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

Two-dimensional analysis of open trench as wave barrier to isolate ground vibrations by using in-situ test and semi-analytical BEM in saturated soil

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。

Traffic,machine operations can generate ground vibrations,which can cause distress to adjacent structures and disturb the operation of precision instrument.Generally,these adverse effects of vibrations can be eliminated or prevented by installation of an open trench.This paper focuses on effects of using open trench for the reduction of nearby vibration response generated by the motion of machine foundation in saturated soil.The analysis is accomplished by using the in-situ test and numerical simulation.2D semi-analytical BEM models are established with open trench as active wave barrier to isolate the ground vibrations generated by machine foundation laying on the saturated soil foundation,and the effects of the model parameters on effectiveness of vibration isolation are investigated and discussed.The results show that the open trench can isolate the ground vibrations effectively.The width of open trench has less effect on the screening effectiveness,while increasing the depth of open trench and the distance between the trench and the machine foundation can result in an increase in the screening effectiveness.It is suggested that the trench depth take the value of one Rayleigh wave length,and the open trench should be set around the protected building when the building is far from the machine foundation.Finally,it should be noticed in the design of open trench that resonance of the open trench vibrations isolation system occurs in some certain cases,which decrease the screening efficiency dramatically.