二维地基波阻板隔振分析

本文采用了以薄层法层状半空间基本解答作为格林函数的边界元法,对均质弹性半空间和层状半空间中二维波阻板隔振设计进行了详细的参数分析。分析结果表明,均质弹性半空间和层状半空间内采用波阻板隔振均可取得较好的隔振效果;应保证波阻板具有合理的宽度和较小的埋深,才能得到理想的隔振效果;同时增加波阻板的厚度和模量是提高隔振效果的最有效的2种措施;此外,分层性对波阻板隔振效果也具有一定的影响。     

Gibson地基波阻板隔振分析

采用薄层法层状半空间基本解答作为格林函数的边界元法,对Gibson地基三维波阻板(WIB)隔振设计进行了详细的参数分析.结果表明Gibson地基内采用WIB隔振有较好的隔振效果;应保证WIB具有合理的宽度和较小的埋深;增加WIB的厚度和模量是提高隔振效果的最有效的两种措施;此外地基竖向模量变化对WIB隔振效果也具有一定...     

某高精密设备平台基础隔振措施分析

结合某高精密设备平台基础隔振实际工程,基于UPFs(User Programmable Features)二次开发特点,提出考虑基础-地基-基础动力相互作用计算基础隔振分析的三维有限元方法。该方法首先将动力机器、周围地基以及高精密设备平台基础作为完整的研究对象,通过引入三维紧支黏弹性边界单元模拟半无限地基辐射阻尼效应和远场介质的弹性恢复性能,并在通用有限元软件ANSYS中实现。进而基于最小二乘方法回归分析得到振动衰减关系曲线,通过其与数值分析结果的对比验证计算模型的合理性。最后针对此工程场地条件建立隔振沟减振隔振措施的有限元模型,并对隔振沟影响因素的减振效果进行分析。计算结果表明,隔振沟的位置、深度以及长度是实际工程中需要考虑的重要因素,对其进行合理的选取可获得较好的隔振效果。     

层状地基空沟被动隔振分析

基于薄层法在研究层状介质中波的传播问题的高效性,边界单元法处理无限域问题的精确性,结合两者提出层状地基二次形函数薄层法基本解答, 建立了基于层状半空间薄层法位移基本解答的半解析动力边界元法,可以有效的分析多层场地的动力问题,解决土-结构动力相互作用问题.同时对上软下硬的典型层状地基中的空沟被动隔振效果进行了详细的分析.研究表明:对于上软下硬地基中空沟被动隔振,为取得与匀质弹性半空间中连续屏障隔振同样的效果,需要更深的深度,同时振幅衰减曲线会出现明显的振荡现象;为使隔振效果满足Richart要求,当表层土归一化深度H＜1.0时,空沟归一化深度T应大于1.3,而1.0≤H≤2.0时,T应当大于1.8.     

列车荷载作用下准饱和地基波阻板隔振特性研究

基于Biot波动方程,推导准饱和多孔介质控制方程,建立高铁列车-准饱和地基-波阻板(WIB)隔振模型,研究高铁列车移动荷载作用下准饱和地基中WIB隔振性能.以秦沈客运专线工程实例进行算例分析,研究饱和度对WIB隔振性能影响规律及其力学机制,分析不同列车速度、不同饱和度条件下水平x方向、竖向z方向位移振幅衰减系数及频谱曲...     

地铁列车荷载作用下Duxseal-WIB隔振性能数值分析

城市轨道交通快速便捷的同时,地铁运行产生的环境振动问题也日益突出。Duxseal作为一种工业填料,具有良好的阻尼性能并能吸收振动反射能,将其运用到地铁隔振中,提出一种带孔波阻板填充Duxseal(DXWIB)的隔振方法。通过建立三维ABAQUS有限元模型,对比分析波阻板(WIB)、蜂窝状波阻板(HWIB)和DXWIB的隔振效果,讨论DXWIB埋置深度及厚度对隔振效果的影响,并分析基床表层和地面的振动规律。计算结果表明:DXWIB的隔振效果最优,而WIB与HWIB的隔振效果相近;DXWIB在埋深0.5 m厚度0.8 m时隔振效果最佳;基床表层的振动规律表现为由振源向两侧横向传播中,加速度整体呈衰减趋势,而在地面传播过程中,加速度峰值呈先增大后减小再增大的趋势,在距轨道中轴线20 m和50 m处出现局部放大效应。     

高速铁路空沟隔振措施隔振效果的有限元分析

高速铁路引起的振动对周边环境的影响是不容忽视的,需要采取相应的工程对策来减小其危害。采用空沟隔振施工方便,隔振效果能得到保证,故在实际工程中得到广泛应用。本文使用大型通用有限元软件ABAQUS对空沟隔振的效果进行数值分析。计算模型采用无限元和黏弹性边界吸收振动波,减小边界反射波对计算结果的影响;文中引入参数ARF来评价空沟的隔振效果,在此基础上分析不同的空沟尺寸及不同的荷载频率对隔振效果的影响,可供设计者参考。     

高速铁路空沟隔振措施隔振效果的有限元分析

高速铁路引起的振动对周边环境的影响是不容忽视的,需要采取相应的工程对策来减小其危害。采用空沟隔振施工方便,隔振效果能得到保证,故在实际工程中得到广泛应用。本文使用大型通用有限元软件ABAQUS对空沟隔振的效果进行数值分析。计算模型采用无限元和黏弹性边界吸收振动波,减小边界反射波对计算结果的影响;文中引入参数ARF来评价空沟的隔振效果,在此基础上分析不同的空沟尺寸及不同的荷载频率对隔振效果的影响,可供设计者参考。     

饱和地基中空沟近场隔振的现场试验与二维半解析边界元分析

动力机器运行和车辆行驶等会产生振动污染,危及邻近建筑物安全和干扰精密仪器设备正常运行等。这些振动污染可通过在地基中设置空沟的方式来降低或消除。针对饱和地基上明置动力机器基础的环境振动影响及空沟近场隔振问题,进行了饱和地基上空沟近场隔振的现场试验,并对试验结果进行了无量纲化分析;基于饱和土半解析边界元法,分别推导了动力机器基础环境振动影响和空沟近场隔振的边界元方程;在此基础上,详细研究了空沟对动力机器基础振动影响的隔振效果,分析了空沟深度、宽度和距振源距离对其隔振效果的影响。结果表明:空沟能够有效的降低动力机器基础的环境振动影响;空沟宽度对其隔振效果影响相对较小,而空沟深度对其隔振效果影响较大,为获得较好的隔振效果,空沟深度建议取1倍Rayleigh波波长;空沟距振源距离对其隔振效果也有较大影响,距离越远则隔振效果也越好,当被保护建筑距振源较远时,建议空沟在被保护建筑附近设置。此外,在某些特殊情况下,空沟隔振系统会由于共振现象而出现隔振效果劣化的现象,在工程设计中应予以注意。     

三维层状地基空沟主动隔振分析

基于薄层法在研究层状介质中波的传播问题的高效性、边界单元法处理无限域问题的精确性,结合二者的优点提出三维层状地基薄层法基本解答,建立了基于三维层状半空间薄层法位移基本解答的半解析动力边界元法。该方法可有效的分析多层场地的动力问题,解决土-结构动力相互作用问题。同时分别对粘弹性上软下硬地基及上硬下软地基的三维空沟主动隔振进行了详细的分析。结果表明,两种情况下采用空沟屏障隔振均可以取得一定的隔振效果;同时,地基分层参数对空沟隔振体系的隔振效果影响显著。     

Field experiments on wave propagation and vibration isolation by using wave barriers

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.     

高速铁路桩板结构对瑞利波的被动隔震试验研究

为研究高速铁路桩板结构被动隔震效果,以减震率作为隔震性能评价指标。通过模型试验分析不同几何参数的桩板结构隔震性能,并绘制减震率等值线图以描述其隔震区域。基于试验得到以下结论：桩板结构可以有效阻隔瑞利波,增加桩长、桩径和承载板厚度,并减小埋深与桩间距,可以提高隔震性能并增大有效隔震面积。减震率增长幅度随桩长、桩径和承载板厚度增大而减小,故桩径和桩间距参数宜控制在0.33至0.67之间,桩长参数宜控制在0.40至0.80之间,且应尽可能减小埋深。当砼使用方量相同时,隔震效果从强到弱依次为：桩长、承载板厚度和桩径。     

Field experiment and numerical study on active vibration isolation by horizontal blocks in layered ground under vertical loading

In this paper, a series of field experiments were carried out to investigate the active vibration isolation for a surface foundation using horizontal wave impedance block (WIB) in a multilayered ground under vertical excitations. The velocity amplitude of ground vibration was measured and the root-mean-square (RMS) velocity is used to evaluate the vibration mitigation effect of the WIB. The influences of the size, the embedded depth and the shear modulus of the WIB on the vibration mitigation were also systematically examined under different loading conditions. The experimental results convincingly indicate that WIB is effective to reduce the ground vibration, especially at high excitation frequencies. The vibration mitigation effect of the WIB would be improved when its size and shear modulus increase or the embedded depth decreases. The results also showed that the WIB may amplify rather than reduce the ground vibration when its shear modulus is smaller or the embedded depth is larger than a threshold value. Meanwhile, an improved 3D semi-analytical boundary element method (BEM) combined with a thin layer method (TLM) was proposed to account for the rectangular shape of the used WIB and the laminated characteristics of the actual ground condition in analyzing the vibration mitigation of machine foundations. Comparisons between the field experiments and the numerical analyses were also made to validate the proposed BEM.     

Modelling of pile wave barriers by effective trenches and their screening effectiveness

The three-dimensional problem of isolation of vibration by a row of piles is studied numerically on the basis of a model replacing the row of piles by an effective trench in order to reduce the modelling complexity. The analysis is accomplished with the aid of an advanced frequency domain boundary element method, which is used for both the infilled trench and the soil medium in conjunction with a coupling procedure based on enforcement of equilibrium and compatibility at the trench–soil interface. Linear elastic or viscoelastic material behaviour is assumed for both the piles and the soil. The piles can be tubular or solid and have circular or square cross-section. The vibration source is a vertical force, harmonically varying with time, and the row of piles acts as a passive wave barrier. The effective trench model is constructed by invoking well known homogenization techniques used in the mechanics of fibre-reinforced composite materials, and its accuracy is compared against a rigorous boundary element analysis modelling each pile separately in full contact with the soil medium. On the basis of the effective trench model, the screening effectiveness of a row of piles is studied through parametric studies.     

Three-dimensional analysis of rows of piles as passive barriers for ground vibration isolation

This paper presents a theoretical study on the ground vibration isolation efficiency by multi-rows of piles as passive barrier in a three-dimensional context. Integral equations governing Rayleigh wave scattering are derived according to the Green's solution of Lamb problem. The integral equations are solved accurately and efficiently with an iteration technique. They are used to predict the complicated Rayleigh wave field that is generated by a number of irregular scatterers embedded in an elastic half-space solid. The method is verified with a numerical solution available in the literature for a simplified Rayleigh wave scattering problem. Passive isolation effectiveness of ground vibration with two or three rows of small piles is further studied in detail. Effects of relevant parameters on the effectiveness of vibration isolation are analyzed and presented.     

连续型隔振屏障在高速铁路环境振动问题治理中的应用研究

为探究高速铁路两侧隔振屏障隔振效果，采用有限元与无限元边界结合的方式进行分析，研究不同连续型隔振屏障及布置形式对隔振效果的影响。通过现场试验与同尺寸、同属性有限元模型对比试验，验证有限元模型合理性。计算结果表明:不同连续型隔振屏障中，空沟隔振效果最优，空沟隔振措施适合高速列车隔振；隔振屏障宽度为0.6～2.5倍波长时，其对隔振效果的影响较小，随着宽度的改变，隔振效果变化幅度较小；隔振屏障深度为3.8～15.2倍波长时，其对隔振效果的影响较明显，随着深度的增加，隔振效果增强；屏障位置对隔振效果的影响较大，建议屏障应靠近路基布置；连续型隔振屏障对高频的隔振效果优于低频。     

双排隔振屏障对振动波的阻隔作用及动力响应分析

本文采用模拟试验的方法,对分层土地基中双排隔振屏障对振动波的动力响应进行了探讨,并研究了桩长与土层分界面位置关系、激振频率对其隔振效果的影响作用,得出结论:（1）屏障前振动强度远大于屏障后振动强度,并随着振源距、激振频率、桩长的增加而下降,且屏障前出现明显振动增强现象,在激振频率80 Hz时产生振动峰值,振动强度在高频时基本稳定,继续增加激振频率,振动强度并不会发生明显变化。（2）屏障后中线左右2倍桩长范围内为整个隔振区域的薄弱区,其他区域则由包络线围成一个封闭有效隔振区。（3）屏障对中频和高频有更好的隔振效果,且桩长越大有效隔振面积越大,当桩长超过土层分界面时,有效隔振面积可达到53.25%～69.78%,但此时有效隔振面积增幅由原来的14.29%下降到11.64%,增幅降低了约3%。（4）未设屏障区振动强度较小,随激振频率小范围内浮动,在激振频率为30 Hz和80 Hz时取得振动峰值,且随着屏障布置方向减小,即靠近屏障一侧振动强度较强,远离屏障一侧振动强度较弱。     

Attenuation of ground vibrations using in-filled wave barriers

Ground vibrations generated by construction activities can adversely affect the structural health of adjacent buildings and foundations supporting them. Therefore propagation and rate of attenuation of construction induced ground vibrations is important during construction activities, particularly in urban areas where constructions are carried out in the vicinity of existing structures. In practice wave barriers are installed in the ground to mitigate the ground vibration propagation and hence to minimise the effect of ground vibrations on surrounding structures. Different types of fill materials such as bentonite, EPS geofoam and concrete are used in constructing wave barriers. In this study, a three-dimensional finite element model is developed to study the efficiency of different fill materials in attenuating ground vibrations. The model is first verified using data from full scale field experiments, where EPS geofoam has been used as a fill material in wave barriers. Then the same model has been used to evaluate the efficiency of open trenches, water filled wave barriers and EPS geofoam filled wave barriers on attenuation of ground vibrations. EPS geofoam is found to be the most efficient fill material, providing attenuation efficiency closer to open trenches. The efficiency of EPS geofoam and water filled wave barriers can be significantly increased by increasing the depth of the wave barrier.