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1.
The isolation of vibrations from the surroundings is one of the important problems in the design of machine foundations. The use of open trenches, infilled trenches, single and multiple pile rows have been widely studied. In this paper, the vibration screening efficiency of an inclined secant micro-pile wall positioned as an active vibration barrier is investigated. The study is performed using three-dimensional time domain finite element analyses. Various parameters such as barrier depth, inclination, barrier distance and load excitation frequency were studied. The results show that inclined secant micro-pile walls are a viable vibration isolation option for a multitude of vibration problems. It is shown that varying barrier inclination angle from 90° to 120° improved vibration isolation performance as high as 44% relative to the vertical barrier for the active isolation case. The effectiveness of the barrier increases as its depth increases and also as the excitation frequency increases. The orientation of the inclined barrier towards or against vibration source is shown to be a fundamental design consideration. 相似文献
2.
为研究双线地铁运营时隔振沟的减振效果,基于2.5维有限元法建立双线地铁列车-轨道-地基土体耦合分析模型。模型克服现有研究将轨道结构简化为弹性地基欧拉梁的缺陷,引入实际钢轨动力学参数,实现双线地铁列车荷载下隔振沟对周围地基的隔振效果分析,比较空沟、填充沟两种不同隔振措施的减振特性,并对填充沟隔振影响因素进行系统的参数分析。研究结果表明:双线运营地铁荷载下,空沟隔振作用体现在沟后范围内,填充沟减振范围更广且效果更好,相比空沟更具工程实用性;填充沟在沟深较小时也能发挥良好的减振作用,增大沟深、沟宽均可有效提高减振效果。研究成果可为今后双线地铁隔振设计与施工提供有益参考。 相似文献
3.
在研究轨道振动荷载的产生机理基础上,归纳出一个能够涵盖速度、线路不平顺、轮重、轨枕对轮载的分散作用等因素在内的轨道荷载解析表达式,以此作为输入施加到土体模型上,利用ANSYS模拟地基土在轨道移动荷载作用下的三维瞬态弹塑性反应。通过计算得到土体不同位置位移和加速度时程曲线,并得出如下结论:荷载刚施加时地面位移会有一个突变,但是随着荷载的移动会达到一个稳定值,并随着水平面内远离轨道,该值逐渐衰减;荷载刚刚施加时加速度会有一个突变值,随着荷载的移动逐渐趋于零。轨道机车速度对竖向方向的位移和加速度影响不大。 相似文献
4.
Dynamic analysis of slab track on multi-layered transversely isotropic saturated soils subjected to train loads 总被引：1，自引：0，他引：1
The dynamic responses of a slab track on transversely isotropic saturated soils subjected to moving train loads are investigated by a semi-analytical approach. The track model is described as an upper Euler beam to simulate the rails and a lower Euler beam to model the slab. Rail pads between the rails and slab are represented by a continuous layer of springs and dashpots. A series of point loads are formulated to describe the moving train loads. The governing equations of track-ground systems are solved using the double Fourier transform, and the dynamic responses in the time domain are obtained by the inverse Fourier transform. The results show that a train load with high velocity will generate a larger response in transversely isotropic saturated soil than the lower velocity load, and special attention should be paid on the pore pressure in the vicinity of the ground surface. The anisotropic parameters of a surface soil layer will have greater influence on the displacement and excess pore water pressure than those of the subsoil layer. The traditional design method taking ground soil as homogeneous isotropic soil is unsafe for the case of RE 1 and RG 1, so a transversely isotropic foundation model is of great significance to the design for high train velocities. 相似文献
5.
The paper proposes an alternative approach to dispersion curves to analyse resonant phenomena in the context of wave propagation induced by a harmonic load moving over a railway track coupled to a multilayered poroviscoelastic medium. It consists of a shading representation of the spectral response in the frequency–wavenumber domain. Unlike the usual dispersion curves, it can take into account both the damping and the coupled system. Specific attention is paid to the first mode contribution. Critical ranges are determined from this shading representation: (i) for the load frequency when the load moves at a fixed constant speed, and (ii) for the load speed when the load frequency is constant. Both sub-Rayleigh and super-Rayleigh regimes are studied. 相似文献
6.
为研究层状地基的分界面对于空沟隔振效果的影响,采用模型试验,选取三种不同深度的空沟,分别为小于分界面深度和等于分界面深度以及超过分界面深度的三种深度,分析在改变空沟宽度、空沟位置(固定振源即传感器位置,仅改变空沟所处位置)以及激振频率时对三种深度空沟隔振效果的影响。结果表明:当宽度和激振频率发生改变时,深度等于土层分界面处深度的空沟隔振效果变化最不明显;当宽度和空沟位置发生改变时,沟深小于分界面深度的空沟受到的影响最为明显;在激振频率的改变下时,沟深大于土层分界面深度的空沟所受影响最大;当固定其余参数,逐渐增加空沟深度时,深度在变化到分界面处时会有Ar值发生增加现象,该现象受到激振频率影响,激振频率越低,则上升幅度越大,低频的上升区间也最长,即Ar值从出现上升趋势至恢复减小趋势的距离为上升区间。综上结论,在选择隔振沟时应注重上述因素的影响,合理设计隔振沟,使其达到最佳隔振效果。 相似文献
7.
Shuguang Zhang Xinbiao Xiao Zefeng Wen Xuesong Jin 《Soil Dynamics and Earthquake Engineering》2008,28(8):662-673
The paper reviews some important published papers on the effects of railway track imperfections on track dynamic behavior, and investigates the effect of unsupported sleepers on the normal load of wheel/rail in detail through a numerical simulation. The numerical simulation is based on a coupling dynamic model of vehicle–track. In the model, the vehicle is modeled as a multi-body system, and the track is considered as a 3-layer model with rails, sleepers, and ballast masses. Each rail of the track is modeled with a Timoshenko beam resting on discrete sleepers. The lateral, vertical, and torsional deformations of the beam are taken into account. The sleepers are assumed to move backward at a constant speed to simulate the vehicle running along the track at the same speed, and therefore such a track model can consider the effect of the discrete support by sleepers on the coupling dynamic behavior of the vehicle and track in the simulation. In calculating the coupled vehicle and track dynamics, Hertzian contact theory and the theory by Shen et al. are, respectively, used to calculate the normal forces and the creep forces between the wheels and the rails. The motion equations of the vehicle–track are solved by means of an explicit integration method. A nonlinear spring and a nonlinear damper are used to simulate a gap between the unsupported sleeper and the ballast mass. The numerical results obtained indicate that the gaps between the unsupported sleepers and ballast masses have a great influence on the normal load of the wheel and the rail. 相似文献
8.
Vibration isolation of structures from ground-transmitted waves by open trenches in isotropic, linearly elastic or viscoelastic soil with a shear modulus varying continuously with depth is numerically studied. Both an exponential and a linear shear modulus variation with depth are used in this work. Waves produced by the harmonic motion of a rigid surface machine foundation are considered. The problem is solved by the frequency domain boundary element method employing the Green's function of Kausel-Peek-Hull for a thin layered half-space. Thus only the trench perimeter and the soil-foundation interface need essentially to be discretized. The proposed methodology is first tested for accuracy by solving two Rayleigh wave propagation problems in nonhomogeneous soil with known analytical solutions and/or for which experimental results are available. Then the method is applied to vibration isolation problems and the effect of the inhomogeneity on the wave screening effectiveness of trenches is studied. 相似文献
9.
This paper explores dynamic soil–bridge interaction in high speed railway lines. The analysis was conducted using a general and fully three-dimensional multi-body finite element–boundary element model formulated in the time domain to predict vibrations caused by trains passing over the bridge. The vehicle was modelled as a multi-body system, the track and the bridge were modelled using finite elements and the soil was considered as a half-space by the boundary element method. The dynamic response of bridges to vehicle passage is usually studied using moving force and moving mass models. However, the multi-body system allows to consider the quasi-static and dynamic excitation mechanisms. Soil–structure interaction was taken into account by coupling finite elements and boundary elements. The paper presents the results obtained for a simply supported short span bridge in a resonant regime under different soil stiffness conditions. 相似文献
10.
Diagnosis and prediction of vibration from railway trains 总被引：7，自引：0，他引：7
In the North West of France, more particularly in the region of the Somme Bay, where the ground is constituted mainly of peat, observation of the surface of the soil near railway tracks has revealed high levels of displacement. This paper, contains a prediction model and diagnosis of vibration near the track. A model of a railway track on layered ground subjected to a moving train has been built and the calculation method uses Fourier transform formalism for a semi-analytical solution in the wave number domain. It includes all elements of the track and allows a parametric analysis of its different elements and evaluation of vertical displacement according to the speed, weight and composition of each train. The diagnosis has been performed with in situ measurements and with the aim of the validation of the model. A parameter study of the ground undertaken by seismic measurements shows a critical speed close to 100 m/s while the studied trains are moving with sub-Rayleigh speeds. Measurements give us a lot of information about lateral and vertical acceleration on the soil's surface and parts of the track. For high speeds and freight trains, displacement reaches more than 10 mm. 相似文献
11.
Efficiency of trenches along railways for trains moving at sub- or supersonic speeds 总被引：2，自引：0，他引：2
A full 3D analytical approach is adopted to account for trenches on one or both sides close to a railroad. Low-frequency ground vibrations are investigated due to the passing of trains, and open trenches are used as wave barriers. The modelling technique is based on Fourier transforms and Fourier series. The ground is modelled as a layered semi-infinite domain and the embankment with finite layers. The trenches are obtained by simulating the upper surface layer with two or three finite rectangular regions with appropriate widths. A particular boundary condition is adopted at the vertical sides of all finite regions to enable the solution procedure. Rails and sleepers are accounted for with Euler–Bernoulli beams and an anisotropic Kirchhoff plate with transversal isotropy. The wheel loads from the boogie wheel pairs of the train are simulated as moving forces. Hence, no irregularities in rails or wheels are accounted for. 相似文献
12.
The use of ballastless slab track is significantly increasing in HST line technology. This development is due to some structural and operational advantages over ballasted track. In addition, floating slab tracks can be used to control ground-borne vibrations generated by surface and underground rail transportation systems. In this paper, a general and fully three dimensional multi-body-finite element-boundary element model is used to study vibrations due to train passage on ballast and non-ballast tracks. The vehicle is modelled as a multi-body system, the track, in both cases, using finite elements and the soil is represented using boundary elements. The three components of the load are considered; the quasi-static excitation (force generated by moving axle loads), the parametric excitation due to discrete supports of the rails and the excitation due to wheel and rail roughness and track unevenness. Track receptances are computed for both track systems and vibrations induced by high-speed train passage at the track and the free-field are evaluated for different train speeds. Soil behaviour changes significantly with the track system. Finally, a floating slab track is studied to show how this type of solution leads to a significant vibration reduction for surface tracks. 相似文献
13.
Model testing in laboratory, as an effective alternative to field measurement, provides valuable data to understand railway׳s dynamic behaviors under train moving loads. This paper presents comprehensive experimental results on track vibration and soil response of a ballastless high-speed railway from a full-scale model testing with simulated train moving loads at various speeds. A portion of a realistic ballastless railway comprising slab track, roadbed, subgrade, and subsoil was constructed in a larger steel box. A computer-controlled sequential loading system was developed to generate equivalent vertical loadings at the track structure for simulating the dynamic excitations due to train׳s movements. Comparisons with the field measurements show that the proposed model testing can accurately reproduce dynamic behaviors of the track structure and underlying soils under train moving loads. The attenuation characteristics of dynamic soil stresses in a ballastless slab track is found to have distinct differences from that in a ballasted track. The model testing results provide better understanding of the influence of dynamic soil–structure interaction and train speed on the response of track structure and soils. 相似文献
14.
车辆-轨道系统振动响应分析--Timoshenko梁与Euler梁轨道模型的比较 总被引：1，自引：0，他引：1
近年来，铁路的高速化、高运量化以及轻微的地震灾害等因素加速了轨道结构的沉降或变形，导致车辆轨道系统振动的加剧。本文运用车辆-轨道耦合动力学理论，编制了基于Timoehenko梁钢轨模型的车辆-轨道耦合振动仿真分析软件，分析了车辆-轨道系统的垂向振动特性，并与基于Euler梁模型的VICT软件的仿真结果进行了比较分析。结果表明：仿真结果与VICT的仿真结果基本一致，但在较高频域，前者能更好地反映轮轨系统的高频特性。因而，在研究轮轨高频振动及轮轨噪声时。采用Timoshenko梁钢轨模型更具合理性。 相似文献
15.
Three-dimensional simulation of track on poroelastic half-space vibrations due to a moving point load 总被引：1，自引：0，他引：1
An analytical approach is used to investigate dynamic responses of a track system and the poroelastic half-space soil medium subjected to a moving point load under three-dimensional condition. The whole system is divided into two separately formulated substructures, the track sub-system and the ground. The ballast supporting rails and sleepers is placed on the surface of the ground. The rail is modeled by introducing the Green function for an infinitely long Euler beam subjected to the action of the moving point load and the reaction of sleepers represented by a continuous mass. Using the double Fourier transform, the governing equations of motion are then solved analytically in the frequency–wave-number domain. The time domain responses are evaluated by the inverse Fourier transform computation for a certain load velocities. Computed results show that dynamic responses of the soil medium are considerably affected by the fluid phase as well as the load velocity. 相似文献
16.
介绍了使用路检车装载探地雷达(Ground Penetrating Radar)对铁路路基检测的原理,结合野外探测过程中对测量深度、精度和行车速度的要求,给出了GPR现场工作测线布置的原则,理论上给出天线中心频率、时窗、采样率、测量点距的计算公式.讨论了连续测量和离散测量的关系,考虑到连续测量时水平精度的要求,给出行车速度必须满足的两个条件,从而确定行车速度的上限.为保证野外检测工作的顺利进行,结合实际情况给出了GPR工作参数的设计原则和流程. 相似文献
17.
A simplified analytical model including the coupled effects of the wheel–rail–soil system and geometric irregularities of the track is proposed for evaluation of the moving train load. The wheel–rail–soil system is simulated as a series of moving point loads on an Euler–Bernoulli beam resting on a visco-elastic half-space, and the wave-number transform is adopted to derive the 2.5D finite element formulation. The numerical model is validated by published data in the literature. Numerical predictions of ground vibrations by using the proposed method are conducted at a site on the Qin-Shen Line in China. 相似文献
18.
Erkan Çelebi Seyhan Fırat Günay Beyhan İlyas Çankaya İsa Vural Osman Kırtel 《Soil Dynamics and Earthquake Engineering》2009
In this paper, the obtained results from the experimental studies describe the basic characteristics of wave propagation and ability of possible measures to reduce the impact of soil vibrations on structural response for both active and passive isolation cases. A series of field tests on the foundation vibrations generated by electrodynamic shaker are performed to examine the screening efficiency of open and in-filled trench barriers which are constructed for full-scale measurement. From field measurements of amplitude with and without the barrier, the amplitude reduction ratio is estimated at different points of interest. Wave propagating characteristics and frequency-dependent screening effects of the wave barriers are investigated according to various isolation material stiffnesses. The remarkable outcomes from these experimental studies can be briefly generalized as follows: backfilled trench with softer material than soil is more effective for the passive isolation than the active one. The reduction effects of wave barriers depend on the frequency of vibration source for both passive and active isolation cases. In-situ measurements confirm that vibration screening systems using open or in-filled trench barriers can be applied as a reduction measure for soil vibrations due to a moving load which is considered as stationary wave source in this problem. 相似文献
19.
基于轨道结构-路基-地基动力相互作用理论,建立考虑地震-列车移动荷载耦合输入的轨道结构-路基-地基动力学模型,研究高速铁路路基及轨道在耦合荷载作用下的振动响应问题。通过编制DLOAD子程序并与ABAQUS有限元计算程序联立,实现地震荷载与列车移动荷载耦合作用的施加,以高速铁路桩承式路基及自由式路基为研究对象,对地震-列车移动荷载耦合作用下两种路基系统的动力响应进行数值计算并比较两者的振动响应差异。结果表明,耦合荷载对桩承式路基动力响应影响显著,该荷载作用下桩承式路基会发生共振现象,使得桩承式路基中轨道和路基振动位移幅值均大于自由式路基的振动位移幅值;桩承式路基不会影响路基系统的振动频率,但会改变路基系统的振动大小,桩承式路基中轨道X方向加速度、路肩边及路基坡脚处的竖向加速度分别减小6.2%、50%、28.6%。 相似文献
20.
Dynamic effects of moving loads on road pavements: A review 总被引：3，自引：0，他引：3
This review paper deals with the dynamic response of road pavements to moving loads on their surface. The road pavement can be modeled as a beam, a plate, or the top layer of a layered soil medium. The foundation soil can be modeled as a system of elastic springs and dashpots or a homogeneous or layered half-space. The material behavior of the pavement can be elastic or viscoelastic, while that of the foundation layers elastic, viscoelastic, water-saturated poroelastic or even inelastic. The loads are concentrated or distributed of finite extent, may vary with time and move with constant or variable speed. The analysis is done by analytical, analytical/numerical and purely numerical methods, such as finite element and boundary element methods, under conditions of plane strain or full three-dimensionality. A number of representative examples is presented in order to illustrate the problem and the methods of analysis, demonstrate the dynamic effects of moving loads on the layered soil medium and indicate the implications of the results on road and airport pavement design. 相似文献