Ground Surface Vibration Research Articles

Benchmark for three-dimensional explicit asynchronous absorbing layers for ground wave propagation and wave barriers

This paper presents a benchmark for three-dimensional explicit asynchronous absorbing layers for modeling unbounded domains through a standard displacement-based finite element method: Three-dimensional Perfectly Matched Layers (PML) is compared to recently proposed Absorbing Layers with Increasing Damping (ALID) based on Rayleigh and Kosloff damping formulations.The coupled problem, including the interior subdomain and the absorbing layers, is implemented in the framework of Heterogeneous Asynchronous Time Integrator (HATI), enabling the absorbing layers to be handed with an explicit Central Difference scheme, with fine time steps, independently from the time stepping procedure adopted in the interior subdomain. Simple 3D Lamb’s tests are considered by using different kinds of absorbing layers. The superiority of the PML in terms of the accuracy and computation time is highlighted. Finally, realistic 3D applications are investigated, such as the Lamb’s test and the study of the screening effect provided by a horizontal wave barrier in mitigating the ground surface vibration generated by an excited plate.

Analysis of the impact of shallow subway train traffic on urban development

The article discusses the process of propagation of vibrations in a soil massif from a moving subway train. With the help of previously performed measurements of ground surface vibrations above a shallow metro line, it was found that the electrical insulating joint of rail strings is a source of increased vibrations when a train enters the station from a tunnel, which can lead to an excess of vibration acceleration levels in residential and industrial buildings limited by sanitary standards. The main types of wheel and rail defects are considered. The propagation of vibrations in unlimited space from a moving subway train in a tunnel, represented by an absolutely rigid body, loaded with dynamic action, taking into account the shock impact at the rail joint, has been studied. The dependences of the parameters of the wave field in infinite space and the displacement of the points of the tunnel on the frequency of the forcing action are found. It is noted that the parameters of the wave field decrease with an increase in the frequency of the external forcing action. The results obtained can be used to solve the problem of the propagation of vibrations in a confined space from moving subway trains.

Prediction model of ground vibration based on combined model

The two basic functions of power function and exponential function are used, and the variable weight combination model based on the Lagrange multiplier of the two basic functions is used to predict the surface vibration attenuation. Based on the measured data of the ground surface vibration of viaducts and embankments, a prediction model can be established through a combination model. A better fitting effect can be acquired through this prediction model. The model can obtain better prediction with fewer parameters and can comprehensively reflect the different model information of the two models. Although the amount of data is limited, it can also be obtained. The predictions that are in good agreement with the actual situation are better, the vibration attenuation in the near field is faster, and the vibration attenuation in the far field is slow, which are consistent with the actual situation.

Modal Analysis of Selected Measuring Bases and Their Impact on the Recorded Level of Surface Accelerations

In predicting the impact of vibrations propagated in a ground on newly designed construction objects, it is extremely important to reliably measure the time histories of velocity or acceleration at the site of the planned investment. As some studies show, the method of coupling accelerometers and geophones to the ground can affect not only the level of peak particle accelerations (PPA) or peak particle velocities (PPV)—commonly used in this type of evaluation—but also vibration frequency distribution of recorded signals. This makes it difficult to compare and analyze the results obtained by various research teams. Conclusions based on this type of comparison may be wrong. For this reason, it is extremely important that reliable dynamic measurements related to the propagation of ground surface vibrations should be carried out using not only appropriately selected measuring equipment (with the required sensitivity and measurement ranges—both in the time domain and frequency domain), but also the measurement bases/setups used for mounting various types of transducers, whose natural frequencies will be outside the frequency range relevant to the possible impact of vibrations on buildings and human beings inside. The paper presents the results of modal analyses carried out with the use of Ansys Engineering Simulation and 3D Design Software (based on the Finite Element Method) for three different types of measuring bases used to coupling accelerometers to the ground. Measuring bases selected for numerical analyses were in the form of a stiff steel spike of an X-shaped cross section (a measuring base No. 1) and two steel spikes of L-shaped cross-sections (a measuring bases No. 2 and No. 3). In the places of screwed accelerometers (three different types of IEPE/ICP transducers of varying sensitivity and a weight) point masses were attached to the measuring bases. As a result of the analyses, it was possible to determine the impact of individual methods of coupling of accelerometers to the ground on the reliability of recorded ground surface accelerations. Among others it was concluded that in each analyzed case the lowest natural frequencies of the measuring bases with attached accelerometers significantly exceeded 100 Hz. The widest frequency band free of resonance vibrations can be provided by the measuring base No. 3 (L50 × 50 × 5).

Effects of train operational parameters on ground-borne vibrations induced by twin metro tunnels

ABSTRACT 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 and train's speed effect on the ground surface vibration response while two trains passed each other in the opposite direction in the twin subway tunnels. Firstly, a 3D finite element (FE) model of a twin circular tunnel in a homogeneous soil is developed and verified by the previous analytical studies. Then, sensitivity analyses are performed to assess the effect of train's speed and axle load on the ground surface response. The achieved results show that an increment of the train's speed in both tunnels causes increment PPV (Peak Particle Velocity) at the ground surface, but increasing the speed of one of the trains respect to the other one has a considerable influence on surface vibrations. The vibrations are increased about 2 dB and 3.5 dB by doubling the speed of both trains and one of the trains, respectively. Vibrations level at the ground surface is enhanced with increasing both trains axle load, but the ground surface vibrations are more sensitive to the difference between two trains axle load.

On Image Fusion of Ground Surface Vibration for Mapping and Locating Underground Pipeline Leakage: An Experimental Investigation.

This paper is concerned with imaging techniques for mapping and locating underground pipeline leakage. Ground surface vibrations induced by the propagating axisymmetric wave can be measured by an array of acoustic/vibration sensors, with the extraction of magnitude information used to determine the position of leak source. A method of connected graph traversal is incorporated into the vibroacoustic technique to obtain the spatial image with better accuracy compared to the conventional magnitude contour plot. Measurements are made on a dedicated cast iron water pipe by an array of seven triaxial geophones. The spectral characteristics of the propagation of leak noise signals from underground water pipes to the ground surface are reported. Furthermore, it is demonstrated that suspicious leakage areas can be readily identified by extracting and fusing the feature patterns at low frequencies where leak noise dominates. The results agree well with the real leakage position in the underground pipeline.

Vibration mitigation efficiency of an inclined, curved, open trench

The vibration screening efficiency of a curved, inclined, open trench is investigated in this paper. An elastic, transversely isotropic half-space with hysteretic damping, acted upon by a harmonic vertical excitation, is assumed. Equations of motion with absorbing boundary conditions are presented and numerically integrated using FlexPDE software, based on the finite element method. The barrier efficiency is analysed in terms of the reduction of the vertical and horizontal components of the ground surface vibration. The results are presented for trenches with different geometric features based on the non-dimensional amplitude reduction factor. The trench inclination angle, the shape of the trench surface and the distance between the source of vibration and an obstacle are investigated as factors that can improve the trench reduction ability. It is demonstrated that a better attenuation of vibration is achieved with the proposed inclined trench than with its vertical counterpart. Moreover, the vibration mitigation effect is more significant in the case of a more horizontally located trench than for its vertical counterpart (even up to 5 times smaller displacement amplitudes for the vertical displacement component). Additionally, assuming the same trench depth, the vibration reduction effect is better in the case of a smaller number of rings used. The vibration attenuation efficiency is more visible if the trench is located closer to the vibration source.

Study on Surface Vibration Characteristics of Composite Shallow-buried Tunnel Blasting Construction

Based on the background of the construction of the mining section at the southern end of Yangli Station of Fuzhou Metro Line 2 project, in order to study the ground surface vibration law during the blasting construction of tunnels in the upper soft and lower hard composite strata, the vibration velocity data were obtained through field tests, and the traditional and modified Sadowski formulas were used to fit and analyze the vibration velocity respectively, which were verified by numerical simulation. The results show that under the condition of composite stratum, the peak value of radial vibration velocity of blasting construction on the surface of cave-forming area is the largest, and the peak value of vertical vibration velocity on the surface of non-cave-forming area is the largest; the ground vibration of shallow-buried tunnel excavation area in composite stratum has void effect, and the larger the distance between the blasting centers, the more obvious the void effect; the fitting degree of traditional Sadowski formula is lower than that of modified Sadowski formula V=KQaRb; because of the existence of soft-hard interface, the attenuation rate of vertical vibration velocity is the sharpest relative to the radial and tangential vibration velocities on the surface of composite shallow-buried tunnels. At the same time, the feasibility of numerical software to simulate such engineering blasting construction is verified.

Response Spectra of Structures under Subway Induced Vibrations

Passing underground trains induce vibrations transmitted to the ground surface and the nearby structures. Ordinarily, these vibrations do not result in structural damage but can harm nonstructural elements and disturb the occupants. These effects are more pronounced when evaluating buildings like hospitals, laboratories, museums, etc., and their assessment is an important design need. To respond to this requirement, in this paper response spectra for passing trains moving with different velocities are calculated. Using these spectra, without resorting to the time consuming and costly analysis of a tunnel-soil system under moving loads, the maximum structural responses can be calculated rapidly. To make this end, the soil-tunnel interaction is modeled using a three dimensional (3D) finite difference scheme under the standard moving train loads. The dynamic analysis of such a system results in the ground surface vibration time histories at different distances from the tunnel axis. Then the maximum values of acceleration, velocity, and displacement responses are calculated for a single degree of freedom (SDOF) dynamical system. The above calculations are accomplished for different standard trains, train velocities, tunnel depths, distances from tunnel, and soil types, and are presented as response acceleration, velocity, and displacement spectra.

GPR Image Enhancement Based on Frequency Shifting and Histogram Dissimilarity

In the ground-penetrating radar (GPR) B-scan images, various noise sources are superimposed due to the ruggedness of the surface, sensor vibration, and multiple reflections. Additionally, the intensity of the received signals from small-size or low-metal-content landmines is low. Thus, it is difficult to accurately detect buried mines. In this letter, we propose an effective method to improve the B-scan image so that accurate landmine detection is possible even in such conditions. The proposed B-scan image enhancement method is comprised of two main techniques: an A-scan transformation based on frequency shifting and a background-landmine dissimilarity measurement using cumulative intensity distribution (CID). Based on frequency shifting, an A-scan transformation is devised to attenuate the strong ac component contained by the received A-scan signal. The CID-based dissimilarity is introduced to measure how an A-scan differs from a background model in the presence of a landmine. The proposed dissimilarity measure provides a robust response to a rugged ground surface and sensor vibration. For performance analysis, we compared our method with some conventional methods using the GPR data set acquired by an ultra wide band GPR sensor manufactured by Hanwha Systems Co., Ltd. We carried out various experiments and verified that the proposed method has a better performance than the conventional methods.

Tree root detection from ground surface vibration measurements

Rapid development of urban infrastructure in past decades together with a relatively recent growth of awareness of its impact on the natural environment result in an increased interest in non-destructive ground interrogation methods. Tree root damage is a very well known issue in civil engineering and can emerge as road surface fracture, building foundations disintegration or pipe penetration, among others. In this paper we investigate the feasibility of using a vibroacoustic method for tree root mapping. The core of the idea is that the mechanical waves induced by an excitation mechanism acting on the tree trunk propagate to the roots and then radiate into the surrounding soil. Owing to that, the response measured at the ground surface contains the contribution of waves radiating from roots and can be used for mapping their extent. In this paper, we report a set of field experiments on a ‘purpose-built’ root-trunk model buried underground. These preliminary results both demonstrate the technique and shed light on related challenges and limitations.

A proposal for vibration isolation of structures by using a wave generator

This paper describes a concept for vibration-mitigation techniques with the potential to reduce the ground vibration amplitudes by applying an additional vibration source. The idea is presented through the case of an impact load. Equations of motion for the transversally isotropic ground model with absorbing boundary conditions are presented and numerically integrated using FlexPDE software, based on the finite element method. The efficiency of the solution is analysed in terms of reducing the vertical and horizontal components of ground surface vibrations. Results in the form of a dimensionless amplitude reduction factor are presented for four different locations of a generator and different soil conditions. In each analysed case the vibration mitigation effect in a three-story building was achieved.

An analytical model of ground surface vibration due to axisymmetric wave motion in buried fluid-filled pipes

The axisymmetric (n=0) fluid-borne (s=1) wave has been exploited with varying degrees of success in practical surveys for determining the location of buried pipes. Difficulties are sometimes encountered in interpreting ground surface vibration data, whilst attempting to locate the pipes, due to the occurrence of abrupt changes in the phase response over the usable frequency range. Based on a wave propagation model developed recently, this paper presents an analytical model for predicting the ground surface displacements resulting from the radiated elastic waves in the soil medium. Two representative soils have been specifically considered, where the s=1 wave in the pipe will leak shear waves into the soil, but may or may not leak compressional waves. In each of these cases, numerical simulations are presented to predict the ground surface displacements. The model is used to demonstrate how, when both compressional and shear waves are radiated, they can interfere such that abrupt phase changes occur at the frequencies coincident with magnitude minima in the ground surface displacements; when only shear waves are radiated, such interference does not occur. Furthermore, for sandy soil, it is found that the horizontal displacement is dominated by the radiated shear wavenumber component whereas the vertical displacement is controlled by the radiated compressional wavenumber component. Using the analytical model, theoretical predictions of ground surface displacements are compared with experimental data from a dedicated MDPE pipe rig.

Continuous monitoring of deformations in mines using laser interferometer–deformograph

The article gives a detail description of the deformation graphing equipment designed at the Institute of Laser Physics, SB RAS, for the geodynamic monitoring of stress state in mine galleries and other underground openings, and for the analysis of ground surface vibrations before earthquakes and other seismic events. The more comprehensive study of separate rock mass blocks uses the advanced modification of the prototype deformograph introduced into service on Talgar testing ground in Kazakhstan. The programming support of the equipment is described.

3D Modelling of Ground Surface Vibration Induced by Underground Train Movement

Correia et al. [1], developed an expression to model the force distribution due to axle loads, with respect to the moving referential. The above force distribution was used for Finite Element Analysis using PLAXIS 3D. A code is developed in MATLAB to generate a matrix of dynamic multipliers for each static point load applied along the railway track with each time step. The amount of load applied is equal to the axle load of the train resulting from the solution of the Winkler Beam for the movement of a load. The results can be used for gauging the effect of changing various geological and physical parameters on the distribution of force due to axle load. Once calibrated to geotechnical and physical data corresponding to sites above actual underground train tracks, the model can be used to predict the effect of vibrations on existing infrastructure.

A novel method for the remote condition assessment of buried pipelines using low-frequency axisymmetric waves

“Mapping the Underworld” is a large multi-disciplinary, multi-university research programme taking place in the UK, which aims to revolutionize the way we undertake streetworks. Within this programme, a number of vibration-based techniques for remotely detecting and locating buried pipes have been developed. Relying either on the direct excitation of a pipe as it comes up to the surface or excitation of the ground in the vicinity of a buried pipe, mapping the ground surface vibration response allows information to be gathered concerning the pipe's exact position. However, contained within this surface response is often information which could, if utilized appropriately, provide insights into the condition of the pipe as well as its location. Furthermore, critical information regarding the condition of the ground in which a pipe is buried could, in some circumstances, be gleaned. In this paper, how this additional information might be extracted, used and eventually exploited is explored. Providing the basis for work currently being undertaken in a new programme, “Assessing the Underworld”, example results are presented which demonstrate the immense potential of the proposed methods.

A study of the reduction of ground vibrations by an active generator

This paper presents the concept of using an additional generator to prevent ground vibrations. A linear, transversally isotropic three dimensional half-space with the hysteretic damping model, acted upon by a harmonic vertical excitation is assumed. Equations of motion for the transversally isotropic ground model with the absorbing boundary conditions are presented and numerically integrated using FlexPDE software, based on the finite element method. The efficiency of the solution is analysed in terms of reducing the vertical and horizontal components of ground surface vibrations. Results in the form of a dimensionless amplitude reduction factor are presented for four different locations of a generator. The influence of the soil parameters and layers locations on the additional generator's efficiency is investigated. The vibration reduction efficiency in a four-story building is also presented.

Effect of horizontal wave barriers on ground vibration propagation.

The aim of this article is to introduce a method to mitigate ground surface vibration through a flexural plate coupled to the ground and acting as a horizontal wave barrier. Using the thin plate hypothesis, two flexural plates are coupled to the ground, the first plate being the excited plate and the second plate the horizontal wave barrier. For instance, the first plate may represent a slab track and be excited by the tramway wheels. A solution to the problem can be found using a spatial two-dimensional Fourier transform of the elastodynamics equation for the ground and a modal decomposition for the flexural plate vibration. The authors show that vibration is substantially mitigated by the horizontal wave barrier and depends on its thickness and width. When the top surface wavelength becomes smaller than twice the plate width, the horizontal wave barrier acts as a wave barrier in the frequency range of interest, i.e., from 20 Hz.

Comparative Feature Analysis of Ground Surface Vibration Induced by High-Speed Train Running on Viaduct and Embankment

Based on the Abaqus parallel computing cluster system platform, the three-dimensional finite element model of train-track-viaduct/embankment-foundation-soil coupling is established. The three-dimensional space-time variation and Fourier spectrums characters of ground surface vibration vertical accelerations by high-speed train running on viaduct and embankment are simulated. The result shows that ground surface vibration is mainly excited by periodic axle force of the train in the site near the viaduct pier. In the site far from the viaduct pier, ground surface vibration is mainly from the transmission of the site near the viaduct pier. With the increased distance between the viaduct pier, the peak value of ground surface vibration vertical acceleration decreases, and decreases significantly when the distance is within 10m. There are two main frequency bands of Fourier spectrum of ground surface vibration vertical acceleration: low-frequency band 0-12Hz and high-frequency band 35-47Hz of viaduct route, and low-frequency band 0-21Hz and high-frequency band 25-45Hz of embankment route. In general, with the increased distance between viaduct/embankment, Fourier spectrum amplitude of every frequency band decrease, and attenuation speed of high-frequency band is much faster than-frequency band’s.

A shear wave ground surface vibration technique for the detection of buried pipes

A major UK initiative, entitled ‘Mapping the Underworld’ aims to develop and prove the efficacy of a multi-sensor device for accurate remote buried utility service detection, location and, where possible, identification. One of the technologies to be incorporated in the device is low-frequency vibro-acoustics; the application of this technology for detecting buried infrastructure, in particular pipes, is currently being investigated. Here, a shear wave ground vibration technique for detecting buried pipes is described. For this technique, shear waves are generated at the ground surface, and the resulting ground surface vibrations measured. Time-extended signals are employed to generate the illuminating wave. Generalized cross-correlation functions between the measured ground velocities and a reference measurement adjacent to the excitation are calculated and summed using a stacking method to generate a cross-sectional image of the ground. To mitigate the effects of other potential sources of vibration in the vicinity, the excitation signal can be used as an additional reference when calculating the cross-correlation functions. Measurements have been made at two live test sites to detect a range of buried pipes. Successful detection of the pipes was achieved, with the use of the additional reference signal proving beneficial in the noisier of the two environments.