单排非连续刚性桩屏障对弹性波的隔离

对于人工振动产生的弹性波,如果刚性桩屏障埋置足够深,在分析其对弹性波的隔离效果时,可以简化为固定的刚性桩屏障对弹性波的多重散射问题。采用波函数展开法将入射波和散射波的势函数展开成Fourier-Bessel函数的级数形式,根据Graf加法定理和固定刚性桩周边土体的边界条件得到散射系数的理论解,引入了无量纲位移(屏障后土体中由入射波和散射波产生的总的位移幅值与入射波在该处单独产生的位移幅值之间的比值)和透射系数(屏障后屏障宽度范围内的无量纲位移的几何平均值)的概念,绘制了屏障后一定范围内的无量纲位移等值线,及屏障后某处的透射系数随桩净距(相邻两桩之间的空隙)的变化曲线,通过分析这些曲线得出,对于三种入射体波(SV波、P波和SH波):屏障后越靠近屏障,隔离效果越好;当桩净距接近一倍桩半径时,屏障的整体隔离效果达到最好。

Isolation of Elastic Waves by Discontinuous Barrier Composed of a Row of Rigid Piles

The problems of isolation of the elastic waves caused by man-made vibrations by means of discontinuous barrier composed of a row of rigid piles can be simplified as multiple scattering problems of elastic waves if the rigid piles were embedded deeply enough. The potential functions of incident and scattered waves were expanded to the series of Fourier-Bessel functions by using of the expansion method of wave functions.Theoretical solutions of the scattering coefficients were obtained according to Graf's addition theory and the boundary conditions of the soil adjacent to the fixed rigid piles. By truncating the terms over a finite namber of orders, the curves of the normalized displacements, which is the ratio of the sum displacement caused by the incident and scattering waves in some place behind the barrier to the displacement only caused by incident waves with no barrier were achieved, and the transmissibility index, which is the geomertrical mean of the normalized displacement in the range of whole barrier width in some place behind the barrier, were drawn. It concludes by analyzing these curves, that the farer from the barrier,the worse the isolation effect, and the barrier will behave as best isolation effect when the net distance between two adjacent piles is nearly equal to the radius of the piles.