【作者】 陈文；

【导师】 杨永斌；

【作者基本信息】 重庆大学 ， 土木工程， 2021， 硕士

【摘要】 地铁在方便人们出行的同时,其引发的环境振动问题也不容忽视。列车诱发的环境振动会干扰沿线居民的正常生活,影响精密仪器的使用,甚至导致古建筑物开裂。因此,研究地铁振源引致地表振动的隔振措施具有十分重要的现实意义。针对传统2维方法精度不足、3维方法效率低等问题,本文考察了Yang提出的2.5维有限/无限元法在地铁引致地表振动及隔振分析中的适用性,主要研究内容包括:(1)利用三重傅里叶变换方法求解了移动荷载作用下半无限空间动力响应的理论解,包括位移、速度、加速度和应力-应变响应的理论解;(2)利用理论解验证了2.5维数值解的正确性,并利用2.5维数值方法深入研究了移动荷载引致土体的应力波传播特性;(3)将2.5维方法拓展应用于研究地铁振源引致地表振动问题,对沟渠的隔振效果进行了参数化分析,考察了沟渠深度、宽度和位置等因素的影响规律,并研究了填充沟渠不同填充材料的影响规律。基于上述研究工作,得出以下结论:(1)移动荷载下土体剪应力受“临界速度效应”影响最大,当荷载速度达到临界速度时,其最大值可达竖向正应力的0.8倍;(2)荷载速度超过临界波速时,应力响应可以观察到马赫波现象,且无自振频率荷载下,波传方向具有固定传播角;自振频率荷载下,波传方向无固定传播角;(3)地铁荷载引致的地表振动,20Hz以上较高频段衰减较快,0～20Hz频段衰减较慢;随着距离增加,地表振动总体逐渐减小,但局部会发生振动放大现象;(4)空沟渠隔振时沟前会发生振动放大现象,但其后方整体隔振效果显著;空沟渠的隔振效果受深度影响最大,且对10Hz以上较高频段具有明显的隔振效果,而对0～10Hz低频的隔振效果较差;(5)填充沟渠隔振时沟前振动放大较小,而沟后仅在一倍沟深范围内隔振效果显著;填充沟渠隔振效果受宽度影响较大,沟渠越宽,隔振效果越好;(6)填充沟渠的隔振效果受填充材料影响明显,一定范围内,刚性材料越刚,隔振效果越好,柔性材料越柔,隔振效果也越好;对10～20Hz较低频段的隔振效果,刚性材料要优于柔性材料。更多还原

【Abstract】 Subway traffic is convenient for people to travel,while the environmental vibration caused by trains cannot be ignored.The environmental vibration induced by the trains will interfere with the normal life of the residents along the routes,prevent the precision instruments from working properly,and even cause the cracking of ancient buildings.Therefore,it is of great practical significance to study the surface vibration isolation measures caused the subway trains.Due to the traditional two-dimensional(2D)method cannot precisely simulate the speed effect,whereas a fully three-dimensional(3D)model is too time-consuming in practice,a 2.5D finite/infinite element approach is presented by Yang to study the isolation of surface vibration caused by the subway.The following studies have been carried out:(1)By the triple Fourier transformation method,the analytical solutions of the steady-state dynamic response of the half space subjected to a moving load,including the responses of displacement,velocity,acceleration,and the stress-strain.(2)The 2.5D numerical solution is compared with the theoretical solution to ensure the accuracy of numerical method.The dynamic response of the semi-infinite space subjected to a moving load has been studied by the 2.5D finite/infinite element approach.(3)The application of the 2.5D method is extended to study the surface vibration caused by underground trains.The parameter analysis is carried out on the isolation effect of the ground vibration of the trenches induced by the subway.Factors such as depth,width and position of the trenches,as well as load speed,are taken into account.The effects of in-filled trenches with different materials are also considered.Based on the research work above,the following conclusions are drawn:(1)the shear stress is affected by the "Critical velocity effect" mostly,which reaches a maximum of 0.8 times the vertical stress when the load speed reaches critical speed.(2)The Mach wave effect can be observed in stress response when the load velocity exceeds the critical wave velocity.The transmission direction of waves has a fixed propagation angle with the load without self-frequency.But it does not with the load with self-frequency.(3)The frequency of ground-borne vibration induced by subways ranges from 0 to 60 Hz.Response above 20 Hz decays more quickly,that in the range of 0 to 20 Hz decays slowly.As the distance increases,the ground-borne vibration decreases gradually,but the vibration amplification occurs locally.(4)When the open trench is set up,vibration amplification occurs in front of it.The overall vibration isolation effect on its rear is significant.The vibration isolation effect of the open trench is greatest affected by depth,and the vibration isolation effect is obvious for higher frequency bands above 10 Hz,while it is poor for 0 to 10 Hz low frequency.(5)Vibration amplification is smaller in front of the in-filled trench,The vibration isolation effect is significant only within twice the depth of the in-filled trench.The vibration-isolation effect of the in-filled trench is greatly affected by its width,and the wider the in-filled trench,the better the vibration-isolation effect.(6)The vibration isolation effect of the in-filled trench is obviously affected by the materials.To a certain extent,the more rigid material,the better the vibration isolation effect,the softer the flexible material,the better the vibration isolation effect.For vibration isolation in the lower bands of 10 ～ 20 Hz,rigid materials are superior to flexible materials.更多还原