饱和土中流体对压缩波传播特性影响

Effect of the fluid on propagation characteristics of compressible waves in saturated soils

为了进一步分析流体性质对饱和土中压缩波传播的影响,基于Biot两相介质波动理论,推导了压缩波平面波动解,并得到了孔隙流体自由流动和流体无渗流时的压缩波速度公式.通过数值算例分析了水饱和、准饱和及气饱和三种饱和情况下土中压缩波的传播及衰减特性.结果表明,在水饱和至准饱和土中,两种压缩波的速度和弥散性均随含气量的增加而降低,衰减则随含气量的增加而增加.气饱和土中,P1波速度比水饱和时显著降低且基本无弥散和衰减;P2波速度比水饱和时有很大提高,同时弥散和衰减加强,且特征频率向高频漂移.完全水饱和时P1波主要在流体中传播,含气量超过一定值(1%)时主要受土骨架中控制,P2波则刚好与此相反.

To analyze the effect of fluids on compressible waves propagation in saturated soils, based on Biot＇ s theory of wave propagation in two-phase media, the plane wave solutions of compressible waves were derived and the velocity formulations for free flow and no flow were obtained. The characteristics of propagation and attenuation of compressible waves in water-saturated, pseudo water-saturated and air-saturated soils were discussed by using numerical methods. Numerical results show that there are great differences between air-and water-filled soils. The velocity and dispersion of the compressible waves decrease considerably with the decreasing saturation, and the attenuation of compressible wave increases with the decreasing saturation in water-saturated and pseudo water-saturated soils. The P1 wave velocity, dispersion and attenuation are much lower in air-filled soils than those in water-saturated soils. The P2 wave velocity, dispersion and attenuation are higner in air-saturated soils than those in water-saturated soils, and the eigenfrequency shifts to a much higher frequency in air-saturated soils. The P1 wave mainly depends on fluid in completely water-saturated soils and is effected by soil skeleton with increasing air content. However the P2 wave is on the contrary.