地质雷达在岩溶隧道超前预报中的应用

Application of geological radar to geological forecast in karst tunnel

地质雷达是一种广泛用于地质探测的高频电磁脉冲波技术.针对湖北大广南高速公路建设中紫荆山岩溶隧道实际工程,为了探明隧道周边岩溶等不良地质体,采用地质雷达中连续测量方法进行信号采集,并通过增益调节、滤波处理等方法对采集信号进行处理.通过结合裂隙、溶洞、富水岩体三个典型实例,分析并总结了它们的地质雷达反射波的具体特征,分别表现为节理裂隙反射波同相轴杂乱、岩溶裂隙反射波的带状分布、溶洞反射波的"双曲线反射"、富水岩体反射波的主频显著降低和能量迅速衰减等.这些特征有助于断定出不良地质体的具体位置和规模,从而为保障隧道的安全施工提供了一定依据.

Geological radar is one kind of the electromagnetic wave technologies with high frequency, which is widely used in geological exploration. According to the Zijingshan karst tunnel engineering during the Daguangnan Highway construction in Hubei, a continuous mode was adopted to collect signals by geological radar in order to detect an adverse geological body. Signals collected were processed by gain control and filtering processing. Combining with the typical examples of fissure, karst cave and water-beating rock mass, the specific characteristics of their radar reflection were analyzed, such as unorganized events in reflection of joint fissure, zonal distribution in reflection of karst fissure, hyperbola in reflection of karst caves, the decrease of frequency and energy in reflection of water-bearing rock mass. These characters are helpful for estimating the concrete position and scale of an adverse geological body and can provide a basis to protect the safety of tunnel construction.