Prediction of high-speed train induced ground vibration based on train-track-ground system model

The development of analysis on train-induced ground vibration is briefly summarized. A train-track- ground integrated dynamic model is introduced in the paper to predict the ground vibration induced by high-speed trains. Representative dynamic responses of the train-track-ground system predicted by the model are presented. Some major results measured from two field tests on the ground vibration induced by two high-speed trains are reported. Numerical prediction with the proposed train-track-ground model is validated by the high-speed train running experiments. Research results show that the wheel/rail dynamic interaction caused by track irregularities has a significant influence on the ground acceleration and little influence on the ground displacement. The main frequencies of the ground vibration induced by high-speed trains are usually below 80 Hz. Compared with the ballasted track, the ballastless track structure can produce much larger train-induced ground vibration at frequencies above 40 Hz. The vertical ground vibration is much larger than the lateral and longitudinal components.

Analysis of ground vibrations due to underground trains by 2.5D finite/infinite element approach

The 2.5D finite/infinite element approach is adopted to study wave propagation problems caused by underground moving trains. The irregularities of the near field, including the tunnel structure and parts of the soil, are modeled by the finite elements, and the wave propagation properties of the far field extending to infinity are modeled by the infinite elements. One particular feature of the 2.5D approach is that it enables the computation of the three-dimensional response of the half-space, taking into account the load-moving effect, using only a two-dimensional profile. Although the 2.5D finite/infinite element approach shows a great advantage in studying the wave propagation caused by moving trains, attention should be given to the calculation aspects, such as the rules for mesh establishment, in order to avoid producing inaccurate or erroneous results. In this paper, some essential points for consideration in analysis are highlighted, along with techniques to enhance the speed of the calculations. All these observations should prove useful in making the 2.5D finite/infinite element approach an effective one.

Prediction and mitigation analysis of ground vibration caused by running high-speed trains on rigid-frame viaducts

In this study a 3D numerical analysis approach is developed to predict the ground vibration around rigid-frame viaducts induced by running high-speed trains. The train-bridge-ground interaction system is divided into two subsystems： the train-bridge interaction and the soil-structure interaction. First, the analytical program to simulate bridge vibration with consideration of train-bridge interaction is developed to obtain the vibration reaction forces at the pier bottoms. The high- speed train is described by a multi-DOFs vibration system and the rigid-frame viaduct is modeled with 3D beam elements. Second, applying these vibration reaction forces as input external excitations, the ground vibration is simulated by using a general-purpose program that includes soil-structure interaction effects. The validity of the analytical procedure is confirmed by comparing analytical and experimental results. The characteristics of high-speed train-induced vibrations, including the location of predominant vibration, are clarified. Based on this information a proposed vibration countermeasure using steel strut and new barrier is found effective in reducing train-induced vibrations and it satisfies environmental vibration requirements. The vibration screening efficiency is evaluated by reduction VAL based on 1/3 octave band spectral analysis.

Analysis of ground vibrations induced by high-speed train moving on pile-supported subgrade using three-dimensional FEM

The pile-supported subgrade has been widely used in high-speed railway construction in China.To investigate the ground vibrations of such composite foundation subjected to moving loads induced by high-speed trains(HSTs),three-dimensional(3D)finite element method(FEM)models involving the pile,pile cap and cushion are established.Validation of the proposed model is conducted through comparison of model predictions with the field measurements.On this basis,ground vibrations generated by HSTs under different train speeds as well as the ground vibration attenuation with the distance away from the track centerline are investigated.In addition,the effects of piles and pile elastic modulus on ground vibrations are well studied.Results show that the pile-reinforcement of the subgrade could significantly contribute to the reduction of ground vibrations.In particular,the increase of elastic modulus of pile could lead to consistent reduction of ground vibrations.However,when the pile elastic modulus is beyond 10 GPa,this benefit of pile-reinforcement on vibration isolation can hardly be increased further.

Assessment of noise and ground vibration induced during blasting operations in an open pit mine——A case study on Ewekoro limestone quarry,Nigeria

Our study was carried out to assess the level of noise generated and ground vibrations induced during blasting operations at the Ewekoro limestone quarry in Nigeria.To achieve this objective,vibro monitor equipment was used to take readings related to noise generated and ground vibrations during all blasting operations that took place in the quarry for a period of one month.As well,a digital camera was used to take photographs of residential structures within villages near the quarry.The results obtained indicate that the ground vibration readings fall between 0.5 mm/s and 2.1 mm/s and the noise generated during the blasting operations between 82 dB and 89 dB.These readings when compared with the limits set by FEPA(Federal Environmental Protection Agency) of 5.0 mm/s and 150 dB) all fall within the permissible limits.However the photographs of most structures near the quarry reveal cracks and dilapidated building walls.Recommendations are made on how to sustain and improve current blasting techniques.

An ANN-based approach to predict blast-induced ground vibration of Gol-E-Gohar iron ore mine,Iran

Blast-induced ground vibration is one of the inevitable outcomes of blasting in mining projects and may cause substantial damage to rock mass as well as nearby structures and human beings.In this paper,an attempt has been made to present an application of artificial neural network(ANN)to predict the blast-induced ground vibration of the Gol-E-Gohar(GEG)iron mine,Iran.A four-layer feed-forward back propagation multi-layer perceptron(MLP)was used and trained with Levenberg–Marquardt algorithm.To construct ANN models,the maximum charge per delay,distance from blasting face to monitoring point,stemming and hole depth were taken as inputs,whereas peak particle velocity(PPV)was considered as an output parameter.A database consisting of69data sets recorded at strategic and vulnerable locations of GEG iron mine was used to train and test the generalization capability of ANN models.Coefficient of determination(R2)and mean square error(MSE)were chosen as the indicators of the performance of the networks.A network with architecture4-11-5-1and R2of0.957and MSE of0.000722was found to be optimum.To demonstrate the supremacy of ANN approach,the same69data sets were used for the prediction of PPV with four common empirical models as well as multiple linear regression(MLR)analysis.The results revealed that the proposed ANN approach performs better than empirical and MLR models.

Determination of the ground vibration attenuation law from a singleblast: A particular case of trench blasting

The general transmissivity law of ground vibrations was studied,and a user-friendly methodology for determining the behavior of vibrations generated in any rock mass is proposed.The study was based on a single blast in a trench excavation,analyzing the vibration components recorded from two fixed locations.The attenuation law and the main variables according to the legal requirements,frequency and peak particle velocity(PPV),are defined with this novel method,achieving a high confidence level in a simple manner.The proposed approach can also have an important impact in terms of reducing the potential consequences of vibrations for the surrounding construction and achieving the required definition of rock mass.Reducing the cost and time in many projects where blasting techniques are applied is particularly useful for the design of future blasts.

Novel Soft ComputingModel for Predicting Blast-Induced Ground Vibration in Open-Pit Mines Based on the Bagging and Sibling of Extra Trees Models

This study considered and predicted blast-induced ground vibration(PPV)in open-pit mines using bagging and sibling techniques under the rigorous combination of machine learning algorithms.Accordingly,four machine learning algorithms,including support vector regression(SVR),extra trees(ExTree),K-nearest neighbors(KNN),and decision tree regression(DTR),were used as the base models for the purposes of combination and PPV initial prediction.The bagging regressor(BA)was then applied to combine these base models with the efforts of variance reduction,overfitting elimination,and generating more robust predictive models,abbreviated as BA-ExTree,BAKNN,BA-SVR,and BA-DTR.It is emphasized that the ExTree model has not been considered for predicting blastinduced ground vibration before,and the bagging of ExTree is an innovation aiming to improve the accuracy of the inherently ExTree model,as well.In addition,two empirical models(i.e.,USBM and Ambraseys)were also treated and compared with the bagging models to gain a comprehensive assessment.With this aim,we collected 300 blasting events with different parameters at the Sin Quyen copper mine(Vietnam),and the produced PPV values were also measured.They were then compiled as the dataset to develop the PPV predictive models.The results revealed that the bagging models provided better performance than the empirical models,except for the BA-DTR model.Of those,the BA-ExTree is the best model with the highest accuracy(i.e.,88.8%).Whereas,the empirical models only provided the accuracy from 73.6%–76%.The details of comparisons and assessments were also presented in this study.

Theoretical analysis on ground vibration attenuation using sub-track asphalt layer in high-speed rails

Using a finite element method （FEM） program, a Portland cement concrete slab trackbed （So）, and a sub- track asphalt roadbed （RAC-S） were modeled under high- speed train loads to analyze their responses to ground vibration attenuation, by considering 10, 15, 20, 25, and 30 thick sub-track asphalt layer replaced on the top of the upper subgrade. FEM results show that the vibration amplitude of RAC-S is at least three times lower than the vibration for So. The maximum vibration amplitude of RAC-S is linearly increased with train speed. The vertical acceleration is found to be reduced by more than 10 % when the asphalt layer thickness is increased from 10 to 20 cm. However, the reduction in vertical acceleration is only about 1% when the thickness of the asphalt layer changes from 20 to 30 cm. The vibration level is slightly lower if the asphalt layer has higher resilient modulus in the seasons of autumn or winter. This theoretical analysis indicates that a railway substructure that consists of a 10-20 cm thick high modulus asphalt layer located at the top of trackbed shows a good performance in ground vibration control for high-speed rails.

Engineering Characteristics of Ground Vibration Caused by Blasting Demolition of Urban Viaducts

Ground vibration accelerations caused by the collapse of blasting demolition of urban viaducts was recorded in ordered to analyze the engineering characteristics and effects on the surrounding buildings. Through the analysis of peak ground acceleration,peak frequency,duration and response spectra of the recorded vibrations in different acceleration arrays,some conclusions are drawn: the peak ground acceleration decreases with increasing distance, and the amplitude of vertical component is higher than that of the horizontal components,especially in near source region. The peak frequency of ground acceleration decreases with distance,and in near source region,it is larger than the natural frequency of the surrounding buildings,and thus it will not have much effect on the buildings. The duration of ground acceleration caused by collapse is longer than that caused by blasting itself. The vertical response spectrum is the largest of the three components,and it decreases rapidly in the near source region of about 30 m,but beyond that the distance decreases slowly.The horizontal components are smaller than the local seismic design spectrum,while the vertical component for natural period under 0.15 s exceeds the seismic design spectrum,but the natural periods of general buildings are usually beyond that domain,so this will not have much effect on the nearby buildings.

Measurement and characteristics of ground vibration caused by blasting demolition of urban overpass

To analyze the characteristics of ground vibration caused by blasting demolition of urban overpass, in this paper we introduced the measurement method and then studied the characteristics of recorded ground vi- brations. Through the analysis of peak acceleration, peak frequency and duration, results indicated that the ver- tical component of vibration is the most important in the region close to the collapse point; the collapse of bridge segments will lead to superposition of ground vibration, and isolation measures can reduce the peak ac- celeration but increase the duration of vibration; blasting and collapse vibration cause no damage to the re- served structure which indicates that blastin~ demolition is a safe and effective method.

Reasons and laws of ground vibration amplification induced by vertical dynamic load

The phenomenon of ground vibration amplification caused by railway traffic was found and proved. In order to study the reasons which cause the amplification, a drop-weight test was performed. Then, the model for both homogeneous and layered soil subjected to a harmonic vertical load was built. With the help of this model, displacement Green's function was calculated and the propagation laws of ground vibration responses were discussed. Results show that: 1) When applying a harmonic load on the half-space surface, the amplitude of ground vibrations attenuate with fluctuation, which is caused by the superposition of bulk and Rayleigh waves. 2) Vibration amplification can be enlarged under the conditions of embedded source and the soil layers. 3) In practice, the fluctuant attenuation should be paid attention to especially for the vibration receivers who are sensitive to single low frequencies(<10 Hz). Moreover, for the case of embedded loads, it should also be paid attention to that the receivers are located at the place where the horizontal distance is similar to embedded depth, usually 10 to 30 m for metro lines.

A 2.5D finite element approach for predicting ground vibrations generated by vertical track irregularities

Dynamic responses of track structure and wave propagation in nearby ground vibration become significant when train operates on high speeds. A train-track-ground dynamic interaction analysis model based on the 2.5D finite element method is developed for the prediction of ground vibrations due to vertical track irregularities. The one-quarter car mode,1 is used to represent the train as lumped masses connected by springs. The embankment and the underlying ground are modeled by the 2.5D finite element approach to improve the computation efficiency. The Fourier transform is applied in the direction of train＇s movement to express the wave motion with a wave-number. The one-quarter car model is coupled into the global stiffness matrix describing the track-ground dynamic system with the displacement compatibility condition at the wheel-rail interface, including the irregularities on the track surface. Dynamic responses of the track and ground due to train＇s moving loads are obtained in the wave-number domain by solving the governing equation, using a conventional finite element procedure. The amplitude and wavelength are identified as two major parameters describing track irregularities. The irregularity amplitude has a direct impact on the vertical response for low-speed trains, both for short wavelength and long wavelength irregularities. Track irregularity with shorter wavelength can generate stronger track vibration both for low-speed and high-speed cases. For low-speed case, vibrations induced by track irregularities dominate far field responses. For high-speed case, the wavelength of track irregularities has very little effect on ground vibration at distances far from track center, and train＇s wheel axle weights becomes dominant.

Inversion of excitation source in ground vibration from urban railway traffic

Urban trains running on ground surface lead to evironmental ground vibrations in the vicinity of railwaylines. The complicated vibration source of the system can hardly be measured directly. The inversion methodology in engineering seismology is borrowed here to study the dynamic exciting sourec, i.e., the wheel-rail unevenness. A dynamic coupled train-track-3D ground model is combined with a genetic algorithm for the inversion. The solution space of the inversion variables, the objective function and the solving genetic strategy of the inversion are determined, and a joint inversion for the wheel-rail unevenness source function and some track structure parameters is therefore designed. The wheel-rail unevenness PSD, being the source function of No. 13 Beijing urban railway, is obtained by the inversoin based on observed data in the field. The result indicates that the source function discribes the track unevenness in the range of wavelength over 1.2 m, and reflects properly wheel irregularites in the range of wavelength shorter than 1.2 m. It should be noticed that the urban rail traffic is not very fast, and this range of short wavelength is exactly corresponding to the main frequency band of environmental vibrations from the traffic. The unevenness of wavelength under 1.2 m is underestimated, and the ground vibration in the main frequency band must be underestimated consequently, if the track unevenness spectrum is taken as the source function. Rather than the track spectrum reflecting just the evenness of track, the wheel-rail spectrum expresses both the track unevenness and the irregularities of wheels, and therefore is more suitable to be the source function of urban railway traffic. It is also convinced that the exciting source inversion according to observed ground vibrations is an effective way to detect quantitatively the combined wheel-rail unevenness.

Ground vibration analysis under combined seismic and high-speed train loads

The rise of high-speed railway induces an increased probability of serious derailment accidents of operating high-speed trains during earthquakes.A two-and-half-dimensional finite element model(2.5D FEM)was developed to investigate the ground vibration under combined seismic and high-speed train loads.Numerical examples were demonstrated and the proposed method was turned out to provide an effective means for estimating ground vibration caused by high-speed train load during earthquakes.The dynamic ground displacement caused by combined seismic and high-speed train loads increases with the increase of the train speed,and decreases with the increase of the stiffness of ground soil.Compared with the seismic load alone,the coupling effect of the seismic and high-speed train loads results in the low-frequency amplification of ground vibration.The moving train load dominants the medium–high frequency contents of the ground vibration induced by combined loads.It is observed that the coupling effects are significant as the train speed is higher than a critical speed.The critical train speed increases with the increase of the ground stiffness and the intensity of the input earthquake motion.

Simple and fast prediction of train-induced track forces,ground and building vibrations

A simple and fast prediction scheme is presented for train-induced ground and building vibrations.Simple models such as(one-dimensional)transfer matrices are used for the vehicle–track–soil interaction and for the building–soil interaction.The wave propagation through layered soils is approximated by a frequency-dependent homogeneous half-space.The prediction is divided into the parts“emission”(excitation by railway traffic),“transmission”(wave propagation through the soil)and“immission”(transfer into a building).The link between the modules is made by the excitation force between emission and transmission,and by the free-field vibration between transmission and immission.All formula for the simple vehicle–track,soil and building models are given in this article.The behaviour of the models is demonstrated by typical examples,including the mitigation of train vibrations by elastic track elements,the low-and high-frequency cut-offs characteristic for layered soils,and the interacting soil,wall and floor resonances of multi-storey buildings.It is shown that the results of the simple prediction models can well represent the behaviour of the more time-consuming detailed models,the finite-element boundary-element models of the track,the wavenumber integrals for the soil and the three-dimensional finite-element models of the building.In addition,measurement examples are given for each part of the prediction,confirming that the methods provide reasonable results.As the prediction models are fast in calculation,many predictions can be done,for example to assess the environmental effect along a new railway line.The simple models have the additional advantage that the user needs to know only a minimum of parameters.So,the prediction is fast and user-friendly,but also theoretically and experimentally well-founded.

Artificial neural network with a cross-validation approach to blast-induced ground vibration propagation modeling

Given their technical and economic advantages,the application of explosive substances to rock mass excavation is widely used.However,because of serious environmental restraints,there has been an increasing need to use complex tools to control environmental effects due to blast-induced ground vibrations.In the present study,an artificial neural network(ANN)with k-fold cross-validation was applied to a dataset containing 1114 observations that was obtained from published results;furthermore,quantitative and qualitative parameters were considered for ground vibration amplitude prediction.The best ANN model obtained has a maximum coefficient of determination of 0.840 and a mean absolute error of 5.59 and it comprises 17 input parameters,12 neurons in a one-layer hidden layer,and a sigmoid transfer function.Compared with the traditional models,the model obtained using the proposed methodology demonstrated better generalization ability.Furthermore,the proposed methodology offers an ANN model with higher prediction ability.

Vibration Behavior of the Ground and Houses Caused by Monorail Traffic

The vibration behavior of the ground and houses caused by monorail traffic is discussed in this paper. The environmental ground vibration problem discussed herein occurs in a residential area near a monorail used for public transportation, Vibrations were measured on the ground at the side of monorail piers lacing the residential area and within the affected houses. Results indicate that the vibration level in the house was 60 dB or more, a level high enough to warrant complaints, Peculiar geological and geographical features are thought to contribute to the amplification of low frequency （-10 Hz） ground vibrations to irritable levels in these homes even though a distance of≥30 m separates the residential area and the monorail.

Rotational Population Measurement of Ultracold 85Rb^133Cs Molecules in the Lowest Vibrational Ground State

We measure the rotational populations of ultracold SS Rbla3 Cs molecules in the lowest vibrational ground state by a depletion spectroscopy and quantify the molecular production rate based on the measurement of single ion signal area. The SSRb133Cs molecules in the X1∑＋（v = 0） are formed from the short-range （2）^3П0＋（V = 10, J = 0） molecular state. A home-made external-cavity diode laser is used as the depletion laser to measure the rotational populations of the formed molecules. Based on the determination of single ion signal, the production rates of molecules in the J=0 and J = 2 rotational levels are derived to be 4800mole/s and 7200mole/s, respectively. The resolution and quantification of molecules in rotational states are facilitative for the manipulation of rotational quantum state of ultracold molecules.

Vibration reduction technology and the mechanisms of surrounding rock damage from blasting in neighborhood tunnels with small clearance

Interlaid rock is an important component in the construction of neighborhood tunnels that supports and reinforces the area between two tunnels.However,the blasting load during excavation can sometimes damage the interlaid rock and threaten the stability of a tunnel’s structure.This paper presents a case study of the small clearance section of the Liantang highway tunnel project in Shenzhen,China,where the minimum distance between the two tunnels involved is only 0.5 m.To reduce the damage to the interlaid rock caused by blasting loads,we proposed a four-part excavation method with a vibrationcushioning rock layer in the following tunnel of neighborhood tunnels.Numerical simulation was used to model the damage prevention mechanism of the vibration-cushioning rock layer and to better understand the propagation of cracks in the interlaid rock.Furthermore,based on the simulation results,combined microseismic controlled-blasting technology was implemented,using innovative blasting patterns combined with different charge structures and blasting equipment designed according to the varying thickness of the interlaid rock.Finally,this implementation succeeded in protecting interlaid rock during blasting operations.