Prediction of Ground and Building Vibrations Induced by High-speed Trains using a 3D Coupled Numerical Model Based on a Spectral Element Analysis Code

Noise and Vibration Mitigation for Rail Transportation Systems

Train-induced ground vibration problems have become an important subject, as the number of the high speed railroad construction projects rapidly increases worldwide. Various numerical approaches have been proposed and used for the prediction of the train-induced ground vibration. However, the estimation performance has not been satisfactory due to the difficulty in modeling the train-transit loads on railroad structures and the structure-soil interaction system, which are essential for the accurate prediction of ground vibration. In this study, a new semi-analytical method was proposed for the prediction of ground vibration and the evaluation of environmental vibration levels with simple measurements of the ground vibration on the surface. The proposed method does not need any analytical model for inputting the train load. Instead, it identifies the effective train loads acting on the railroad track structure based on the measured ground responses at several locations and the numerical model of the structure-soil interaction system through the identification of the properties of the soil layers. Then, the effective train load is utilized as an input to the structure-soil interaction problem to predict the ground vibrations and the environmental vibration levels of the structures. A finite and infinite element model was utilized to solve the wave propagation problem in the soil medium in the frequency domain. Field validations were carried out at a site where Korea high-speed trains run over an elevated bridge structure. The predicted ground accelerations were found to be in good agreement with the measured data.

Numerical prediction of low-frequency ground vibrations induced by high-speed trains at Ledsgaard, Sweden

Experimental validation of a simplified numerical model to predict train-induced ground vibrations

The dynamically induced ground vibration from high speed trains (HSTs) is investigated using a semi-analytical vehicle–track–ground coupling model. A multi-body vehicle is adopted along with rail irregularity considered in the model. The soil is simulated as a saturated poroelastic half-space with two elastic layers. The coupling system is solved in the transformed domain by applying the Fourier transform, and the dynamic stiffness matrix method is used to deal with the layered soil. The time-domain solutions are obtained by the inverse fast Fourier transform (FFT). The effects of the vehicle speed, observation location, rail irregularity, subgrade-bed stiffness, and vehicle type on the ground vibration are investigated thoroughly. The results show that all these factors can significantly affect the dynamically induced ground vibration.

Quantification of ground-vibrations generated by high speed trains in ballasted railway tracks

The existing attenuation equation is examined to evaluate the reliability for ground vibration attenuation induced by high-speed trains. Several representative attenuation coefficients are applied to predict ground vibration and then compare them with field measured results for high-speed trains on bridge and embankment. Based on these analyses, the results are comparable for both bridge and embankment structures, and the existing attenuation equation can be used to reasonably predict ground vibration. Attenuation coefficients based on each one-third octave band center frequency and the frequency range for predicting ground vibration are more reliable and consistent. A simple and general methodology for the attenuation of ground vibration by high-speed trains is proposed for engineering practice.

This paper focuses on the dynamic interactions between a Shinkansen viaduct and the nearby ground when a high speed train is running along the viaduct. Due to the characteristics of the structure-foundation-soil system, a substructure method is employed to divide the global system into two substructures: one consists of the superstructure of track girder and supporting piers, the other consists of the foundation and near ground. Both substructures have continuity conditions at the interfaces, i.e. deformation continuity and force continuity. The superstructures are modeled by 3-dimensional (3-D) beam elements with a structural procedure, while the substructure is analyzed through a pseudo 3-D axisymmetric finite element method. A field test was conducted in the near field of the Shinkansen viaduct to examine the vibration level. The measurement data also help us to understand the wave motion influenced by the geometric properties of the structures and the moving train. Based on the field test results, a thorough interpretation is provided by analyzing both the structures and the soil. Further, computation simulation is conducted to investigate the vibrations in the ground to a wider extent. According to the nature of vibration, a combined countermeasure is proposed which involves the source motion control and the wave propagation obstruction. Satisfactory mitigation is achieved by the combined measure.

Influences of piles on the ground vibration considering the train-track-soil dynamic interactions

The prediction of ground and building vibrations has been established for surface lines and has now been extended to tunnel lines. The wave propagation in homogeneous or layered soils (the transmission) is calculated by an integration in wavenumber domain. The wave amplitudes at different distances and for different frequencies will be analysed for the following situations. 1. The horizontal propagation from a surface point to a surface point constitutes the basic rules. 2. The horizontal propagation from a source point at depth to a receiver point at depth which is related to a building with a deep basement or on a pile foundation. 3. The propagation from depth to the surface, which is the normal case for free-field measurements, has some different characteristics, for example a weaker attenuation with the horizontal distance from the source, which can be approximated by the full-space solution and the reflection rules for incident waves. The emission from a tunnel structure has been calculated by a finite-element model of the tunnel combined with a boundary-element model of the soil giving the reduction compared to a point-load excitation. The immission has been analysed by finite-element models of tunnel-soil-building systems for examples of research and consultancy work. Measurement results from a high-speed and a metro line confirm some of the established rules.

Application of multivariate analysis for prediction of blast-induced ground vibrations

During blasting operations in open pit mines, most of the blast energy (approximately 40%) is wasted due to ground vibration. This phenomenon causes damages to the surrounding structures and pit slope. Therefore, prediction of ground vibration with an appropriate degree of accuracy is important to identify safety area of blasting. In this paper, in the first step, a predictive equation based on gene expression programming (GEP) was developed to estimate ground vibrations of blasting operations conducted in Gol-E-Gohar iron mine. For this aim, 115 blasting operations were identified and the most effective parameters on peak particle velocity (PPV), i.e., burden, spacing, stemming, hole-depth, hole-diameter, powder factor, maximum charge per delay and distance from the blast face were collected from the mine. Capability of the developed GEP model was compared with a non-linear multiple regression (NLMR) model and five conventional equations. The obtained results revealed that the developed GEP model is more efficient compared to the other models in predicting PPV. In the second step, to optimize the GEP predictive model, cuckoo optimization algorithm (COA) was employed and proposed. To do this, several strategies were defined and then several optimized blasting patterns were determined for each strategy. It was found that by developing the COA model, a significant reduction can be happened in PPV values.

SUMMARY The Spectral Analysis of Surface Waves (SASW) method is a technique for the identification of the thickness, dynamic shear modulus, and damping ratio of shallow soil layers. The method consists of an in situ experiment to determine the dispersion curve of the soil and the solution of an inverse problem where the corresponding soil profile is identified. The SASW method has been used to investigate pavement systems, to assess the quality of ground improvement, to determine the thickness of waste deposits, and to identify the dynamic soil properties for the prediction of ground vibrations. In this paper, the focus is on the last application. The information on the dynamic soil properties provided by the dispersion curve is limited. The dispersion curve is insensitive to variations of the soil properties on a small spatial scale and at a large depth. As a result, the solution of the inverse problem in the SASW method is non-unique and hence uncertain. The prediction of ground vibrations is therefore based on a soil model with uncertain properties. In this study, a Bayesian approach is followed to solve the inverse problem in the SASW method. A prior stochastic soil model is first formulated using the information that is available before the SASW test is performed. A Markov chain Monte Carlo method is used to transform the prior model into a posterior stochastic soil model that accounts for the SASW test results. Finally, the prediction of ground vibrations is addressed. The posterior soil model is used to assess the robustness of the predicted vibrations, accounting for the uncertainty on the results of the SASW test. As an example, the free field vibrations due to a hammer impact on a concrete foundation are considered. More complicated problems, such as the prediction of road and rail traffic induced vibrations, can be addressed in a similar way.

PurposeThis paper aims to analyze the bearing characteristics of the high speed train window glass under aerodynamic load effects.Design/methodology/approachIn order to obtain the dynamic strain response of passenger compartment window glass during high-speed train crossing the tunnel, taking the passenger compartment window glass of the CRH3 high speed train on Wuhan–Guangzhou High Speed Railway as the research object, this study tests the strain dynamic response and maximum principal stress of the high speed train passing through the tunnel entrance and exit, the tunnel and tunnel groups as well as trains meeting in the tunnel at an average speed of 300 km·h-1.FindingsThe results show that while crossing the tunnel, the passenger compartment window glass of high speed train is subjected to the alternating action of positive and negative air pressures, which shows the typical mechanic characteristics of the alternating fatigue stress of positive-negative transient strain. The maximum principal stress of passenger compartment window glass for high speed train caused by tunnel aerodynamic effects does not exceed 5 MPa, and the maximum value occurs at the corresponding time of crossing the tunnel groups. The high speed train window glass bears medium and low strain rates under the action of tunnel aerodynamic effects, while the maximum strain rate occurs at the meeting moment when the window glass meets the train head approaching from the opposite side in the tunnel. The shear modulus of laminated glass PVB film that makes up high speed train window glass is sensitive to the temperature and action time. The dynamically equivalent thickness and stiffness of the laminated glass and the dynamic bearing capacity of the window glass decrease with the increase of the action time under tunnel aerodynamic pressure. Thus, the influence of the loading action time and fatigue under tunnel aerodynamic effects on the glass strength should be considered in the design for the bearing performance of high speed train window glass.Originality/valueThe research results provide data support for the analysis of mechanical characteristics, damage mechanism, strength design and structural optimization of high speed train glass.

The effect of critically moving loads on the vibrations of soft soils and isolated railway tracks