平面P波在饱和半空间中洞室周围的散射(II):数值结果

本文通过数值计算研究了入射平面P波在饱和半空间中洞室周围散射问题,分析了入射波频率和角度、边界渗透条件、孔隙率、泊松比等参数对散射的影响。研究表明,平面P波入射情况下,饱和半空间和单相(干土)半空间中洞室附近地表位移幅值的差别很大,干土情况的水平位移幅值相对较大,饱和情况的竖向地表位移幅值相对较大;由于波在洞室附近的干涉,饱和情况与干土情况的地表位移出现相位漂移。随着孔隙率的增大,洞室附近水平地表位移幅值逐渐减小,竖向地表位移幅值则逐渐增大;当孔隙率较低时,边界渗透条件对地表位移幅值的影响很小,而当孔隙率较大时,边界渗透条件的影响则不可忽视,不透水情况下,水平和竖向地表位移幅值的峰值均相对较大;随着入射频率的增加,孔隙率的影响逐渐增大,而且不透水情况下孔隙率的影响相对较大。随着泊松比的增大,洞室附近水平地表位移幅值逐渐降低,竖向地表位移幅值则逐渐增大;泊松比较小时,边界渗透条件对位移幅值的影响较大,泊松比较大时,边界渗透条件对位移幅值的影响则较小;随着入射频率的增加,泊松比的影响逐渐增大。当孔隙率较小时,半空间地表和洞室表面孔隙水压幅值较小,但空间变化比较剧烈,随着孔隙率的增大,孔隙水压逐渐增大但空间变化逐渐平缓;随着入射频率的增加,孔隙水压幅值逐渐增大,且孔隙水压的空间变化逐渐变得复杂。

Scattering of plane P waves around a cavity in poroelastic half-space(II):numerical results

Scattering of plane P waves around a cavity in poroelastic half-space is studied by numerical results,and the effects of incident frequency and angle,drainage condition,porosity,Poisson's ratio,etc.on the wave scattering are discussed.It is shown that,for incident plane P waves the surface displacement amplitudes near the cavity in saturate and dry poroelastic half-space are found to be very different: the surface horizontal displacement amplitudes are larger for the dry poroelastic case,and the surface vertical displacement amplitudes are larger for the saturate cases;the phase shifts between the saturate and dry poroelastic cases due to the wave interference around the cavity can be observed.As the porosity increases,the surface horizontal displacement amplitudes decrease gradually,but the surface vertical displacement amplitudes increase gradually;for small porosity,the drainage condition has little influence on the surface displacement amplitudes,for large porosity,however,the effect of drainage condition becomes significant,and both the surface horizontal and vertical displacement amplitudes for the undrained case are relatively larger;as the incident frequency increases,the effect of porosity becomes significant,and the effect for the undrained case is more significant.As the Poisson's ratio increases,the surface horizontal displacement amplitudes decrease gradually,but the surface vertical displacement amplitudes increase gradually;for low Poisson's ratio,the drainage condition has significant influence on the surface displacement amplitudes,however,for high Poisson's ratio,the effect of drainage condition becomes insignificant;as the incident frequency increases,the effect of Poisson's ratio becomes important.When the porosity is small,the surface pore pressures near or around the cavity are small but their oscillations are violent,and as the porosity increases,the pore pressures increase significantly but their oscillations become smoother;as the incident frequency increases,the pore pressures become larger and their oscillations become more complicated.