等值反磁通瞬变电磁法在城市轨道交通岩溶勘察中的应用

Application of opposing-coils transient electromagnetics in karst exploration of urban rail transit

岩溶是一种较为常见的不良地质现象,严重威胁城市轨道交通的建设及运营。城市轨道交通建设环境较为复杂,常用的岩溶物探手段易受场地空间限制、各种震动及强电磁干扰等因素的影响,探测效果不佳。为了更准确地探明地下岩溶的发育情况,以广东某轨道交通为例,将等值反磁通瞬变电磁法应用于城市轨道交通岩溶勘察中,在线路经过的灰岩区沿中线布置了1条物探测线。探测结果不仅揭示了地下的岩土分界面,还发现了多处低阻异常区,经与钻孔资料对比,证实低阻异常区由岩溶引起。实践表明该物探方法探测效果良好、成果可靠,适合于城市轨道交通岩溶勘察。

As a common adverse geological phenomenon,karst seriously threatens the construction and operation of urban rail transit.However,the construction environment of urban rail transit is relatively complex,and the commonly used karst detection methods are easy to be affected by the space limitation of the site,various vibrations and strong electromagnetic interference,and therefore cannot obtain accurate results.In order to more accurately explore the development of underground karst,taking a rail transit project in Guangdong Province as an example,this paper applied the opposing-coils transient electromagnetics(OCTEM)to the karst survey and arranged a geophysical detection line along the middle line in the limestone area through which the railway passed.The detection results not only revealed the interface of the underground rock and soil,but also found a number of low-resistance anomalies which were confirmed to be caused by karst by comparison with borehole data.The practice shows that the opposing-coils transient electromagnetic method is effective and reliable,which is suitable for karst exploration of urban rail transit.