中文摘要：

提出了聚焦电流法进行隧道超前预报。采用两种电极布置方式——只用屏蔽电极探测的An供电装置和在屏蔽电极中间再加一电极同时供电的An-A0供电装置。土槽模拟实验结果表明：当掌子面不断接近异常体时，观测电位逐渐下降，可利用下降点和拐点进行预报；注意区和警示区的形态如手电光，表示本方法具有聚焦探测效果。超前探测的距离与电极距和异常体大小有关，电极距越大，异常体越大，异常体越早被探测到；An-A0供电装置比An供电装置效果好。

英文摘要：

Focused current method is proposed for advanced forecast in tunnels by two DC electrode layout. A. installation is detected by the shield electrode and An -A0 installation added to another electrode in the middle of the shielded electrode. The clay test show that the observed potential drops down when tunnel face approaches to anomaly constantly. Meanwhile, forecasting can be carried out by the drop point and the transition point. The pat- terns of notice area and warning area as torchlight indicate the method with focused effect. Forecast distance is determined by radius of electrode and size of anomaly. The bigger the electrode and the anomaly are, the earlier the anomaly can be detected. The effect of An - A0 installation is better than An installation.