高阶模态面波在软弱薄层探测中的应用

Application of high model surface wave in low velocity thin layer

面波勘探在浅地层波速测试及速度分层工作中取得了较好的地质效果 .在一般情况下主要利用面波的基阶模态 .有低速薄层存在时 ,瑞利面波的能量不仅分配在基阶面波中 ,有些高阶模态的面波还具有较高的能量 ,高阶模态面波的高能量反映了低速层的存在 .在以高能量为标准的方法合成频散曲线时 ,各阶面波的综合作用使频散曲线上出现“之”字形特征 .根据这些特征可以确定软弱薄层的空间位置 .在实测资料解释中 ,注意利用高阶模态面波 ,取得了较好的地质效果 。

The energy of Rayleigh surface wave is often contained in various models . The strong energy in high models surface waves implies the existence of low velocity layers and that the velocity-frequency curve appears the shape of 'Z'. This is confirmed by both field survey and theoretical calculation. The position of low velocity layer can then be determined according to this feature. Good exploration results are achieved by the application of high model surface waves. It is proved by field cases that the surface waves method is reliable to detect the low velocity layers.