarrier depth. The in-situ excitation test fills the experimental gap in the field of environmental vibration caused by underground high-speed trains and the research on the application of metabarrier provides fresh insights for preventing railway induced vibration, specifically in studies where metabarriers are considered as mitigation measures. • An in-situ excitation experiment was carried out inside high-speed railway tunnel. • An elaborate spatial dynamics model was built to calculate the three-dimensional responses of the system. • An engineered metabarrier was adopted to suppresses underground high-speed train induced vibration. • The sensitivity of ground vibration attenuation rate to metabarrier depths were revealed.

Esmaeili Moghadam A., Rafiee-Dehkharghani R.

This paper aims to design optimal inclined wave barriers for screening vibrations in homogeneous and layered grounds with different groundwater table levels. The wave propagation phenomenon in the dry and saturated layered half-space is modeled using finite element numerical simulations considering elastodynamic and Biot's poroelastodynamic theories in dry and saturated layers, respectively. The inclined barriers' geometry and position are optimized using Covariance Matrix Adaption Evolution Strategy (CMA-ES), in which the finite element simulations are incorporated to find the fitness function. The studied grounds are subjected to dynamic loadings with different frequencies, and they are considered to have single or multiple layers with different groundwater levels. It is observed that the barriers perform better at larger frequencies and tend to locate close to the loading area to screen the waves actively. Also, the optimal barriers alleviate the environmental nuisance caused by the ground-borne vibrations significantly. • Vibration mitigation using wave barriers at different frequencies. • Topology optimization using CMA-ES method coupled with finite element. • Biot's poroelastodynamic theory for modeling wave propagation in saturated media. • Investigating the effects of barrier geometry and inclination angle. • Effect of GWT and optimal barrier differences in dry and saturated grounds.

He C., Zhou S., Guo P.

• A 3D analytical solution is proposed to calculate the dynamic response of multiple inclusions in a layered half-space. • The mitigation of railway-induced vibrations by periodic WIBs is investigated, with soil stratigraphy being considered. • Systematic parametric study on the geometry and material characteristics of the WIBs and layered ground is performed. Railway-induced vibrations can cause significant environmental issues. This paper proposes an efficient analytical method to investigate the mitigation of railway-induced vibrations by using periodic barriers in a layered half-space. The general solutions for layered ground and multiple inclusions are derived by using the potential decomposition and multiple scattering theory. The conversion equation between cylindrical and exponential functions and the addition theorem are introduced to achieve the transformation between plane and cylindrical wave functions and the translation between cylindrical wave functions. Combined with the transfer matrix method, the fundamental solution for the soil-inclusion dynamic interaction in a layered half-space is derived. The railway train and track are subsequently coupled to the ground-inclusion system. Numerical results demonstrate that the phononic crystal effect induced by the periodic distribution of barriers improves the mitigation efficiency at high frequencies. The increase in the number, size, and stiffness of barriers can give a higher mitigation efficiency in a wider frequency range. The mitigation efficiency of periodic barriers can be guaranteed when their depth is shorter than half the Rayleigh wavelength in the considered frequency range. Owing to the scattering of waves at layer interfaces, the periodic barriers beneath the track have a higher efficiency than those located next to the track, which does not appear in the homogeneous half-space. The performance of periodic barriers is significantly affected by the soil stiffness of the upper shallow layer, while it is less affected by the soil stiffness of the bottom stiffer layer.

Chen Q., Guo D., Ke W., Xu C., Nimbalkar S.

Lamprea-Pineda A.C., Connolly D.P., Hussein M.F.

Beam on elastic foundation theory is widely employed when studying railway track behaviour, for applications such as track dynamics, and noise and vibration. At a basic level, the use of a single continuous beam resting on a springs-in-series support is straightforward to implement and computationally efficient. However, it can also be extended to simulate the multi-layered and periodic nature of railway tracks, which typically comprise a variety of components. Further, these track models can also be coupled with both vehicle and subgrade models. Therefore, this paper presents a state-of-the-art technical review of beam on elastic foundation theory, including the exploration of recent advancements in the field. Firstly, a variety of modelling strategies and solution methods employed for the computation of track behaviour are reviewed. These include periodic and semi-periodic modelling approaches. Considerations for extending beam on elastic foundation approaches to include train-track interaction and track-ground interaction are then provided. Finally, using the aforementioned theory, benchmark solutions for three common problem types are given: railway noise, railway track dynamics and railway ground-borne vibration.

Ouakka S., Verlinden O., Kouroussis G.

Vibration and noise aspects play a relevant role in the lifetime and comfort of urban areas and their residents. Among the different sources, the one coming from the rail transit system will play a central concern in the following years due to its sustainability. Ground-borne vibration and noise assessment as well as techniques to mitigate them become key elements of the environmental impact and the global enlargement planned for the railway industry. This paper aims to describe and compare the different mitigation systems existing and reported in literature through a comprehensive state of the art analysis providing the performance of each measure. First, an introduction to the ground-borne vibration and noise generated from the wheel-rail contact and its propagation through the transmission path is presented. Then, the impact and the different ways of evaluating and assessing these effects are presented, and the insertion loss indicator is introduced. Next, the different mitigation measures at different levels (vehicle, track, transmission path and receiver) are discussed by describing their possible application and their efficiency in terms of insertion loss. Finally, a summary with inputs of how it is possible to address the future of mitigation systems is reported.

Arcos R., Soares P.J., Alves Costa P., Godinho L.

A novel experimental/numerical hybrid methodology for the assessment of railway-induced ground-borne vibration in buildings based on experimental measurements in the soil surface is proposed in this paper. This methodology has been specifically designed for the prediction of railway-induced vibration in buildings to be constructed close to an operative railway infrastructure, although it can be applied for other types of vibration sources. The model of the incident wave field induced by the railway infrastructure consists of a set of virtual forces applied in the soil, which would be obtained from vibration experimental measurements in the surface of the ground where the building will be constructed. These virtual forces can be subsequently applied to a model of the building-soil system to obtain a prediction of the vibration levels that will be induced by the existing railway infrastructure to the studied building. In the present work, this methodology is theoretically defined and it is numerically validated for two-dimensional and two-and-a-half-dimensional cases. To numerically test the methodology, the measured ground surface responses are replaced by simulated ones obtained in a set of points called collocation points. In this context, a parametric study has been developed with the aim of finding out a robust criterion for the application of the present methodology with respect to the amount and location of the collocation points (representing vibration sensors) and virtual forces. It is found that the distance between virtual sources should be smaller than the S-wave wavelength of the upper soil layer corresponding to the highest frequency of the frequency range of interest to ensure the reliability of the methodology. Moreover, the proposed method is found to be insignificantly affected by the building-tunnel dynamic coupling for building-tunnel distances above 20 m. The proposed hybrid model would simplify the usual numerical prediction approach commonly adopted for dealing in detail with these problems, since a model of the railway infrastructure is no longer required. Moreover, it would reduce the uncertainty of the prediction due to the use of experimental measurements of the particular site to be studied. In addition, it would provide a higher accuracy and flexibility than empirical models based on experimental transmissibility functions between the soil surface and the building. • A method for the prediction of railway-induced vibration in buildings is presented. • The prediction is done in building prior to its construction. • The method is hybrid, combining experimental data with a numerical model. • The method has been numerically validated at various case studies. • Guidelines for the practical application of the method are established.

Liang R., Liu W., Ma M., Liu W.

The uncertainty in the prediction of train-induced ground-borne vibration is mainly attributed to the randomness of excitation, the variability of soil, the uncertainty of models, etc. Quantification of the uncertainty in prediction is an intractable problem using traditional models. Herein, an efficient model based on the Bayesian neural network is presented to predict the train-induced ground-borne vibration and quantify the uncertainty. In this model, vibration prediction is performed using a probabilistic framework. The aleatoric uncertainty is quantified by assuming a Gaussian noise over the observation data of vibration level, and the epistemic uncertainty is quantified by delivering the posterior of the fitting parameters in the model using Bayesian inference. In addition to the mean value of prediction, the model can provide a probability distribution to describe the uncertainty in prediction. A case study is presented in which both the weighted vibration level and the frequency-dependent vibration level are predicted. The proposed model performed well about the prediction accuracy and uncertainty estimation, as indicated by a comparison of the results with previously published measurements.

Li C., Liu W.

The environmental vibration caused by the metro trains has remarkable uncertainties due to some uncertain parameters in the source and propagation path of the vibration. Based on the complex principal component analysis, a probabilistic prediction approach is presented to quantify the uncertainty of the wheel-rail force, which can be used to predict the ground-borne vibration in the probabilistic framework. Furthermore, an evaluation index is proposed to quantify the accuracy of the predicted results. This index can be used to consider not only the bias between the predicted and measured results but also their respective uncertainties. A case study is made to validate the probabilistic prediction procedure and the evaluation of the prediction accuracy. The results show that the predicted and measured vibration levels have good agreement, and the evaluation index can effectively quantify the prediction accuracy at frequencies in one-third octave band. • A probabilistic method is proposed in frequency domain to quantify the train loads. • Probabilistic prediction of the metro induced ground-borne vibration is realized. • A distribution-oriented index is presented to evaluate the prediction accuracy.

Khalil A.A., Metwally K.G., Ahmed N.Z.

The principal aim of this paper is to analyze the impact of rubber pad systems on levels of vibrations and values of stresses and deformations induced in the subway tunnel segments. Thus, the 3D model has been selected to be isotropically simulated in the ANSYS program to conduct a finite element analysis. Therefore, the proposed track system in the tunnel of line 4 of the Greater Cairo Metro has been selected as an analytical and simulation case study. The impact of using eight different values for the stiffness of the rubber pad system in the case of a single tunnel has been analyzed. The results showed that levels of vibrations are significantly affected and are in logarithmic correlation with the stiffness. Also, the impact of the stiffness on the deformations and stresses are determined as well as mathematical models connecting the different parameters have been introduced.

Heidary R., Esmaeili M., Gharouni Nik M.

Many underground railway lines consist of twin tunnels. The accurate prediction of ground-borne vibration levels is thus essential for this situation. This study investigates the train’s axle load ...

Kedia N.K., Kumar A.

Rapid increase in urban population in India put a lot of pressure on existing transportation systems which results in frequent traffic jams, congestion, and delay. To overcome this problem, governments propose construction of underground metro systems in various cities some of which are either operational or in construction phase. Metro has proved to be safe and efficient mode of transportation in cities. However, passage of trains at certain speed produces vibrations which are uncomfortable and annoying to the people living near the vicinity of the metro systems. In addition to the human annoyance, these vibrations can affect old buildings and sensitive equipment. This paper reviews various vibration issues that are generated due to wheel-track interaction and tunnel-soil interaction in India and other countries. Moreover, track-based countermeasures and ground improvement techniques are summarized and compared. Nonetheless, some issues in numerical modeling of these systems are also discussed.

Thompson D.J., Kouroussis G., Ntotsios E.

There is a great need to develop rail networks over long distances and within cities as more sustainable transport options. However, noise and vibration are seen as a negative environmental consequ...

Bai Y., He Z., Qu S., Li B., Zhai W.

The lateral stiffness and damping of rail pads significantly influence train performance on curves, yet their effects are not well understood. This study investigates the lateral dynamics of three rail pad structures: groove (GRP), mesh-type (MTRP), and mesh-type with high damping (MTHDRP), and their impact on train curve performance. Results from lateral loading tests indicate that MTHDRP pads exhibit the highest lateral static stiffness, dynamic stiffness, and damping ratio, while GRP pads have the lowest, highlighting significant performance disparities. Finite element analysis reveals substantial deformations in GRP pads under high lateral loads, leading to increased stress levels. Strategies to increase the lateral stiffness across these pad types involve structural parameter adjustment and integration of harder materials, detailed further in the conclusions. Multibody dynamic simulations suggest that decreasing lateral stiffness while increasing damping not only increases train safety on curves but also reduces track system vibration. Under varying conditions of speed, curve radius, rail slope, and superelevation, MTHDRP consistently demonstrates favorable performance, underscoring the importance of lateral dynamics in the design, manufacturing, testing, and dynamic analysis of rail pads to optimize vehicle and track performance on curves.

Luo W., Deng S.

Bai Y., He Z., Li P., Li B.

Ren Y., Li Q., Qu S., Yang J., Luo W., Zhu S., Zhai W.