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Abstract It?s important to implement advance geological forecast for Weak zone in a long diversion tunnel construction by GPR. This paper take gravel and clay mixed dielectric constant as the research object，and study on the relative dielectric constant of shale and water mixture and its trend. Then we deduce the experience formula and the relation curve moisture content of the mixed dielectric constants. Therefore we make FDTD(Finite Difference Time Domain) forward modeling by means of two kinds of spatial distribution of weak zone，and analyze the typical imaging regularity and characteristics. So as to we may achieve the purpose of the space position in the weak zone from the measured data. Analysis results as follows：The volume ratio on the mixing soil and gravel mixture component have great influence on the dielectric constant. Meanwhile the water content reflection characteristics of electromagnetic wave are obvious and easily reform to multiple waves. In consequence we can remove interferences through the measured and FDTD forward. And we fixed formation value of moisture content and establish the 3D slice result maps. Which provide method and guidance for similar geological forecast projects.
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2015, Vol. 34 
