基于高密度电法的重点预选场址区远场断裂探测应用

Detection application of far-field fault in key prescription area of nuclear waste disposal site based on high density electrical method

对于高放废物地质处置而言,其场区边界断裂首先成为放射性核素向生物圈运移的潜在通道,有效探明处置库周边断裂地质信息(断裂影响性、产状及核部宽度等)显得尤为重要,优先的研究手段应通过钻探获取断裂信息,但面对高放废物处置库这样的工程特点,钻探又不宜大面积布置。本文基于上述情况,特以新场地块重点预选区西边界断裂为研究对象,分别在平行与垂直于断裂方向上布设了物探线,尝试利用高效无损的高密度电法探测技术开展相关研究,后期运用成熟的AGI与Loke反演,得到二维视电阻率剖面图,两种反演方法的解译结果均能较好地反映断裂信息。沿断裂走向上,在视电阻率剖面1300m左右开始出现一个较宽低阻区,显示出较大范围岩体破碎区,与地表露头踏勘对应,这就为研究区可能曾受北边逆断裂压性作用影响提供了物探证明;同时在垂直于断裂方向上,视电阻率剖面显示该断裂视倾角约70°,断裂核部宽约3~5m,其结果被三维精细化探槽所印证。实践证明,高密度电法能为处置库设计提供必要的基础数据,具有广阔的应用价值。

For the geological disposal of high level radioactive waste, the field boundary fault is the potential channel for the migration of radio nuclides to the biosphere. Therefore, finding out the geological information of the surrounding fault （fracture influencing degree, occurrence, width, etc. ） effectively is particularly important. The priority means of research is drilling, but drilling could not be assigned widely in the area duo to the engineering features of nuclear waste disposal. Based on the above-mentioned conditions, the west boundary fault in the key pre-selected area of Xinchang block is studied. The high- density electrical detection technology is employed to detect fault, and the geophysical lines are set up in parallel and perpendicular to the fault direction. In the later stage, the two-dimensional apparent resistivity profile is obtained using the mature AGI and Loke, and the fault information is reflected well by the two interpretations. Along the fault, there is a wide low resistance zone starting at about 1300m in the apparent resistivity profile, showing a larger range of rock fracture area, and consistent with outcrop survey results, which provides a geophysical proof for the study area affected by the north thrust fault extrusion. In perpendicular to the fault direction, the apparent resistivity profile shows that the viewing angle of the fault is about 70°and the width of the fault Core zone is about 3 - 5m, and the result is almost the same to three- dimension fine trenching. The high-density electrical method could provide necessary basic data for the repository design and has a wide range of application.