点源激振下地表竖向位移的近—远场分界线  

Borderline between Near and Far Field of Vertical Ground Vibration Caused by Point Excitation at Surface of Elastic Half-Space

作　　者：陈龙珠[1] 严细水[2] 秦建堂[3] 

机构地区：[1]上海交通大学安全与防灾工程研究所,中国上海200030 [2]浙江大学防灾工程研究所,浙江杭州310027 [3]浙江大学城市学院,浙江杭州310015

出　　处：《防灾减灾工程学报》2004年第2期126-130,共5页Journal of Disaster Prevention and Mitigation Engineering

基　　金：国家自然科学基金资助项目 (5 0 0 790 2 7)

摘　　要：在竖向点源作用下 ,地基表面的竖向振动随着源距的增大而衰减 ;但因在近振源区域受体波 (P波、S波 )影响大而在较远处受表面波 (R波 )控制 ,近、远场地表振动的定量衰减规律存在着较大的差异 ,可靠地确定近—远场的分界线便具有重要的学术和应用价值。本文在综述既有研究成果的基础上 ,通过比较Lamb问题的精确解和瑞利近似解 ,较为系统地对这一问题进行了分析 ,结果表明 :由地表竖向位移振幅确定的近—远场分界线较由其相位确定的为远 ,前者源距将随地基泊松比的升高和容许误差的减小而增大且目前的常见取值明显偏小 ,后者与地基泊松比的变化几乎无关。之所以分界线源距随地基泊松比升高而增大 ,主要是由于此时的P波波长增大的影响比S波和R波波长增大的影响要大而造成的。The vertical ground vibration at the surface of an elastic half-space caused by a point excitation will attenuate with distance from the excitation. Based on the classical wave theory, the vibrations are mainly governed by body waves (P and S waves) in the near region and by the surface wave (R wave) in the far field, respectively, which leads to different equations for predicting their vibration intensities varying with distance from the excitation. Through comparing the exact and approximate solutions of the Lamb's problem, the borderline between near and far field of vertical ground vibration at the surface of an elastic half-space is investigated in this paper. Parametrical studies show a greater distance of the mentioned boderline from the excitation determined by the amplitude of displacement than by its phase angle, and that the result by the former will increase with increasing Poisson's ratio of ground and with decreasing allowable error of computation while the result by the latter behaves less correlatively to the Poisson's ratio of ground. Because the wave length of P increases larger than those of S and R waves, it is mainly the P wave that makes the borderline between near and far field farther for an increasing Poisson's ratio or saturation of ground.

关 键 词：弹性地基 点源激振 地表竖向位移 近一远场分界线 

分 类 号：P315.9[天文地球—地震学]