浅海沉积层中界面波的传播以及掩埋目标的回波

A study on the propagation of interface wave in shallow sea sediments and the echo wave for buried objects

根据地声界面波的相关理论,采用时域有限差分法建立浅海沉积层中界面波传播模型。以沉积层中掩埋小目标为例,计算界面波对空腔掩埋物和实心掩埋物的不同作用结果。根据运动方程和应力应变关系采用中心差分网格建立声场的有限差分模型,计算了声场瞬态情况和质点振动的时间序列结果,从不同角度比较分析了地声界面波对掩埋目标的作用。根据浅海沉积层的性质计算了界面波的传播损失和对掩埋物体的目标强度,由于界面波传播衰减主要由沉积层的能量耗散引起,其规律接近横波的传播衰减,在高频情况下界面波在沉积层中传播的距离不远。文章试图建立一种对浅海沉积层中掩埋小尺度目标的探测新方法。通过一些典型模型的分析,从理论角度证明地声界面波对目标探测的可行性。

In the framework of Geoacoustics interface wave theory, a time domain fmite difference model for the propagation of interface wave in shallow sea has been developed. A numerical model is used to study the interactions of interface wave with different buried objects. There are different resnits for ob- jects with and without air-filled chamber. The equation of motion and the stress-strain relation, together with a constitutive relation, form a set of partial differential equations. Introducing finite differences, this set of equations can be discretized and adapted to the finite-difference time-domain scheme. According to the characteristics of sediments in shallow sea, transmission loss of interface wave and target strength of buried object have been calcniated. Energy loss in sediment causes attenuation of interface waves so that the propagation range is limited in high frequency. This is similar to shear waves. In this paper, a computational method is presented with some typical examples to assess feasibility of using interface wave to detect objects.