Vibration Propagation Characteristics Research Articles

Vibration characteristics of subway turnout area during vehicle deceleration and assessment of the model accuracy

Frog gaps and rail joints produces intricate wheel-rail contact conditions within subway turnouts, which results in intense vibrations. This study describes vibration tests conducted on several typical cross-sections of a turnout, which aimed at understanding the vibration transfer characteristics of typical section in turnout area. To separation the vibration signals from each carriage, wavelet analysis and peak detection algorithms were utilized. Using a 2D kernel density algorithm, representative data from the carriages were clustered, effectively isolating the influence of interference data. A coupled vehicle-turnout-tunnel-soil vibration analysis model was established, combining multiple spatial and temporal scales and the accuracy of its prediction was evaluated by comparing the calculated results to statistical test results.The test results indicate that when the train decelerated through the turnout, there was a significant variation in the vibrations of different train carriages, with a 13 dB difference in the total rail vibration levels. The rail joints and frog gap present in the turnout resulted in high vibration level in the tunnel walls. The main frequency of tunnel wall vibration in the frog gap section was 63 Hz, and the total vibration level was 84.9 dB. The accuracy of vibration response prediction was evaluated by comparing the calculated results to statistical test results using probability density functions, and the model errors were maintained within 10 % of the test data. The presented vibration testing and modelling results of vibration propagation characteristics in various directions for the subway turnout area will provide a foundation for selecting vibration mitigation measures.

Experimental study on the characteristics of vibration energy propagation in the subway turnout area

Due to the scarcity of urban land resources, the development model of building over rail transit has rapidly emerged. The turnouts near the train depots and stations have become significant sources of environmental vibrations. This paper employs on-site experimental methods to measure the vibration acceleration of rail, track slab, and tunnel wall at multiple sections in the turnout area when a subway train passes through. The vibration intensities at different sections of the turnout area are analyzed, and the vibration reduction effects of vibration isolation fasteners and steel-spring floating slabs in the turnout area under similar conditions are compared. Finally, an energy evaluation method is used to analyze the vibration propagation characteristics on the non-isolated turnout frog section. Obtained the propagation and attenuation characteristics of vibrations in different frequency bands in the turnout area based on on-site test data.

Field monitoring of vibration characteristics during advanced ductule installation in sandy cobble stratum

The sandy cobble stratum presents a high risk for underground tunnel construction due to its low cohesive properties and susceptibility to loosening and falling. The use of Advanced ductule for grouting reinforcement inevitably results in vibrations, and understanding how these vibrations propagate is crucial in selecting tunnel engineering support schemes and responding to accident risks. Based on a bored tunnel under construction in Xi’an, field vibration propagation characteristics testing were carried out for advanced ductile installation. The time-history response and frequency distribution characteristics of the vibration velocity within the tunnel face under sandy cobble stratum conditions were studied, and the law of vibration propagation attenuation within the tunnel face range was obtained. The results showed that: 1) During the conduit drilling process, the tunnel face mainly experienced vertical vibrations, with the horizontal velocity amplitude accounting for only 15%–20% of the vertical velocity amplitude. At a distance of 1.0 m from the conduit, the vertical velocity amplitude reaches 10.602 mm/s, and the vibration energy concentrates mainly in the frequency range of 150–250 Hz. At a distance of 1.5 m from the conduit, the bidirectional vibration velocity significantly attenuates; 2) The vibration characteristics within the tunnel face can be classified into three primary areas: “Loose and Falling” area, “Significant Vibration” area, and “Vibration Attenuation” area. Loose, falling and significant vibrations occurred mainly within a range of about 1.25 m around the conduit. 3) As the diameter of the conduit decreases, the amplitude of vertical vibration velocity decreases by about 20%. By reducing the design diameter of the advanced ductule in a reasonable manner, it is possible to effectively mitigate the impact of vibration caused by the sandy cobble stratum during installation. This can yield a positive impact, curtailing the occurrence of the tunnel’s collapse phenomenon and ensuring its stability.

Experimental study on the influence of cracks on tunnel vibration under subway train load

The impact of train vibration on the tunnel lining is a popular research topic. Under long-term train operation, the tunnel lining may incur damage, mainly longitudinal cracks, which will further increase the vibration caused by running trains, impacting the lining and the surrounding soil and eventually endangering the safety of train operation. To understand the influence of cracks on tunnel vibration under train load, we performed a model test of a shield tunnel with and without typical cracks based on a line of Hangzhou metro prototype to characterize its dynamic responses under train vibration loads. To simulate the tunnel lining material, the tunnel segment was lined up with polymer cast nylon with low creep rate and high strength. An inverted shaker simulated the train vibration load, and an accelerometer was used to measure the dynamic response of the tunnel structure and the surrounding soil. The results show that the dynamic response of the cracked section is significantly larger than that of the intact section, and due to the propagation characteristics of vibration, the expansion effect inside the tunnel is significantly greater than that of the surrounding soil. When the frequency spectrum results of the tunnel structure and the surrounding soil are compared, it is found that the vibration level of the surrounding soil due to cracks is mainly concentrated at around 100 Hz, while that of the tunnel structure at around 315 Hz, indicating that the cracks have a targeted effect on the expansion of the dynamic response. Meanwhile, the excessive vibration of intact segments is –2 or –1 dB, and the existing vibration reduction measures can meet the damping requirements. However, the excessive vibration caused by typical cracks can go up to 12 dB. Therefore, corresponding vibration reduction measures should be taken according to specifications. Finally, this paper proposes some vibration reduction suggestions and crack repair measures.

The vibration propagation and damage distribution characteristics of deep-buried underground cavern blasting

AbstractWith the increase of the scale of an underground cavern, more and more towering underground side walls are left behind by blasting operation, which leaves a huge hidden danger to the structure safety of an underground cavern. Taking the propagation mechanism and damage distribution characteristics of blasting vibration along the elevation direction as the research subject, the propagation mechanism of blasting vibration along the elevation direction of high side wall of a deep-buried underground cavern can be obtained by comprehensive application of theoretical analysis, dimensional analysis, formula derivation, numerical analysis, and other research methods. Through multiangle comparative analysis, the internal mechanism of blasting vibration under elevation effect in underground caverns is revealed, and combined with the relationship between surrounding rock damage and blasting vibration velocity, the distribution characteristics of blasting vibration and damage under the elevation effect are proposed. In addition, through the establishment of a mechanical model of the response of blasting vibration of underground high side walls, the prediction formula of particle vibration velocity along the elevation direction under blasting vibration condition is analyzed, and the formula is adjusted and modified, which can meet the developing requirements of surrounding rock damage control precision.

Propagation characteristics of vibration induced by medium-low-speed maglev train running on subgrade

As a new generation of urban transit system, the medium-low-speed maglev transport entered a rapid development stage. However, the report about the ground vibration due to running medium-low-speed maglev train (mlsMT) is very limited. Therefore, an in-situ experiment and numerical analysis are systematically carried out to investigate the vertical and horizontal ground vibrations induced by mlsMT running on subgrade. The experiment was performed on the Changsha Maglev Express under different train load conditions. The numerical analysis is carried out by using the two-step analysis method. In the first step, the mlsMT-guideway spatially coupled dynamics model is developed to obtain the rail supporting forces during train passing. In the second step, a three-dimensional finite element model of guideway-subgrade-ground system is established, and then the rail supporting forces are taken as the external loads to calculate the ground vibration. After well validated by the experiment, the two-step analysis method is employed to study the time- and frequency- domain characteristics of the vertical and horizontal vibrations propagating from guideway to ground, under the conditions of different train speeds and double line operation. Results show that the vibrations induced by mlsMT are significantly different from those induced by the traditional wheel/rail steering train and the high-speed maglev train. The horizontal ground vibrations are not only more serious than vertical ones, but also have obvious vibration amplification phenomenon. Besides, the subgrade can obviously decrease the vertical and horizontal vibrations propagating to ground. With the increasing distance to the guideway centerline, both the decaying rate of ground vibration and the influences of the train load, running speed and double-guideway operation mode are gradually reduced. This works could contribute to the evaluation of the vibration annoyance caused by mlsMT operation.

Propagation Characteristics of Vibration in Structure and Site Under Single-point Simple Harmonic Excitation

Propagation Characteristics of Vibration in Structure and Site Under Single-point Simple Harmonic Excitation

Study on Vibration Propagation Characteristics Caused by Segments Joints in Shield Tunnel

In recent years, with the development of urban rail transit, more and more attention has been paid to the vibration problems caused by its operation. As the main form of urban rail transit’s underground construction, the shield tunnel is the first to bear the brunt. However, the existing researches on the vibration of shield tunnel usually take it as a homogeneous barrel and do not consider the impact of its assembly joints on the vibration propagation. In this paper, to study the influence of the joints caused by the shield tunnel’s assembly forms on the propagation of vibration, two finite element models of shield tunnels with different assembly forms are established. The analysis and comparing results of these models show that the joints caused by segment assembly of shield tunnel have obvious hysteresis and reduction effect on the vibration waves and this ability is obviously related to its location. In addition, the ability to weaken the vibration wave is also related to the frequency of the vibration wave.

In-Situ Estimation of Bolt Clamping Force by Utilization of Its Effects on Flexural Vibration Propagation

After a bolt assembling process, non-destructive identification of the clamping force is important to minimize unexpected failure of the assembled joint structures. For in-situ inspection for every parts, a detachable device which allows generation and detection of vibration propagation was proposed in this study. Tone burst excitation was transmitted through the bolted-joint structure. The vibration propagation characteristics depended on the clamping force. With an increase in the clamping force, the surface vibration propagation speed increased. The vibration magnitude decreased due to increasing constraint. A band-pass filter was used to remove noise component. The filtered vibration propagation responses were used in convolutional long short-term memory (CLSTM) training. The performance of CLSTM model was verified through comparison with actual clamping force. With minimal physical influence on the assembled parts, the clamping force of bolted-joint was measured using the surface vibration propagation characteristics.

Field measurement and simplified numerical model for vibration response of subway superstructure

The residents near subway lines may be influenced by subway-induced vibration to a large extent. A simplified numerical modelling technique of the subway superstructure with a high-precision Caughey damping was proposed based on finite element software ANSYS in this paper, aiming to simulate the above-ground vibration response related to residents’ comfort under subway operation. Firstly, the two-stage field measurement of “free field-floor slabs of superstructure”, spanning four years, was carried out on a frame structure building above Guangzhou Metro Line 3. The time domain and frequency domain data of the measured vibration were analysed. A simplified numerical finite element (FE) model of the superstructure was then established, in which a high-precision Caughey damping was constructed using seven control frequencies. The comparative analysis of the simulated and measured results of the building verified that the simplified FE model for simulating the subway superstructure’s vibration response worked well and facilitated engineering applications. Additionally, another superstructure model of the shear wall was established by the same method to explore further the difference in the propagation characteristics of subway-induced vibration in the structure of two different forms. Finally, design recommendations for vibration control of subway superstructure were provided.

Vibration Propagation Characteristics of Micro-Milling Tools

Micro-milling tools are usually used for the 3D precision processing of micro metal parts under ultra-high speed. However, due to the structural characteristics of small scale, variable cross-section, and weak stiffness, the vibration of micro-milling tools is weak and easily mutates, which can potential cause great harm to the stability and machining accuracy of machine tools. To reveal the transfer law of micro-milling tool vibration, guiding the method selection of tool vibration measurement and providing new means for mechanical model verification; firstly, the vibration mechanics model and vibration transfer matrix of the micro-milling tool were established. The vibration propagation characteristics of the micro-milling tool were analysed in contrast with the time domain and frequency domain, taking two representative micro-milling tools, Tool A and Tool B, as examples which with different cross-sections and structural parameters. Secondly, a micro-milling tool vibration measurement experimental system was set up and a sensor array with four optical fibre displacement sensors was used to obtain the vibration displacements at different positions of the tool under pulse and start-stop excitation. Finally, the results show the following: for Tool A, the max vibration displacement of the measurement of point 1 is about 3.5 times of measurement point 2 but near 18 times the measurement of point 3; meanwhile, compared with measurement point 1, the 16.8 kHz signal disappeared in measurement point 2, measurement point 3 and measurement point 4. However, for Tool B, the max vibration displacement of measurement point 1 is about 11.24 times the measurement of point 2; in contrast, the signal strength of the measurement of point 3 and point 4 is too weak to compare and analyse, although there are three resonant frequencies (10.2 kHz, 17.6 kHz, and 26.7 Hz) of Tool B based on the signal of measurement point 1, the 26.7 kHz signal disappeared in measurement point 2. The vibration amplitude of the tool tip decreases rapidly in the process of tool transfer, a bigger ratio cross-section with bigger attenuation of vibration amplitude and smaller size will aggravate this process. This study provides a reference for the selection of measuring points of micro-milling tool vibration displacement.

Ultralow-frequency broadband characteristics of stepwise radial metamaterials

A new type of stepwise radial metamaterial (SRM) with ultralow-frequency and broadband characteristics is proposed in this study. In contrast to the traditional radial metamaterial (TRM), the proposed structure is periodically arranged in a stepwise shape along the radial direction. The propagation characteristics of Lamb waves in the SRM were investigated using the finite element method. For the numerical analysis, the degeneracy between the bands of the SRM was separated, resulting in the opening of the bandgaps in the ultralow-frequency range. The total bandwidth was 75 times that of the TRM, and the wave attenuation ability was increased by more than 70%. The introduction of a stepwise array in the SRM opened up the local resonance and Bragg scattering bandgaps, and as a result, the SRM exhibited ultralow-frequency broadband characteristics. Furthermore, the influences of the structural parameters of the SRM on the bandgap characteristics were discussed. With the increase in the stepped angle, the coupling relationship between the Lamb wave mode and the local resonance was enhanced, which caused the band structure to shift to a lower frequency. In addition, the hole rotation and shape played important roles in the bandgap tuning. Finally, the experimental sample was processed based on the model, and the vibration propagation characteristics were tested to prove its ultralow-frequency broadband characteristics. The proposed shielding approach could provide a better alternative in the field of ultralow-frequency noise reduction and vibration reduction.

Attenuation and propagation characteristics of railway load-induced vibration in a loess area

The long-term vibration caused by the operation of high-speed trains not only reduces the strength and stability of a roadbed but also affects infrastructure such as buildings along the line, resulting in a series of engineering–environmental problems. In this study, field tests were conducted to examine the ground vibrations caused by the operation of the Datong-Xi’an high-speed railway; three different line forms––viaducts, embankments, and embankment culverts––were considered. First, the propagation law and attenuation characteristics of environmental vibration caused by high-speed railways in typical loess areas were analyzed using time-domain and frequency-domain features. Second, based on the Bornitz model and combined with the measured data, the geometric attenuation coefficient and damping attenuation coefficient of the formula are discussed, and the optimized Bornitz model is used to predict the ground vibration caused by high-speed trains in a loess area. The results showed the following: (1) The ground vibration caused by high-speed train operation is a periodic excitation, and there is an obvious superimposition effect at the bogie of the train. The vertical vibration acceleration of the ground surface decays continuously as the distance from the vibration source increases. The dominant frequency also decreased with an increase in distance. (2) The geometric attenuation coefficient of the bridge and embankment sections decrease with an increase in the distance from the vibration source, and the overall attenuation is a power function. Different distances should be regarded as different types of vibration sources, and the damping attenuation coefficient differs at different measurement points. (3) The improved Bornitz model was used to predict ground vibrations caused by the operation of high-speed trains. A comparison with the measured data showed good agreement, explaining the amplification effect in the attenuation of ground vibration.

Study on dynamic response and permanent deformation of the pier and its surrounding sites induced by high-speed train loads in seasonally frozen regions

Vibration induced by high-speed trains (HSTs) is well-known problem, which can deteriorate the embankments, piers and other structures along the railways. Particularly, the problem is more serious due to the freeze-thaw cycle of soil in seasonally frozen regions. In the present study, a series of field experiments are conducted to measure the HST-induced vibration of the pier and its surrounding different sites on the Harbin-Dalian high-speed railway (HSR) in seasonally frozen regions. The characteristics of the vibration in the time and frequency domains are analyzed based on the field measurement results. And the site effects are investigated by the frequency response function (FRF). In addition, the finite element model is established to study the vibration propagation characteristics along the soil surface and interior in different season by the analyzing the variation laws of acceleration peak (Amax) and deviatoric stress (qd), and predict the permanent deformation (Dp) of surface. The results show that the vibration characteristics of the pier and foundation sites are completely different. The Amax decreases in the form of a power function with the distance (R) from the pier in the unfrozen and frozen conditions. Moreover, the distributions of the qd of soil surface in freezing season are obviously different from those in non-freezing season, but the difference between them decreases gradually with the increase of depth (D). The growth speed of Dp decreases with the increase of the time, and the Dp value will eventually trend to a stable value.

Wave propagation analysis of inhomogeneous Multi–Nanoplate systems subjected to a thermal field considering surface and flexoelectricity effects

This paper deals with wave propagation analysis of a viscoelastic exponentially graded multi-nanoplate system (EGMNPS) embedded in visco-Pasternak foundations based on Eringen’s nonlocal theory (ENT) and Kirchhoff plate theory. It is supposed that the EGMNPS is subjected to an external electric field and thermal environment, and the effects of flexoelectricity are also taken into account. Each nano-plate is assumed to be made of viscoelastic and exponentially graded materials (EGM) whose properties vary through the thickness according to an exponential function. A homogenous system of m differential equations of wave motion are derived using Hamilton’s principle and by incorporating surface effects including surface elasticity, surface residual stresses, and surface mass density. The nonlocal governing equations of motion are analytically solved to obtain undamped natural frequencies and damping ratio. A parametric study is carried out to demonstrate the effects of nonlocal parameters, wave number, thermal field, flexoelectricity, surface properties, foundation parameters, and non-homogeneity constant on the thermo-electro-mechanical vibration and wave propagation characteristics of the EGMNPS.

Measurement of Vibration Propagation Characteristics in Tomato Plants for Artificial Pollination by Drone

Measurement of Vibration Propagation Characteristics in Tomato Plants for Artificial Pollination by Drone

Intraocular Pressure Estimation Method Based on Vibration Propagation Characteristics According to Structure Contact

Intraocular pressure (IOP) measurement is one of the basic tests performed in ophthalmology and is known to be an important risk factor for the development and progression of glaucoma. Measurement of IOP is important for assessing response to treatment and monitoring the progression of the disease in glaucoma. In this study, we investigate a method for measuring IOP using the characteristics of vibration propagation generated when the structure is in contact with the eyeball. The response was measured using an accelerometer and a force sensitive resistor to determine the correlation between the IOP. Experiment was performed using ex-vivo porcine eyes. To control the IOP, a needle of the infusion line connected with the water bottle was inserted into the porcine eyes through the limbus. A cross correlation analysis between the accelerometer and the force sensitive resistor was performed to derive a vibration factor that indicate the change in IOP. In order to analyze the degree of influence of biological tissues such as the eyelid, silicon was placed between the structure and the eyeball. The Long Short-Term Memory (LSTM) deep learning algorithm was used to predict IOP based on the vibration factor.

Effects of Silica Fume Addition on Properties of Fresh Mortar

In recent years, concrete structures have tended to be taller and larger than before. With that trend, concrete as a material has diversified, and various kinds have been developed to meet differing quality requirements. In particular, the need for high-strength concrete is increasing. In general, high-strength concrete has a low water-binder ratio, so its workability is inferior to general concrete. Including admixtures such as silica fume is one way to remedy this problem. Previous studies have discussed the quality and hardening characteristics achievable using silica fume. Nevertheless, expected increasing demand for high-strength concrete dictates the need to understand not only its properties when fresh, but also to have an accurate picture of its vibration compaction properties on construction sites. In this study, the effect of adding silica fume on the workability of mortar was investigated by evaluating its fresh properties, plastic viscosity, and vibration propagation characteristics. Changes to mortar’s fresh properties due to pressure were also investigated to clarify its behavior in pumping environments. The study confirmed that the addition of silica fume decreases plastic viscosity and increases vibration propagation characteristics, and that increased plastic viscosity due to pressurization can be reduced.

Vibration wave propagation analysis of a liquid-filled pipe–plate coupled system with multiple supports

This paper analyzes the influence of an elastic plate on the vibration wave propagation of a pipe system. An impedance synthesis method is applied to establish the governing equation of the pipe–plate coupled system by using the force and boundary continuum. The natural frequency and dynamic response are determined by this method. The validity of the theoretical derivation is verified through comparisons with finite element model results. A periodically supported pipe–plate model is set up to analyze the effect of the elastic plate on the vibration bandgap. Finally, through the analysis of the vibration power flow of the coupled system, the vibration propagation characteristics of the pipe–plate configuration are analyzed from the perspective of energy flow. The results presented in this paper provide valuable suggestions for vibration control in pipe systems.

Study on highway dynamic load vibration propagation characteristics in surrounding soil and influence control distance

The dynamic monitoring for the scene of the engineering vehicle dynamic load of the vibration was performed. By developing a subroutine of ABAQUS DLOAD to simulate the process of vehicle traffic, the characteristics of vehicle vibration transmission in soil was analyzed. Based on three different indicators: displacement, acceleration and vibration level, the influence of different speeds and different weights of the vehicle vibration on the surrounding soil and reasonable control distance was analyzed. This paper provides reference and guidance to avoid the influence of traffic dynamic load when designing and constructing.