微动技术在大连地铁岩溶勘察中的应用

The Application of Microtremor Technology to Karst Survey of the Dalian Subway

大连地铁5号线沿线区域岩溶发育,前期勘察阶段受勘察手段和钻孔间距限制,存在较多岩溶勘察空白区域,给地铁盾构施工带来极大的地质隐患和技术风险。因此采用微动新技术,查明复杂城市环境条件下地铁沿线隧道洞身影响范围内岩溶的分布及发育情况。在微动解译的岩溶异常靶区布置钻孔验证,同时采用高精度跨孔地震CT对岩溶规模进行扫描。对比分析表明,微动二维视S波速度剖面能够直观、准确地显示地下地质体高低速地球物理性质,对低速岩溶地质体的规模、形态刻画精度与钻探揭露、地震CT探测精度基本一致。由此可见,微动是一种抗干扰能力强、场地适用性广、成果解释可靠的新方法,尤其适用于复杂城市环境下地质勘察工作,具有经济、高效、无损、快速的特点,建议在城市轨道交通不良地质体勘察工程项目中推广应用。

The karst development in the area along Dalian subway line 5 is limited by survey means and borehole spacing in the early exploration stage. There are many blank areas of karst exploration, which brings great geological hidden dangers and technical risks to the shield construction of the subway. This paper adopts a new microtremor technology with strong anti-jamming ability and wide site adaptability to find out the distribution and development of karst in the influence area of tunnel body along subway line under complex urban environment. Drilling holes are arranged to verify the fretting interpretation of target area in the karst anomaly, and high-precision cross-hole seismic CT to scan the karst scale. The comparative analysis shows that the microtremor two-dimensional apparent S-wave velocity profile can visually and accurately display geophysical properties of underground geological bodies with the high and low velocity, and the accuracy of describing the scale and shape of karst geological bodies is basically consistent with that of drilling and seismic CT detection. It can be seen that microtremor is a new method with strong anti-interference ability, wide site applicability and reliable interpretation of results,especially suitable for geological survey in complex urban environment. It has the characteristics of economy, high efficiency, non-destruction and celerity. It is suggested that microtremor should be popularized and applied to the survey of unfavorable geological bodies in urban rail transit.