基于高密度地震技术的武汉某区溶洞探测研究

Karst cavities detection based on high density seismic technique in a certain area of WuHan

武汉市灰岩广泛发育,存在大量岩溶孔洞,地质风险程度高。为了探测某区50 m以浅的灰岩溶洞,避免高层建筑以及道路建设中的安全隐患,运用高密度地震勘探技术,使用便携电驱重锤震源、智能节点式地震仪,对区内道路及周边地下灰岩溶洞进行探测。获取的高分辨率三维地震数据有效频带为10~80 Hz,主频30 Hz。在三维地震数据体上识别出2个灰岩溶洞,埋深25~40 m,属半充填或未充填型溶洞。溶洞在高密度地震剖面上反射特征表现为反射同相轴中断,内部反射波杂乱,同相轴扭曲,反射能量弱于周边地层地震反射。后期对研究区南部溶洞进行了钻孔验证,证实了该溶洞的存在,溶洞顶面埋深40 m,内部充填软土及灰岩碎块。

Wuhan city is well known for widely distributed limestone.A large number of karst cavities with high geological risk develop there.In order to detect the karst cavities buried less than 50m and avoid the hidden danger to high buildings or roads,the high-density seismic exploration technology is used in this study.In this workflow,portable electric drive heavy hammer source and intelligent node seismograph are used to detect the underground karst cavities in the study area.High resolution 3D seismic data is obtained from this work with effective frequency band from 10 Hz to 80 Hz and the dominant frequency at 30 Hz.Two karst cavities with a buried depth from 25 m to 40 m are identified on the 3D seismic data volume,which are semi filled or unfilled.The seismic reflection characteristics of the karst cavities on the high-density seismic profile are as follows:the reflection event axis is interrupted;the internal reflection wave is disordered;the event axis is distorted;and the reflection energy is weaker than the seismic reflection of the surrounding strata.In the later stage,the karst cavity in the south of the study area is verified by drilling,which confirms the existence of the karst cavity.The top surface of the karst cavity is buried 40 m deep,and the interior is filled with soft soil and limestone fragments.