地震散射技术在盾构隧道海底孤石探测中的应用———以横琴隧道为例

针对珠海横琴海底盾构隧道孤石探测这一工程勘察难点,选用具有高分辨特点的地震散射新技术,通过小排列密集采集方式,进行2 m×1 m 的网格观测,获得轴向间距1 m、横向2 m、垂向0. 5 m 的三维速度结构和地质界面分布。以波速大于2 400 m/ s 为识别基岩与孤石的指标,得到其高程分布;对三维波速结构进行水平、纵向和横向切片,展现基岩与孤石的分布图像。勘探发现 26 处孤石,其中9 处直径超过3 m。通过证实,物探与钻探的吻合率达到90%,平均深度误差在1 m 以内。实际应用结果表明地震散射技术具有采集灵活、分辨率高的特点,特别适合孤石勘探。

Application of Seismic Scattering Technique to Prospecting of Boulders in Submarine Tunnel: a Case Study of Hengqin Tunnel

Aiming at the difficulty of engineering survey of the boulder in the Hengqin Submarine Shield Tunnel in Zhuhai, seismic scattering technique is selected which has high resolution feature. Seismic scattering technique utilizes small-scale and dense data collection methods, of which data collection grid is up to 2 m×1 m. Three-dimensional velocity structure and geological interface distribution with axial spacing of 1 m, lateral 2 m, and vertical 0. 5 m are obtained. The elevation distribution of bedrock and boulders are distinguished whose velocity is greater than 2 400 m/ s. The horizontal, vertical and lateral slices of three-dimensional velocity structure illustrate the distribution of bedrock and boulder. Exploration revealed 26 boulder stones, 9 of which are more than 3 m in diameter. The results demonstrate that geophysical prospecting coincides to drilling exploration, and its average depth error is less than 1 m. The features of easy data collection and high resolution make seismic scattering profile technology suitable for boulder exploration.