The ground-water zone is the most concerned issue in advance water exploring in tunnel construction. At present, the electromagnetic technique is commonly used in forecasting the water-bearing condition in surrounding rock; however this method is constrained by in-situ conditions such as the tunnel face, metal devices interference and 3D wave-field position. So the water-bearing forecast of the surrounding rock within 100 m ahead of the tunnel face is an extremely difficult problem at home and abroad. The complex-frequency conductance exploring technique( CFC) is developed on the basis of the analysis of conductivity and complex-frequency features of permittivity and the practical case of Neelum-Jhelum Water Diversion Project in Pakistan. The technique is based on the principle of reflection and coherence of electromagnetic wave. The frequency range was from 100 kHz to 10 MHz and the electric dipole emission and receiving in array and migration imaging were adopted, which over-came the in-situ condition limitation problem. The position of water-bearing body and water content were determined according to the 1/4 coherent wavelength and the coherent energy respectively. The application in Neelum-Jhelum water diversion project in Pakistan has proved the feasibility and effectiveness of the method.%围岩富水带是隧道超前预报最关注的问题,目前,多使用电磁方法来预报围岩的含水性,但受到场地条件限制,面临掌子面条件、金属机具干扰、三维波场定位等诸多困难,特别是掌子面前方100 m范围内围岩的含水性预报,在国内外都是一个新的高难课题. 在研究了岩体电导率与电容率复频特性的基础上,结合巴基斯坦NJ-TBM引水隧洞工程,开发了复频电导探水( CFC)技术. 该技术基于电磁波反射与相干原理,选用100 kHz~10 MHz频率范围,采用电偶极子发射与阵列接收方式和偏移成像技术,突破了隧道内场地条件的限制. 依据1/4相干波长确定含水体的位置,相干能量确定含水量的大小. 在巴基斯坦NJ-TBM隧洞超前探水的应用,证明了该方法的可行性与有效性.
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